Isolation of Staphylococcus aureus and antibiotic-resistant Staphylococcus aureus from residential indoor bioaerosols.OBJECTIVE: In this study we evaluated the levels of Staphylococcus aureus Staphylococcus au·re·us
A bacterium that causes furunculosis, pyemia, osteomyelitis, suppuration of wounds, and food poisoning.
Staphylococcus aureus Staphylococcus pyogenes and antibiotic-resistant S. aureus The aureus (pl. aurei) was a gold coin of ancient Rome valued at 25 silver denarii. The aureus was regularly issued from the 1st century BC to the beginning of the 4th century AD, when it was replaced by the solidus. in colony-forming units (CFU CFU
see colony-forming units. ) per cubic meter Noun 1. cubic meter - a metric unit of volume or capacity equal to 1000 liters
cubic metre, kiloliter, kilolitre
metric capacity unit - a capacity unit defined in metric terms of air.
DESIGN: We used Andersen two-stage samplers to collect bioaerosol samples from 24 houses in El Paso El Paso (ĕl pă`sō), city (1990 pop. 515,342), seat of El Paso co., extreme W Tex., on the Rio Grande opposite Juárez, Mex.; inc. 1873. , Texas, using tryptic tryp·tic
Relating to or resulting from trypsin.
relating to or resulting from digestion by trypsin. soy agar as the collection media, followed by the replicate plate method on Chapman Stone selective medium to isolate S. aureus. The Kirby-Bauer disk diffusion method was used to determine antibiotic resistance antibiotic resistance,
n the ability of certain strains of microorganisms to develop resistance to antibiotics.
antibiotic resistance to ampicillin ampicillin (ăm'pĭsĭl`ĭn), a penicillin-type antibiotic that is effective against both gram-negative microorganisms and gram-positive microorganisms such as Escherichia coli. , penicillin, and cefaclor cefaclor /cef·a·clor/ (sef´ah-klor) a semisynthetic, second-generation cephalosporin effective against a wide range of gram-positive and gram-negative bacteria.
n. , which represent two distinct classes of antibiotics.
RESULTS: The average recovered concentration of respirable respirable /res·pir·a·ble/ (re-spir´ah-b'l)
1. suitable for respiration.
2. small enough to be inhaled.
1. Fit for breathing, as air. heterotrophic heterotrophic /het·ero·tro·phic/ (-tro´fik) not self-sustaining; said of microorganisms requiring a reduced form of carbon for energy and synthesis. organisms found outside each home was 345.38 CFU/[m.sup.3], with an average of 12.63 CFU/[m.sup.3] for S. aureus. The average recovered concentration of respirable heterotrophic organisms found inside each home was 460.23 CFU/[m.sup.3], with an average of 15.39 CFU/[m.sup.3] for S. aureus. The respirable S. aureus recovered from inside each home had an average resistance of 54.59% to ampicillin and 60.46%. to penicillin. Presence of cefaclor-resistant and of multidrug-resistant S. aureus was the same, averaging 13.20% per house. The respirable S. aureus recovered from outside each home had an average resistance of 34.42% to ampicillin and 41.81% to penicillin. Presence of cefaclor-resistant and of multidrug-resistant S. aureus was the same, averaging 13.96% per house.
CONCLUSIONS: This study indicates that antibiotic-resistant bioaerosols are commonly found within residential homes. Our results also suggest that resistant strains of airborne culturable S. aureus are present in higher concentrations inside the study homes than outside the homes.
KEY WORDS: antibiotic resistant, bioaerosols, residential indoor air, Staphylococcus aureus. Environ Health Perspect 114:1859-1864 (2006). doi:10.1289/ehp.9585 available via http://dx.doi.org/ [Online 7 September 2006]
The introduction of antimicrobial agents Antimicrobial agents
Chemical compounds biosynthetically or synthetically produced which either destroy or usefully suppress the growth or metabolism of a variety of microscopic or submicroscopic forms of life. to treat human disease was one of the most significant public health accomplishments of the 20th century. Although many factors (e.g., improvements in sanitation, nutrition, and standard of living) worked in concert with antibiotic therapy to control and limit infectious disease Infectious disease
A pathological condition spread among biological species. Infectious diseases, although varied in their effects, are always associated with viruses, bacteria, fungi, protozoa, multicellular parasites and aberrant proteins known as prions. transmission, antibiotic therapy was unique in that it not only allowed for the prevention but also for the curing and control of certain diseases (Barker 1999; Cohen cohen
(Hebrew: “priest”) Jewish priest descended from Zadok (a descendant of Aaron), priest at the First Temple of Jerusalem. The biblical priesthood was hereditary and male. 1992). Although the introduction and successful development of this therapeutic class of agents represents a significant medical achievement, this success has also led to complacency within both greater society and the scientific community with regard to the development of bacterial resistance (Neu 1992). That microorganisms possess the ability to develop resistance to antibiotics was recognized soon after the introduction of antimicrobial therapy, when resistant bacteria were initially identified in the 1930s (Smith and Coast 2002; Virk and Steckelberg 2000). Reoccurring episodes of infection with multiple resistant organisms have affected hospitals since the early 1950s when penicillin-resistant staphylococci staph·y·lo·coc·cus
n. pl. staph·y·lo·coc·ci
A spherical gram-positive parasitic bacterium of the genus Staphylococcus, usually occurring in grapelike clusters and causing boils, septicemia, and other infections. initially emerged (Cohen 1992). In spite of the increased understanding of the factors contributing to the development of resistance over the last 60 years, the Years, The
the seven decades of Eleanor Pargiter’s life. [Br. Lit.: Benét, 1109]
See : Time extent of this problem has not decreased with time and is currently among the strongest global threats to the treatment of infectious disease (Conly 2002). The degree to which this problem has progressed is demonstrated by the fact that resistance has developed against all available classes of antibiotics (Rao 1998; Virk and Steckelberg 2000).
As a result of the significant difficulties associated with the accurate measurement of airborne bacteria, little data exist on the concentration of bacteria in indoor air in comparison to other airborne contaminants airborne contaminants,
n.pl materials in the atmosphere that can affect the health of persons in the same or a nearby environment. Also referred to as
air pollution. [Institute of Medicine Committee on Damp Indoor Spaces and Health (IOM IOM
See: Index and Option Market ) 2004]. Although there are significant difficulties in measuring airborne concentrations of most bioaerosols, the health effects associated with exposure to aerosolized Adj. 1. aerosolized - in the form of ultramicroscopic solid or liquid particles dispersed or suspended in air or gas
gaseous - existing as or having characteristics of a gas; "steam is water is the gaseous state" bacteria have received less research attention than those associated with exposure to other organic dusts, such as molds and animal allergens. Also, many bacteria have traditionally been thought of as infectious organisms, with disease resulting only from transmission via large droplets over short distances or through contact with contaminated contaminated,
v 1. made radioactive by the addition of small quantities of radioactive material.
2. made contaminated by adding infective or radiographic materials.
3. an infective surface or object. surfaces (Roy and Milton 2004). Roy and Milton (2004) suggested that this paradigm be questioned and that there is a need for improved understanding of aerosol-acquired disease. This need is made more urgent by the increasing environmental burden of antibiotic-resistant bacteria.
Multidrug-resistant Staphylococcus aureus is an example of a bacterium for which the role of exposure to aerosolized organisms in disease transmission should be more closely evaluated. An international survey of infections due to Staphylococcus staphylococcus (stăf'ələkŏk`əs), any of the pathogenic bacteria, parasitic to humans, that belong to the genus Staphylococcus. The spherical bacterial cells (cocci) typically occur in irregular clusters [Gr. species resulted in the finding that S. aureus was the most prevalent cause of hospital- and community-acquired bloodstream, skin and soft tissue, and lower respiratory infection Noun 1. lower respiratory infection - infection of the lower respiratory tract
respiratory infection, respiratory tract infection - any infection of the respiratory tract (Diekema et al. 2001). In the hospital setting, the most common mode of transmission of resistant S. aureus is close contact with infected persons or with health-care workers with contaminated hands or clothing (Cooper et al. 2004). Recent evidence suggests, however, that airborne dispersal and transmission may also be important (Beggs 2003; Cooper et al. 2004; Roberts et al. 2006), and case studies implicating im·pli·cate
tr.v. im·pli·cat·ed, im·pli·cat·ing, im·pli·cates
1. To involve or connect intimately or incriminatingly: evidence that implicates others in the plot.
2. airborne transmission airborne transmission Epidemiology The transmission of pathogens by aerosol, which enter the body by the respiratory tract. See Aerosol. in the hospital setting have been published in the literature (Cotterill et al. 1996; Wagenvoort et al. 1993). Although drug-resistant S. aureus has historically been a significant problem only in hospitals, the urgent need for further study of the ambient airborne concentrations and the role of airborne transmission of this organism in non-hospital environments is demonstrated by the increasing prevalence of methicillin-resistant S. aureus (MRSA MRSA Methicillin-resistant Staphylococcus aureus. See MARSA. ) infections in the community (Chambers 2001). Most alarming about this trend is that infection has been observed among individuals with and without known risk factors (Gorak et al. 1999).
The primary objective of this study was to determine the levels of respirable S. aureus, including antibiotic-resistant and multidrug-resistant S. aureus (those resistant to at least two classes of antibiotics) found within the bioaerosols of residential homes. We hypothesized that S. aureus, including antibiotic-resistant and multidrug-resistant S. aureus, were present in the bioaerosols of the average home.
Sample collection. Indoor and outdoor culture-able bacterial bioaerosol samples were collected in El Paso, Texas, from 24 one-story houses that had no basement or attic. These 24 houses were randomly selected from a separate larger study of 50 houses that had been identified when a solicitation for study participation was sent to faculty, staff, and students at the University of Texas School of Public Health The Texas Legislature authorized the creation of a school of public health in 1947, but did not appropriate funds for the school until 1967. The first class was admitted in the Fall of 1969, doubled in the second year and doubled again in the third year, with continued grwoth over the , El Paso Regional Campus, and the University of Texas at El Paso The University of Texas at El Paso, popularly known as UTEP, is a public, coeducational university, and it is a member of the University of Texas System. The school is located on the northern bank of the Rio Grande, in El Paso, Texas, and is the largest university in the (Mota LC, Gibbs SG, Green CF, Payan F, Tarwater PM, Ortiz M, unpublished data). These houses contained no visible microbial microbial
pertaining to or emanating from a microbe.
the breakdown of organic material, especially feedstuffs, by microbial organisms. issues; no adverse health issues that could be related to microbial contamination of the home had been previously reported by the occupants. Protocols were in accordance with Human Subject and Health Insurance Portability and Accountability Act The Health Insurance Portability and Accountability Act (HIPAA) was enacted by the U.S. Congress in 1996.
According to the Centers for Medicare and Medicaid Services (CMS) website, Title I of HIPAA protects health insurance coverage for workers and their families when approval through the University of Texas School of Public Health. Samples were taken during spring (March, April, and May) of 2006, with sampling conducted at different times of day to accommodate the needs of the home owners.
We used methods adapted from previous work (Gibbs et al. 2004, 2006; Green et al. 2003; Mota LC, Gibbs SG, Green CF, Payan F, Tarwater PM, Ortiz M, unpublished data). Duplicate bioaerosol samples were collected inside each house using Andersen two-stage viable microbial particle sizing sampler instruments (Tisch Environmental, Cleves, OH) (Andersen Samplers Inc. 1976.) The Andersen two-stage sampler is a cascade impactor with 200 orifices for each of the two stages; the sampler separates particles according to according to
1. As stated or indicated by; on the authority of: according to historians.
2. In keeping with: according to instructions.
3. their size onto one of two stages. The nonrespirable stage collects particles > 8 [micro]m onto a media-filled petri dish pe·tri dish
A shallow circular dish with a loose-fitting cover, used to culture bacteria or other microorganisms.
a shallow, circular, glass or disposable plastic dish used to grow bacteria on solid media such as agar. , and the respirable stage collects particles of 0.8-8 [micro]m onto a second media-filled petri dish. Separate equipment, including a pump (Gast Oil-less Pressure/Vacuum Pump, Gast Manufacturing, Inc., Benton Harbor Benton Harbor, city (1990 pop. 12,818), Berrien co., SW Mich., on Lake Michigan at the mouth of the St. Joseph River opposite St. Joseph; inc. 1869. A long-time fruit industry, tourist, and industrial center, noted for appliance manufacturing, the city declined in , MI) and Andersen two-stage sampler were used to duplicate each site. All pumps were calibrated cal·i·brate
tr.v. cal·i·brat·ed, cal·i·brat·ing, cal·i·brates
1. To check, adjust, or determine by comparison with a standard (the graduations of a quantitative measuring instrument): to 28.3 L/min using the TriCal Laboratory/Field Audit Calibrator calibrator
an instrument for dilating a tubular structure or for determining the caliber of such a structure. (BGI BGI Barclays Global Investors
BGI Bainbridge Graduate Institute
BGI Bureau Gravimétrique International
BGI Borland Graphic Interface (File Name Extension)
BGI Bridgetown, Barbados - Grantley Adams International Incorporated, Waltham, MA) before each sampling event (Dacarro et al. 2003). The samplers were placed on a tripod 1 m above the floor surface in the center of the main living area to simulate the human breathing zone (Hyvarinen et al. 2001; Pastuska et al. 2000; Sterling and Lewis 1998).
The Andersen two-stage samplers were loaded with plates of tryptic soy agar (TSA TSA
See tax-sheltered annuity (TSA). ; Difco Laboratories, Detroit, MI), an excellent general agar used to culture a variety of bacterial microorganisms. Duplicate 10- and 15-min air samples were taken at each home. Various climatic conditions were measured, including temperature, relative humidity relative humidity
The ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage. , and barometric pressure, using a portable weather station (Traceable Digital Barometer Module; Calibration Control Company, Friendswood, TX). All equipment and materials were handled using aseptic aseptic /asep·tic/ (-tik) free from infection or septic material.
Of, relating to, or characterized by asepsis. technique to ensure that the bioaerosol samples were not contaminated. All samples were returned to the laboratory for analysis within 2 hr of sample collection.
At the laboratory, the plates were placed in an inverted inverted
reverse in position, direction or order.
inverted L block
a pattern of local filtration anesthesia commonly used in laparotomy in the ox. position in an incubator at 35[degrees]C. The colonies were counted after 24 and 48 hr to determine if the plates were overgrown overgrown
said of a part that has not been kept trimmed.
overgrown hooves put unusual stresses on bones and tendons and allow for distortion of the wall and sole. . After 48 hr of incubation, the plates were inverted and refrigerated re·frig·er·ate
tr.v. re·frig·er·at·ed, re·frig·er·at·ing, re·frig·er·ates
1. To cool or chill (a substance).
2. To preserve (food) by chilling. at 4[degrees]C until use for the replica plate method (Lederberg and Lederberg 1952). We counted colonies for each plate and calculated the total number of culturable colony forming units (CFUs) per cubic meter (Green et al. 2003; Meklin et al. 2002). Only the TSA plates from the respirable portion were evaluated using the replica plate method and Kirby-Bauer procedures; therefore, the data presented in the present study deal only with the culturable respirable portion of bioaerosols.
Isolation and speciation speciation
Formation of new and distinct species, whereby a single evolutionary line splits into two or more genetically independent ones. One of the fundamental processes of evolution, speciation may occur in many ways. . We used the replica plate method to identify the recovered aerosolized culturable bacteria by transferring the bacterial colonies onto a selective medium (Lederberg and Lederberg 1952). For this method we used Chapman Stone medium (CSM CSM - ["CSM - A Distributed Programming Language", S. Zhongxiu et al, IEEE Trans Soft Eng SE-13(4):497-500 (Apr 1987)]. ; Difco Laboratories) for identification of S. aureus. After pressing of the CSM, TSA was used as a final control for the method, being pressed first and last to ensure that the organisms were completely transferred to all plates. All plates were incubated at 35[degrees]C and counted at 24 and 48 hr. The presence of S. aureus was further confirmed using Bacto coagulase coagulase /co·ag·u·lase/ (-las) an antigenic substance of bacterial origin, produced by staphylococci, which may be causally related to thrombus formation.
n. plasma (Fisher Scientific Fisher Scientific, formally Fisher Scientific International, Inc. and colloquially Fisher was a biotechnology company that provided products and services to the global scientific research and United States clinical laboratory markets. , Houston, TX). Once counted, the plates were refrigerated in an inverted position at 4[degrees]C until used for the Kirby-Bauer disk diffusion method.
Antimicrobial susceptibility testing. We analyzed the antibiotic-resistant characteristics of up to five S. aureus isolates collected from the respirable plate of each sample using the Kirby-Bauer disk diffusion method (Bauer et al. 1966). Only organisms that could be isolated from the CSM and cultured using a slant tube were evaluated for antibiotic resistance. The method was conducted in duplicate for each organism evaluated. If the duplicate analysis did not result in the same resistance profile, the organism was not included in the analysis. A sterile loop was used to transfer the microorganism microorganism /mi·cro·or·gan·ism/ (-or´gah-nizm) a microscopic organism; those of medical interest include bacteria, fungi, and protozoa. being tested to a tube of phosphate-buffer water until the tube was the same turbidity turbidity /tur·bid·i·ty/ (ter-bid´i-te) cloudiness; disturbance of solids (sediment) in a solution, so that it is not clear.tur´bid
The cloudiness or lack of transparency of a solution. as the 0.5 McFarland standard, which resulted in an estimated [10.sup.8] CFUs/mL. Room temperature Mueller-Hinton agar (MHA MHA
microangiopathic hemolytic anemia. ; Difco Laboratories) plates were used to evaluate each of the microorganisms for antibiotic resistance. Once the organism was placed onto the MHA, it was allowed to dry before the disks containing the antibiotics were placed onto the MHA surface using a Sensi-Disk 6-Place Self- Tamping tamp
tr.v. tamped, tamp·ing, tamps
1. To pack down tightly by a succession of blows or taps.
2. To pack clay, sand, or dirt into (a drill hole) above an explosive. Dispenser (Baltimore Biological Laboratory, Cockeysville, Maryland). The disks were allowed to settle before being inverted and placed in an incubator at 35[degrees]C. The plates were checked for susceptibility after 48 hr. The zones of inhibition were recorded for all of the plates, and a determination was made as to whether the microorganism was susceptible, intermediately resistant, or resistant to each antibiotic evaluated using National Committee for Clinical Laboratory Standards (NCCLS NCCLS National Committee for Clinical Laboratory Standards 1997, 2000, 2001). Table 1 provides the specific NCCLS zone diameters used to categorize S. aureus. An organism was not included in the tabulation tab·u·late
tr.v. tab·u·lat·ed, tab·u·lat·ing, tab·u·lates
1. To arrange in tabular form; condense and list.
2. To cut or form with a plane surface.
Having a plane surface. of results if the antibiotic disk had dislodged from the media or if the duplicates did not result in the same antibiotic-resistance profile.
We used three types of Antibiotic Susceptibility Test Disks (Difco Laboratories) for the Kirby-Bauer method Kirby-Bauer method
a method for testing the antimicrobial susceptibility of bacteria based on the size of zones of inhibition of growth of a lawn culture around disks impregnated with the antimicrobial drug. . These three antibiotics (10 [micro]g ampicillin, 10 [micro]g penicillin, and 30 [micro]g cefaclor), chosen because they are commonly used in human medicine, represent two distinct classes of antibiotics. Ampicillin and penicillin are both penicillins, and cefaclor is a second generation cephalosporin cephalosporin (sĕf'əlōspôr`ĭn), any of a group of more than 20 antibiotics derived from species of fungi of the genus Cephalosporium and closely related chemically to penicillin. Cephalosporins, e.g. . Multidrug resistance multidrug resistance,
n the adaptation of tumor cells or infectious agents to resist chemotherapeutic agents. is defined as resistance to at least two different classes of antibiotics; therefore, any organism in this study that was resistant to cefaclor and either ampicillin or penicillin was deemed multidrug resistant.
Quality assurance and quality control was maintained throughout the study using aseptic techniques. All sampling material that could be autoclaved was autoclaved for 15 min at 15 psi and 121[degrees]C. The Andersen two-stage samplers were sterilized ster·il·ize
tr.v. ster·il·ized, ster·il·iz·ing, ster·il·iz·es
1. To make free from live bacteria or other microorganisms.
2. after each use, washed, and then sterilized again before their next use. All other items were disinfected Disinfected
Decreased the number of microorganisms on or in an object.
Mentioned in: Isolation with a 70% ethanol solution after each sampling trip and before the next sampling trip. For negative controls, we used empty plates of TSA that were taken to the sampling site during collection. S. aureus (ATCC ATCC American Type Culture Collection, see there 25923; American Type Culture Collection American Type Culture Collection (ATCC) is a private, not-for-profit biological resource center whose mission focuses on the acquisition, authentication, production, preservation, development and distribution of standard reference microorganisms, cell lines and other materials for , Manassas, VA) was used as positive control. We applied S. aureus (ATCC 25923) to the CSM to ensure that it would be able to culture the selected organism. We also tested the control organisms in the Kirby-Bauer method to ensure that antibiotics used would inhibit growth of a nonresistant non·re·sis·tant
1. Not resistant, especially to a disease or environmental factor, such as heat or moisture.
2. Submissively obedient. culture.
Climatic conditions measured both inside and outside each home during the course of the study showed an expected variation for a study conducted during the spring season (Table 2).
The average recovered concentration of respirable heterotrophic organisms found within each home was 460.23 CFU/[m.sup.3] (Table 3). A quartile Quartile
A statistical term describing a division of observations into four defined intervals based upon the values of the data and how they compare to the entire set of observations.
Each quartile contains 25% of the total observations. (Q) representation shows the distribution of respirable heterotrophic organisms from inside the homes as follows: [Q.sub.0] = 154.59, [Q.sub.1] = 269.29, [Q.sub.2] = 415.49, [Q.sub.3] = 657.69, and [Q.sub.4] = 883.39 CFU/[m.sup.3]. The average recovered concentration of S. aureus found within each home was 15.39 CFU/[m.sup.3] (Table 3). A quartile representation shows the distribution of respirable S. aureus from inside the homes at [Q.sub.0] = 0.59, [Q.sub.1] = 4.20, [Q.sub.2] = 10.31, [Q.sub.3] = 20.32, and [Q.sub.4] = 53.30 CFU/[m.sup.3]. This results in an average respirable percentage of recovered culturable S. aureus to heterotrophic organisms of 3.94% ([Q.sub.0] = 0.27%, [Q.sub.1] = 1.11%, [Q.sub.2] = 2.37%, [Q.sub.3] = 5.01%, and [Q.sub.4] = 20.10%).
The average recovered concentration of respirable heterotrophic organisms found outside each home was 345.38 CFU/[m.sup.3] (Table 4). The distribution of respirable heterotrophic organisms from outside the homes by quartile were [Q.sub.0] = 44.17, [Q.sub.1] = 153.56, [Q.sub.2] = 286.51, [Q.sub.3] = 441.70, and [Q.sub.4] = 883.39 CFU/[m.sup.3]. The average recovered concentration of S. aureus found outside each home was 12.63 CFU/[m.sup.3] (Table 4). A quartile representation shows the distribution of respirable S. aureus from outside the homes at [Q.sub.0] = 0.00, [Q.sub.1] = 3.61, [Q.sub.2] = 6.77, [Q.sub.3] = 11.34, and [Q.sub.4] = 74.79 CFU/[m.sup.3]. This results in an average respirable percentage of recovered culturable S. aureus to heterotrophic organisms of 5.08% ([Q.sub.0] = 0.00%, [Q.sub.1] = 1.23%, [Q.sub.2] = 2.44%, [Q.sub.3] = 5.42%, and [Q.sub.4] = 37.33%); indicating that, on average, S. aureus represents 5.08% of the recovered culturable out-door bioaerosol.
The respirable S. aureus recovered from inside each home had an average resistance to ampicillin of 54.59% ([Q.sub.0] = 0.00%, [Q.sub.1] = 34.31%, [Q.sub.2] = 61.54%, [Q.sub.3] = 67.95%, and [Q.sub.4] = 100.00%) (Table 5). The average resistance to penicillin was 60.46% for each home ([Q.sub.0] = 0.00%, [Q.sub.1] = 45.00%, [Q.sub.2] = 62.50%, [Q.sub.3] = 75.00%, and [Q.sub.4] = 100.00%). Presence of cefaclor-resistant and of multidrug-resistant S. aureus was the same, averaging 13.20% per house ([Q.sub.0] = 0.00%, [Q.sub.1] = 12.50%, [Q.sub.2] = 23.61%, [Q.sub.3] = 60.00%, and [Q.sub.4] = 60.00%).
The average resistance to ampicillin of respirable S. aureus recovered from outside each home was 34.42% ([Q.sub.0] = 0.00%, [Q.sub.1] = 0.00%, [Q.sub.2] = 33.33%, [Q.sub.3] = 50.00%, and [Q.sub.4] = 100.00%) (Table 6). The average resistance to penicillin was 41.81% for each home ([Q.sub.0] = 0.00%, [Q.sub.1] = 0.00%, [Q.sub.2] = 40.20%, [Q.sub.3] = 72.50%, and [Q.sub.4] = 100.00%). Presence of cefaclor-resistant and of multidrug-resistant S. aureus was the same, averaging 13.96% per house ([Q.sub.0] = 0.00%, [Q.sub.1] = 0.00%, [Q.sub.2] = 0.00%, [Q.sub.3] = 20.83%, and [Q.sub.4] = 100.00%).
Using a paired t-test, we found that resistant strains of airborne culturable S. aureus were significantly higher inside the study homes than outside the homes. However, we found no significant difference between the concentrations of S. aureus inside versus outside the homes.
The present study was conducted over a 3-month period during spring 2006 to test the hypothesis that S. aureus, including antibiotic-resistant and multidrug-resistant S. aureus, are present in the bioaerosol of the average home. Study findings not only support our hypothesis but also suggest that resistant strains of airborne culturable S. aureus are present in higher concentrations inside the study homes than outside of the homes (Tables 5 and 6). This data trend suggests the presence of an indoor source of these organisms. Although this trend may be, in part, the result of the significantly higher concentrations of total heterotrophic organisms recovered inside compared to outside the homes, the lack of significant differences in both concentrations of recovered S. aureus and the percentages of S. aureus within all heterotrophic organisms recovered suggests that greater numbers of culturable antibiotic-resistant S. aureus strains per unit volume of air are present inside the homes. Additionally, based on evidence suggesting that human activities involving the movement of dry fabrics, such as bed making and curtain movement, are associated with elevated concentrations of airborne bacteria (Das et al. 2002; Roberts et al. 2006), it is reasonable to assume that elevated concentrations of S. aureus may exist indoors compared to outdoors. The health risks associated with occupant exposure to the concentrations we observed are difficult to calculate because of the few studies that have reported bacterial aerosol concentrations in indoor air (IOM 2004) and the resultant lack of epidemiologic data available for typical indoor environments. Although airborne bacteria have been associated with infectious and allergic respiratory disease Noun 1. respiratory disease - a disease affecting the respiratory system
respiratory disorder, respiratory illness
adult respiratory distress syndrome, ARDS, wet lung, white lung - acute lung injury characterized by coughing and rales; inflammation of the (Heidelberg et al. 1997), research involving bioaerosol assessment of culturable organisms in the residential environment has largely focused on fungi and the allergenic Allergenic
A substance capable of causing an allergic reaction.
Mentioned in: Echinococcosis and asthmatic health effects associated with exposure to these organisms. The results of the present study, in combination with the recently observed trends in the epidemiology of S. aureus (Chambers 2001) provide sufficient justification for further scientific evaluation of both the indoor sources of, and health effects associated with, indoor residential exposure to airborne S. aureus.
The epidemiology of S. aureus has changed in that there has been a continual increase in the prevalence of infections caused by antibiotic-resistant strains of the microbe microbe /mi·crobe/ (mi´krob) a microorganism, especially a pathogenic one such as a bacterium, protozoan, or fungus.micro´bialmicro´bic
n. (Garcia-Lara et al. 2005; Maranan et al. 1997). In addition to this increase in prevalence, resistant S. aureus has progressed from being an organism primarily associated with nosocomial infection Nosocomial infection
An infection that can be acquired in a hospital. ABPA is a nosocomial infection.
Mentioned in: Allergic Bronchopulmonary Aspergillosis, Hospital-Acquired Infections, Pseudomonas Infections
to one that has begun to regularly infect individuals outside of the hospital setting (Chambers 2001; Garcia-Lara et al. 2005; Groom et al. 2001; Herold et al. 1998; Manranan et al. 1997; Salgado et al. 2003). The lack of published data documenting patterns in bacterial aerosol concentrations in residential environments over time precludes our ability to determine whether there has been an increase in airborne concentrations of resistant S. aureus that has occurred in parallel with the increase in community-acquired infection. However, our finding of elevated indoor concentrations compared to outdoor reference samples indicates the need for further evaluation of the implications of this indoor-outdoor relationship. The extent to which these elevated concentrations increase the risk of adverse health outcomes or simply reflect the increasing burden of resistant bacteria in our environment are issues that merit the attention of the scientific community. This attention is particularly needed for the most vulnerable in society. Much of the concern regarding the emergence of resistant S. aureus infections in the community has resulted from reports of methicillin-resistant S. aureus (MRSA) isolated from children (Chambers 2001). S. aureus is a significant pathogen in children and causes illnesses ranging from minor soft tissue lesions to life-threatening infections (Marcinak and Frank 2003). Risk factors for MRSA infection have traditionally been thought to include intravenous drug use intravenous drug use Intravenous drug abuse The habitual IV injection of drugs of abuse Epidemiology In the US ± 2.5 million–population ± 235 million have used IVDs Infections Pyogenic–eg, endocarditis, pneumonia, sepsis Common agents , serious underlying illness, previous antimicrobial therapy, prolonged hospitalization, and invasive or surgical procedures Surgical procedures have long and possibly daunting names. The meaning of many surgical procedure names can often be understood if the name is broken into parts. For example in splenectomy, "ectomy" is a suffix meaning the removal of a part of the body. "Splene-" means spleen. (Herold et al. 1998; Maranan et al. 1997). However, since the 1990s there has been an increase in community-acquired MRSA infections among healthy children without known risk factors [Centers for Disease Control and Prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. (CDC See Control Data, century date change and Back Orifice.
CDC - Control Data Corporation ) 2006; Marcinak and Frank 2003]. This increase has been documented in both hospital-based studies (Gorak et al. 1999; Herold et al. 1998; Hussain et al. 2000) and case reports of outbreaks among newborns (CDC 2006), as well as infections resulting in the death of four children in the midwestern United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. (CDC 1999).
In any investigation, potential confounders in the role that airborne S. aureus plays in adverse human health outcomes include its near ubiquity in the human environment and its carriage by approximately 30% of healthy humans (Garcia-Lara et al. 2005). Rates of infection are higher in carriers than noncarriers, and nasal carriage of the organism is a major risk factor for staphylococcal staphylococcal
pertaining to Staphylococcus spp.
staphylococcal clumping test
used as a means of measuring the quantity of fibrinogen-split products in a sample of blood. disease (Peacock et al. 2001). To clearly discern the role of the airborne bacterium in the causation of health effects, most epidemiologic investigations would benefit from separate assessments of carriers and noncarriers. The near ubiquity of the organisms in the human environment presents significant challenges in not only the measurement of airborne concentrations but also in the determination of potential sources of any elevated concentrations. These challenges are present in addition to those already limiting the assessment of bacterial aerosols in the indoor environment. These limitations, while significant, should not prevent future investigation into this important issue.
Culturable S. aureus was recovered inside each of 24 houses sampled and in 23 of the outdoor reference samples. S. aureus isolates resistant to both penicillin and ampicillin were recovered inside 22 of 24 study homes, whereas isolates resistant to cefaclor were recovered in 14 of 24 homes. Trends in our data suggest that resistant strains were present in higher concentrations inside homes compared to outside the homes. The findings of the present study, in combination with existing literature documenting the increase in community-acquired infections caused by resistant strains of S. aureus, indicate the need for further research into the role that aerosolized organisms play in the causation of adverse health of building occupants.
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Angelina Gandara, (1) Linda C. Mota, (1) Carissa Flores Flores, town, Guatemala
Flores (flōrəs), town (1990 est. pop. 2,200), capital of Petén department, N Guatemala. Flores was built on an island in the southern part of Lake Petén Itzá and on the site of the , (1) Hernando R. Perez, (2) Christopher F. Green, (3) and Shawn G. Gibbs (1)
(1) The University of Texas Health Science Center at Houston, School of Public Health, El Paso, Texas, USA; (2) Drexel University Drexel University, at Philadelphia, Pa.; coeducational; founded 1891 by Anthony J. Drexel, opened 1892, chartered 1894 as Drexel Institute of Art, Science, and Industry. It was renamed Drexel Institute of Technology in 1936 and gained university status in 1970. , School of Public Health, Philadelphia, Pennsylvania, USA; (3) Department of Civil and Environmental Engineering, University of Cincinnati The University of Cincinnati is a coeducational public research university in Cincinnati, Ohio. Ranked as one of America’s top 25 public research universities and in the top 50 of all American research universities, , Cincinnati, Ohio “Cincinnati” redirects here. For other uses, see Cincinnati (disambiguation).
Cincinnati is a city in the U.S. state of Ohio and the county seat of Hamilton County. , USA
Address correspondence to S.G. Gibbs, The University of Texas Health Science Center at Houston, School of Public Health, 1100 N. Stanton, Suite 110, El Paso, TX 79902 USA. Telephone: (915) 747-8582. Fax: (915) 747-8512. E-mail: firstname.lastname@example.org
This research was partially funded by Hot Projects, an initiative of the Paso del Norte Del Norte can refer to multiple things:
The authors declare they have no competing financial interests.
Received 7 August 2006; accepted 7 September 2006.
Table 1. NCCLS zone diameters used to categorize S. aureus recovered as susceptible, intermediate, or resistant. Zone diameter interpretive standards (mm) (a) Antimicrobial agent Disk potency ([micro]g) Resistant Ampicillin 10 [less than or equal to] 28 Cefaclor 30 [less than or equal to] 14 Penicillin 10 [less than or equal to] 28 Zone diameter interpretive standard (mm) (a) Antimicrobial agent Intermediate Susceptible Ampicillin -- [greater than or equal] 29 Cefaclor 15-17 [greater than or equal] 18 Penicillin -- [greater than or equal] 29 (a) These standards were adapted from NCCLS (1997, 2000, 2001). Table 2. Summary of climatic conditions for all homes. Mean [+ or -] SD Minimum Maximum Temperature ([degrees]C) Inside 18.96 [+ or -] 2.14 15 24 Outside 15.38 [+ or -] 6.01 7 30 Relative humidity (%) Inside 27.08 [+ or -] 3.96 23 42 Outside 27.50 [+ or -] 4.27 20 38 Barometric pressure (mmHg) Inside 882.63 [+ or -] 7.20 869 895 Outside 882.58 [+ or -] 7.08 869 894 Table 3. Average recovered concentrations (CFU/[m.sup.3]) of respirable S. aureus and heterotrophic organisms from inside each home. Heterotrophic S. aureus within House S. aureus organisms heterotrophic organisms (%) 1 2.94 173.73 1.69 2 7.36 692.87 1.06 3 4.42 607.18 0.73 4 29.74 389.87 7.63 5 17.08 623.38 2.74 6 9.42 839.22 1.12 7 11.19 505.89 2.21 8 5.01 154.59 3.24 9 9.42 456.12 2.07 10 37.69 883.39 4.27 11 13.55 274.15 4.94 12 20.02 790.64 2.53 13 20.02 673.14 2.97 14 3.53 328.92 1.07 15 13.25 254.71 5.20 16 0.59 209.95 0.28 17 6.48 441.11 1.47 18 1.77 655.48 0.27 19 3.24 214.66 1.51 20 2.65 373.67 0.71 21 39.46 318.61 12.38 22 53.30 664.31 8.02 23 21.20 336.28 6.30 24 35.92 178.74 20.10 Mean 15.39 460.23 3.94 [Q.sub.0] 0.59 154.59 0.27 [Q.sub.1] 4.20 269.29 1.11 [Q.sub.2] 10.31 415.49 2.37 [Q.sub.3] 20.32 657.69 5.01 [Q.sub.4] 53.30 883.39 20.10 Table 4. Average recovered concentrations (CFU/[m.sup.3]) of respirable S. aureus and heterotrophic organisms from outside each home. Heterotrophic S. aureus within House S. aureus organisms heterotrophic organisms (%) 1 4.12 223.20 1.85 2 7.66 159.01 4.81 3 3.83 723.20 0.53 4 0.00 62.43 0.00 5 5.89 213.19 2.76 6 4.12 243.42 1.69 7 24.73 278.56 8.88 8 2.36 137.22 1.72 9 8.83 356.30 2.48 10 5.89 81.27 7.25 11 2.94 242.05 1.22 12 10.60 441.11 2.40 13 9.42 294.46 3.20 14 0.59 108.36 0.54 15 32.98 883.39 3.73 16 2.36 443.46 0.53 17 13.55 402.83 3.36 18 2.36 883.39 0.27 19 6.48 375.74 1.72 20 7.07 574.20 1.23 21 74.79 641.64 11.66 22 45.35 378.09 11.99 23 16.49 44.17 37.33 24 10.60 98.35 10.78 Mean 12.63 345.38 5.08 [Q.sub.0] 0.00 44.17 0.00 [Q.sub.1] 3.61 153.56 1.23 [Q.sub.2] 6.77 286.51 2.44 [Q.sub.3] 11.34 441.70 5.42 [Q.sub.4] 74.79 883.39 37.33 Table 5. Antibiotic resistance of evaluated recoverable respirable S. aureus from inside each home. Ampicillin Penicillin House N [N.sub.r] Percent [N.sub.r] Percent 1 1 0 0.00 0 0.00 2 6 2 33.33 3 50.00 3 7 2 28.57 2 28.57 4 8 6 75.00 6 75.00 5 7 4 57.14 5 71.43 6 8 5 62.50 4 50.00 7 8 2 25.00 3 37.50 8 3 2 66.67 3 100.00 9 4 1 25.00 3 75.00 10 17 6 35.29 6 35.29 11 8 6 75.00 5 62.50 12 9 6 66.67 6 66.67 13 11 7 63.64 7 63.64 14 5 2 40.00 2 40.00 15 16 8 50.00 8 50.00 16 (a) 0 -- -- -- -- 17 5 4 80.00 4 80.00 18 6 3 50.00 3 50.00 19 2 2 100.00 2 100.00 20 3 2 66.67 3 100.00 21 13 9 69.23 9 69.23 22 12 4 33.33 4 33.33 23 13 8 61.54 8 61.54 24 11 10 90.91 10 90.91 Mean 54.59 60.46 [Q.sub.0] 0.00 0.00 [Q.sub.1] 34.31 45.00 [Q.sub.2] 61.54 62.50 [Q.sub.3] 67.95 75.00 [Q.sub.4] 100.00 100.00 Cefaclor Multidrug House [N.sub.r] Percent [N.sub.r] Percent 1 0 0.00 0 0.00 2 1 16.67 1 16.67 3 0 0.00 0 0.00 4 2 25.00 2 25.00 5 2 28.57 2 28.57 6 0 0.00 0 0.00 7 1 12.50 1 12.50 8 0 0.00 0 0.00 9 1 25.00 1 25.00 10 1 5.88 1 5.88 11 1 12.50 1 12.50 12 2 22.22 2 22.22 13 0 0.00 0 0.00 14 1 20.00 1 20.00 15 4 25.00 4 25.00 16 (a) -- -- -- -- 17 3 60.00 3 60.00 18 0 0.00 0 0.00 19 0 0.00 0 0.00 20 0 0.00 0 0.00 21 1 7.69 1 7.69 22 0 0.00 0 0.00 23 2 15.38 2 15.38 24 3 27.27 3 27.27 Mean 13.20 13.20 [Q.sub.0] 0.00 0.00 [Q.sub.1] 12.50 12.50 [Q.sub.2] 23.61 23.61 [Q.sub.3] 60.00 60.00 [Q.sub.4] 60.00 60.00 Abbreviations: N, number or organisms evaluated; [N.sub.r], number of resistant organisms. (a) No organisms could be isolated for resistance testing. Table 6. Antibiotic resistance of evaluated recoverable respirable S. aureus from outside each home. Ampicillin Penicillin House N [N.sub.r] Percent [N.sub.r] Percent 1 3 1 33.33 3 100.00 2 2 0 0.00 0 0.00 3 3 1 33.33 1 33.33 4 (a) 0 -- -- -- -- 5 2 0 0.00 0 0.00 6 2 0 0.00 0 0.00 7 10 7 70.00 7 70.00 8 1 0 0.00 0 0.00 9 5 1 20.00 1 20.00 10 1 0 0.00 0 0.00 11 (a) 0 -- -- -- -- 12 6 2 33.33 3 50.00 13 7 5 71.43 6 85.71 14 (a) 0 -- -- -- -- 15 4 1 25.00 1 25.00 16 2 0 0.00 0 0.00 17 5 4 80.00 4 80.00 18 1 1 100.00 1 100.00 19 2 1 50.00 1 50.00 20 2 1 50.00 2 100.00 21 17 8 47.06 8 47.06 22 4 1 25.00 1 25.00 23 (a) 0 -- -- -- -- 24 6 3 50.00 3 50.00 Mean 34.42 41.81 [Q.sub.0] 0.00 0.00 [Q.sub.1] 0.00 0.00 [Q.sub.2] 33.33 40.20 [Q.sub.3] 50.00 72.50 [Q.sub.4] 100.00 100.00 Cefaclor Multidrug House [N.sub.r] Percent [N.sub.r] Percent 1 1 33.33 1 33.33 2 0 0.00 0 0.00 3 1 33.33 1 33.33 4 (a) -- -- -- -- 5 0 0.00 0 0.00 6 0 0.00 0 0.00 7 0 0.00 0 0.00 8 0 0.00 0 0.00 9 0 0.00 0 0.00 10 0 0.00 0 0.00 11 (a) -- -- -- -- 12 0 0.00 0 0.00 13 0 0.00 0 0.00 14 (a) -- -- -- -- 15 0 0.00 0 0.00 16 0 0.00 0 0.00 17 2 40.00 2 40.00 18 1 100.00 1 100.00 19 0 0.00 0 0.00 20 1 50.00 1 50.00 21 1 5.88 1 5.88 22 0 0.00 0 0.00 23 (a) -- -- -- -- 24 1 16.67 1 16.67 Mean 13.96 13.96 [Q.sub.0] 0.00 0.00 [Q.sub.1] 0.00 0.00 [Q.sub.2] 0.00 0.00 [Q.sub.3] 20.83 20.83 [Q.sub.4] 100.00 100.00 Abbreviations: N, number or organisms evaluated; [N.sub.r], number of resistant organisms. (a) No organisms could be isolated for resistance testing.