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Automated blood culture testing: a retrospective study indicates that a three-day incubation period is sufficient.

Blood culture is an essential tool for the investigation of clinically suspected bacteremia or septicemia. A timely detection of organism type and antibiotic susceptibility testing is critical for the effective treatment of the patient, and it is a primary tool to decrease healthcare-acquired infections (HAI) and to reduce methicillin-resistant Staphylococcus aureus (MRSA). We retrospectively analyzed 38,784 blood cultures over a six-month period from adult patients admitted at Temple University Hospital, Philadelphia (TUH), an urban teaching and tertiary care center. A total of 2,569 positive blood cultures from 721 patients were positive after five days of incubation. By day three, 95.8 percent of the organisms had been detected. Only 4.2 percent of the organisms were detected on day four and day five combined, and of these only one isolate was clinically significant-- and that patient had already been effectively treated. Based on these observations a three-day incubation period for automated blood culture testing should be seriously considered for routine continuous monitoring blood culture systems. In addition, rapid methods for the identification of pathogens from blood cultures are increasingly becoming more common as a tool to systematically reduce MRSA and HAIs.

Introduction

Bloodstream infections are serious problems in hospitals and frequently have grave consequences including shock, multiple organ failure, disseminated intravascular coagulation, and even death. Timely diagnosis and detection of blood-borne pathogens is of pivotal importance in effective management of bloodstream infections. Blood culture is an essential tool for investigation of clinically suspected bacteremia or septicemia, and guidance for appropriate antimicrobial management. (1-6) The rapid identification of important pathogens such as MRSA from blood cultures can aid significantly in the reduction of HAIs and aid in the overall Infection Control and Prevention activities within the hospital environment. Comprehensive reviews and recent studies have documented the optimal timing of specimen collection, the use of prompt Gram staining of blood cultures, and the detection of fastidious pathogens. (7-9)

Over the past few decades, multiple automated blood culture systems have been developed with significant improvement in reliability and time to detection of bacteria and yeasts. (10) In fact, the standard approach for most clinical microbiology laboratories in the U.S., Canada, the EU and other developed countries relies heavily on highly automated systems for routine blood cultures, and for the identification and antimicrobial susceptibility testing of bacteria and commonly encountered yeasts. In clinical microbiology laboratories the near future holds even more promise for continued and expanded automation in all aspects of diagnostic microbiology specimen handling, testing, analysis and reporting. (11)

The current standard for automated blood culture testing as recommended by the College of American Pathologists (CAP) is a five-day incubation period (CAP checklist, 2014); and even for the more fastidious so-called HACEK group of organisms (e.g., Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella) and Brucella spp., incubation beyond the five-day period is seldom required. (12) Mycobacteria, dimorphic fungi, and other more fastidious microorganisms may require longer incubation periods and special media, or non-culture based methods, including molecular approaches. (3,4)

Several studies have documented shorter incubation periods to obtain relevant clinical information from blood cultures for patient management, including three-day and four-day protocols. (13-17) The standard, however, has remained a five-day incubation period, and this recommendation has been made as recently as 2011. (6)

Automated blood culture systems are available from different manufacturers and are used commonly in high-volume clinical microbiology laboratories, and they have undergone extensive analysis since their introduction. (18-19) Most, if not all, of the published studies evaluating the various automated blood culture systems have demonstrated rough equivalency in detecting pathogens commonly encountered in human infections. However, variations in selected microorganisms have been documented from one automated system to another, which probably is the result of different media formulations.

The primary aim of this study and review is to update the current information and knowledge of automated blood culture testing and assess time of positivity using an automated blood culture system. We retrospectively analyzed results of 38,784 consecutive blood cultures collected from adult patients at Temple University Hospital, Philadelphia (TUH). The cultures were performed over a six-month period. All results were obtained from software of the blood culture system, from archives of the Department of Pathology and Laboratory Medicine and from medical records at TUH. We also evaluated the clinical significance of all of the late positive cultures detected during the five-day incubation period.

Materials and methods

A total of 38,784 blood cultures from adult patients admitted at TUH, an urban teaching and tertiary care center, were analyzed over a six-month period. All blood cultures were performed using pairs of aerobic and anaerobic culture bottles. A maximum amount of 10 ml blood was collected in each bottle (20 ml per venipuncture). When the instrument registered a positive signal, the bottles were examined by Gram stain and subcultured to five percent sheep blood agar and chocolate agars. Any specimen that was positive on subculture was considered positive. Time of positivity was recorded and included in the analysis. Bottles with no positive signal after five full days of incubation were considered negative and discarded on the sixth day. Isolated bacteria and yeast were identified by either automated identification systems or by rapid methods. Designated fungal or mycobacterial cultures which were performed by lysis centrifugation were not included in this study.

Data acquisition and analysis

Data was acquired retrospectively from the automated blood culture system, from the laboratory information system (LIS) or from TUH medical record archives of blood cultures, which were received in the clinical microbiology laboratory during the six-month period. The patient's name, accession number, date and number of bottles received, earliest date of positive results, number of positive bottles, and final organism identification were recorded and evaluated. Positive bottles and the bacteria/yeasts isolated were manually and electronically sorted and categorized according to the day of positivity first detected in any bottle. Positive culture data by the earliest detection day was documented and evaluated. The organisms considered pathogenic were grouped into "usual pathogens," and those considered contaminants were classified as "occasional pathogens/possible contaminants." Medical records of patients with day four and day five blood culture isolates were reviewed, and the clinical significance of these isolates was evaluated. Comparisons were also made between the current study and data collected during earlier studies from this institution and from other centers.

[FIGURE 2 OMITTED]

Results

Data from the blood cultures were collected and analyzed. A total of 2,746 organisms from 2,569 blood cultures were isolated from 721 patients. More than one organism was isolated from 154 blood culture bottles; the remaining 2,415 positive cultures had one organism. By day six, a total of 36,215 cultures remained negative and were discarded. By the end of day one, 61 percent of the organisms were detected, and 28.4 percent of the organisms were detected during the second day. By day three, 95.8 percent of the organisms were detected. Only 4.2 percent of the organisms were detected on day four and day five combined (Figure 1).

The isolated organisms are listed in Table 1. They were categorized into "usually pathogenic microorganisms" and "possible contaminants." Coagulase negative staphylococci, alpha hemolytic streptococci (not Streptococcus pneumoniae), diphtheroids, and Bacillus species other than Bacillus anthracis were considered as possible contaminants. The pathogens represented 63.5 percent of the isolates and possible contaminants 36.5 percent. Comparison of day of positivity between pathogens and occasional pathogens demonstrated only 3.1 percent of the pathogens were isolated on days four and five, compared to 6.2 percent of the possible contaminants. The most common organism and most common pathogen isolated was Staphylococcus aureus. It represented 43.6 percent of the pathogens. Bacteroides spp. were the most frequently isolated anaerobe (13 out of 37). Yeast represented 2.5 percent of the total isolates. Only one mold (Verticillium spp.) was isolated during the evaluation period.

Only 115 cultures (92 patients) became positive on days four and five. A total of 116 organisms were isolated from those 115 blood cultures. Medical records were reviewed from all of these patients to determine the clinical significance of the isolated organisms. Among 116 organisms isolated on days four and five, 76 organisms were already isolated from previously collected blood culture bottles, and they were considered insignificant, as these results did not change patient management. From the remaining 40 organisms, 33 organisms were considered likely contaminants. Further review of patient charts confirmed that six more organisms were clinically insignificant. Only one organism was considered clinically significant. Cryptococcus neoformans was isolated on day five from an HIV-positive patient. Appropriate antifungal therapy had already been initiated based on clinical features, and therefore antimicrobial therapy was not modified.

Discussion

The incubation period employed for automated continuous-monitoring blood culture systems, when introduced, was six to seven days. The currently recommended incubation period is now commonly accepted as five days. In this study, we reviewed the time to positivity for 38,784 blood cultures over a period of six months. We have shown that more than 95 percent of organisms from blood cultures were detected within three days of incubation. This is almost identical to the previous blood culture study reported by this laboratory (16) and by others. (8,14) At least one study has shown that 97 percent of significant isolates were recovered within three days of incubation. (13) Only 116 organisms out of a total of 2,746 were isolated after the third day of incubation. Review of clinical information for days four and five isolates demonstrated that they were of limited clinical significance. Similar studies using different automated blood culture systems have shown that three or four days of incubation may be sufficient to detect clinically significant organisms. (13-17)

The most common organisms isolated after the third day of incubation were Staphylococcus aureus, coagulase-negative staphylocci, and diphtheroids. These organisms constituted 71.6 percent of the fourth and fifth day isolates. All of these organisms were considered to be either contaminants or clinically not significant.

Only 3.1 percent of what were classified as "usually pathogenic organisms" were isolated on the fourth and fifth day compared to 6.2 percent of "possible" contaminants. More than 50 percent of the organisms isolated on days four and five were possible contaminants. It is becoming increasingly obvious, from many studies over a number of years, that as one increases the incubation time; it becomes more likely that a potential contaminant, not a pathogenic organism, will be isolated. (Figure 2).

Of note, Cryptococcus neoformans is notorious as being a slowly growing organism. Six out of eight isolates in this study were detected on day three of incubation, and one isolate even took more than four days to become positive. Therefore, we believe that it is reasonable to incubate for a full five days, or even longer, before declaring a culture negative if this organism or other fastidious or slowly growing microorganisms are clinically suspected. Overall, it should be kept in mind that yeast are more likely to be isolated later than bacteria. More than 10 percent of yeasts were isolated in this study on the fourth and fifth day, compared to less than five percent of bacteria.

The real cost savings of implementing a three- or four-day routine automated blood culture protocol could be significant, since the laboratory would experience reduced time and effort expended in the identification and occasional antibiotic susceptibility testing of contaminants and clinically insignificant isolates. In addition to laboratorians' time and effort, other clear advantages would include a reduction in media costs; the number of instruments needed by the laboratory and related finance and service costs; time spent by healthcare professionals in the interpretation of possible contaminants; and pharmacy costs incurred in the treatment of patients with contaminating organisms. Perhaps most important, additional time and financial resources could be dedicated to other, arguably more important, clinical aspects of patient care. These might include rapid molecular and other testing directly from positive blood cultures, implementation of new testing modalities such as MALDI-ToF, complete laboratory automation, gene sequencing, and infection prevention and control, all of which could be important components in an effort to reduce HAIs.

Additionally, any potential downside of a policy of decreased time of incubation could be mitigated at any time by the ordering of an additional blood culture set (or two) for a patient suspected of harboring a difficult pathogen, or the request for extended incubation time for rarely encountered fastidious microorganisms. That is, exceptions could be made when the situation warranted them.

Conclusion

Essentially, all studies evaluating automated blood culture systems provide information for those particular systems and software/hardware configurations at the participating institutions. This study and other similar studies have repeatedly demonstrated that a three- or four-day incubation period for blood cultures is sufficient for the isolation of clinically significant organisms. When results of different studies are compared, it should be understood that commercial blood culture systems, media and software are frequently upgraded and modified. Each healthcare institution should evaluate the appropriate incubation time for its instruments and its patient population. Nonetheless, it appears evident from this study and others that a three-day incubation period for automated blood culture testing should be seriously considered for routine continuous monitoring blood culture systems, and one could argue convincingly that the time for such consideration is now.

ACKNOWLEDGEMENT

A part of this study was presented at 112th General Meeting of the American Society for Microbiology (Control #2195, C02; Diagnostic Bacteriology Identification), 2012, San Francisco, CA.

REFERENCES

(1.) Baron EJ, Miller JM, Weinstein MP, et. al. A guide to utilization of the microbiology laboratory for diagnosis of infectious diseases: 2013 recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM)(a). Clinical infectious diseases: an official publication of the Infectious Diseases Society of America, 57, e22-e121.

(2.) Baron EJ, Weinstein M, Dunne W, Yagupsky P, Welch D, Wilson D.2005. Cumitech 1C: blood cultures IV. Coordinating ed, Baron EJ American Society for Microbiology, Washington, DC.

(3.) Deck MK, Anderson ES, Buckner RJ, et al. Multicenter evaluation of the Staphylococcus QuickFISH method for simultaneous identification of Staphylococcus aureus and coagulase-negative staphylococci directly from blood culture bottles in less than 30 minutes. J Clin Microbiol. 2012; 50:1994-1998.

(4.) Deck MK, Anderson ES, Buckner RJ, et al. MJ. Rapid detection of Enterococcus spp. direct from blood culture bottles using Enterococcus QuickFISH method: a multicenter investigation. Diag Microbiol Infect Dis. 2014; 78:338-342.

(5.) Kirn TJ, Weinstein MP. Update on blood cultures: how to obtain, process, report, and interpret. Clin Microbiol Infect. 2013; 19: 513-520.

(6.) Weinstein MP, Doern GV. A critical appraisal of the role of the clinical microbiology laboratory in the diagnosis of bloodstream infections. J Clin Microbiol.2011;49: S26-S29.

(7.) Barenfanger J, Graham DR, Kolluri L, et al. Decreased mortality associated with prompt Gram staining of blood cultures. Amer J Clin Pathol, 2008; 130(61:870-876.

(8.) Doern GV. Detection of selected fastidious bacteria. Clin Infect Dis. 2000:30:166-173.

(9.) Riedel S, Bourbeau P, Swartz B, et al. Timing of specimen collection for blood cultures from febrile patients with bacteremia. J Clin Microbiol 2008; 46:1381-1385.

(10.) Weinstein MP, Reller LB. Commercial Blood Culture Systems and Methods. In A. Truant Ed, Manual of Commercial Methods in Clinical Microbiology. American Society of Microbiology.

(11.) Bourbeau PP, Ledeboer NA Automation in clinical microbiology. J Clin Microbiol. 2013; 51:1658-1665.

(12.) Baron EJ, Scott JD, Tompkins LS. Prolonged incubation and extensive subculturing do not increase recovery of clinically significant microorganisms from standard automated blood cultures. Clin Infect Dis. 2005; 41:1677-1680.

(13.) Bourbeau PP, Pohlman JK. Three days of incubation may be sufficient for routine blood cultures with BacT/Alert FAN blood culture bottles. J Clin Microbiol. 2001;33:2079-2082.

(14.) Doern GV, Brueggemann AB, Dunne. WM, Jenkins SG, Halstead DC, McLaughlin JC. (1997) Four-day incubation period for blood culture bottles processed with the Difco ESP blood culture system. J Clin Microbiol. 1997; 35:1290-1292.

(15.) Evans MR, Truant AL, Kostman J, Locke L. The detection of positive blood cultures by the BACTEC NR660. The clinical importance of four-day versus seven-day testing. Diagn Microbiol Infect Dis. 1991; 14:107-110.

(16.) Han XY, Truant AL (1999) The detection of positive blood cultures by the AccuMed ESP-384 system: the clinical significance of three-day testing. Diagn Microbiol Infect Dis. 1999; 33:1-6.

(17.) Johnson AS, Touchie C, Haldane DJ, Forward KR (2000) Four-day incubation for detection of bacteremia using the BACTEC 9240. Diagn Microbiol Infect Dis 2000; 38:195-199.

(18.) Dreyer AW, Ismail NA, Nkosi D. Comparison of the VersaTREK blood culture system against the Bactec9240 system in patients with suspected bloodstream infections. Ann Clin Microbiol Antimicrob. 2011; 10.4.

(19.) Mirrett S, Hanson KE, Reller LB. Controlled clinical comparison of VersaTREK and BacT/ALERT blood culture systems. J Clin Microbiol. 2007; 45:299-302.

Continuing Education

To earn CEUs, see the test on page 16 or online at www.mlo-online.com under the CE Tests tab.

LEARNING OBJECTIVES

Upon completion of these articles, the reader will be able to:

1. Identify how the use of automated blood culture testing can be improved.

2. Identify findings from the research study by the authors.

3. Describe methods and materials used for the research study.

4. Identify conclusions made by the authors.

TEST QUESTIONS

1. The essential tool for investigation of clinically suspected septicemia is the

a. CBC.

b. UA.

c. blood culture.

d. CMP.

2. Detection of blood-borne pathogens is necessary for determining appropriate microbial management.

a. True

b. False

3. Rapid identification of pathogens may increase the number of healthcare-acquired infections.

a. True

b. False

4. The College of American Pathologists-recommended incubation period for automated blood culture testing is

a. one day.

b. three days.

c. five days.

d. seven days.

5. Longer-than-recommended incubation periods may be required to isolate which of the following?

a. mycobacteria

b. fungi

c. fastidious organisms

d. all of the above

6. This study analyzed 38,784 blood cultures over a period of

a. one year.

b. six months.

c. one month.

d. two weeks.

7. The standard method of blood culture testing is the collection of pairs of aerobic and anaerobic culture bottles.

a. True

b. False

8. The typical (recommended) amount of blood collected by venipuncture and added to each blood culture bottle is

a. 1 ml.

b. 3 ml.

c. 5 ml.

d. 10 ml.

9. In this study, a signal from the automated blood culture indicating a positive result required

a. examination of culture by gram stain.

b. subculture to sheep blood agar.

c. subculture to chocolate agar.d. all of the above.

10. These researchers wanted to investigate and report on the first day of positivity detected by the automated blood culture system.

a. True

b. False

11. These researchers determined that the percentage of organisms detected by day three was

a. 4.2%.

b. 28.4%.

c. 61%.

d. 95.8%.

12. Isolated organisms were categorized as pathogenic and nonpathogenic.

a. True

b. False

13. Which of the following organisms is NOT considered a possible contaminant?

a. Coagulase negative staphylococci.

b. Diptheroids.

c. Staphylococcus aureus.

d. Alpha hemolytic streptococci.

14. The organism found representing 43.6% of the pathogens was

a. Staphylococcus aureus.

b. Bacteroides spp.

c. E. coli.

d. Acinetobacter complex.

15. Of the cultures that became positive on days four and five, the only organism found to be clinically significant was

a. Acinetobacter complex.

b. Bacteroides spp.

c. E. coli.

d. Cryptococcus neoformans.

16. The authors of this study showed that more than 95% of organisms from blood cultures were detected within three days of incubation. This corresponds to a previous study of blood cultures.

a. True

b. False

17. As a general rule, yeast takes longer to grow and thus is more likely to be isolated later than bacteria.

a. True

b. False

18. According to these researchers, implementation of a three- or four-day automated blood culture protocol would

a. reduce time to identification of organisms.

b. reduce media costs.

c. reduce pharmacy costs.

d. all of the above.

19. According to this study, the most common organism recovered by automated blood culture systems in the Enterobacteriaceae family was

a. Proteus mira bilis.

b. Enterobacter aerogenes.

c. Escherichia coli.

d. Klebsiella pneumonia.

20. Of the possible contaminants identified by this study, the organism found most often was

a. Candida albicans.

b. Staphylococcus aureus.

c. Coagulase negative Staphylococci.

d. Bacillus spp. (not B. anthracis)

Raghava Potula, MHA, PhD, is an Assistant Professor of Pathology and Laboratory Medicine and Center for Substance Abuse Research at Temple University School of Medicine. He serves as Associate Director of the Clinical Microbiology, Immunology, and Virology Laboratories at Temple University Hospital.

Vipul Dadhania, MD, completed his Anatomic-Clinical Pathology residency training at Temple University Hospital.

Allan L. Truant, PhD, serves as Director of the Clinical Microbiology, Immunology and Virology Laboratories, and is a Professor of Pathology and Laboratory Medicine, Microbiology and Immunology, and Medicine at Temple University Hospital and School of Medicine.
Table 1. Time to recovery of microorganisms from automated blood
culture system

                                          Number of
                                        microorganisms
Organism                                  recovered
Usually pathogenic microorganisms           by day

                                              1           2     3

Gram-positive cocci
Staphylococcus aureus                        410         261    75
Streptococcus agalactiae                      30          0     0
Streptococcus pneumoniae                      51          0     0
Group G Streptococcus                         9           0     0
Streptococcus pyogenes                        22          1     0
Enterococcus avium                            3           0     0
Enterococcus faecalis                         78          7     5
Enterococcus faecium                          38          6     0
Micrococcus spp.                              6           6     1
Aerobic gram-positive bacilli
Arcanobacterium spp.                          0           3     0
Enterobacteriaceae
Escherichia coli                             165          18    6
Enterobacter aerogenes                        3           1     0
Enterobacter cloacae                          64          15    1
Klebsiella oxytoca                            12          0     0
Klebsiella pneumoniae                        142          22    3
Morganella morganii                           4           0     0
Proteus mirabilis                             26          5     1
Providencia rettgeri                          3           0     0
Salmonella spp.                               11          2     0
Serratia marcescens                           20          7     2
Other gram-negative bacilli
Alcaligenes spp.                              1           1     0
Acinetobacter calcoaceticus-baumanii
  complex                                     21          3     0
Acinetobacter Iwoffii                         1           0     0
Haemophilus parainfluenzae                    0           1     4
Haemophilus influenzae                        6           2     1
Pasteurella multocida                         2           0     0
Pseudomonas aeruginosa                        19          7     0
Pseudomonas putida                            1           0     0
Sphingomonas paucimobilis                     0           1     0
Stenotrophomonas maltophila                   7           3     1
Nocardia spp.                                 0           3     0
Anaerobes
Bacteroides fragilis                          0           2     0
Bacteroides thetaiotaomicron                  0           3     0
Bacteroides uniformis                         0           7     0
Bacteroides distasonis                        0           1     0
Clostridium perfringens                       6           0     0
Other Clostridium spp.                        1           2     0
Fusobacterium necrophorum                     1           1     0
Gemella morbillorum                           0           1     0
Veillonella spp.                              0           0     1
Peptostreptococcus anaerobius                 0           0     2
Peptostreptococcus asaccharolyticus           1           0     1
Peptostreptococcus micros                     0           1     0
Peptostreptococcus prevotti                   1           0     0
Prevotella bivia                              0           1     0
Prevotella loescheii                          0           1     0
Prevotella oralis                             2           0     0
Yeast
Candida albicans                              1           8     2
Candida glabrata                              8           12    4
Candida krusei                                1           1     2
Candida parapsilosis                          1           1     3
Candida tropicalis                            2           5     0
Cryptococcus neoformans                       0           1     6
Rhodotorula rubra                             0           0     0
Trichosporon beigelii                         0           3     0
TOTAL PATHOGENS                              1180        426   121
Possible contaminants
Coagulase negative Staphylococci             385         286    35
Staphylococcus hyicus                         0           1     0
Streptococcus salivarius                      0           0     0
Streptococcus mitis                           4           1     0
Streptococcus mutans                          0           0     1
Streptococcus oralis                          3           1     0
Streptococcus parasanguinis                   0           1     0
Alpha hemolytic Streptococcus                 18          3     1
Microaerophilic Streptococcus                 0           5     1
Rhodococcus equi                              0           1     0
Bacillus spp (not B. anthracis)               70          19    5
Diphtheroids                                  15          35    10
Thermoactinomyces spp.                        0           0     0
Lactobacillus spp.                            0           1     1
Verticillium spp.                             0           0     0
TOTAL CONTAMINANTS                           495         354    54
TOTAL (BOTH CATEGORIES)                      1675        780   175

                                                        Total
Organism                                             of recovered
Usually pathogenic microorganisms                   microorganisms

                                        4     5

Gram-positive cocci
Staphylococcus aureus                   18    13         777
Streptococcus agalactiae                0     0           30
Streptococcus pneumoniae                0     0           51
Group G Streptococcus                   0     0           9
Streptococcus pyogenes                  0     0           23
Enterococcus avium                      0     0           3
Enterococcus faecalis                   0     2           92
Enterococcus faecium                    1     0           45
Micrococcus spp.                        0     0           13
Aerobic gram-positive bacilli
Arcanobacterium spp.                    0     0           3
Enterobacteriaceae
Escherichia coli                        1     2          192
Enterobacter aerogenes                  0     0           4
Enterobacter cloacae                    1     1           82
Klebsiella oxytoca                      0     0           12
Klebsiella pneumoniae                   2     3          172
Morganella morganii                     0     0           4
Proteus mirabilis                       0     0           32
Providencia rettgeri                    0     0           3
Salmonella spp.                         3     0           16
Serratia marcescens                     0     0           29
Other gram-negative bacilli
Alcaligenes spp.                        0     0           2
Acinetobacter calcoaceticus-baumanii
  complex                               0     0           24
Acinetobacter Iwoffii                   0     0           1
Haemophilus parainfluenzae              0     0           5
Haemophilus influenzae                  0     0           9
Pasteurella multocida                   0     0           2
Pseudomonas aeruginosa                  0     0           26
Pseudomonas putida                      0     0           1
Sphingomonas paucimobilis               0     0           1
Stenotrophomonas maltophila             0     0           11
Nocardia spp.                           1     0           4
Anaerobes
Bacteroides fragilis                    0     0           2
Bacteroides thetaiotaomicron            0     0           3
Bacteroides uniformis                   0     0           7
Bacteroides distasonis                  0     0           1
Clostridium perfringens                 0     0           6
Other Clostridium spp.                  0     0           3
Fusobacterium necrophorum               0     0           2
Gemella morbillorum                     0     0           1
Veillonella spp.                        0     0           1
Peptostreptococcus anaerobius           0     1           3
Peptostreptococcus asaccharolyticus     0     0           2
Peptostreptococcus micros               0     0           1
Peptostreptococcus prevotti             0     0           1
Prevotella bivia                        0     0           1
Prevotella loescheii                    0     0           1
Prevotella oralis                       0     0           2
Yeast
Candida albicans                        2     0           13
Candida glabrata                        2     0           26
Candida krusei                          0     0           4
Candida parapsilosis                    1     0           6
Candida tropicalis                      0     0           7
Cryptococcus neoformans                 0     1           8
Rhodotorula rubra                       1     0           1
Trichosporon beigelii                   0     0           3
TOTAL PATHOGENS                         33    23         1783
Possible contaminants
Coagulase negative Staphylococci        17    14         737
Staphylococcus hyicus                   0     0           1
Streptococcus salivarius                1     0           1
Streptococcus mitis                     0     0           5
Streptococcus mutans                    0     0           1
Streptococcus oralis                    0     0           4
Streptococcus parasanguinis             0     0           1
Alpha hemolytic Streptococcus           1     0           23
Microaerophilic Streptococcus           0     0           6
Rhodococcus equi                        0     0           1
Bacillus spp (not B. anthracis)         0     1           95
Diphtheroids                            12    9           81
Thermoactinomyces spp.                  1     0           1
Lactobacillus spp.                      2     1           5
Verticillium spp.                       0     1           1
TOTAL CONTAMINANTS                      34    26         963
TOTAL (BOTH CATEGORIES)                 67    49         2746

Figure 1. Percentage of microorganisms isolated by days of incubation

Day of incubation

1st                   61.0%
2nd                   28.4%
3rd                    6.4%
4th                    2.4%
5th                    1.8%

Note: Table made from bar graph.
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Title Annotation:CE: HAI/MRSA
Author:Potula, Raghava; Dadhania, Vipul; Truant, Allan L.
Publication:Medical Laboratory Observer
Article Type:Cover story
Geographic Code:1USA
Date:Sep 1, 2015
Words:4341
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