Gambling With Your Health: Bacterial Contamination on Casino Gaming Chips.
According to Saldmann (2008), the list of illness-causing bacteria and viruses that can be spread through casual hand-to-hand or inanimate object-to-hand contact includes: E. coli, Tatumella ptyseos, Serratia plymuthica, Citrobacter freundii, Proteus penneri, Erwinia, and Helicobacter pylori. By coming into contact with objects that have been contaminated by individuals who are carriers of these illness-causing bacteria and viruses, these infectious diseases can be spread through casual human contact. Further, if bacteria or viruses are deposited on an object, (e.g., someone infected with human influenza sneezes without covering their mouth), then the infectious bacterial organisms can live from several hours to up to 5 months on inanimate objects, depending on the environmental conditions (Brady, Fraser, Dunlop, Paterson-Brown, & Gibb, 2007; Kramer, Schwebke, & Kampf, 2006; Rutala, White, Gergen, & Weber, 2006; Saldmann, 2008).
In the medical and healthcare field, hand washing practices are determined by monitoring the bacterial levels located on objects such as keyboards and wireless communication devices (Brady et al., 2007; Rutala et al., 2006). The results of these studies show that despite continual use and cleaning, disinfectants were continually required to ensure that disease-causing microorganisms were controlled to safe levels (Brady et al., 2007; Rutala et al., 2006). This vigilant approach is critical, especially in light of research that disease-causing viruses can remain on everyday surfaces such as door knobs, desk tops, and chairs--even after disinfectants have been used to sanitize the contaminated area (Terpstra et al., 2007).
One of the major barriers to effectively controlling the spread of infectious diseases is proper personal hygiene, particularly hand washing. The Centers for Disease Control and Prevention (CDC) has worked to create the Clean Hands Count (CHC) campaign in an effort to "create and support coordinated, sustained initiatives to significantly improve health and save lives through clean hands" (Centers for Disease Control and Prevention [CDC], 2018a). Research has shown that public restrooms are a source of bacterial and viral infection because of improper hand washing (Allwood, Jenkins, Paulus, Johnson, & Hedberg, 2004; Bakalar, 2005; Berry, Mitteer, & Fourni er, 2014; de Kort & Velthuijsen, 2011; Guinan, McGuckinGuinan, & Sevareid, 1997; Oldfield, 2017). Further, if people are using public restrooms in a casino, then cross-contamination can occur on casino gaming chips, because studies have shown that on average, 35% of the U.S. population does not wash their hands after using the restroom (Altekruse, Yang, Timbo, & Angulo, 1999; Berry et al., 2014; Byrd-Bredbenner et al., 2007; "Did you wash your hands," 1996; Filion, Kukanich, Chapman, Hardigree, & Powell, 2011; Guinan et al., 1997).
It should be noted that even though 65% of the U.S. population has been found to wash their hands after using the restroom, the duration of hand washing does not reach the recommended time to ensure that hands are effectively cleaned. Berry and coauthors (2014) found that the average time that individuals wash hands after using the restroom was 8.1 s, with the range being 0.52-57.7 s. The Food and Drug Administration recommends that when washing hands, you should:
"(3) Rub together vigorously for at least 10 to 15 seconds while: (a) Paying particular attention to removing soil from underneath the fingernails during the cleaning procedure, and (b) Creating friction on the surfaces of the hands and arms or surrogate prosthetic devices for hands and arms, finger tips, and areas between the fingers" (U.S. Department of Health and Human Services, 2013, pp. 46-47).
Alternatively, CDC recommends that when washing hands, you should "rub your hands together vigorously for at least 15 seconds, covering all surfaces of the hands and fingers" (CDC, 2018b).
Casino employees and customers can be at risk for exposure to infectious diseases, especially bacterial diseases, through the handling of chips. A study by Mc Keown and coauthors (2011) was designed to determine if infectious bacteria were present on chips that were used by casino workers and customers by comparing the bacteria counts of these chips to new, never-used-before chips.
The purpose of this replication study was to determine to what degree the results obtained from the Mc Keown and coauthors' 2011 study, where both bacteria and fungi were present in statistically significant numbers on both the unused (factory) and used (in use at casinos) chips, were due to happenstance or instead indicate a serious health issue. The secondary purpose of this study was to determine if E. coli or coliforms are among the illness-causing bacteria found on the chips being studied. The information gathered from this study will provide recommendations that can reduce and prevent infectious bacterial disease among casino workers and customers.
The protocol for this study closely follows that which was outlined in Mc Keown and coauthors (2011) with changes made to the protocol outlined below. This study employs a case-control design to determine if infectious bacteria exist on chips. The in-use chips were purchased at a table game in the amount of $100 in $5 chips, resulting in a total of 20 chips being purchased for the study. The $5 denomination was chosen as a chip that is available at the various table games and is actively in use in games with minimum bets ranging from $1-$25.
Then, 13 chips that have never been used in a casino were compared with 13 chips that had been in play at an undisclosed casino in the Midwest. It was determined that the number 13 was used in the original study because the primary investigator was self-funding the study and that was how many blood-agar Petri dishes could be purchased.
In this study, a total of 20 chips ($5 denomination each) were collected from four different casinos, with 4 chips from a casino in the Gulf Coast and the other 15 chips (5 each) from three different casinos in Las Vegas, Nevada. Chips were randomly chosen in equal numbers from the four casinos until 13 chips had been tested. Each chip contains three sides (obverse or front, reverse or back, and side or rim), so a total of n = 78 tests were performed: 39 for the used chips, and 39 for the control group (never-used chips).
Obverse and reverse sides of the chips were determined based on the chip design and positioning of colored stripes in relation to wording and casino label. Chip labels closely oriented with the wording on the edge of the chip were considered the obverse side of the chip. In the Mc Keown and coauthors' 2011 study, chips were randomly removed from sterilized plastic containers marked as either used or unused using sterilized forceps.
In this study, two biologists performed the tests and directly removed the chips from the zip-sealed plastic bags that they were collected in from the casinos. One biologist performed the tests on the used chips and a different biologist performed the tests on the new, unused chips. The biologists wore neoprene gloves while handling the chips for testing. Between the testing of each chip, the testing area and gloves were sterilized with an alcohol solution of 70% ethanol. Each chip was then swabbed for bacteria using 6-in. sterile cotton-tipped applicators that had been dipped into a sterile solution of elution fluid containing 1% tween and 0.3% lecithin (Gaonkar, Geraldo, Shintre, & Modak, 2006).
The obverse side of the chip surface area was swabbed first, followed by the reverse side, and finally the rim. To gauge the degree in which the process might generate unique findings, we reversed swabs 22-27 to determine if swabbing order affected the results of the study. Additionally, we introduced a different bottle of sterile elution fluid at swab number 49. Both bottles of sterile elution fluid were made at the same time and both sterile elution fluids were tested before and after the study was completed. These steps were taken to determine that the elution fluids were not contaminated.
Swabs were then directly streaked across numbered blood agar Petri dishes, with the number corresponding to the location of the chip being swabbed to determine reactionary issues based on microorganism growth. For this study, larger Petri dishes were inadvertently acquired, so lines were drawn to create three equal areas. Each area was labeled either with an O, R, or E to reference the obverse (front), reverse (back), or edge (side) of the chip. The Petri dishes were also labeled with an identifier indicating from which of the four casinos it originated.
Once all the Petri dishes had been swabbed, they were placed upside down (optimal growing condition) in a growth incubator set at 37[degrees]C for 48 hr. After 48 hr, the Petri dishes were removed from the incubator and placed in a refrigerated cooling area until the results were analyzed. This protocol for growing bacteria from contaminated surfaces is standard procedure (Bykowski & Stevenson, 2008). At the end of the study, the purchased chips were used in other studies, then returned to the respective casinos and redeemed for the cash value.
We used analysis of variance (ANOVA) to measure the bacterial growth comparisons between the control and casino-used chips. We used the statistical program Stata version 10.1, which is considered a powerful statistical analysis package, to perform these tests. A probability of p < .05 was used for determining significant differences between the control versus casino-used chips for bacterial growth. A total of 78 samples (39 from each set of control chips and casino-used chips) offered enough statistical power (for [alpha] = .05, SD = 0.50, N = 78; power = 0.865) to determine the statistical significance noted above.
First, the plates were examined to determine the results (Figure 1). We used microscopic examination to identify cellular morphology and reaction (Figure 2). The bacteria cultured from the unused (control) chips were morphologically similar throughout each plate (Table 1). Bacteria on the unused casino chips consisted of grampositive bacillus (rodlike) populations on all plates analyzed (Table 2). According to the World Health Organization, Corynebacteria, Propionibacteria, and Staphylococcus epidermidis are common gram-positive bacteria that colonize human hands. Although gram-positive bacteria colonize the hands to a greater extent than gram-negative bacteria, a greater diversity of bacteria, fungi, and viruses are key features in the human hand microbiome compared to alternative sources of bacterial populations on inanimate objects (Cosseau et al., 2016; Wenzler, Fraidenburg, Scardina, & Danziger, 2016). Although outside the scope of this experimental design, the population of bacteria found on the unused chips might originate from the manufacturing and packaging process rather than direct human contact, thus explaining the low diversity of bacteria present on the surface of the chips.
The blood agar plates containing bacteria from the used chips displayed higher diversity of bacteria and fungi (Table 2). There were roughly 32% fungi and 68% bacteria on each plate. With the use of selective E. coli media and coliform media, we detected the presence of E. coli, a type of coliform and common food poisoning-related bacterium (Addis & Sisay, 2015). Plates 2, 4, 5, 6, 8, 11, and 12 contained both gram-positive and gram-negative bacillus and gram-negative cocci (spherical-like) bacteria. Furthermore, the identification of gram-negative cocci bacteria on plate 11 suggests the presence of genera Neisseria, Moraxella, or Kingella, which are causative agents for meningitis, sinusitis, and bronchopneumonia, and can be transmitted by genital-to-hand contamination (Wenzler et al., 2016; Zapka et al., 2011).
The presence of capsular and lipopolysaccharides increases pathogenicity and antiphagocytic qualities suitable for evading the human immune system and can provide genetic diversity for increased multidrug-resistant populations (Arora, Devi, Chadha, & Malhotra, 2009). The differences in bacteria and morphology found is typical of fomites that have been in contact with a multitude of people.
Limitations of the study include genus and species identification of the diverse microbial communities present on used and unused chips using molecular identification, such as DNA sequencing, genomics, or proteomics. Additionally, swabbing might underestimate the total populations on the various surfaces of the chips, because swabbing does not access microbes embedded in the textured layers of the surface. The human hand influences the spread of disease, leaving and picking up microbes with each touch. With the use of standardized methods and increasingly larger studies, we will increase our understanding of the impact of casino chip sanitation on health outcomes.
Of the 78 tests completed, each test produced results that are considered usable for this study. We counted the number of bacteria or fungi colonies that grew in the agar Petri dish. For bacteria, the 78 usable results had a mean of 14.03 colonies and a standard deviation of 7.61 with a range of 1-33 colonies; alternatively, the fungi resulted in a mean of 1.44 colonies and a standard deviation of 1.92 with a range of 0-10 colonies. The E. coli test showed a mean of 2.1 colonies and a standard deviation of 3.74 with a range of 0-19 colonies. The coliform test was negative for each case.
The ANOVA results [F(1,76) = 43.56, p < .001] indicated a statistically significant difference between the amount of bacteria found on used versus unused chips. According to the Bonferroni results, used chips have a higher mean score related to the number of bacteria found than that of unused chips, with a significance of p < .01. This study's measure of explained variation, however, shows that 36.43% of the variance in bacteria levels is explained by the differences between used and unused chips. Additionally, the fungi results were also statistically significant [F(1,77) = 99.89, p < .001], where 56.79% of the variance is explained by the difference between the used and unused chips. Finally, the E. coli results were also statistically significant [F(1,77) = 92.22, p < .001], where 54.82% of the variance is explained by the difference between the used and unused chips.
ANOVA was also performed to determine any differences in the swabbed areas (i.e., obverse, reverse, and edge). The bacteria, fungi, and E. coli found were not statistically significant for bacteria [F(2,77) = 1.19, p > .05], fungi [F(2,77) = 0.68, p > .05], or E. coli [F(2,77) = 1.87, p > .05]. The variance between the differences in the sections was 3.07% for bacteria, 1.77% for fungi, and 4.74% for E. coli.
Finally, the bacteria, fungi, and E. coli found on the obverse, reverse, and edge (p < .001) of the chips were statistically significant; however, the amount of explained variation for each test was low at 8.12%, 7.66%, and 6.95% for bacteria; 1.90%, 2.36%, and 1.38% for fungi; and 8.41%, 9.61%, and 6.24% for E. coli, respectively.
As illustrated above, both bacteria and fungi were found in statistically significant amounts on used and unused chips. This finding aligns with the Mc Keown and coauthors (2011) study, which found:
"Further microscopic examination of the cell arrangements of the yellow colonies, found on plates 1, 4, 24, 28, 36, 43, 46, 49, 53, 56, 68, 71, and 77, were diplococcic and in tetrads, which means that this was most likely a hand bacterium known as Micrococcus luteus (Greenblatt et al., 2004). The fungus showed conclusively under a microscope to be a fungus; however, without expensive DNA sequencing it was not possible to determine which type. Moreover, the fungus resulted in complete hemolysis (rupture or destruction of red blood cells) within the agar Petri dish, also known as beta-hemolysis ([beta]-hemolysis). This increased hemolysis suggested that the fungi were capable of being pathogenic."
With the increased awareness of disease-causing microorganisms and the previous pandemics associated with influenza, these results show that chips can be carriers of organisms that can cause illness in susceptible populations (e.g., older people who tend to spend time at casinos, or infants/toddlers who find colorful chips laying around a hotel room or cruise ship stateroom).
An undercover investigation by The Today Show found just as many germs on the handle of a slot machine (373, well above the failure mark of 100) as on elevator buttons (370) (Rossen & Davis, 2015). The cleanliness of casino hotels and cruise ships are constantly being monitored by their respective health districts; unfortunately, the Vessel Sanitation Program 2011 Operations Manual created by CDC has no specific information regarding cleaning and sanitizing of the casino area. Every other area within a cruise ship is listed, with specific requirements and sanitation protocols--except for the casino (CDC, 2011; Cramer, Blanton, & Otto, 2008). Even the Southern Nevada Health District, which monitors hotels and casinos in the Las Vegas area, has only four items in a casino that are required to be cleaned and sanitized in an effort to control and prevent norovirus: "Casino cage counters, gaming chair backs, contact areas of gaming tables, and table game cup holders" (Southern Nevada Health District, 2007).
While this study was conducted using chips from four casinos compared with one casino in the study by Mc Keown and coauthors (2011), it only explored one specific denomination, specifically, the $5 chip. Currently, there are hundreds of casinos around the world where chips are used and chips are available in multiple denominations, ranging from $1-$500 or higher; however, the $5 chips are actively used in just about all casinos and are available in large quantities.
After testing for multiple types of pathogens on multiple chips from multiple casinos, tests are being conducted to determine the best method for cleaning and sanitizing chips to ensure a healthy population, or if the chips should be redesigned to control for the ability to harbor these microorganisms. For example, we placed a chip in liquid bleach for 24 hours with no noticeable discoloration, in addition to placing a chip in an autoclave with no noticeable effects to the gaming chip. While these are two basic methods of sterilization, tests are being conducted on methods of sanitation that would be practical and usable within the casino industry. The eventual goal is to determine effective disease-prevention strategies for the safe handling and use of chips based on the presence of significant levels of infectious bacteria.
As a result, this study shows that additional studies need to be performed, and are being performed, to determine precisely the amounts and types of microorganisms that can be found on chips. Due to limited funds, the variability of chip denominations and casinos was sacrificed. In addition, limited funds dictated the amount of testing that was performed. Continued studies on casino chips will include DNA profiling of the microorganisms in addition to testing for possible viral pathogens.
Edward G. Mc Keown, PhD
Acknowledgements: The author wishes to thank graduate students Ryan Moreno and Victor Jimenez with the North Arizona University biology department for helping run the laboratory tests on the casino gaming chips. Funding for this research was provided by the School of Hotel & Restaurant Management in the W.A. Franke College of Business at Northern Arizona University.
Corresponding Author: Edward G. Mc Keown, P.O. Box 6315, Gulfport, MS 39506.
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Caption: FIGURE 1 Sample Blood Agar Plate
Caption: FIGURE 2 Microscopic Examination
TABLE 1 Control (Unused) Casino Gaming Chip Results Chip Surface Total # of Size Shape Color Margin # Colonies 1 Obverse 11 SM Round Yellow, gray Smooth Reverse 33 Edge 9 2 Obverse 15 SM Round Yellow, gray Smooth Reverse 15 Edge 16 3 Obverse 27 SM Round Yellow, gray Smooth Reverse 24 Edge 11 4 Obverse 12 SM Round Yellow, gray Smooth Reverse 12 Edge 10 5 Obverse 17 SM Round Yellow, gray Smooth Reverse 14 Edge 24 6 Obverse 19 SM Round Yellow, gray Smooth Reverse 17 Edge 29 7 Obverse 19 SM Round Yellow, gray Smooth Reverse 14 Edge 23 8 Obverse 27 SM Round Yellow, gray Smooth Reverse 22 Edge 22 9 Obverse 23 SM Round White, gray Smooth Reverse 8 Edge 17 10 Obverse 20 SM Round White, yellow Smooth Reverse 11 Edge 19 11 Obverse 22 MD, SM Round White Smooth Reverse 20 Edge 17 12 Obverse 11 SM Round White Smooth Reverse 25 Edge 10 13 Obverse 33 SM Round White Smooth Reverse 29 Edge 18 Chip Surface Elevation Total # of Total # of Gram # E. coli Coliforms Stain (+ or -) 1 Obverse Raised 0 0 N/A Reverse 0 0 + Edge 0 0 N/A 2 Obverse Raised 0 0 + Reverse 0 0 N/A Edge 0 0 N/A 3 Obverse Raised 0 0 N/A Reverse 0 0 N/A Edge 0 0 N/A 4 Obverse Raised 0 0 N/A Reverse 0 0 N/A Edge 0 0 N/A 5 Obverse Raised 0 0 N/A Reverse 0 0 N/A Edge 0 0 N/A 6 Obverse Raised 0 0 N/A Reverse 0 0 N/A Edge 0 0 N/A 7 Obverse Raised 0 0 N/A Reverse 0 0 N/A Edge 0 0 N/A 8 Obverse Raised 0 0 N/A Reverse 0 0 N/A Edge 0 0 N/A 9 Obverse Raised 0 0 N/A Reverse 0 0 N/A Edge 0 0 N/A 10 Obverse Raised 0 0 N/A Reverse 0 0 N/A Edge 0 0 N/A 11 Obverse Raised 0 0 + Reverse 0 0 + Edge 0 0 N/A 12 Obverse Raised 0 0 N/A Reverse 0 0 N/A Edge 0 0 N/A 13 Obverse Raised 0 0 N/A Reverse 0 0 N/A Edge 0 0 N/A Chip Surface Bacteria Isolated # of # Morphology Colonies Fungi (RNA Later) 1 Obverse N/A N/A 0 Reverse Bacillus 1 0 Edge N/A N/A 0 2 Obverse Bacillus 1 0 Reverse N/A N/A 0 Edge N/A N/A 0 3 Obverse N/A N/A 0 Reverse N/A N/A 0 Edge N/A N/A 0 4 Obverse N/A N/A 0 Reverse N/A N/A 0 Edge N/A N/A 0 5 Obverse N/A N/A 0 Reverse N/A N/A 0 Edge N/A N/A 0 6 Obverse N/A N/A 0 Reverse N/A N/A 0 Edge N/A N/A 0 7 Obverse N/A N/A 0 Reverse N/A N/A 0 Edge N/A N/A 0 8 Obverse N/A N/A 0 Reverse N/A N/A 0 Edge N/A N/A 0 9 Obverse N/A N/A 0 Reverse N/A N/A 0 Edge N/A N/A 0 10 Obverse N/A N/A 0 Reverse N/A N/A 0 Edge N/A N/A 0 11 Obverse Bacillus 1 0 Reverse Bacillus 1 0 Edge N/A N/A 0 12 Obverse N/A N/A 0 Reverse N/A N/A 0 Edge N/A N/A 0 13 Obverse N/A N/A 0 Reverse N/A N/A 0 Edge N/A N/A 0 TABLE 2 In-Use (Used) Casino Gaming Chip Results Chip Surface Total # of Size Shape Color Margin # Colonies 1 Obverse 5 SM Round Yellow, Smooth Reverse 10 gray Edge 8 2 Obverse 20 LG, Round White, Smooth, Reverse 8 MD, yellow, rigid Edge 11 SM gray 3 Obverse 19 MD, Round White, Smooth Reverse 27 SM yellow Edge 10 4 Obverse 16 LG, Round, White Smooth, Reverse 9 MD, rhizoid, rigid Edge 9 SM filamentous 5 Obverse 6 MD, Round Yellow, Smooth Reverse 12 SM gray Edge 9 6 Obverse 12 LG, Round White, Smooth, Reverse 10 MD, yellow, rigid Edge 10 SM gray 7 Obverse 21 MD Round White, Smooth Reverse 12 gray Edge 8 8 Obverse 8 LG, Round, White, Smooth, Reverse 8 MD, rhizoid yellow, rigid Edge 6 SM gray 9 Obverse 11 MD, Round Yellow, Smooth Reverse 10 SM gray Edge 8 10 Obverse 5 MD, Round Yellow, Smooth Reverse 2 SM gray Edge 1 11 Obverse 12 MD, Round White, Smooth Reverse 9 SM yellow, Edge 5 gray 12 Obverse 12 LG, Round, Yellow, Smooth, Reverse 7 MD rhizoid gray rigid Edge 7 13 Obverse 1 MD, Round White, Smooth Reverse 2 SM yellow, Edge 3 gray Chip Surface Elevation Total Total # of Gram # # of E. coli Coliforms Stain (+ or -) 1 Obverse Raised 15 0 N/A Reverse 5 0 N/A Edge 11 0 N/A 2 Obverse Raised 14 0 + Reverse 6 0 N/A Edge 5 0 N/A 3 Obverse Raised 4 0 N/A Reverse 1 0 N/A Edge 2 0 N/A 4 Obverse Raised, 4 0 N/A Reverse flat 2 0 - Edge 6 0 N/A 5 Obverse Raised 4 0 N/A Reverse 2 0 - Edge 5 0 N/A 6 Obverse Raised 4 0 + Reverse 8 0 N/A Edge 2 0 N/A 7 Obverse Raised 0 0 N/A Reverse 2 0 N/A Edge 3 0 N/A 8 Obverse Raised, 19 0 N/A Reverse flat 2 0 N/A Edge 3 0 - 9 Obverse Raised 7 0 N/A Reverse 3 0 N/A Edge 2 0 N/A 10 Obverse Raised 1 0 N/A Reverse 1 0 N/A Edge 2 0 N/A 11 Obverse Raised 11 0 - Reverse 0 0 N/A Edge 0 0 N/A 12 Obverse Raised, 0 N/A Reverse flat 0 + Edge 0 + 13 Obverse Raised 0 N/A Reverse 0 N/A Edge 3 0 N/A Chip Surface Bacteria Isolated # of # Morphology Colonies Fungi (RNA Later) 1 Obverse N/A N/A 0 Reverse N/A N/A 3 Edge N/A N/A 1 2 Obverse Bacillus 1 5 Reverse N/A N/A 1 Edge N/A N/A 0 3 Obverse N/A N/A 4 Reverse N/A N/A 4 Edge N/A N/A 2 4 Obverse N/A N/A 3 Reverse Bacillus 1 3 Edge N/A N/A 2 5 Obverse N/A N/A 3 Reverse Bacillus 1 5 Edge N/A N/A 4 6 Obverse Bacillus 1 3 Reverse N/A N/A 4 Edge N/A N/A 4 7 Obverse N/A N/A 10 Reverse N/A N/A 6 Edge N/A N/A 3 8 Obverse N/A N/A 2 Reverse N/A N/A 4 Edge Bacillus 1 3 9 Obverse N/A N/A 3 Reverse N/A N/A 2 Edge N/A N/A 2 10 Obverse N/A N/A 1 Reverse N/A N/A 2 Edge N/A N/A 1 11 Obverse Cocci 1 4 Reverse N/A N/A 3 Edge N/A N/A 2 12 Obverse N/A N/A 3 Reverse Bacillus 2 3 Edge Cocci 1 3 13 Obverse N/A N/A 1 Reverse N/A N/A 2 Edge N/A N/A 1 Note. We performed gram stain, bacterial morphology, isolated colonies, and fungi tests only on chips/petri dishes/colonies that were different. A lot of the colonies throughout the plates looked identical so we would isolate one of the colonies as a representation of the group. We isolated at least one colony out of all the colonies of the same group. SM = small; MD = medium; LG = large; N/A = not applicable.
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|Title Annotation:||ADVANCEMENT OF THE SCIENCE|
|Author:||Mc Keown, Edward G.|
|Publication:||Journal of Environmental Health|
|Article Type:||Cover story|
|Date:||Apr 13, 2019|
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