Normal microbial flora of YCP students

We are currently examining the normal microbial flora in BIO230 labs this month, with focus on skin carriage of Staphylococcus and characterization of specific species. I had stated in class that our samples (minus any personally identifying information) would be analyzed for epidemiologic trends for carriage among student populations, and that this project has been ongoing for about 5 years now.

The current Biology major working on this project, Corrine Cusick (YCP Bio Class of 2012,) was kind enough to share her data with me to summarize here so that the BIO230 students might be able to better understand the big picture of the project and how they fit into it. The graphic to the right represents data collected from the entire United States, and shows how a variety of S. aureus infections in health care settings have been increasing over the past decade, presenting a growing concern and challenge for health care workers.

Corrine’s project examined a new cohort of YCP students (Fall 2010/Spring 2011)  with nasal and skin-isolated samples grown in M-Staph broth to promote the enrichment of Staphylococcus. Samples were then streaked onto Mannitol Salts Agar, in order to identify putative colonies of S. aureus by their ability to ferment mannitol. Each student sample was then examined by the coagulase test to confirm the presence of S. aureus in the sample, and for expression of the antimicrobial resistance gene beta-lactamase.  These isolates were then correlated with reported student usage of gym facilities, and with working in a health care setting.  She then compared this data with similar datasets collected from the Fall 2007 term forward.

Prevalence of S. aureus and beta-lactamase expressing S. aureus among YCP students, 2007 to 2011 HC/NHC = Health care/non-health care workers G/NG = Gym/non-gym use

Corrine’s full data set is shown here. As can be seen, there are gender differences in carriage of coagulase-positive S. aureus (%coag), with males showing a statistically significant difference from females, however the differences between genders for beta-lactamase expressing S. aureus was not statistically significant. Frequent gym use did not seem to be significant for either carriage of coagulase-positive SA, or for beta-lactamase positive SA, with no statistic difference in gender pooled groups. Health-care association however did demonstrate a significant risk factor for carrying beta-lactamase positive SA, with students who reported working in any health-care facility showing up to 50% higher carriage rates of antibiotic resistant SA isolates on their skin.

Corrine’s most significant conclusion follows that latter finding; overall in YCP student populations student carriage of coagulase-positive Staphylococcus aureus was within normally reported levels found nationwide, however these isolates were also positive of beta lactamase up to 47% of the time, which is significantly higher than the national average. The collected data on YCP students suggests that community acquired SA should be continued to be monitored.

The take home message is this: emergence of antibiotic resistant isolates of nosocomially-acquired infections continues to rise, and presents a tremendous problem for health care. Awareness of the presence of these organisms on our bodies, and active prevention of transmission to susceptible individuals will offer us the best opportunity to help our patients, and speed their recovery times.


About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on April 16, 2012, in Danger danger danger!, Microbes in the News and tagged , , , . Bookmark the permalink. 2 Comments.

  1. There is a full experimental lab report on how hospitals and/or specific units in a hospital could potentially solve this problem, published by the Oxford Journals in February 2003, on the use of routine cycling of antimicrobial agents to aid in infection control. The full report can be found here: Cycling refers to, “The deliberate, scheduled removal and substitution of specific antimicrobials or classes of antimicrobials within an institutional environment (either hospital-wide or confined to specific units) to avoid or reverse the development of antimicrobial resistance.”

    This lab report is over 9 years old, but I believe it gives us some type of insight on how we could potentially achieve infection control. As the report also states, this topic isn’t widely addressed by many researchers, as there still remains insufficient evidence on whether or not cycling has any positive inpact on infection control in regards to this specific concern.

    • Those chemotherapeutics from that article are for in vivo patient treatment, as opposed to control in an environmental setting. Cycling of antibiotics does help to prevent acquisition of resistance in an infection, but does not help with organisms on fomites, where chemical methods of control are needed.

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