2058. Prevalence of mup and qac genes in clinical and surveillance Methicillin-resistant Staphylococcus aureus (MRSA) isolates at two Military treatment facilities
Session: Poster Abstract Session: Antimicrobial Resistant Infections: Treatment
Saturday, October 29, 2016
Room: Poster Hall
Background: MRSA decolonization protocols are increasingly used in US hospitals. A concern therefore exists about emerging resistance to topical antibiotics and antiseptics. MupA and mupB genes are associated with high level resistance to mupirocin, while qacA and qacB genes are associated with resistance to chlorhexidine.

Methods: Using a multiplex PCR assay, we sought to determine the prevalence of mup and qac resistance genes in MRSA isolates collected at two US military treatment facilities over a period of 17 months. We also sought to determine the current baseline rates of these genes for future trending. In addition, we included 4 MRSA virulence and resistance genes that are routinely evaluated at our lab into the analysis. These include the sep gene (associated with MRSA bacteremia), pvl (encodes for the Panton-Valentine leucocidin toxin), etA (encodes for the exfoliative toxin A), and cfr (confers resistance to linezolid). 458 unique clinical and surveillance MRSA isolates were collected from 458 patients. The majority of isolates were clinical (n=435, 95.0%) versus 5% surveillance cultures.

Results: Overall, 25 of 458 isolates (5.5%) were positive for the mup gene. The monthly rate of mup-positive isolates ranged from 0 to 25% (3 of 12 total isolates) with a mean of 7.2%. We found only 3 positive qac isolates (0.6% overall prevalence). The monthly rate of qac-positive isolates ranged from 0-11.1% (1 of 9 total isolates) with a mean of 0.9%. The frequency of mup or qac positivity did not appear to increase over the course of the study period. 23 isolates carried the sep gene (5.0%). The majority of isolates (n= 305, 66.6%) carried the pvl gene. Cfr and etA genes were not detected in any of our isolates.

Conclusion: We found a slightly higher baseline prevalence of mupirocin resistance than previously reported rates in the US. However, similar to prior reports, the presence of qac gene was rare (0.6%). Rates of mup and qac positivity remained flat during the study period, although usage of both chlorhexidine and mupirocin increased in the spring 2014. These data provide a valuable frame of reference for trending emerging mupirocin or chlorhexidine resistance in this population.

Mackenzie Morgan, MD1, Emil Lesho, D.O., FIDSA2, Douglas Richesson, PhD3, Ana Ong, BS2, Rossalyn Maybank, BS2, Yoon Kwak, MS2, Michael Julius, PMP2, Mary Hinkle, M.D.2 and Patrick Mcgann, PhD2, (1)Walter Reed National Military Medical Center, Bethesda, MD, (2)Walter Reed Army Institute of Research, Silver Spring, MD, (3)Landstuhl Regional Medical Center, Landstuhl, Germany


M. Morgan, None

E. Lesho, None

D. Richesson, None

A. Ong, None

R. Maybank, None

Y. Kwak, None

M. Julius, None

M. Hinkle, None

P. Mcgann, None

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