NFL Infectious Disease News – January 2014 Duke Infection Control Outreach Network (DICON) Volume 5, Number 1
The Changing Epidemiology of Staphylococcus aureus: Recent Trends in Antibiotic
The antimicrobial susceptibility of S. aureus began to change soon after penicillin was discovered in the early 1940’s. Although some staphylococci had become resistant to penicillin by the early 1950’s, methicillin-resistant staphylococci did not become widespread and common in the United States until the 1980’s. The proportion of staphylococci that were methicillin-resistant steadily increased for the next 25 years. By 2000, many strains of S. aureus causing infections in the community were also methicillin resistant. Recent changes in the susceptibility of S. aureus will be the focus of this newsletter. Although our previous treatment recommendations have not changed as a result of the information we discuss, we believe that NFL team medical personnel should be aware of the following 4 recent changes in the susceptibility or epidemiology of staphylococci as they may impact their treatment and assessment of players who develop staphylococcal infections in the future. Previously rare, penicillin-susceptible S. aureus (PSSA) may be making a “comeback” in the United States. Two recent reports by investigators from medical centers in New York and California showed that 15-20% of isolates of S. aureus from blood or ICU patients were PSSA (1-2). In one of these studies the incidence of PSSA increased from 5% in 2004 to 15% in 2012 (1). Recognition of this phenomenon was delayed because most laboratories stopped testing penicillin susceptibility of S. aureus isolates. Such testing requires two steps to produce a valid result. First, routine MIC testing has to show susceptibility to penicillin. Then, a second test for β-lactamase production must be done. The preceding reports have prompted us to ask our local laboratories to resume penicillin testing of all methicillin-sensitive S. aureus clinical isolates. This is important because the drug of choice of patients with infections due to PSSA is penicillin, as it is remarkably more active than other agents. Because of the preceding trends we advise NFL medical personnel to request penicillin testing for all strains of methicillin susceptible S. aureus isolated from NFL players. Strains of S. aureus that are resistant to Linezolid have recently been detected. Linezolid (Zyvox) is an antibiotic that normally has good activity against MRSA. We recently encountered a patient with recurrent boils who was infected with a strain of MRSA that was resistant to linezolid. Although this was an isolated case, we were concerned because linezolid-resistant MRSA have been recently reported by investigators in the United States and Europe. The mechanism of this resistance is known to be due to a single mutation on a plasmid (which has the unfortunate ability and tendency to “jump” from one strain of S. aureus to another). So far, linezolid resistance appears to be extremely rare, but a recent report of an outbreak of linezolid-resistant strain of MRSA involving 12 patients in an ICU in Spain alarmed epidemiologists in the United States and Europe (3). Because such strains are rare we do not advise making any changes in our previous recommendations concerning the use of linezolid in players with MRSA infections. This recommendation, however, may change if such resistance becomes more common in the future. Daptomycin-resistant strains of MRSA are increasing in frequency. Daptomycin is an intravenous antibiotic that normally has excellent activity against MRSA. This drug is the most common alternative for treatment of patients with serious MRSA infections who cannot tolerate Vancomycin. Daptomycin- resistant MRSA infections appear to be increasing in frequency in multiple locations in the United States (4). This resistance is particularly likely to occur in patients with bone or complicated blood or deep- seated staphylococcal infections who are treated with prolonged courses of daptomycin. We believe that doctors who use daptomycin to treat complicated MRSA infections for prolonged periods should be aware of the risk of treatment failure due to the emergence of daptomycin resistance. The treating physicians must ensure that daptomycin-susceptibility has been tested by their microbiology lab. Although the incidence of MRSA infections has declined in American hospitals during the past 6 years, the incidence of community-acquired MRSA infections has remained unchanged. A recent study showed that the incidence of invasive hospital-acquired and healthcare-associated MRSA infections declined by 54 and 28% respectively from 2005-2011 in 9 urban areas in the United States (5). Unfortunately, the incidence of invasive community-acquired MRSA declined by a minimal amount (5%) during the same time span. We believe this information is relevant to NFL medical personnel in two respects: First, the risk of NFL players developing community-onset MRSA infections has changed little in the past 6 years. However, the risk of NFL players acquiring MRSA infections while hospitalized for surgery or other injuries has declined by over 50%.In view of the fact that the incidence of community-acquired MRSA infections has not declined, we advise NFL medical personnel to continue to obtain cultures from all players with cutaneous abscesses, initiate empiric therapy with activity against MRSA until susceptibility test results return, and follow the recommendations about prevention and control outlined in our previous newsletters. References
1. Crane JK Resurgence of penicillin-susceptible Staphylococcus aureus at a hospital in New York
State, USA J Antimicrob Chemother 2013; doi: 10.1093/jac/dkt 317
2. Goodman J Penicillin-susceptible Staphylococcus aureus (PSSA) infection in an era of multidrug
resistance Poster #169 ID Week Annual IDSA Meeting, San Francisco October 18, 2012.
3. Morales G, Picazo JJ, Baos E et al Resistance to linezolid is mediated by the cfr gene in the first
report of an outbreak of linezolid-resistant Staphylococcus aureus. Clin Infect Dis 2010; 50: 821-5.
4. Gasch O, Camoez M, Domingues MA et al Emergence of resistance to daptomycin in a cohort of
patients with methicillin-resistant Staphylococcus aureus persistent bacteremia treated with daptomycin J Antimicrob Chemother 2013; dos: 10.1093/jac/dkt396.
5. Dantes R, Mu Y, Bellflower R et al National burden of invasive methicillin-resistant
Staphylococcus aureus infections, United States 2011. JAMA Intern Med 2013; 173:1970-8.
Daniel J. Sexton, MD Deverick J. Anderson, MD, MPH Professor of Medicine Associate Professor of Medicine Division of Infectious Diseases Division of Infectious Diseases Medical Director Co-Medical Director Duke Infection Control Outreach Network Duke Infection Control Outreach Network Duke University Medical Center Duke University Medical Center
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NFL Infectious Disease News – January 2014 
MRSA infections. This recommendation, however, may change if such resistance becomes more common