Staphylococcus aureus is a bacterium commonly associated with the normal human microbiome, a commensal and symbiotic collection of bacteria that inhabit our body. In particular, S. aureus can reside harmlessly on skin and in the nose. However, with the growing prevalence of antibiotic resistance in bacteria overall, a subpopulation of healthy individuals can also carry or be colonized with MRSA strains. MRSA, which stands for methicillin-resistant Staphylococcus aureus, is a drug-resistant variant S. aureus that is not only resistant to penicillins and other related antibiotics, but can also be resistant to other commonly used drug classes such as tetracyclines, quinolones and aminoglycosides. According to the Centers for Disease Control, in 2011, there were about 16,500 cases of community-acquired MRSA infections in two percent of the U.S. population is nasally colonized with MRSA.
In recent news, a third player from the Tampa Bay Buccaneers, cornerback Johnthan Banks, was diagnosed with a MRSA infection. A few months earlier in August, two other Tampa Bay players, guard Carl Nicks and kicker Lawrence Tynes, were treated for MRSA infections. According to an infectious disease expert who had been called in to assess the situation in August, Nicks and Tynes. MRSA infections were caused by different MRSA strains, suggesting that these infections were not related. It remains to be determined whether Banks infection is connected to either of the earlier infections. Nevertheless, the League is taking no chances and has sanitized all Tampa Bay player facilities and has boosted efforts to educate players and staff on methods for preventing spread of infections, both after the two infections in August and the more recent case in October.
The Buccaneers MRSA scare is just the latest in a number of MRSA outbreaks associated with NFL teams, which include the St. Louis Rams, Cleveland Browns, Washington Redskins and San Francisco 49ers. Notably, in the 2003 football season, five out of the 58 St. Louis Rams players became infected with a single MRSA clone within a span of three months (Kazakova SV, 2005). The CDC conducted a retrospective study and found that skin abrasions, or turf burns, were associated with all the MRSA skin abscesses in infected players; concluding that not only were the abrasions entry points for MRSA, but because they typically occur in areas not covered by the uniform, once infected, these lesions became a source for contact transmissions. In fact, infections only occurred in linemen and linebackers, and avoided players in the backfield positions, providing further evidence that this outbreak was likely caused through skin to skin contact. Other behaviors, such as sharing towels, gym equipment and Jacuzzis could also have contributed to spread of infection among team members. Of note, the study also uncovered that on average, players received ten times the number of antibiotics prescribed to the general public, which can lead to a local environment where drug-resistant pathogens, like MRSA, can thrive. In order to better understand the risk factors associated with MRSA infections in the NFL, the League has started a study to examine the prevalence and outcome of MRSA infections associated with synthetic turf grass systems. It is likely however, that many NFL MRSA infections are acquired outside the team training facilities, as was the case with Washington Redskin Brandon Noble, whose recurring MRSA infection was caused by surgery for an injured knee. Likewise, given that the two initial MRSA infections were due to distinct strains, the MRSA infections plaguing the Buccaneers are probably isolated incidents caused by infections acquired in the community. The various etiologies associated with MRSA infections in NFL players only highlights all the factors that can put them at risk for acquiring these severe infections.
MRSA infections are more commonly acquired in the hospital-setting, where the combination of sick/immunocompromised patients with the high probability of drug resistance among nosocomial pathogens (e.g. MRSA) can lead to a higher incidence of drug-resistant infection. Even though MRSA strains acquired in the community can be more virulent than those acquired in the hospital, they are nevertheless more susceptible to oral therapies and can often be treated in the outpatient setting. But as patients move in and out of hospital care, all the while carrying community and/or hospital MRSA strains with them, the distinction between community- and hospital-acquired MRSA infections is starting to blur. As a result, most infections positive for MRSA that are severe enough to require hospitalization are treated similarly; empirically with intravenous (IV) vancomycin, then patients are switched to narrow-spectrum anti-MRSA agents such as IV/oral linezolid (Pfizer's Zyvox/Zyvoxid) or IV daptomycin (Cubist/Novartis/Merck's Cubicin) once a diagnosis of MRSA is confirmed.
As hospitals aim to contain costs associated with prolonged hospitalization, anti-MRSA antibiotics that reduce days of therapy or allow patients to be discharged from the hospital sooner are highly desired. The commercial success of linezolid, which is available in IV and oral formulations, highlights the utility of oral formulation in the treatment of MRSA infections. We forecast that within the next ten years, as many as four new antibiotics with both IV and oral formulations will launch (Cubist's tedizolid, Melinta's delafloxacin, Tetraphase's eravacycline and Nabriva's BC-3781), which will provide physicians with additional therapeutic options for IV-oral step-down therapy and early hospital discharge. Notably, Cubist's tedizolid, which like linezolid belongs to the oxazolidinone class, is poised for commercial success due to its once-daily dosing and its potential to cure MRSA skin infections in fewer days than linezolid (seven vs. ten days). We expect that the majority of these new agents will be approved for the treatment of complicated skin and skin structure infections, which along with community-acquired pneumonia, is one of the more common community-acquired infections where MRSA is a common pathogen.
Overall, the re-emergence of high-profile MRSA infections has increased the public's awareness of MRSA and the threat of highly drug-resistant bacterial pathogens. In addition, it emphasizes that even healthy individuals, including ones at the peak of physical fitness, are susceptible to severe infections. Yet similar to infection prevention strategies implemented in hospitals, good hygiene can go a long way to preventing infection and spread of MRSA in NFL locker rooms. As a result, the NFL has taken several steps towards helping reduce outbreaks like the one in St. Louis, such as constant circulation of clean towels and maintaining clean and dry dressing over skin abrasions. In addition, NFL staff and players are continually educated on proper hand hygiene, with hand sanitizer dispensers located throughout common areas in training facilities. For non-NFL players such as the rest of us, simple hand washing, immediate cleaning and covering of open wounds and avoiding getting tackled by NFL linebackers would be good places to start.
Maria Ascano is a business insights analyst with the Infectious Disease team at Decision Resources.
Kazakova SV, et al. A clone of methicillin-resistant Staphylococcus aureus among professional football players. N Engl J Med. 2005;352:468-475.