Community-associated methicillin-resistant Staphylococcus aureus and athletes

Toxigenic profile of methicillin-sensitive and resistant Staphylococcus aureus isolated from special groups

Background

Staphylococcus aureus is characterized by its pathogenicity and high prevalence, causing disease in both healthy and immunocompromised individuals due to its easy dissemination. This fact is aggravated by the widespread dissemination of S. aureus carrying toxigenic genes. The objective of this study was to determine the toxigenic profile of methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) in patients with purulent skin and/or soft tissue infections seen at the Dermatology Department of the University Hospital of the Botucatu Medical School, asymptomatic adults older than 60 years living in nursing homes, and prison inmates of the Avaré Detention Center.

Methods

PCR was used for the detection of the mecA gene, enterotoxin genes (sea, seb, and sec), exfoliative toxins A and B (eta and etb), toxic shock syndrome toxin 1 (tst), panton–valentine leukocidin (lukS-PV and lukF-PV), and alpha- and delta-hemolysins or cytotoxins (hla and hld).

Results

The results showed a significant prevalence of toxigenic genes among S. aureus isolates from asymptomatic individuals, with the observation of a higher prevalence of cytotoxin genes. However, the panton–valentine leukocidin gene was only detected in MSSA isolated from patients with skin infections and the tst gene was exclusively found in MSSA isolated from prison inmates.

Conclusions

The present study demonstrated a significant prevalence of toxigenic genes in MSSA and MRSA strains isolated from asymptomatic S. aureus carriers. There was a higher prevalence of cytotoxin genes.

Community-associated methicillin-resistant Staphylococcus aureus case studies

Over the past decade, the emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has changed the landscape of S. aureus infections around the globe. Initially recognized for its ability to cause disease in young and healthy individuals without healthcare exposures as well as for its distinct genotype and phenotype, this original description no longer fully encompasses the diversity of CA-MRSA as it continues to expand its niche. Using four case studies, we highlight a wide range of the clinical presentations and challenges of CA-MRSA. Based on these cases we further explore the globally polygenetic background of CA-MRSA with a special emphasis on generally less characterized populations.

Will there ever be a universal Staphylococcus aureus vaccine?

Developing a universal vaccine for S. aureus is a top priority but to date we have only had failures in human clinical trials. Given the plethora of bacterial virulence factors, broad range of the health of humans at-risk for infections, lack of any information regarding immune effectors mediating protection for any manifestation of S. aureus infection and overall competence of this organism as a colonizer, commensal and pathogen, we may just simply have to accept the fact that we will not get a universal vaccine. Antigenic variation is a major challenge for some vaccine targets and for many conserved targets the organism can easily decrease or even eliminate expression to avoid immune effectors without compromise to infectivity and ability to cause disease. Studies of human immune responses similarly have been unable to identify any clear mediators of immunity and data from such studies can only eliminate those found not to be associated with protection or that might serve as a marker for individuals with a higher level of resistance to infection. Animal studies are not predictive of success in humans and unlikely will be except in hindsight if and when we develop an efficacious vaccine. Successful vaccines for other bacteria based on capsular polysaccharides have not worked to date for S. aureus, and laboratory studies combining antibody to the major capsular serotypes and the other S. aureus surface polysaccharide, poly-N-acetyl glucosamine, unexpectedly showed interference not augmentation of immunity. Potential pathways toward vaccine development do exist but for the foreseeable future will be based on empiric approaches derived from laboratory-based in vitro and animal tests and not on inducing a known immune effector that predicts human resistance to infection.

Surveillance of Physician-Diagnosed Skin and Soft Tissue Infections Consistent With Methicillin-Resistant Staphylococcus aureus (MRSA) Among Nebraska High School Athletes, 2008–2012

Though historically confined to hospital settings, methicillin-resistant Staphylococcus aureus (MRSA) has received increasing attention in the wider community, particularly among athletes. A 2007–2008 investigation in Nebraska concluded that MRSA skin infections were an emerging problem among the state’s student athletes. Statewide surveillance was subsequently conducted during 4 school years (2008–2012) to estimate incidence of skin and soft tissue infections (SSTI) consistent with MRSA among student athletes. High school athletic officials completed Internet-based surveys following winter and fall sport seasons. Over 3 school years, incidence estimates per 10,000 athletes decreased substantially from 20.9 (2008–2009) to 11.3 (2010–2011) among football players and from 60.8 (2008–2009) to 28.1 (2010–2011) among wrestlers. Following the 2011–2012 sport seasons, however, incidence estimates increased to 16.6 per 10,000 football players and 43.3 per 10,000 wrestlers. School nurses should support school officials to prioritize prevention and control efforts for SSTI, including MRSA.