CA-MRSA Infections Research Articles

Outbreaks of Infection Caused by Community‐Acquired Methicillin‐Resistant Staphylococcus aureus in a Canadian Correctional Facility

Methicillin-resistant Staphylococcus aureus (MRSA) has been identified in prison settings in the United States. The present study investigated two clusters of skin and soft tissue infection caused by community-acquired (CA) MRSA in a correctional facility in southern Ontario. Outbreak investigations were conducted by the responsible public health authority. Strain relatedness was assessed through comparison of pulsed-field gel electrophoresis and antibiograms. Two distinct outbreaks of CAMRSA-associated disease occurred in 2002 and 2004. Most patients presented with abscesses in the lower extremities. All isolates had identical DNA banding patterns on pulsed-field gel electrophoresis. One-half of the affected inmates resided in a cellblock with one other affected inmate. No other risk factors were identified. One of the first outbreaks of CAMRSA infections in a correctional facility in Canada is documented. Taken in conjunction with outbreaks elsewhere, this suggests that residence in correctional facilities may be a risk factor for CAMRSA infection.

How to prevent transmission of MRSA in the open community?

In the past 20 to 30 years, methicillin-resistant Staphylococcus aureus (MRSA) strains have been present in hospitals and have become a major cause of hospital-acquired infection. Methicillin resistance rates of S. aureus vary considerably between countries, with a high prevalence in the United States, and southern Europe (>20%) and a low prevalence in northern Europe (< or =5%). Community-acquired MRSA emerged worldwide in the late 1990s. There has been great confusion in the literature between healthcare-associated MRSA infections occurring in the community in patients who are at risk of acquiring hospital MRSA (such as those with past history of hospital admission, immunocompromised status, etc.), and true CA-MRSA infections due to strains that are present in the community only.

Severe Staphylococcus aureus infections caused by clonally related community-acquired methicillin-susceptible and methicillin-resistant isolates.

We investigated the genetic relatedness of 5 community-acquired (CA) Staphylococcus aureus isolates obtained from 4 consecutive pediatric patients presenting with sepsis syndrome and severe pneumonia during a 3-week period in 2000. Two patients were infected with methicillin-susceptible S. aureus (MSSA), and 2 were infected with methicillin-resistant S. aureus (MRSA). The pulsed-field gel electrophoresis patterns for the 2 CA-MRSA isolates were identical to each other, as were the patterns for the 3 CA-MSSA isolates. A 2-band difference reflecting the presence of a staphylococcal cassette chromosome mec (SCCmec) element distinguished the CA-MRSA isolates from the CA-MSSA isolates. The small, mobile type IV SCCmec element was present in the CA-MRSA isolates. These data suggest that an insertion or, less likely, a deletion of the SCCmec type IV element occurred in a highly virulent S. aureus background. Staphylococcal toxin genes sea, seh, lukS-PV, and lukF-PV were detected in all isolates. Also, in all isolates, was a partial homolog of seo (seo'). The relationship among these patient isolates strengthens the assumption that CA-MRSA infections may be caused by isolates closely related to MSSA isolates.

Staphylococcal resistance revisited: community-acquired methicillin resistant Staphylococcus aureus--an emerging problem for the management of skin and soft tissue infections.

In the community non-localized or deep staphylococcal skin and soft tissue infections are typically managed with beta-lactamase stable penicillins. The aims of this review are (1) to evaluate the evidence for the emergence of new strains of community-acquired methicillin resistant Staphylococcus aureus (MRSA), (2) to identify the reasons for their significant association with cutaneous infections, and (3) to consider how they arose and how big a threat they pose to the management of such infections outside hospitals. MRSA are emerging as significant community pathogens, especially in previously healthy children with no recognizable risk factors, and are predominantly associated with skin and soft tissue infections (especially abscesses and cellulitis). When present, risk factors are generally similar to those for infection with methicillin susceptible S. aureus. The MRSA isolates associated with such infections may not be entirely 'new', but could represent the displacement of some hospital clones (e.g. EMRSA-15 or variants thereof) to the community as well as the de-novo generation of novel MRSA clones by multiple horizontal transmissions of the mecA gene into methicillin susceptible S. aureus with different genetic backgrounds, some of which are already circulating globally. Community-acquired MRSA from diverse locations are non multiresistant and almost always contain the novel type IV SCCmec commonly found in coagulase-negative staphylococci, but also in hospital-associated gentamicin susceptible MRSA from France, the paediatric clone and in EMRSA-15. More local data on CA-MRSA infections are needed so that dermatologists and community physicians can assess the risk of such infections amongst their patients and avoid the inappropriate administration of beta-lactams. No simple change in prescribing practices will entirely alleviate selective pressure for the spread of community-acquired MRSA and not exacerbate resistance in pyogenic streptococci, commonly found together with S. aureus in skin and soft tissue infections. The importance of hygiene in preventing the spread of community-acquired MRSA in the community must be reemphasized.