Community-Onset MRSA May Be Less Obvious Than in the Hospital

April 22, 2004

Andrew Bowser

April 22, 2004 (Philadelphia) — Outside of the hospital, presence of healthcare-associated risk factors such as chronic illness may be of little value in distinguishing methicillin-resistant Staphylococcus aureus (MRSA) infection from methicillin-sensitive S. aureus (MSSA), suggest findings of a study presented here at the annual scientific meeting of the Society of Healthcare Epidemiology of America.

In children presenting for care at an urban tertiary care center's emergency room or affiliated clinics, MRSA was not significantly more common in those with chronic illness, medical devices, or a history of hospitalization — the risk factors commonly associated with MRSA acquired in a healthcare setting, according to Susan Coffin, MD, MPH, medical director of infection prevention and control at Children's Hospital of Philadelphia in Pennsylvania.

"We set out to get the clinician's perspective…[on] children that come in for healthcare that are not hospitalized," Dr. Coffin told Medscape. "We found…the presence of a healthcare-associated risk factor does not appear to help clinicians discriminate between patients who do and do not have MRSA."

Incidence of community-acquired MRSA "more than doubled" during that same time period in children presenting with S. aureus soft tissue infections, she added.

Together, these findings suggest that all community-acquired S. aureus infections should be considered suspect, at least in areas where community-acquired MRSA is on the rise. "Clinicians seeing children with suspected S. aureus infections need to be aware [that those infections] may be caused by a resistant organism," said Dr. Coffin, who suggested several potential "changes in clinical practice" based on these findings.

In particular, S. aureus infections should be cultured to determine whether they are caused by MRSA; drainage should be attempted more frequently, because a "significant proportion" of skin and soft tissue infections may resolve with drainage alone, Dr. Coffin said. Finally, clinicians should ask patients to come back for reexamination more frequently to assess their clinical response to therapy, and instruct patients to return more promptly if their infection worsens.

In a case-control study, Dr. Coffin and coinvestigators identified 447 cases of community-acquired MRSA between 2001 and 2003. Of that group, 134 cases (30%) of infections were due to MRSA. There was no change over time in incidence of MRSA in invasive infections; however, MRSA incidence rose sharply in children with soft tissue S. aureus infections, from less than 20% in 2001 to nearly 50% in 2003, although the investigators qualified this finding by the risk of possible referral bias or other factors.

There were no significant differences between the MRSA and MSSA groups in the presence of chronic illness (43% vs. 54%; P = .09), a medical device (20% vs. 29%; P = .14), or a history of hospitalization (51% vs. 60%; P = .16).

These findings bolster preliminary reports that suggesting an increase "in certain geographic pockets" in incidence of children without healthcare-associated risk factors presenting with infections due to MRSA, Dr. Coffin told Medscape.

A "significant percentage" of MRSA isolates were resistant to antibiotics other than penicillin-related drugs, "so they look more similar to the healthcare-associated MRSA strains," Dr. Coffin told Medscape. "Initially, community-onset MRSA was recognized as having unique antibiotic susceptibility patterns [and] were resistant almost exclusively to penicillin-related drugs."

Other recent reports on community-acquired MRSA also suggest antibiotic susceptibility patterns similar to that seen in the healthcare setting, she added.

The authors reported no commercial relationships relevant to the study.

SHEA 14th Annual Scientific Meeting: Abstract 164. Presented April 18, 2004.

Reviewed by Gary D. Vogin, MD

Andrew Bowser is a freelance writer for Medscape.

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