MRSA infections observed during anti-TNF treatment.

PARIS -- Methicillin-resistant Staphylococcus aureus infections have been reported for the first time in patients with rheumatoid arthritis being treated with tumor necrosis factor inhibitors.

In a poster presented at the annual European Congress of Rheumatology, Dr. Jack Lichtenstein noted that he had observed that several of his patients receiving tumor necrosis factor (TNF) inhibitors developed severe methicillin-resistant S. aureus (MRSA) infections, so he undertook a review of medical records of all patients in his clinical practice being treated with these drugs between August 2003 and July 2006 to determine the overall incidence and severity of these infections.

Among 430 patients receiving infliximab, etanercept, or adalimumab, 15 developed MRSA infections, had to stop TNF inhibitor therapy, and received intravenous antibiotics, reported Dr. Lichtenstein, a rheumatologist in group practice in Annapolis, Md. Additionally, 12 patients required hospitalization.

Concomitant immunosuppressive treatment included prednisone in 12 patients and methotrexate in 6.

Clinical presentations included cellulitis in six, osteomyelitis in three, sinusitis in two, and septic arthritis, mastitis, pneumonia, and Fournier's gangrene with sepsis in one each.

More than half of the infections occurred within the first 6 months of treatment, but four developed after more than a year of therapy. Six were seen in patients on infliximab, five in those on etanercept, and four in those on adalimumab.

Another 10 patients developed methicillin-sensitive S. aureus (MSSA) infections, 5 of whom had cellulitis, 4 septic arthritis, and 1 osteomyelitis. Seven of these required hospitalization, and nine were given intravenous antibiotics.

Other bacterial infections seen in anti-TNF-treated patients included gram-negative bacterial cellulitis in four, severe Clostridium difficile infections in three, and tuberculosis with fatal pneumonia, Mycobacterium marinum joint infection, and Nocardia pneumonia in one each. Other infections for which no bacterial agent was cultured included cellulitis in nine, pneumonia in six, and diverticulitis in two.

MRSA and MSSA infections were more common than were other bacterial infections in this group of anti-TNF-treated patients, according to Dr. Lichtenstein, who noted that MRSA infections may have a protracted course and may not respond to available treatments.

Attempts to restart TNF inhibitors after control of the MRSA infections led to recurrent infection in seven patients, and only two patients were able to resume TNF inhibitor therapy after the infection was controlled.

Based on these findings, Dr. Lichtenstein wrote that he would no longer continue the use of TNF inhibitors in patients with MRSA or MSSA infections.

Approximately one-third of Americans are carriers of MSSA and 0.8% carry MRSA, and infections with these organisms are expected to be common in immunocompromised patients such as these. However, baseline screening for MRSA carriage was not done in these patients.

This study was wholly funded by the investigators and had no pharmaceutical, institutional, or financial support.

BY NANCY WALSH

New York Bureau