WASHINGTON — Quebec's recent outbreak of Clostridium difficile-associated diarrhea does not appear to have been associated with any specific antibiotic use pattern. Rather, poor infection control practices are likely to blame.
That was the conclusion of an analysis from four Canadian hospitals conducted by Dr. Karl A. Weiss and his associates at Maisonneuve-Rosemont Hospital, Montreal, and reported in a poster at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
The outbreak of C. difficile-associated diarrhea (CDAD), which occurred in 2002–2004 at several Quebec hospitals, was caused by a new strain of C. difficile found to be more virulent than those previously seen (N. Engl. J. Med. 2005;353:2442–9).
Although antibiotic usage has been strongly associated with the occurrence of CDAD, the circumstances of this outbreak were at odds with that explanation: No increase in CDAD cases was seen in any province other than Quebec, which actually has the lowest per capita antibiotic consumption of all the Canadian provinces.
The investigators analyzed antibiotic use data for the time periods 1999–2001, 2002, and 2003 from two hospitals that were affected by the new C. difficile strain outbreak and two that were not. In one of the affected hospitals, the number of CD diagnoses per 1,000 population rose from 9 in 1999–2001 to 14 in 2002 to 33 in 2003. In contrast, rates in one of the unaffected hospitals remained stable, from 5/1,000 in 1999–2001 to 4 in 2002 to 5.5 in 2003.
A comparison of affected and unaffected hospitals showed no significant association between the number of CDAD cases per 1,000 admissions and the daily consumption of cephalosporins, carbapenems, β-lactams/β-lactamase inhibitors, fluoroquinolones, or intravenous clindamycin. There was no significant protective effect from any class of antibiotics, Dr. Weiss and his associates reported at the meeting, sponsored by the American Society for Microbiology.
Proper antibiotic use is key to controlling the emergence of resistant organisms, but in the case of CDAD antibiotics appear to be acting mainly as triggering agents in patients who acquire the new strain during their hospital stay.
Instead, the Quebec outbreak appeared to be mostly caused by poor infection control practices. The situation improved dramatically in 2004–2005 following substantial investment by the provincial government and the implementation of infection control measures.