Use it or lose it: Empiric use spurs resistance

The case of the quinolone quandary

Synopsis: Ninety-three percent of sputum isolates from a single long-term care facility were resistant to quinolones. Epidemiologic study showed an association with prior receipt of levofloxacin. Strains were closely related by pulsed field gel electrophoresis (PFGE) analysis, indicating patient-to-patient spread of a resistant clone.

Source: Nazir J, et al. Quinolone resistant Haemophilus influenzae in a long-term care facility: Clinical and molecular epidemiology. Clin Infect Dis 2004; 38:1,564-1,569.

The clinical microbiology laboratory at a large teaching hospital in New York documented that in 2001, 35% of Haemophilus influenzae isolates were resistant to levofloxacin. Nazir and colleagues, therefore, reviewed the clinical records of all patients from whom levofloxacin-resistant H. influenzae (LRHI) had been isolated. All patients were residents of a single long-term care facility affiliated with the hospital. Further, all were residents of a single unit in the facility that provided long-term ventilator care. Of the 30 patients from the long-term care facility from which H. influenzae had been isolated, 28 (93%) had LRHI. Most of the patients from whom LRHI was isolated had some clinical evidence of infection at the time of isolation; 19 had fever, 16 had purulent tracheal secretions, and 7 had pulmonary infiltrates.

The researchers performed two case-control studies. The first included all patients treated at the acute care hospital from which LRHI was isolated. Residence at the nursing home in question (OR, 19.0; 95% CI, 1.3-287) and chronic obstructive pulmonary disease (OR, 24.5; 95% CI, 1.6-2797) were independently associated with isolation of LRHI. The second case control study included patients with LRHI treated at the long-term care facility. Only levofloxacin use (OR 3.0, 95% CI, 1.2-8.0) was associated with isolation of LRHI. PFGE analysis of LRHI showed all to be highly related. Although resistant to levofloxacin and multiple other quinolones, the isolates were susceptible to ampicillin, azithromycin, trimethoprim/sulfamethoxazole, and ceftriaxone.

Comment by Robert Muder, MD

Quinolone resistance among H. influenzae isolates has been very uncommon in the United States. The study by Nazir and colleagues demonstrates the occurrence of an outbreak of LRHI in a respiratory care unit of a long-term care facility. Both quinolone use and patient-to-patient spread appear to have been significant factors in the outbreak.

Quinolones are used widely for treatment of both community and nursing home-acquired pneumonia. Therapy often is empiric, particularly in the nursing home setting. There have been increasing numbers of reports of quinolone resistance among isolates of Streptococcus pneumoniae;1,2 increasing use of quinolones appears to be a significant factor.

The increase in quinolone resistance among isolates of two major respiratory pathogens underscores the importance of monitoring susceptibility patterns of clinical respiratory tract isolates, and the potential pitfalls of initiating quinolone mono-therapy for treatment of pneumonia in the absence of appropriate culture and susceptibility data.

Quinolones frequently are used as empiric therapy for nursing home-acquired pneumonia. Unfortunately, the nursing home setting is one in which the emergence and spread of antimicrobial resistance is particularly likely due to high frequency of antimicrobial use, prolonged patient stays, and less-than-optimal infection control practices.

References

1. Low DE. Quinolone resistance among pneumococci: Therapeutic and diagnostic implications. Clin Infect Dis 2004; 38(Suppl4):S357-362.

2. Chen DK, et al. Decreased susceptibility of Streptococcus pneumoniae to fluoroquinolones in Canada. Canadian Bacterial Surveillance Network. N Engl J Med 1999; 341:233-239.

Robert Muder, MD, Hospital Epidemiologist, Pittsburgh VA Medical Center Pittsburgh, is Associate Editor of Infectious Disease Alert.