An Outbreak of Quinolone Resistant Haemphilus influenzae in a Long-Term Care Facility

Abstract & Commentary

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 Haemphilus influenzae in a long-term care facility: clinical and molecular epidemiology. Clin Infect Dis. 2004;38:1564-1569.

The clinical microbiology laboratory at a large teaching hospital in New York documented that in 2001, 35% of Haemphilus 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 whom 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.

Nazir et al performed 2 case-control studies. The first included all patients treated at the acute care hospital from whom 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 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 widely used for treatment of both community and nursing home acquired pneumonia. Therapy is often 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 2 major respiratory pathogens underscores the importance of monitoring the susceptibility patterns of clinical respiratory tract isolates, and the potential pitfalls of initiating quinolone monotherapy for treatment of pneumonia in the absence of appropriate culture and susceptibility data. Quinolones are frequently 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.


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 Section Editor, Hospital Epidemiology, Associate Editor of Infectious Disease Alert.