Risk factors and clinical characteristics of patients with qnr-positive Klebsiella pneumoniae bacteraemia.

OBJECTIVES: Plasmid-mediated quinolone resistance (PMQR) caused by qnr genes has been known for 15 years. Information about global distribution and prevalence of qnr genes is abundant, but clinical information concerning infections produced by these isolates and risk factors for their acquisition is limited.
METHODS: Klebsiella pneumoniae blood isolates (n = 227) from a 1 year prospective cohort of patients in Taiwan were studied. MICs of quinolones were determined for all isolates, and multiplex PCR for the presence of PMQR genes and DNA gyrase mutations was applied to all 24 isolates with ciprofloxacin MICs ≥ 0.12 mg/L and a control group of 72 isolates with MICs ≤ 0.06 mg/L.
RESULTS: All qnr isolates were in the group with ciprofloxacin MICs ≥ 0.12 mg/L, constituting 9.4% of tested isolates and 3.9% (qnrB 2.6% and qnrS 1.3%) of total isolates. aac(6')-Ib-cr and qepA were not found. Risk factors for qnr included nosocomial infection, bedridden status, surgery within 3 months, non-K1/K2 serotypes and prior antimicrobial use. Ciprofloxacin MIC ≥ 0.12 mg/L was associated with prior quinolone use; in contrast, prior cephalosporin use was more closely linked to the presence of qnr. Fourteen-day mortality was similar in patients infected with qnr-positive versus qnr-negative isolates, but there was a trend for increased in-hospital mortality in patients infected with qnr-positive isolates.
CONCLUSIONS: In K. pneumoniae blood isolates collected at a hospital in Taiwan, the overall prevalence of qnr genes was 3.9%. Prior quinolone use was linked to increased ciprofloxacin MIC, but not with the prevalence of qnr, which was most strongly linked to exposure to other antimicrobials, especially cephalosporins.