Multiple antibiotic-resistant Klebsiella and Escherichia coli in nursing homes

Context infections caused by ceftazidime sodium-resistant gram-negative bac teria that harbor extended-spectrum beta-lactamases (ESBLs) are increasing in frequency in hospitals in the United States. Objectives To report a citywide nursing home-centered outbreak of infection s caused by ESBL-producing gram-negative bacilli and to describe the clinic al and molecular epidemiology of the outbreak. Design Hospital-based case-control study and a nursing home point-prevalenc e survey. Molecular epidemiological techniques were applied to resistant st rains. Settings A 400-bed tertiary care hospital and a community nursing home. Patients Patients who were infected and/or colonized with ceftazidime-resis tant Escherichia coli, Klebsiella pneumoniae, or both and controls who were admitted from nursing homes between November 1990 and July 1992, Main Outcome Measures Clinical and epidemiological factors associated with colonization or infection by ceftazidime-resistant E coli or K pneumoniae; molecular genetic characteristics of plasmid-mediated ceftazidime resistanc e. Results Between November 1990 and October 1992, 55 hospital patients infect ed or colonized with ceftazidime-resistant E coli, K pneumoniae, or both we re identified. Of the 35 admitted from 8 nursing homes, 31 harbored the res istant strain on admission. All strains were resistant to ceftazidime, gent amicin, and tobramycin; 96% were resistant to trimethoprim-sulfamethoxazole and 41% to ciprofloxacin hydrochloride, In a case-control study, 24 nursin g home patients colonized with resistant strains on hospital admission were compared with 16 nursing home patients who were not colonized on hospital admission; independent risk factors for colonization included poor function al level, presence of a gastrostomy tube or decubitus ulcers, and prior rec eipt of ciprofloxacin and/or trimethoprim-sulfamethoxazole. In a nursing ho me point-prevalence survey, 18 of 39 patients were colonized with ceftazidi me-resistant E coli; prior receipt of ciprofloxacin or trimethoprim-sulfame thoxazole and presence of a gastrostomy tube were independent predictors of resistance. Plasmid studies on isolates from 20 hospital and nursing home patients revealed that 17 had a common 54-kilobase plasmid, which conferred ceftazidime resistance via the ESBL TEM-10, and mediated resistance to tri methoprim-sulfamethoxazole, gentamicin, and tobramycin; all 20 isolates har bored this ESBL. Molecular fingerprinting showed 7 different strain types o f resistant K pneumoniae and E coli distributed among the nursing homes. Conclusions Nursing home patients may be an important reservoir of ESBL-con taining multiple antibiotic-resistant E coli and K pneumoniae. Widespread d issemination of a predominant antibiotic resistance plasmid has occurred. U se of broad-spectrum oral antibiotics and probably poor infection control p ractices may facilitate spread of this plasmid-mediated resistance. Nursing homes should monitor and control antibiotic use and regularly survey antib iotic resistance patterns among pathogens.