title: Molecular epidemiology of acquisition of ceftazidime-resistant gram-negative bacilli in a nonoutbreak setting.
abstract: We prospectively studied the acquisition of ceftazidime-resistant gram-negative bacilli (CAZ-RGN) in two surgical intensive care units (SICU) during a nonoutbreak period. Surveillance cultures were obtained from patients at the time of admission and serially thereafter. CAZ-RGN isolates were typed by pulsed-field gel electrophoresis (PFGE). Three hundred and forty-three patients were enrolled from whom 1,621 baseline and follow-up cultures were obtained. The most common species isolated from patients were Pseudomonas aeruginosa (22), Enterobacter cloacae (21), Acinetobacter spp. (13), Enterobacter aerogenes (11), Citrobacter spp. (10), Pseudomonas spp. (non P. aeruginosa) (9), and Stenotrophomonas spp. (7). For each species, PFGE strain types were highly diverse; no single type was recovered from more than four patients. Twenty-eight patients acquired a CAZ-RGN during the SICU stay; in six (21%), emergence of resistance from a previously susceptible strain was documented on the basis of matching serial strain types. Transmission of CAZ-RGN between patients occurred but was infrequent, as judged by analyzing strain types of epidemiologically linked patients. In conclusion, colonization with CAZ-RGN in SICU was associated with diverse species and strains, as determined by molecular typing. Emergence of resistance from previously susceptible strains appeared to be more important than horizontal transmission in acquisition of CAZ-RGN in a nonoutbreak period.
authors.affiliation: Division of Infectious Diseases, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: E
authors.initials: E
authors.lastname: D'Agata
authors.forename: L
authors.initials: L
authors.lastname: Venkataraman
authors.forename: P
authors.initials: P
authors.lastname: DeGirolami
authors.forename: M
authors.initials: M
authors.lastname: Samore
mesh_terms: D000150:Acinetobacter / Q000187:drug effects; D002442:Ceftazidime / Q000494:pharmacology*; D018550:Cephalosporin Resistance; D002511:Cephalosporins / Q000494:pharmacology*; D015331:Cohort Studies; D016521:Electrophoresis, Gel, Pulsed-Field; D004755:Enterobacteriaceae / Q000187:drug effects; D006090:Gram-Negative Bacteria / Q000145:classification / Q000187:drug effects*; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology; D006801:Humans; D007362:Intensive Care Units; D011159:Population Surveillance; D011446:Prospective Studies; D011550:Pseudomonas aeruginosa / Q000187:drug effects
chemical_list: D002511:Cephalosporins; D002442:Ceftazidime