Mutations altering substrate specificity in OHIO-1, and SHV-1 family beta-lactamase.

The OHIO-1 beta-lactamase does not normally hydrolyse oxyimino-beta-lactam substrates like cefotaxime, ceftriaxone, ceftazidime or aztreonam. We were able to select spontaneous mutants of an OHIO-1-bearing strain of Escherichia coli using the antibiotic substrates listed above by enrichment methods of frequencies of 10(-8)-10(-10) for all antibiotics except ceftazidime (frequency less than 10(-10)). Most mutants with increased resistance to the other beta-lactams were also more resistant to ceftazidime.

OHIO-1 beta-lactamase is part of the SHV-1 family.

The OHIO-1 beta-lactamase gene was subcloned in a 1.16-kilobase TaqI fragment in the 2.4-kilobase chimeric plasmid pSK04.

The epidemiology of gentamicin-resistant Pseudomonas aeruginosa on an intermediate care unit.

The authors conducted a prospective six-month study of colonization by gentamicin-resistant Pseudomonas aeruginosa on an intermediate care unit at a Cleveland, Ohio hospital with the use of selective culture techniques, serotyping, and plasmid analysis. Thirty-five of 163 patients (21%) were culture positive at least once for gentamicin-resistant Pseudomonas aeruginosa. Patient samples, environmental cultures, and personnel hand cultures revealed no common source for the organisms.

Introduction of a plasmid encoding the OHIO-1 beta-lactamase to an intermediate care ward by patient transfer.

A prospective study of 147 intermediate care ward (ICW) patients for acquisition of gentamicin-resistant Enterobacteriaceae (GRE) was carried out. Fifty (34%) were colonized or infected with one or more strains of GRE. Fifteen of these patients and one nurse were colonized with 22 strains (including ten species) of GRE bearing identical 60 kb plasmids encoding a novel beta-lactamase determinant, OHIO-1 and ANT(2").