Survey of Plasmid-Associated Genetic Markers in Enterobacteriaceae with Reduced Susceptibilities to Cephalosporins
Autor: | Eileen M. Graffunder, Ann M. Evans, Richard A. Venezia, Karen E. Preston |
---|---|
Rok vydání: | 2003 |
Předmět: |
Adult
Genetic Markers Klebsiella pneumoniae medicine.drug_class Cephalosporin Microbiology Plasmid Enterobacteriaceae Mechanisms of Resistance Genotype polycyclic compounds medicine Humans Pharmacology (medical) Cloning Molecular Antibacterial agent Pharmacology Genetics Cephalosporin Resistance biology Incidence Enterobacteriaceae Infections biochemical phenomena metabolism and nutrition bacterial infections and mycoses biology.organism_classification Transformation (genetics) Phenotype Infectious Diseases Genetic marker bacteria Seasons Transformation Bacterial Plasmids |
Zdroj: | Antimicrobial Agents and Chemotherapy. 47:2179-2185 |
ISSN: | 1098-6596 0066-4804 |
Popis: | Clinical isolates of Enterobacteriaceae with reduced susceptibilities to cephalosporins were collected from 1993 to 2000. The organisms were screened for the extended-spectrum β-lactamase (ESBL) phenotype, and plasmid extracts were screened for genetic markers by hybridization. A bla TEM probe was derived from pUC19; other probes were derived from pACM1, the plasmid responsible for the first known appearance of an ESBL in our institution. These probes included bla SHV , int , aac(3)-Ia , dfrA1 , IS 6100 , tetA , IncM markers, and Anon 13, a marker for the Klebsiella pneumoniae chromosomal sequences that flank bla SHV-5 . There were 42 hybridization patterns among 237 isolates. Patterns designated pACM1-like occurred in 44% of the isolates (eight species) and were always associated with the clavulanic acid (CA)-susceptible ESBL phenotype. The TEM marker was not predictive of the ESBL phenotype. Mapping indicated the presence of an SHV marker and up to 7.5 kb of its flanking chromosomal sequences in three non-IncM plasmids obtained in transformation experiments. We theorize that this DNA segment spread to other plasmids from pACM1-like sources. CA insensitivity became more frequent with time and was usually associated with either the TEM marker or the absence of both bla markers. One plasmid-encoded enzyme with characteristics of an AmpC β-lactamase was observed in a transformant lacking both TEM and SHV markers. Although SHV type ESBLs were a continuing source of reduced susceptibility to cephalosporins in our institution, organisms with different resistance mechanisms were added to the hospital microflora in later years. These changes might be related, in part, to ESBL control strategies implemented in 1995. |
Databáze: | OpenAIRE |
Externí odkaz: |