| Summary: | South Africa is not excluded from the problems encountered world-wide in the treatment of
nosocomial urinary tract infections, commonly caused by enzyme-producing Enterobacteriaceae.
These enzymes include the Ã-lactamases and extended-spectrum Ã-lactamases (ESBLs) capable of hydrolysing the Ã-lactam agents and in particular the expanded-spectrum cephalosporins frequently
used. The study was designed to determine the role of Ã-lactamases in resistance development in
commonly encountered pathogens implicated in urinary tract infections and to characterise the
enzymes involved. Resistance to the Ã-lactam agents amoxicillin, ceftriaxone, ceftriaxone, piperacillin
and cefoxitin was suspected to involve the presence of one or more β-lactamases in the isolates from
Bloemfontein hospitals. Diverse and complex β-lactamases were identified and ESBLs were detected
in 80% of the isolates. These β-lactamases were characterised by isoelectric focusing (IEF) and
genetic analysis (DNA amplification by PCR) to investigate the presence of possible genes
responsible for resistance development. The production of blaTEM and blaSHV type genes was
demonstrated. Isolates harbouring these genes were highly resistant to amoxicillin and piperacillin,
with MIC90s of >128μg/ml. Resistance to these antibiotics was shown to be readily transferred
between strains and there was an indication that the resistance genes are carried on plasmids and
was transferred by conjugation. A plasmid of 9-10 kb was detected in 83% of the isolates and could
be one of the mechanisms implicated in the transfer of ESBLs in uropathogenic bacteria. Ã-Lactam
resistance could be attributed to the presence and action of Ã-lactamases such as the TEM and SHV
type enzymes and this resistance can be transmitted between bacteria, causing problems specifically
in the hospital environment. Further and continuous investigations are required to find a solution for
this ever increasing problem.
|
|---|
