Naslov
Effect of hyperproduction of SHV-2 and SHV-5 beta-lactamase on the beta-lactamase stability of oral cephalosporins

Autori
Bedenić, Branka

Izvornik
Journal of Antimicrobial Chemotherapy (0305-7453) 6 (1999), Suppl;

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, kongresno priopcenje, znanstveni

Ključne riječi
SHV-2 beta-lactamase; SHV-5 beta-lactamase; hyperproduction

Sažetak
Extended spectrum beta-lactamases are plasmid-ediated enzymes that confer resistance to oxymino-beta-lactams that were designed to be effective against strains producing known plasmid mediated beta-lactamases. Apart of the type of beta-lactamase a very import factor in determination of resistance to oxymino beta-lactam is the amount of enzymes produced which can vary between the strains producing the same type of enzyme. The aim of this investigation was to determine the influence of hyperproduction of SHV-5 and SHV-2 beta-lactamase on the beta-lactamase stability of oral cephalosporins and amoxycillin. The both of beta-lactamases mentioned in the investigation were associated with very high levels of resistance to amoxycillin, cephalexin and cefaclor. The strains producing both types of enzymes displayed wide range of MICs of all oral compounds. Our SHV-2 producing strains expressed higher level of resistance to ceftibuten and cefetamet compared to previous investigations.The E. coli transconjugants had slightly lower MICs of the mentioned antibiotics than their respective K. pneumoniae donor strains.SHV-5 containing strains expressed very high MICs for new generation oral cephalosporins too which is difficult to explain solely by the presence of the enzyme since the hydrolysis rates were low even for the beta-lactamase hyperproducing strains. The possible explanation is the presence of an additional mechanism of resistance, i.e. permeability barrier. The hyperproducing strains had slightly higher hydrolysis rates (Vmax) for most cephalosporins compared to low level beta-lactamase producing strains but there was no difference observed when enzyme activities were standardized against hydrolysis rates for penicillin (relative enzyme activity), since the hyperproducing strains had two or three times higher Vmax for benzylpenicillin. Oral beta-lactams with an increased activity and an extended-spectrum have become available. However increased activity against susceptible strains does not always correlate with activity against strains producing ESBLs particulary hyperproducers.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

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