Naslov
Selection of Klebsiella pneumoniae mutants with high level cefotaxime resistance during growth in serum, containing therapeutic concentrations of cefotaxime

Autori
Bedenić, Branka

Izvornik
Chemotherapy (0009-3157) 48 (2002); 10-14

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
extended-spectrum beta-lactamases; cefotaxime; SHV-2 beta-lactamase; hyperproduction; Klebsiella pneumoniae

Sažetak
Background In the previous investigation on genetic characterization of extended-spectrum b-lactamases in Klebsiella pneumoniae from Zagreb, Croatia, 20 strains were found to produce SHV-2 b-lactamase. Those strains displayed a varying degree of b-lactam resistance and a wide range of b-lactamase activity. We concluded that more resistant isolates were hyperproducers of SHV-2 b-lactamase. Methods In this investigation, we tried to develop the hyperproducing variants from 8 low level SHV-2 b-lactamase producing Klebsiellae by subculturing them in the serum, containing therapeutic concentrations of cefotaxime. Results In most cases there was a moderate increase in cefotaxime resistance (two fold to three fold) except in one strain which displayed 16 fold increase in cefotaxime MIC after incubation in the serum. That strain showed a marked increase in enzyme activity as well. The strains with moderate increase in cefotaxime MIC did not produce more enzyme after exposure to the serum except of one strain which had a three fold rise in b-lactamase activity after exposure to serum. Conclusions In this investigation, it was established that the mutants with high level cefotaxime resistance developed very quickly in the biological fluids containing therapeutic concentrations of cefotaxime. It is likely to expect that a similar process occurs in the patient infected with an ESBL producing K. pneumoniae strain during antibiotic treatment. Since most of the high level cefotaxime mutants did not have a marked rise in b-lactamase activity after exposure to serum it is possible that the elevated resistance was due to some other mechanism like reduced PBP affinity, changes in outer membrane proteins or efflux by multidrug efflux pumps.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

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