1992 Volume 66 Issue 11 Pages 1572-1579
Forty-two isolates of P. aeruginosa from various infections were each incubated in Mueller-Hinton broth including piperacillin, cefsulodin, ceftazidime, imipenem, gentamicin or norfloxacin (1MIC-4MIC) at 35°C for 18 hours, and serotyped using monoclonal antibodies. Serotypes of 4 (9.5%)-8 (19.0%) of the 42 isolates each changed to different groups after incubation. No relationship was found between serotypes of the formed variants and anti-pseudomonal drugs used.
When P. aeruginosa TA-2 was exposed to cefsulodin at different concentrations (1MIC and 2MIC) under the above conditions, the distinct variants different in serotypes were formed according to the drug concentrations. Furthermore, P. aeruginosa TA-2 and TA-13 were incubated in Mueller-Hinton broth including cefsulodin (1/2 or 2MIC) and gentamicin (1/2MIC), respectively, and the growth curves of parent and variant cells were determined. In the experiments, the variants appeared 6 hours after onset of the incubation and grew with the parents.
The present results may explain our findings previously reported; coexistence of colonies different in serotype of P. aeruginosa isolated from some individual patients. The results indicate the possibility that alteration in bacterial surfaces in association with changes in serotypes might occur in vivo in these patients infected with P. aeruginosa and treated with anti-pseudomonal drugs.
