Study on Gentamicin and Carbenicillin resistant strains of Pseudomonas aeuroginosa

ABSTRACT

Pseudomonas aeruginosa strains were isolated from different clinical wards of Tanta University hospital during the period from January 1981 till the end of December of the same year. Extensive use of gentamicin and carbenicillin against Pseudomonas during the last few years, has caused an increase in the number of resistant strains to these antibiotics. Gentamicin resistant strains during one year of study increased from 10.6% of the total isolates, in the first 6 months, to 20% at the end of the second 6 months of the same year, while carbenicillin resistant strains increased from 25.3% to 48.2% during the same period. It was found that 88% of total isolates were resistant to ampicillin, chloramphenicol, tetracycline, kanamycin, kefeoldin, streptomycin and sulfamethazole. Gentamicin and carbenicillin resistant strains were also resistant to the above mentioned antibiotics. Minimum inhibitory concentration of gentamicin and carbenicillin and transfer studies were performed on strains resistant to all the antibiotics tested. No transfer of gentamicin resistance traits was observed. The unstability of gentamicin resistance and other resistance characters, in the presence of acriflavin indicated the extrachromosomal nature of the resistance characters. Five serotypes were noted among the strains with no evidence of cross infection. Four of the studied strains displayed an unstable gentamicin resistance at 12°C but not at 37°C. This instability appeared to be linked to the rate of growth of these strains