Hospital Pseudomonas aeruginosa : Surveillance of Resistance to Gentamicin and Transfer of Aminoglycoside R Factor

Abstract

). The other antimicrobials were tested in TS broth only. The strains were grown for 18 h and subcultured for 4 h before inoculation of 104 organisms into 1.0 ml of medium containing antibiotic. After overnight incubation, the tubes were observed for minimum inhibitory concentration. Nonturbid dilutions were streaked on TS agar plates, incubated, and observed for growth 18 h later. Susceptible Pseudomonas strains (Ellsworth and Hines no. 954) and a resistant strain (Hines no. 1109) were used as susceptibility test controls.All transfer experiments were done in TS media. Resistance transfer factor was sought be standard methods for conjugation (29) and replica plating (16). For recombination, overnight cultures of donor and recipient were diluted 1:10 in TS broth and incubated at 37 C for 4 h with shaking (125 rpm). Two milliliters of donor and 0.1 ml of recipient cultures were mixed in a 50-ml Erlenmeyer flask and incubated at 37 C for 4 h without agitation. Aliquots of 0.1 ml of a 10-5 dilution were spread on TS plates and incubated at 37 C overnight. TS replica plates containing 50 Ag of gentamicin and 1,000 Mg of carbenicillin per ml were incubated overnight at 37 C for selection of exconjugants. For curing of resistance, ethidium bromide was used at 6 x 10-6 M (27), and acridine orange and acriflavine neutral in a range of 1.5 to 100 Ag/ml were used (30). The dyes were used both with and without 15-s

Evidence for a chromosomal site specifying amikacin resistance in multiresistant Serratia marcescens

“…Resistance to gentamicin and tobramycin in gram-negative bacilli and staphylococci is a growing clinical problem (6,7,14,15,21,24,28,34). A common mechanism of aminoglycoside resistance is through plasmid-specified enzymes (5,(7)(8)(9)22) (8,9).…”

Antimicrobial agent susceptibility patterns of bacteria in hospitals from 1971 to 1982

“…Before 1946, 85% of Staphylococcus aureus strains were highly susceptible to penicillin; today, only 11% remain susceptible (12). The medical community has been warned repeatedly of major increases in bacterial resistance (23,28,34,39,41), with many reports citing the increased resistance of S. aureus to methicillin (1,4,5,7,8,11,19,41,44,49) and gentamicin (5,10,11,44,48), of Haemophilus influenzae to ampicillin (16,20,27,51), of gram-negative bacilli, especially Pseudomonas aeruginosa, to aminoglycosides (13,17,24,31,32,37,38,50), and the increasing multiple drug resistance among enterococci (30, 33). The new cephalosporins appear to be responsible for bacterial cross-resistance to several betalactam antibiotics and occasionally to the aminoglycosides (43).…”