[Antibiotic sensitivity of aerobic gram-negative bacilli isolated from severe infections in 1992: results of a French multicenter study. Groupe d'Etude d'Infections à bacilles à Gram Négatif (GEIGN)].

OBJECTIVES

Antibiotic susceptibility of 649 gram-negative bacilli involved in severe infections and isolated in 18 teaching hospitals from January to December 1992 was evaluated.

METHODS

Minimal Inhibitory Concentrations were determined by agar dilution method for piperacillin, piperacillin+ tazobactam and imipenem, and by a microdilution method for 11 other antibiotics (amoxicillin, amoxicillin + clavulanic acid, cefotaxime, ceftazidime, aztreonam, ticarcillin, ciprofloxacin, fosfomycin, tobramycin, gentamicin, amikacin). Criteria of Comité Français de l'Antibiogramme de la Société Française de Microbiologie were followed for interpretation. Betalactamases were identified by isoelectric focusing and overproduction of cephalosporinase was defined by the resistance phenotype. The main species isolated were Escherichia coli (45%), Pseudomonas aeruginosa (14%), Klebsiella pneumoniae (7.8%), Salmonella spp. (7.5%), Enterobacter cloacae (4%) and Klebsiella oxytoca (4%). Most of the strains were isolated from blood culture (72.3%), respiratory tract (11.4%) and intraabdominal infections (8.6%). Most of the enterobacteria isolates were susceptible to imipenem, aztreonam, amikacin and ciprofloxacin (percentages of susceptibility were respectively 99.3, 98, 98.3 and 96.3); in most of cases clavulanic acid did not entirely restore sensitivity to amoxicillin of penicillinase-producing strains. Among 89 P. aeruginosa strains, 82% were susceptible to imipenem and ceftazidime, 81% to the association piperacillin + tazobactam and 51% to ticarcillin. Resistance rates are very high for Acinetobacter baumannii except for imipenem.

CONCLUSION

Production of TEM-type penicillinase and over-production of the chromosomal cephalosporinase are the most widely observed mechanisms of resistance (respectively 22% and 9% of 649 strains). Prevalence of extended spectrum betalactamases was low (1%) and essentially observed for K. pneumoniae.