Klebsiella species: antimicrobial susceptibilities, bactericidal kinetics, and in vitro inactivation of beta-lactam agents

Abstract

In vitro properties of 19 antimicrobial agents were tested with 56 isolates of Klebsiella spp. The aminoglycosides and the new beta-lactam compounds cefotaxime and moxalactam were the most inhibitory drugs tested. Chloramphenicol, tetracycline, trimethoprim, and trimethoprim-sulfamethoxazole were moderately active, whereas piperacillin, mezlocillin, and furazlocillin were ineffective against 25% of the isolates. Gentamicin was the only agent tested that was uniformly bactericidal in time-kill experiments with drug concentrations of four times the minimal inhibitory concentration. In combination studies with gentamicin, moxalactam and furazlocillin each increased the rate of bacterial killing for three of five isolates as compared with gentamicin alone, whereas chloramphenicol significantly retarded the rate of bacterial killing for the same number of strains. Furazlocillin was completely inactivated after 24 h of incubation with each of five selected strains. The inactivation of moxalactam, cefoxitin, and cephalothin was 36, 56, and 72%, respectively. In all instances in which these four agents were inactivated to levels below the minimal bactericidal concentration, there was accelerated growth after initial inhibition. However, regrowth also occurred in three instances in which drug levels were higher than the minimal bactericidal concentration. Retesting after drug exposure revealed a 4-to 32-fold rise in the minimal inhibitory concentration and minimal bactericidal concentration in two of these isolates.Infections caused by Klebsiella spp. continue to account for a large portion of nosocomial disease with a high rate of morbidity and mortality (6, 7). Aminoglycosides alone and in combination with cephalosporins are frequently prescribed for these serious infections (1). The purpose of this investigation was (i) to study the in vitro activity of aminoglycosides, beta-lactam agents, and other antimicrobial agents against recent clinical isolates of Klebsiellapneumoniae and Klebsiella oxytoca, (ii) to deternine the bactericidal ability of these agents in time-kill experiments, (iii) to examine the rate of bacterial killing of gentamicin alone and in combination with other antimicrobial agents, and (iv) to deternine the rates of inactivation of the betalactam compounds by Klebsiella spp. during the time-kill experiments. MATERIALS AND METHODSAntimicrobial agents. A total of 19 antimicrobial agents were studied. The aminoglycosides used were streptomycin, gentamicin, tobramycin, amikacin, and netilmicin. The beta-lactam compounds included cephalothin, cefazolin, cephapirin, cefoxitin, cefaman-

Retrospective Analysis of Clinical and Microbiological Aspects of Klebsiella oxytoca Bacteremia Over a 10-Year Period

“…Until recently, a relatively small number of cases of Klebsiella oxytoca bacteremia were included in previous studies of Klebsiella bacteremia [3,4,5,6,7,8]. However, previous investigators found no significant differences between the clinical features of Klebsiella pneumoniae bacteremia and those of Klebsiella oxytoca bacteremia [4,20]. To our knowledge, this is the largest series of Klebsiella oxytoca bacteremia.…”

Diffuse-Type Tenosynovial Giant Cell Tumor of the Knee with Concurrent Polymicrobial Infection (Klebsiella oxytoca and Group B Streptococcus)

“…Infections caused by KO are nearly always nonarticular and predominately occur in the nosocomial setting in patients with concurrent medical conditions [13][14][15][16][17][18]. Similarly, the likelihood of a GBS infection is increased in individuals who are immunocompromised because of underlying conditions such as diabetes [19][20][21].…”

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“…Panwalker and his associates [9] have shown that moxalactam does not •' Number of strains tested. l'M !C,ll(pg/ml). '…”