[Characterization of the resistance to combinations of beta lactams and inhibitors of beta-lactamases in Escherichia coli. Effect of the type and amount of beta-lactamase production].
BACKGROUND
The aim of this study was to characterize resistance of Escherichia coli in our environment to four associations of beta-lactams and beta-lactamase inhibitors (beta Lac) studying the influence of the type and level of beta Lac production.


METHODS
The minimum inhibitory concentration (MIC) to ampicillin/sulbactam (A/S), amoxycillin/clavulanic acid (A/C), ticarcillin/clavulanic acid (T/C) and piperacillin/tazobactam (P/T) assessed was in 245 strains of E. coli resistant to ampicillin, consecutively isolated in our laboratory from September 1995 to March 1996. The beta Lac produced by these isolates were identified by isoelectrofocusing and spectrophotometrically quantified.


RESULTS
The sensitivity to A/S, A/C, T/C and P/T was of 9.4, 86.9, 64.5 and 89.4%, respectively. The strains with only one beta Lac which cofocused with TEM-1 were the most frequent (215/245), followed by those producing a cofocusing enzyme with SHV-1 (7/245). A significant correlation was observed between beta Lact activity of the 215 TEM-1 strains and their MIC at A/S (r = 0.53; p < 0.001), A/C (r = 0.46; p < 0.001), T/TC (r = 0.58; p < 0.001), and P/T (r = 0.42; p < 0.001). The comparison between enzyme activity of the isolates of the different categories of susceptibility showed significant differences (p < 0.05) for the four associations studied.


CONCLUSIONS
TEM-1 production is the main cause of resistance to beta-lactams in E. coli in our environment. The inhibitory efficacy of sulbactam, clavulanic acid and tazobactam over TEM-1 is inversely proportional to the amounts of enzyme produced. The high rate of resistance to A/S and T/C E. coli presents in our environment is mainly due to a hyperproduction of TEM-1.
del Mar Pérez-Moreno
M
M
Servicio de Análisis Clínicos, Hospital Verge de la Cinta, Tortosa, Tarragona.
Pous-Miralles
G
G
Romera-Sastre
G
G
Panisello-Bertomeu
J M
JM
Jardí-Baiges
A M
AM
Zarazoga-López
J
J
D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D004338:Drug Combinations; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology; D008826:Microbial Sensitivity Tests; D013045:Species Specificity; D018440:beta-Lactam Resistance; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000096:biosynthesis / Q000145:classification / Q000502:physiology*; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D065093:beta-Lactamase Inhibitors; D047090:beta-Lactams; D001618:beta-Lactamases; C034413:beta-lactamase TEM-1
Caracterización de la resistencia a asociaciones de betalactámicos e inhibidores de betalactamasas en Escherichia coli. Influencia del tipo y nivel de producción de betalactamasas.