Influence of imipenem on the serum resistance of enterobacteriaceae

Complement component C9 enhances the capacity of beta-lactam antibiotics to kill Escherichia coli in vitro and in vivo

Complement component C9 is required for rapid complement-mediated killing of Escherichia coli. In this report, the influence of supplemental C9 on the bactericidal and protective effects of beta-lactam antibiotics in neonates was assessed. By rocket immunoelectrophoresis, the intrinsic C9 concentrations of pooled serum from both human and rat neonates was less than 20% of adult levels. Supplemental C9 purified from human plasma enhanced the capacity of ampicillin-treated serum from human neonates to impair the survival of E coli O7:K1:NM (P < 0.02). Similarly, supplemental C9 enhanced the capacity of cefotaxime-treated neonatal rat serum to impair the survival of E coli O1:K1:NM (P < 0.05). Moreover, the intraperitoneal administration of C9 enhanced the survival of cefotaxime-treated neonatal rats that were septic with E coli (P < 0.05). These observations may contribute to the development of new strategies, such as augmentation of complement component serum concentrations, to reduce the morbidity and mortality of neonatal E coli sepsis.

Influence of beta-lactam antibiotics on serum resistance of K1-positive blood culture isolates of Escherichia coli

The K1-positive strains of Escherichia coli are a group with considerable clinical importance, serum resistance being a common virulence factor of these strains. In the present paper, the influences of cephaloridine, imipenem, and ceftazidime on the serum resistance of eight serum-resistant K1-positive E. coli blood culture isolates with smooth-type lipopolysaccharide were studied. All strains were rendered more serum sensitive by treatment with subinhibitory concentrations of antibiotics. The amount of the reduction of serum resistance was dependent on the concentration of the antibiotic. Amounts of K1 produced under the influence of the antibiotics were measured and were found to be reduced for almost all strains tested. To further test the hypothesis that antibiotic-induced reduction of serum resistance is mediated by inhibition of K1 expression, isogenic mutants of one strain were produced by selection for resistance against infection with K1-specific bacteriophages. These mutants were found to be highly serum sensitive. We conclude from this study that beta-lactam antibiotics can render K1-positive serum-resistant strains of E. coli highly serum sensitive and that this effect is mediated by inhibition of K1 expression.

Imipenem/cilastatin. A review of its antibacterial activity, pharmacokinetic properties and therapeutic efficacy

Imipenem is the first available semisynthetic thienamycin and is administered intravenously in combination with cilastatin, a renal dipeptidase inhibitor that increases urinary excretion of active drug. In vitro studies have demonstrated that imipenem has an extremely wide spectrum of antibacterial activity against Gram-negative and Gram-positive aerobic and anaerobic bacteria, even against many multiresistant strains of bacteria. It is very potent against species which elaborate beta-lactamases. Imipenem in combination with equal doses of cilastatin has been shown to be generally well tolerated and an effective antimicrobial for the treatment of infections of various body systems. It is likely to be most valuable as empirical treatment of mixed aerobic and anaerobic infections, bacteraemia in non-neutropenic patients and serious hospital-acquired infections.