Entry of sanfetrinem into human polymorphonuclear granulocytes and its cell-associated activity against intracellular, penicillin-resistant Streptococcus pneumoniae

Carbapenems: past, present, and future

In this review, we summarize the current "state of the art" of carbapenem antibiotics and their role in our antimicrobial armamentarium. Among the β-lactams currently available, carbapenems are unique because they are relatively resistant to hydrolysis by most β-lactamases, in some cases act as "slow substrates" or inhibitors of β-lactamases, and still target penicillin binding proteins. This "value-added feature" of inhibiting β-lactamases serves as a major rationale for expansion of this class of β-lactams. We describe the initial discovery and development of the carbapenem family of β-lactams. Of the early carbapenems evaluated, thienamycin demonstrated the greatest antimicrobial activity and became the parent compound for all subsequent carbapenems. To date, more than 80 compounds with mostly improved antimicrobial properties, compared to those of thienamycin, are described in the literature. We also highlight important features of the carbapenems that are presently in clinical use: imipenem-cilastatin, meropenem, ertapenem, doripenem, panipenem-betamipron, and biapenem. In closing, we emphasize some major challenges and urge the medicinal chemist to continue development of these versatile and potent compounds, as they have served us well for more than 3 decades.

Synergistic effect of erythromycin on polymorphonuclear cell antibacterial activity against erythromycin-resistant phenotypes of Streptococcus pyogenes

To evaluate the synergistic activity of erythromycin and human polymorphonuclear cells (PMNs) on the binomial erythromycin-resistant (ERY(R)) Streptococcus pyogenes/host, the phagocytic and bactericidal activities of PMNs against ERY(R) streptococcal strains (cMLS(B), M, and iMLS(B) A, B and C phenotypes) were assessed in the presence of the macrolide. The results showed that when erythromycin, PMNs and streptococci [both erythromycin-sensitive (ERY(S)) and ERY(R)] were simultaneously present in the culture medium, PMN phagocytic activity was similar to that of drug-free controls. In contrast, the results emphasised a significant high increase in intracellular killing by PMNs in the presence of erythromycin not only for ERY(S) streptococci but also for ERY(R)S. pyogenes with high (cMLS(B), iMLS(B) A and iMLS(B) B phenotypes) and moderate (M and iMLS(B) C phenotypes) erythromycin resistance compared with controls without drug. From literature data it emerged that, even if intracellularly concentrated, erythromycin is relatively inactive because of its instability. The results indicate that the enhanced intra-PMN streptococcal killing detected is mainly attributable to PMN bactericidal systems that synergise with intracellular erythromycin in eradicating ERY(R)S. pyogenes strains (both with high and moderate resistance). These data confirm that the antibiotic resistance detected in vitro does not always imply a failure of antimicrobial treatment.

Role of fosfomycin tromethamine in modulating non-specific defence mechanisms in chronic uremic patients towards ESBL-producing Escherichia coli

Antimicrobial agents and polymorphonuclear cells (PMNs) have the potential to interact in such a way that improve the therapy for infectious diseases. In immunocompromised patients highly susceptible to microbial infections with high morbidity and mortality, several metabolic and functional alterations in PMNs, mostly related to microbicidal activity, are observed. Therefore, the antibiotic of choice should have a good antimicrobial effect without impairing host defences. The aim of this study is to evaluate in vitro effects of sub-inhibiting fosfomycin tromethamine (FT) concentrations on the primary functions of PMNs from healthy subjects and immunocompromised patients (haemodialysed and renal transplant recipients), against an ESBL-producing Escherichia coli, the most common aetiological agent in urinary tract infections (UTIs). FT is considered a first line drug in the eradication of UTIs due to its appropriate antimicrobial spectrum, oral bioavailability and minimal risk of microbial resistance. Our results provide evidence that FT is able to induce enhancement of the depressed phagocytic response of PMNs from patients on chronic haemodialysis and from renal transplant recipients, restoring their primary functions in vitro against ESBL-producing E. coli. All these data permit the conclusion that uremic-infected patients might additionally benefit from the immunomodulating properties of FT.

Immunomodulating effect of antimicrobial agents on cytokine production by human polymorphonuclear neutrophils

It has been previously demonstrated that some antimicrobial agents enhance activities of human polymorphonuclear neutrophils (PMNs). The effect on the release of cytokines in an inflammatory context from PMNs by these antibiotics was evaluated. We studied the effect of the release of some cytokines by human PMNs RT-PCR analysis on a clinical strain of Klebsiella pneumoniae by comparing the effect with that observed in the presence of co-amoxiclav, sanfetrinem, clarithromycin, prulifloxacin and tobramycin. All the drugs tested were capable of modulating PMN synthesis in vitro of pro-inflammatory cytokines IL-8, IL-1beta, TNF-alpha and IL-6, but not that of anti-inflammatory cytokine IL-10. The degree of their stimulatory or inhibitory potency varied with the cytokine examined.

Improved phagocyte response by co-amoxiclav in renal transplant recipients

BACKGROUND

Infectious diseases are a major source of morbidity and mortality for immunosuppressed transplant recipients and the antimicrobial chemotherapy can be often less effective in these individuals, because the contribution of underlying host defenses is absent.

METHODS

The influence of co-amoxiclav on the functions of polymorphonuclear granulocytes (PMNs) from renal transplant recipients were investigated.

RESULTS

PMNs from renal transplant recipients showed a diminished phagocytic activity with reduced phagocytosis and bactericidal activity against intracellular Klebsiella pneumoniae, compared to that seen with PMNs from healthy subjects. Co-amoxiclav significantly elicited the functions of PMNs from uremic patients, resulting in an increased percentage of ingested klebsiellae and in a higher bactericidal effect (98-99%), compared with the drug-free control system. When PMNs were collected from renal transplant recipients treated with co-amoxiclav a significant high increase in both phagocytosis and killing activity were detected, showing the co-amoxiclav capability of "restoring" even in vivo the depressed primary functions of PMNs.

CONCLUSIONS

The interesting beneficial properties of co-amoxiclav, which result in restoring the phagocyte-dependent response in renal transplant patients both in vitro and in vivo, may make this drug more suitable for the treatment of infections in patients with defects of phagocyte functions.