Comparative efficacies of ciprofloxacin and pefloxacin alone or in combination with fosfomycin in experimental endocarditis induced by multidrug-susceptible and -resistant Pseudomonas aeruginosa

Treatment of patients with serious infections due to carbapenem-resistant Acinetobacter baumannii: How viable are the current options?

This review critically appraises the published microbiologic and clinical data on the treatment of patients with carbapenem-resistant Acinetobacter baumannii infections. Despite being recognized as an urgent threat pathogen by the CDC and WHO, optimal treatment of patients with serious CRAB infections remains ill-defined. Few commercially available agents exhibit reliable in vitro activity against CRAB. Historically, polymyxins have been the most active agents in vitro, though interpretations of susceptibility data are difficult given issues surrounding MIC testing methodologies and lack of correlation between MICs and clinical outcomes. Most available preclinical and clinical data involve use of polymyxins, tetracyclines, and sulbactam, alone and in combination. As the number of viable treatment options is limited, combination therapy with a polymyxin is often used for patients with CRAB infections, despite the significant risk of nephrotoxicity. However, no treatment regimen has been found to reduce mortality, which exceeds 40% across most studies, or substantially improve clinical response. While some newer agents, such as eravacycline and cefiderocol, have demonstrated in vitro activity, clinical efficacy has not been fully established. New agents with clinically relevant activity against CRAB isolates and favorable toxicity profiles are sorely needed.

Fosfomycin in continuous or prolonged infusion for systemic bacterial infections: a systematic review of its dosing regimen proposal from in vitro, in vivo and clinical studies

Fosfomycin (FOS) administered intravenously has been recently rediscovered for the treatment of systemic infections due to multidrug-resistant bacteria. Its pharmacokinetic properties suggest a time-dependent dosing schedule with more clinical benefits from prolonged (PI) or continuous infusion (CI) than from intermittent infusion. We revised literature concerning PI and CI FOS to identify the best dosing regimen based on current evidence. We performed a MEDLINE/PubMed search. Ninety-one studies and their pertinent references were screened. Seventeen studies were included in the present review. The activity of FOS against Gram-negative and Gram-positive bacteria was evaluated in fourteen and five studies, respectively. Six studies evaluated FOS activity in combination with another antibiotic. Daily dosing of 12, 16, 18 or 24 g, administered with different schedules, were investigated. These regimens resulted active against the tested isolates in most cases. Emergence of resistant isolates has been shown to be preventable through the coadministration of another active antibiotic. FOS is a promising option to treat systemic infections caused by multidrug-resistant bacteria. Coadministration with another active molecule is required to prevent the emergence of resistant bacterial strains. The results of our review suggest that a therapeutic regimen including a loading dose of FOS 8 g followed by a daily dose of 16 g or 24 g CI could be the best therapeutic approach for patients with normal renal function. The dosing regimens in patients with renal insufficiency and CI or PI superiority compared with intermittent infusion in clinical settings should be further investigated.

Fosfomycin as Partner Drug for Systemic Infection Management. A Systematic Review of Its Synergistic Properties from In Vitro and In Vivo Studies

Fosfomycin is being increasingly prescribed for multidrug-resistant bacterial infections. In patients with systemic involvement, intravenous fosfomycin is usually administered as a partner drug, as part of an antibiotic regimen. Hence, the knowledge of fosfomycin pharmacodynamic interactions (synergistic, additive, indifferent and antagonistic effect) is fundamental for a proper clinical management of severe bacterial infections. We performed a systematic review to point out fosfomycin’s synergistic properties, when administered with other antibiotics, in order to help clinicians to maximize drug efficacy optimizing its use in clinical practice. Interactions were more frequently additive or indifferent (65.4%). Synergism accounted for 33.7% of total interactions, while antagonism occurred sporadically (0.9%). Clinically significant synergistic interactions were mostly distributed in combination with penicillins (51%), carbapenems (43%), chloramphenicol (39%) and cephalosporins (33%) in Enterobactaerales; with linezolid (74%), tetracyclines (72%) and daptomycin (56%) in Staphylococcus aureus; with chloramphenicol (53%), aminoglycosides (43%) and cephalosporins (36%) against Pseudomonas aeruginosa; with daptomycin (97%) in Enterococcus spp. and with sulbactam (75%) and penicillins (60%) and in Acinetobacter spp. fosfomycin-based antibiotic associations benefit from increase in the bactericidal effect and prevention of antimicrobial resistances. Taken together, the presence of synergistic interactions and the nearly total absence of antagonisms, make fosfomycin a good partner drug in clinical practice.

Synergistic Activity of Fosfomycin, Ciprofloxacin, and Gentamicin Against Escherichia coli and Pseudomonas aeruginosa Biofilms

Gram-negative (GN) rods cause about 10% periprosthetic joint infection (PJI) and represent an increasing challenge due to emergence of antimicrobial resistance. Escherichia coli and Pseudomonas aeruginosa are among the most common cause of GN-PJI and ciprofloxacin is the first-line antibiotic. Due to emergence of fluoroquinolone resistance, we evaluated in vitro the activity of fosfomycin, ciprofloxacin, and gentamicin, alone and in combinations, against E. coli and P. aeruginosa biofilms. Conventional microbiological tests and isothermal microcalorimetry were applied to investigate the anti-biofilm activity of the selected antibiotics against standard laboratory strains as well as clinical strains isolated from patients with prosthetic joint associated infections. The biofilm susceptibility to each antibiotic varied widely among strains, while fosfomycin presented a poor anti-biofilm activity against P. aeruginosa. Synergism of two-pair antibiotic combinations was observed against different clinical strains from both species. Highest synergism was found for the fosfomycin/gentamicin combination against the biofilm of E. coli strains (75%), including a gentamicin-resistant but fosfomycin-susceptible strain, whereas the gentamicin/ciprofloxacin combination presented synergism with higher frequency against the biofilm of P. aeruginosa strains (71.4%). A hypothetical bacteriolysis effect of gentamicin could explain why combinations with this antibiotic seem to be particularly effective. Still, the underlying mechanism of the synergistic effect on biofilms is unknown. In conclusion, combinatorial antibiotic application has shown to be more effective against biofilms compared to monotherapy. Further in vivo and clinical studies are essential to define the potential treatment regimen based on our results.

Fosfomycin: efficacy against infections caused by multidrug-resistant bacteria

OBJECTIVE

To analyze the indications for and the efficacy of parenteral fosfomycin, especially against multidrug-resistant (MDR) and pan-resistant bacterial infections.

PATIENTS AND METHODS

During a unique crisis in fosfomycin production, the supply of this antibiotic had to be carefully monitored in France over a 10-week period. One hundred and sixteen assessable patients were included in a prospective cohort study.

RESULTS

The main indications for use were osteoarthritis, lung infection, urinary tract infection, and bacteraemia. The 2 bacteria most frequently involved were Pseudomonas aeruginosa and methicillin-resistant Staphylococcus. MDR bacteria were seen in 71.5% (83/116) of cases, especially MDR P. aeruginosa (n = 28). Critical situations were common, with 44.0% (51/116) of hospitalizations occurring in an intensive care unit and 22.4% (26/116) of patients with septic shock. The overall outcome was favourable in 76.8% of cases (76/99 assessable patients).

CONCLUSION

This study provided a unique opportunity to describe the use of fosfomycin and assess its efficacy, especially against MDR bacterial infections, even in critical situations.

Efficacy of ciprofloxacin in an experimental model of Escherichia coli chorioamnionitis in rabbits

Pregnant rabbits were treated with ciprofloxacin alone or with gentamicin in a model of Escherichia coli chorioamnionitis, and the results were compared with those for untreated rabbits. The survival rate increased and the bacteremia decreased significantly in treated fetuses in comparison to controls (P = 0.003). Nevertheless, rapid selection of resistant mutants is a major limit to ciprofloxacin applications.

In vivo efficacy of moxifloxacin compared with cloxacillin and vancomycin in a Staphylococcus aureus rabbit arthritis experimental model

We investigated the efficacies of moxifloxacin, cloxacillin, and vancomycin in a rabbit model of Staphylococcus aureus arthritis. No significant difference between therapeutic regimens was observed after a 7-day treatment. Oral moxifloxacin could be a suitable alternative to standard parenteral therapy for S. aureus arthritis.

Role of ciprofloxacin in its synergistic effect with fosfomycin on drug-resistant strains of Pseudomonas aeruginosa

BACKGROUND

The aim of this study was to investigate the synergistic effect of ciprofloxacin (CPFX) and fosfomycin (FOM) on CPFX-resistant Pseudomonas aeruginosa strains.

METHODS

The synergistic effect was evaluated using the fractional inhibitory concentration index, acute bactericidal effect and morphological observation.

RESULTS

In the fractional inhibitory concentration index experiments, the combination of CPFX with FOM showed a synergistic effect in 20 of 74 (27.0%) strains of P. aeruginosa. From the morphological observations, it was determined that CPFX affected the outer membrane structure. CPFX combined with FOM caused striking morphological changes, resulting in bacteriolysis. A time lag experiment suggested that the addition of CPFX prior to FOM produced more pronounced bactericidal activity than the addition of FOM prior to CPFX.

CONCLUSIONS

These results indicate that the combination of CPFX with FOM induces a synergistic effect on CPFX-resistant P. aeruginosa strains. The role of CPFX is thought to be related to damage of the outer membrane, enhancing FOM penetration.

Role of fosfomycin in a synergistic combination with ofloxacin against Pseudomonas aeruginosa growing in a biofilm

We examined the combined effect of fosfomycin and ofloxacin against Pseudomonas aeruginosa biofilms of four clinical isolates with different susceptibilities to ofloxacin. A clear synergistic effect was detected in all four strains in accordance with their susceptibilities to ofloxacin. To clarify the mechanism of this synergistic action, changes in cellular accumulation of ofloxacin into fosfomycin-pretreated cells and morphological changes in cells treated with fosfomycin, ofloxacin, or fosfomycin plus ofloxacin were investigated. Pretreatment with fosfomycin significantly enhanced cellular uptake of labeled or unlabeled ofloxacin in biofilm cells as well as in floating cells. The accumulation of ofloxacin into fosfomycin-pretreated biofilm cells was further enhanced by treating cells simultaneously with ofloxacin and fosfomycin. Morphological studies using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and confocal laser scanning microscopy (CLSM) demonstrated that fosfomycin induced dramatic changes in cell shape and the outer membrane structure responsible for the altered membrane permeability of both surface and embedded biofilm cells. The resulting increased accumulation of ofloxacin in multilayers of biofilm cells was correlated with the kinetics of biofilm cell eradication, and this synergistic killing effect was confirmed by a combined study using SEM, TEM, and CLSM.

Monotherapy versus combination therapy for bacterial infections

The authors discuss the latest findings regarding the use of one or more antimicrobial drugs for a variety of infections. They offer suggestions for treatment based on a host of considerations, including the synergy and antagonism of specific drugs, type of infection, potential toxicities, and cost.

Bactericidal effect of pefloxacin and fosfomycin against Pseudomonas aeruginosa in a rabbit endocarditis model with pharmacokinetics of pefloxacin in humans simulated in vivo

The bactericidal activity of pefloxacin and fosfomycin alone and in combination against Pseudomonas aeruginosa was evaluated in an experimental rabbit endocarditis model after 24 h of treatment. Two strains with intermediate susceptibility to pefloxacin and good susceptibility to fosfomycin were tested. The serum kinetics obtained during administration of 400 mg every 12 h in humans were simulated in the animals using computer-controlled variable-flow infusion. Fosfomycin was administered as a continuous infusion at a constant flow, allowing a steady-state concentration of 47.4 +/- 11.9 mg/ml to be reached in serum. In valvular vegetations, pefloxacin was less bactericidal than fosfomycin, and in combination treatment, it reduced (but did not abolish) the bactericidal effect of fosfomycin. The duration of the pretreatment interval (12-48 h) had a negative effect on the bactericidal activity of both drugs, especially that of fosfomycin.

Advances in medical and antibiotic management of infective endocarditis

Infective endocarditis remains a serious medical problem despite advancements in laboratory detection, echocardiographic techniques, and newer antibiotic agents. This article summarizes the microbial agents in infective endocarditis, in addition to developments in medical and antibiotic management.