Pharmacodynamics of ceftriaxone and cefixime against community-acquired respiratory tract pathogens

Development and characterization of a new swine model of invasive pneumococcal pneumonia

Streptococcus pneumoniae is the most common microbial cause of community-acquired pneumonia. Currently, there are no available models of severe pneumococcal pneumonia in mechanically ventilated animals to mimic clinical conditions of critically ill patients. We studied endogenous pulmonary flora in 4 healthy pigs and in an additional 10 pigs in which we intra-bronchially instilled S. pneumoniae serotype 19 A, characterized by its resistance to penicillin, macrolides and tetracyclines. The pigs underwent ventilation for 72 h. All pigs that were not challenged with S. pneumoniae completed the 72-h study, whereas 30% of infected pigs did not. At 24 h, we clinically confirmed pneumonia in the infected pigs; upon necropsy, we sampled lung tissue for microbiological/histological confirmation of pneumococcal pneumonia. In control pigs, Streptococcus suis and Staphylococcus aureus were the most commonly encountered pathogens, and their lung tissue mean ± s.e.m. concentration was 7.94 ± 20 c.f.u./g. In infected pigs, S. pneumoniae was found in the lungs of all pigs (mean ± s.e.m. pulmonary concentration of 1.26 × 10⁵ ± 2 × 10² c.f.u./g). Bacteremia was found in 50% of infected pigs. Pneumococcal pneumonia was confirmed in all infected pigs at 24 h. Pneumonia was associated with thrombocytopenia, an increase in prothrombin time, cardiac output and vasopressor dependency index and a decrease in systemic vascular resistance. Upon necropsy, microbiological/histological pneumococcal pneumonia was confirmed in 8 of 10 pigs. We have therefore developed a novel model of penicillin- and macrolide-resistant pneumococcal pneumonia in mechanically ventilated pigs with bacteremia and severe hemodynamic compromise. The model could prove valuable for appraising the pathogenesis of pneumococcal pneumonia, the effects associated with macrolide resistance and the outcomes related to the use of new diagnostic strategies and antibiotic or complementary therapies.

Efficacy of Ceftriaxone 1 g daily Versus 2 g daily for The Treatment of Community-Acquired Pneumonia: A Systematic Review with Meta-Analysis

Introduction: Ceftriaxone has been recommended as a first-line treatment for various infections; however, the doses for pneumonia have not been a consensus in randomized clinical trials. To compare ceftriaxone 1 g daily efficacy to other ceftriaxone dosing regimens in community-acquired pneumonia. Area covered: We performed a systematic review and meta-analysis on PubMed, Web of Science, Scopus, and LILACS. Randomized controlled trials of ceftriaxone in community-acquired pneumonia were included. Outcomes included clinical cure in modified intention-to-treatment, clinically and microbiologically evaluable patients. Expert opinion: Ceftriaxone dosages of 1 g daily are as safe and effective as other antibiotic regimens for community-acquired pneumonia. Twenty-four articles fulfilled the inclusion criteria. Twelve studies evaluated ceftriaxone regimens at a dosage of 2 g daily and 12 studies evaluated ceftriaxone at a dosage of 1 g daily. The odds-ratio of clinical cure in the modified intention-to-treatment patients administered either ceftriaxone (4666 patients) or a comparator (4411 patients) was 0.98 (95% CI [0.82-1.17]). Comparator regimens showed similar efficacy to ceftriaxone regimens of 1 g daily, with an odds ratio of 1.03 (95% CI [0.88-1.20]). Dosages higher than ceftriaxone 1 g daily did not result in improved clinical outcomes for community-acquired pneumonia patients (OR 1.02, 95% CI [0.91-1.14]).

SYN-004 (ribaxamase), an oral beta-lactamase, mitigates antibiotic-mediated dysbiosis in a porcine gut microbiome model

AIM

To evaluate an antibiotic inactivation strategy to protect the gut microbiome from antibiotic-mediated damage.

METHODS AND RESULTS

SYN-004 (ribaxamase) is an orally delivered beta-lactamase intended to degrade penicillins and cephalosporins within the gastrointestinal tract to protect the microbiome. Pigs (20 kg, n = 10) were treated with ceftriaxone (CRO) (IV, 50 mg kg^-1 , SID) for 7 days and a cohort (n = 5) received ribaxamase (PO, 75 mg, QID) for 9 days beginning the day before antibiotic administration. Ceftriaxone serum levels were not statistically different in the antibiotic-alone and antibiotic + ribaxamase groups, indicating ribaxamase did not alter systemic antibiotic levels. Whole-genome metagenomic analyses of pig faecal DNA revealed that CRO caused significant changes to the gut microbiome and an increased frequency of antibiotic resistance genes. With ribaxamase, the gut microbiomes were not significantly different from pretreatment and antibiotic resistance gene frequency was not increased.

CONCLUSION

Ribaxamase mitigated CRO-mediated gut microbiome dysbiosis and attenuated propagation of the antibiotic resistance genes in pigs.

SIGNIFICANCE AND IMPACT OF THE STUDY

Damage of the microbiome can lead to overgrowth of pathogenic organisms and antibiotic exposure can promote selection for antibiotic-resistant micro-organisms. Ribaxamase has the potential to become the first therapy designed to protect the gut microbiome from antibiotic-mediated dysbiosis and reduce emergence of antibiotic resistance.

In vitro activity of human-simulated epithelial lining fluid exposures of ceftaroline, ceftriaxone, and vancomycin against methicillin-susceptible and -resistant Staphylococcus aureus

Staphylococcus aureus, including methicillin-susceptible (MSSA) and -resistant (MRSA) strains, is an important pathogen of bacterial pneumonia. As antibiotic concentrations at the site of infection are responsible for killing, we investigated the activity of human-simulated epithelial lining fluid (ELF) exposures of three antibiotics (ceftaroline, ceftriaxone, and vancomycin) commonly used for treatment of S. aureus pneumonia. An in vitro pharmacodynamic model was used to simulate ELF exposures of vancomycin (1 g every 12 h [q12h]), ceftaroline (600 mg q12h and q8h), and ceftriaxone (2 g q24h and q12h). Four S. aureus isolates (2 MSSA and 2 MRSA) were evaluated over 72 h with a starting inoculum of ∼ 10(6) CFU/ml. Time-kill curves were constructed, and microbiological response (change in log10 CFU/ml from 0 h and the area under the bacterial killing and regrowth curve [AUBC]) was assessed in duplicate. The change in 72-h log10 CFU/ml was largest for ceftaroline q8h (reductions of >3 log10 CFU/ml against all strains). This regimen also achieved the lowest AUBC against all organisms (P < 0.05). Vancomycin produced reliable bacterial reductions of 0.9 to 3.3 log10 CFU/ml, while the activity of ceftaroline q12h was more variable (reductions of 0.2 to 2.3 log10 CFU/ml against 3 of 4 strains). Both regimens of ceftriaxone were poorly active against MSSA tested (0.1 reduction to a 1.8-log10 CFU/ml increase). Against these S. aureus isolates, ELF exposures of ceftaroline 600 mg q8h exhibited improved antibacterial activity compared with ceftaroline 600 mg q12h and vancomycin, and therefore, this q8h regimen deserves further evaluation for the treatment of bacterial pneumonia. These data also suggest that ceftriaxone should be avoided for S. aureus pneumonia.

Pharmacokinetics of ceftriaxone in plasma and bone of patients undergoing hip or knee surgery

OBJECTIVES

Patients undergoing hip or knee replacement therapy are routinely pretreated with antibiotics before surgery. It is controversial in which antibiotic is the treatment of choice for this purpose. One possibility is the cephalosporin ceftriaxone. Here, we wanted to know if effective tissue concentrations are reached.

METHODS

We studied plasma and bone kinetics of ceftriaxone in orthopaedic patients (n = 22) treated with ceftriaxone (2 g) immediately prior operation. Plasma samples were withdrawn before and at three time points after ceftriaxone infusion. After bone replacement, extracts from cancellous bone or cortical bone were obtained, and ceftriaxone was quantified using column chromatography.

KEY FINDINGS

The plasma kinetics of ceftriaxone and distribution into bone were analysed using a population approach (ADAPT 5). The population mean of the area under the curve (AUC) was 140 mg h/l. A cancellous bone to plasma concentration ratio of 1.12 ± 1.29 was achieved 5 h after start of infusion. The half-life of uptake into the cortical bone was less (8.4 h) than into cancellous bone (12.1 h, P < 0.05).

CONCLUSIONS

Under these experimental conditions, concentrations of ceftriaxone in cancellous and cortical bone should be adequate to protect the patients against usual ceftriaxone-sensitive nosocomial infections and are substantially lower than the plasma concentrations.

Predicting the Clinical Efficacy of Generic Formulations of Ceftriaxone

Time above MIC (T>MIC) is regarded as the best pharmacokinetic/pharmacodynamic (PK/PD) parameter for predicting the clinical efficacy of cephalosporins. The concentration of non-protein-bound proprietary ceftriaxone (Rocephin, Roche) in body fluids exceeds this PK/PD criterion for the treatment of Streptococcus pneumoniae respiratory infections. However, the pharmaceutical quality of several generic products may be inferior to Rocephin. We have calculated the variations in fluid concentrations of 34 generic formulations of ceftriaxone and, by mathematical modelling, the implications for attainment of recommended PK/PD criteria, specifically: Treatment of S. pneumoniae infections based on the time that non-protein-bound ceftriaxone concentration in pleural fluid exceeds the CLSI (NCCLS) breakpoint of 4 mg/L for identification of resistant isolates. Impact upon Monte Carlo simulations in plasma for the treatment of S. pneumoniae infections based on T>MIC for 50% dosing interval. Rocephin exceeded the required PK/PD parameters at the mean and two standard deviation levels in both investigations. In contrast, most generic products failed to achieve required PK/PD levels in both investigations. As a consequence, some generic formulations of ceftriaxone may increase risks of clinical failure and/or emergence of resistant isolates.

Ceftriaxone: an update of its use in the management of community-acquired and nosocomial infections

Ceftriaxone is a parenteral third-generation cephalosporin with a long elimination half-life which permits once-daily administration. It has good activity against Streptococcus pneumoniae, methicillin-susceptible staphylococci, Haemophilus influenzae, Moraxella catarrhalis and Neisseria spp. Although active against Enterobacteriaceae, the recent spread of derepressed mutants which hyperproduce chromosomal beta-lactamases and extended-spectrum beta-lactamases has diminished the activity of all third-generation cephalosporins against these pathogens necessitating careful attention to sensitivity studies. Extensive data from randomised clinical trials confirm the efficacy of ceftriaxone in serious and difficult-to-treat community-acquired infections including meningitis, pneumonia and nonresponsive acute otitis media. Ceftriaxone also has efficacy in other community-acquired infections including uncomplicated gonorrhoea, acute pyelonephritis and various infections in children. In the nosocomial setting, extensive data also confirm the efficacy of ceftriaxone with or without an aminoglycoside in serious Gram-negative infections, pneumonia, spontaneous bacterial peritonitis and as surgical prophylaxis. Outpatient use of ceftriaxone, either as part of a step-down regimen or parenterally, is a distinguishing feature of the data gathered on the agent over the last decade. The review focuses on new applications of the drug and its use in infections in which the causative pathogens or their resistance patterns have changed over the past decade. Ceftriaxone has a good tolerability profile, the most common events being diarrhoea, nausea, vomiting, candidiasis and rash. Ceftriaxone may cause reversible biliary pseudolithiasis, notably at higher dosages of the drug (>/=2 g/day); however, the incidence of true lithiasis is <0.1%. Injection site discomfort or phlebitis can occur after intramuscular or intravenous administration.

CONCLUSIONS

As a result of its strong activity against S. pneumoniae, ceftriaxone holds an important place, either alone or as part of a combination regimen, in the treatment of invasive pneumococcal infections, including those with reduced beta-lactam susceptibility. Its once-daily administration schedule allows simplification of otherwise complex regimens in a hospital setting and has also contributed to its popularity as a parenteral agent in an ambulatory setting. These properties, together with a well characterised tolerability profile, mean that ceftriaxone is likely to retain its place as an important third-generation cephalosporin in the treatment of serious community-acquired and nosocomial infections.