Poor outcomes of empiric ceftriaxone ± azithromycin for community-acquired pneumonia caused by methicillin-susceptible Staphylococcus aureus

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.

Ceftriaxone and methicillin-susceptible staphylococcus aureus: a perspective from pharmacokinetics/pharmacodynamics studies

INTRODUCTION

: Usage of ceftriaxone-based therapy to treat Methicillin-Susceptible Staphylococcus aureus (MSSA) infections is a controversial issue, from in vitro to clinical studies.

AREA COVERED

: We conducted a literature review using PubMed of articles with ceftriaxone pharmacokinetics parameters and built a probability of target attainment (PTA) based on PK values from stable conditions (non-critically-ill patients) with goals of fT>55%, fT>75%, and fT>100%. Ceftriaxone's minimal inhibitory concentration from 31 MSSA strains (0.25-64mg/L) was used to build the cumulative fraction response (CFR). The isolates were clinically relevant from blood, bronchoalveolar lavage, and soft tissue biopsy.

EXPERT OPINION

The results from controversies about using ceftriaxone for MSSA infections have been commonly addressed in the literature. However, variables such as (i) pharmacokinetic profile, (ii) pharmacodynamic target, (iii) site of infection, and (iv) MIC distributions may influence divergences. From this pharmacokinetics-pharmacodynamics perspective, ceftriaxone may be a reasonable option for MSSA infections when the MIC50 and MIC90 were 4mg/L and 8mg/L. CFR analysis demonstrated that ceftriaxone 1g q24h could be used if bacteriostasis is the aim (fT>55%), while 1g q12h should be used for bactericidal effects (fT>75% or fT>100%). Since there is a lack of data from clinical trials, the findings should be interpreted cautiously.

Clinical cure with ceftriaxone versus ceftaroline or ceftobiprole in the treatment of staphylococcal pneumonia: a systematic review and meta-analysis

Ceftriaxone is an empirical antibiotic commonly used to treat pneumonia. However, its use to treat infections caused by methicillin-susceptible Staphylococcus aureus (MSSA) is controversial given limited evidence of its clinical efficacy. The objective of this study was to compare the clinical efficacy of ceftriaxone with either ceftaroline or ceftobiprole in the treatment of pneumonia caused by MSSA. A systematic review and meta-analysis of randomised controlled trials (RCTs) comparing clinical cure in patients with pneumonia who received ceftriaxone versus those who received either ceftaroline or ceftobiprole was conducted. Patients who received ceftriaxone plus vancomycin were excluded. The PubMed, Embase and Cochrane Library databases as well as clinical trial registries were searched up to 8 June 2018. Risk differences (RDs) with 95% confidence intervals (CIs) were estimated using a random-effects model and assessing for heterogeneity (I2). A total of five RCTs met the inclusion criteria; four used ceftaroline and one used ceftobiprole. Four studies included adults and one included paediatric patients. The adult studies included non-intensive care unit patients with mild-to-moderate community-acquired pneumonia. Clinical cure was statistically lower with ceftriaxone (RD, -28.5%, 95% CI -53.5% to -3.4%; P = 0.026; I2 = 16.321%) than with ceftaroline or ceftobiprole. In conclusion, ceftriaxone use was associated with higher clinical failure of MSSA pneumonia compared with ceftaroline or ceftobiprole. This supports the notion that ceftriaxone is not an ideal agent for the treatment of MSSA infections and adds new evidence against its use for MSSA pneumonia.

Determining best outcomes from community-acquired pneumonia and how to achieve them

Community-acquired pneumonia (CAP) is a common acute medical illness with a standard, effective treatment that was introduced before the evidenced-based medicine era. Mortality rates have improved in recent decades but improvements have been minimal when compared to other conditions such as acute coronary syndromes. The standardized approach to treatment makes CAP a target for comparative performance and outcome measures. While easy to collect, simplistic outcomes such as mortality, readmission and length of stay are difficult to interpret as they can be affected by subjective choices and health care resources. Proposed clinical- and patient-reported outcomes are discussed below and include measures such as the time to clinical stability (TTCS) and patient satisfaction, which can be compared between health institutions. Strategies to improve these outcomes include use of a risk stratification tool, local antimicrobial guidelines with antibiotic stewardship and care bundles to include early administration of antibiotics and early mobilization.