Once-Daily Treatments for Methicillin-Susceptible Staphylococcus aureus Bacteremia: Are They Good Enough?

Safety and Efficacy of Ceftriaxone in the Treatment of Methicillin-Susceptible Staphylococcus aureus Bloodstream Infections: A Noninferiority Retrospective Cohort Study

BACKGROUND

Antistaphylococcal penicillins and cefazolin are the treatments of choice for methicillin-susceptible Staphylococcus aureus (MSSA) infections, requiring multiple doses daily. At Parkland, eligible uninsured patients with MSSA bloodstream infections (BSI) receive self-administered outpatient parenteral antimicrobial therapy (S-OPAT). Ceftriaxone was used in a cohort of S-OPAT patients for ease of once-daily dosing.

OBJECTIVE

A retrospective study was conducted to evaluate clinical outcomes for patients discharged with ceftriaxone versus cefazolin to treat MSSA BSI.

METHODS

A retrospective cohort noninferiority study design was used to assess treatment efficacy of ceftriaxone versus cefazolin among Parkland S-OPAT patients treated from April 2012 to March 2020. Demographic, clinical, and treatment-related adverse events data were collected. Clinical outcomes included treatment failure as defined by repeat positive blood culture or retreatment within 6 months, all-cause 30-day readmission rates, and central line-associated bloodstream infection (CLABSI) rates.

RESULTS

Of 368 S-OPAT patients with MSSA BSI, 286 (77.7%) received cefazolin, and 82 (22.3%) received ceftriaxone. Demographics and comorbidities were similar for both groups. There were no treatment failures in the ceftriaxone group compared with 4 (1%) in the cefazolin group (P = 0.58). No difference in 30-day readmission rate between groups was found. The CLABSI rates were lower in ceftriaxone group (2%) compared with cefazolin (11%; P = 0.02). Limitations include retrospective cohort design.

CONCLUSIONS

Ceftriaxone was found to be noninferior to cefazolin in this study. Our findings suggest that ceftriaxone is a safe and effective treatment of MSSA BSI secondary to osteoarticular or skin and soft tissue infections when used in the S-OPAT setting.

POSTER ABSTRACT

OFID on 2018 Nov; 5(Suppl 1): S316: doi: 10.1093/ofid/ofy210.894.

Real time monitoring of Staphylococcus aureus biofilm sensitivity towards antibiotics with isothermal microcalorimetry

Biofilm-associated infections with Staphylococcus aureus are difficult to treat even after administration of antibiotics that according to the standard susceptibility assays are effective. Currently, the assays used in the clinical laboratories to determine the sensitivity of S. aureus towards antibiotics are not representing the behaviour of biofilm-associated S. aureus, since these assays are performed on planktonic bacteria. In research settings, microcalorimetry has been used for antibiotic susceptibility studies. Therefore, in this study we investigated if we can use isothermal microcalorimetry to monitor the response of biofilm towards antibiotic treatment in real-time. We developed a reproducible method to generate biofilm in an isothermal microcalorimeter setup. Using this system, the sensitivity of 5 methicillin-sensitive S. aureus (MSSA) and 5 methicillin-resistant S. aureus (MRSA) strains from different genetic lineages were determined towards: flucloxacillin, cefuroxime, cefotaxime, gentamicin, rifampicin, vancomycin, levofloxacin, clindamycin, erythromycin, linezolid, fusidic acid, co-trimoxazole, and doxycycline. In contrast to conventional assays, our calorimetry-based biofilm susceptibility assay showed that S. aureus biofilms, regardless MSSA or MRSA, can survive the exposure to the maximum serum concentration of all tested antibiotics. The only treatment with a single antibiotic showing a significant reduction in biofilm survival was rifampicin, yet in 20% of the strains, emerging antibiotic resistance was observed. Furthermore, the combination of rifampicin with flucloxacillin, vancomycin or levofloxacin was able to prevent S. aureus biofilm from becoming resistant to rifampicin. Isothermal microcalorimetry allows real-time monitoring of the sensitivity of S. aureus biofilms towards antibiotics in a fast and reliable way.

Outcomes of Outpatient Parenteral Antimicrobial Therapy With Ceftriaxone for Methicillin-Susceptible Staphylococcus aureus Bloodstream Infections-A Single-Center Observational Study

Background

Staphylococcus aureus bloodstream infections (BSIs) are associated with significant morbidity and mortality. Ceftriaxone is convenient for outpatient parenteral antimicrobial therapy (OPAT), but data for this indication are limited.

Methods

Adult patients with methicillin-susceptible Staphylococcus aureus (MSSA) BSI discharged on OPAT with cefazolin, oxacillin, or ceftriaxone for at least 7 days were included. We compared outcomes of ceftriaxone vs either oxacillin or cefazolin. Ninety-day all-cause mortality, readmission due to MSSA infection, and microbiological failure were examined as a composite outcome and compared among groups. Rates of antibiotic switches due to intolerance were assessed.

Results

Of 243 patients included, 148 (61%) were discharged on ceftriaxone and 95 (39%) were discharged on either oxacillin or cefazolin. The ceftriaxone group had lower rates of intensive care unit care, endocarditis, and shorter duration of bacteremia, but higher rates of cancer diagnoses. There was no significant difference in the composite adverse outcome in the oxacillin or cefazolin group vs the ceftriaxone group (18 [19%] vs 31 [21%]; P = .70), comprising microbiological failure (6 [6.3%] vs 9 [6.1%]; P = .94), 90-day all-cause mortality (7 [7.4%] vs 15 [10.1%]; P = .46), and readmission due to MSSA infection (10 [10.5%] vs 13 [8.8%]; P = .65). Antibiotic intolerance necessitating a change was similar between the 2 groups (4 [4.2%] vs 6 [4.1%]; P = .95).

Conclusions

For patients with MSSA BSI discharged on OPAT, within the limitations of the small numbers and retrospective design we did not find a significant difference in outcomes for ceftriaxone therapy when compared with oxacillin or cefazolin therapy.

Intravenous Ceftriaxone Versus Multiple Dosing Regimes of Intravenous Anti-Staphylococcal Antibiotics for Methicillin-Susceptible Staphylococcus aureus (MSSA): A Systematic Review

Background: Methicillin-susceptible Staphylococcus aureus (MSSA) is a common pathogen associated with a range of clinically important infections. MSSA can cause deep-seated infections requiring prolonged courses of intravenous antibiotic therapy to achieve effective resolution. The move toward ambulatory or outpatient delivery of parenteral antibiotics has led to an increase in the use of ceftriaxone as a pragmatic first choice given its advantageous single daily dosing schedule. Objective: To compare the efficacy of once daily ceftriaxone in the treatment of infections due to confirmed or suspected MSSA to multiple dosing regimes of anti-staphylococcal antibiotics. Methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), Database of Abstracts of Reviews of Effects (DARE), Global Health, PubMed, EMBASE and CINAHL for randomised controlled trials as well as prospective and retrospective cohort studies that compared ceftriaxone to any multiple dosing regime of anti-staphylococcal antibiotics. Outcome measures were the proportion of patients with a resolution of infection based on time after initiation of therapy, adverse reactions, recurrence and duration of hospital admission. Results: We included two randomized controlled trials, one prospective observational study and three retrospective cohort studies (643 participants; 246 children, 397 adults). There was no difference in time to resolution of symptoms. The number of adverse reactions, recurrence of bacteraemia and duration of hospital stay were not significantly different between ceftriaxone and other anti-staphylococcal antibiotics. Conclusions: Based on a small number of low-quality studies, ceftriaxone is as effective as multiple dosing regimes for the treatment of infections due MSSA. An appropriately powered randomized trial is required to demonstrate equivalence and cost effectiveness.

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.

Antibiotic-Derived Lipid Nanoparticles to Treat Intracellular Staphylococcus aureus

Intracellular survival of pathogenic bacteria leads to high chances of bacterial persistence and relapse in the bacteria-infected host. However, many antibiotics fail to clear the intracellular bacteria due to their low internalization by cells. In order to increase delivery of antibiotics in cells and eliminate intracellular bacteria, we developed antibiotic-derived lipid nanoparticles. First, we synthesized antibiotic-derived lipid conjugates using two widely used antibiotics including penicillin G (PenG) and levofloxacin (Levo). Then, we formulated them into antibiotic-derived lipid nanoparticles and evaluated their antibacterial effects. We found that penicillin G derived phospholipid nanoparticles (PenG-PL NPs) were able to enhance cellular uptake of penicillin G as compared with free penicillin G and eliminate up to 99.9998% of ~10^8.5 intracellular methicillin sensitive Staphylococcus aureus (S. aureus) in infected A549 cells, a lung epithelial cell line. The PenG-PL NPs showed the potential for inhibiting intracellular S. aureus and are promising to be further studied for in vivo antibacterial applications.