Staphylococcus aureus nasal carriage in a Moroccan dialysis center and isolates characterization

The Antistaphylococcal Activity of Amoxicillin/Clavulanic Acid, Gentamicin, and 1,8-Cineole Alone or in Combination and Their Efficacy through a Rabbit Model of Methicillin-Resistant Staphylococcus aureus Osteomyelitis

The aim of this research paper is to test the antistaphylococcal effect of 1,8-cineole, amoxicillin/clavulanic acid (AMC), and gentamicin, either separately or in combination against three Staphylococcus aureus strains isolated from patients suffering from osteomyelitis. This activity was tested in vitro by using the microdilution method and the checkerboard assay. The efficacy of these three antibacterial agents was then tested in vivo by using an experimental model of methicillin-resistant S. aureus osteomyelitis in rabbits. This efficacy was assessed after four days of treatment by counting the number of bacteria in the bone marrow. The obtained results in vitro showed that the combination of the AMC with gentamicin did not induce a synergistic effect, whereas the combination of the two antibiotics with 1,8-cineole did. This effect is stronger when AMC is combined with 1,8-cineole as a total synergistic effect was obtained on the three strains used (FIC ≤ 0.5). In vivo, a significant reduction was noted in the number of colonies in the bone marrow when rabbits were treated with AMC associated with either 1,8-cineole or gentamicin compared to rabbits treated with AMC, gentamicin, or 1,8-cineole alone. These results demonstrated that 1,8-cineole showed a synergistic effect in combination with both AMC and gentamicin, which offer possibilities for reducing antibiotic usage. Also, the AMC associated with 1,8-cineole could be used to treat MRSA osteomyelitis.

Reduced pro-inflammatory responses to Staphylococcus aureus bloodstream infection and low prevalence of enterotoxin genes in isolates from patients on haemodialysis

Patients with end-stage renal failure undergo regular haemodialysis (HD) and often develop episodes of Staphylococcus aureus bloodstream infection (BSI), which can re-occur. However, clinically, patients on HD, with S. aureus BSI, respond well to treatment, rarely developing overt signs of sepsis. We investigated the contributions of bacterial virulence and cytokine responses to the clinical course of S. aureus BSI in HD and non-HD patients. Seventy patients were recruited, including 27 (38.6 %) patients on HD. Isolates were spa-typed and virulence and antimicrobial resistance gene carriage was investigated using DNA microarray analysis. Four inflammatory cytokines, IL-6, RANTES, GROγ and leptin, were measured in patient plasma on the day of diagnosis and after 7 days. There was no significant difference in the prevalence of genotypes or antimicrobial resistance genes in S. aureus isolates from HD compared to non-HD patients. The enterotoxin gene cluster (containing staphylococcal enterotoxins seg, sei, sem, sen, seo and seu) was significantly less prevalent among BSI isolates from HD patients compared to non-HD patients. Comparing inflammatory cytokine response to S. aureus BSI in HD patients to non-HD patients, IL-6 and GROγ were significantly lower (p = 0.021 and p = 0.001, respectively) in HD patients compared to other patients on the day of diagnosis and RANTES levels were significantly lower (p = 0.025) in HD patients on day 7 following diagnosis. Lowered cytokine responses in HD patients and a reduced potential for super-antigen production by infecting isolates may partly explain the favourable clinical responses to episodes of S. aureus BSI in HD patients that we noted clinically.

Meta-analysis of methicillin-resistant Staphylococcus aureus colonization and risk of infection in dialysis patients

Patients undergoing dialysis are particularly vulnerable to methicillin-resistant Staphylococcus aureus (MRSA) infections. We performed a meta-analysis of published studies to estimate the prevalence of MRSA colonization in dialysis patients, time trends, and long-term risk of subsequent MRSA infections. Our search of the PubMed and Embase databases returned 5743 nonduplicate citations, from which we identified 38 relevant studies that included data on 5596 dialysis patients. The estimated prevalence of MRSA colonization was 6.2% (95% confidence interval [95% CI], 4.2% to 8.5%). The prevalence increased over time but remained stable after 2000. Stratification of patients according to dialysis modality and setting revealed that 7.2% (95% CI, 4.9% to 9.9%) of patients on hemodialysis were colonized with MRSA compared with 1.3% (95% CI, 0.5% to 2.4%) of patients on peritoneal dialysis (P=0.01), and that a statistically significant difference existed in the percentage of colonized inpatients and outpatients (14.2% [95% CI, 8.0% to 21.8%] versus 5.4% [95% CI, 3.5% to 7.7%], respectively; P=0.04). Notably, the risk of developing MRSA infections increased among colonized hemodialysis patients compared with noncolonized patients (relative risk, 11.5 [95% CI, 4.7 to 28.0]). The long-term (6-20 months) probability of developing a MRSA infection was 19% among colonized hemodialysis patients compared with only 2% among noncolonized patients. In summary, 6.2% of dialysis patients are MRSA colonized, and the average prevalence of colonization has remained stable since 2000. Colonization in hemodialysis patients is associated with increased risk of MRSA infection.