Association of Vancomycin MIC and Molecular Characteristics with Clinical Outcomes in Methicillin-Susceptible Staphylococcus aureus Acute Hematogenous Osteoarticular Infections in Children

Abstract

Strains of methicillin-resistant (MRSA), particularly those belonging to the USA300 pulsotype, have been well described to cause severe osteoarticular infections (OAIs). A vancomycin MIC of ≥1.5 μg/ml has been demonstrated to contribute to disease severity in adults with MRSA and even methicillin-susceptible (MSSA) bacteremia. Little data exist describing the outcomes of MSSA OAIs in terms of molecular characteristics and vancomycin MIC. All patients/isolates were chosen from a surveillance study at Texas Children's Hospital (TCH). OAI isolates were identified from 2011 to 2016 and subjected to vancomycin Etests, pulsed-field gel electrophoresis (PFGE), and PCR to determine Panton-Valentine leucocidin (PVL) production and group. Two hundred fifty-two cases of OAI were identified; 183 cases were MSSA (72.6%). During the study period, a decrease in the proportion of cases secondary to MRSA was observed, declining from 37.8% to 15.9% ( = 0.02). Of the MSSA isolates, 26.2% and 23.5% were USA300 and PVL positive, respectively. An increase in the proportion of MSSA isolates with a vancomycin MIC of ≥1.5 μg/ml occurred in the study period ( = 0.004). In MSSA, an elevated vancomycin MIC was associated with multiple surgical procedures and venous thromboses, even when adjusting for empirical β-lactam use. An increase in vancomycin MIC was noted among isolates belonging to group 4 during the study period. Methicillin resistance is declining among OAI isolates at TCH. Simultaneously, vancomycin Etest MICs are increasing among MSSA isolates. Vancomycin MICs of ≥2 μg/ml are associated with adverse clinical outcomes in MSSA irrespective of antibiotic choice, suggesting that this may be a surrogate for organism virulence.

Declining prevalence of Methicillin-resistant Staphylococcus aureus septic arthritis and osteomyelitis in children: implications for treatment

“…Traditionally, MRSA bone and joint infections are considered more severe leading to greater morbidity than those with MSSA infections. (8,12,15) We found MRSA infections were associated with higher inflammatory markers and a longer length of hospitalization compared to MSSA infections, but contrary to many other studies, we did not find any significant differences in the percentage of patients with severe disease sequelae such as a subperiosteal abscess after adjusting for potential confounders. An et al (22) found no significant differences in inflammatory markers or length of hospitalization between MRSA and MSSA infections.…”

“…(23,24) It is most often produced by MRSA strains but has also been recently detected in some MSSA strains associated with more severe infections and worse outcomes. (15) Consistent with several recent studies, we found that musculoskeletal infections caused by MSSA in our community have been gradually increasing during our 8-year study period coinciding with a decline in MRSA prevalence. MSSA accounted for 35.9% of isolates in our study in 2009 and increased to 54.5% in 2016.…”

“…(13) However, more recently studies have shown a decrease in the proportion of S. aureus infectionscaused by MRSA. (14)(15)(16)(17) The changing epidemiology of these infections in some areas may necessitate a change in empiric antibiotic therapies. The Infectious Diseases Society of America recommends intravenous vancomycin for the treatment of children with acute hematogenous MRSA osteomyelitis and septic arthritis;…”

Declining Prevalence of Methicillin-Resistant Staphylococcus aureus Septic Arthritis and Osteomyelitis in Children: Implications for Treatment

“…However, more recently studies have shown a decrease in the proportion of S. aureus infections caused by MRSA [14][15][16][17].…”

The Effects of Thyme on IL-6 Level and the Bacterial Count in the Brain and Spleen of Mice Infected by Methicillin-Resistant Staphylococcus aureus (MRSA)

“…Amoxicillin is an antibiotic known to be resistant to Staphylococcus aureus. In this study, Amoxicillin was used to observe the effectiveness of amoxicillin combined with thyme in eliminating MRSA bacteria (3).…”