Commensal Bacteria Augment Staphylococcus aureus septic Arthritis in a Dose-Dependent Manner

Background

Septic arthritis is considered one of the most dangerous joints diseases and is mainly caused by the Gram-positive bacterium Staphylococcus aureus (S. aureus). Human skin commensals are known to augment S. aureus infections. The aim of this study was to investigate if human commensals could augment S. aureus-induced septic arthritis.

Method

NMRI mice were inoculated with S. aureus alone or with a mixture of S. aureus together with either of the human commensal Staphylococcus epidermidis (S. epidermidis) or Streptococcus mitis (S. mitis). The clinical, radiological and histopathological changes due to septic arthritis were observed. Furthermore, the serum levels of chemokines and cytokines were assessed.

Results

Mice inoculated with a mixture of S. aureus and S. epidermidis or S. mitis developed more severe and frequent clinical arthritis compared to mice inoculated with S. aureus alone. This finding was verified pathologically and radiologically. Furthermore, the ability of mice to clear invading bacteria in the joints but not in kidneys was hampered by the bacterial mixture compared to S. aureus alone. Serum levels of monocyte chemoattractant protein 1 were elevated at the early phase of disease in the mice infected with bacterial mixture compared with ones infected with S. aureus alone. Finally, the augmentation effect in septic arthritis development by S. epidermidis was bacterial dose-dependent.

Conclusion

The commensal bacteria dose-dependently augment S. aureus-induced septic arthritis in a mouse model of septic arthritis.

Trends in antimicrobial resistance among bacteria causing septic arthritis in adults in a single center: A 15-years retrospective analysis

Septic arthritis (SA) is commonly associated with Staphylococcal or Streptococcal infections. Overtime, there has been a global increase in the distribution of antimicrobial resistance within both Gram-positive bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and Gram-negative bacteria such as extended-spectrum beta-lactamase (ESBL) positive Enterobacteriacea. The aim of this study was to determine whether this change in epidemiology similarly affected the distribution of resistant pathogens causing SA. The study was conducted at the Shaare Zedek Medical Center in Jerusalem, Israel. All adult patients diagnosed with SA during 2002-2016 were included in the cohort. Antimicrobial resistance trends were examined over three periods: 2002-2009, 2010-2013, and 2014-2016. Of 85 patients with SA, mean age of patients was 66.8 (± 20.3) years, with male predominance (n = 62, 66%). Most SA cases involved native knee joints and more than 85% (n = 80) were acquired in the community. The most common isolates were S. aureus (n = 38, 45%) and beta-hemolytic streptococci (n = 13, 15%). MRSA SA was diagnosed in 8% of all SA cases (n = 7). An increasing, although non-significant trend in MRSA SA was observed during the study period (p = 0.3). Gram-negative infections were uncommon (n = 14). No ESBL-positive or carbapenem-resistant Enterobacteriacea were detected. Over a 15-year study period, no significant increase in resistant pathogens causing SA was observed. In the era of antibiotic stewardship, these results strengthen our practice of administering narrow-spectrum antimicrobials empirically for SA. However, our findings cannot be generalized to regions with higher rates of MRSA in the community.

Septic arthritis due to oral streptococci following intra-articular injection: A case series

Oral streptococcal species are a rare cause of septic arthritis. We describe 4 cases of septic arthritis due to oral streptococcal species following joint injection. The routine use of face masks during joint injection may prevent this rare but serious complication.

Endophthalmitis following intravitreal anti-vascular endothelial growth factor (VEGF) injection: a comprehensive review

The purpose of this review is to report and summarize previously reported studies and assess many of the individual steps of the intravitreal injection procedure's possible effect on the prevention of endophthalmitis. The pooled endophthalmitis rate from 20 large retrospective case series of anti-VEGF injections was 144/510,396 (0.028%; 1/3,544). Injections may be performed in an office-based location or in an operating room (OR) and low rates of endophthalmitis can be achieved in either location with careful attention to asepsis. Pre- or post-injection topical antibiotics have not been shown to be effective, and could select for more virulent microorganisms. Povidone-iodine prior to injection is accepted as the gold-standard antiseptic agent, but aqueous chlorhexidine may be an alternative. Antisepsis before and after gel or subconjunctival anesthetic is suggested. The preponderance of Streptococcal infections after intravitreal injection is discussed, including the possible role of aerosolization, which can be minimized by using face masks or maintaining silence. As with other invasive procedures in medicine, the use of sterile gloves, following adequate hand antisepsis, may be considered. Control of the eyelashes and lid margin is required to avoid contamination of the needle, but this can be achieved with or without a speculum. Techniques to minimize vitreous reflux have not been shown to reduce the risk of endophthalmitis. Same day bilateral injections should be performed as two separate procedures, preferably using drug from different lots, especially when using compounded drugs.