Answer to photo quiz: Coinfection with Mycobacterium marinum and M. Ulcerans

The patient’s pus stain showed unstained organisms in the Gram stain (see Fig. 1C in the photo quiz), which were positive by acid-fast staining (see Fig. 1D in the photo quiz). Tissue and pus specimens were cultured at 32°C by inoculating the sediment on LJ solid medium and in a mycobacterial growth indicator tube (MGIT) (Becton, Dickinson, Sparks, MD). The cultures grew acid-fast bacilli (AFB) after 4 weeks for the pus specimen and 8 weeks for the tissue specimen. Two groups of mycobacterial colonies were identified. The first group (at 4 weeks) contained colonies that were creamy in color and turned yellow when exposed to light (photochromogenic), while the second group of colonies (at 8 weeks) appeared yellow and rough, with a welldemarcated edge. The organisms were later identified as Mycobacterium marinum and M. ulcerans, respectively (1). DNA extracted from pus and tissue samples were evaluated by PCR targeting the 16S rRNA gene and by the IS2404 insertion elements. PCR targeting the 16S rRNA gene confirmed Mycobacterium species most closely matching M. marinum and/or M. ulcerans. The sequences of the IS2404 amplicon were identical to those from M. ulcerans. Coinfections due to M. marinum and M. ulcerans, thus, were diagnosed based on cultures (M. marinum and M. ulcerans) and PCR primers specific for M. ulcerans. M. marinum and M. ulcerans were subjected to antimicrobial susceptibility testing (AST) using a broth microdilution susceptibility test (2), and both organisms were susceptible to clarithromycin, doxycycline, moxifloxacin, and rifampin. The patient was empirically treated with rifampin, clarithromycin, and streptomycin together with multiple surgical debridements of his left index finger, which resulted in a significant reduction of the inflammation and resolution of the abscess

Photo quiz: A 53-year-old Thai man with progressive swelling of the left index finger

Apreviously healthy 53-year-old Thai man living in central Thailand (Pathum Thani) presented with progressive swelling of his left index finger for 4 months. He worked at an advertising company, and his hobbies included gardening and decorating corals at his home. The swelling site was located where he had been bitten by an ant while gardening near a pond

Eradication of carriage with methicillin-resistant Staphylococcus aureus: determinants of treatment failure

Background: Using data from an observational study in which the effectiveness of a guideline for eradication of methicillin-resistant Staphylococcus aureus (MRSA) carriage was evaluated, we identified variables that were associated with treatment failure. Methods: A multivariate logistic regression model was performed with subgroup analyses for uncomplicated and complicated MRSA carriage (the latter including MRSA infection, skin lesions, foreign-body material, mupirocin resistance and/or exclusive extranasal carriage) and for those treated according to the guideline (i.e. mupirocin nasal ointment and chlorhexidine soap solution for uncomplicated carriage, in combination with two oral antibiotics for complicated carriage). Results: Six hundred and thirteen MRSA carriers were included, of whom 333 (54%) had complicated carriage; 327 of 530 patients (62%) with known complexity of carriage were treated according to the guideline with an absolute increase in treatment success of 20% (95% confidence interval 12%-28%). Among those with uncomplicated carriage, guideline adherence [adjusted odds ratio (OR alpha) 7.4 (1.7-31.7)], chronic pulmonary disease [OR alpha 44 (2.9-668)], throat carriage [OR alpha 2.9 (1.4-6.1)], perineal carriage [OR alpha 2.2 (1.1-4.4)] and carriage among household contacts [OR alpha 5.6 (1.2-26)] were associated with treatment failure. Among those with complicated carriage, guideline adherence was associated with treatment success [OR alpha 0.2 (0.1-0.3)], whereas throat carriage [OR alpha 4.4 (2.3-8.3)] and dependence in activities of daily living [OR alpha 3.6 (1.4-8.9)] were associated with failure. Conclusions: Guideline adherence, especially among those with complicated MRSA carriage, was associated with treatment success. Adding patients with extranasal carriage or dependence in daily self-care activities to the definition of complicated carriage, and treating them likewise, may further increase treatment success.Antimicrobial treatment and prevention of infection

Interactions of Staphylococci with Osteoblasts and Phagocytes in the Pathogenesis of Implant-Associated Osteomyelitis

In spite of great advancements in the field of biomaterials and in surgical techniques, the implant of medical devices is still associated with a high risk of bacterial infection. Implant-associated osteomyelitis is a deep infection of bone around the implant. The continuous inflammatory destruction of bone tissues characterizes this serious bone infectious disease. Staphylococcus aureus and Staphylococcus epidermidis are the most prevalent etiologic agents of implant-associated infections, together with the emerging pathogen Staphylococcus lugdunensis. Various interactions between staphylococci, osteoblasts, and phagocytes occurring in the pen-prosthesis environment play a crucial role in the pathogenesis of implant-associated osteomyelitis. Here we focus on two main events: internalization of staphylococci into osteoblasts, and bacterial interactions with phagocytic cells