International Society of Cardiovascular Infectious Diseases Guidelines for the Diagnosis, Treatment and Prevention of Disseminated Mycobacterium chimaera Infection Following Cardiac Surgery with Cardiopulmonary Bypass.

Mycobacterial infection-related morbidity and mortality in patients following cardiopulmonary bypass surgery is high and there is a growing need for a consensus-based expert opinion to provide international guidance for diagnosing, preventing and treating in these patients. In this document the International Society for Cardiovascular Infectious Diseases (ISCVID) covers aspects of prevention (field of hospital epidemiology), clinical management (infectious disease specialists, cardiac surgeons, ophthalmologists, others), laboratory diagnostics (microbiologists, molecular diagnostics), device management (perfusionists, cardiac surgeons) and public health aspects.

Mycobacterium immunogenum sp. nov., a novel species related to Mycobacterium abscessus and associated with clinical disease, pseudo-outbreaks and contaminated metalworking fluids: an international cooperative study on mycobacterial taxonomy.

PCR-restriction enzyme pattern analysis of a 439 bp hsp65 gene segment identified 113 unique isolates among non-pigmented rapidly growing mycobacteria (RGM) from clinical and environmental sources that failed to match currently recognized species patterns. This group represented 40% of isolates recovered from bronchoscope contamination pseudo-outbreaks, 0% of disease-associated nosocomial outbreaks and 4% of routine clinical isolates of the Mycobacterium abscessus/Mycobacterium chelonae group submitted to the Mycobacteria/Nocardia laboratory for identification. It is grouped within the Mycobacterium fortuitum complex, with growth in less than 7 d, absence of pigmentation, positive 3-d arylsulfatase reaction and growth on MacConkey agar without crystal violet. It exhibited overlapping biochemical, antimicrobial susceptibility and HPLC characteristics of M. abscessus and M. chelonae. By 16S rRNA gene sequencing, these isolates comprised a homogeneous group with a unique hypervariable region A sequence and differed by 8 and 10 bp, respectively, from M. abscessus and M. chelonae. Surprisingly, this taxon contained two copies of the ribosomal operon, compared with single copies in the two related species. By DNA-DNA hybridization, this new group exhibited <30% homology with recognized RGM species. The name Mycobacterium immunogenum sp. nov. is proposed for this new taxon.

Successful treatment of disseminated Mycobacterium chelonae infection with linezolid.

We describe a 57-year-old man with steroid-dependent myasthenia gravis and progressive ulcerating leg nodules due to clarithromycin-resistant Mycobacterium chelonae. The patient was successfully treated with linezolid.

In vitro activities of linezolid against multiple Nocardia species.

Linezolid was tested by broth microdilution against 140 clinical Nocardia isolates belonging to seven species. The MIC at which 50% of the strains are inhibited (MIC50) and MIC90 for all species other than Nocardia farcinica were 2 and 4 microg/ml. Linezolid is the first antimicrobial agent demonstrated to be active against all Nocardia species.

Activities of linezolid against rapidly growing mycobacteria.

Linezolid is an oxazolidinone available as an oral drug which has activity against most gram-positive bacteria. However, few species of the genus Mycobacterium have been studied. We tested 249 clinical isolates and 10 reference strains of rapidly growing mycobacteria for susceptibility to linezolid by broth microdilution. Clinical species included the Mycobacterium fortuitum group (n = 74), M. abscessus (n = 98), M. chelonae (n = 50), M. mucogenicum (n = 10), and M. fortuitum third biovariant complex (10). The modal MIC for M. mucogenicum was 1.0 microg/ml, and the MIC at which 90% of the isolates tested are inhibited (MIC(90)) was 4 microg/ml; the modal MIC for the M. fortuitum group was 4 microg/ml, and the MIC(90) was 16 microg/ml; the modal MIC for the M. fortuitum third biovariant complex was 4 microg/ml, and the MIC(90) was 8 microg/ml; the modal MIC for M. chelonae was 8 microg/ml, and the MIC(90) was 16 microg/ml; and the modal MIC for M. abscessus was 32 microg/ml, and the MIC(90) was 64 microg/ml. Based on peak levels of linezolid in serum of 15 to 20 microg/ml, we propose the following broth MIC breakpoints for these species: susceptible, < or = 8 microg/ml; moderately susceptible, 16 microg/ml; and resistant, > or =32 microg/ml). These studies demonstrate the excellent potential of linezolid for therapy of rapidly growing mycobacteria.