Mycobacterium helveticum sp. nov., a novel slowly growing mycobacterial species associated with granulomatous lesions in adult swine.

The occurrence of nontuberculous mycobacteria in different hosts and their implication as obligate or opportunistic pathogens remain mainly unclear. Mycobacteriosis in pigs is usually associated with members of the Mycobacterium avium complex and, in particular, with 'Mycobacterium avium subsp. hominissuis'. Here we describe a novel slow-growing mycobacterial species isolated from lymph nodes obtained from two sows housed in different Swiss farms. The animals presented chronic inappetence and mild diarrhoea. Gross pathology revealed focal caseous lymphadenopathy of the mesenteric lymph nodes. Complete genome sequencing of the two isolates from the two sows was performed. The genomes comprised 5.76 Mb and an average nucleotide identity score of 99.97 %. Whole genome sequence, mycolic acid and matrix-assisted laser desorption ionization-time of flight mass spectrometry analyses revealed that the two isolates were not related to any previously described Mycobacterium species. The closest related species was Mycobacterium parmense, a slow-growing scotochromogenic mycobacterium first isolated from a cervical lymph node of a 3-year-old child. The name proposed for the new species is Mycobacterium helveticum sp. nov. and 16-83T (=DSM 109965T= LMG 2019-02457T) is the type strain.

Gentamicin plasma concentrations in hospitalized horses and retrospective minimal inhibitory concentrations of gram-negative equine pathogens.

OBJECTIVES: The optimal dosage regimen of gentamicin in horses is still under investigation. The objectives of this study were to determine gentamicin plasma concentrations in hospitalized horses treated with 10 mg/kg gentamicin (IV, q 24 h) and to determine whether a plasma concentration to minimum inhibitory concentration (MIC) ratio of 10:1 is reached for equine pathogens using this dose. DESIGN: Prospective clinical observational study; retrospective study on MICs of 131 gram-negative bacteria isolated from horses (2012-2015). SETTING: University teaching hospital. ANIMALS: Ninety-eight horses >6 months old, treated with gentamicin for their primary disease, consecutive samples. MEASUREMENTS AND MAIN RESULTS: Plasma concentrations were measured 1 hour (C1h ) and 20 hours (C20h ) after gentamicin administration using fluorescence polarization. Presence of systemic inflammatory response syndrome (SIRS) and azotemia was recorded, as well as the reason for antimicrobial administration (primary disease) and whether administration was prophylactic or therapeutic. The target C1h of ≥20 µg/mL gentamicin was reached in 90% of horses and was sufficient to reach a plasma concentration:MIC of 10:1 in 32 of 131 (24%) of gram-negative aerobic bacteria. A C20h ≤ 2 µg/mL was reached in 97% horses. Therapeutic versus prophylactic administration, primary disease, azotemia, and systemic inflammatory response syndrome were not associated with a failure to reach a desired peak or trough. CONCLUSIONS: The gentamicin dose of 10 mg/kg every 24 hours should be further investigated and safety assessed because a target gentamicin plasma concentration of ≥20 µg/mL was achieved in the majority of cases. Nephrotoxic side effects were not assessed. Individual drug monitoring should be performed because clinical factors are unreliable predictors of plasma concentrations. A gentamicin target concentration of ≥40 µg/mL does not offer additional benefits compared to ≥20 µg/mL, due to the bimodal distribution of resistance in bacterial isolates.