Species Identification and Antimicrobial Susceptibility of Mycobacterial Isolates from Dogs and Cats

  1. Sreekumari Rajeev
  2. Jaclyn Azelby
  3. Porsha Reed
  4. Rebekah Jones
  5. Rajeev V. Nair
  6. Brian Johnson

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Abstract

Nontuberculous Mycobacterium (NTM) species are increasingly recognized as opportunistic pathogens in companion animals, yet data on species distribution and antimicrobial resistance remain limited. The goal of this study was to evaluate species identification methods and determine antimicrobial susceptibility profiles of NTM isolates from cats and dogs submitted to the University of Tennessee veterinary diagnostic laboratory. Twenty-nine NTM isolates (25 feline, 4 canine) collected between 2016 and 2022 were cultured and identified using MALDI-TOF MS and 16S rRNA sequencing. Antimicrobial susceptibility testing (AST) was performed by broth microdilution. Most isolates (27/29) were rapidly growing mycobacteria from skin or wound samples. Combined MALDI-TOF and sequencing identified 11 isolates within the Mycobacterium fortuitum complex, 10 as M. smegmatis, 4 within the M. abscessus group, and one each as M. mucogenicum and M. farcinogenes. MALDI-TOF failed to identify four isolates, including two slow-growing strains. AST revealed consistent susceptibility to amikacin and moxifloxacin, while resistance was highest to doxycycline (44%), clarithromycin (37%), and tobramycin (33%). Rapidly growing NTM predominates in feline cutaneous infections, with species-specific resistance patterns underscoring the need for accurate identification and AST to guide therapy.

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  1. Access Microbiology

    Overall, this is a very interesting paper and an interesting read. Please find some minor amendments that would improve the article. Abstract: The wording is a bit confusing on the isolate numbers. 29 isolates collected. 11 M. fortuitum + 10 M. smegmatis + 4 M. abscessus + 1 M. mucogenicum +1 M. farcinogenes = 27 As per S1, there is identification information on all 29. Perhaps you are only discussing the rapid growers, and this should be clarified if so. Introduction: Please break introduction into paragraphs. Suggested starts of paragraphs are Line 60, new paragraph starts at ‘In contrast..’. Line 67, new paragraph starts at ‘However…’ Line 77, new paragraph starts at ‘Despite..’ Main text: Line 74 – Please provide references for molecular methods such as 16s being the gold standard for definitive identification. Line 121 – Is there a reason why 2 slow-growing isolates, if they can also cause infection in companion animals? Line 149 – Please provide reference for CLSI M24 guidelines. Line 197 – Italicise erm. Please break discussion into paragraphs. Suggested starts of paragraphs are Line 190, new paragraph starts at ‘In contrast …’ Line 202, new paragraph starts at ‘Our use of ..’ Line 213, new paragraph starts at ‘Future work..’ Supplementary material: S1 – Table isolate description. • Some columns are hidden (A/B). Please remove any unused columns. • Column C is unnamed and ambiguous. Please clarify name of column and number format as it is unclear why there are multiple organisms numbered 8. • Column L. It is unclear which is the colony characteristic at 72 hours or 1 week. Please clarify this. • Please group organisms as per the abstract (11 M. fortuitum, 10 M. smegmatis, 4 M. abscessus, 1 M. mucogenicum and 1 M. farcinogenes S2 – Table AST o Correct spelling is Cefoxitin. o Correct spelling is Ciprofloxacin

  2. Version published to 10.1099/acmi.0.001188.v1 on Access Microbiology