The pathogen Mycoplasma dispar Shows High Minimum Inhibitory Concentrations for Antimicrobials Commonly Used for Bovine Respiratory Disease.

Marco Bottinelli,Elisabetta Stefani,Marianna Merenda,Micaela Picchi,Michele Gastaldelli,Salvatore Catania,Robin A J Nicholas

doi:10.3390/antibiotics9080460

Marco Bottinelli, Elisabetta Stefani + Show 5 more

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https://doi.org/10.3390/antibiotics9080460

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Abstract

Mycoplasma dispar is an overlooked pathogen often involved in bovine respiratory disease (BRD), which affects cattle around the world. BRD results in lost production and high treatment and prevention costs. Additionally, chronic therapies with multiple antimicrobials may lead to antimicrobial resistance. Data on antimicrobial susceptibility to M. dispar is limited so minimum inhibitory concentrations (MIC) of a range of antimicrobials routinely used in BRD were evaluated using a broth microdilution technique for 41 M. dispar isolates collected in Italy between 2011–2019. While all isolates had low MIC values for florfenicol (<1 μg/mL), many showed high MIC values for erythromycin (MIC90 ≥8 μg/mL). Tilmicosin MIC values were higher (MIC50 = 32 μg/mL) than those for tylosin (MIC50 = 0.25 μg/mL). Seven isolates had high MIC values for lincomycin, tilmicosin and tylosin (≥32 μg/mL). More, alarmingly, results showed more than half the strains had high MICs for enrofloxacin, a member of the fluoroquinolone class considered critically important in human health. A time-dependent progressive drift of enrofloxacin MICs towards high-concentration values was observed, indicative of an on-going selection process among the isolates.

Highlights

Mycoplasma dispar, characterized for the first time in 1970 [1], is a mollicute frequently isolated from the respiratory airways of both healthy and pneumonic calves worldwide [2,3,4,5]
M. dispar falls within the M. neurolyticum cluster of the hominis group of Mollicutes, showing a high degree of similarity to M. hyopneumoniae, the cause of enzootic pneumonia in pigs worldwide, and M. ovipneumoniae [6], a respiratory pathogen of small ruminants
Few detailed studies have been carried out to establish the exact role of M. dispar in bovine respiratory disease (BRD) which is a chronic condition affecting beef cattle in feedlots and dairy calves; it is estimated to cost the USA cattle industry alone over US$4 billion in production losses, treatment and prevention [7]

Summary

Introduction

Mycoplasma dispar, characterized for the first time in 1970 [1], is a mollicute frequently isolated from the respiratory airways of both healthy and pneumonic calves worldwide [2,3,4,5]. M. dispar falls within the M. neurolyticum cluster of the hominis group of Mollicutes, showing a high degree of similarity to M. hyopneumoniae, the cause of enzootic pneumonia in pigs worldwide, and M. ovipneumoniae [6], a respiratory pathogen of small ruminants. Experimental infection of calves with M. dispar led to a mild pneumonia [8] but data from the field suggests a more pathogenic role. Of pneumonic calves and only 40% of healthy lungs [3,4] while in Denmark it was found in over half of calf lungs showing either fibrino-necrotising or suppurative bronchopneumonia [9].

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