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

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.

Dynamics of the nasopharyngeal microbiome of apparently healthy calves and those with clinical symptoms of bovine respiratory disease from disease diagnosis to recovery

“…These two Mycoplasma species have been previously identified as opportunistic pathogens related to bovine respiratory disease ( 32 , 33 ). More specifically, M. dispar has been detected in pneumonic cases in cattle and can exhibit a pathogenic phenotype by suppressing the host immune response, and producing hydrogen peroxide and biofilms ( 34 ). Nonetheless, another study identified a high relative abundance of M. dispar in the nasopharynx of apparently healthy heifers after feedlot arrival ( 35 ) similar to the results observed in our study.…”

Evaluating the potential of third generation metagenomic sequencing for the detection of BRD pathogens and genetic determinants of antimicrobial resistance in chronically ill feedlot cattle

“…The frequent co-occurrence of these species is remarkable in that several studies suggest synergism between Mycoplasma sp. and P. multocida [ 31 , 33 , 34 ] as well as a possible initiative role of M. dispar in the development of respiratory tract disease in dairy cattle [ 35 – 38 ]. While the pathogenicity of M. dispar is well described in dairy calves, particularly in countries free of M. bovis , it has received little attention in BRD feedlot studies.…”

“…While the pathogenicity of M. dispar is well described in dairy calves, particularly in countries free of M. bovis , it has received little attention in BRD feedlot studies. However, this could be a consequence of the challenges associated with the fastidious nature of this organism rather than its potential importance in BRD in feedlot cattle [ 38 ]. In this regard, culture-independent approaches like metagenomic sequencing offer the opportunity to expand pathogen detection beyond the more typical predetermined BRD pathogens of interest ( M. haemolytica, P. multocida, H. somni ) for which culture-based techniques are well-established.…”