Monitoring Mycoplasma bovis Diversity and Antimicrobial Susceptibility in Calf Feedlots Undergoing a Respiratory Disease Outbreak

Abstract

Bovine respiratory diseases (BRD) are widespread in veal calf feedlots. Several pathogens are implicated, both viruses and bacteria, one of which, Mycoplasma bovis, is under-researched. This worldwide-distributed bacterium has been shown to be highly resistant in vitro to the main antimicrobials used to treat BRD. Our objective was to monitor the relative prevalence of M. bovis during BRD episodes, its diversity, and its resistance phenotype in relation to antimicrobial use. For this purpose, a two-year longitudinal follow-up of 25 feedlots was organized and 537 nasal swabs were collected on 358 veal calves at their arrival in the lot, at the BRD peak and 4 weeks after collective antimicrobial treatments. The presence of M. bovis was assessed by real-time PCR and culture. The clones isolated were then subtyped (polC subtyping and PFGE analysis), and their susceptibility to five antimicrobials was determined. The course of the disease and the antimicrobials used had no influence on the genetic diversity of the M. bovis strains: The subtype distribution was the same throughout the BRD episode and similar to that already described in France, with a major narrowly-variable subtype circulating, st2. The same conclusion holds for antimicrobial resistance (AMR) phenotypes: All the clones were already multiresistant to the main antimicrobials used (except for fluoroquinolones) prior to any treatments. By contrast, changes of AMR phenotypes could be suspected for Pasteurellaceae in two cases in relation to the treatments registered.

Addressing the Antimicrobial Resistance of Ruminant Mycoplasmas Using a Clinical Surveillance Network

“…However, because some clinical signs, age classes or production types are dominant in Vigimyc-sampled animals ( Table 1 ), they are also dominant in the AST panel. We remain alert with respect to a potential bias and for M. bovis we have already shown the absence of influence of (i) tissue tropism ( 17 ), or (ii) sampling time post antimicrobial therapy ( 23 ) on AMR.…”

“…Between 2014 and 2019, the preservation rate allowed a first-line conservation of 414 cultures out of 465 identified per year on average (Table 1). After several quality controls, isolates derived from these cultures have regularly been included in various studies on epidemiology [see for example (23)], method validation (24) or mycoplasma biology (25). In the last decade, this collection has also been a valuable source of material for studying the AMR of French isolates over time (15)(16)(17)22).…”

Mycoplasma bovis in Nordic European Countries: Emergence and Dominance of a New Clone

“…For instance, polC subtyping was insufficiently discriminatory for recent isolates, generating only two subtypes, with the majority of isolates assigned to st3, while st2 isolates appeared restricted to France or the Netherlands. In France, st2 is currently the main clone in the circulation, with st3 constituting a maximum of 20% of the M. bovis population to date [38]. The st2 and st3 subtypes were further subdivided into 16 subtypes by MLST-1a [26] (Table S1), indicating that MLSTs better inform international epidemiological trends.…”

Antimicrobial Susceptibility of Mycoplasma bovis Isolates from Veal, Dairy and Beef Herds

“…In recent years, a decrease in the antimicrobial susceptibility of M. bovis to various antimicrobial classes targeting protein synthesis (e.g., phenicols, tetracyclines, lincosamides and macrolides) and DNA synthesis (e.g., fluoroquinolones) has been reported in different countries [ 4 , 5 , 6 , 7 , 8 , 9 ]. Especially for macrolides, high percentages of resistant M. bovis isolates are reported, while fluoroquinolones remain the most effective antimicrobial in vitro in most countries [ 5 , 9 , 10 , 11 ], except for Spain and Italy [ 6 , 7 ]. Geographical differences in the antimicrobial susceptibility of M. bovis, as well as differences between strains isolated from various predilection sites, such as the joint, udder and lung, have been described [ 5 , 10 , 12 ].…”

“…If production-specific antimicrobial susceptibility exists for M. bovis , it might be necessary to adjust M. bovis treatment guidelines to specific production systems. Additionally, whether antimicrobial resistance is associated with specific genetic strains is not clear, as some studies observed no association between genetic subtypes based on the polC subtyping scheme [ 11 ], while others did for lincosamides and macrolides [ 9 ]. With whole genome sequencing (WGS) becoming more popular and commercially available for identification and strain typing [ 16 , 17 , 18 , 19 ], it might be helpful to determine whether phenotypic antimicrobial susceptibility patterns are associated with genomic clusters of M. bovis .…”