Abstract
Mycoplasma bovis is an important bovine pathogen causing pneumonia, mastitis, and arthritis and is responsible for major economic losses worldwide. In the absence of an efficient vaccine, control of M. bovis infections mainly relies on antimicrobial treatments, but resistance is reported in an increasing number of countries. To address the situation in Spain, M. bovis was searched in 436 samples collected from beef and dairy cattle (2016–2019) and 28% were positive. Single-locus typing using polC sequences further revealed that two subtypes ST2 and ST3, circulate in Spain both in beef and dairy cattle, regardless of the regions or the clinical signs. Monitoring of ST2 and ST3 isolates minimum inhibitory concentration (MIC) to a panel of antimicrobials revealed one major difference when using fluoroquinolones (FQL): ST2 is more susceptible than ST3. Accordingly, whole-genome sequencing (WGS) further identified mutations in the gyrA and parC regions, encoding quinolone resistance-determining regions (QRDR) only in ST3 isolates. This situation shows the capacity of ST3 to accumulate mutations in QRDR and might reflect the selective pressure imposed by the extensive use of these antimicrobials. MIC values and detection of mutations by WGS also showed that most Spanish isolates are resistant to macrolides, lincosamides, and tetracyclines. Valnemulin was the only one effective, at least in vitro, against both STs.
Highlights
Isolated in the early 60s, Mycoplasma bovis is an important bovine pathogen that has a major economic impact on the global cattle industry [1,2]
M. bovis was mainly detected in feedlot calves (81/183) and to a lesser extent in pasture-raised animals (3/22) housed in 26 different farms from 5 Spanish regions
This pathogenic species was detected in animals suffering from respiratory infections and/or arthritis (44/80), and in asymptomatic carriers (40/125)
Summary
Isolated in the early 60s, Mycoplasma bovis is an important bovine pathogen that has a major economic impact on the global cattle industry [1,2]. In the absence of an efficient vaccine, the control of M. bovis infections mainly relies on antimicrobial treatments [4]. Many countries have reported that the in vitro antimicrobial sensitivity of M. bovis isolates has been dramatically reduced [5,6,7,8,9,10,11,12,13,14]. M. bovis belongs to the class Mollicutes, a large group of wall-less bacteria with reduced genome and limited metabolic capacities, but a remarkable adaptive potential [15,16]. Treatment with ß-lactams, Pathogens 2020, 9, 545; doi:10.3390/pathogens9070545 www.mdpi.com/journal/pathogens
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