Macrolides and lincosamides in cattle and pigs : Use and development of antimicrobial resistance

Peer reviewe

Driving laboratory standardisation of bacterial culture and antimicrobial susceptibility testing in veterinary clinical microbiology in Europe and beyond.

Globally, antimicrobial resistance is one of the most important public health challenges in which the clinical microbiology laboratory plays a critical role by providing guidance for antimicrobial treatment. Despite the recognition of its importance, there is still a real need for standardized training of clinical microbiologists and harmonisation of diagnostic procedures. This is particularly true for veterinary clinical microbiology where additional challenges exist when microbiologists are trying to fulfil a professional role very similar to their colleagues working in human microbiology laboratories. The specific points that need addressing to improve the outputs of veterinary microbiology laboratories discussed here include 1) harmonisation of methodologies used by veterinary laboratories for antimicrobial susceptibility testing (AST); 2) specific guidelines for interpretation and reporting of AST results for animal pathogens; 3) guidelines for detection of antimicrobial resistance mechanisms in animal isolates; 4) standardisation of diagnostic procedures for animal clinical specimens and 5) the need to train more veterinary clinical microbiology specialists. However, there is now a plan to address these issues led by the European Network for Optimisation of Veterinary Antimicrobial Treatment (ENOVAT) which is bringing together experts in veterinary microbiology, pharmacology, epidemiology and antimicrobial stewardship from Europe and wider afield. ENOVAT is aiming to work with project partners towards standardisation and harmonisation of laboratory methodologies and optimisation of veterinary antimicrobial treatment. Ultimately, the project may provide a mechanism for standardisation and harmonisation of veterinary clinical microbiology methodologies, which could then be used as a template for implementation at a wider international level

Occurrence and characterization of livestock-associated methicillin-resistant Staphylococcus Aureus

Methicillin resistant Staphylococcus aureus causes a wide range of severe and economically-important diseases in humans and animals. Different types of MRSA are associated with different hosts but the transmission occurs between them. The aim of this study was to investigate possible spread of MRSA among livestock in Lithuania and to determine their types and antimicrobial resistance. Cattle (n=120), horses (n=120) pigs (n=160) and poultry (pooled samples, n=120) were tested for MRSA prevalence. From a total of 520 samples tested, 4 isolates of methicillin resistant Staphylococcus aureus (0.8 %) were identified. All isolates were obtained from the finisher pigs delivered from the same farm complex. Multiplex PCR demonstrated presence of mecA, nuc and 16S genes in all tested cultures. All MRSA isolates were identified as ST398. Sequencing of spa genes and SCCmec typing revealed that all strains belonged to the spa type t011 and SCCmec V. PFGE revealed two different clones among the isolates. Susceptibility testing revealed resistance to tetracycline in all MRSA isolates attributed to tetK and tetM genes. All tested isolates were resistant to erythromycin owing to the presence of ermB gene as well as resistances to azithromycin, clindamycin and quinupristin/dalfopristin. One isolate was resistant to trimethoprim/sulfamethoxazole and carried the resistance gene dfrK while the other isolate was resistant to the combination of amoxicillin and clavulanic acid. All of the isolates were susceptible to fluoroquinolones, cefotaxime, chloramphenicol, fosfomycin, fusidic acid, gentamicin, linezolid, vancomycin, mupirocin and teicoplanin

Occurrence and characterization of livestock-associated methicillin-resistant Staphylococcus Aureus

Methicillin resistant Staphylococcus aureus causes a wide range of severe and economically-important diseases in humans and animals. Different types of MRSA are associated with different hosts but the transmission occurs between them. The aim of this study was to investigate possible spread of MRSA among livestock in Lithuania and to determine their types and antimicrobial resistance. Cattle (n=120), horses (n=120) pigs (n=160) and poultry (pooled samples, n=120) were tested for MRSA prevalence. From a total of 520 samples tested, 4 isolates of methicillin resistant Staphylococcus aureus (0.8 %) were identified. All isolates were obtained from the finisher pigs delivered from the same farm complex. Multiplex PCR demonstrated presence of mecA, nuc and 16S genes in all tested cultures. All MRSA isolates were identified as ST398. Sequencing of spa genes and SCCmec typing revealed that all strains belonged to the spa type t011 and SCCmec V. PFGE revealed two different clones among the isolates. Susceptibility testing revealed resistance to tetracycline in all MRSA isolates attributed to tetK and tetM genes. All tested isolates were resistant to erythromycin owing to the presence of ermB gene as well as resistances to azithromycin, clindamycin and quinupristin/dalfopristin. One isolate was resistant to trimethoprim/sulfamethoxazole and carried the resistance gene dfrK while the other isolate was resistant to the combination of amoxicillin and clavulanic acid. All of the isolates were susceptible to fluoroquinolones, cefotaxime, chloramphenicol, fosfomycin, fusidic acid, gentamicin, linezolid, vancomycin, mupirocin and teicoplanin

Driving Laboratory Standardization of Bacterial Culture and Antimicrobial Susceptibility Testing in Veterinary Clinical Microbiology in Europe and Beyond

Globally, antimicrobial resistance is one of the most important public health challenges in which the clinical microbiology laboratory plays a critical role by providing guidance for antimicrobial treatment. Despite the recognition of its importance, there is still a real need for the standardized training of clinical microbiologists and harmonization of diagnostic procedures. This is particularly true for veterinary clinical microbiology, where additional challenges exist when microbiologists are trying to fulfill a professional role very similar to that of their colleagues working in human microbiology laboratories. The specific points that need addressing to improve the outputs of veterinary microbiology laboratories discussed here include (i) harmonization of methodologies used by veterinary laboratories for antimicrobial susceptibility testing (AST); (ii) specific guidelines for interpretation and reporting of AST results for animal pathogens; (iii) guidelines for detection of antimicrobial resistance mechanisms in animal isolates; (iv) standardization of diagnostic procedures for animal clinical specimens; and (v) the need to train more veterinary clinical microbiology specialists. However, there is now a plan to address these issues, led by the European Network for Optimization of Veterinary Antimicrobial Treatment (ENOVAT), which is bringing together experts in veterinary microbiology, pharmacology, epidemiology, and antimicrobial stewardship from Europe and wider afield. ENOVAT is aiming to work with project partners toward standardization and harmonization of laboratory methodologies and optimization of veterinary antimicrobial treatment. Ultimately, the project may provide a mechanism for standardization and harmonization of veterinary clinical microbiology methodologies that could then be used as a template for implementation at a wider international level

Staphylococcus aureus CC398:Host Adaptation and Emergence of Methicillin Resistance in Livestock

Since its discovery in the early 2000s, methicillin-resistant Staphylococcus aureus (MRSA) clonal complex 398 (CC398) has become a rapidly emerging cause of human infections, most often associated with livestock exposure. We applied whole-genome sequence typing to characterize a diverse collection of CC398 isolates (n = 89), including MRSA and methicillin-susceptible S. aureus (MSSA) from animals and humans spanning 19 countries and four continents. We identified 4,238 single nucleotide polymorphisms (SNPs) among the 89 core genomes. Minimal homoplasy (consistency index = 0.9591) was detected among parsimony-informative SNPs, allowing for the generation of a highly accurate phylogenetic reconstruction of the CC398 clonal lineage. Phylogenetic analyses revealed that MSSA from humans formed the most ancestral clades. The most derived lineages were composed predominantly of livestock-associated MRSA possessing three different staphylococcal cassette chromosome mec element (SCCmec) types (IV, V, and VII-like) including nine subtypes. The human-associated isolates from the basal clades carried phages encoding human innate immune modulators that were largely missing among the livestock-associated isolates. Our results strongly suggest that livestock-associated MRSA CC398 originated in humans as MSSA. The lineage appears to have undergone a rapid radiation in conjunction with the jump from humans to livestock, where it subsequently acquired tetracycline and methicillin resistance. Further analyses are required to estimate the number of independent genetic events leading to the methicillin-resistant sublineages, but the diversity of SCCmec subtypes is suggestive of strong and diverse antimicrobial selection associated with food animal production. IMPORTANCE Modern food animal production is characterized by densely concentrated animals and routine antibiotic use, which may facilitate the emergence of novel antibiotic-resistant zoonotic pathogens. Our findings strongly support the idea that livestock-associated MRSA CC398 originated as MSSA in humans. The jump of CC398 from humans to livestock was accompanied by the loss of phage-carried human virulence genes, which likely attenuated its zoonotic potential, but it was also accompanied by the acquisition of tetracycline and methicillin resistance. Our findings exemplify a bidirectional zoonotic exchange and underscore the potential public health risks of widespread antibiotic use in food animal production