A Field Guide to Pandemic, Epidemic and Sporadic Clones of Methicillin-Resistant Staphylococcus aureus

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) have become a truly global challenge. In addition to the long-known healthcare-associated clones, novel strains have also emerged outside of the hospital settings, in the community as well as in livestock. The emergence and spread of virulent clones expressing Panton-Valentine leukocidin (PVL) is an additional cause for concern. In order to provide an overview of pandemic, epidemic and sporadic strains, more than 3,000 clinical and veterinary isolates of MRSA mainly from Germany, the United Kingdom, Ireland, France, Malta, Abu Dhabi, Hong Kong, Australia, Trinidad & Tobago as well as some reference strains from the United States have been genotyped by DNA microarray analysis. This technique allowed the assignment of the MRSA isolates to 34 distinct lineages which can be clearly defined based on non-mobile genes. The results were in accordance with data from multilocus sequence typing. More than 100 different strains were distinguished based on affiliation to these lineages, SCCmec type and the presence or absence of PVL. These strains are described here mainly with regard to clinically relevant antimicrobial resistance- and virulence-associated markers, but also in relation to epidemiology and geographic distribution. The findings of the study show a high level of biodiversity among MRSA, especially among strains harbouring SCCmec IV and V elements. The data also indicate a high rate of genetic recombination in MRSA involving SCC elements, bacteriophages or other mobile genetic elements and large-scale chromosomal replacements

A Field Guide to Pandemic, Epidemic and Sporadic Clones of Methicillin-Resistant Staphylococcus aureus

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) have become a truly global challenge. In addition to the long-known healthcare-associated clones, novel strains have also emerged outside of the hospital settings, in the community as well as in livestock. The emergence and spread of virulent clones expressing Panton-Valentine leukocidin (PVL) is an additional cause for concern. In order to provide an overview of pandemic, epidemic and sporadic strains, more than 3,000 clinical and veterinary isolates of MRSA mainly from Germany, the United Kingdom, Ireland, France, Malta, Abu Dhabi, Hong Kong, Australia, Trinidad & Tobago as well as some reference strains from the United States have been genotyped by DNA microarray analysis. This technique allowed the assignment of the MRSA isolates to 34 distinct lineages which can be clearly defined based on non-mobile genes. The results were in accordance with data from multilocus sequence typing. More than 100 different strains were distinguished based on affiliation to these lineages, SCCmec type and the presence or absence of PVL. These strains are described here mainly with regard to clinically relevant antimicrobial resistance- and virulence-associated markers, but also in relation to epidemiology and geographic distribution. The findings of the study show a high level of biodiversity among MRSA, especially among strains harbouring SCCmec IV and V elements. The data also indicate a high rate of genetic recombination in MRSA involving SCC elements, bacteriophages or other mobile genetic elements and large-scale chromosomal replacements

Genetic Basis, Transferability And Linkage Of Streptomycin And Sulphonamide Resistance Genes In Escherichia Coli From Food Animals In Kenya

The genetic basis and transferability of streptomycin and sulphonamide resistance was studied in 23 Escherichia coli isolates from food animals in Kenya. Physical linkage of the streptomycin resistance gene strA with sulphonamide resistance gene sul2 was investigated by PCR and confirmed by sequencing. Two small plasmids of 6 kb (pSSGK1) and 8 kb, (pSSTGK1) identified by transformation to mediate resistance to at least streptomycin and sulphonamide were restricted in order to define their relatedness. Their restriction maps were compared to one another and with the maps of other plasmids from E. coli known to mediate these resistance properties. Streptomycin resistance was based on the expression of the strA, strB and/or aadA1 genes, while sulphonamide resistance was encoded by the sul2 or sul1 gene. The strA, strB and sul2 genes were transferable via conjugation and transformation. Physically linked sul2 and strA genes were present in both plasmids pSSGK1 and pSSTGK1. The plasmids pSSGK1 and pSSTGK1 were different from each other, but similar respectively to sulphonamide/streptomycin and sulphonamide/streptomycin/tetracycline resistance plasmids described previously in uropathogenic E. coli from humans. Conjugation of plasmids encoding streptomycin and sulphonamide resistance may be one mechanism for the wide dissemination and persistence of these resistances among food animal E. coli in Kenya. Physical linkage of the plasmid-borne strA and sul2 genes would facilitate the spread of these genes by co-selection during selective pressure imposed by the use either of the two antimicrobials and highlights the need for the prudent use of streptomycin or sulphonamides in animal husbandry.La base génétique et la transférabilité de la résistance à la streptomycine et au sulfamide ont été étudiées chez 23 souches de Escherichia coli issues d'aliments d'origine animale au Kenya. Le lien physique du gène strA de résistance à la streptomycine avec le gène sul2 de résistance au sulfamide a été examiné par PCR et confirmé par séquençage. Deux petits plasmides de 6 kb (pSSGK1) et de 8 kb (pSSTGK1) identifiés par transformation pour modifier la résistance au moins à la streptomycine et au sulfamide étaient restreints en vue d'établir leur lien. Leurs cartes de restriction étaient comparées les unes aux autres ainsi qu'avec les cartes des autres plasmides issus de E. coli pour modifier leurs propriétés de résistance. La résistance à la streptomycine était fondée sur l'expression des gènes strA, strB et/ ou aadA1, alors que la résistance au sulfamide était codée par le gène sul2 ou sul1. Les gènes strA, strB et sul2 étaient transférables par le biais de conjugaison et de transformation. Les gènes sul2 et strA physiquement liés étaient présents dans les deux plasmides pSSGK1 et pSSTGK1. Les plasmides pSSGK1 et pSSTGK1 étaient différents l'un de l'autre, mais respectivement semblables aux plasmides de résistance au sulfamide/streptomycine et sulfamide/streptomycine/tétracycline décrits auparavant dans E. coli uropathogènes issus des humains. La conjugaison des plasmides codant la résistance à la streptomycine et au sulfamide peut être un mécanisme pour la large diffusion et la persistance de ces résistances dans E. coli issus des aliments d'origine animale au Kenya. Le lien physique des gènes strA et sul2 transportés par le plasmide pourrait faciliter la propagation de ces gènes par une co-sélection au cours de la pression sélective imposée par l'utilisation de l'un ou l'autre des deux agents antimicrobiens, et souligne la nécessité de recourir à l'usage judicieux de la streptomycine ou du sulfamide dans l'élevage.Bulletin of Animal Health and Production in Africa Vol. 56 (1) 2008: pp. 56-6

tet(L)-mediated tetracycline resistance in bovine Mannheimia and Pasteurella isolates

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Novel spectinomycin/streptomycin resistance gene, aadA14, from Pasteurella multocida

A novel spectinomycin/streptomycin resistance gene, designated aadA14, was detected on the mobilizable 5,198-bp plasmid pCCK647 from Pasteurella multocida. The aadA14 gene encodes an aminoglycoside adenylyltransferase of 261 amino acids. Sequence comparisons revealed that the AadA14 protein showed less than 60% identity to the AadA proteins known so far

Detection of tetracycline-resistant and susceptible Pasteurellaceae in the nasopharynx of loose group-housed calves

&lt;p&gt;The aim of the present study was to determine which Pasteurella and Mannheimia species are present in the upper respiratory tract of healthy calves with no history of antimicrobial treatment prior to sampling. The presence of subpopulations of tetracycline-resistant Pasteurellaceae was also investigated. Nasal swabs from 61 loose group-housed, clinically healthy calves, 1 to 4 months old, from 16 dairy herds were inoculated aerobically on a selective medium (Columbia agar with 5% ovine blood and 16 mg/L bacitracin) with or without 4 mg/L oxytetracycline (OTC). A total of 43 strains belonging to the family Pasteurellaceae were isolated from 38 calves (62.3%) out of 13 herds (81.3%). The predominant organisms were Pasteurella multocida subsp. multocida (57.4%), Mannheimia varigena (4.9%) and M. haemolytica (3.2%). Growth of Pasteurellaceae on the OTC-containing medium was seen only with samples from two herds (6 animals; 9.8%), and on only one farm this proved to be an OTC-resistant subpopulation. Minimum inhibitory concentration (MIC) determinations by means of agar dilution confirmed a low prevalence of OTC-resistant Pasteurellaceae, with overall MIC(50) and MIC(90) values of 0.25 and 32 mg/L, respectively. These data do not support the hypothesis that the relative high frequency of tetracycline-resistant P. multocida isolates from fatal cases of bovine respiratory disease is related to the presence of minor tetracycline-resistance subpopulations within this species.&lt;/p&gt;</p