Comparison of Streptococcus halichoeri isolates from canine and fur animal infections: biochemical patterns, molecular characteristics and genetic relatedness.

BACKGROUND: Streptococcus halichoeri infections have been reported in grey seals, a European badger, a Stellar sea lion and humans, but its presence in companion and fur animals is unknown. Since 2010, S. halichoeri-like bacteria (SHL) have been isolated from fur animals and dogs in Finland. Our aim was to retrospectively investigate laboratory records for SHL from canine and fur animal infections, characterize the isolates and compare their genetic relatedness in relation to three reference strains: CCUG 48324T, originating from a grey seal, and strains 67100 and 61265, originally isolated from humans. RESULTS: A total of 138 and 36 SHLs from canine and fur animal infections, respectively, were identified in the laboratory records. SHL was commonly associated with skin infections, but rarely as the only species. A set of 49 canine and 23 fur animal SHLs were further characterized. MALDI-TOF confirmed them as being S. halichoeri. The growth characteristics were consistent with the original findings, but isolates were catalase positive. In total, 17 distinct API 20 Strep patterns were recorded among all 75 isolates tested, of which pattern 5563100 was the most common (n = 30). Antimicrobial resistance to erythromycin and clindamycin was common in canine isolates, but rare in fur animal isolates. Three clusters were observed by PFGE, and 16S rRNA sequencing revealed 98.1-100% similarities with the human strains and 98.1-99.5% with the seal strain. A phylogenetic tree of concatenated 16S rRNA and rpoB revealed closely related isolates with two clades. Fifteen canine isolates were identical to the human strains based on concatenated 16S rRNA and rpoB sequencing. CONCLUSIONS: Streptococcus halichoeri appears to be quite a common bacterial species in the skin of dogs and fur animals. The clinical significance of S. halichoeri is uncertain, as it was rarely isolated as a monoculture. No apparent temporal or spatial clustering was detected, but isolates from different sources were genetically very similar. Because many canine isolates were genetically similar to the human reference strains, transmission between dogs and humans may be possible. WGS sequencing of strains from different sources is needed to further investigate the epidemiology and virulence of S. halichoeri.

Description of two Serratia marcescens associated mastitis outbreaks in Finnish dairy farms and a review of literature.

BACKGROUND: Infection with Serratia spp. have been associated with mastitis outbreaks in dairy cattle herds. Environmental contamination or a point source, like a teat dip product, have often been observed to be potential sources of such outbreaks. We describe two Serratia marcescens associated mastitis outbreaks associated with a contaminated teat dip containing a tertiary alkyl amine, n,n-bis (3-aminopropyl) dodecylamine in two dairy cattle farms in Finland. S. marcescens strains isolated from milk and environmental samples were identified by the MALDI-TOF method. RESULTS: Six specimens (n = 19) on Herd 1 and all specimens (n = 9) on Herd 2 were positive for S. marcescens. Positive specimens were from mastitis milk and teat dip liquid and equipment. Bacteria were not isolated from the unopened teat dip canister. The same clone of S. marcescens was isolated from milk samples and teat dip samples within the farms. Pulsed field gel electrophoresis results to the S. marcescens isolates from these two different herds were tested with unweighted pair-group method using arithmetic average clustering analysis. The isolates were not same clone in both herds, because similarity in that test was only 75% when cut-off value to similarity is 85%. CONCLUSIONS: Our investigation showed that the post milking teat dip and/or temporary containers were contaminated with S. marcescens and these were most likely the sources for new mastitis cases. The negative result from the unopened teat dip canister and positive results from refillable containers demonstrated that the product itself was not contaminated with S. marcescens at the production unit, but became contaminated at the farm level.

Species distribution and in vitro antimicrobial susceptibility of coagulase-negative staphylococci isolated from bovine mastitic milk.

BACKGROUND: Coagulase-negative staphylococci (CoNS) are the most common bovine mastitis causing bacteria in many countries. It is known that resistance for antimicrobials is in general more common in CoNS than in Staphylococcus aureus but little is known about the antimicrobial resistance of specific CoNS species. In this study, 400 CoNS isolates from bovine mastitic milk samples were identified to species level using ribotyping and MALDI-TOF MS, and their antimicrobial susceptibility was determined using a commercially available microdilution system. The results were interpreted according to the epidemiological cut-off values by the European Committee on Antimicrobial Susceptibility testing. RESULTS: The most common CoNS species were S. simulans, S. epidermidis, S. chromogenes and S. haemolyticus. Penicillin resistance was the most common type of antimicrobial resistance. Staphylococcus epidermidis was the most resistant among the four major species. Almost one-third of our S. epidermidis isolates were resistant to >2 antimicrobials and close to 7 % were multidrug resistant. The majority of S. epidermidis isolates were resistant to benzylpenicillin. On the contrary, only few S. simulans isolates were penicillin-resistant. Phenotypic oxacillin resistance was found in all four main species, and 34 % of the isolates were oxacillin resistant. However, only 21 isolates (5 %) were positive for the mecA gene. Of these, 20 were S. epidermidis and one S. sciuri. mecC positive isolates were not found. CONCLUSION: Staphylococcus epidermidis differed from the three other major CoNS species as resistance to the tested antimicrobials was common, several isolates were multidrug resistant, and 19 % of the isolates carried the mecA gene encoding methicillin resistance.

Phylogeny, virulence factors and antimicrobial susceptibility of Escherichia coli isolated in clinical bovine mastitis.

The aim of this study was to identify specific phylogeny groups, virulence genes or antimicrobial resistance traits of Escherichia coli isolated in bovine mastitis associated to clinical signs, persistence of intramammary infection in the quarter and recovery from mastitis. A total of 154 E. coli isolates from bovine clinical mastitis, 144 from the acute stage and 10 from follow-up samples 3 weeks later, originating from 144 cows in 65 dairy herds in Southern Finland were investigated. Phylogeny groups and virulence genes of the isolates were determined using polymerase chain reaction, and antimicrobial susceptibility using the VetMIC™ microdilution method. In ten cows (11.8%), infection persisted, confirmed by re-isolation of the same pulsed-field gel electrophoresis type from the affected quarter at 3 weeks post-treatment. The majority of isolates, 119 (82.6%), belonged to phylogeny group A, which mainly consisted of commensal strains. Altogether 56 isolates (38.9%) had at least one virulence gene detected. Most common virulence genes detected were irp2, iucD, papC iss; genes svg, stx1, stx2, cnf1 and hlyA were not found. Combinations of virulence genes varied greatly. Forty (27.8%) of the 144 E. coli isolates showed resistance to at least one antimicrobial tested. None of the studied phylogeny groups, virulence factors or antimicrobial resistance traits was associated with clinical signs, persistence of intramammary infection or clinical recovery from mastitis. The results support the conclusion that mastitis-causing E. coli bacteria are typical commensals.