Genotypic and phenotypic characterization of Staphylococcus aureus causing persistent and nonpersistent subclinical bovine intramammary infections during lactation or the dry period.

Staphylococcus aureus is a significant pathogen frequently causing persistent intramammary infections (IMI) in dairy cows. We compared some genotypic and phenotypic characteristics of 285 strains collected from quarter milk samples from cows with persistent and nonpersistent subclinical IMI across Canada. Variable number of tandem repeats typing was used to infer the persistence of the same S. aureus strain in 3 consecutive quarter milk samples collected at intervals of 3 wk during lactation or before and after dry-off. All first isolates of the series were used as the representative strains from persistent IMI and were compared with nonpersistent strains for the presence of genes seg, sen, sec, and tst as well as by spa typing. Biofilm production in vitro and hld-RNAIII expression levels were also quantified. The gene seg was associated with a reduction in the likelihood of the bacteria to cause a persistent IMI during lactation. Strains persisting through the dry period produced significantly more biofilm in vitro than strains that do not persist after calving. Also, we showed that strains expressing more hld were more likely to be nonpersistent during either lactation or through the dry period. Three spa types were predominant (t529, t267, and a novel type: t13401). In the strains studied, the spa type tbl 2645 was the most frequent, and 97.0% of the strains of this spa type carried both sen and seg. Strains from the spa type tbl 2645 were less likely to cause a persistent IMI in the dry period. Most (86.7%) of the strains of the novel spa type (t13401) were negative for seg, sen, or both and produced significantly more biofilm in vitro than tbl 2645 and t267. The present study expanded our current knowledge on the genotypic and phenotypic traits of S. aureus strains recovered from persistent and nonpersistent IMI in Canada.

[Detection by RT-PCR of the 1st cases of Astrovirus in human stools in Abidjan, Côte d'Ivoire]. / Détection par RT-pCR des premiers cas d'Astrovirus dans les selles humaines à Abidjan, Côte d'Ivoire.

Viral gastroenteritis are a problem of public health because of the high rate of morbidity and mortality, particularly in children. Among the etiologic agents, human Astroviruses are the third agents most often incriminated after Rotaviruses and Caliciviruses. Symptoms of gastroenteritis caused by Astroviruses are generally moderated compared with those observed with Rotaviruses and rarely involve hospitalization. In sub-Saharan Africa, particularly in Côte d'Ivoire, the majority of viral gastroenteritis is attributed to Rotavirus with rates varying from 20 to 26%. No study on the circulation of human Astroviruses has been carried out in Côte d'Ivoire. Our objective was to detect human Astroviruses in the diarrhoeal stools in Abidjan. Seventy-two samples of human diarrhoeal stools were collected in ambulatory patients. This population was made up of 44 patients from 0 to 15 and 28 patients over 15 years old. The concentration of the viral particles of the samples was followed by the extraction of the RNA by the modified method of Boom. The extracted RNA were amplified by RT-PCR by using specific primers targeting a portion of the 3' end of the open reading frame ORF la of the genome of human Astroviruses. The amplified fragment was 192 pb. The genome of human Astroviruses was detected in 3 stools out of the 72 samples. That is a frequency of 4%. Among these 3 stools, 2 came from 4 month and 3 year-old children and the 3rd stool came from a 33 year-old patient. For the first time this survey has pointed out the circulation of human Astroviruses in the Côte d'Ivoire population. This survey also showed that human Astroviruses could be found in children as well as in adults.