Staphylococcus aureus From Goats Are Genetically Heterogeneous and Distinct to Bovine Ones

Abstract

Staphylococcus aureus is one of the major pathogens responsible for intramammary infections in small ruminants, causing severe economic losses in dairy farms. In addition, S. aureus can contaminate milk and dairy products and produce staphylococcal enterotoxins, being responsible for staphylococcal food poisoning. Currently, data on the population structure and the virulence gene patterns of S. aureus strains isolated from goat milk is limited. Therefore, this study aimed at defining Ribosomal Spacer PCR (RS-PCR) genotypes, clonal complexes (CC), spa types, and virulence gene profiles of S. aureus isolated from goat milk samples from Lombardy region of Italy. A total of 295 S. aureus isolates from 65 goat bulk tank milk samples were genotyped by RS-PCR. spa typing and virulence gene patterns of a subgroup of 88 isolates were determined, and MLST was performed on a further subgroup of 39 isolates, representing all the spa types identified during the analysis. This study revealed 7 major genotypic clusters (CLR, CLAA, CLZ, CLAW, CLBW, CLS, and CLI), of which S. aureus CLR (19.8%) was the most common. A total of 26 different spa types were detected, the most prevalent types were t1773 (24%), t5428 (22.7%), and t2678 (12.5%). Overall, 44.3% of all isolates harbored at least one enterotoxin gene. The most prevalent was the combination of sec-sel genes (35.2%). Based on their MLST, isolates were assigned to 14 different CC, with majority grouped as CC133 (24%), CC130 (19.6%), and CC522 (19.6%). The caprine S. aureus population was depicted with a minimum spanning tree and an evolutionary analysis based on spa typing and MLST, respectively. Then, the variability of such strains was compared to that of bovine strains isolated in the same space-time span. Our results confirmed that S. aureus isolates from goats have wide genetic variability and differ from the bovine strains, supporting the idea that S. aureus from small ruminants may constitute a distinct population.

Safety Issues Regarding the Detection of Antibiotics Residues, Microbial Indicators and Somatic Cell Counts in Ewes’ and Goats’ Milk Reared in Two Different Farming Systems

“…S. aureus is classified among the most frequent bacterial causative agents of clinical mastitis in small ruminants [54][55][56][57]. The isolation frequencies in the present study were low: two strains out of 120 samples in group A and six strains out of 120 samples in group B.…”

Genomic Analysis of Staphylococcus aureus Isolates Associated With Peracute Non-gangrenous or Gangrenous Mastitis and Comparison With Other Mastitis-Associated Staphylococcus aureus Isolates

“…The majority, 17 of 20 (85%) of our isolates belonged to three CCs: CC151, CC133, and CC97, which have been reported as common bovine-associated complexes ( Hoekstra et al, 2020 ; Naushad et al, 2020 ). Two of our isolates in the peracute group belonged to CC522, which is commonly found in isolates from mastitis in small ruminants ( Kahila Bar-Gal et al, 2015 ; Romano et al, 2020 ). A recent review ( Matuszewska et al, 2020 ) showed that CC522 has thus far been found only in small ruminants.…”

“…CC522 was not detected by Hoekstra et al (2020) , nor by Naushad et al (2020) . Both CC522 and CC133 are commonly found in small ruminants ( Kahila Bar-Gal et al, 2015 ; Romano et al, 2020 ). Neither of the herds from which the CC522 isolates in our study originate has any association with small ruminants, nor are these farms located adjacent to each other.…”

Survey of Staphylococcus aureus carriage by free‐living red deer ( Cervus elaphus ): Evidence of human and domestic animal lineages

“…Despite the extensive typing of S. aureus isolates, the other most prevalent lineages reported in wild ruminants in several European countries, namely CC97, CC130 and CC133 (Monecke et al., 2016 ), were not detected in our study area. This result was unexpected because CC97 and CC130 have been reported in Western Italian Alps in roe deer and chamois (Luzzago et al., 2014 ) and might also represent livestock‐associated lineages in Italy (Feltrin et al., 2016 ; Romanò et al., 2020 ).…”

“…were not detected in our study area. This result was unexpected because CC97 and CC130 have been reported in Western Italian Alps in roe deer and chamois (Luzzago et al, 2014) and might also represent livestock-associated lineages in Italy (Feltrin et al, 2016;Romanò et al, 2020).…”