Bacteria Isolated From Milk of Dairy Cows With and Without Clinical Mastitis in Different Regions of Australia and Their AMR Profiles

Abstract

Mastitis is the most common disease in dairy cattle worldwide. The objectives of this study were to estimate the prevalence of different bacterial species associated with mastitis from dairy herds located in geographically and climatically distinct zones in Australia, and to evaluate the antimicrobial susceptibility of the isolated bacteria. Quarter-level milk samples (n = 419) were collected from 151 mastitis cases and 268 healthy controls originating from 18 dairy herds located in tropical (Northern Queensland), subtropical (Southeast Queensland) and temperate zones (Victoria) between March and June 2019. Milk samples were cultured, and the isolated bacteria were grouped into six groups: Enterobacteriaceae spp.; Streptococcus spp.; Staphylococcus aureus, non-aureus staphylococci (NAS); Bacillus spp.; and Others. Mixed effects conditional logistic regression models were applied to quantify the association between the prevalence of each bacterial group and the herd zone and bulk milk tank somatic cell counts (BMTSCC). Of the 205 isolates, 102 (50%) originated from mastitis cases, and 103 (50%) from controls. Staphylococci were the most prevalent (NAS 32% and S. aureus 11%). Contagious mastitis bacteria were more prevalent in Victoria compared to Queensland dairy herds. NAS species (P < 0.001) were less prevalent in herds with BMTSCC >300,000 cells/mL compared with herds with low BMTSCC ≤150,000 cells/mL. Enterobacteriaceae and Streptococcus spp. groups showed high resistance rates to 1 (51 and 47%, respectively), and 2 (11 and 23%, respectively), antimicrobials. More than one third of the Enterobacteriaceae (48%) and Others (43%) groups spp. were resistant to at least three antimicrobials. This study provided a unique opportunity to investigate the prevalence of mastitis-associated bacteria in clinical cases and in apparently healthy controls. The findings of this study help inform mastitis control and antimicrobial stewardship programs aimed to reduce the prevalence of mastitis and antimicrobial resistance in dairy herds.

Etiology of Mastitis and Antimicrobial Resistance in Dairy Cattle Farms in the Western Part of Romania

“…None of the isolates were sensitive for all antimicrobials, an aspect also observed by others [ 34 , 35 , 36 ]. In the present research, all 14 strains tested showed the multiple resistance phenomenon, as follows: six strains (42.9%) to five antimicrobials, three strains (21.4%) to six antimicrobials, two strains (14.3%) to eight antimicrobials, two strains (14.3%) to nine antimicrobials and one strain (7.1%) to ten antimicrobials.…”

“…The target plate was then loaded on MALDI-TOF Biotyper and identified by comparing the mass spectral protein detection pattern with the reference patterns in database. A score of >0.2 was accepted as representing a reliable identification [ 34 , 64 ].…”

Detection of immunoreactive proteins of Escherichia coli, Streptococcus uberis, and Streptococcus agalactiae isolated from cows with diagnosed mastitis

“…The results obtained in this paper corresponded to Australian studies, in which S. uberis was the most commonly cultivated bacterial species collected from milk samples (Dyson et al, 2022). Al-harbi et al also described S. uberis as the most common species of Streptococcus spp., however, the percentage was fourfold lower compared to our results (Al-harbi et al, 2021). In the European cattle population, S. uberis is also described as the most common agent causing mastitis (Tenhagen et al, 2006;Botrel et al, 2010).…”

“…In most of the clinical cases of mastitis in our study, were caused by Streptococcus spp. The obtained results corresponded to the investigation described by Al-harbi et al (Al-harbi et al, 2021), as well as to the North American cattle population (Schukken et al,TABLE 2 Bioinformatic prediction of proteins' cell localization (Busca database), detection of signal peptides (PRED-LIPO), classical (SignaIP) and nonclassical (Secretome, PncsHub) proteins, and prediction of antigenicity (VaxiJen). 2009; Levison et al, 2016).…”

A culture-, amplification-independent, and rapid method for identification of pathogens and antibiotic resistance profile in bovine mastitis milk

“…host cell/DNA exists. Most previous research that used PF (Ganda et al, 2016;Lima et al, 2018;Taponen et al, 2019;Al-Harbi et al, 2021;Ma T. et al, 2021;Schwenker et al, 2022) or NG kit (Quigley et al, 2012;Cheema et al, 2021;Lyons et al, 2021) considered 16S metagenomic sequencing for bacterial identification following DNA extraction; therefore, no host DNA contamination was reported. While amplicon sequencing is a sensitive method for taxonomy clarification, the relevance of this approach for rapid diagnostic and AMR gene detection in mastitis is questionable.…”