Staphylococcus aureus and Streptococcus agalactiae: prevalence, resistance to antimicrobials, and their relationship with the milk quality of dairy cattle herds in Minas Gerais state, Brazil

Abstract

Bovine mastitis is the most frequent disease worldwide in dairy herds, causing high economic losses to producers and industry, as well as having implications for public health due to the zoonotic potential of some agents involved in its etiology and the increased risk of antimicrobial residues in milk and its derivatives. Considering the multifactorial aspect of this disease, knowledge of the agents involved in its etiology and their antimicrobial susceptibility profiles is very important. This study was conducted with 306 dairy herds from the Campo das Vertentes region, located in the south of Minas Gerais state, whose owners were milk suppliers to a dairy in the same region. The study involved approximately 34,000 dairy cows and covered an area of approximately 12,564 km2. In these herds, prevalence rates of Staphylococcus aureus and Streptococcus agalactiae and their relationship with bulk milk somatic cell counts (BMSCC), total bacterial counts (TBC), and daily production were evaluated. In addition, analyses of resistance of these pathogens to the antimicrobials most commonly used in the treatment of mastitis in dairy herds were performed. Microbiological analyses of milk samples from collect from bulk milk tanks were performed aiming to evaluate the prevalence of S. aureus and S. agalactiae. For these proposes, the modified Baird-Parker Agar medium was used for detection of S. aureus and the modified Edwards Agar medium, enriched with 5% defibrinated sheep blood, was used for detection of S. agalactiae. The disc diffusion technique was applied to evaluate antimicrobial resistance. Results show high prevalence rates of S. aureus (70.3%) and S. agalactiae (67.0%) in the dairy farms studied, with 47.71% of the herds showing both pathogens. Associations between BMSCC and the presence of pathogens S. aureus and S. agalactiae and between TBC and the presence of S. agalactiae were observed, demonstrating the influence of these pathogens in milk quality. No variation was observed in the distribution of S. aureus and S. agalactiae in the different strata of daily production. High levels of resistance and multi-resistance were observed among the pathogens S. aureus and S. agalactiae. The results indicate the need for more effective control measures for mastitis caused by S. aureus and S. agalactiae in the dairy herds of the region studied and more judicious use of antimicrobials in order to reduce the problem of resistance to them.

Molecular Typing and Antimicrobial Susceptibility Profile of Staphylococcus aureus Isolates Recovered from Bovine Mastitis and Nasal Samples

“…Beyond that, even if we excluded resistance to penicillin, as proposed by Magiorakos et al [ 10 ], 30 (15.87%) isolates were regarded as multidrug-resistant S. aureus . A high proportion of S. aureus isolates originated from IMIs harboring resistance to tetracycline and penicillin has been previously observed in Brazil [ 22 , 23 ], which corroborates our findings. Nevertheless, our study showed a high level of resistance to gentamycin in S. aureus originating from IMIs, although gentamycin resistance frequencies reported are generally low [ 22 , 23 ].…”

“…A high proportion of S. aureus isolates originated from IMIs harboring resistance to tetracycline and penicillin has been previously observed in Brazil [ 22 , 23 ], which corroborates our findings. Nevertheless, our study showed a high level of resistance to gentamycin in S. aureus originating from IMIs, although gentamycin resistance frequencies reported are generally low [ 22 , 23 ]. The high level of multidrug resistant S. aureus found here, together with the predominance of an udder-adapted strain, may contribute to our knowledge of the history of the high level of mastitis caused by this pathogen, as the existence of penicillin-resistant S. aureus is related to low cure rates for S. aureus IMI treatment with either β-lactam or non-β-lactam antimicrobials [ 24 ].…”

Antibacterial Use of Macroalgae Compounds against Foodborne Pathogens

“…Unfortunately, this contaminated food provoked a foodborne outbreak and 140 patients presented primary symptoms of sore throat and fever [ 150 ]. Bovine mastitis is the most frequent disease worldwide in dairy herds, causing high economic losses for producers and the industry, as well as having implications for public health due to the zoonotic potential of some agents involved in its etiology and the increased risk of antimicrobial residues in milk and its derivatives [ 151 ].…”

“…The prevalence of S. agalactiae in 306 dairy herds from Campo das Vertentes region, located in the south of Minas Gerais state, Brazil, was evaluated. The study involved approximately 3.4 × 10 4 dairy cows and covered an area of approximately 1.2 × 10 4 km 2 and indicated that 67% of the samples were contaminated with S. agalactiae [ 151 ]. S. agalactiae was also found in bulk milk from Prince Edward Island dairy farms [ 152 ].…”

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“…Also, a high antimicrobial resistance to β-lactam antibiotics was identified in the MIC test.4.2 INTRODUCTIONStaphylococcus aureus is a commensal skin pathogen, capable of infecting humans, cattle and a variety of other species. This microorganism is frequently isolated from raw milk(BOUFAIDA ASNOUNE et al, 2012;SAIDI;KHELEF;KAIDI, 2013) and its within-herd prevalence on Brazilian dairy farms was reported to be 7.4%(DITTMANN et al, 2017) and of 70.3% among herds(MESQUITA et al, 2019). Intramammary infections (IMI) caused by S.…”