Antimicrobial resistance studies in staphylococci and streptococci isolated from cows with mastitis in Argentina

Abstract

Background Staphylococcus aureus and Streptococcus agalactiae are the main cause of clinical mastitis in dairy cattle in Argentina, whereas coagulase-negative staphylococci (CNS) and environmental streptococci are the main cause of subclinical mastitis. Bacteria isolated from infected animals show increasing antimicrobial resistance. Objectives This study aims to determine the antimicrobial resistance of staphylococci and streptococci isolated from milk with mastitis, and to genotypically characterize the methicillin-resistant (MR) staphylococci. Methods Isolation was performed on blood agar and identification was based on biochemical reactions. Antimicrobial susceptibility was according to the Clinical and Laboratory Standards Institute guidelines. The antimicrobial resistance genes, SCC mec type and spa type were detected by the polymerase chain reaction method. Results We isolated a total of 185 staphylococci and 28 streptococci from 148 milk samples. Among the staphylococcal isolates, 154 were identified as CNS and 31 as S. aureus . Among the 154 CNS, 24.6% (n = 38) were resistant to penicillin, 14.9% (n = 23) to erythromycin, 17.5% (n = 27) to clindamycin, 6.5% (n = 10) to cefoxitin and oxacillin. Among the S. aureus isolates, 16.1% (n = 5) were resistant to penicillin, 3.2% (n = 1) to cefoxitin and oxacillin (MRSA). Six MR isolates (5 CNS and 1 MRSA) were positive to the mecA gene, and presented the SCC mec IVa. The MRSA strain presented the sequence type 83 and the spa type 002. Among the 28 streptococcal isolates, 14.3% (n = 4) were resistant to penicillin, 10.7% (n = 3) to erythromycin and 14.3% (n = 4) to clindamycin. Conclusions The present findings of this study indicate a development of antimicrobial resistance in main bacteria isolated from cows with mastitis in Argentina.

Staphylococcal mastitis in dairy cows

“…Staphylococci are known to become resistant to several antibiotics, including methicillin resistance, which is important for public health ( 163 , 164 ). Methicillin-resistant Staphylococcus aureus (MRSA) infection can only be treated with limited antibiotics and needs long-term treatment ( 163 , 165–167 ). MRSA infection is zoonotic ( 168 ), and continuous antimicrobial susceptibility surveillance is very crucial to control the transmission of this strain from animal production to humans and vice versa ( 169 ).…”

“…Staphylococci are known to become resistant to several antibiotics, including methicillin resistance, which is important for public health ( 163 , 164 ). Methicillin-resistant Staphylococcus aureus (MRSA) infection can only be treated with limited antibiotics and needs long-term treatments ( 163 , 165–167 ).…”

Non-aureus staphylococci and mammaliicocci as a cause of mastitis in domestic ruminants: current knowledge, advances, biomedical applications, and future perspectives – a systematic review

“…Antimicrobials are an important tool in mastitis control programs; therefore, surveillance of antimicrobial susceptibility is important to ensure optimal results when using them and minimize the risk of resistance (Bowler et al 2020 ; Kizerwetter-Świda et al 2018 ). Staphylococci can express resistance to a range of antimicrobials, of which methicillin resistance is of public health concern (Crespi et al 2022 ; Fergestad et al 2021 ). Infections caused by methicillin-resistant Staphylococcus (MRS) are more damaging due to the long-term treatments and limited drug options (Adkins et al 2018b ; Crespi et al 2022 ; Mahato et al 2017 ; Virdis et al 2010 ).…”

“…Staphylococci can express resistance to a range of antimicrobials, of which methicillin resistance is of public health concern (Crespi et al 2022 ; Fergestad et al 2021 ). Infections caused by methicillin-resistant Staphylococcus (MRS) are more damaging due to the long-term treatments and limited drug options (Adkins et al 2018b ; Crespi et al 2022 ; Mahato et al 2017 ; Virdis et al 2010 ). Recent reports from different parts of the world revealed that MRS are an emerging cause of infection and a potent threat to the dairy industry and public health due to their zoonotic potential (Kizerwetter-Świda et al 2018 ; Windria et al 2016 ).…”

Coagulase-negative staphylococci as an evolving mastitis causing organism in cows: A review

“…Regularly monitoring antimicrobial profiles in livestock is very vital to collect data for trends/emergence in antimicrobial resistance genotypes and phenotypes to recognize and identify new or emerging resistance profiles (Crespi et al, 2022).…”