Etiology and in vitro antimicrobial susceptibility profile of strains isolated from bovine mastitis in dairy herds from the midwest region of Santa Catarina state, Brazil

Abstract

Article history Dairy farming is an important social and economic activity in the Midwest region of Santa Catarina State, Brazil. However, despite technological advances in the productive chain, mastitis is still considered the main disease of dairy herds, due its high economic impact. Bacterial pathogens are the main cause of this disease and failures in the treatment of clinical cases are attributed in part to the antimicrobial resistance of these pathogens. As an alternative, in vitro antimicrobial susceptibility tests of strains isolated from bovine mastitis cases have been carried out; the information generated contributes to strategic treatment measures, and also to the control of microorganism resistance. Therefore, the aims of the present study were to evaluate the etiology and in vitro antimicrobial susceptibility profiles of bacterial strains isolated from cases of bovine mastitis in dairy herds from the Midwest region of Santa Catarina State, Brazil. For this purpose, 345 milk samples were collected from 70 herds located in 16 different municipalities. The main pathogens isolated were: staphylococci (55.9%), streptococci (34.8%), Corynebacterium spp. (7.8%) and Escherichia coli (1.4%). The resistance rates of staphylococcus strains to ampicillin and to gentamicin were lower (24.9%) and higher (33%), respectively, than those obtained in other Brazilian studies. The resistance profiles of streptococcus strains were similar to those described in the literature, while Corynebacterium spp., showed high resistance rates to tetracycline (85.2%). Moreover, a considerable prevalence of staphylococcus (27.5%) and streptococcus (11.7%) multiresistant strains was verified. These data reinforce the need for regional characterization of microorganisms.

Species identification and antimicrobial susceptibility profile of bacteria associated with cow mastitis in southern Brazil

“…Staphylococcus spp. was also the most commonly bacterial genus isolated from bovine mastitis in previous studies carried out in Brazil (Oliveira et al 2011, Haubert et al 2017, Valmorbida et al 2017, Lavor et al 2019) and even in other countries (Sztachańska et al 2016, Vakkamäki et al 2017, Kim et al 2019). On contrast, 56 milk samples dit not present bacterial growth.…”

“…is another important genus associated with clinical mastitis. The two isolates identified as S. uberis by MALDI-TOF MS deserve special attention, once this species is an environmental pathogen responsible for a significant proportion of mastitis cases and associated with the lack of hygiene in the dairy farms (Valmorbida et al 2017). This pathogen can persist in the udder and cause a chronic infection in the mammary gland.…”

“…Importantly, it was observed a high frequency of bacterial resistance to penicillin, tetracycline, amoxicillin, ampicillin and sulfamethoxazole/trimethoprim in this study (46.3%, 39%, 36.6%, 34.1% and 31.7%, respectively). Antimicrobial resistance is not a recent phenomenon, but it has progressively increased in the last decades due to an abusive use in veterinary and human medicine (Valmorbida et al 2017). The high frequency of resistance to some of these antimicrobials were expected, since they were frequently used in veterinary practice in recent years (Dorneles et al 2018).…”

“…The large use of these medicines has resulted in a high increase of the antimicrobial resistance in different bacterial species isolated from milk samples in Brazil (Mesquita et al 2019). Importantly, many bacterial isolates have already presented resistance to three or more antimicrobial classes, evidencing the occurrence of multidrug-resistance (MDR) (Machado et al 2008, Silva et al 2012, Valmorbida et al 2017, Dorneles et al 2018, Freitas et al 2018.…”

Training, development, and evaluation of on-farm culturing as a technical resource to reduce the use of antimicrobials in dairy herds in the Midwest Region of Santa Catarina State, Brazil

“…In this way, the possibility of bacteriological cure of the cow is reduced, leading to the chronicity of cases; the continued elimination of pathogens in the milk of infected cows acts as sources of infection for other animals in the herd. Additionally, the need to repeat the treatment, with a consequent increase in the therapeutic cost and pressure for the selection of genetically resistant bacterial strains, increases the number of days for discarding milk, and the partial and/or total loss of function of the affected mammary gland (s), determining the early culling of animals (VALMOrBIDA et al, 2017).…”