Antibiotic resistance of Staphylococcus aureus isolated from raw cow and goat milk produced in the Tiaret and Souk Ahras areas of Algeria

Antibiograms, multidrug resistance, and milk-related parameters of bacteria isolated from milk of dairy cattle in Phatthalung, Thailand

Background and Aim

Milk, a nutritious food, is widely consumed in human diets; however, contamination by micro-organisms can negatively impact its quality and consumer health. Contamination by micro-organisms affects the quality of milk, which can affect the quality of the milk production chain. This study aimed to determine the changes in milk composition and antibiotic susceptibility related to bacteria isolated from dairy cow milk.

Materials and Methods

Raw milk samples were collected from 72 dairy cows. All milk samples were subjected to the California Mastitis Test (CMT) for CMT score determination. We also investigated milk composition, bacterial culture (BC), and antibiotic susceptibility.

Results

About 47.22% and 30.56% of dairy cattle were positive for CMT + BC and automatic somatic cell count (ASCC) + BC, respectively. Fecal appearance and animal age were found to be risk factors for ASCC + BC positivity in dairy cattle. Bacteria were found in approximately 76% of milk samples, with the most common isolated species being α-hemolytic Streptococcus spp., coagulase-negative Staphylococcus spp., and Escherichia coli. Of these, 70% are resistant to at least one antibiotic. Variation in the multidrug resistance pattern was high in Klebsiella spp.

Conclusions

Fecal appearance and animal age are risk factors for ASCC + BC positivity in dairy cattle. This study identified antibiotic and multidrug resistance patterns, which require comprehensive studies and effective surveillance systems. Remarkably, the use of antibiotic therapy in dairy cattle should be monitored.

The first study on antimicrobial resistance of Staphylococcus aureus isolated from raw goat milk associated with subclinical mastitis in Siliragung Subdistrict, East Java, Indonesia

Background and Aim

Raw goat milk is a highly nutritious dairy product and a suitable medium for the growth of antimicrobial-resistant Staphylococcus aureus, the leading cause of subclinical mastitis. This study aimed to investigate the resistance status of S. aureus which isolated from goat milk associated with subclinical mastitis cases in Siliragung Subdistrict, Banyuwangi District, East Java, Indonesia.

Materials and Methods

The S. aureus isolates were recovered from 258 raw goat milk samples from seven different dairy goat farms. Preliminary screening of subclinical mastitis using the California mastitis test, then samples with score +3 and +4 were taken for further isolation and identification, followed by a biochemical test to determine the S. aureus. Moreover, the bacteria susceptibility test against several antimicrobials was done using the disk diffusion method.

Results

Based on our findings, a total of 66 (25.58%) raw goat milk samples were tested positive for S. aureus, of which 36.36% were identified as multidrug-resistant. Moreover, S. aureus were also identified as resistant to penicillin (81.82%), ampicillin (65.15%), erythromycin (50.52%), and gentamicin (36.09%).

Conclusion

The prevalence of S. aureus isolated from raw goat milk associated with subclinical mastitis in Siliragung Subdistrict, Banyuwangi District, Indonesia, was recorded at 25.58%. Moreover, 36.36% of S. aureus isolates were categorized as resistant to three or more classes of antibiotics. The biosafety and biosecurity procedures during the milking process should be strengthened in dairy goat farms to prevent the transmission of antimicrobial resistance among animals, humans, and environments.