Investigation of Tetracycline antimicrobial activities against Staphylococcus aureus from clinical mastitis strains in growth media and milk
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- October 22, 2021
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Nur Syammimi Abdul Hadi. Investigation of Tetracycline antimicrobial activities against Staphylococcus aureus from clinical mastitis strains in growth media and milk. 30th Veterinary Association of Malaysia (VAM) Congress. 19th-20th October, 2018. Hilton Hotel, Petaling Jaya, Malaysia.(Abstract of Rapid Oral Presentation).
1Nur Syammimi Abdul Hadi, 2Nor Fadhilah Kamaruzzaman 1Veterinary Research Institute, Department of Veterinary Services, 59, Jalan Sultan Azlan Shah, 31400 Ipoh, Perak, Malaysia 2University Malaysia Kelantan, Universiti Malaysia Kelantan, Pengkalan Chepa, 16100, Kota Bharu, Kelantan, Malaysia. Corresponding author: email@example.com
Mastitis is a disease characterized by inflammation of mammary gland which causes economic losses in the dairy industry. Antibiotic therapy has not been successful to control the disease. Interaction of the drug and protein composition in the milk like as casein is believed to reduce drug’s efficacy. Therefore, this study was conducted to investigate and compare the antibacterial activities of tetracycline against three Staphylococcus aureus strains isolated from clinical mastitis cases in the growth media and pasteurized milk. Minimum inhibitory concentration (MIC) was performed using the broth dilution method. MIC of tetracycline against S. aureus clinical mastitis strain 1 and 3; 2 µg/ml while strain 2; 1 µg/ml. Different concentrations of tetracycline MIC values; 1xMIC, 25xMIC, 50xMIC and 100xMIC from three strains S. aureus were used to determine bactericidal activities by time-kill assay (TKA) in pasteurized milk and growth media at 0, 2, 4, and 24 hour post incubation. The study revealed no bactericidal effect on MIC values of tetracycline against S. aureus strains with the absence of 3-log decrease in CFU/mL of bacteria counts, as compared to the growth control. All three strains of S. aureus showed 100% bacterial growth in pasteurized milk while 75 to 92% of bacterial growth was recorded in growth media at the concentration of 100xMIC of tetracycline. That study confirms the milk inhibits antibacterial activities. Thus, tetracycline intramammary treatment alone may not yield the best effect in treating clinical mastitis.
Keywords: S. aureus clinical mastitis, tetracycline, minimum inhibitory concentration (MIC)