Bovine Mastitis in Oman is Mainly Associated with Environmental Bacteria that Show High Resistance to Commonly Used Antibiotics

Author(s): Al-Haddadi W, Elshafie A, Al-Ansari A, Al-Mawly J, Al-Hatali R, Al-Habsi H, Al-Hshami A, Al-Ansari A

In Oman, mastitis is an important disease that affects the dairy animals, especially cows. In this study, bacteria and fungi from subclinical and clinical mastitis were identified using 16S rDNA and 18S rDNA, respectively, in 76 milk samples from 30 cows. The frequency of subclinical mastitis (75%) was higher than clinical mastitis (25%). Bacterial isolates were detected in 82% of the samples, out of which 12% showed mixed bacterial cultures. The most predominant isolated bacteria were environmental bacteria rather than minor and contagious bacteria from subclinical (53.6%, 42.8% and 3.6%, respectively) and clinical mastitis (62.5%, 25% and 12.5%, respectively).

Antibiotic resistance profiles of the isolated bacteria for six commonly used antibiotics showed an increase in resistance compared to a previous study in 1991. Most isolated bacteria were resistance to AMP, while they were more sensitive for SXT and TE. Eleven percent of the isolated bacteria were resistance to four of the antibiotics tested or more.

About half of the samples (47%) were positive for fungal growth. Most of those samples were positive for bacteria, which suggested that detected fungi may be opportunistic. However, 3% of the investigated samples were negative for bacterial growth, which may indicate pathogenic involvement in mastitis.

In conclusion, the major association of mastitis with environmental bacteria and the detected multi-antibiotics resistance emphasized the need for using appropriate control protocols by allowing to investigate each case and determine whether antibiotic treatment is necessary and which antibiotics to be used.

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