Abstract
The aim of this study was to determine the species distribution of Staphylococcus, Gram negative bacteria (GNB) and the occurrence of Methicillin Resistant Staphylococci (MRS) and Extended-Spectrum β-lactamase- (ESBL-) producing GNB. Bacterial culture of 300 clinical mastitis milk samples from 30 different farms across different regions of Tunisia during four seasons was realized. The obtained results showed the presence of high frequency of the tested samples with a positive growth for bacteria (64%). In addition a high recovery rate of Staphylococci and/or GNB in these clinical mastitis milk samples (87%) was detected. In addition, a high percentage of GNB (68.2%) compared to Staphylococcus species (32%) was noted. Moreover, a significant variation of the number of these bacteria according to the farm location, the seasons, and cows age was detected. The highest percentage was observed in the North of Tunisia during the winter and the spring seasons in adult cows with a dominance of GNB growth. Coagulase negative Staphylococci (CNS) (n=11) and GNB (n=16) species were identified. Escherichia coli (E. coli) was the most frequently found bacterium followed by Klebsiella pneumoniae. The dominant Staphylococcus isolates was S. xylosus followed by S. aureus the major pathogen isolated. Methicillin resistance was confirmed by the presence of the mecA gene in 3 S. aureus and 14 CNS isolates; all of these isolates were lacking the mecC gene. Various species of GNB, resistant to cefotaxime, were detected (n=15). ESBLs were detected on selective medium in 10 E. coli and 4 K. pneumoniae. All ESBL producers strains carry the blaCTX-M. The presence of different resistant mastitis pathogens in dairy farms may complicate therapeutic options and contaminated animals could become zoonotic agent reservoir for human.
Highlights
Bovine mastitis is one of the most costly and complex diseases of the dairy industry worldwide
Coliforms and Coagulase negative Staphylococci (CNS) are considered as environmental pathogens and are opportunistic bacteria of the mammary gland that may potentially be transferred from the contaminated environment to the cow mammary gland during milking [9]
87% of the tested samples showed a positive growth for Staphylococci and/or Gram negative bacteria (GNB)
Summary
Bovine mastitis is one of the most costly and complex diseases of the dairy industry worldwide. It has a negative impact on animal health and productivity and poses a potential health risk for the consumers [1]. Bovine mastitis is a multifactorial disease, which develops as a result of the interaction between various factors associated with the host, the specific pathogens, the environment, the season, and the farm management [4, 5]. Coliforms and CNS are considered as environmental pathogens and are opportunistic bacteria of the mammary gland that may potentially be transferred from the contaminated environment to the cow mammary gland during milking [9]. The financial implications of mastitis and their importance for public health should not be overlooked
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