REGULAR ARTICLES Bacterial isolation of milk samples submitted from clinical mastitis buffaloes during 2007 to 2016 P. S. Bhutia 1 & B. K. Bansal 1 & D. K. Gupta 1 & Raj Sukhbir Singh 2 & S. K. Uppal 1 Received: 30 July 2018 /Accepted: 12 February 2019 # Springer Nature B.V. 2019 Abstract The present study determined trends in the isolation of bacterial pathogens in milk samples submitted from clinical mastitis buffaloes at the University mastitis laboratory during 2007 to 2016. Culture results (n = 3945) were classified into six categories (Staphylococcus spp., 28.7%; Streptococcus spp., 1%; Corynebacterium spp., 1.1%; gram-negative organisms, 3.2%; others including mixed growths, 3.3%; and no growth, 62.7%). Overall, culture results were significantly associated with year (χ 2 = 112.28; df = 10; P < 0.001) and season (χ 2 = 136.03; df = 20; P < 0.001). From 2007–2009 to 2013–2016, the isolation of Staphylococcus spp. increased from 28.2 to 48.4%, while isolation of Streptococcus spp. (50 to 20%) and Corynebacterium spp. (65.1 to 16.3%) decreased. The proportion of samples characterized as no growth increased from 26.4% (2007–2009) to 46.3% (2013–2016). Further, the proportion of clinical mastitis cases increased over the study years (goodness-of-fit χ 2 = 59; df = 2; P < 0.001). With respect to season, the proportion of Staphylococcus spp. (30.6%; 346/1132), Corynebacterium spp. (48.8%; 21/43), and gram-negative bacteria (55.9%; 71/127) were more associated with the monsoon, and that of Streptococcus spp. (47.5%; 19/40) with the winter. Seasonal effects were also observed on the occurrence of clinical mastitis cases; compar- atively, more clinical mastitis cases (35.6%; 523/1473) were observed during the monsoon season (goodness-of-fit χ 2 = 276.7; df = 4; P < 0.001) as compared with other seasons. The present study concludes that Staphylococcus spp. are the major cause of intramammary infections in buffaloes with clinical mastitis, demanding more studies regarding its epidemiology and pathoge- nicity. Also, more efforts are needed in the prevention and control of clinical mastitis in buffaloes, especially, during the monsoon season. Keywords Buffalo . Clinical mastitis . Milk sample . Bacteriological analysis . Year . Season Introduction Mastitis, an inflammation of mammary gland, is a common and economically important disease of dairy cattle reported worldwide (Halasa et al. 2007). Economic losses to dairy in- dustry attributed to mastitis include reduced milk yield and quality, milk discard, involuntary premature culling, veterinary services and treatment costs, and increased labor (Bansal and Gupta 2009). Bovine mastitis can be classified as clinical mastitis and subclinical mastitis. In subclinical mastitis, there are no ob- servable or palpable changes in the udder or secreted milk; however, clinical mastitis is always associated with abnormal- ities of the udder (such as edema, redness, warmness, pain on palpation, fibrosis) and milk (such as flakes, blood, pus or watery discharge). Regardless of the fact that mastitis is caused by vast range of microbial species (Smith and Hogan 2001), the majority of intramammary infections (IMI) are caused by bacterial pathogens such as Staphylococcus aureus, coagulase-negative staphylococci (CNS), Streptococcus spp., and Escherichia coli (Reyher et al. 2012). The distribution of mastitis pathogens differs within individual animals in a herd, and between herds, host species, and countries (Dhakal et al. 2007, Sharma et al. 2012, Tufani et al. 2012, Oliveira et al. 2013, Gao et al. 2017) and largely attributed to herd- (Gao * Raj Sukhbir Singh rsbs_66@rediffmail.com 1 Department of Veterinary Medicine, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, Punjab 141 004, India 2 Department of Teaching Veterinary Clinical Complex, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, Punjab 141 004, India Tropical Animal Health and Production https://doi.org/10.1007/s11250-019-01846-w