Prevalence of contagious and environmental mastitis-causing bacteria in bulk tank milk and its relationships with milking practices of dairy cattle herds in São Miguel Island (Azores)

Carla Azevedo,Jaime Maldonado,Ricardo Romão,Mónica Moitoso,Roger Guix,Luísa Soares,João Simões,Diana Pacheco

doi:10.1007/s11250-015-0973-6

Carla Azevedo, Jaime Maldonado + Show 6 more

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https://doi.org/10.1007/s11250-015-0973-6

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Abstract

This study aimed to assess the degree of contamination of bulk tank milk (BTM) by Staphylococcus spp. and coliform bacteria and to identify major milking practices that help perpetuate them in dairy cattle herds in São Miguel Island. In July 2014, BTM was sampled and a survey concerning local milking practices was conducted on 100 herds. Semi quantitative multiplex polymerase chain reaction detected coagulase-negative staphylococci, Escherichia coli, Staphylococcus aureus, and other coliform bacteria (Klebsiella oxytoca, Klebsiella pneumoniae, and Serratia marcescens) in 100, 75, 59, and 35 % of BTM, respectively. According to multivariable univariate models, on herds not using hot water for cleaning the milking machine and teat liners, there was at least 3.4 more odds (P < 0.01) to have S. aureus or coliform bacteria contamination in BTM. The likelihood of finding S. aureus in BTM was higher (P < 0.001) on herds without high hygiene during milking, when milking mastitic cows at the end, on abrupt cessation of milking at dry-off, and official milk control implementation. The glove use also favored (odds ratio (OR) 5.8; P < 0.01) the detection of coliform bacteria in BTM. Poor milking practices identified in this study should be avoided in order to decrease S. aureus and coliform bacteria contamination of BTM. Other factors associated with milk quality in São Miguel Island also should be further investigated.

Highlights

Bovine mastitis affects a high proportion of cows in dairy herds worldwide, being considered one of the major diseases causing a negative economic impact to the dairy industry (Bradley 2002)
Of the 100 samples tested, coagulase-negative staphylococci (CNS) were present in 100 %, E. coli in 75 %, S. aureus in 59 %, and coliform bacteria in 35 %
The microbiological milk quality is a key economic factor for dairy farms and pathogenic bacteria could arise from several sources (Berry et al 2006; Rysánek et al 2009; Bava et al 2011), such as mastitic udders of cows, incrementing somatic cell counts (SCC), and/or during milking and milk transport to bulk tank milk (BTM)

Summary

Introduction

Bovine mastitis affects a high proportion of cows in dairy herds worldwide, being considered one of the major diseases causing a negative economic impact to the dairy industry (Bradley 2002). Information concerning prevalence and distribution of both environmental and contagious mastitis-causing bacteria (Zadoks et al 2001; Riekerink et al 2010), along with the identification of contributing risk factors (Leelahapongsathon et al 2014) are crucial in order to control and/or prevent the disease. Testing on samples from the bulk tank milk (BTM) is an accurate and effective approach for evaluating the milk quality at herd level (Cicconi-Hogan et al 2013) and is useful for the detection and identification of contagious bacteria in cows clinically affected by mastitis (Riekerink et al 2010). The polymerase chain reaction (PCR) has been recently used for the specific and sensitive detection and identification of environmental and contagious mastitisrelated pathogens (Katholm et al 2012). Taponen et al (2009) observed that the real-time PCR method (qPCR) can detect bacteria on approximately half of the negative bacteriologic cultures

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