title: Identifying the major bacteria causing intramammary infections in individual milk samples of sheep and goats using traditional bacteria culturing and real-time polymerase chain reaction.
abstract: Use of DNA-based methods, such as real-time PCR, has increased the sensitivity and shortened the time for bacterial identification, compared with traditional bacteriology; however, results should be interpreted carefully because a positive PCR result does not necessarily mean that an infection exists. One hundred eight lactating dairy ewes (56 Manchega and 52 Lacaune) and 24 Murciano-Granadina dairy goats were used for identifying the main bacteria causing intramammary infections (IMI) using traditional bacterial culturing and real-time PCR and their effects on milk performance. Udder-half milk samples were taken for bacterial culturing and somatic cell count (SCC) 3 times throughout lactation. Intramammary infections were assessed based on bacteria isolated in ≥2 samplings accompanied by increased SCC. Prevalence of subclinical IMI was 42.9% in Manchega and 50.0% in Lacaune ewes and 41.7% in goats, with the estimated milk yield loss being 13.1, 17.9, and 18.0%, respectively. According to bacteriology results, 87% of the identified single bacteria species (with more than 3 colonies/plate) or culture-negative growth were identical throughout samplings, which agreed 98.9% with the PCR results. Nevertheless, the study emphasized that 1 sampling may not be sufficient to determine IMI and, therefore, other inflammatory responses such as increased SCC should be monitored to identify true infections. Moreover, when PCR methodology is used, aseptic and precise milk sampling procedures are key for avoiding false-positive amplifications. In conclusion, both PCR and bacterial culture methods proved to have similar accuracy for identifying infective bacteria in sheep and goats. The final choice will depend on their response time and cost analysis, according to the requirements and farm management strategy.
authors.affiliation: Group of Ruminant Research (G2R), Department of Animal and Food Sciences, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Rovai
authors.affiliation: Group of Ruminant Research (G2R), Department of Animal and Food Sciences, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Caja
authors.affiliation: Group of Ruminant Research (G2R), Department of Animal and Food Sciences, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Sheep and Goat Research Department, Animal Production Research Institute, Dokki 12311, Giza, Egypt.
authors.forename: A A K
authors.initials: AA
authors.lastname: Salama
authors.affiliation: Laboratori Interprofessional Lleter de Catalunya (ALLIC), 08348 Cabrils, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Jubert
authors.affiliation: Vacunek, Ibaizabal Bidea 800, Parque Científico y Tecnológico de Bizkaia, 48160 Derio Bizkaia, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Lázaro
authors.affiliation: Laboratori Interprofessional Lleter de Catalunya (ALLIC), 08348 Cabrils, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Lázaro
authors.affiliation: National Mastitis Reference Center, Kimron Veterinary Institute, PO Box 12, Bet Dagan 50250, Israel. Electronic address: leitnerg@moag.gov.il.
authors.forename: G
authors.initials: G
authors.lastname: Leitner
mesh_terms: D000818:Animals; D058345:Asymptomatic Infections / Q000453:epidemiology*; D002452:Cell Count / Q000662:veterinary; D015169:Colony Count, Microbial; D005260:Female; D006041:Goats / Q000382:microbiology*; D007774:Lactation; D008321:Mammary Glands, Animal / Q000382:microbiology; D008413:Mastitis / Q000453:epidemiology / Q000662:veterinary*; D008892:Milk / Q000166:cytology / Q000382:microbiology*; D015995:Prevalence; D060888:Real-Time Polymerase Chain Reaction; D012756:Sheep / Q000382:microbiology*
keywords: mastitis prevalence; real-time polymerase chain reaction; small ruminant; subclinical mastitis