A case of bovine mastitis caused by Listeria monocytogenes.
Year: 1990
Type: article
Abstract: Although Listeria monocytogenes is common in the feces of cattle (1) and widespread in the environment (2), only a few cases of listerial mastitis have been reported in the literature (3-5). These observations indicate that either the organism is not particularly invasive to the bovine udder, or that cases of listerial mastitis are not being detected in routine laboratory examination of mastitic milk samples. We wish to report a case of subclinical mastitis caused by L. monocytogenes that may shed some light on this matter. An investigation was started in 1987 to determine the incidence and origin of L. monocytogenes in raw bulk tank milk in Alberta. Farms yielding positive results on the bulk tank milk were visited for detailed investigations in an effort to determine the origin of the organism. All milk samples, including bulk milk, individual cow samples, and quarter samples were examined for the presence of L. monocytogenes using the selective enrichment methods described by Fedio and Jackson (6). Environmental samples such as feed, water, and feces were examined by primary enrichment in UVM broth (Becton Dickinson Canada Inc., Mississauga, Ontario) and secondary enrichment in Fraser both (7) followed by plating on Oxford Agar (Oxoid Canada Inc., Nepean, Ontario) and lithium chloride phenylethanol moxalactam agar (8). During the course of this investigation, one herd showing positive bulk milk samples was found to contain one animal with subclinical mastitis caused by L. monocytogenes serotype 1 in one quarter. The infected quarter was detected independently in two laboratories, one using the selective enrichment methods described by Fedio and Jackson (6), and the other using routine plating on blood agar (5%0 ovine, Columbia agar base). The detailed findings of this investigation are presented in this paper. The infected animal, identified as 56UA, freshened on June 18, 1989 and appeared to have mastitis at the time in the left hind quarter; this quarter subsequently dried up. Initial tests on the animal on the December 18, 1989 indicated the presence of L. monocytogenes and a somatic cell count (SCC) of 3,500,000/mL in the right hind quarter, although the milk appeared normal. Further tests on December 28, 1989, on the right hind quarter showed moderate growth of L. monocytogenes on sheep blood agar plates (SBA) and a SCC of 5,300,000/mL. The total aerobic plate count was 3,600/mL. It was decided at this time to treat the infected quarter with antibiotics. Antimicrobial susceptibility tests (Kirby Bauer) showed that the organism was sensitive to cephalothin, erythromycin, penicillin, tetracycline, neomycin, and novobiocin; it was resistant to oxacillin. The penicillinsensitive/oxacillin-resistant pattern was confirmed by minimum inhibitory concentration (MIC) determination. Immediately prior to starting the treatment on January 4, 1990 further tests of the infected quarter showed heavy growth of L. monocytogenes on SBA and a SCC of 4,500,000/mL. The treatment given was
Source: PubMed Central
Authors: W M Fedio, M Schoonderwoerd, R H Shute, H Jackson
Language: English
Subfield: Animal Science and Zoology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W1673610074