Identification and antimicrobial resistance of Streptococcus uberis and Streptococcus parauberis isolated from bovine milk samples

The conventional identification of Streptococcus uberis/parauberis group (n = 137) in clinical and subclinical bovine mastitis samples originating from 111 different farms was compared with identification based on 16 and 23S rRNA gene HindIII RFLP patterns used as operational taxonomic units in numerical analyses. On the basis of ribopattern analysis only 2 isolates belonged to S. parauberis, which is thus not a frequent cause of bovine intramammary infections in Finland. According to in vitro antimicrobial susceptibility testing, Streptococcus uberis is susceptible to beta-lactam antibiotics. The prevalence of erythromycin (15.6%) and oxytetracycline (40.6%) resistance of clinical S. uberis isolates was higher than reported previously among subclinical isolates. The 2 subclinical S. parauberis isolates were susceptible to all the antimicrobials tested.

Comparison of tests for detection of beta-lactamase-producing staphylococci

Penicillin resistance identification tests are important in veterinary medicine. Six enzyme assays and a PCR test were compared for the detection of beta-lactamase production or the beta-lactamase gene in 175 staphylococcal isolates. We conclude that the PCR test and two nitrocefin-based assays can be recommended for routine clinical use.

Interlaboratory proficiency testing as a tool for improving performance in laboratories diagnosing bovine mastitis

The National Veterinary and Food Research Institute (Finland) and the Veterinary Laboratories Agency of the Quality Assurance Unit, Department for Environment, Food and Rural Affairs, United Kingdom (previously the Ministry of Agriculture, Fisheries and Food) organized a proficiency testing program for laboratories analyzing veterinary mastitis samples. Three test samples with lyophilized strains of common aerobic bacteria were sent to the participating laboratories 7 times between 2000 and 2003. The participants returned 98% of the requested data. The overall performance of the laboratories varied from 63 to 93% in different testing rounds. All laboratories diagnosed Staphylococcus aureus and Escherichia coli correctly at every round. Improvement in diagnosing individual bacteria was observed for Staphylococcus epidermidis, Streptococcus dysgalactiae, Enterococcus spp. and Klebsiella spp. The overall performance of the laboratories improved with increased participation. The educational role of the program was important. Laboratories working in the veterinary field should implement a documented quality system covering all functions of the laboratory, as well as a planned quality assurance system.

Bovine Mastitis in Finland 2001—Prevalence, Distribution of Bacteria, and Antimicrobial Resistance

A nationwide survey was conducted in Finland to estimate prevalence of bovine mastitis, distribution of mastitis pathogens, and in vitro antimicrobial susceptibility of different mastitis pathogens. In total, 12,661 quarter milk samples were collected from 3282 dairy cows at 216 farms. These were randomly selected from a database covering all Finnish dairy farms. Quarter milk samples collected by the dairy advisors were submitted for somatic cell counting, bacteriological examination, and testing for antimicrobial susceptibility. If the milk SCC of a cow or of a quarter exceeded 300,000/mL, the cow was defined as having mastitis. The results were compared with those of a previous survey done in 1995. The prevalence of mastitis continued to decrease from 38% in 1995 to 31% in 2001. Compared with the study from 1995, the number of quarters with bacterial growth in 2001 increased significantly from 21.0 to 33.5%. This mainly resulted from increased prevalence of Corynebacterium bovis. Coagulase-negative staphylococci remained the most common bacterial group, comprising almost one-half of the pathogens isolated, whereas the relative number of Staphylococcus aureus isolations decreased from the time of the previous study. According to in vitro antimicrobial susceptibility testing, the enterococci demonstrated the highest level of resistance. Compared with the other Nordic countries, penicillin resistance among the staphylococci was still at a relatively high level in Finland (52.1 and 32.0% for Staphylococcus aureus and coagulase-negative staphylococci, respectively). Streptococci isolated from mastitis were very susceptible to beta-lactam antibiotics, as also found in the previous survey in 1995.

A three-year study of Campylobacter jejuni genotypes in humans with domestically acquired infections and in chicken samples from the Helsinki area

Campylobacter jejuni isolates from stool samples of patients with domestically acquired sporadic infections and from chicken from retail shops were studied during seasonal peaks from June to September over a 3-year period from 1996 to 1998. A large number of pulsed-field gel electrophoresis (PFGE) genotypes (a combined SmaI-SacII pattern) were identified each year. Certain genotypes persisted for the whole study period, and predominant genotypes represented 28 to 52% of the strains during a restricted period of time. The peak level of positive chicken samples was between July and August of each study year, when 10 to 33% of the samples were positive for campylobacter. The same PFGE genotypes found in humans were also detected in the chicken samples. This suggests that common genotypes were circulating in the area.