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Since the emergence of MRSA in livestock, screening of animals for the detection of MRSA is widely practised. Different procedures are published for animal samples but a systematic comparison of methods has not been performed. The objective of this study was to compare three available commonly used procedures and three chromogenic agars for detecting MRSA in nasal swabs from pigs (n=70) and veal calves (n=100). Procedures 1 and 2 used a pre-enrichment comprising Mueller Hinton broth with 6.5% NaCl followed by selective enrichment with 4 microg/ml oxacillin+75 microg/ml aztreonam (procedure 1) and 5 microg/ml ceftizoxime+75 microg/ml aztreonam (procedure 2) respectively. Procedure 3 used a selective enrichment broth only, containing 4% NaCl, 5 microg/ml ceftizoxime+50 microg/ml aztreonam. After selective enrichment, media were streaked on to three different chromogenic agars. Significantly more MRSA were found for pig as well as for veal calf samples with procedures 1 and 2. No significant differences were found between procedures 1 and 2. For nasal swabs from pigs significantly more MRSA-positive samples were found when MRSA Screen (Oxoid) or MRSASelect (Bio-Rad) agars were used compared to MSRA ID (bioMérieux). For calf samples no significant differences between the different agars were found. In conclusion, the results of this study show that procedures 1 and 2, both using additional high salt pre-enrichment are superior and should be recommended for MRSA detection in nasal swabs from pigs and veal calves. The preferred choice of chromogenic agar depends on the sample matrix.

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In order to shed some light on the different opinions regarding the importance of Salmonella infections in dogs, we gathered some data from our laboratory database. Of the 6589 faecal samples from diarrhoeic dogs examined, 69 (1%) yielded Salmonella spp. Another eleven isolates were cultured from materials other than faeces. If Salmonella spp. can be cultured directly from faeces, this should be interpreted as clinically significant; however, even if the organism is found only after enrichment it may still be a clinical case. Antibiotic therapy is indicated in all dogs that are severely ill or have systemic infection, fluoroquinolones or trimethoprim/sulphonamides being drugs of choice. Double-blind placebo-controlled studies of humans with gastroenteritis have shown that the length of postconvalescent excretion of Salmonella is not affected by antimicrobials. For the elimination of the carrier state, however, fluoroquinolones are successful in human medicine. Salmonellae are zoonotic agents and transmission from dog to man has been reported. This should be taken into account when deciding on antimicrobial therapy. Of our isolates (n = 80), 96% were susceptible to enrofloxacin, 94% to trimethoprim/sulphonamides, 94% to gentamicin, 86% to ampicillin and amoxicillin-clavulanic acid, 47% to cephalexin and 63% to tetracycline.