Antimicrobial resistance patterns to beta-lactams of gram-positive cocci isolated from bovine mastitis in Lithuania.

The aim of the study was to isolate gram-positive cocci from cows with mastitis and to determine their resistance to beta-lactamic antibiotics. Eight hundred and nine strains were isolated and identified as staphylococci (n=516), streptococci (n=199) and enterococci (n=94) from sub-clinical and clinical cases of bovine mastitis in Lithuania. The most common causative agents of udder disease included: S. epidermidis (n=176), S. aureus (n=176), S. agalactiae (n=134), S. hyicus (136) and E. hirae (n=68). Isolates were analysed for antimicrobial resistance to penicillin, ampicillin, amoxicillin, cephalothin, cephalexin, amoxicillin + clavulanate. The susceptibility patterns were analysed using the agar disk diffusion method. S. aureus showed the highest level of resistance to amoxicillin (81.3%), penicillin (76.7%) and ampicillin (78.4%). The corresponding values for CNS strains were 59.7%, 59.7% and 50.6% against penicillin, ampicillin and amoxicillin respectively. Streptococci were the most frequently resistant to amoxicillin (29.3%), and enterococci to penicillin (27%), amoxicillin (27.5%) and amoxicillin/clavulanic acid (23.8%). The resistance of all tested mastitis pathogens to aminopenicillins and penicillin highly correlated (r=0.83). Compared with other antibiotics, amoxicillin and clavulanic acid combination tended to be more effective (p<0.05) against all tested bacteria in vitro. However, S. aureus, in 38.1% of cases, was resistant to this combination of antimicrobials. This study demonstrates that S. epidermidis, S. aureus, S. hyicus, S. agalactiae and E. hirae remain the most frequent mastitis causative agents on Lithuanian cattle farms. The highest resistance in vitro to penicillins was demonstrated by S. aureus, S. hyicus and S. intermedius. Resistance to cephalosporins remains low, irrespective of bacterial species of gram-positive cocci.

A comparison of modifications of the McMaster method for the enumeration of Ascaris suum eggs in pig faecal samples.

The comparative efficacies of seven published McMaster method modifications for faecal egg counting were evaluated on pig faecal samples containing Ascaris suum eggs. Comparisons were made as to the number of samples found to be positive by each of the methods, the total egg counts per gram (EPG) of faeces, the variations in EPG obtained in the samples examined, and the ease of use of each of the methods. Each method was evaluated after the examination of 30 samples of faeces. The positive samples were identified by counting A. suum eggs in one, two and three sections of newly designed McMaster chamber. In the present study compared methods were reported by: I-Henriksen and Aagaard [Henriksen, S.A., Aagaard, K.A., 1976. A simple flotation and McMaster method. Nord. Vet. Med. 28, 392-397]; II-Kassai [Kassai, T., 1999. Veterinary Helminthology. Butterworth-Heinemann, Oxford, 260 pp.]; III and IV-Urquhart et al. [Urquhart, G.M., Armour, J., Duncan, J.L., Dunn, A.M., Jennings, F.W., 1996. Veterinary Parasitology, 2nd ed. Blackwell Science Ltd., Oxford, UK, 307 pp.] (centrifugation and non-centrifugation methods); V and VI-Grønvold [Grønvold, J., 1991. Laboratory diagnoses of helminths common routine methods used in Denmark. In: Nansen, P., Grønvold, J., Bjørn, H. (Eds.), Seminars on Parasitic Problems in Farm Animals Related to Fodder Production and Management. The Estonian Academy of Sciences, Tartu, Estonia, pp. 47-48] (salt solution, and salt and glucose solution); VII-Thienpont et al. [Thienpont, D., Rochette, F., Vanparijs, O.F.J., 1986. Diagnosing Helminthiasis by Coprological Examination. Coprological Examination, 2nd ed. Janssen Research Foundation, Beerse, Belgium, 205 pp.]. The number of positive samples by examining single section ranged from 98.9% (method I), to 51.1% (method VII). Only with methods I and II, there was a 100% positivity in two out of three of the chambers examined, and FEC obtained using these methods were significantly (p<0.01) higher comparing to remaining methods. Mean FEC varied between 243 EPG (method I) and 82 EPG (method IV). Examination of all three chambers resulted in four methods (I, II, V and VI) having 100% sensitivity, while method VII had the lowest 83.3% sensitivity. Mean FEC in this case varied between 239 EPG (method I) and 81 EPG (method IV). Based on the mean FEC for two chambers, an efficiency coefficient (EF) was calculated and equated to 1 for the highest egg count (method I) and 0.87, 0.57, 0.34, 0.53, 0.49 and 0.50 for remaining methods (II-VII), respectively. Efficiency coefficients make it possible not only to recalculate and unify results of faeces examination obtained by any method but also to interpret coproscopical examinations by other authors. Method VII was the easiest and quickest but least sensitive, and method I the most complex but most sensitive. Examining two or three sections of the McMaster chamber resulted in increased sensitivity for all methods.