[Resistance of mastitis pathogens in northern Germany]

The data of 1692 susceptibility tests acquired from April 2003 through March 2004 in the mastitis laboratory of the Institute for Food Quality and Safety were summarized in order to help veterinarians confronted with acute mastitis in choosing the appropriate antibiotic. Two thirds of the milk samples were infected with gram-positive cocci. One third of these were identified as Streptococcus (S.) uberis, one fourth as Staphylococcus (S.) aureus. All isolates (100%) of S. uberis, S. dysgalactiae, S. agalactiae and Arcanobacterium pyogenes were susceptible to Penicillin and Ampicillin. Concering S. aureus, nearly 100% of the isolates were susceptible to Oxacillin, Cephalothin, Cefacetril, Cefquinom and Neomycin, but only 88% of the isolates were sensitive to Penicillin, Ampicillin and Cefoperazon. The gram-negative rods (Escherichia (E.) coli, Klebsiella spp. and Pseudomonas spp.) displayed an irregular resistance pattern. More than 93% of all examined isolates including Pseudomonas spp. were susceptible to Colistin. The sensitivity of E. coli and Klebsiella spp.to Marbofloxacin, Enrofloxacin and Cefquinom exceeded 96%. Thus, the susceptibility of gram-positive mastitis pathogens to common antibiotics is favourable. Because the highly effective Colistin is no longer approved for local therapy, the situation for gram-negative bacteria is more difficult.