There are not many data available on antibiotics used solely in animals and almost exclusively for growth promotion. These products include bambermycin, avilamycin, efrotomycin, and the ionophore antibiotics (monensin, salinomycin, narasin, and lasalocid). Information is also scarce for bacitracin used only marginally in human and veterinary medicine and for streptogramin antibiotics. The mechanisms of action of and resistance mechanisms against these antibiotics are described. Special emphasis is given to the prevalence of resistance among gram-positive bacteria isolated from animals and humans. Since no susceptibility breakpoints are available for most of the antibiotics discussed, an alternative approach to the interpretation of MICs is presented. Also, some pharmacokinetic data and information on the influence of these products on the intestinal flora are presented

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Four staphylococcal isolates from clinical and necropsy specimens from a cat, a dog, a horse and a parrot (Psittacus erithacus timneh) were found to constitute a distinct taxon. 16S rRNA gene sequence analysis revealed that its closest phylogenetic relatives are Staphylococcus intermedius and Staphylococcus delphini. Growth characteristics, biochemical features and DNA-DNA hybridizations demonstrated that the strains differ from these and other known species and that they represent a single, novel Staphylococcus species for which the name Staphylococcus pseudintermedius sp. nov. is proposed. The novel species is commonly confused with S. intermedius in routine diagnostic veterinary bacteriology. Although the strains described were isolated from lesions and show several characteristics typical of pathogenic staphylococci, such as coagulase, DNase and b-haemolysin production, the pathogenic significance of the novel species remains unclear. The type strain, LMG 22219 T (=ON 86 T =CCUG 49543 T ), was isolated from lung tissue of a cat.

The susceptibilities of 12 antimicrobial agents for two collections of Staphylococcus aureus, isolated in the 1970s and in 2006 from poultry, were determined. For eight antibiotics, the percentage of resistance was significantly higher in the recent isolates. Ten recent isolates were methicillin resistant and had spa types t011 and t567, belonging to multilocus sequence type 398. This is the first report of "livestock-associated" methicillin resistant S. aureus from healthy poultry.Antimicrobial agents, including penicillin, erythromycin, and tetracyclines, are widely used for treating staphylococcal and other infections in poultry (1,19,23). The extensive use of antimicrobial agents in animal husbandry contributes to the selection of drug-resistant strains. Recently, the isolation of methicillin-resistant Staphylococcus aureus (MRSA) from animals has been reported at an increasing frequency (14,15,16,18,22,24). This study analyzes the frequency of acquired resistance to 12 antimicrobial agents, ␤-lactamase activity, and the prevalence of the mecA gene between two groups of S. aureus isolates from poultry.Ninety S. aureus isolates were obtained from tendon sheaths of diseased breeder chickens and from the noses and cloacae of healthy broiler breeders between 1970 and 1972 (9) (old isolates), and eighty-one S. aureus isolates were collected from the noses and cloacae of healthy chickens derived from 39 randomly selected industrial broiler farms in 2006 (recent isolates). The old isolates had been lyophilized and stored at Ϫ20°C until used. To collect the recent isolates, the noses and cloacae of five chickens from each flock were sampled. Samples were inoculated on Columbia agar supplemented with sheep blood, colistin, and nalidixic acid (Oxoid, Basingstoke, United Kingdom). Isolates were identified as S. aureus by colony morphology, standard biochemical methods, and growth on modified Baird-Parker medium (10). Multiplex PCR for the femA and mecA genes was performed to confirm the identification and methicillin resistance of S. aureus (17,22). Susceptibility to oxacillin, penicillin, enrofloxacin, erythromycin, tylosin, lincomycin, gentamicin, neomycin, spectinomycin, sulfonamides, tetracycline, and trimethoprim was determined according to CLSI guidelines by using agar dilution tests (6).For interpretation of MICs, European Committee on Antimicrobial Susceptibility Testing (EUCAST; http://www.escmid .org/sites/index_f.aspx?parϭ2.4) wild-type cutoff values were used, except for enrofloxacin and tylosin, for which we used cutoff values from our study, according to the bimodal distribution of MICs (20). ␤-Lactamase production was tested for the penicillin-resistant isolates by using ␤-lactamase diagnostic tablets (Rosco, Taastrup, Denmark) according to the manufacturer's instructions. MRSA isolates (n ϭ 10) were genotyped by pulsed-field gel electrophoresis (PFGE) after SmaI macrorestriction analysis and by DNA sequence analysis of the polymorphic repeat region of protein A gene (spa typing) (8, 13). The spa types w...

DNA-rRNA hybridizations (Kilpper-Balz et al., 1982) and 16S rRNA cataloguing data (Ludwig et ai., 1985) have shown that the enterococci form a separate genus. This was confirmed with the more comprehensive 16S rRNA sequencing studies which elucidated the precise phylogenetic position of the genus. Based on almost complete 16S rRNA sequences the enterococci have been shown to belong to the clostridial subdivision of the Gram-positive bacteria, comprising also the lactic acid bacterial genera Aerococcus, Carnobacterium, Giobicatella, Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, Streptococcus, Tetragenococcus, and Vagococcus. The enterococci form a distinct cluster with the genera Vagococcus, Tetragenococcus and Carnobacterium as their closest neighbours Aguirre and Collins, 1992). This phylogenetic group of four genera is genealogically somewhat more closely related to Aerococcus and Dolosigranulum than to the streptococci or the lactococci, to which Enterococcus has historically been linked.Within the genus Enterococcus 16S rRNA sequences revealed the presence of species groups (Williams et al., 1991), as shown in Figure 10.1. The first group contains Ent. durans, Ent. faecium, Ent. hirae and Ent. mundtii (between 98.7 and 99.7% 16S rRNA sequence similarity). The second contains Ent. avium, Ent. raffinosus, Ent. malodoratus and Ent. pseudoavium (between 99.3 and 99.7% 16S rRNA sequence similarity). The third consists of the species pair Ent. casseliflavus and Ent. gallinarum (99.8% 16S rRNA sequence similarity) which is peripherally linked to the avium species group. Enterococcus saccharolyticus, Ent. sulfureus, Ent. faecalis, Ent. cecorum and Ent. columbae form individual lines of descent (Martinez-Murcia and Collins, 1991) but Ent. cecorum was found to be more related to Ent. coiumbae than to any other Enterococcus species.Enterococcus solitarius appears to be phylogenetically more closely related to the genus Tetragenococcus (c. 98% 16S rRNA sequence similarity) than to the enterococci (c. 92-94% 16S rRNA sequence similarity; Collins et al., 1990;Williams et al., 1991), whereas the type strain (ATCC 49156) of Ent. seriolicida has been shown to be genealogically identical with Lactococcus garvieae (100% 16S rRNA similarity; Collins, M.D., unpublished). At present no 16S rRNA sequencing data are available for Ent. flavescens. By SDS-PAGE of whole-cell proteins, this species cannot be discriminated from Ent. casseliflavus (Pot et al., unpublished). Therefore, its taxonomic status is uncertain. Growth and isolation of enterococciBecause of their complex nutrient requirements, enterococci cannot be grown and studied in defined media. They require several vitamins, biotin,