RESUMO
Potential synergism between florfenicol (FF) and thiamphenicol (TAP) was investigated for in vitro efficacy against Actinobacillus pleuropneumoniae and/or Pasteurella multocida as well as in vivo efficacy in swine. Among isolates of A. pleuropneumoniae (n = 58) and P. multocida (n = 79) from pigs in Taiwan that were tested, high percentages showed resistance to FF (52 and 53%, respectively) and TAP (57 and 53%, respectively). Checkerboard microdilution assay indicated that synergism [fractional inhibitory concentration index (FICI) ≤ 0.5] was detected in 17% of A. pleuropneumoniae (all serovar 1) and 24% of P. multocida isolates. After reconfirming the strains showing FICI ≤ 0.625 with time kill assay, the synergism increased to around 32% against both bacteria and the number could further increase to 40% against resistant A. pleuropneumoniae and 65% against susceptible P. multocida isolates. A challenge-treatment trial in pigs with P. multocida showed that the FF + TAP dosage at ratios correspondent to their MIC deduction was equally effective to the recommended dosages. Further on the combination, the resistant mutation frequency is very low when A. pleuropneumoniae is grown with FF + TAP and similar to the exposure to sub-inhibitory concentration of FF or TAP alone. The degree of minimum inhibitory concentration (MIC) reduction in FF could reach 75% (1/4 MIC) or more (up to 1/8 MIC for P. multocida, 1/16 for A. pleuropneumoniae) when combined with 1/4 MIC of TAP (or 1/8 for A. pleuropneumoniae). The synergism or FICI ≤ 0.625 of FF with oxytetracycline (47%), doxycycline (69%), and erythromycin (56%) was also evident, and worth further investigation for FF as a central modulator facilitating synergistic effects with these antimicrobials. Taken together, synergistic FF + TAP combination was effective against swine pulmonary isolates of A. pleuropneumoniae and P. multocida both in vitro and in vivo. Thus, this study may offer a potential alternative for the treatment of A. pleuropneumoniae and P. multocida infections and has the potential to greatly reduce drug residues and withdrawal time.
RESUMO
BACKGROUND: A number of domestic rabbit (Oryctolagus cuniculus) breeds exist, and the pet rabbit population consists of a variety of pure- and crossbred animals. However, the reference intervals (RIs) for rabbits are limited by outdated methods and a single-breed source. OBJECTIVE: This study aimed to establish more complete, updated erythrocytic and biochemical RIs for the crossbred pet rabbit population to improve routine diagnostic accuracy in clinical practice, and to examine the effects of crossbreeding on erythrocytic and biochemical parameters. METHODS: Blood specimens were collected from 85 clinically healthy crossbred pet rabbits representing a wide range of breeds. RIs for the erythrocyte indices and 12 chemistry analytes were determined as recommended by the American Society for Veterinary Clinical Pathology guidelines. The results were compared with four widely used RIs. Age and sex differences for all variables were statistically analyzed. RESULTS: The results diverged from the RIs for New Zealand white rabbits, indicating that not all RIs from this species are appropriate for use in exotic animal practices. Breed-associated variations were evident for aspartate amino transferase, alkaline phosphatase, and glucose, while crossbreed effects were found for total protein, albumin, blood urea nitrogen, creatinine, calcium, and phosphate. Statistically significant differences and clinical relevance among age groups were detected for hemoglobin, hematocrit, and creatinine. CONCLUSIONS: Establishing RIs specifically for crossbred pet rabbits is desirable for clinicians treating pet rabbits of various breeds and ages. Age-specific RIs for this population warrants further investigation.
