Treatment of experimentally induced Pasteurella multocida infections in broilers and turkeys: comparative studies of different oral treatment regimens

Novel multi-strain probiotics reduces Pasteurella multocida induced fowl cholera mortality in broilers

Pasteurella multocida causes fowl cholera, a highly contagious poultry disease of global concern, causing significant ecological and economic challenges to the poultry industry each year. This study evaluated the effects of novel multi-strain probiotics consisting of Lactobacillus plantarum, L. fermentum, Pediococcus acidilactici, Enterococcus faecium and Saccharomyces cerevisiae on growth performance, intestinal microbiota, haemato-biochemical parameters and anti-inflammatory properties on broilers experimentally challenged with P. multocida. A total of 120 birds were fed with a basal diet supplemented with probiotics (10⁸ CFU/kg) and then orally challenged with 10⁸ CFU/mL of P. multocida. Probiotics supplementation significantly (P < 0.05) improved growth performance and feed efficiency as well as reducing (P < 0.05) the population of intestinal P. multocida, enterobacteria, and mortality. Haemato-biochemical parameters including total cholesterol, white blood cells (WBC), proteins, glucose, packed cell volume (PCV) and lymphocytes improved (P < 0.05) among probiotic fed birds when compared with the controls. Transcriptional profiles of anti-inflammatory genes including hypoxia inducible factor 1 alpha (HIF1A), tumor necrosis factor- (TNF) stimulated gene-6 (TSG-6) and prostaglandin E receptor 2 (PTGER2) in the intestinal mucosa were upregulated (P < 0.05) in probiotics fed birds. The dietary inclusion of the novel multi-strain probiotics improves growth performance, feed efficiency and intestinal health while attenuating inflammatory reaction, clinical signs and mortality associated with P. multocida infection in broilers.

Florfenicol As a Modulator Enhancing Antimicrobial Activity: Example Using Combination with Thiamphenicol against Pasteurella multocida

Synergistic effects between the same class of antibiotics are rarely reported. Our previous study found synergistic-like interaction between florfenicol (FFC) and thiamphenicol (TAP) against Staphylococcus aureus. Here, the enhanced antimicrobial activity was evaluated in 97 clinical isolates of both Gram-negative and Gram-positive bacteria. Susceptible strains were initially identified by checkerboard microdilution assay (fractional inhibitory concentration index [FICI] ≤ 0.625), followed by confirmation of synergism using the time-kill methodology (≥2 log₁₀ CFU/ml reduction). In all, 43% of Pasteurella multocida tested were susceptible to the enhanced bactericidal effect. In chicken fowl cholera models, FFC and TAP combination at much lower dosage that is correspondent to their MIC deduction provided maximum protection in vivo. Furthermore, synergistic combination of FFC with oxytetracycline (OTC) against Pseudomonas aeruginosa in vitro was also demonstrated. Based on the enhanced uptake of TAP and OTC, FFC presumably elicits enhanced antimicrobial activity in an orderly manner through alteration of bacterial membrane permeability or efflux systems and subsequent increase of intracellular concentration of the antibiotics used in combination. Results of ethidium bromide accumulation assay and RNA-seq showed little evidence for the involvement of efflux pumps in the synergy but further investigation is required. This study suggests the potentiality of a novel combination regimen involving FFC as an initiating modulator effective against both Gram-positive and Gram-negative bacteria depending on the antibiotics that are combined. The observed improvement of bacteriostatic effect to bactericidal, and the extended effectiveness against FFC-resistant bacterial strains warrant further studies.

Identification of Pasteurella multocida Serogroup F isolates in rabbits

A total of 24 Pasteurella multocida rabbit isolates obtained from 24 rabbit flocks in the Czech Republic during the period of between 2001 and 2004 were analysed by capsular PCR typing. Apart from isolates identified as serogroups A (n = 14, 58.4%) and D (n = 2, 8.3%), eight isolates (33.3%) were identified as members of serogroup F. This serogroup had been predominantly associated with poultry infections so far. The rabbit serogroup F isolates were characterized in detail by ribotyping with restriction to endonuclease MspI revealing two distinct ribotypes. Seven serogroup F isolates were assigned to ribotype 1 and one isolate was assigned to ribotype 2.

Disposition of norfloxacin in broiler chickens and turkeys after different methods of oral administration

Norfloxacin was administered orally to chickens and turkeys at 15 mg/kg body weight by pulse dosing at 24 h intervals and by continuous dosing at 100 mg/L in drinking water for five days. Blood samples were taken serially. Plasma norfloxacin concentrations were determined by high-performance liquid chromatography. The plasma norfloxacin concentrations increased slowly during continuous dosing and reached the MIC(90) (250 ng/mL) for Gram-negative pathogens by 12 h in chickens and 18 h in turkeys. The steady-state plasma concentration was attained in 36 h and remained at approximately 776.67+/-33.23 ng/mL in chickens and 682.50+/-28.55 ng/mL in turkeys. After pulse dosing, the plasma norfloxacin concentrations increased rapidly and exceeded the MIC(90) at 2 h in both species and remained above MIC(90) for 8 h in chickens and 6 h in turkeys. Pulse dosing provided half the steady-state concentration that was achieved by continuous dosing, 365.32+/-39.31 ng/mL in chickens and 306.03+/-32.26 ng/mL in turkeys, during the dosing interval of 24 h. Data for daily pulse dosing suggested that every administration corresponded to a single, daily repeated bolus administration although pulse dosing produced higher plasma concentrations more readily. Continuous and pulse dosing are both rational for the administration of norfloxacin to flocks of chickens and turkeys. We recommend that treatment be commenced with a pulse oral dose administered over a 4 h period and maintained by continuous oral medication for three to five consecutive days.