Establishment of a Pathogenicity Index for One-day-old Broilers to Pasteurella multocida Strains Isolated from Clinical Cases in Poultry and Swine

Galleria mellonella larvae as an alternative model to determine the pathogenicity of avian pathogenic Escherichia coli

RESEARCH HIGHLIGHTS

Galleria mellonella larvae are a viable model for determining APEC pathogenicity.Larval disease score is the main variable for determining APEC pathogenicity.Response variables should be evaluated up to 24 h post-inoculation.

Virulence attitude estimation of Pasteurella multocida isolates in embryonated chicken eggs

A total of 220 birds of age ranging from 3 to 14 weeks old were collected from several backyards and different farms in Sharkia Governorate, Egypt, and surveyed for the presence of fowl cholera. Twenty Pasteurella multocida from chickens (15/145, 10%) and ducks (5/75, 6%) were bacteriologically isolated, and it was shown that the infection was significantly related to age and breed. Capsular typing, using multiplex polymerase chain reaction (PCR), demonstrated that all strains were type A (100%). Disk diffusion assay towards ten antimicrobials revealed high susceptibilities to amikacin, doxycycline, chloramphenicol, and neomycin with varying degrees. Doxycycline was effective at the lowest concentration (MIC 0.125-1 µg/ml). Multidrug resistance was detected with a percentage of 25%. Multidrug-resistant isolates (five isolates) were subjected to study their pathogenicity in embryonated chicken eggs (ECE). The results showed a variation in indices between different dilutions of the tested strains. The resulting pathogenicity indices showed significant differences (P < 0.05) according to the origin and dilution of the isolate. From the original inoculum to 10^-4 dilutions, the mortality of inoculated embryos occurred within 1-2 days with pathological findings, including maceration and lesions on chorioallantoic membrane (CAM). From dilutions ranging from 10^-5 to 10^-9, no death occurred until 7 days post-inoculation, but a variation in the lesions on CAM was observed. In conclusion, P. multocida serogroup A could be intensely pathogenic for mature chickens thus causing considerable economic losses, and PCR provides a suitable technique for early and rapid diagnosis of fowl cholera.

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.

Pharmacokinetic and pharmacodynamic integration of enrofloxacin against Salmonella Enteritidis after administering to broiler chicken by per-oral and intravenous routes

It is crucial to optimize the dose of fluoroquinolones to avoid antibiotic resistance and to attain clinical success. We undertook this study to optimize the dose of enrofloxacin against Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) in chicken by assessing its pharmacokinetic/pharmacodynamic (PK/PD) indices. The antibacterial activities of enrofloxacin against S. Enteritidis were evaluated. After administering 10 mg/kg body weight (b.w.) of enrofloxacin to broiler chickens of both sexes by intravenous (IV) and peroral (PO) routes, blood samples were drawn at different intervals and enrofloxacin concentrations in plasma were determined. PK/PD indices were calculated by integrating the PK and PD data. The elimination half-lives (T_1/2), time required to reach peak concentration (T_max), peak concentration (C_max), and area under curve (AUC) after administering enrofloxacin by PO and IV routes were 25.84 ± 1.40 h, 0.65 ± 0.12 h, 3.82 ± 0.59 µg/mL, and 20.84 ± 5.0 µg·h/mL, and 12.84 ± 1.4 h, 0.22 ± 0.1 h, 6.74 ± 0.03 µg/mL, and 21.13 ± 0.9 µg.h/mL, respectively. The bioavailability of enrofloxacin was 98.6% ± 8.9% after PO administration. The MICs of enrofloxacin were 0.0625–1 µg/mL against S. Enteritidis strains, and the MIC₅₀ was 0.50 µg/mL. The C_max/MIC₅₀ were 7.64 ± 0.2 and 13.48 ± 0.7 and the 24 h AUC/MIC₅₀ were 41.68 ± 0.1 and 42.26 ± 0.3 after administering the drug through PO and IV routes, respectively. The data in this study indicate that the application of 50 mg/kg b.w. of enrofloxacin to chicken through PO and IV routes with a dosing interval of 24 h can effectively cure S. Enteritidis infection, indicating the need for a 5-fold increase in the recommended dosage of enrofloxacin in chicken.

Evaluation of the biofilm formation capacity of Pasteurella multocida strains isolated from cases of fowl cholera and swine lungs and its relationship with pathogenicity

ABSTRACT: Pasteurella multocida is a Gram-negative bacillus that causes economic losses due to the development of respiratory diseases in several animal species. Among the mechanisms of virulence, the formation of biofilms is an important factor for bacterial survival in hostile environments. Studies of biofilm formation by P. multocida are needed because P. multocida is an important pathogen involved in respiratory infections. However, in contrast to other microorganisms, few studies of biofilm formation have examined P. multocida. Studies comparing the pathogenicity of microbial strains as a function of their biofilm production capacity are also rare. Consequently, the aim of this study was to evaluate the biofilm formation capacity of 94 P. multocida strains isolated from cases of fowl cholera and from swine lungs on polystyrene plates. The associations of the biofilm formation capacity with the pathogenicity index (PI) in vivo and with the presence of four genes (screened by PCR) of the tad locus (tadB, tadD, tadE and tadG), described as adhesion markers, were also determined. Strains from both animal origins were able to form biofilms. However, most of the specimens (52.13%) were classified as weak producers, and more than 40% of the strains of P. multocida (40.42%) did not produce biofilms. There was no significant difference (p>0.05) in the degree of biofilm production between the two sources of isolation. Of the analyzed strains, 56.52% contained all four genes (tadB, tadD, tadE and tadG). The PI arithmetic mean of the strains classified as non-biofilm producers was significantly different (p<0.05) from the PI of moderate-producer strains. The PI of specimens classified as weak biofilm producers also differed significantly (p<0.05) from that of the moderate-producer strains. The results indicate that even though the P. multocida strains isolated from cases of fowl cholera and swine lungs formed biofilms on polystyrene surfaces, adhesion was usually weak. The genes tadB, tadD, tadE and tadG were not significantly associated (p>0.05) with the production of biofilms and with the origin of a given strain. Finally, low virulence strains may suggest a higher biofilm formation capacity on polystyrene plates.