Diversity of Antimicrobial Resistance Phenotypes in Salmonella Isolated from Commercial Poultry Farms.

Salmonella remains the leading cause of foodborne illness in the United States, and the dissemination of drug-resistant Salmonellae through the food chain has important implications for treatment failure of salmonellosis. We investigated the ecology of Salmonella in integrated broiler production in order to understand the flow of antibiotic susceptible and resistant strains within this system. Data were analyzed from a retrospective study focused on antimicrobial resistant Salmonella recovered from commercial broiler chicken farms conducted during the initial years of the US FDA's foray into retail meat surveillance by the National Antimicrobial Resistance Monitoring System (NARMS). Sixty-three percentage of Salmonella were pan-susceptible to a panel of 19 antimicrobials used by the NARMS program. Twenty-five antimicrobial resistance phenotypes were observed in Salmonella isolated from two broiler chicken farms. However, Salmonella displaying resistance to streptomycin, alone, and in combination with other antibiotics was the most prevalent (36.3%) antimicrobial resistance phenotype observed. Resistance to streptomycin and sulfadimethoxine appeared to be linked to the transposon, Tn21. Combinations of resistance against streptomycin, gentamicin, sulfadimethoxine, trimethoprim, and tetracycline were observed for a variety of Salmonella enterica serovars and genetic types as defined by pulsed-field gel electrophoresis. There were within and between farm differences in the antibiotic susceptibilities of Salmonella and some of these differences were linked to specific serovars. However, farm differences were not linked to antibiotic usage. Analysis of the temporal and spatial distribution of the endemic Salmonella serovars on these farms suggests that preventing vertical transmission of antibiotic-resistant Salmonella would reduce carcass contamination with antibiotic-resistant Salmonella and subsequently human risk exposure.

Mucosal vaccination with a codon-optimized hemagglutinin gene expressed by attenuated Salmonella elicits a protective immune response in chickens against highly pathogenic avian influenza.

The purpose of this study was to evaluate clinical protection from challenge conferred by two attenuated Salmonella enteria serovar typhimurium vaccine strains expressing the hemagglutinin (HA1) gene from a highly pathogenic avian influenza (HPAI) H5N1 (A/whooper swan/Mongolia/3/2005), under control of the anaerobically inducible nir15 promoter. Two-week-old White Leghorn chickens were immunized by oral gavage with one milliliter doses of >109 Salmonella colony-forming units once weekly for 4 weeks prior to challenge. Expression of recombinant protein was confirmed via Western blot. Serum and mucosal gavage samples were collected prior to, and following immunization and antibodies against avian influenza HA were confirmed by Western blot and hemagglutination-inhibition (HI) assay. Chickens were challenged with homologous (A/whooper swan/Mongolia/3/2005), or heterologous (A/Chicken/Queretaro/14588-19/95) HPAI virus strains. Chickens immunized with attenuated Salmonella strains containing plasmid expression vector (pTETnir15HA) demonstrated a statistically significant increase in survival compared to control groups. Results provide evidence of effectiveness of attenuated Salmonella strains for delivery of recombinant avian influenza HA antigens and induction of mucosal and systemic immune responses protective against lethal challenge with HPAI.

Vertical and horizontal transmission of salmonella within integrated broiler production system.

Salmonella remains one of the leading causes of food-borne illness in the United States, and many key questions regarding the introduction and persistence in animal production systems still remain. In order to understand the ecology of Salmonella within an integrated commercial broiler production system, 289 Salmonella enterica were recovered from two integrated poultry farms during the production and processing of seven consecutive flocks. The variety and prevalence of Salmonella serotypes differed between farms. Overall, 15 serotypes were identified, with the most common being Typhimurium (55%), Montevideo (7.9%), Kentucky (9%), and Enteritidis (9.7%). Salmonella Typhimurium and Enteritidis isolates recovered from processed carcasses from Farm One were further characterized using pulsed-field gel electrophoresis (PFGE), and were shown to be indistinguishable from isolates recovered from the poultry house environment and mice trapped on this farm. Additionally, the same broiler S. Typhimurium and S. Enteritidis strains, identified by PFGE, were also isolated from samples taken at a company breeder farm, suggesting vertical transmission of these Salmonella serotypes in this poultry production system. Results indicate that management practices at the breeder level may have a profound effect on the transmission and persistence of salmonellae within an integrated production system, as well as on the potential contamination of poultry-derived products.

Duodenal obstruction caused by infection with Pythium insidiosum in a 12-week-old puppy.

Pythium insidiosum is an aquatic fungus-like organism that causes a serious chronic granulomatous disease called pythiosis in animals and humans in tropical and subtropical regions of the world. In North America, pythiosis is most often diagnosed in the Gulf Coast states. Early recognition of the disease is crucial to successful treatment, which includes surgical resection of granulomatous lesions and administration of antifungal agents. Despite increasing availability of diagnostic tests, intestinal pythiosis is insidious and is often not detected until lesions are extensive. Intestinal pythiosis was diagnosed in a 12-week-old puppy from South Carolina examined because of vomiting, diarrhea, and anorexia. Pythiosis was not initially suspected because of the young age of the patient and because pythiosis is uncommon in this area.