Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2005
Publication Date: N/A
Interpretive Summary: Listeria monocytogenes (Lm) contamination of poultry processing plants and products is assumed to be due to contamination with environmental bacteria and poor hygiene, and not due to carriage by poultry, based largely on studies of fecal and feather sampling. The study of turkey osteomyelitis complex, a disease in which bacteria are harbored in the joints and bone of normal-appearing turkeys, has suggested that the increase in L. monocytogenes isolation that occurs along the processing line may also be due to the presence of bacteria within the joints and tissues of a small percentage of turkeys. The ability of Lm to cause disease in day-old turkeys was determined by injecting low and high levels of Lm into the respiratory system. Between 25 and 100% of the birds died, depending on how much bacteria they received. Most of the birds infected with a high level of Lm died between 2 and 4 days after challenge. Signs of disease were present in the liver, heart, spleen, bursa of Fabricius, lung, and kidney. The weights of the bursa of Fabricius and the spleen, two organs important to the immune response, were affected. Lm was isolated from the liver, heart, brain, both left and right knee, gall bladder, yolk sac and cecal tonsils that were cultured for bacteria. High challenge resulted in confirmed Lm isolation from 48% of left knee and 59% of right knee cultures. Low challenge resulted in isolation of Lm from 11% of both left knee and right knee cultures. These results suggest that Lm Scott A can colonize the tissues surrounding turkey knee joints and that this infection can be the result of respiratory exposure to the bacteria.
Technical Abstract: Listeria monocytogenes contamination of poultry processing plants and products is assumed to be due to contamination with environmental bacteria and poor hygiene, and not due to carriage by poultry, based largely on studies of fecal and feather sampling. Study of turkey osteomyelitis complex, in which bacteria are harbored in the joints and bone of normal-appearing turkeys, has led us to hypothesize that the increase in L. monocytogenes isolation that occurs along the processing line may be due to endogenous bacteria within the tissues of some animals. The pathogenesis of Listeria monocytogenes strain Scott A was studied by challenging day-old male turkey poults by air sac inoculation with tryptose phosphate broth containing 10**0 cfu (Control), 10**4, 10**5, and 10**6 cfu (Low challenge) or 10**7 and 10**8 cfu (High challenge) of the Scott A (serotype 4b) strain of L. monocytogenes. Mortality at 2 weeks post-infection (PI) ranged from 25% for Low challenge to 100% for High Challenge (P = 0.0001). Gross and histopathological lesions were observed in heart, liver, spleen, lung, and bursa of Fabricius of mortalities at 4 days PI. Listeria monocytogenes challenge resulted in significantly decreased relative weight of the bursa of Fabricius and increased relative weight of the spleen and L. monocytogenes was isolated by direct plating of liver, pericardium, brain, and both left and right stifle joint synovium (knee) cultures, as well as gall bladder, yolk sac, and cecal tonsil from transfer swabs onto UVM Listeria selective agar. Isolates were confirmed as positive using Gram stain, biochemical tests, and the Biolog system. High challenge resulted in confirmed L. monocytogenes isolation from 48% of left knee and 59% of right knee cultures. Low challenge resulted in isolation of L. monocytogenes from 11% of both left and right knee cultures. These results suggest that L. monocytogenes Scott A colonization of turkey knee synovial tissue can initiate in day of age poults and that L. monocytogenes Scott A can be invasive through respiratory transmission.