COCKROACHES AS VECTORS OF SALMONELLA - LABORATORY AND FIELD TRIALS

Studies were conducted to determine if individual American, German, or Oriental cockroaches could acquire a naladixic acid-resistant strain of Salmonella typhimurium from an infected food source and then infect noncontaminated colony members, food, and water. Cockroaches, food, a nd water were sampled after 24, 48, 72, and 96 h and assayed for S. ty phimurium. Cockroaches, food, and water samples were positive for S. t yphimurium at each 24-h sampling period. American and Oriental cockroa ches were contaminated twice as often as German cockroaches. In a seco nd study, the incidence of S. typhimurium cross-contamination between 1 or 5 infected cockroaches and 10 noninfected cockroaches was followe d over 4 d. The highest frequency of cross-contamination occurred with in 24 h and declined thereafter. Water sites were heavily contaminated throughout the 4-d test period. In a third study, the potential for c ontamination of table eggs via S. typhimurium-infected cockroaches was evaluated. Whole egg rinses of eggs exposed for 24 h to infected cock roaches contained a minimum of 75 S. typhimurium cells per egg. In a f inal study, American cockroaches captured from a commercial poultry fe ed mill and hatchery were assayed for salmonellae using an ELISA metho d. Five of 45 feed mill and eight of 45 hatchery cockroach samples wer e confirmed positive for salmonellae. These findings clearly suggest t hat cockroaches are capable of acquiring and infecting other cockroach es and objects, therefore implicating them as potential vectors of foo dborne pathogens in poultry production and processing facilities.