Salmonella and on-farm risk factors in healthy slaughter-age cattle and sheep in eastern Australia

To examine healthy slaughter-age cattle and sheep on-farm for the excretion of Salmonella serovars in faeces and to identify possible risk factors using a questionnaire. The study involved 215 herds and flocks in the four eastern states of Australia, 56 with prior history of salmonellosis. Production systems examined included pasture beef cattle, feedlot beef cattle, dairy cattle, prime lambs and mutton sheep and animals were all at slaughter age. From each herd or flock, 25 animals were sampled and the samples pooled for Salmonella culture. All Salmonella isolated were serotyped and any Salmonella Typhimurium isolates were phage typed. Questionnaires on each production system, prepared in Epi Info 6.04, were designed to identify risk factors associated with Salmonella spp excretion, with separate questionnaires designed for each production system. Salmonellae were identified in all production systems and were more commonly isolated from dairies and beef feedlots than other systems. Statistical analysis revealed that dairy cattle were significantly more likely to shed Salmonella in faeces than pasture beef cattle, mutton sheep and prime lambs (P < 0.05). A wide diversity of Salmonella serovars, all of which have been isolated from humans in Australia, was identified in both cattle and sheep. Analysis of the questionnaires showed access to new arrivals was a significant risk factor for Salmonella excretion on dairy properties. For beef feedlots, the presence of large numbers of flies in the feedlot pens or around stored manure were significant risk factors for Salmonella excretion. Dairy cattle pose the highest risk of all the slaughter-age animals tested. Some of the identified risk factors can be overcome by improved management practices, especially in relation to hygiene.

Relationship between the Physicochemical Properties of Nonchitinolytic Listeria and Salmonella and Their Attachment to Shrimp Carapace

Listeria and Salmonella are important foodborne pathogens normally associated with the shrimp production chain. This study investigated the potential of Salmonella Typhimurium, Salmonella Senftenberg, and Listeria monocytogenes (Scott A and V7) to attach to and colonize shrimp carapace. Attachment and colonization of Listeria and Salmonella were demonstrated. Shrimp abdominal carapaces showed higher levels of bacterial attachment (P < 0.05) than did head carapaces. Listeria consistently exhibited greater attachment (P < 0.05) than did Salmonella on all surfaces. Chitinase activity of all strains was tested and found not to occur at the three temperatures (10, 25. and 37 degrees C) tested. The surface physicochemical properties of bacterial cells and shrimp carapace were Studied to determine their role in attachment and colonization. Salmonella had significantly (P < 0.05) more positive (-3.9 and -6.0 mV) cell surface charge than Listeria (-18 and -22.8 mV) had. Both bacterial species were found to be hydrophilic (<35%) when measured by the bacterial adherence to hydrocarbon method and by contact angle (theta) measurements (Listeria, 21.3 and 24.8 degrees, and Salmonella, 14.5 and 18.9 degrees). The percentage of cells retained by Pheryl-Sepharose was lower for Salmonella (12.8 to 14.8%) than it was for Listeria (26.5 to 31.4%). The shrimp carapace was found to be hydrophobic (theta = 74.5 degrees), and a significant (P < 0.05) difference in surface roughness between carapace types was noted. There was a linear correlation between bacterial cell Surface charge (r(2) = 0.95) and hydrophobicity (r(2) = 0.85) and initial attachment (P < 0.05) of Listeria and Salmonella to carapaces. However, the same properties Could not be related to subsequent colonization.

Prevalence, persistence and control of Salmonella and Listeria in shrimp and shrimp products: A review.

Shrimp are an important commodity in the international fisheries trade and there is an indication of an increase in worldwide consumption of this crustacean. Salmonella and Listeria have been isolated from shrimps and shrimp products on a regular basis since the 1980s. The continued reporting of the presence of these pathogens in fresh and frozen shrimps, and even in the lightly preserved and ready-to-eat products, indicates that the existing practices used by the manufacturers or processors are insufficient to eliminate these pathogens. This paper reviews the information available on Salmonella and Listeria in shrimp and makes recommendations on control options and avenues for future research in order to improve shrimp safety and quality.

Mechanically Ventilated Broiler Sheds: a Possible Source of Aerosolized Salmonella, Campylobacter, and Escherichia coli.

This study assessed the levels of two key pathogens, Salmonella and Campylobacter, along with the indicator organism Escherichia coli in aerosols within and outside poultry sheds. The study ranged over a 3-year period on four poultry farms and consisted of six trials across the boiler production cycle of around 55 days. Weekly testing of litter and aerosols was carried out through the cycle. A key point that emerged is that the levels of airborne bacteria are linked to the levels of these bacteria in litter. This hypothesis was demonstrated by E. coli. The typical levels of E. coli in litter were similar to 10(8) CFU g(-1) and, as a consequence, were in the range of 10(2) to 10(4) CFU m(-3) in aerosols, both inside and outside the shed. The external levels were always lower than the internal levels. Salmonella was only present intermittently in litter and at lower levels (10(3) to 10(5) most probable number [MPN] g(-1)) and consequently present only intermittently and at low levels in air inside (range of 0.65 to 4.4 MPN m(-3)) and once outside (2.3 MPN m(-3)). The Salmonella serovars isolated in litter were generally also isolated from aerosols and dust, with the Salmonella serovars Chester and Sofia being the dominant serovars across these interfaces. Campylobacter was detected late in the production cycle, in litter at levels of around 107 MPN g(-1). Campylobacter was detected only once inside the shed and then at low levels of 2.2 MPN m(-3). Thus, the public health risk from these organisms in poultry environments via the aerosol pathway is minimal.

Salmonella Virchow and Salmonella Weltevreden in a Random Survey of the Asian House Gecko, Hemidactylus frenatus, in Houses in Northern Australia.

Background: Salmonella enterica serotype Virchow is the most common cause of invasive nontyphoid salmonellosis in North Queensland, particularly in infants, but the zoonotic source is unknown. This study aimed at determining (i) the prevalence of the introduced Asian house gecko, Hemidactylus frenatus, in houses in North Queensland and (ii) whether they were a potential source of Salmonella Virchow. Methods: Asian house geckos were collected in a random survey of houses in Townsville, North Queensland. Gut contents underwent microbiological analysis within 2 h of removal using both direct plating and enrichment broth methods. Any organism found to be a presumptive Salmonella spp. was then sent to a reference lab for confirmation of genus/species, serotyping, and phage typing if indicated. Results: One hundred Asian house geckos were collected from 57 houses. Geckos were present in 100% of houses surveyed, and prevalence of Salmonella in large intestinal contents was 7% (95% confidence interval 2, 12%). Three serotypes were found: Virchow (phage type 8), Weltevreden, and an untypable subspecies 1 serotype 11:-:1,7. Conclusion: Since Salmonella Virchow (phage type 8) is associated with invasive disease, the introduced Asian house gecko may play a significant role in the epidemiology of sporadic salmonellosis in places invaded by these peridomestic reptiles. These results justify more detailed epidemiological studies on the role of the Asian house gecko in sporadic salmonellosis and development of evidence-based strategies to decrease this potential zoonotic hazard.

Impact of the Australian litter re-use practice on Salmonella in the broiler farming environment

This study has examined the dynamics (in terms of levels and serovar diversity) of Salmonella in the "dual litter environment" that occurs within a single shed as a result of a management practice common in Australia. The study also looked at the physical parameters of the litter (pH, moisture content, water activity and litter temperature) as a means of understanding the Salmonella dynamics in these litter environments. The Australian practice results in the brooder end of the shed having new litter each cycle while the grow-out end has re-used litter (a "dual litter environment"). Two farms that adopted this partial litter re-use practice were studied over one full broiler cycle each. Litter was sampled weekly for the levels (and serovars) of Salmonella during a farming cycle. There was a trend for lower levels of Salmonella (and a lower Salmonella serovar) diversity in the re-used litter environment as compared with the new litter environment. Of the physical parameters examined, it would appear that the lower water activity associated with the re-used litter may contribute to the Salmonella dynamics in the dual environment.