Narelle Fegan

Isolation and characterisation of Arcobacter butzleri from meat

A survey was conducted to determine the prevalence of Arcobacter in ground chicken, pork, beef and lamb meats. Meat samples were enriched in Arcobacter broth (AB) containing cefoperazone, amphotericin and teicoplanin (CAT) supplement. Samples were screened for the presence of Arcobacter spp. using a multiplex polymerase chain reaction (PCR) followed by isolation on blood and selective agar. Arcobacter butzleri was the only species of Arcobacter isolated from 35% of 88 samples of ground meats. A. butzleri was more frequently isolated from poultry (73%) than pork (29%), beef (22%) or lamb (15%) samples. No significant differences were found in the isolation rates and from the different regions sampled. Isolates were characterised by pulsed-field gel electrophoresis (PFGE) using SacII, EagI and SmaI restriction endonucleases. A number of isolates with indistinguishable PFGE fingerprints were found to be epidemiologically related, which may indicate cross-contamination of common types of Arcobacter from different meat species or between meat species. The public health significance of Arcobacter in ground meat needs to be determined.

Attachment of different Salmonella serovars to materials commonly used in a poultry processing plant

Salmonella can adhere to poultry and food contact surfaces and persist to cause diseases. Adhesion of Salmonella Sofia (n = 14), S. Typhimurium (n = 6), S. Infantis (n = 3) and S. Virchow (n = 2) to Teflon, stainless steel, glass, rubber and polyurethane were assayed using epifluorescence microscopy. Surface free energies of bacteria and materials were calculated using contact angle values and interfacial free energy between isolates and materials determined. Surface roughness of the materials was analysed using atomic force microscopy. S. Sofia isolates adhered in higher numbers (P < 0.05) to all materials compared to other serovars. The mean number of cells of S. Sofia isolates attaching to Teflon were significantly higher (P < 0.05) compared to all materials except stainless steel (P > 0.05). Mean roughness values ranged from 82.26 nm (Teflon) to 1.34 nm (glass). Correlations between the apolar component of the surface free energy of materials (gamma(S)(LW)) and bacterial adhesion (R(2) = 0.80), and between gamma(S)(LW) and the surface roughness of the materials (R(2) = 0.71) were found. Materials more positive in interfacial free energies had the highest number of adhering bacteria. Generalised surface property measurements were found to be useful in characterising Salmonella attachment but the degree of variability in results suggests that other factors, such as flagella or membrane proteins, could also contribute.

The prevalence and concentration of Escherichia coli O157 in faeces of cattle from different production systems at slaughter

Aims:  To determine the prevalence and concentration of Escherichia coli O157 shed in faeces at slaughter, by beef cattle from different production systems.

Enumeration of Escherichia coli O157 in cattle faeces using most probable number technique and automated immunomagnetic separation

Aims:  To determine the numbers of Escherichia coli O157 present in the faeces of naturally infected cattle.

Population structure and diversity of avian isolates of Pasteurella multocida from Australia.

A total of 110 isolates of Pasteurella multocida from Australian poultry and reference strains for the 16 somatic serovars plus the three subspecies (gallicida, multocida, septica) were analysed to examine their population structure and diversity. The 81 field isolates examined by multilocus enzyme electrophoresis (MLEE) were diverse, being divided into 56 electrophoretic types (ETs), with the 19 reference strains in another 15 ETs. The population was clonal and somatic serotyping was not particularly useful in establishing relationships between isolates. The 71 ETs formed three distinct subclusters (A, B and C) at a genetic distance of 0.36. Biovars tended to be associated with these subclusters: A with biovars 1, 3, 4, 5 and 8 and B with biovars 2, 6, 7, 9 and 10. Ribotyping, performed on all 110 isolates using Hpall, recognized 21 ribotypes forming nine clusters (R1-R9). The isolates in ribotype cluster R1 were almost identical to those in MLEE cluster B. Using both MLEE and ribotyping, the 19 non-Australian reference strains were found to be distributed over the full diversity of the Australian isolates of P. multocida. This study has shown that a range of P. multocida clones are associated with fowl cholera in Australia and that many of the Australian isolates are similar to non-Australian reference strains. Both the MLEE results and the ribotyping data identified a previously unrecognized subset of P. multocida strains.

Phenotypic characterisation of Pasteurella multocida isolates from Australian poultry.

A phenotypic characterisation of 110 isolates of bacteria previously identified as Pasteurella multocida was performed. Reference strains of many of the currently recognised species within the genus Pasteurella were included in the study. All the isolates had been obtained from Australian poultry-67 from chickens, 42 from turkeys and one from a duck. Ten different biochemical biovars were recognised amongst the isolates. Four of these biovars, representing 91 isolates, were identified as P. multocida subsp. multocida. One biovar, consisting of one isolate, was identified as P. multocida subsp. septica and another biovar, consisting of five isolates, as P. multocida subsp. gallicida. Two further biovars were tentatively identified as ornithine decarboxylase negative P. multocida subsp. multocida (five isolates) and maltose positive P. multocida subsp. septica (one isolate). The final two biovars, consisting of five and two isolates each, could not be assigned to any of the currently recognised subspecies of P. multocida.

Distribution, prevalence and persistence of Cronobacter (Enterobacter sakazakii) in the nonprocessing and processing environments of five milk powder factories

Aims:  To characterise the occurrence of Cronobacter in milk powder factories.

An investigation of Escherichia coli O157 contamination of cattle during slaughter at an abattoir.

The extent of contamination with Escherichia coli O157 was determined for 100 cattle during slaughter. Samples from 25 consecutively slaughtered cattle from four unrelated groups were collected from the oral cavity, hide, rumen, feces after evisceration, and pre- and postchill carcass. Ten random fecal samples were collected from the pen where each group of animals was held at the abattoir. E. coli O157 was detected using automated immunomagnetic separation (AIMS), and cell counts were determined using a combination of most probable number (MPN) and AIMS. E. coli O157 was isolated from 87 (14%) of the 606 samples collected, including 24% of 99 oral cavity samples, 44% of 100 hides, 10% of 68 fecal samples collected postevisceration, 6% of 100 prechill carcass swabs, and 15% of 40 fecal samples collected from holding pens. E. coli O157 was not isolated from rumen or postchill carcass samples. E. coli O157 was isolated from at least one sample from each group of cattle tested, and the prevalence in different groups ranged from less than 1 to 41%. The numbers of E. coli O157 differed among the animals groups. The group which contained the highest fecal (7.5 x 10(5) MPN/g) and hide (22 MPN/cm2) counts in any individual animal was the only group in which E. coli O157 was isolated from carcasses, suggesting a link between the numbers of E. coli O157 present and the risk of carcass contamination. Processing practices at this abattoir were adequate for minimizing contamination of carcasses, even when animals were heavily contaminated with E. coli O157.

Quantification and prevalence of Salmonella in beef cattle presenting at slaughter

Aims:  A survey to determine the prevalence and numbers of Salmonella in beef cattle presented for slaughter at abattoirs across Australia was conducted between September 2002 and January 2003.

The molecular epidemiology of four outbreaks of porcine pasteurellosis

Biochemical profiles, restriction endonuclease analysis (REA) and ribotyping were used to investigate a total of 38 Pasteurella multocida isolates from four separate outbreaks of pasteurellosis in Australian piggeries. Six isolates were obtained from Outbreak 1, 16 from Outbreak 2 and eight each from outbreaks 3 and 4. Outbreaks 1 and 2 were cases of pneumonic pasteurellosis while outbreaks 3 and 4 involved systemic pasteurellosis. Biochemical characterisation established that a number of different types of P. multocida were present in outbreaks 1 and 3 while outbreaks 2 and 4 were associated with a single type of P. multocida. Outbreaks 1 and 3 yielded isolates of P. multocida that belonged to the subspecies multocida and gallicida, with the subspecies multocida isolates being identified as biovar 3 (6 in total) or 12 (1 in total) and the subspecies gallicida isolates (7 in total) being identified as biovar 8. All 24 isolates from outbreaks 2 and 4 belonged to the subspecies multocida and were all biovar 3. REA and ribotyping showed that, in outbreaks 1 and 3, there were three different types of P. multocida in each outbreak with no common strains between the outbreaks. The molecular methods showed that only a single strain of P. multocida was associated with outbreaks 2 and 4, although the outbreaks were associated with strains that differed in REA profiles but shared a ribotype profile. This study has shown that both, systemic and pneumonic pasteurellosis can be associated with either a single strain or multiple strains of P. multocida. The results also indicate that the molecular typing methods of REA and ribotyping are superior to biochemical characterisation for epidemiological investigation of porcine pasteurellosis.