Rasik Khakhria

Escherichia coli O157:H7 diarrhoea associated with well water and infected cattle on an Ontario farm

A 16-month old female child living on an Ontario dairy farm was taken to hospital suffering from bloody diarrhoea. Escherichia coli O157:H7 was isolated from her stool. Initial tests of well water samples were negative for E. coli by standard methods but culture of selected coliform colonies on sorbitol-MacConkey agar led to isolation of E. coli O157:H7. E. coli O157:H7 was also isolated from 63% of cattle on the farm. The E. coli O157:H7 isolates from the child, the water and the cattle were phage type 14, produced verotoxins 1 and 2, and were highly related on analysis by pulsed field gel electrophoresis. The child did not have known direct contact with the cattle and did not consume unpasteurized milk. Hydrogeological investigation revealed the design and location of the well would allow manure-contaminated surface water to flow into the well. This investigation demonstrates that cattle farm well water is a potential source of E. coli O157:H7 which may not be identified by standard screening for E. coli in water.

Human Escherichia coli O157:H7 infection associated with the consumption of unpasteurized goat's milk

A cluster of four cases of haemolytic uraemic syndrome in children occurred in Northern Bohemia, Czech Republic, between 15 June and 7 July, 1995. All the cases had significantly elevated titres of anti-O157 lipopolysaccharide (LPS) antibodies as detected by the indirect haemagglutination assay. All but one of them had drunk unpasteurized goats milk from the same farm within the week before the disease. Evidence of E. coli O157 infection was subsequently found in 5 of 15 regular drinkers of the farms raw goats milk; four of them were asymptomatic, 1 had mild diarrhoea at the end of June. Verocytotoxin 2-producing E. coli O157:H7 strains of phage type 2 and of identical pulsed-field gel electrophoresis patterns were isolated from 1 of 2 farm goats and from 1 of the asymptomatic goats milk drinkers. The frequency of anti-O157 LPS antibodies found among regular drinkers of the farms raw goats milk (33%; 5 of 15) was significantly higher than that found in control population (0%; none of 45) (P = 0.0005; Fishers exact test). Our findings indicate that goats may be a reservoir of E. coli O157:H7 and a source of the infection for humans; raw goats milk may serve as a vehicle of the pathogen transmission.

Multiresistant Salmonella Typhimurium DT104 infections of humans and domestic animals in the Pacific Northwest of the United States.

Salmonella Typhimurium definitive type 104 with chromosomally encoded resistance to five or more antimicrobial drugs (R-type ACSSuT+) has been reported increasingly frequently as the cause of human and animal salmonellosis since 1990. Among animal isolates from the northwestern United States (NWUS), R-type ACSSuT+ Typhimurium isolates increased through the early 1990s to comprise 73% of Typhimurium isolates by 1995, but subsequently decreased to comprise only 30% of isolates during 1998. NWUS S. Typhimurium R-type ACSSuT+ were consistently (99%) phage typed as DT104 or the closely related DTu302. S. Typhimurium isolates from cattle with primary salmonellosis, randomly selected from a national repository, from NWUS were more likely to exhibit R-type ACSSuT+ (19/24, 79%) compared to isolates from other quadrants (17/71, 24%; P < 0.01). Human patients infected with R-type ACSSuT+ resided in postal zip code polygons of above average cattle farm density (P < 0.05), while patients infected with other R-types showed no similar tendency. Furthermore, humans infected with R-type ACSSuT+ Typhimurium were more likely to report direct contact with livestock (P < 0.01) than humans infected with other R-types.

Salmonella isolated from humans, animals and other sources in Canada, 1983-92.

A total of 89760 human and 22551 non-human isolates of salmonella were serotyped in Canada during the period 1983-92. There were 2180 reported outbreaks associated with 10065 cases during the 10-year period. The most common salmonella serovars isolated from human and non-human sources were S. typhimurium and S. hadar. The third and fourth most common serovars from human sources were S. enteritidis and S. heidelberg, respectively, and from non-human sources they were S. heidelberg and S. infantis. The number of S. typhimurium isolations from human and non-human sources showed a downward trend over the 10-year period. A total of 222 outbreaks of S. typhimurium associated with 1622 cases occurred. The S. hadar isolations from human and non-human sources reached a peak during the years 1987-90 and declined thereafter. The number of human isolates of S. enteritidis increased until 1985 and fluctuated at a level of 8.3-12.8% of all human isolates thereafter. Seventy-three outbreaks of S. enteritidis infection associated with 568 cases occurred. More than 50% of the S. enteritidis infections in humans were caused by phage type (PT) 8. During the review period, infections caused by PT4 were less common and were almost exclusively found in people who had travelled abroad. The annual isolation rates of S. heidelberg from human and non-human sources increased steadily during the period. Bacteriophage typing of serovars from outbreaks showed that contaminated food products of poultry and bovine origin were common sources of human infection. Salmonella typhi was identified as the cause of 43 small outbreaks affecting 116 persons.

Phage-Based Typing Scheme for Salmonella enterica Serovar Heidelberg, a Causative Agent of Food Poisonings in Canada

ABSTRACT Salmonella enterica serovar Heidelberg is perhaps the second most frequent Salmonella serovar isolated from humans and the most common isolated from animals in Canada. This pathogen has shown increasing resistance to antimicrobial agents and mimics the multidrug resistance observed in S. enterica serovar Typhimurium strain DT 104. However, unlike for serovar Typhimurium, a rapid and inexpensive subtyping method has not been available for large-scale surveillance efforts. We developed a phage typing scheme and subtyped 2,523 strains of serovar Heidelberg from outbreaks, sporadic infections, and environmental sources in Canada between January 1991 and December 2000. All strains were sensitive to one or more phages and could be subdivided into 49 phage types. A total of 196 isolates from 13 major outbreaks could be subtyped into six phage types, while 86 strains from family outbreaks were assigned to seven phage types. All strains were typeable, and epidemiologically related strains isolated from patients and implicated foods had identical phage types, antibiograms, and pulsed-field gel electrophoresis (PFGE) patterns. Combining PFGE with phage typing increased the discriminatory power of the analysis beyond that of either method alone. We concluded that this phage typing scheme, in conjunction with PFGE, enhances subtyping of serovar Heidelberg strains. Furthermore, this phage typing scheme is a rapid, economical, stable, and reliable epidemiologic tool for tracing the origin of food-borne disease and for the surveillance of sporadic infections.

Diversity of Genome Structure in Salmonella enterica Serovar Typhi Populations

The genomes of most strains of Salmonella and Escherichia coli are highly conserved. In contrast, all 136 wild-type strains of Salmonella enterica serovar Typhi analyzed by partial digestion with I-CeuI (an endonuclease which cuts within the rrn operons) and pulsed-field gel electrophoresis and by PCR have rearrangements due to homologous recombination between the rrn operons leading to inversions and translocations. Recombination between rrn operons in culture is known to be equally frequent in S. enterica serovar Typhi and S. enterica serovar Typhimurium; thus, the recombinants in S. enterica serovar Typhi, but not those in S. enterica serovar Typhimurium, are able to survive in nature. However, even in S. enterica serovar Typhi the need for genome balance and the need for gene dosage impose limits on rearrangements. Of 100 strains of genome types 1 to 6, 72 were only 25.5 kb off genome balance (the relative lengths of the replichores during bidirectional replication from oriC to the termination of replication [Ter]), while 28 strains were less balanced (41 kb off balance), indicating that the survival of the best-balanced strains was greater. In addition, the need for appropriate gene dosage apparently selected against rearrangements which moved genes from their accustomed distance from oriC. Although rearrangements involving the seven rrn operons are very common in S. enterica serovar Typhi, other duplicated regions, such as the 25 IS200 elements, are very rarely involved in rearrangements. Large deletions and insertions in the genome are uncommon, except for deletions of Salmonella pathogenicity island 7 (usually 134 kb) from fragment I-CeuI-G and 40-kb insertions, possibly a prophage, in fragment I-CeuI-E. The phage types were determined, and the origins of the phage types appeared to be independent of the origins of the genome types.

Differentiation of Clinical Helicobacter pullorum Isolates from Related Helicobacter and Campylobacter Species

Background. Helicobacter pullorum, first detected in the liver and intestinal contents of poultry, was defined as a new species in 1994. This organism has since been isolated from humans with gastroenteritis. Phenotypic as well as genotypic methods have been used to identify H. pullorum associated with cases of human disease.