A national case-control study of risk factors for listeriosis in Australia.

Listeriosis is a foodborne disease associated with significant mortality. This study attempts to identify risk factors for sporadic listeriosis in Australia. Information on underlying illnesses was obtained from cases' treating doctors and other risk factors were elicited from the patient or a surrogate. We attempted to recruit two controls per case matched on age and primary underlying immune condition. Between November 2001 and December 2004 we recruited 136 cases and 97 controls. Of perinatal cases, living in a household where a language other than English was spoken was the main risk factor associated with listeriosis (OR 11·3, 95% CI 1·5-undefined). Of non-perinatal cases we identified the following risk factors for listeriosis: prior hospitalization (OR 4·3, 95% CI 1·0-18·3), use of gastric acid inhibitors (OR 9·4, 95% CI 2·4-37·4), and consumption of camembert (OR 4·7, 95% CI 1·1-20·6). Forty percent of cases with prior hospitalization were exposed to high-risk foods during hospitalization.

Risk factors for infection with Campylobacter jejuni flaA genotypes.

We aimed to explore Campylobacter genotype-specific risk factors in Australia. Isolates collected prospectively from cases recruited into a case-control study were genotyped using flaA restriction fragment-length polymorphism typing (flaA genotyping). Exposure information for cases and controls was collected by telephone interview. Risk factors were examined for major flaA genotypes using logistic and multinomial regression. Five flaA genotypes accounted for 325 of 590 (55%) cases - flaA-6b (n=129), flaA-6 (n=70), flaA-10 (n=48), flaA-2 (n=43), flaA-131 (n=35). In Australia, infections due to flaA-10 and flaA-2 were found to be significantly associated with eating non-poultry meat (beef and ham, respectively) in both case-control and inter-genotype comparisons. All major genotypes apart from flaA-10 were associated with chicken consumption in the case-control comparisons. Based on several clinical criteria, infections due to flaA-2 were more severe than those due to other genotypes. Thus genotype analysis may reveal genotype-specific niches and differences in virulence and transmission routes.

Sesame seed products contaminated with Salmonella: three outbreaks associated with tahini.

In November 2002, the first of three outbreaks of Salmonella Montevideo infection in Australia and New Zealand was identified in New South Wales, Australia. Affected persons were interviewed, and epidemiologically linked retail outlets inspected. Imported tahini was rapidly identified as the source of infection. The contaminated tahini was recalled and international alerts posted. A second outbreak was identified in Australia in June-July 2003 and another in New Zealand in August 2003. In a total of 68 S. Montevideo infections, 66 cases were contacted. Fifty-four (82%) reported consumption of sesame seed-based foods. Laboratory analyses demonstrated closely related PFGE patterns in the S. Montevideo isolates from human cases and sesame-based foods imported from two countries. On the basis of our investigations sesame-based products were sampled in other jurisdictions and three products in Canada and one in the United Kingdom were positive for Salmonella spp., demonstrating the value of international alerts when food products have a wide distribution and a long shelf life. A review of the controls for Salmonella spp. during the production of sesame-based products is recommended.

Immune response of children who develop persistent diarrhea following rotavirus infection.

A prospective study was conducted with Bangladeshi children with rotavirus (RV) diarrhea to assess whether nutritional and clinical parameters, RV serotypes, levels of interleukin-10 (IL-10), tumor necrosis factor alpha (TNF-alpha), and gamma interferon (IFN-gamma), and RV-specific antibody titers in plasma and stool were associated with the development of persistent diarrhea. Children with watery diarrhea for 6 to 8 days, selected from the Dhaka Hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), were enrolled in the study and monitored until diarrhea improved. Children were classified as having acute diarrhea (AD) if diarrhea resolved within 14 days of onset and as having persistent diarrhea (PD) if diarrhea persisted for more than 14 days after onset. Uninfected, control children (n = 13) from the Nutrition Follow-Up Unit of ICDDR,B were also enrolled. Of the 149 children with diarrhea enrolled, 29 had diarrhea with RV alone, of which 19 had AD and 10 developed PD. Samples of stool and blood were collected from all children on enrollment. Stool samples were collected again from children when they developed PD. Of the 10 children who had an initial RV infection and then developed PD, only one had persistent RV infection. Plasma levels of IL-10 and TNF-alpha were higher in children with diarrhea compared to uninfected controls but were similar in children with AD and PD. Plasma IFN-gamma levels were higher in children who developed PD than in those with AD (P = 0.008) or uninfected controls (P = 0.001). In stools, the levels of TNF-alpha, the only cytokine detected, were similar in the three groups of children. RV-specific immunoglobulin G (IgG) titers in plasma were higher in uninfected children than in those with AD (P < 0.001) or PD (P = 0.024) but titers were similar in children with AD and PD. RV-specific IgA titers in plasma and stool were similar in the three groups of children. From all observed parameters, only elevated plasma IFN-gamma levels were associated with subsequent development of PD. However, a larger sample size is necessary to substantiate this observation.

Evidence of high-frequency genomic reassortment of group A rotavirus strains in Bangladesh: emergence of type G9 in 1995.

We characterized 1,534 rotavirus (RV) strains collected in Bangladesh from 1992 to 1997 to assess temporal changes in G type and to study the most common G and P types using reverse transcription-PCR, oligonucleotide probe hybridization, and monoclonal antibody-based enzyme immunoassay. Results from this study combined with our previous findings from 1987 to 1991 (F. Bingnan et al., J. Clin. Microbiol. 29:862-868, 1991, and L. E. Unicomb et al., Arch. Virol. 132:201-208, 1993) (n = 2,515 fecal specimens) demonstrated that the distribution of the four major G types varied from year to year, types G1 to G4 constituted 51% of all strains tested (n = 1,364), and type G4 was the most prevalent type (22%), followed by type G2 (17%). Of 351 strains tested for both G and P types, three globally common types, type P[8], G1, type P[4], G2, and type P[8], G4, comprised 45% (n = 159) of the strains, although eight other strains were circulating during the study period. Mixed G and/or P types were found in 23% (n = 79) of the samples tested. Type G9 RVs that were genotype P[6] and P[8] with both long and short electrophoretic patterns emerged in 1995. The finding of five different genotypes among G9 strains, of which three were frequently detected, suggests that they may have an unusual propensity for reassortment that exceeds that found among the common G types. We also detected antigenic changes in serotypes G2 and G4 over time, as indicated by the loss of reactivity with standard typing monoclonal antibodies. Our data suggest that a vaccine must provide protection against type G9 RVs as well as against the four major G types because G9 strains constituted 16% (n = 56) of the typeable RV strains and have predominated since 1996.

Astrovirus infection in association with acute, persistent and nosocomial diarrhea in Bangladesh.

BACKGROUND: Diarrhea is an important public health concern in developing countries such as Bangladesh. Diarrhea in children that persists for 14 days or more occurs in 7% of patients in Bangladesh and frequently results in death. Astrovirus has been demonstrated as a cause of acute and nosocomial diarrhea and can be excreted for prolonged periods, yet its importance as a cause of diarrhea among children in a developing country like Bangladesh has not been investigated. METHODS: We tested 629 stool specimens from patients with acute diarrhea, 153 from patients with persistent diarrhea, 175 specimens from 76 patients hospitalized for diarrhea who were sampled repeatedly to detect nosocomial infection and 428 from nonhospitalized healthy children (controls). All children enrolled in the study were <5 years of age. Astrovirus was detected by enzyme immunoassay and other enteropathogens were detected by standard techniques. RESULTS: The detection of astrovirus increased significantly with the duration of diarrhea. Astrovirus was found in 23 (15%) specimens from patients with persistent diarrhea, 26 (4%) patients with acute diarrhea, but only 8 (2%) healthy controls. This trend remained when we limited our analysis to infants <12 months of age and to episodes in which astrovirus was the sole pathogen. Among patients with nosocomial diarrhea, 16% of postadmission specimens were positive for astrovirus when the admission specimen was negative. CONCLUSION: The observation that astrovirus is detected more frequently with diarrhea of increasing duration suggests the need for further studies to determine whether astrovirus plays a causative role in persistent diarrhea or is a secondary agent.

Anticipating rotavirus vaccines: hospital-based surveillance for rotavirus diarrhea and estimates of disease burden in Bangladesh.

OBJECTIVES: Rotavirus is the most common cause of severe diarrhea in children worldwide, and a vaccine may soon be licensed and available for use in immunization programs. To assess the need for a rotavirus vaccine in Bangladesh, we estimated the disease burden of rotavirus diarrhea from national vital statistics for births and diarrheal deaths, together with hospital surveillance data on the proportion of severe childhood diarrhea attributed to rotavirus. METHODS: From 1990 through 1993, hospital surveillance was conducted of a systematic, random 4% sample of >80,000 patients with diarrhea who sought care each year at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B). RESULTS: Rotavirus was detected in 20% (1561 of 7709) of fecal specimens from children with diarrhea <5 years of age; 92% of all cases (1436) occurred in children <2 years of age, but only 3% (50) of cases occurred in infants <3 months of age. Children infected with rotavirus were more likely to have watery stools (P < 0.001), severe vomiting (P < 0.001) but less severe dehydration (P = 0.007) than children infected with other enteropathogens. CONCLUSIONS: We estimate that in this setting, where 18% of children die by age 5 and about 25% of these succumb to diarrhea, between 14,850 and 27,000 of the 3 million Bangladeshi children born in 1994 will die of rotavirus by the age of 5 years, equivalent to 1 rotavirus death per 111 to 203 children. The estimated burden of rotavirus diarrhea in Bangladesh is sufficiently great to warrant field testing of rotavirus vaccines for possible inclusion in the current immunization program.

Neonatal rotavirus infection in Bangladesh: strain characterization and risk factors for nosocomial infection.

BACKGROUND: Rotavirus (RV) diarrhea is an important cause of childhood morbidity and mortality in Bangladesh and is responsible for 24% of hospital admissions for diarrhea in children from 3 months to 2 years of age. However, the prevalence of neonatal RV infections and characteristics of RV strains infecting neonates have not been explored in Bangladesh. METHODS: We investigated neonates at six hospitals in Bangladesh to determine the prevalence of neonatal RV infection, to identify risk factors for infection and to characterize neonatal RV strains by reverse transcription-polymerase chain reaction. RESULTS: Of 381 neonates screened at 6 hospitals 61 of 146 infants (42%) at 2 hospitals in Dhaka were RV-positive. Of these 62% were detected within the first 5 days of life. We found an increased risk for neonatal RV infection among infants whose mothers reported no handwashing during care of the neonate (P = 0.03). Analysis of RV strains in enzyme-linked immunosorbent assay-positive specimens identified P[6]G4 and P[6]G1 genotypes to be most common; 7% (2 of 27) of strains were nontypable. A concurrent analysis of RV strains circulating in Bangladesh suggested that RV genotypes infecting neonates had a distinct P genotype, because most community strains were P-nontypable compared with neonatal strains, which carried the P[6] genotype. CONCLUSIONS: Hospitalized neonates in Dhaka have increased risk for infection with RV as early as the first week of life with strains having the unusual P[6] genotype. Our findings confirm studies in India showing that neonatal RV infection can be common and may occur with strains distinct from those circulating in the community. Neonatal RV infections could alter a child's response to the RV vaccine as well as the calculation of RV vaccine efficacy in these populations.

Demonstration of a lack of synergistic effect of rotavirus with other diarrheal pathogens on severity of diarrhea in children.

The severity of group A rotavirus (RV) diarrhea was compared with that of mixed infections of RV with diarrheagenic Escherichia coli, Vibrio cholerae O1, and Shigella species by a scoring system. The severity of mixed infections of RV and E. coli was the same as that of infections with RV alone. RV infections mixed with V. cholerae and Shigella species mimicked cholera and shigellosis, respectively.

Previous enteric adenovirus infection does not protect against subsequent symptomatic infection: longitudinal follow-up of eight infants.

Eight infants followed longitudinally were found to have enteric adenovirus (EAdv) infections: in 5 infants with diarrhea and in 3 with no accompanying diarrhea. Sequential stool samples prior to EAdv infections were tested for adenovirus antigen, anti-adenoviral IgA and neutralizing antibodies to serotypes 40, 41 and 2 in order to ascertain whether protection from symptoms was due to prior infection. No difference was found in the number of adenoviral infections among infants prior to their EAdv infections with or without accompanying diarrhea. However, in 3 of the 5 infants in whom EAdv infection was accompanied by diarrhea and 2 of 3 control infants, previous EAdv infections had occurred as detected by serotype-specific antibody rises.

Rotavirus serotypes causing severe acute diarrhea in young children in six Australian cities, 1989 to 1992.

Rotavirus VP7 serotypes were identified in stools from 72.9% (1,302/1,784) of hospitalized Australian children in six cities (1989 to 1992) and comprised 1,088 (83.6%) serotype G1 isolates, 84 (6.4%) serotype G2 isolates, 64 (4.9%) serotype G3 isolates, 49 (3.8%) serotype G4 isolates, and 17 (1.3%) isolates of mixed serotypes. The most densely populated cities yielded the greatest diversity of serotypes.

Evaluation of a probe hybridisation serotyping method for group A rotavirus.

Serotype-specificity and sensitivity of oligonucleotide probes to serotype human rotaviruses was assessed. Probes could detect as little as 6.3 ng of homologous RNA and none reacted with as much as 100 ng of heterologous RNA. Northern-blot analysis revealed that probes reacted with one of genomic segments 7, 8 or 9 of corresponding serotypes.

Enteric adenovirus infection among infants with diarrhea in rural Bangladesh.

A total of 4,409 stool specimens from infants less than 5 years of age seeking treatment for diarrhea in Matlab, Bangladesh, were tested for the presence of adenoviruses by using an enzyme immunoassay (EIA). EIA-positive stool samples were serotyped with monoclonal antibodies specific for adenovirus type 40 (Ad40) and Ad41 and group antigen, inoculated into Graham G293 cells, and retested by EIA. Of adenovirus-positive cultures, 125 (2.8%) specimens were confirmed as enteric adenoviruses (EAds), of which 51 (40.8%) were typed as Ad40 and 74 (59.2%) were typed as Ad41, and 12 of 4,409 (0.3%) were identified as nonenteric adenoviruses. A slight peak of incidence of EAd infection was observed in the cool, dry months, and an outbreak of Ad40 infections occurred in March 1988, when the detection rate of EAd reached 12.3%. Information on age, gender, and symptoms was available for 80 infants infected with adenovirus only. Age distribution was similar for types 40 and 41 and nonenteric adenovirus; the median ages were 11, 12, and 12 months, respectively. The ratio of males to females for the 80 infants varied according to serotype; Ad40 had the highest male/female ratio, 2.17. The symptoms experienced by the 80 children were similar for each adenovirus type. The most common clinical features of EAd infection were watery diarrhea (87.5%), more than eight loose bowel movements per day in the 24-h period prior to presentation (68.8%), with vomiting (80.0%), abdominal pain (76.3%), and low-grade fever (95.0%); these symptoms are significantly similar to symptoms of infants infected with group A rotavirus. EAd infection generally gave rise to mild to moderate dehydration, which is significantly similar to dehydration produced by infection with rotavirus.

A one-year survey of rotavirus strains from three locations in Bangladesh.

Group A rotavirus strains from 3 locations in Bangladesh collected over one year were examined. Serotypes 1-4 were found throughout in 2 locations, whereas an epidemic of RV diarrhoea due to a single rotavirus strain occurred in one location.

Seroprevalence of enteric and nonenteric adenoviruses in Bangladesh.

Single serum samples obtained from infants between 0 and 24 months of age admitted to a diarrheal disease hospital in Bangladesh were tested for the presence of adenovirus-specific immunoglobulin G (IgG) and IgA antibodies by using enzyme immunoassay and neutralizing antibodies to adenovirus types 2, 40, and 41. IgG antibodies were more prevalent than IgA antibodies, and neutralizing activity to enteric adenovirus was found in serum samples from 50% of infants who had reached 2 years of age.

Cultivation and characterization of novel human group A rotaviruses with long RNA electropherotypes, subgroup II specificities, and serotype 2 VP7 genes.

During an epidemiological study of human rotavirus infections in Bangladesh, three group A strains hybridized with a serotype 2 oligonucleotide probe, but they had long RNA electropherotypes. The three strains were collected from 8- to 20-month-old infants with acute diarrhea and moderate malnutrition. By a modified isolation procedure, two strains (T-B and T-C) were adapted in MA104 cell cultures. They were identified to be subgroup II specific by enzyme-linked immunosorbent assay with subgroup I- and II-specific monoclonal antibodies and were identified by a fluorescent focus reduction neutralization assay with hyperimmune antisera to be serotype 2 specific. Further characterization of these unusual rotavirus strains needs to be carried out.

Epidemiology of rotavirus serotypes in Melbourne, Australia, from 1973 to 1989.

Fecal rotavirus strains collected between 1973 and 1989 from 943 children admitted with acute diarrhea to one hospital in Melbourne, Australia, were serotyped by using an enzyme-linked immunosorbent assay. The assay incorporated neutralizing monoclonal antibodies specific for VP7 of the four major human serotypes (1 through 4). A serotype could be assigned to 690 of 943 specimens (73.2%). Typeable strains comprised serotype 1 (72.5%), serotype 2 (6.8%), serotype 3 (2.9%), or serotype 4 (15.4%). Monotypes 1a and 1c comprised 52 and 44%, respectively, of serotype 1 strains. All serotypes and monotypes exhibited polymorphic genomic RNAs. Specimens reacting as mixed serotypes were rare (3.2%) and included intertypic strains (0.7%) and mixed infections (1.0%). Nontypeable strains for which an electropherotype could be determined appeared to be identical with typeable strains present concurrently in the community. Serotypes exhibited various epidemiological patterns. Serotype 1 strains were dominant except during three successive winters when 60 to 90% of the disease was caused by serotype 2. Serotype 4 strains showed an episodic pattern of appearance, recurring at peak incidence approximately every 3 years. Fecal rotavirus strains collected from 145 newborn babies housed in Melbourne obstetric hospitals between 1974 and 1986 were also serotyped. All 135 typeable strains (93.1%) belonged to serotype 3. It is hypothesized that endemic infection with serotype 3 rotaviruses in nurseries for the newborn influenced the epidemiology of rotavirus serotypes responsible for severe clinical disease in young children in the same community.

Rotavirus infection detected in neonates from hospitals in urban Bangladesh.

A study of neonatal group A rotavirus (RV) infection in 3 hospitals of urban Bangladesh identified 60 infected babies of 100 studied in 2 hospitals. Preliminary evidence based on serotyping and electropherotyping suggest that these RVs differ from community strains.

Serotyping of human group A rotavirus with oligonucleotide probes.

Rotaviruses (RV) in stools of children with diarrhea in Thailand were serotyped by monoclonal enzyme immunoassay (MEIA), and RNA extracted from these specimens were tested for hybridization with oligonucleotides constructed from the nucleotide sequences of VP7 of human serotypes 1, 2, 3, and 4. Of 178 specimens that contained RV as identified with a monoclonal antibody to group A RV, 84% (149/178) hybridized with serotype-specific oligonucleotides, and 42% (74/178) were serotyped by MEIA (P less than .001). Of the 74 specimens that were serotyped by MEIA, 92% (35/38) of type 1, 97% (34/35) of type 2, and the one type 4 RV hybridized with the HuG1Ac, HuG2Ac, and HuG4Ac oligonucleotides, respectively. RV strains identified in children in Thailand in 1987 and 1988 to which a serotype could be assigned by either method were either type 1, type 2, or, less often, type 4. Testing RV for hybridization with oligonucleotides for genes encoding VP7 is an alternate method of determining RV serotypes.

Experience with an enzyme immunoassay for serotyping human group A rotaviruses.

An enzyme immunoassay utilizing neutralizing monoclonal antibodies to VP7 of four human group A rotavirus serotypes successfully typed rotaviruses in 71.4% (568 of 796) of fecal specimens. Sensitivity was enhanced by using homologous capture and detector antibodies. Serotyping was most successful with specimens stored for less than 3 years and containing 10(4) or more particles per ml.