A possible murine model for investigation of pathogenesis of sudden infant death syndrome.

Several studies have indicated a possible causative role of toxigenic bacteria in sudden infant death syndrome (SIDS). This study examined the effect of toxigenic E. coli on pregnant and infant mice to determine if these animals could be used as a model for SIDS pathogenesis. Strains of E. coli from the intestinal contents of infants who have died of SIDS or other causes and from the faeces of healthy infants were collected over a broad time scale. The isolates were tested for their ability to produce then known toxins of E. coli and were serotyped (O and H antigens). Certain serotypes (e.g. O1:H- and O25:H1) emerged significantly more frequently from cases of SIDS than from healthy infants and isolates of these types were generally toxigenic in Vero-cell cultures but whose verotoxicity was not related to classical Shiga or other known toxins. This mouse model was developed to test the effects of these toxigenic and also non-toxigenic strains. Four apparently healthy pups aged between 17 and 21 days died unobserved overnight but no pups of the 54 control mice died suddenly (P = 0.0247, Fisher's exact test). These were considered to represent sudden unexpected deaths. Pathological effects compatible with those in SIDS were observed in mouse pups exposed to toxigenic strains indicating this model may be suitable for further study into the pathogenesis of unexpected deaths in infancy. Providing an animal model of SIDS would promote a much better avenue for studying the pathogenesis of this enigmatic condition.

Serotypes of Escherichia coli in sudden infant death syndrome.

AIM: To examine the diversity of Escherichia coli serotypes found in the intestinal contents of infants who died of Sudden Infant Death Syndrome (SIDS) compared with that in comparison infants. METHODS AND RESULTS: Over the 3-year period, 1989-1991, in South Australia and Victoria (Australia), a total of 687 E. coli isolates from 231 patients with SIDS (348 isolates), 98 infants who had died from other causes (144 isolates) and 160 healthy infants (195 isolates) were studied. The isolates from patients with SIDS were found to represent 119 different serotypes; the isolates from 'other cause' infants represent 97 different serotypes; and the isolates from healthy infants represent 117 different serotypes. The seven common serotypes isolated most frequently from infants with SIDS belonged to those associated with extra-intestinal infections in humans. Compared to healthy infants (6%), these were found in significantly higher proportions among infants who died of other causes (13%, P < 0.05) or infants with SIDS (18.7%, P = 0.0002). CONCLUSIONS: Despite these sources yielding a wide variety of serotypes of E. coli, a pattern of certain potential pathotypes of E. coli being associated with SIDS is apparent. SIGNIFICANCE AND IMPACT OF THE STUDY: While SIDS remains one of the most important diagnoses of postneonatal death, its causes are still unexplained. If E. coli has a role in the pathogenesis of SIDS (as suggested by the pathotypes identified on the basis of serotype), further studies may reveal novel virulence factors that may clarify the role of this bacterium in SIDS.

Novel hypothesis for unexplained sudden unexpected death in infancy (SUDI).

OBJECTIVE: Two recent retrospective studies independently reported typically pathogenic bacteria in normally sterile sites of infants succumbing to sudden unexpected death in infancy (SUDI). These findings suggested a proportion of unexplained SUDI might be triggered by bacteraemia. The objective was to assess these observations in the context of the pathology and epidemiology of sudden infant death syndrome (SIDS) in relation to the role of infection and inflammation as triggers of these deaths. DESIGN: A review of the literature to identify potential risk factors for unexplained infant deaths and proposal of a theoretical model for SUDI. RESULTS: Pathologic and epidemiological evidence suggests a hypothesis based on three factors: bacterial translocation, pathogen pattern recognition insufficiency and prenatal exposure to infection. CONCLUSION: We propose that sterile site infections in which common toxigenic bacteria are identified indicate a brief bacteraemic episode prior to death. This might reflect an ineffective innate response to invasive pathogens that results in reduced clearance of the bacteria. Thymomegaly observed consistently among infants diagnosed under the category of SIDS might have its origins in prenatal life, perhaps generated via in utero infection or exposure to microbial antigens which results in thymocyte priming. There is consistent evidence for an infectious aetiology in many unexplained SUDI. Future directions for research are suggested.

Sterile site infection at autopsy in sudden unexpected deaths in infancy.

OBJECTIVE: To examine and compare bacteriological findings at autopsy of cases of sudden unexpected infant death and those of deaths from other cause. DESIGN: Autopsy report review of 130 sudden infant death syndrome (SIDS) cases (2004 definition), 32 cases of sudden unexpected death in infancy (SUDI) due to infection and 33 cases of non-infectious sudden deaths. SETTING: Qualitative assessment of normally sterile site (NSS; heart blood, spleen or cerebrospinal fluid) bacteriology in SIDS and age-matched comparison deaths that occurred in the late 1980s and early 1990s. MAIN OUTCOME MEASURES: Comparative sterile site bacteriological findings. RESULTS: Sterile site infection was rare in cases of sudden accidental death (eg, motor vehicle accident or drowning); however, the finding of true pathogens such as Staphylococcus aureus in sterile sites in SIDS and deaths associated with infection was relatively common. 10.76% of SIDS had S aureus present in a sterile site, compared with 18.75% of cases of infection-related deaths. S aureus was not found in sudden accidental deaths. The incidence of coliform bacteria in NSS in SIDS was not significantly different from that seen in deaths from other cause. NSS bacteriology yielded no growth in 45.4% of sudden accidental deaths, 43% of SIDS and 28.1% of infectious causes of death. CONCLUSIONS: The finding of S aureus in NSS in a large proportion of cases of SIDS would indicate that a proportion of these babies died of staphylococcal disease. Although the differences in NSS isolation of S aureus in the three infant groups did not quite achieve significance, on the basis of these findings and the characteristic virulence of S aureus, it is recommended that sudden unexpected deaths from which S aureus is isolated from NSS be considered for reclassification. The incidence of coliform bacteria in NSS in SIDS is not significantly different from that in deaths from another cause (both accidental and infectious). From these findings it is recommended that the opinion of a consultant microbiologist be sought to interpret microbiological findings prior to finalising autopsy reports on SUDI.

Fetal exposure to herpesviruses may be associated with pregnancy-induced hypertensive disorders and preterm birth in a Caucasian population.

OBJECTIVE: To investigate the role of fetal viral infection in the development of a range of adverse pregnancy outcomes (APOs), including pregnancy-induced hypertensive disorders (PIHD), antepartum haemorrhage (APH), birthweight <10th percentile (small for gestational age, SGA) and preterm birth (PTB). DESIGN: Population-based case-control study. SETTING: Laboratory-based study. POPULATION: The newborn screening cards of 717 adverse pregnancy cases and 609 controls. METHODS: Newborn screening cards were tested for RNA from enteroviruses and DNA from herpesviruses using polymerase chain reaction (PCR). The herpesviruses were detected using two PCRs, one detecting nucleic acids from herpes simplex virus (HSV)-1, HSV-2, Epstein-Barr virus (EBV), cytomegalovirus (CMV) and human herpesvirus (HHV)-8, hereafter designated Herpes PCR group A viruses, and the other detecting nucleic acids from varicella-zoster virus (VZV), HHV-6 and HHV-7, hereafter designated Herpes PCR group B viruses. MAIN OUTCOME MEASURE: Odds ratios and 95% CIs for specific APOs. RESULTS: For both term and PTBs, the risk of developing PIHD was increased in the presence of DNA from Herpes PCR group B viruses (OR 3.57, 95% CI 1.10-11.70), CMV (OR 3.89, 95% CI 1.67-9.06), any herpesvirus (OR 5.70, 95% CI 1.85-17.57) and any virus (OR 5.17, 95% CI 1.68-15.94). The presence of CMV was associated with PTB (OR 1.61, 95% CI 1.14-2.27). No significant association was observed between SGA or APH and exposure to viral infection. CONCLUSIONS: Fetal exposure to herpesvirus infection was associated with PIHD for both term and PTBs in this exploratory study. Exposure to CMV may also be associated with PTB. These findings need confirmation in future studies.

Sudden infant death syndrome: a critical review of approaches to research.

This review explores the various research approaches taken attempting to solve the problem of SIDS. It would appear that major clues provided by pathological findings have been largely overlooked and as a consequence much effort, time, and money has been wasted on projects that satisfy only sub-specialty and political needs. Close examination of the pathological clues would provide better insights into the mechanisms underlying this enigmatic and heartbreaking problem.

Bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease: implications for Australia.

The bovine spongiform encephalopathy (BSE) epizootic developed in the United Kingdom in the mid-1980s. Feeding practices in the cattle industry amplified the causative prion, and meat contaminated with BSE entered the market. Human consumption of prion-contaminated meat led to the new zoonosis--variant Creutzfeldt-Jakob disease (vCJD). The UK BSE Inquiry published its report in October 2000; while praising policy decisions, it also documented failures in the execution of these policies, specifically delays and lack of rigour. Australia is in an excellent position to maintain its BSE- and scrapie-free status, but widespread active surveillance of neural and non-neural tissue from all species of farmed quadrupeds is needed.

Rotavirus encephalopathy: pathogenesis reviewed.

Two cases of rotavirus gastroenteritis associated with neurological involvement, one with encephalitis (defined by abnormal neurological signs, cerebrospinal fluid (CSF) pleocytosis and detection of rotavirus genomic nucleic acid in the CSF) and one with a non-inflammatory encephalopathy (defined by abnormal neurological signs, an entirely normal CSF and detection of rotavirus genomic nucleic acid in the CSF), are presented and used as a basis to review and explore potential pathogenetic mechanisms, including direct viral replication within neurons and indirect effects of the newly described rotavirus 'enterotoxin'.

SIDS: more facts and controversies.

A more robust theory of the causation of sudden infant death syndrome (SIDS) is needed. The asphyxial theory of SIDS, which encompasses the prone sleeping position, relies on contradictory pathological evidence and fails to explain infants with SIDS who are found in the supine or lateral position. Many of the risk factors for SIDS point to an infective cause. The relative risks of these infection-related factors differ from study to study, as does the relative risk of prone sleeping position. I present the case for an infection model for SIDS causation, which has largely been neglected by mainstream SIDS researchers.

Escherichia coli 'O' group serology of a haemolytic uraemic syndrome (HUS) epidemic.

This is the first comprehensive serological analysis of a haemolytic uraemic syndrome (HUS) outbreak. A wide range of 'O' group Escherichia coli antibody responses in patients and controls was examined. The study provides a unique insight into the epidemiology of such epidemics, points a way to the most appropriate investigation of these and indicates possible answers to a number of issues related to severity of disease. In order to be able to test for a wide variety of E. coli 'O' antigens, a microagglutination assay was used to examine E. coli 'O' group serological responses of 22 children admitted to hospital with HUS and 14 contemporaneous age-matched controls. A total of 51 'O' serogroup strains were used. These included 'O' groups reported to be associated with cases of HUS, with 6 isolates from patients associated with the Adelaide outbreak (O26, O111, O123 and O157), environmental Verocytotoxigenic/Shiga-toxin producing Escherichia coli (VTEC/STEC) strains and common human commensal strains. Sixteen clinically confirmed HUS cases (72.7%) of 22 seroconverted to 1 or more serogroups of which 11 (50%) seroconverted to O111 (the serogroup isolated from 16 patients). In addition, 11 (50%) and 10 (45.5%) developed antibody to O137 and O145, respectively, although no stool isolates of these serogroups were made. Seventeen (77.3%) of 22 HUS patients had antibody to serogroup O157, with 11 (50%) seroconversions, however, O157:H- was isolated from only 2 of these. Overall, titres ranged from 100 to 6400, some of the highest in 3 patients were against O157, whose faeces yielded only Enterohaemorrhagic E. coli (EHEC) O111, and only 1 developed O111 antibody. Mixed infection was demonstrated serologically by microagglutination (confirmed by Western blot) and was consistent with the findings of multiple serogroups of VTEC found in the mettwurst incriminated as the source, and suggests further strains (not found in the source or in patients' faeces) were probably also involved. In HUS associated with EHEC infection, multiple strain infection may be the rule rather than the exception. A relationship with clinical severity deserves further investigation. Non-O157 EHEC (in addition to O157) should be sought in all future outbreaks of EHEC disease.

Association between rotavirus infection and pancreatic islet autoimmunity in children at risk of developing type 1 diabetes.

Pancreatic islet autoimmunity leading to type 1 diabetes could be triggered by viruses in genetically susceptible individuals. Rotavirus (RV), the most common cause of childhood gastroenteritis, contains peptide sequences highly similar to T-cell epitopes in the islet autoantigens GAD and tyrosine phosphatase IA-2 (IA-2), suggesting T-cells to RV could trigger islet autoimmunity by molecular mimicry. We therefore sought an association between RV infection and islet autoantibody markers in children at risk for diabetes who were followed from birth. There was a specific and highly significant association between RV seroconversion and increases in any of these antibodies: 86% of antibodies to IA-2, 62% to insulin, and 50% to GAD first appeared or increased with increases in RV IgG or IgA. RV infection may therefore trigger or exacerbate islet autoimmunity in genetically susceptible children.

New perspectives on the role of Escherichia coli O157:H7 and other enterohaemorrhagic E. coli serotypes in human disease.

This review compares the rates of detection of non-O157:H7 enterohaemorrhagic Escherichia coli (EHEC) with EHEC O157:H7 in outbreaks and sporadic cases of human disease by analysing Australian data and the world literature. Numerous outbreaks of disease have been attributed to EHEC O157:H7. In many studies, isolation rates of this organism have been low and attempts to seek other EHEC have not been made. Ease of isolation and identification of the O157:H7 serotype may have given the impression that this serotype was the sole organism responsible for the outbreaks. Careful review and analysis shows that serotypes other than O157:H7 also play an important role in human disease. Evidence is presented from several overseas outbreaks described in the literature, as well as from investigations of the Adelaide O111:H- outbreak, that suggests an association between severity of disease and multiple infecting serotypes. While not diminishing the role of the O157:H7/H- clone, this review indicates that other serotypes can be responsible for outbreaks as well as cases of sporadic human disease. The current focus on O157:H7 has major implications in terms of diagnosis, the food industry and human health.

An unusual case of microangiopathic haemolytic anaemia associated with enterohaemorrhagic Escherichia coli O113:H21 infection, a verocytotoxin-2/shiga toxin-2 producing serotype.

A case of microangiopathic haemolytic anaemia and thrombocytopaenia in a 79-year-old woman is presented. The case is unusual in that diarrhoeal symptoms were brief and symptoms of anaemia caused her to re-present to hospital 6 days after the diarrhoea had ceased. Enterohaemorrhagic Escherichia coli O113:H21 producing shiga toxin-2 was isolated from a faecal specimen. This serotype has been reported only a few times to be associated with serious disease. However, it is amongst the 20 most common serotypes carried in cattle and found in beef. This case also illustrates the importance of using shiga-toxin gene detection in faecal cultures (as opposed to cultural methods for detection of the O157:H7 serotype) as the recommended investigation of human disease for accurate epidemiology and attribution of cause.

Randomized, comparative trial of 20 micrograms vs 40 micrograms Engerix B vaccine in hepatitis B vaccine non-responders.

Fifty-two adults who had previously received 4 x 20 micrograms doses of hepatitis B [Engerix-B] vaccine (appropriately administered into the deltoid muscle) and who had failed to develop detectable anti-HBs were randomized to receive a fifth dose of Engerix-B (either 20 micrograms or 40 micrograms) intramuscularly (deltoid). The participants were blinded as to the contents of the syringe. Anti-HBs was tested (by EIA) 3 months after the injection. Anti-HBs results from 45 non-responders were evaluable. Seven vaccinees were excluded; four of these on the basis of failure to have follow-up blood collected and three who were found to be anti-HBc positive (one HBsAg positive). Twelve of 22 (54.5%) of those receiving 20 micrograms of HB vaccine developed anti-HBs, whereas 10 of 23 (43.5%) who received 40 micrograms developed anti-HBs, showing no significant difference between the regimens. The mean geometric titres were 93 +/- 50 and 86 +/- 51 IU l-1, respectively. Vaccinee groups were well matched for age, sex and body mass index and the interval between injection and bleeding. Side-effects in those receiving the double (40 micrograms) dose were no different from those receiving the normal (20 micrograms) adult dose. On the basis of this study, a fifth dose of vaccine in non-responsive vaccinees is recommended. No significant advantage of 40 micrograms over 20 micrograms of vaccine was observed. Whilst smoking and obesity were common in this cohort of non-responders and probably contributed to the individuals primary non-responsive state, these factors had no unfavourable effect on response to a fifth dose of vaccine.

Routine microbiological testing in sudden and unexpected infant death.

OBJECTIVE: To evaluate the significance of microbiological test results in a series of infants who had died suddenly and unexpectedly. METHODOLOGY: Following a review of all cases of sudden natural death in infants presenting to the Adelaide Children's Hospital (ACH) division of the Women's and Children's Hospital (WCH) over the 10 year period between 1983 and 1992, specific evaluation of microbiological test results was undertaken. RESULTS: There were 329 cases of sudden infant death syndrome (SIDS) and 23 cases in which sudden infant death was either attributed to other conditions or was unclassifiable. Positive microbiological results were recorded in the majority of cases, most being considered to be due to postmortem overgrowth or to contamination at autopsy. Of the remaining cases, microbiological results were essential to the establishment of the diagnosis in three cases, and were a useful adjunct to the diagnosis in a further six cases. CONCLUSIONS: Routine microbiological testing in cases presenting as SIDS did not reveal occult sepsis in most instances. Such testing did, however, add support to the diagnosis of SIDS where no pathogens were isolated and, if not undertaken, would have resulted in a small percentage of cases of sudden infant death due to infections remaining undiagnosed.