Sequence diversity of a fragment of the 16S RNA gene from Helicobacter pylori.

Helicobacter pylori is one of the most common bacterial pathogens. It is the main cause of gastric and duodenal ulcers and has been associated with other diseases. The organism seems to be more genetically diverse than other bacterial pathogens, and the source of these differences awaits explanation. The sequence of a fragment of the 16S rRNA gene was determined for ten strains of H. pylori to examine the contribution of point mutation within a conserved gene. There were few differences between the sequences from the various strains and it was concluded that such differences were not the most important source of diversity.

Obligatory role of gamma interferon for host survival in a murine model of infection with Burkholderia pseudomallei.

Burkholderia pseudomallei, the causative agent of melioidosis, is a gram-negative bacterium capable of causing either acute lethal sepsis or chronic but eventually fatal disease in infected individuals. However, despite the clinical importance of this infection in areas where it is endemic, there is essentially no information on the mechanisms of protective immunity to the bacterium. We describe here a murine model of either acute or chronic infection with B. pseudomallei in Taylor Outbred (TO) mice which mimics many features of the human pathology. Intraperitoneal infection of TO mice at doses of >10(6) CFU resulted in acute septic shock and death within 2 days. In contrast, at lower doses mice were able to clear the inoculum from the liver and spleen over a 3- to 4-week period, but persistence of the organism at other sites resulted in a chronic infection of between 2 and 16 months duration which was eventually lethal in all of the animals tested. Resistance to acute infection with B. pseudomallei was absolutely dependent upon the production of gamma interferon (IFN-gamma) in vivo. Administration of neutralizing monoclonal antibody against IFN-gamma lowered the 50% lethal dose from >5 x 10(5) to ca. 2 CFU and was associated with 8,500- and 4,400-fold increases in the bacterial burdens in the liver and spleen, respectively, together with extensive destruction of lymphoid architecture in the latter organ within 48 h. Neutralization of either tumor necrosis factor alpha or interleukin-12 but not granulocyte-macrophage colony-stimulating factor, also increased susceptibility to infection in vivo. Together, these results provide the first evidence of a host protective mechanism against B. pseudomallei. The rapid production of IFN-gamma within the first day of infection determines whether the infection proceeds to an acute lethal outcome or becomes chronic.

An ultrastructural study of the phagocytosis of Burkholderia pseudomallei.

Burkholderia pseudomallei causes melioidosis and is believed to be an intracellular pathogen in human and animal disease. The uptake of B. pseudomallei by mouse peritoneal macrophages and cells in tissue culture was examined by electron microscopy. In all the systems studied B. pseudomallei were phagocytosed and apparently inhibited the normal processes of intracellular killing. Destruction of the phagosome membrane occurred and the bacteria escaped into the cytoplasm.

Stability of strain genotypes of Burkholderia pseudomallei from patients with single and recurrent episodes of melioidosis.

The constancy of strain genotypes of multiple isolates of Burkholderia pseudomallei from 13 patients with melioidosis was examined by BamHI ribotyping and pulsed-field gel electrophoresis (PFGE) of XbaI digests of DNA. Seven of 8 patients with single episodes of melioidosis each yielded genetically identical isolates and only one of five patients with recurrent episodes was infected with a new strain clearly distinct from the original primary strain. Variation was observed in PFGE patterns of primary and relapse isolates of another patient but this was insufficient to define genetically distinct strains. We conclude that most patients with single or multiple episodes of melioidosis retain a single strain.

Effects of Burkholderia pseudomallei and other Burkholderia species on eukaryotic cells in tissue culture.

Burkholderia pseudomallei causes melioidosis, a serious and often fatal bacterial infection. B. pseudomallei can behave as a facultatively intracellular organism and this ability may be important in the pathogenesis of both acute and chronic infection. The uptake of B. pseudomallei and other Burkholderia spp. by cells in tissue culture was examined by electron microscopy. B. pseudomallei can invade cultured cell lines including phagocytic lines such as RAW264, J774 and U937, and non-phagocytic lines such as CaCO-2, Hep2, HeLa, L929, McCoy, Vero and CHO. Uptake was followed by the intracellular multiplication of B. pseudomallei and the induction of cell fusion and multinucleate giant cell formation. Similar effects were produced by B. mallei and B. thailandensis.

Ribotyping and DNA macrorestriction analysis of isolates of Burkholderia pseudomallei from cases of melioidosis in Malaysia.

Forty-nine isolates of Burkholderia pseudomallei from sporadic cases of melioidosis in Malaysia over the past 18 years were examined by BamHI ribotyping and pulsed-field gel electrophoresis (PFGE) of XbaI digests of total deoxyribonucleic acid (DNA). Twenty-four patients had septicaemic melioidosis with a mortality of 70%; mortality in the non-septicaemic disease was 16%. Five ribotype patterns were identified, 2 of which accounted for 90% of all isolates. PFGE revealed a number of different strains within these ribotypes, but some pairs of isolates from unrelated cases gave closely similar DNA profiles. These results are in agreement with Australian studies which showed a high prevalence of a few ribotypes of B. pseudomallei which are further divisible by genotyping, in areas where melioidosis is endemic.

The ultrastructure of stressed Legionella pneumophila.

Legionellae are able to survive in natural environments which kill many other organisms. The reason for this stress resistance is not well understood nor have its morphological correlates been investigated. The ultrastructure of Legionella pneumophila subjected to stress by heat, acid and starvation, was studied by transmission electron microscopy. Heat-treated cells showed little change although cell shape tended to be distorted. Acid-treated cells showed severe shrinkage of cytoplasmic contents. Starvation caused a reduction in cell size, and after 1 month of starvation cells became fragile, although viability was not reduced.

Plasmid profiles of drug resistant Shigella boydii types 1-5, 8, 10, 12-14 from Ethiopia (1974-85).

Plasmid profile analysis by agarose gel electrophoresis was performed on 42 drug resistant strains of Shigella boydii serotypes 1-5, 8, 10, 12-14, collected between 1974 and 1985 from endemic cases of shigellosis in Ethiopia, and their Escherichia coli K12 transconjugants. Resistance factors (R factors) were further characterized by incompatibility testing. Patterns of small plasmids, less than 15 kb, were similar within each of the individual S. boydii serotypes. Plasmids of about 3.3-3.7 kb were found in all strains of serotypes 2 and 4. Plasmids of about 4.3-4.6 kb were found in about 86% of strains. Serotypes 1, 2 and 3 were characterized by plasmids of about 5.6-5.7 kb. The 6.4-6.7 kb plasmid was found consistently in serotypes 1, 2, 3, 5, 8, 12 and 13 which were resistant to SSu or had an SSu resistance component in their phenotypes. Large plasmids (155-186 kb) were found in most S. boydii strains. Conjugative drug resistance plasmids, most often coding for three or less drugs, were found in about 26% of drug resistant strains. R-factors, coding for AT resistance (in types 2 and 8), and ASSuT resistance (in type 4), were compatible with all reference plasmids tested. Plasmids belonging to incompatibility groups X and N were found in serotypes 5 and 10, respectively.

Diploma in Hospital Infection Control (Dip HIC)

The London School of Hygiene and Tropical Medicine (LSHTM) has established a Diploma in Hospital Infection Control (Dip-HIC). The course for this new Diploma is run under the auspices of the Hospital Infection Society (HIS) and the Public Health Laboratory Service (PHLS) and will commence in October 1997. The aim of this course is to provide infection control staff with systematic training in the sciences relevant to hospital infection control which will allow them to provide, and to take responsibility for, a broad-based infection control service. Topics will include the epidemiology of infectious diseases, clinical microbiology, health care economics, statistics, surveillance methods and patient management. The course will be multi-disciplinary and open to UK and overseas students, both medical and non-medical.

The study of hygiene behaviour in Botswana: a combination of qualitative and quantitative methods.

This paper describes a study from northern Botswana which explored the relationship between hygiene behaviour and diarrhoeal diseases in young children. Both qualitative and quantitative data collection methods were used. The qualitative methods included observations, key informant interviews, in-depth interviews and focus groups. The quantitative methods included spot check observations, anthropometric measurements, the monitoring of diarrhoea morbidity and the administration of a socioeconomic questionnaire. A profile of hygiene behaviours was developed for this community and traditional beliefs related to diarrhoea were identified. The methods described provided considerable information in a short period of time. They were also relatively inexpensive and easy to implement, thus providing a model for further studies dealing with hygiene behaviour in developing countries. The information gathered enabled the identification of areas needing further research, the development of health education programmes and provided the basis for larger epidemiological studies.

Understanding of hygiene behaviour and diarrhoea in two villages in Botswana.

This paper describes a study which took place in two villages in north-east district of Botswana from July 1990 through July 1991. Qualitative data collection methods were used including: observations, key-informant interviews, focus groups, and in-depth interviews. The data were used for understanding and interpreting the cultural belief systems regarding specific hygiene behaviours and diarrhoea, with emphasis on hand washing. Hand washing was said to occur for three main reasons: to remove contamination, for social reasons, and for comfort reasons. Sources of dirt on the hands included human blood and faeces. Many perceived causes of diarrhoea were identified, including pogwana (dehydration associated with sunken anterior fontanelle). Traditional concepts regarding the treatment and prevention of diarrhoea were also identified. It is suggested that beliefs surrounding hygiene behaviour and diarrhoea should be incorporated into health education programmes.

PIP: During July 1990 to July 1991, in northeastern Botswana, focus groups, observations, and interviews were conducted in two villages largely inhabited by people from the Tswana and Kalanga tribes. Researchers examined hygiene behaviors (especially hand washing) and attitudes towards infantile diarrhea in these villages. Villagers considered hand washing after defecation to be a modern idea. Hand washing was not always done, especially if one went into the bush to defecate. People considered it more important to wash hands before meals. Identified sources of contamination were one's own body (through scratching, touching oneself while urinating, blowing the nose, hands [especially the left hand], blood [especially menstrual blood], and adult feces), soil, weeds, chicken feces, laundry water, and sometimes dish-washing water, but not cow dung and mud. Hand washing after touching each source was not always done. The focus groups identified a list of words for diarrhea in Setswana and Kalanga so health workers could track diarrhea morbidity. Both languages had a word for diarrhea that characterized the condition as having more frequent stools than usual and being affected by general ill health. Pogwana referred to dehydration associated with sunken anterior fontanelle. Many mothers did not know the cause of diarrhea. Some perceived causes of diarrhea were worms in the brain or in the stomach, a bewitched child, malnutrition, teething, watermelons, contaminated water or food, or cold weather. Ways to prevent diarrhea identified by the traditional healer included not feeding the child dirty food, not storing cooked food overnight, not giving too many different foods each day, and keeping yards swept. Diarrhea treatment options were: take the child to the clinic right away; visit a faith or traditional healer; and treat the child at home with oral rehydration salts, a home-made sugar/salt solution, or a traditional herb tea. All mothers mentioned additional fluids. Traditional healers sometimes used enemas. These findings suggest that health education programs should incorporate the beliefs revolving around hygienic behavior and diarrhea.

The use of microbiology in the study of hygiene behaviour.

Faecal indicator bacteria have been used to measure levels of hygiene in a variety of settings. This paper describes a study in northern Botswana which used the isolation of faecal indicator bacteria in combination with other quantitative and qualitative techniques to gain information regarding hygiene behaviour. The microbiological samples included, samples from stored drinking water and water sources; eating plates; infant feeding bottles; dishcloths and the fingertips of carers and children. Water was usually clean at source but contaminated after storage. Presumptive faecal coliforms contaminated 31% of the eating plates, 29% of the dishcloths and 40% of the infant feeding bottles. Many of the presumptive faecal coliform isolates were not identified as Escherichia coli, indicating the need for further research into methodologies appropriate for isolating E. coli in tropical climates.

Breath methane excretion and intestinal methanogenesis in children and adults in rural Nigeria.

Breath methane excretion was measured in 274 healthy subjects from 2 rural communities in northern Nigeria. Studies in 24 adults showed a normal faecal flora with no enteric pathogens. Breath methane was detected in 122 (77%) of 159 adults, 19 (40%) of 47 older children (2-6 years), and 4 (8%) of 68 young children (< 2 years). Women were slightly more commonly breath methane-positive than men (82% versus 75%, respectively). Hyperventilation did not influence the specificity of the breath methane assay, although levels were circa 30% lower after deliberate hyperventilation. Methanogens were estimated by enrichment culture of faeces from 49 subjects. Of the subjects 76% had faecal methanogens estimated at > or = 10(2)/g, 45% at > or = 10(4)/g, and 16% at > or = 10(6)/g. There was no significant difference in distribution of methanogenic cultures between different age or tribal groups, and there were no obvious correlations between breath methane excretion and either the faecal carriage of methanogens per se or numbers present.