rDNA fingerprinting as a tool in epidemiological analysis of Salmonella typhi infections.

Characterization of 169 strains of Salmonella typhi of phage types C1, C4, D1 and D9 isolated in 1975-88 was carried out by rDNA gene restriction pattern analysis. Twenty-four isolates had been recovered during four large waterbone outbreaks in the last 20 years in Sicily; 145 strains, isolated from apparently sporadic cases of infection in Southern Italy in the same period of time, were also examined. Application of rRNA-DNA hybridization technique after digestion of chromosomal DNA with Cla I showed the identity of patterns of the epidemic strains of phage types C1 and D1, confirming attribution of the outbreaks to single bacterial clones. Patterns of the two available strains of lysotype D9 were slightly different, whilst the 12 epidemic strains of phage type C4 could be assigned to two distinct patterns scarcely related to each other and, consequently, to two different clones. A considerable heterogeneity was detected among all apparently sporadic isolates of the four phage types under study. This fingerprinting method appears a reliable tool to complement phage typing in characterizing isolates of S. typhi. In particular, epidemiological features of spread of this salmonella serovar in areas, where simultaneous circulation of indigenous and imported strains occurs, can be elucidated.     

IS200 fingerprinting of Salmonella enterica serotype Abortusovis strains isolated in Iran

Salmonella enterica serovar Abortusovis is one of the most common pathogens responsible for abortion in sheep. In Iran, the spread of Abortusovis is highly dependent on the nomadic life style. In this study we performed IS200 fingerprinting to identify the clonal lines circulating in Iran. All the isolates contained 4 or 5 copies of the transposon and could be classified in 4 genotypes. A single genotype was highly prevalent and very likely it has circulated in Iran since 1970. All the isolates showed a high degree of relatedness.     

Restaurant-associated outbreak of Salmonella typhi in Nauru: an epidemiological and cost analysis.

Typhoid fever is endemic in the South Pacific. We investigated an outbreak in Nauru. Through interviews and medical records, we identified 50 persons with onset between 1 October 1998 and 10 May 1999, of fever lasting > or = 3 days and one other symptom. Salmonella Typhi was isolated from 19 (38%) cases. Thirty-two (64%) patients were school-aged children, and 17 (34%) were in four households. Case-control studies of (a) culture-confirmed cases and age- and neighbourhood-matched controls; and (b) household index cases and randomly selected age-matched controls implicated two restaurants: Restaurant M (matched OR [MOR] = 11, 95% confidence interval [CI] = 1.3-96) and Restaurant I (MOR = 5.8, 95% CI = 1.2-29). Food-handlers at both restaurants had elevated anti-Vi antibody titres indicative of carrier state. The annual incidence was 5.0/1000 persons. Outbreak-associated costs were $46,000. Routine or emergency immunization campaigns targeting school-aged children may help prevent or control outbreaks of typhoid fever in endemic disease areas.     

Genome fingerprinting of Salmonella typhi by pulsed-field gel electrophoresis for subtyping common phage types.

The genomic DNA of 39 strains of Salmonella typhi isolated from local residents and patients who had visited countries in the Asian region was analysed for restriction fragment length polymorphisms (RFLP). Pulsed-field gel electrophoretic (PFGE) analysis of Xba I- and Spe I-generated genomic restriction fragments established 22 PFGE types whereas phage typing differentiated the 39 isolates into 9 distinct phage types. This study showed that PFGE is more discriminatory than phage typing as it is capable of subtyping S. typhi strains of the same phage types. Genetic relatedness among the isolates was determined. Seven major clusters were identified at SABs of > 0.80 and the remaining 13 isolates were distributed into minor clusters which were related at SABs of less than 0.80. In conclusion, PFGE analysis in conjunction with distance matrix analysis served as a useful tool for delineating common S. typhi phage types of diverse origins from different geographical locales and separated in time.     

IS200 fingerprint of Salmonella enterica serotype Typhimurium human strains isolated in Sardinia.

A collection of Salmonella enterica serotype Typhimurium human strains isolated in Northern Sardinia (Italy) was examined for the insertion sequence IS200, phage type, antibiotic profile, ribotyping polymorphisms and plasmid profile. All clinical isolates studied contained from 4 to 10 copies of the IS200 element. IS200 permitted to discriminate Typhimurium strains and to identify five IS200 types, some of them circulating in Sardinia at least since 1900. Strains belonging to phage DT104 predominated and correlated with a specific IS200 pattern.     

Salmonellosis in Indonesia: phage type distribution of Salmonella typhi.

The distribution of phage types was studied among 577 strains of Salmonella typhi from Indonesia. Chemotype, colicinogeny, and tetrathionate reductase activity were also studied for most of these strains. The current phage type formula for Java was determined to be: A, D2, D6, E1a, E2, M1, and 46, but two other large groups of strains were also found, I + IV and degraded Vi+ strains. Significant differences in S. typhi strain distributions were noted between two localities on Java with respect to phage type and tetrathionate reductase activity. Comparisons were made with past phage typing studies in Jakarta as well as with more recent studies in other parts of south-east Asia. Phage types A, D1, D2, and E1 persisted at a rather steady level in Jakarta for 28 years. Evidence was found for epidemiological links to European and Asian areas. Antibiotic resistance among these Indonesian S. typhi strains was rare.     

Grouping of Salmonella enterica serotype Montevideo strains by ribotyping and IS200 profiling

One-hundred and twenty-one isolates of Salmonella enterica serotype Montevideo, representing different biotypes and incidents of infection detected in the UK between 1977 and 1995, were analysed by EcoRI ribotyping, PvuII ribotyping and IS200 fingerprinting. Among the isolates examined, 7 EcoRI ribotypes, 5 PvuII ribotypes and 55 IS200 profile types were recognized and 4 arbitrary groups defined. All 33 isolates of biotype 2d belonged to EcoRI/PvuII ribotype 1/1 and IS200 lineage A and comprised Group I. The other 88 isolates of biotype 10di and its variants were assigned to Groups II-IV. All 27 isolates in Group II were of EcoRI/PvuII ribotype 2/2 and IS200 lineage B. Among the 43 isolates in Group III, 42 of which were of EcoRI/PvuII ribotype 3/3, IS200 analysis identified 38 profiles in lineages C-I. Six EcoRI/PvuII ribotypes and 8 IS200 profiles, mostly in lineages C-E, were recognized among the 18 isolates in Group IV. The combined use of biotyping and ribotyping, and to some extent IS200 profiling, has enhanced our understanding of the clonal structure of serotype Montevideo and provides a basis for further study.     

Measles in Europe: an epidemiological assessment

Measles in Europe: an epidemiological assessment .
Muscat M. , Bang H. , Wohlfahrt J. , Glismann S. & Mølbak K. , for the EUVAC.NET Group . ( 2009 ) The Lancet , 373 , 383 – 389 .     

Suicide in Canada: an epidemiological assessment

Suicide rates in Canada rapidly increased during the 1960s and 1970s. More recent analysis of these trends indicates that in males suicide rates have stabilized and in females a notable decrease has been identified. The greatest changes in suicide rates have occurred among the youngest age groups (15 to 19), while little change has occurred in suicide mortality rates for males aged 50 years and over. The age-specific death rates in 1986 are uniformly distributed in males above age 20, while in females an inverted "U" curve is demonstrated with the peak at age 45-50. Males continue to have higher rates and the difference between males and females is expanding. A birth cohort analysis indicates that the contribution of the birth cohort to explaining suicide rates has diminished and been replaced by a more recent period effect. Suicide remains the second most important cause of death of persons between 15 and 34 years of age. Provincial variation is discussed through geographic variation, cause-specific rankings and potential years of life lost. In contrast to national trends, suicide mortality in Alberta, Quebec and New Brunswick continues to increase. An atlas is provided to display Canadian census divisions that exhibit elevated rates of suicide.     

Spread of Salmonella typhi in a maternity hospital.

An Asian patient with undiagnosed typhoid fever was admitted to a maternity hospital and delivered within 10 min. Salmonella typhi (phage type D5) was isolated from her blood and from the faeces of her baby. Another women in a different room of the labour suite at the same time acquired the same organism in her faeces; her brother was admitted to the Infectious Diseases Unit 5 weeks later with typhoid fever. Two babies, born over 60 h after the index case was delivered, became faecal excreters of the same strain and one of them also developed S. typhi osteitis of the hip. These two babies and their mothers were in the same ward as each other, but not that occupied by the infected mother and her baby. Nine other excreters in two of the families involved were identified. The index case and her baby were isolated immediately after delivery, and the relevant rooms in the labour suite were adequately disinfected. No evidence of undisinfected equipment used by the index case and the other infected patients was found, and no spread to staff was detected. The mode of spread remains unknown.     

Ethylene oxide: an assessment of the epidemiological evidence on carcinogenicity.

Mortality from cancer among workers exposed to ethylene oxide (EtO) has been studied in 10 distinct cohorts that include about 29,800 workers and 2540 deaths. This paper presents a review and meta-analysis of these studies, primarily for leukaemia, non-Hodgkin's lymphoma, stomach cancer, pancreatic cancer, and cancer of the brain and nervous system. The magnitude and consistency of the standardised mortality ratios (SMRs) were evaluated for the individual and combined studies, as well as trends by intensity or frequency of exposure, by duration of exposure, and by latency (time since first exposure). Exposures to other workplace chemicals were examined as possible confounder variables. Three small studies by Hogstedt initially suggested an association between EtO and leukaemia, but in seven subsequent studies the SMRs for leukaemia have been much lower. For the combined studies the SMR = 1.06 (95% confidence interval (95% CI) 0.73-1.48). There was a slight suggestion of a trend by duration of exposure (p = 0.19) and a suggested increase with longer latency (p = 0.07), but there was no overall trend in risk of leukaemia by intensity or frequency of exposure; nor did a cumulative exposure analysis in the largest study indicate a quantitative association. There was also an indication that in two studies with increased risks the workers had been exposed to other potential carcinogens. For non-Hodgkin's lymphoma there was a suggestive risk overall (SMR = 1.35, 95% CI 0.93-1.90). Breakdowns by exposure intensity or frequency, exposure duration, or latency did not indicate an association, but a positive trend by cumulative exposure (p = 0.05) was seen in the largest study. There was a suggested increase in the overall SMR for stomach cancer (SMR = 1.28, 95% CI 0.98-1.65 (CI 0.73-2.26 when heterogeneity among the risk estimates was taken into account)), but analyses by intensity or duration of exposure or cumulative exposure did not support a causal association for stomach cancer. The overall SMRs and exposure-response analyses did not indicate a risk from EtO for pancreatic cancer (SMR = 0.98), brain and nervous system cancer (SMR = 0.89), or total cancer (SMR = 0.94). Although the current data do not provide consistent and convincing evidence that EtO causes leukaemia or non-Hodgkin's lymphoma, the issues are not resolved and await further studies of exposed populations.     

Application of ribotyping and IS200 fingerprinting to distinguish the five Salmonella serotype O6,7:c:1,5 groups: Choleraesuis sensu stricto, Choleraesuis var. Kunzendorf, Choleraesuis var. Decatur, Paratyphi C, and Typhisuis.

Sixty-seven strains of the five described Salmonella serotypes having antigens 6,7:c:1,5, that is S. enterica serotype Choleraesuis sensu stricto, Choleraesuis var. Kunzendorf, Choleraesuis var. Decatur, Paratyphi C, and Typhisuis, were examined for 16S rrn profile ribotype, presence of IS200 and phenotypic characters, including rate of change of flagellar-antigen phase and nutritional character. Choleraesuis sensu stricto and its Kunzendorf variant had related but distinct ribotypes. Therefore, ribotyping appears to be a suitable method for differentiating Choleraesuis non-Kunzendorf from Choleraesuis var. Kunzendorf. Some strains of Paratyphi C had 16S profiles that resembled that of Choleraesuis non-Kunzendorf, while others resembled that of Choleraesuis var. Kunzendorf. The Typhisuis profiles were like those of Choleraesuis non-Kunzendorf, while the Choleraesuis var. Decatur profiles were unlike those of any of the other four groups. Furthermore, IS200 fingerprinting discriminated between Choleraesuis var. Decatur and the other strains with antigenic formula O6,7:c:1,5, and comparison of IS200 patterns showed a high degree of genetic divergence within Choleraesuis var. Decatur. Our findings show that ribotyping and IS200 fingerprinting, combined with classical microbiological methods, distinguish the groups Choleraesuis non-Kunzendorf, Choleraesuis var. Kunzendorf, Choleraesuis var. Decatur, Paratyphi C and Typhisuis.     

Molecular fingerprinting of multidrug-resistant Salmonella enterica serotype Typhi.

For epidemiologic investigations, the primary subdivision of Salmonella Typhi is vi-phage typing; 106 Vi-phage types are defined. For multidrug-resistant strains the most common types have been M1 (Pakistan) and E1 (India, Pakistan, Bangladesh, and the Arabian Gulf); a strain untypable with the Vi phages has been responsible for a major epidemic in Tajikistan. Most often, isolates from the Indian subcontinent have been resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, tetracyclines, and trimethoprim; but in the 1997 Tajikistan outbreak, the epidemic strain was also resistant to ciprofloxacin. For multidrug-resistant strains, subdivision within phage type can be achieved by plasmid profile typing and pulsed-field gel electrophoresis.     

我国伤寒沙门氏菌的分子流行病学特征Ⅰ．我国部分地区伤寒沙门氏菌的多位点酶电泳研究

通过聚丙烯酰胺凝胶电泳（ＰＡＧＥ）分析了我国部分伤寒高发省份在不同年代分离到的３３５株伤寒菌的七种染色体编码的多位点代谢酶。结果发现这七个酶位点均有多态性。其平均等位基因数为７．４（２～１９）；平均遗传多态度为０．４９８（０．１９８～０．８８３）。３３５株伤寒菌的七个酶位点电冰结果通过排序和数值分类可分为１４７个不同的电泳型（ＥＴｓ）．根据对ＥＴｓ进行聚类分析以及聚类时不相似系数曲线变化情况，把１４７个ＥＴｓ归属于２２个不同的亚克隆系，１２个克隆系，进一步的分析发现，不同地区、不同年代、不同来源的菌株有其规律性，１９８８年的江苏、浙江菌株大部来自同一克隆系；１９９０年的广西菌株和１９９０年的部分湖北菌株也为同一个克隆系菌株。不同年代分离的湖南和贵州菌株之间具有较近的亲缘性；而新疆菌株则有相对的独立性。同时结果还显示同一次伤寒爆发或流行中分离到的菌株均来自一个亚克隆系。