Independent Outbreaks Research Articles

Role of Curli and Cellulose Expression in Adherence ofEscherichia coliO157:H7 to Spinach Leaves

Shiga-toxigenic Escherichia coli O157:H7 outbreaks have been linked to consumption of fresh produce. It is generally recognized that bacterial attachment to vegetal matrices constitutes the first step in contamination of fresh produce. Cellular appendages, such as curli fibers, and cellulose, a constituent of extracellular matrix, have been suggested to be involved in E. coli attachment and persistence in fresh produce. A comparative evaluation was conducted on the ability of Shiga toxin-producing E. coli O157:H7 strains EDL933 and 86-24, linked to two independent foodborne disease outbreaks in humans, and their mutants deficient in curli and/or cellulose expression to colonize and to firmly attach to spinach leaf. Inoculated spinach leaves were incubated at 22°C, and at 0, 24, and 48 h after incubation loosely and strongly attached E. coli O157:H7 populations were determined. Curli-expressing E. coli O157:H7 strains developed stronger association with leaf surface, whereas curli-deficient mutants attached to spinach at significantly (p<0.01) lower numbers. Attachment of cellulose-impaired mutants to spinach leaves was not significantly different from that of curliated strains. The relative attachment strength of E. coli O157:H7 to spinach increased with incubation time for the curli-expressing strains. Laser scanning confocal microscopy (LSCM) analysis of inoculated leaves revealed that curli-expressing E. coli O157:H7 were surrounded by extracellular structures strongly immunostained with anti-curli antibodies. Production of cellulose was not required to develop strong attachment to spinach leaf. These results indicate that curli fibers are essential for strong attachment of E. coli O157:H7 to spinach whereas cellulose is dispensable.

Measles genotypes D4 and G3 reintroduced by multiple foci after 15 years without measles virus circulation, Gipuzkoa, the Basque Country, Spain, March to June 2011

During a three-month period in spring 2011, 23 cases of measles occurred in seven independent outbreaks in a region in Spain with around 700,000 inhabitants, where the disease had been eliminated since 1997. High vaccination coverage and rapid diagnosis allowed implementation of containment measures and this prevented spread of the disease. Except for the first outbreak which affected 10 cases, each of the other six outbreaks caused a maximum of three secondary cases.

Typing of O26 enterohaemorrhagic and enteropathogenic Escherichia coli isolated from humans and cattle with IS621 multiplex PCR-based fingerprinting

This study evaluated a typing method of O26:H11 enterohaemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC) based on the variation in genomic location and copy numbers of IS621. Two multiplex PCRs, targeting either the left (5') or right (3') IS/chromosome junction of 12 IS621 insertion sites and one PCR specific of another truncated copy, were developed. Thirty-eight amplification profiles were observed amongst a collection of 69 human and bovine O26:H11 EHEC and EPEC. Seventy-one per cent of the 45 EHEC and EPEC with identical IS621 fingerprints within groups of two, three or four isolates had >85% pulsed field gel electrophoresis (PFGE) profile similarity, including four groups of epidemiologically related EHEC or EPEC, while most of the groups had <85% similarity between each others. Epidemiologically related EHEC from each of three independent outbreaks in Japan and Belgium also exhibited identical IS621 fingerprints and PFGE profiles. The IS621 fingerprinting and the PFGE are complementary typing assays of EHEC and EPEC; though, the former is less discriminatory. The IS621 printing method represents a rapid (24 h) first-line surveillance and typing assay, to compare and trace back O26:H11 EHEC and EPEC during surveys in farms, multiple human cases and outbreaks.

Salmonella infections in food workers identified through routine Public Health Surveillance in Minnesota: impact on outbreak recognition.

The frequency of Salmonella-infected food workers identified through routine surveillance from 1997 to 2004 in Minnesota was determined in order to evaluate the impact of surveillance on the detection of outbreaks in restaurants and to quantify the duration of Salmonella shedding in stool. Of 4,976 culture-confirmed Salmonella cases reported to the Minnesota Department of Health, 110 (2.2%) were identified as food workers; this was less than one-half the number expected based on the incidence of Salmonella in the general population. Twenty food workers (18%) were associated with outbreaks. Twelve were involved in nine independent outbreaks at the restaurants where they worked. The identification of the index food worker in six of these outbreaks was critical to the initiation of outbreak investigations that revealed much larger problems. Among food workers who submitted specimens until at least one negative result was obtained (n = 69), the median duration of shedding was 22 days (range, 1 to 359 days). Among the four most common serotypes (Enteritidis, Typhimurium, Heidelberg, and Newport) the median duration of shedding was significantly longer for Salmonella Newport (80 days; P = 0.02) and for Salmonella Enteritidis (32 days; P = 0.04) than for Salmonella Heidelberg (8 days). Food workers should be considered an important source of Salmonella transmission, and those identified through surveillance should raise a high index of suspicion of a possible outbreak at their place of work. Food service managers need to be alert to Salmonella-like illnesses among food workers to facilitate prevention and control efforts, including exclusion of infected food workers or restriction of their duties.

Outbreak of acute hemorrhagic conjunctivitis in Yunnan, People's Republic of China, 2007

An outbreak of acute hemorrhagic conjunctivitis (AHC) occurred in Yunnan Province, China between August and September in 2007. A total of 3,597 cases were officially reported and the incidence rate reached 1390.94/100,000. Descriptive epidemiological analysis of the outbreak was conducted using the data from National Disease Supervision Information Management System (NDSIMS). To determine the causative agent for this outbreak and to analyze their genetic features, 30 conjunctival swabs and 19 paired serum specimens of acute and convalescent phase were collected from 30 patients with AHC, and viral isolation, molecular typing, antibody assay and phylogenetic analysis were performed.11 virus strains were isolated from 30 conjunctival swabs. Amplification and sequencing of the VP4 region of these strains identified that coxsackievirus A24 variant (CA24v) could be the causative agent of the AHC outbreak and this was further confirmed by subsequent virus neutralizing antibody test on 19 paired serum specimens. Phylogenetic analysis based on the 3C regions showed that the Yunnan CA24v strains belonged to Group 3 and clustered with the strains isolated from worldwide AHC outbreaks after 2002. Phylogenetic analysis based on the partial VP1 revealed that the Yunnan strains differed from the strains isolated from AHC outbreak in Guangdong of China in 2007 with 2.8 - 3.0% nucleotide divergence, suggesting that two different lineages of CA24v caused the independent AHC outbreaks in Yunnan and Guangdong, respectively.

Hepatitis A in the European Union: responding to challenges related to new epidemiological patterns

In the European Union (EU), the overall incidence of hepatitis A has decreased over the last 10 years from 15.1 per 100,000 population in 1996 to 3.9 per 100,000 in 2006. However, reduction in circulation of HAV leads to decreased acquisition of immunity and, in the absence of universal vaccination, an accumulation of susceptible individuals. The impact of increasing susceptibility of the general population on the risk for outbreaks is clearly illustrated in independent outbreaks in Czech Republic, Latvia and Slovakia in 2008, described in three of the articles published in this week’s issue of Eurosurveillance.

Role of Human Bocavirus infections in outbreaks of gastroenteritis

Background Human Bocavirus (HBoV) is considered to be responsible for lower respiratory tract infections in small children. Recent publications also reported the detection of HBoV in stool samples of gastroenteritis patients. Therefore HBoV might be associated with gastroenteritis cases. Objectives To investigate the prevalence and the causative role of HBoV in gastroenteritis outbreaks in day care facilities for children. Study design We examined 307 stool samples using a real time PCR protocol for HBoV load. Samples were collected from 48 independent outbreaks of gastroenteritis in day care facilities. Results HBoV was detected in 14/307 stool samples (4.6%). HBoV load in the samples was low and the 14 HBoV positive samples were distributed among 13 different outbreaks. Coinfections with Norovirus in single samples were frequent (57.1%), but no gastroenteritis outbreak could be associated with HBoV infection or coinfection. Conclusions This study indicates that HBoV is not a causative agent for gastroenteritis outbreaks.

High-resolution genotyping of Pseudomonas aeruginosa strains linked to acute post cataract surgery endophthalmitis outbreaks in India

BackgroundInvestigation of two independent outbreaks of post cataract surgery endophthalmitis identified the reservoir of epidemic strains of P. aeruginosa.MethodsPatient isolates cultured from vitreous fluid of all the nine cases and from the peripheral devices of phacoemulsification machine were subjected to high-resolution Fluorescent Amplified Fragment Length Polymorphism (FAFLP) analysis.ResultsFAFLP based genotyping of the isolates confirmed nosocomial transmission. Although biochemical characterization and antibiotic susceptibility profiles grouped all the isolates together, FAFLP based genotyping revealed that, all the outbreak isolates were derived from 2 different strains, with independent origins. One group of isolates was traced to phacoprobe and the second one to the internal tubing system of the phacoemulsification machine used in cataract surgery. In silico analysis indicated possible evolution in both the clusters of P. aeruginosa isolates due to genetic polymorphisms. The polymorphisms were mapped to gene products (cell envelope, outer membrane proteins) possibly having significant role in pathogenesis.ConclusionThe present study is probably the first one to apply FAFLP typing successfully to investigate outbreaks of postoperative endophthalmitis (POE) in an ophthalmic setting, which was able to identify the source, and helped to make rational decisions on sterilization procedures that halted more cases of infection in these hospitals.

Extended Spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Outbreaks During a Third Generation Cephalosporin Restriction Policy

In spite of the adoption of third generation cephalosporin restriction policies, two independent outbreaks by Extended Spectrum Beta-Lactamase (ESBL)-producing Klebsiella pneumoniaeoccurred in two different wards (Neonatal Intensive Care Unit, NICU and Neurosurgery) of a teaching hospital in Rome, Italy. In the former 19 infected neonates were reported, whereas in the latter there were 10 infected patients. In both wards no differences were observed in the mortality rates in periods of outbreak and those with no outbreak. Molecular typing on a total of 19 isolated strains was carried out and restriction patterns were compared. The PFGE showed that nine isolates responsible for infection in the NICU were all included in three closely related clusters. In Neurosurgery nine strains out of ten were strictly related and part of an outbreak occurring between August-December 2003, while one isolate was temporarily (February 2003) and genetically (seven band differences) unrelated to the outbreak strains. When ESBL producing K. pneumoniae clusters from the two wards (NICU vs Neurosurgery) were compared, they appeared to be completely different both for their genotype pattern and plasmid type or presence, thus demonstrating cross transmission by two different genotypes.

Multifocal detection of multidrug-resistant Pseudomonas aeruginosa producing the PER-1 extended-spectrum beta-lactamase in Northern Italy.

Forty-four nonreplicate clinical isolates of Pseudomonas aeruginosa that were resistant to extended-spectrum cephalosporins (ceftazidime and cefepime) and aztreonam, that putatively produced an acquired extended- spectrum beta-lactamase (ESBL), according to the results of a double-disk synergy test, and that had been involved in nosocomial outbreaks were obtained from six different hospitals in northern Italy and screened for the presence of bla(PER) ESBL determinants. Twenty isolates, associated with nine independent outbreaks that occurred in five hospitals in the Milan area and its surroundings during 1995-2000, were found to carry an acquired bla(PER-1) gene. PER-1 producers representative of the nine outbreaks exhibited a multidrug resistance (MDR) phenotype, including resistance to extended-spectrum cephalosporins, aztreonam, meropenem, aminoglycosides, and in most cases, imipenem and ciprofloxacin. An analysis of macrorestriction profiles of their genomic DNAs by pulsed-field gel electrophoresis revealed an overall clonal diversity of the PER-1 producers, although interhospital clonal spread was also observed. The bla(PER-1) gene was not transferable and appeared to be chromosomally located. An analysis of the EcoRI and EcoRV restriction fragment length polymorphisms of the bla(PER-1) locus revealed identical patterns for all isolates, and the characterization of a 1.9-kb region containing bla(PER-1) revealed a conserved structure in representatives of the various clonal lineages. The present findings indicate that MDR P. aeruginosa clones producing the PER-1 ESBL are endemic to this area of northern Italy, where they have been circulating since the mid-1990s and have been associated with several nosocomial outbreaks.

Retrospective genetic analysis of SAT-1 type foot-and-mouth disease outbreaks in West Africa (1975–1981)

The complete 1D genome region encoding the immunogenic and phylogenetically informative VP1 gene was genetically characterized for 23 South African Territories (SAT)-1 viruses causing foot-and-mouth (FMD) disease outbreaks in the West African region between 1975 and 1981. The results indicate that two independent outbreaks occurred, the first involved two West African countries, namely Niger and Nigeria, whilst the second affected Nigeria alone. In the former epizootic, virus circulation spanned a period of 2 years, whilst in the latter virus was recovered from the field over a 3 year period. Comparison of the West African viruses with SAT-1 viruses from other regions on the continent revealed that the two West African lineages identified in this study are regionally distinct. Furthermore, variation in VP1 gene length was identified in SAT-1 viruses for the first time, further emphasizing the uniqueness of these pathogens in West Africa. This first retrospective analysis in which the molecular epidemiology of SAT-1 viruses in West Africa is reported, provides a useful measure of the regional variation of these viruses and is an essential first step in the establishment of a West African sequence database that will be a useful reference for future outbreak eventualities.

Molecular Epidemiology of a Geographically Localised Salmonella Typhimurium DT104 Outbreak in Danish Cattle and Pigs

Salmonella enterica serovar Typhimurium phage type DT 104 is a zoonotic bacteria. 25 % of the S. Typhimurium cases in humans in Denmark are caused by DT104 and food of animal origin is thought to be the main source of these infections. DT 104 is found in many different kinds of animal species including cattle. Molecular typing methods have proven to be a strong tool in epidemiological investigations. In the present investigation pulse field gel electrophoresis (PFGE) and plasmid profiling have been the methods used to investigate a geographically localised (15 km in diameter) outbreak among cattle and pigs. 88 isolates of DT 104 samples from 15 different cattle and pig herds collected during a period of three years was characterised by plasmid profile analysis and pulsed field gel electrophoresis (PFGE) using the digestion enzymes XbaI and BlnI. The samples originated mainly from cattle but include also swine, sheep, horse, hen, dog, cat and rat. Eighty-six of the isolates were multiresistant and two were fully susceptible to antimicrobial agents. Four different PFGE profiles were identified. 84 of the isolates were the same PFGE type. The two susceptible isolates had a different PFGE profile. Four different plasmidprofiles were found. One plasmid profile dominated in 13 of the 15 herds and another profile dominated in the remaining two herds. The plasmid profile has demonstrated high in-vivo stability in the herds of the region. An investigation of the in-vitro stability of the plasmids showed that the plasmids were very stable with no loss over time. This may indicate that the two different plasmid profiles in two and thirteen herds, respectively, reflect two independent outbreaks with different sources of infection The plasmid profile found in the 13 herds has not been found previously in cattle herds in Denmark though it has been found in isolates from humans, swine and food. A majority of the herds are connected either through neighbourhood or ownership or because they share agricultural machines. In most cases, a certain route of transmission between cattle farms in the outbreak region was suspected, however, in five cases, no obvious cause of introduction at herd level was found. The results combined with the epidemiological data available indicated that risk factors of introduction of DT104 is being neighbour to a DT104 infected farm, sharing agricultural machines or manure tank with an infected farm.

Abomasitis associated with multiple antibiotic resistant Salmonella enterica serotype Typhimurium phagetype DT104

Salmonella enterica serotype Typhimurium phagetype DT104 is a multiple antibiotic resistant pathogen that has been purported to be more pathogenic than other Salmonella. In this study, we evaluated the possibility that DT104 is the causative agent of veal calf abomasitis observed in four independent outbreaks of salmonellosis. This study was undertaken to determine if the outbreaks might be due to hypervirulent S. enterica serotype Typhimurium phagetype DT104 (DT104) since Salmonella does not usually cause abomasitis. Tissues and fluids from these calves were subjected to bacteriologic culture. Pure Salmonella cultures were then used in bovine challenge experiments. DT104 was identified as the causative agent of abomasitis in calves. Thus, abomasitis is a potential indicator of infection with multiple antibiotic resistant DT104 and adds credence to the apparent hypervirulence of this pathogen.

Changing prevalence of hepatitis C virus genotypes: Molecular epidemiology and clinical implications in the hepatitis C virus hyperendemic areas and a tertiary referral center in Taiwan

To determine the hepatitis C virus (HCV) genotype distribution in Taiwan and to clarify the relationship between genotype and the pathogenesis of HCV infection, 1,164 subjects positive for serum HCV antibodies and HCV RNA from three HCV hyperendemic areas (Masago, Tzukuan, and Taoyuan) and a tertiary referral center in Taiwan were studied during 1995–1997. HCV genotypes and viral loads were determined using Okamoto's method and branched DNA assay, respectively. Genotype 1b was the most prevalent in Tzukuan (61.9%), Taoyuan (76.9%), and the referral center (47.0%). By contrast, genotype 2a was the major HCV type in Masago (63.5%). Prevalence of genotype 1b positively and that of genotype 2a negatively correlated to age, regardless of study populations (P < 0.01). Based on multivariate analysis, the significant factors associated with the presence of cirrhosis, with or without hepatocellular carcinoma, in chronic hepatitis C patients were genotype 1b and age. In conclusion, these results underline that independent HCV outbreaks continue in HCV hyperendemic areas in Taiwan, concomitant with a changing relative prevalence of HCV genotypes in relation to age. Both the correlation of genotype 1b with age (cohort effect) and intrinsic properties of HCV genotypes are probably responsible for the association between genotype and the pathogenesis of HCV infection. J. Med. Virol. 65:58–65, 2001. © 2001 Wiley-Liss, Inc.

Changing prevalence of hepatitis C virus genotypes: Molecular epidemiology and clinical implications in the hepatitis C virus hyperendemic areas and a tertiary referral center in Taiwan

To determine the hepatitis C virus (HCV) genotype distribution in Taiwan and to clarify the relationship between genotype and the pathogenesis of HCV infection, 1,164 subjects positive for serum HCV antibodies and HCV RNA from three HCV hyperendemic areas (Masago, Tzukuan, and Taoyuan) and a tertiary referral center in Taiwan were studied during 1995-1997. HCV genotypes and viral loads were determined using Okamoto's method and branched DNA assay, respectively. Genotype 1b was the most prevalent in Tzukuan (61.9%), Taoyuan (76.9%), and the referral center (47.0%). By contrast, genotype 2a was the major HCV type in Masago (63.5%). Prevalence of genotype 1b positively and that of genotype 2a negatively correlated to age, regardless of study populations (P < 0.01). Based on multivariate analysis, the significant factors associated with the presence of cirrhosis, with or without hepatocellular carcinoma, in chronic hepatitis C patients were genotype 1b and age. In conclusion, these results underline that independent HCV outbreaks continue in HCV hyperendemic areas in Taiwan, concomitant with a changing relative prevalence of HCV genotypes in relation to age. Both the correlation of genotype 1b with age (cohort effect) and intrinsic properties of HCV genotypes are probably responsible for the association between genotype and the pathogenesis of HCV infection.

Detection of DNA restriction fragment polymorphisms in Streptococcus equi

Large-restriction-fragment (LRF) polymorphisms in Streptococcus equi (S equi subspecies equi) were studied by pulsed-field gel electrophoresis. Five or six chromosomal fragments of between 194 and 915 kb were separated by...

Epidemic Typhoid in Vietnam: Molecular Typing of Multiple-Antibiotic-Resistant Salmonella enterica Serotype Typhi from Four Outbreaks

Multidrug-resistant Salmonella enterica serotype Typhi isolates from four outbreaks of typhoid fever in southern Vietnam between 1993 and 1997 were compared. Pulsed-field gel electrophoresis, bacteriophage and plasmid typing, and antibiotic susceptibilities showed that independent outbreaks of multidrug-resistant typhoid fever in southern Vietnam are caused by single bacterial strains. However, different outbreaks do not derive from the clonal expansion of a single multidrug-resistant serotype Typhi strain.

Discrimination of multidrug-resistant Mycobacterium tuberculosis IS6110 fingerprint subclusters by rpoB gene mutation analysis.

The rpoB gene mutations in a 69-bp region of the gene, resulting in resistance to rifampin, were used to discriminate between Mycobacterium tuberculosis IS6110 fingerprint subclusters. These subclusters exhibited identical IS6110 fragments or had one or two additional fragments. In the two major subclusters all the analyzed strains have the same variant rpoB allele but are different from each other, suggesting the occurrence of independent outbreaks.

Molecular genotyping of Staphylococcus aureus strains: comparison of repetitive element sequence-based PCR with various typing methods and isolation of a novel epidemicity marker.

Repetitive sequence-based (Rep)-PCR genotyping as described here is based on the presence of homologues of Mycoplasma pneumoniae repeat-like elements in Staphylococcus. In this study we comparatively evaluated the usefulness of rep-PCR typing with two sets of well-defined collections of Staphylococcus aureus strains. Rep-PCR analysis of the first collection of S. aureus strains (n = 59) and one Staphylococcus intermedius strain showed 14 different rep-PCR patterns, with each pattern harboring 6 to 15 DNA fragments. The discriminatory power of rep-PCR typing compared well to those of arbitrarily primed PCR (average of 20 types) and pulsed-field gel electrophoresis (11 types). S. aureus strain collection I comprised four outbreak-related groups of isolates. The isolates in only one group were found to have identical rep-PCR profiles. However, in an analysis of isolates from three additional independent local outbreaks (n for outbreaks 1 and 2 = 5, n for outbreak 3 = 12), identical rep-PCR types were found among strains isolated during each outbreak. Therefore, we conclude that rep-PCR genotyping may be an easy and fast method for monitoring of the epidemiology of nosocomial Staphylococcus infections. Rep-PCR analysis of strain collection II, which consisted of epidemic and nonepidemic methicillin-resistant S. aureus (MRSA) strains, revealed that a cluster of similar rep-PCR profiles was found among MRSA isolates which were more frequently isolated and which were most often associated with outbreaks.

Geographic distribution and epidemiology of peste des petits ruminants viruses

Peste des petits ruminants (PPR) is an important viral disease of goats and sheep prevalent in West Africa and the Middle East. In recent years, PPR has emerged in India, first in the South India and later in North India. To study the genetic relationships between viruses of distinct geographical origin we have sequenced a 322 nucleotide cDNA fragment of the fusion protein gene generated using reverse transcription followed by polymerase chain reaction (PCR) amplification. Viruses from nineteen independent PPR outbreaks were compared; these included the prototype African strain from Senegal and viruses from disease outbreaks which have occurred at different times and locations across Africa, Arabia, the Near East and the Indian subcontinent. Four separate lineages of the virus were identified and the virus isolates from Asia over the past 2 years were all of one lineage which had not previously been identified in Africa or Asia.