Prevalence and genetic characterization of pertactin-deficient Bordetella pertussis in Japan

The adhesin pertactin (Prn) is one of the major virulence factors of Bordetella pertussis, the etiological agent of whooping cough. However, a significant prevalence of Prn-deficient (Prn(-)) B. pertussis was observed in Japan. The Prn(-) isolate was first discovered in 1997, and 33 (27%) Prn(-) isolates were identified among 121 B. pertussis isolates collected from 1990 to 2009. Sequence analysis revealed that all the Prn(-) isolates harbor exclusively the vaccine-type prn1 allele and that loss of Prn expression is caused by 2 different mutations: an 84-bp deletion of the prn signal sequence (prn1ΔSS, n = 24) and an IS481 insertion in prn1 (prn1::IS481, n = 9). The frequency of Prn(-) isolates, notably those harboring prn1ΔSS, significantly increased since the early 2000s, and Prn(-) isolates were subsequently found nationwide. Multilocus variable-number tandem repeat analysis (MLVA) revealed that 24 (73%) of 33 Prn(-) isolates belong to MLVA-186, and 6 and 3 Prn(-) isolates belong to MLVA-194 and MLVA-226, respectively. The 3 MLVA types are phylogenetically closely related, suggesting that the 2 Prn(-) clinical strains (harboring prn1ΔSS and prn1::IS481) have clonally expanded in Japan. Growth competition assays in vitro also demonstrated that Prn(-) isolates have a higher growth potential than the Prn(+) back-mutants from which they were derived. Our observations suggested that human host factors (genetic factors and immune status) that select for Prn(-) strains have arisen and that Prn expression is not essential for fitness under these conditions.     

中国猪种布鲁氏菌分子流行病学特征分析

【目的】调查猪种布鲁氏菌的基因多态性和分子流行病学特征。【方法】用经典分型方法对菌株的生物型进行鉴定,分析菌株的地理分布特点;用MLVA-16分型方法对60株猪种布鲁氏菌进行基因分型,采用在线软件评估分型方法的分辨率和位点的多态性,用BioNumerics 5.0软件进行聚类分析。【结果】我国流行的猪种布鲁氏菌主要是猪种生物1型(33株)、2型(3株)和3型菌(24株);分布范围较广,包括广东、广西、内蒙古、北京、吉林、宁夏和西藏等地。MLVA-16分型方法对猪种布鲁氏菌具有极高的分辨力,多态性指数为0.992;Panel1、MLVA-11和Panel 2B均具有较高的分辨率,多态性指数分别为0.884、0.916和0.979。60株猪种布鲁氏菌聚为6大类52个基因型,5个共享基因型(GT24,GT25,GT26,GT28,GT29)包括13株布鲁氏菌,各基因型菌株间有潜在的流行病学关联,可能是分别来自相同传染源的暴发流行;另47株布鲁氏菌呈现独特的基因型,表明菌株来自无流行病学关联的零星散发病例。猪种布鲁氏菌的最小生成树表明我国菌株分别与美国、法国和波兰的菌株有完全相同的MLVA-15基因型。【结论】中国猪种布鲁氏菌有较高的遗传多态性,并与美国、法国和阿根廷的菌株有较高的遗传相似性。我国猪种布病以零星散发为主。     

Verotoxin-producing Escherichia coli in sheep grazing an irrigated pasture or arid rangeland forages

Worldwide, verotoxin-producing Escherichia coli (VTEC) have been recognized as the cause of many sporadic cases or major outbreaks of human illnesses involving consumption of contaminated meat, especially beef. Although sheep products have not been linked to reported human illnesses, their role as a food safety risk factor should not be ignored. The objective of this study was to assess VTEC prevalence in two groups of ewes (20 each) grazing an irrigated pasture or arid range in a western United States environment (Nevada) over 1 year (summer of 1999 to summer of 2000). A random sample (n = 504) of potential VTEC isolates were tested for verotoxicity and were screened for the presence (polymerase chain reaction [PCR]) and expression (VTEC-reversed passive latex agglutination assay) of the toxin genes (i.e., VT1 and VT2). Forty-one VTEC isolates (16 having only the VT1 gene and 25 having both VT1 And VT2 genes) were detected in both groups of ewes. Except for seven isolates, the genotype and phenotype data matched. All the isolates (nonmotile [H-]) were non-O157:H7 VTEC (i.e., O91:H- [n = 25], O128:H- [n = 9], and untypeable ones [n = 7]). More infected ewes (nine versus three) and different VTEC strains were found in the irrigated pasture than in the arid range. Because our ewes were shedding two VTEC serotypes known to cause human illnesses, it is beneficial to identify VTEC-positive sheep before slaughter as an initial control point before entering the food chain.     

Mechanisms of resistance to cephalosporin and emergence of O25b-ST131 clone harboring CTX-M-27 β-lactamase in extraintestinal pathogenic Escherichia coli from dogs and cats in Japan

Thirty-three cefazolin-resistant extraintestinal pathogenic Escherichia coli strains from companion animals were screened for bla(CMY-1) , bla(CMY-2) , bla(SHV) , bla(TEM) , and bla(CTX-M) genes. Extended-spectrum β-lactamase-producing strains were further characterized by O serotyping and multilocus sequence typing. It was found that 20 and 17 isolates harbored TEM-1 and CMY-2 β-lactamases, respectively, and 13 isolates harbored both β-lactamases. One isolate harbored DHA-1 β-lactamase. Eleven isolates were found to possess CTX-M β-lactamases (CTX-M-27 [n= 6], CTX-M-14 [n= 3], CTX-M-15 [n= 1], and CTX-M-55 [n= 1]). Of 11 CTX-M-positive strains, four strains were O25b-ST131 clones harboring CTX-M-27, and the remaining seven strains belonged to O6-ST127, ONT-ST354, O159-ST539, O1-ST648, O8-ST1642, O25b-ST2042, and ONT-ST2178.     

Characterization of <Emphasis Type="Italic">Aeromonas</Emphasis> Virulence Using an Immunocompromised Mouse Model

An immunocompromised mouse model was used to characterize Aeromonas strains for their ability to cause opportunistic, extraintestinal infections. A total of 34 isolates of Aeromonas (A. hydrophila [n = 12]), A. veronii biotype sobria [n = 7], A. caviae [n = 4], A. enchelia [n = 4], A. allosaccharophila [n = 2], A. salmonicida (n = 4), and A. bestiarum [n = 1]) were introduced by intraperitoneal injection into immunocompetent or chemically compromised (using cyclophosphamide) mice. The ability of each isolate to persist in the liver and spleen tissue was monitored at 24 hours after exposure. A majority of A. hydrophila and A veronii v. sobria strains, but none of the isolates of other Aeromonas species, were capable of persistent colonization (<300 cells/mg spleen and liver tissue at 24 hours). The presence or absence of several putative virulence factors (cytotoxicity to HEp-2, lipase activity, elastase activity, and hemolysis) were determined for each isolate using in vitro tests. There were no correlations between the presence or absence of biochemical test results for putative virulence factors and persistence of the isolate in spleen and liver tissue at 24 hours.     

Characterization of “Candidatus Liberibacter Asiaticus” Populations by Double-Locus Analyses

“Candidatus Liberibacter asiaticus” (CaLas) is associated with citrus Huanglongbing (HLB, yellow shoot disease), which is highly destructive to world citrus production. Understanding the relationships of CaLas isolates from different geographical regions is important for HLB research and development of disease management strategies. In this study, 301 CaLas isolates [85 Brazil, 132 China, and 84 U.S. (83 Florida and 1 California)] were collected, and genomic variations among them were evaluated based on the analyses of two genomic loci: trn1, characteristic of variable tandem repeat numbers (TRNs), and snp1, characteristic of single nucleotide polymorphisms (SNPs). Locus trn1 revealed the homogeneity of all Brazilian isolates, and locus snp1 revealed the homogeneity of most Florida isolates. When the two loci were analyzed simultaneously, i.e., double-locus (DL) analyses, CaLas isolates were clustered mostly according to geographical origins. DL genotype 1 included 97 % of the Chinese isolates, DL genotype 2 included all Brazilian isolates, and DL genotype 3 included 93 % of the U.S. isolates. DL analyses successfully revealed inter-continental overlapping or movement pattern of CaLas isolates. The isolate recently found in California belonged to Asiatic DL genotype 1.     

Genotype and mating type analysis of Cryptococcus neoformans and Cryptococcus gattii isolates from China that mainly originated from non-HIV-infected patients

Cryptococcosis has been reported to be mostly associated with non-HIV-related patients in China. However, little is known about the molecular characteristics of clinical isolates from the Cryptococcus neoformans species complex in this country. In this study, 115 clinical isolates were included. Molecular type VNI was the most representative ( n =103), followed by VGI ( n =8), VNIII ( n =2), VNIV ( n =1), and VGII ( n =1). With the exception of a serotype D mating type a isolate, all possessed the MAT α locus. Multilocus sequence typing (MLST) revealed that most Cryptococcus gattii isolates from China shared identical MLST profiles with the most common MLST genotype reported in the VGI group, and the only one VGII isolate resembled the Vancouver Island outbreak minor genotype. The C. gattii strains involved in this study were successfully grouped according to their molecular type and mating types by PCR-restriction fragment length polymorphism (RFLP) analysis of the GEF1 gene. Our results suggest that (1) in China, cryptococcosis is mostly caused by C. neoformans var. grubii (molecular type VNI), and mating type α; (2) The most common causative agents of C. gattii infection in China are closely related to a widely distributed MLST genotype; and (3) The PCR-RFLP analysis of the GEF1 gene has the potential to identify the molecular and mating types of C. gattii simultaneously.     

MLVA subtyping of genovar E Chlamydia trachomatis individualizes the Swedish variant and anorectal isolates from men who have sex with men

This study describes a new multilocus variable number tandem-repeat (VNTR) analysis (MLVA) typing system for the discrimination of Chlamydia trachomatis genovar D to K isolates or specimens. We focused our MLVA scheme on genovar E which predominates in most populations worldwide. This system does not require culture and therefore can be performed directly on DNA extracted from positive clinical specimens. Our method was based on GeneScan analysis of five VNTR loci labelled with fluorescent dyes by multiplex PCR and capillary electrophoresis. This MLVA, called MLVA-5, was applied to a collection of 220 genovar E and 94 non-E genovar C. trachomatis isolates and specimens obtained from 251 patients and resulted in 38 MLVA-5 types. The genetic stability of the MLVA-5 scheme was assessed for results obtained both in vitro by serial passage culturing and in vivo using concomitant and sequential isolates and specimens. All anorectal genovar E isolates from men who have sex with men exhibited the same MLVA-5 type, suggesting clonal spread. In the same way, we confirmed the clonal origin of the Swedish new variant of C. trachomatis. The MLVA-5 assay was compared to three other molecular typing methods, ompA gene sequencing, multilocus sequence typing (MLST) and a previous MLVA method called MLVA-3, on 43 genovar E isolates. The discriminatory index was 0.913 for MLVA-5, 0.860 for MLST and 0.622 for MLVA-3. Among all of these genotyping methods, MLVA-5 displayed the highest discriminatory power and does not require a time-consuming sequencing step. The results indicate that MLVA-5 enables high-resolution molecular epidemiological characterisation of C. trachomatis genovars D to K infections directly from specimens.     

Whole Genome-Sequencing and Phylogenetic Analysis of a Historical Collection of Bacillus anthracis Strains from Danish Cattle

Bacillus anthracis, the causative agent of anthrax, is known as one of the most genetically monomorphic species. Canonical single-nucleotide polymorphism (SNP) typing and whole-genome sequencing were used to investigate the molecular diversity of eleven B. anthracis strains isolated from cattle in Denmark between 1935 and 1988. Danish strains were assigned into five canSNP groups or lineages, i.e. A.Br.001/002 (n = 4), A.Br.Ames (n = 2), A.Br.008/011 (n = 2), A.Br.005/006 (n = 2) and A.Br.Aust94 (n = 1). The match with the A.Br.Ames lineage is of particular interest as the occurrence of such lineage in Europe is demonstrated for the first time, filling an historical gap within the phylogeography of the lineage. Comparative genome analyses of these strains with 41 isolates from other parts of the world revealed that the two Danish A.Br.008/011 strains were related to the heroin-associated strains responsible for outbreaks of injection anthrax in drug users in Europe. Eight novel diagnostic SNPs that specifically discriminate the different sub-groups of Danish strains were identified and developed into PCR-based genotyping assays.     

A new species of leopard frog (Anura: Ranidae) from the urban northeastern US

Past confusion about leopard frog (genus Rana) species composition in the Tri-State area of the US that includes New York (NY), New Jersey (NJ), and Connecticut (CT) has hindered conservation and management efforts, especially where populations are declining or imperiled. We use nuclear and mitochondrial genetic data to clarify the identification and distribution of leopard frog species in this region. We focus on four problematic frog populations of uncertain species affiliation in northern NJ, southeastern mainland NY, and Staten Island to test the following hypotheses: (1) they are conspecific with Rana sphenocephala or R. pipiens, (2) they are hybrids between R. sphenocephala and R. pipiens, or (3) they represent one or more previously undescribed cryptic taxa. Bayesian phylogenetic and cluster analyses revealed that the four unknown populations collectively form a novel genetic lineage, which represents a previously undescribed cryptic leopard frog species, Rana sp. nov. Statistical support for R. sp. nov. was strong in both the Bayesian (pp=1.0) and maximum-likelihood (bootstrap=99) phylogenetic analyses as well as the Structure cluster analyses. While our data support recognition of R. sp. nov. as a novel species, we recommend further study including fine-scaled sampling and ecological, behavioral, call, and morphological analyses before it is formally described.     

Molecular phylogenetics and diagnosis of soil and clinical isolates of Halicephalobus gingivalis (Nematoda: Cephalobina: Panagrolaimoidea), an opportunistic pathogen of horses

Phylogenetic relationships among six isolates of Halicephalobus gingivalis (Stefanski, 1954), a species with pathogenic potential in horses and humans, were evaluated using DNA sequences from the nuclear large-subunit ribosomal RNA (LSU rDNA) gene. Sequences from nematodes obtained from in vitro cultures (soil or clinical sources), or isolated from infected horse tissues, were compared. Gene sequences from a fatal equine clinical case from southern California and a free-living isolate recovered from southern California soil showed no fixed differences. Sequences from isolates representing two fatal equine cases from North America, one from Ontario, Canada and another from Tennessee also showed no fixed differences. In contrast, two equine cases from Tennessee had 18 fixed differences for this LSU region, the greatest observed among isolates from horses. Phylogenetic analysis of six Halicephalobus sequences and four outgroup taxa by maximum parsimony yielded one tree with five well-supported clades. This phylogeny did not group isolates of Halicephalobus strictly by region of geographic isolation or source of sample, and depicted one clinical and one soil isolate as sister taxa. These results confirm that free-living environmental isolates are potential sources of infection for horses. The phylogeny also reveals that diverse isolates can cause infections in horses within a relatively limited geographic region, and conversely that genetically similar sister taxa can be recovered from geographically distant localities. PCR primers that selectively amplify Halicephalobus DNA were designed and tested based on comparison of closely related nematodes as inferred from phylogenetic analysis.     

Investigation of spore surface antigens in the genus Bacillus by the use of polyclonal antibodies in immunofluorescence tests

Fluorescein-conjugated rabbit antibodies to formalized spores of Bacillus anthracis were tested against strains of B. anthracis and other Bacillus species in a subjective immunofluorescence test. The lack of reaction of B. anthracis Vollum spores with conjugated antibody raised against B. anthracis Sterne spores indicated that spores of the Vollum strain lacked a major surface antigen present in most of the other anthrax strains tested, including the non-encapsulated strains Sterne and the Soviet ST1, variants cured of the pX01 plasmid that codes for the toxin, and several virulent strains. Four other antibody preparations, raised against B. anthracis Vollum, New Hampshire, Ames and Strain 15, reacted to an approximately similar degree with spores of all four strains and of Sterne, indicating that Vollum has at least one spore antigen in common with these other strains. The anti-Sterne and anti-Vollum conjugates both displayed cross-reactions with spores of strains of B. cereus, B. coagulans, B. subtilis, B. megaterium, B. polymyxa, B. pumilus and B. thuringiensis. Absorption of the anti-anthrax conjugates with B. cereus NCTC 8035 and NCTC 10320 removed all these cross-reactions, demonstrating the existence of spore antigens specific for anthrax.     

Genetic control of resistance to the sterol 14alpha-demethylase inhibitor fungicide prochloraz in the cereal eyespot pathogen Tapesia yallundae

Sexual crosses were used to determine the genetic basis of resistance to the sterol 14 alpha-demethylase inhibitor fungicide prochloraz in the cereal eyespot pathogen Tapesia yallundae. Three different crosses between sensitive parental strains (22-432 and 22-433 [the concentration required to inhibit growth by 50% (IG(50)) for each was 相似文献   

Investigation of spore surface antigens in the genus Bacillus by the use of polyclonal antibodies in immunofluorescence tests

Fluorescein-conjugated rabbit antibodies to formalized spores of Bacillus anthracis were tested against strains of B. anthracis and other Bacillus species in a subjective immunofluorescence test. The lack of reaction of B. anthracis Vollum spores with conjugated antibody raised against B. anthracis Sterne spores indicated that spores of the Vollum strain lacked a major surface antigen present in most of the other anthrax strains tested, including the non-encapsulated strains Sterne and the Soviet ST1, variants cured of the pX01 plasmid that codes for the toxin, and several virulent strains. Four other antibody preparations, raised against B, anthracis Vollum, New Hampshire, Ames and Strain 15, reacted to an approximately similar degree with spores of all four strains and of Sterne, indicating that Vollum has at least one spore antigen in common with these other strains. The anti-Sterne and anti-Vollum conjugates both displayed cross-reactions with spores of strains of B. cereus, B. coagulans, B. subtilis, B. megaterium, B. polymyxa, B. pumilus and B. thuringiensis. Absorption of the anti-anthrax conjugates with B. cereus NCTC 8035 and NCTC 10320 removed all these cross-reactions, demonstrating the existence of spore antigens specific for anthrax.     

Genotyping of Human Brucella melitensis Biovar 3 Isolated from Shanxi Province in China by MLVA16 and HOOF

Background

Brucellosis presents a significant economic burden for China because it causes reproductive failure in host species and chronic health problems in humans. These problems can involve multiple organs. Brucellosis is highly endemic in Shanxi Province China. Molecular typing would be very useful to epidemiological surveillance. The purpose of this study was to assess the diversity of Brucella melitensis strains for epidemiological surveillance. Historical monitoring data suggest that Brucella melitensis biovar 3 is the predominant strain associated with the epidemic of brucellosis in Shanxi Province.

Methods/Principal Findings

Multiple-locus variable-number repeat analysis (MLVA-16) and hypervariable octameric oligonucleotide fingerprinting (HOOF-print) were used to type a human-hosted Brucella melitensis population (81 strains). Sixty-two MLVA genotypes (discriminatory index: 0.99) were detected, and they had a genetic similarity coefficient ranging from 84.9% to 100%. Eighty strains of the population belonged to the eastern Mediterranean group with panel 1 genotypes 42 (79 strains) and 43 (1 strain). A new panel 1 genotype was found in this study. It was named 114 MLVAorsay genotype and it showed similarity to the two isolates from Guangdong in a previous study. Brucella melitensis is distributed throughout Shanxi Province, and like samples from Inner Mongolia, the eastern Mediterranean genotype 42 was the main epidemic strain (97%). The HOOF-printing showed a higher diversity than MLVA-16 with a genetic similarity coefficient ranging from 56.8% to 100%.

Conclusions

According to the MLVA-16 and HOOF-printing results, both methods could be used for the epidemiological surveillance of brucellosis. A new genotype was found in both Shanxi and Guangdong Provinces. In areas with brucellosis, the MLVA-16 scheme is very important for tracing cases back to their origins during outbreak investigations. It may facilitate the expansion and eradication of the disease.     

Comparing Competitive Fitness of West Nile Virus Strains in Avian and Mosquito Hosts

Enzootic transmission of West Nile virus (WNV; Flaviviridae, Flavivirus) involves various species of birds and ornithophilic mosquitoes. Single nucleotide substitutions in the WNV genome may impact viral fitness necessary for WNV adaptation and evolution as previously shown for the WN02 genotype. In an effort to study phenotypic change, we developed an in vivo fitness competition model in two biologically relevant hosts for WNV. The House Finch (HOFI; Haemorhous mexicanus) and Culex tarsalis mosquitoes represent moderately susceptible hosts for WNV, are highly abundant in Western North America and frequently are infected with WNV in nature. Herein, we inoculated HOFIs and Cx. tarsalis competitively (dually) and singly with infectious-clone derived viruses of the founding California isolate COAV997-2003 (COAV997-IC), the founding North American isolate NY99 (NY99-IC), and a 2004 field isolate from California (CA-04), and compared the replicative capacities (fitness) of these viruses to a genetically marked virus of COAV997 (COAV997-5nt) by measuring RNA copy numbers. COAV997 and COAV997-5nt exhibited neutral fitness in HOFIs and Cx. tarsalis, and the temperature-sensitive phenotype of COAV997 did not affect replication in HOFIs as none of the infected birds became febrile. The NY99 and CA-04 isolates demonstrated elevated fitness in HOFIs compared to COAV997-5nt, whereas all viruses replicated to similar titers and RNA copies in Cx. tarsalis, and the only fitness differences were related to infection rates. Our data demonstrated that competitive replication allows for the sensitive comparison of fitness differences among two genetically closely related viruses using relevant hosts of WNV while eliminating host-to-host differences. In conclusion, our approach may be helpful in understanding the extent of phenotypic change in fitness associated with genetic changes in WNV.     

Differentiation of Two New York Isolates of Pratylenchus penetrans Based on Their Reaction on Potato

The behavior of two isolates of Pratylenchus penetrans on six potato clones was assessed to test the hypothesis that these nematode isolates from New York were different. Four potato cultivars (Superior, Russet Burbank, Butte, and Hudson) and two breeding lines (NY85 and L118-2) were inoculated with nematode isolates designated Cornell (CR) and Long Island (LI). Population increase and egression of nematodes from roots were used to distinguish resistance and susceptibility of the potato clones. Based on numbers of eggs, juveniles, and adults in their roots 30 days after inoculation, potato clones Butte, Hudson, and L118-2 were designated resistant to the CR isolate and susceptible to the LI isolate. More eggs were found in the roots of all plants inoculated with the LI isolate than with the CR isolate. The clones NY85 and L118-2 were inoculated with the CR and LI isolates in a 2 x 2 factorial experiment to assess differences in nematode egression. Egression was measured, beginning 3 days after inoculation, for 12 days. The rates of egression were similar for the four treatments and fit linear regression models, but differences were detected in numbers of egressed nematodes. More nematodes of the CR isolate than the LI isolate egressed from L118-2. Differences in egression of females was particularly significant and can be used as an alternative or supplement to reproduction tests to assess resistance in potato to P. penetrans and to distinguish variation in virulence.     

Population genetic structure and history of fragmented remnant populations of the New England cottontail (<Emphasis Type="Italic">Sylvilagus transitionalis</Emphasis>)

The New England cottontail (Sylvilagus transitionalis) has suffered from extensive loss and fragmentation of its habitat and is now a species of conservation priority in the northeastern United States. Remnant New England cottontail populations currently occur in five geographically disjunct locations: southern Maine and southeastern New Hampshire (MENH); the Merrimack Valley in central New Hampshire (NH-MV); Cape Cod, Massachusetts (CC); parts of eastern Connecticut and Rhode Island (CTRI); and western Connecticut, southeastern New York and southwestern Massachusetts (CTNY). We used microsatellite genotyping to discern patterns of population structure, genetic variability, and demographic history across the species’ range and to assess whether the observed patterns are a consequence of recent habitat loss and fragmentation. Our findings show that the geographic populations are highly differentiated (overall F _ST = 0.145; P < 0.001). Using Bayesian clustering analyses, we identified five genetic clusters, which corresponded closely to the geographic populations, but grouped MENH & NH-MV together (ME/NH) and identified an isolated population in eastern Connecticut (Bluff Point). The genetic clusters showed little evidence of recent gene flow and are highly influenced by genetic drift. The CC and Bluff Point populations show signs they experienced a genetic bottleneck, whereas the ME/NH population shows evidence of ongoing decline. Populations in Bluff Point, CC, and ME/NH also show significantly reduced genetic variation relative to the other clusters (CTNY and CTRI without Bluff Point). Without immediate human intervention, the short-term persistence of New England cottontail populations in Maine, New Hampshire and Cape Cod is at great risk. Conservation efforts at this time should focus on within-population sustainability and eventually restoring connectivity among these isolated populations.     

Restriction enzyme analysis of Listeria monocytogenes strains associated with food-borne epidemics

Listeria monocytogenes (serotype 4b) has caused four major food-borne epidemics in North America. In this study, L. monocytogenes isolates from the Nova Scotia (Canada), Boston (Mass.), and Los Angeles (Calif.) outbreaks were examined by restriction enzyme analysis with the endonuclease HhaI. Human isolates (n = 32) from the 1981 Canadian outbreak were compared with a strain recovered from coleslaw, which was epidemiologically incriminated as the vehicle of infection. After HhaI digestion, 29 of 32 isolates exhibited the restriction enzyme pattern of the reference coleslaw isolate. The restriction enzyme patterns of the nine clinical isolates from the 1983 Massachusetts outbreak were identical to each other but differed from those of raw milk isolates recovered from sources supplying the pasteurizer. Isolates (n = 48) from the 1985 California outbreak were evaluated. The restriction enzyme patterns of the L. monocytogenes isolates from humans and from the suspect cheese samples were identical to those of four of five cheese factory environmental isolates. Isolates from each of these outbreaks exhibited a restriction enzyme pattern that was characteristic of that outbreak. The case with which restriction enzyme analysis can be applied to all serotypes of L. monocytogenes argues for its use in the epidemiology of L. monocytogenes.     

Restriction enzyme analysis of Listeria monocytogenes strains associated with food-borne epidemics.

Listeria monocytogenes (serotype 4b) has caused four major food-borne epidemics in North America. In this study, L. monocytogenes isolates from the Nova Scotia (Canada), Boston (Mass.), and Los Angeles (Calif.) outbreaks were examined by restriction enzyme analysis with the endonuclease HhaI. Human isolates (n = 32) from the 1981 Canadian outbreak were compared with a strain recovered from coleslaw, which was epidemiologically incriminated as the vehicle of infection. After HhaI digestion, 29 of 32 isolates exhibited the restriction enzyme pattern of the reference coleslaw isolate. The restriction enzyme patterns of the nine clinical isolates from the 1983 Massachusetts outbreak were identical to each other but differed from those of raw milk isolates recovered from sources supplying the pasteurizer. Isolates (n = 48) from the 1985 California outbreak were evaluated. The restriction enzyme patterns of the L. monocytogenes isolates from humans and from the suspect cheese samples were identical to those of four of five cheese factory environmental isolates. Isolates from each of these outbreaks exhibited a restriction enzyme pattern that was characteristic of that outbreak. The case with which restriction enzyme analysis can be applied to all serotypes of L. monocytogenes argues for its use in the epidemiology of L. monocytogenes.