A descriptive study on spatial and temporal distributions of genetic clusters of porcine reproductive and respiratory syndrome virus infecting pig sites in Quebec, Canada, between 2010 and 2019.

BACKGROUND: The wide diversity of porcine reproductive and respiratory syndrome virus (PRRSV) strains combined with incomplete heterologous cross-protection complicates the management of the disease at both the herd and the regional levels. The objectives of this study were to describe the spatial and temporal distribution of various PRRSV genetic clusters infecting pig sites in Quebec, Canada, and to compare PRRSV regional diversity of wild-type sequences over the years. MATERIALS AND METHODS: A retrospective surveillance-based study was conducted on all pig sites which had PRRSV ORF5 sequences from field submissions transferred into the Laboratoire d'épidémiologie et de médecine porcine database from January 1, 2010 to December 31, 2019. A maximum likelihood phylogenetic tree inferred from multiple sequence alignment was used to identify genetic clusters. For each wild-type cluster gathering ≥ 15 sequences, the number of pig sites in which the cluster was detected per administrative region and per year were displayed on bubble charts and the spatiotemporal distribution of pig sites was illustrated using pie chart maps. A molecular analysis of variance was performed to compare PRRSV wild-type sequence diversity according to the administrative region for each year. RESULTS: A total of 32 wild-type clusters gathering 1653 PRRSV2 sequences from 693 pig sites were described. Each cluster was detected on up to 132 pig sites and 7 administrative regions over the 10-year period. Annually, the mean (min-max) number of wild-type clusters detected in at least one pig site reached 24 (17-29). Some clusters remained localized on a few sites over time whereas others were widespread over the territory during a few or many years. For each year, regional differences were also observed in PRRSV diversity of wild-type sequences. CONCLUSIONS: The differences observed in both the spatiotemporal distributions of PRRSV clusters and in the regional diversity of wild-type sequences highlight the importance of ongoing provincial surveillance to improve collective PRRS management strategies.

Potential of a probabilistic framework for target prediction from surrogate respiratory motion during lung radiotherapy.

Purpose.Respiration-induced motion introduces significant positioning uncertainties in radiotherapy treatments for thoracic sites. Accounting for this motion is a non-trivial task commonly addressed with surrogate-based strategies and latency compensating techniques. This study investigates the potential of a new unified probabilistic framework to predict both future target motion in real-time from a surrogate signal and associated uncertainty.Method.A Bayesian approach is developed, based on a Kalman filter theory adapted specifically for surrogate measurements. Breathing motions are collected simultaneously from a lung target, two external surrogates (abdominal and thoracic markers) and an internal surrogate (liver structure) for 9 volunteers during 4 min, in which severe breathing changes occur to assess the robustness of the method. A comparison with an artificial non-linear neural network (NN) is performed, although no confidence interval prediction is provided. A static worst-case scenario and a simple static design are investigated.Results.Although the NN can reduce the prediction errors from thoracic surrogate in some cases, the Bayesian framework outperforms in most cases the NN when using the other surrogates: bias on predictions is reduced by 38% and 16% on average when using respectively the liver and the abdomen for the simple scenario, and by respectively 40% and 31% for the worst-case scenario. The standard deviation of residuals is reduced on average by up to 42%. The Bayesian method is also found to be more robust to increasing latencies. The thoracic marker appears to be less reliable to predict the target position, while the liver shows to be a better surrogate. A statistical test confirms the significance of both observations.Conclusion.The proposed framework predicts both the future target position and the associated uncertainty, which can be valuably used to further assist motion management decisions. Further investigation is required to improve the predictions by using an adaptive version of the proposed framework.

Association Between Tail-Biting and Intestinal Microbiota Composition in Pigs.

Tail-biting (TB) in pigs is a serious behavioral disorder. It is an important challenge in swine production as it impacts animal welfare and health and the economics and safety of the pork meat supply chain. To prevent TB, approaches including enrichment material and tail docking are proposed but none are optimal. Nutrition appears to be an important factor in TB behavior, perhaps by modulating the intestinal microbiota (IM). Our aim was to assess the association between TB behavior and IM in pigs through comparisons of IM in groups of biter, bitten and non-biter/non-bitten pigs. Each group composed of 12 pigs was formed at the beginning of the growing/finishing phase based on a target behavior analysis centered on TB behavior for the biter group and a score of damages caused to the tail for the bitten group. Blood and fecal samples were collected from each pig during a TB episode, at time 0, t0, and when the TB episode was considered finished, 4 weeks later, at time 1, t1. Serum cortisol level was determined by ELISA and used as an indicator of stress. The pig's fecal microbiota was analyzed from DNA extracted from freshly collected fecal matter using amplicon sequencing of the V4 hypervariable region of the 16S rRNA gene. Serum cortisol levels were significantly higher in either the biter or bitten pig groups compared to the negative control group (p = 0.02 and p = 0.01, respectively). The microbiota alpha-diversity was not significantly different between all groups, biter, bitten and negative control. Analyses of beta-diversity, however, revealed a significant difference between either the biter or the bitten group in comparison to the non-biter/non-bitten negative control group in terms of structure and composition of the microbiota. Lactobacillus were significantly more abundant in the negative control group compared to the two other groups (p = 0.001). No significant difference was revealed between the biter and bitten groups. Quantitative real-time PCR (qPCR) confirmed that lactobacilli were more abundant in the negative control group. Our study indicates that TB behavior is associated with the IM composition in pigs.

Phantom-based quality assurance for multicenter quantitative MRI in locally advanced cervical cancer.

BACKGROUND AND PURPOSE: A wide variation of MRI systems is a challenge in multicenter imaging biomarker studies as it adds variation in quantitative MRI values. The aim of this study was to design and test a quality assurance (QA) framework based on phantom measurements, for the quantitative MRI protocols of a multicenter imaging biomarker trial of locally advanced cervical cancer. MATERIALS AND METHODS: Fifteen institutes participated (five 1.5 T and ten 3 T scanners). Each institute optimized protocols for T2, diffusion-weighted imaging, T1, and dynamic contrast-enhanced (DCE-)MRI according to system possibilities, institutional preferences and study-specific constraints. Calibration phantoms with known values were used for validation. Benchmark protocols, similar on all systems, were used to investigate whether differences resulted from variations in institutional protocols or from system variations. Bias, repeatability (%RC), and reproducibility (%RDC) were determined. Ratios were used for T2 and T1 values. RESULTS: The institutional protocols showed a range in bias of 0.88-0.98 for T2 (median %RC = 1%; %RDC = 12%), -0.007 to 0.029 × 10-3 mm2/s for the apparent diffusion coefficient (median %RC = 3%; %RDC = 18%), and 0.39-1.29 for T1 (median %RC = 1%; %RDC = 33%). For DCE a nonlinear vendor-specific relation was observed between measured and true concentrations with magnitude data, whereas the relation was linear when phase data was used. CONCLUSION: We designed a QA framework for quantitative MRI protocols and demonstrated for a multicenter trial for cervical cancer that measurement of consistent T2 and apparent diffusion coefficient values is feasible despite protocol differences. For DCE-MRI and T1 mapping with the variable flip angle method, this was more challenging.

Distribution, diversity and persistence of Listeria monocytogenes in swine slaughterhouses and their association with food and human listeriosis strains.

Listeria monocytogenes is the etiological agent of listeriosis, a major foodborne disease and an important public health concern. Contamination of meat with L. monocytogenes occurs frequently at the slaughterhouse. Our aims were; 1) to investigate the distribution of L. monocytogenes in the processing areas of four swine slaughterhouses; 2) to describe the diversity of L. monocytogenes strains by pulsed-field gel electrophoresis; 3) to identify persistent L. monocytogenes strains and describe their distribution; 4) to investigate the associations between persistence of strains and their following characteristics: detection in food isolates, detection in human clinical isolates, and the presence of benzalkonium chloride (BAC) resistance genes. Various operation areas within the four swine slaughterhouses were sampled on four occasions. A total of 2496 samples were analyzed, and L. monocytogenes was successfully isolated from 243 samples. The proportion of positive samples ranged from 32 to 58% in each slaughterhouse and from 24 to 68% in each operation area. Fifty-eight different pulsotypes were identified and eight pulsotypes, present in samples collected during 4 visits, were considered persistent. The persistent pulsotypes were significantly more likely to be detected in food (P < 0.01, exact χ²) and human clinical cases (P < 0.01, exact χ²), respectively. Among pulsotypes harboring the BAC bcrABC resistance cassette or the emrE multidrug transporter gene, 42.8% were persistent compared to 4.5% for pulsotypes without these resistance genes (P < 0.01, exact χ²). Our study highlights the importance of persistent L. monocytogenes strains in the environmental contamination of slaughterhouses, which may lead to repeated contamination of meat products. It also shows that the presence of disinfectants resistance genes is an important contributing factor.

Contribution of the Broiler Breeders' Fecal Microbiota to the Establishment of the Eggshell Microbiota.

In broiler chicken production, microbial populations on the eggshell surface following oviposition are still poorly characterized, though they may significantly impact both poultry and public health. The aim of this study was to describe the microbiota of both broiler breeder hens' feces and the surface of their eggs to assess the contribution of the parental fecal microbiota to the eggshell microbiota. A total of twelve breeder flocks in Quebec, Canada, were sampled at two different times, and a total of 940 feces and 16,400 egg surface samples were recovered. Using 16S rRNA gene sequencing, we showed that even if the microbiota of both feces and eggshells were mainly composed of the phyla Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes, the bacterial community compositions and structures differed between both types of samples. Our results also showed that both the sampling time and the flock identity significantly influenced the alpha- and the beta-diversities of the studied microbiomes. Using a Venn diagram, we showed that 1790 operational taxonomic units (OTUs) were shared between feces and eggshell samples. Sequences associated with genera of potentially pathogenic and spoilage bacteria, Acinetobacter, Campylobacter, Escherichia/Shigella, Helicobacter, Listeria, Proteus, Pseudomonas, Salmonella, and Staphylococcus, were shared between sample types. Some OTUs highly represented in the fecal microbiota and associated with Lactobacillus and Streptococcus genera, were absent from eggshells, suggesting a selection during the microbiota transfer and/or the potential role of environmental contamination. To the best of our knowledge, this is the first study using 16S rRNA sequencing to describe the contribution of the transfer from the fecal microbial ecosystem of laying breeder hens to the establishment of the microbiota on the surface of laid eggs, as well as the bacterial communities at both the broiler breeder feces and the eggshell levels.

Salmonella contamination in a network of 10 pig farms interconnected within the same cooperative.

OBJECTIVE: To evaluate whether pig farms interconnected within the same cooperative share similar Salmonella contamination patterns. SETTING: Ten finishing pig farms within a 100 km radius of a common slaughterhouse were selected. Their inclusion was based on their association to the same cooperative and the sharing of common resources: piglets, feed, swine transporters, slaughterhouse, technicians and veterinarians. PROCEDURE: Each farm was visited three times over a 10-month period. Pig faeces, the barn front door handle, the feed pipeline, mobile objects (shovel, balance and pig board), the landing stage, the concrete slab of the feed bins, the tire tracks left on the pathways by the animal feed truck, the pig delivery truck and the carcase knacker truck and the mudguards and cabin carpets of the veterinarian and technician vehicles on their arrival at the farm were all analysed for the presence of Salmonella. RESULTS: All farms were not equally contaminated with Salmonella. Whereas some farms yielded up to 12 Salmonella isolates, other farms were Salmonella free. Some locations, most notably the landing stage, were more contaminated than others. Salmonella contamination was dynamic in time. Some contaminations seen on farms, on specific locations on the first visit, had disappeared on the second and third visits, but new contaminations were detected on different locations. CONCLUSIONS: Contamination with Salmonella was not disseminated through the network of the 10 pig farms interconnected within the same cooperative but was rather most often restricted in time to specific locations on specific farms.

Overlooked sources of Salmonella contamination in the pig production network: Slaughterhouse yard pathways and mudguards and carpets from transport trucks.

This report describes various Salmonella serovars which were found on often overlooked locations in a pig farm/slaughterhouse interface. These include slaughterhouse yard pathways and mudguards and carpets of transport trucks arriving at and departing from production sites.

Sources négligées de contamination par Salmonella dans un réseau de production de porcs: les voies de circulation de l'abattoir et les garde-boues et les tapis de cabine des camions de transport. Nous montrons ici que Salmonella, l'agent causal de la salmonellose, peut être trouvé sur des sites très inhabituels et négligés dans l'interface ferme porcine/abattoir: les voies de circulation de la cour d'abattoir, et les garde-boues et tapis des camions de transport qui arrivent et partent vers les sites de production.(Traduit par les auteurs).

A Novel Plasmid, pSx1, Harboring a New Tn1696 Derivative from Extensively Drug-Resistant Shewanella xiamenensis Encoding OXA-416.

The whole genome sequencing of extensively drug-resistant Shewanella xiamenensis T17 isolated from hospital effluents in Algeria revealed the presence of a novel 268.4 kb plasmid designated pSx1, which carries several antibiotic-resistance genes in the novel Tn1696 derivative (Tn6297), in addition to the chromosomal blaOXA-48-like gene (blaOXA-416). The presence of the plasmid was confirmed by nuclease S1-PFGE analysis and transformation by electroporation into Escherichia coli DH10B. Tn6297 contains an In27 class 1 integron harboring the dfrA12-orfF-aadA2 array, msr(E) and mph(E) associated with IS26; a new efflux pump multidrug resistance composite transposon delimited by two ISEc29s; Tn-tet harboring tetR and tetA(C); a class 1 integron with the qacG gene cassette; qnrVC6 and dfrA23 associated with ISCR1; and a complex class 1 integron In4-like containing aacC1, aadA1, blaVEB-16, catA2, sul1Δ, cmlA9, tetR, tetA(G), aac(6')-II, and blaPSE-1. Its mer operon carries merB, but lacks merC, in contrast to Tn1696 and Tn21. This study represents the first characterization of a multidrug-resistant transposon and multidrug resistance plasmid in Shewanella and is the first report of blaOXA-416 in Algeria, providing evidence that Shewanella spp. could be an important reservoir and vehicle for drug resistance genes.

First Report of Clostridium lavalense Isolated in Human Blood Cultures.

An 88-year-old man was admitted to the hospital with worsening malaise, fever, and weakness. Anaerobic blood culture bottles revealed the presence of an anaerobic, Gram-positive sporulated bacillus. Empirical antibiotherapy with intravenous piperacillin-tazobactam was initiated. The patient defervesced after four days and was switched to oral amoxicillin on his 6th day of antibiotic therapy and later discharged from the hospital. Four months later, he had recovered. The bacterium was initially identified as Clostridium butyricum using anaerobic manual identification panel. 16S rRNA gene sequence and phylogenetic analysis showed the bacterium to be Clostridium lavalense, a recently described species with no previously published case of isolation in human diagnostic samples so far. This is the first report of Clostridium lavalense isolation from human blood cultures. Further studies are needed in order to elucidate the role of Clostridium lavalense in human disease and its virulence factors.

A Fatal Case of Necrotizing Fasciitis Caused by a Highly Virulent Escherichia coli Strain.

Necrotizing fasciitis is a serious disease characterized by the necrosis of the subcutaneous tissues and fascia. E. coli as the etiologic agent of necrotizing fasciitis is a rare occurrence. A 66-year-old woman underwent total abdominal hysterectomy with bilateral salpingo-oophorectomy. She rapidly developed necrotizing fasciitis which led to her death 68 hours following surgery. An E. coli strain was isolated from blood and fascia cultures. DNA microarray revealed the presence of 20 virulence genes.

Draft Genome Sequence of a Necrotoxigenic Escherichia coli Isolate.

Here, we present the draft genome sequence of a necrotoxigenic Escherichia coli strain isolated from a patient following a very rapidly evolving, lethal necrotizing fasciitis.

Parasporin-2 from a New Bacillus thuringiensis 4R2 Strain Induces Caspases Activation and Apoptosis in Human Cancer Cells.

In previous studies, parasporin-2Aa1, originally isolated from Bacillus thuringiensis strain A1547, was shown to be cytotoxic against specific human cancer cells but the mechanisms of action were not studied. In the present study, we found that proteinase K activated parasporin-2Aa1 protein isolated from a novel B. thuringiensis strain, 4R2, was specifically cytotoxic to endometrial, colon, liver, cervix, breast and prostate cancer. It showed no toxicity against normal cells. Upon treatment with proteinase K-activated parasporin-2Aa1, morphological changes were observed and western blot analysis revealed the cleavage of poly (ADP-Ribose) polymerase, caspase-3 and caspase-9 in cancer cell lines exclusively, indicative of programmed cell death, apoptosis. Flow cytometry analyses,using propidium iodide and annexin V, as well as a caspases 3/7 assay confirmed apoptosis induction. Further analyses were performed to study survival pathways, including AKT, XIAP, ERK1/2 and PAR-4, a known inducer of apoptosis. These results indicate that parasporin-2Aa1 is a selective cytotoxic protein that induces apoptosis in various human cancer cell lines from diverse tissues.

Draft Genome Sequences of Two Toxigenic Corynebacterium ulcerans Strains.

Here, we present the draft genome sequences of two toxigenic Corynebacterium ulcerans strains isolated from two different patients: one from a blood sample and the other from a scar exudate following surgery. Although these two strains harbor the diphtheria toxin gene tox, no full prophage sequences were found in the flanking regions.

Discrimination between mesophilic and psychrotolerant strains in the Bacillus cereus group based on the PstI digestion of the pycA gene.

A simple and rapid assay for the detection of Bacillus weihenstephanensis isolates and other psychrotolerant strains in the Bacillus cereus group was developed. It is based on the presence of a nucleotide substitution at position 795 on the housekeeping pycA gene in all B. weihenstephanensis strains. This mutation creates a PstI recognition site. It is absent in mesophilic strains in the B. cereus group. The pycA gene is amplified by PCR and the amplicons submitted to PstI digestions. In mesophilic strains, a single band of 1,718 bp in length is visualised on an agarose gel. In B. weihenstephanensis strains and in all other psychrotolerant strains from the B. cereus group, the amplicons are cleaved and two bands of 1,175 and 543 bp, respectively, are visualised. This method could be used for the screening of B. cereus collections and for the identification of psychrotolerant and mesophilic isolates from different environments.

Bacillus weihenstephanensis characteristics are present in Bacillus cereus and Bacillus mycoides strains.

The Bacillus cereus group comprises seven bacterial species: Bacillus cereus, Bacillus anthracis, Bacillus thuringiensis, Bacillus mycoides, Bacillus pseudomycoides, Bacillus cytotoxicus, and Bacillus weihenstephanensis. Bacillus weihenstephanensis is distinguished based on its capability to grow at 7 °C but not at 43 °C, and the presence of specific signature sequences in the 16S rRNA and cspA genes and in several housekeeping genes: glpF, gmK, purH, and tpi. Bacillus weihenstephanensis-specific signature sequences were found in some B. cereus and B. mycoides strains suggesting psychrotolerance. This was confirmed by growth at 7 °C but not at 43 °C. The other B. cereus and B. mycoides strains and all B. anthracis, B. thuringiensis, and B. pseudomycoides harbored the mesophilic signature sequences. The strains tested grew at 43 °C but did not grow at 7 °C. A maximum-likelihood phylogenetic tree was inferred from comparisons of the concatenated nucleotide sequences. Three groups and one branch were revealed. Group I, II, and III comprised the mesophilic B. cereus, some mesophilic B. mycoides, and all B. anthracis and B. thuringiensis strains; the psychrotolerant B. cereus and B. mycoides, and all B. weihenstephanensis strains; and some mesophilic B. mycoides and all B. pseudomycoides strains, respectively. The branch corresponds to the single B. cytotoxicus strain. Based on psychrotolerance and multilocus sequence analysis, further confirmed by comparisons of amino acid sequences, we show that some B. cereus and B. mycoides strains should be reclassified as B. weihenstephanensis.

Multilocus sequence analysis of Bacillus thuringiensis serovars navarrensis, bolivia and vazensis and Bacillus weihenstephanensis reveals a common phylogeny.

The Bacillus cereus group sensu lato includes six closely-related bacterial species: Bacillus cereus, Bacillus anthracis, Bacillus thuringiensis, Bacillus mycoides, Bacillus pseudomycoides and Bacillus weihenstephanensis. B. thuringiensis is distinguished from the other species mainly by the appearance of an inclusion body upon sporulation. B. weihenstephanensis is distinguished based on its psychrotolerance and the presence of specific signature sequences in the 16S rRNA gene and cspA genes. A total of seven housekeeping genes (glpF, gmK, ilvD, pta, purH, pycA and tpi) from different B. thuringiensis serovars and B. weihenstephanensis strains were amplified and their nucleotide sequences determined. A maximum likelihood phylogenetic tree was inferred from comparisons of the concatenated sequences. B. thuringiensis serovars navarrensis, bolivia and vazensis clustered not with the other B. thuringiensis serovars but rather with the B. weihenstephanensis strains, indicative of a common phylogeny. In addition, specific signature sequences and single nucleotide polymorphisms common to B. thuringiensis serovars navarrensis, bolivia and vazensis and the B. weihenstephanensis strains, and absent in the other B. thuringiensis serovars, were identified.

Mutually exclusive distribution of the sap and eag S-layer genes and the lytB/lytA cell wall hydrolase genes in Bacillus thuringiensis.

Recently, two Bacillus thuringiensis strains were reported to synthesize parasporal inclusion bodies made not of the expected crystal (Cry) proteins but rather of the surface layer proteins (SLP) Sap (encoded by sap) and EA1 (encoded by eag), respectively. Whether the presence of the sap and eag genes is restricted to these two B. thuringiensis strains or ubiquitous in B. thuringiensis is unknown. We report here the distribution of the sap and eag genes in B. thuringiensis. Strains in the Bacillus cereus group were added for comparison purposes. We show that sap and eag are either present in tandem in 35% of the B. thuringiensis strains analysed and absent in 65% of the strains. When absent, a different tandem, the lytB/lytA cell wall hydrolase genes, is present. The distribution of the sap and eag S-layer and the lytB/lytA cell wall hydrolase genes is not species-specific in B. thuringiensis, B. cereus and Bacillus weihenstephanensis. Bacillus anthracis and Bacillus mycoides harbor sap and eag but not lytB/lytA. The sap, eag and lytB/lytA genes were absent in Bacillus pseudomycoides. Clearly, the distribution of the sap and eag S-layer and the lytB/lytA cell wall hydrolase genes in B. thuringiensis and in the Bacillus cereus group is mutually exclusive. We also showed that two genes involved in cell wall metabolism, csaA and csaB, are present not only upstream of the sap and eag S-layer genes, but also upstream of the lytB/lytA tandem in strains where sap and eag are absent. Bootstrapped neighbor-joining trees were inferred from the translated amino acid sequences of sap, eag and the tandem lytB/lytA, respectively.

Bacillus thuringiensis serovars bolivia, vazensis and navarrensis meet the description of Bacillus weihenstephanensis.

The Bacillus cereus sensu lato group comprises six related species: B. cereus, B. anthracis, B. thuringiensis, B. mycoides, B. pseudomycoides and B. weihenstephanensis. Bacillus thuringiensis is a mesophile. It is distinguished from other members of the B. cereus group by the apparition of an inclusion body upon sporulation. B. weihenstephanensis, however, is a psychrotolerant. It grows at 7 degrees C but not at 43 degrees C. It is further characterised by the presence of specific signature sequences on two genes, the 16S rRNA gene (the small subunit ribosomal RNA gene) and cspA (encoding the major cold shock protein). Five B. thuringiensis serovars selected from previous studies, bolivia, vazensis, navarrensis, azorensis and asturiensis were studied here for their capability to grow at 7 degrees C but not at 43 degrees C. Next, their 16S rRNA and cspA genes were analysed for the presence of B. weihenstephanensis-specific signature sequences. Bacillus thuringiensis serovars bolivia, vazensis and navarrensis met the description of B. weihenstephanensis.

Discrimination among Bacillus thuringiensis H serotypes, serovars and strains based on 16S rRNA, gyrB and aroE gene sequence analyses.

Our aim was to investigate the capability of each of three genes, 16S rRNA, gyrB and aroE, to discriminate, first, among Bacillus thuringiensis H serotypes; second, among B. thuringiensis serovars from the same H serotype; and third, among B. thuringiensis strains from the same serovar. The 16S rRNA, gyrB and aroE genes were amplified from 21 B. thuringiensis H serotypes and their nucleotide sequences determined. Additional strains from four B. cereus sensu lato species were included for comparison purposes. These sequences were pair-wise compared and phylogenetic relationships were revealed. Each of the three genes under study could discriminate among B. thuringiensis H serotypes. The gyrB and aroE genes showed a discriminatory power among B. thuringiensis H serotypes up to nine fold greater than that of the 16S rRNA gene. The gyrB gene was retained for subsequent analyses to discriminate B. thuringiensis serovars from the same H serotype and to discriminate strains from same serovar. A total of 42 B. thuringiensis strains, which encompassed 25 serovars from 12 H serotypes, were analyzed. The gyrB gene nucleotide sequences were different enough as to be sufficient to discriminate among B. thuringiensis serovars from the same H serotype and among B. thuringiensis strains from the same serovar.