Isolation and Characterization of Two Novel Genera of Jumbo Bacteriophages Infecting Xanthomonas vesicatoria Isolated from Agricultural Regions in Mexico.

Bacterial spot is a serious disease caused by several species of Xanthomonas affecting pepper and tomato production worldwide. Since the strategies employed for disease management have been inefficient and pose a threat for environmental and human health, the development of alternative methods is gaining relevance. The aim of this study is to isolate and characterize lytic phages against Xanthomonas pathogens. Here, we isolate two jumbo phages, named XaC1 and XbC2, from water obtained from agricultural irrigation channels by the enrichment technique using X. vesicatoria as a host. We determined that both phages were specific for inducing the lysis of X. vesicatoria strains, but not of other xanthomonads. The XaC1 and XbC2 phages showed a myovirus morphology and were classified as jumbo phages due to their genomes being larger than 200 kb. Phylogenetic and comparative analysis suggests that XaC1 and XbC2 represent both different and novel genera of phages, where XaC1 possesses a low similarity to other phage genomes reported before. Finally, XaC1 and XbC2 exhibited thermal stability up to 45 °C and pH stability from 5 to 9. All these results indicate that the isolated phages are promising candidates for the development of formulations against bacterial spot, although further characterization is required.

Virulent shiga toxin-producing Escherichia coli (STEC) O157:H7 ST11 isolated from ground beef in Brazil.

In this study, a total of 248 ground beef samples were analyzed for the presence of Shiga toxin-producing Escherichia coli (STEC). Out of these samples, only one (0.4%) tested positive for STEC. Further analysis using PCR confirmed the presence of all tested genes associated with STEC, including stx1, stx2, eae, ehx, uid, rfbO157, and fliCH7 in this isolate. Interestingly, no STEC strains were detected in the remaining 100 beef cut samples or the 100 chicken cut samples, indicating the absence of detectable STEC contamination in those specific samples. The isolated strain exhibited significant cytotoxic activity in Vero cells, indicating its ability to produce cytotoxic Shiga toxins. To further investigate the strain, whole-genome sequencing (WGS) analyses were performed. The resistome analysis revealed the absence of acquired antimicrobial resistance genes, indicating a pan-susceptible phenotype. However, this strain presented chromosomal mutations in gyrA, gyrB, parC, parE, pmrA, pmrB, and folP. Plasmid analysis identified the presence of two plasmids, namely IncFIB(AP001918) and IncFII. The multi-locus sequence typing (MLST) identified the strain as belonging to sequence type (ST) 11, which is associated with E. coli O157:H7 strains. The virulome analysis confirmed the presence of several canonical virulence markers, including stx1, stx2, eae-g01-gamma, ehxA, stx1a-O157, and stx2a-O157. Overall, this study identified for the first time a rare occurrence of STEC contamination in ground beef, with the isolated strain belonging to the highly virulent O157:H7 serotype. These findings contribute to our understanding of STEC prevalence and characteristics in food samples, highlighting the importance of effective food safety measures to prevent potential health risks associated with STEC contamination.

Long-term occurrence of multiple antimicrobial drug resistant Klebsiella pneumoniae isolates harboring virulent potential in a tertiary hospital from Brazil.

Klebsiella pneumoniae strains are globally associated with a plethora of opportunistic and severe human infections and are known to spread genes conferring antimicrobial resistance. Some strains harbor virulence determinants that enable them to cause serious disease in any patient, both in the hospital and in the community. The aim of this study was to determine the frequency of antimicrobial resistance and virulence traits (by gene detection and string test) among 83 K. pneumoniae isolates obtained from patient cultures of a scholar tertiary hospital in the Midwestern Brazil (Brasília, DF). Antimicrobial susceptibility analysis showed that 94% (78/83) of the isolates presented one of the following resistance profiles: resistant (R, 39), multidrug-resistant (MDR, 29), or extensively drug-resistant (XDR, 10). Several MDR and XDR strains harbored multiple virulence genes and displayed hypermucoviscous phenotype. These characteristics were observed among isolates obtained throughout all the sample collection period (2013 - 2017). The K2 serotype gene, a molecular marker of hypervirulence, was detected in three isolates, one of which classified as XDR. Sequence typing revealed the occurrence of isolates belonged to high-risk (ST13) and multiple resistance-spreading clones (ST105). Thus, our findings showed the occurrence of virulent potential isolates that also presented MDR/XDR phenotypes from 2013 to 2015. This study also indicates the probable convergence of virulence and resistance since at least 2013 in Brazil.

Molecular and Pathological Characterization of Classical Swine Fever Virus Genotype 2 Strains Responsible for the 2013-2018 Outbreak in Colombia.

Classical swine fever (CSF) is a highly contagious transboundary viral disease of domestic and wild pigs. Despite mass vaccination and continuous eradication programs, CSF remains endemic in Asia, some countries in Europe, the Caribbean and South America. Since June 2013, Northern Colombia has reported 137 CSF outbreaks, mostly in backyard production systems with low vaccination coverage. The purpose of this study was to characterize the virus responsible for the outbreak. Phylogenetic analysis based on the full-length E2 sequence shows that the virus is closely related to CSF virus (CSFV) genotype 2.6 strains circulating in Southeast Asia. The pathotyping experiment suggests that the virus responsible is a moderately virulent strain. The 190 nucleotide stretch of the E2 hypervariable region of these isolates also shows high similarity to the CSFV isolates from Colombia in 2005 and 2006, suggesting a common origin for the CSF outbreaks caused by genotype 2.6 strains. The emergence of genotype 2.6 in Colombia suggests a potential transboundary spread of CSFV from Asia to the Americas, complicating the ongoing CSF eradication efforts in the Americas, and emphasizes the need for continuous surveillance in the region.

Extracellular Vesicles From Paracoccidioides brasiliensis Can Induce the Expression of Fungal Virulence Traits In Vitro and Enhance Infection in Mice.

Extracellular vesicles (EVs) are cellular components involved in cargo delivery to the extracellular environment, including the fungal cell wall. Their importance in cell-cell communication, cell wall remodeling, and fungal virulence is starting to be better explored. In the human pathogenic Paracoccidioides spp., our group has pioneered the description of the EV secretome, carbohydrate cargo, surface oligosaccharide ligands, lipid, and RNA content. Presently, we studied the role of fungal EVs in the context of the virulent/attenuated model of the P. brasiliensis Pb18 isolate, which consists of variants transiently displaying higher (vPb18) or attenuated (aPb18) virulence capacity. In this model, the virulence traits can be recovered through passages of aPb18 in mice. Here, we have been able to revert the aPb18 sensitivity to growth under oxidative and nitrosative stress upon previous co-incubation with vEVs from virulent vPb18. That was probably due to the expression of antioxidant molecules, considering that we observed increased gene expression of the alternative oxidase AOX and peroxiredoxins HYR1 and PRX1, in addition to higher catalase activity. We showed that aEVs from aPb18 stimulated macrophages of the RAW 264.7 and bone marrow-derived types to express high levels of inflammatory mediators, specifically, TNF-α, IL-6, MCP-1, and NO. In our experimental conditions, subcutaneous treatment with EVs (three doses, 7-day intervals) before vPb18 challenge exacerbated murine PCM, as concluded by higher colony-forming units in the lungs after 30 days of infection and histopathology analysis. That effect was largely pronounced after treatment with aEVs, probably because the lung TNF-α, IFN-γ, IL-6, and MCP-1 concentrations were specially increased in aEV-treated when compared with vEV-treated mice. Our present studies were performed with EVs isolated from yeast cell washes of confluent cultures in Ham's F-12 defined medium. Under these conditions, vEVs and aEVs have similar sizes but probably distinct cargo, considering that vEVs tended to aggregate upon storage at 4°C and -20°C. Additionally, aEVs have decreased amounts of carbohydrate and protein. Our work brings important contribution to the understanding of the role of fungal EVs in cell-cell communication and on the effect of EVs in fungal infection, which clearly depends on the experimental conditions because EVs are complex and dynamic structures.

Prevalence of antibiotic resistance and virulent factors in nosocomial clinical isolates of Pseudomonas aeruginosa from Panamá

ABSTRACT Background: Pseudomonas aeruginosa is an important causative agent of nosocomial infections. As pathogen, P. aeruginosa is of increasing clinical importance due to its ability to develop high-level multidrug resistance (MDR). Methods: The aim of the present study was to better understand the intrinsic virulence of circulating strains of Pseudomonas aeruginosa, by surveying and characterizing the antibiotic resistance profiles and prevalence of virulence factors in 51 clinical isolates of P. aeruginosa obtained from children admitted to Hospital del Niño-Panamá during the period of October 2016 until March 2017. Antimicrobial susceptibilities were assessed by determining the minimum inhibitory concentration for 12 antibiotics against P. aeruginosa clinical isolates using the VITEK system (https://www.biomerieux.com). Additionally, all isolates were examined by Polymerase Chain Reaction (PCR) for the presence of components of the MexAB-OprM efflux pump system (mexABR) and pyoverdine receptor genes and betalactamases resistance genes (ESBL) using gene-specific primers. Results: A total of 51 pyoverdine producing clinical isolates were analyzed, all of which expressed resistance genes such as genes of the MexAB-OprM efflux pump system (mexABR) and pyoverdine receptor genes (fpvA). Out of 51 MDR isolates, 22 were ESBL producers. The most common ESBL gene was blaTEM expressed by 43% of the isolates. The isolates tested in this study showed increased resistance to antibiotics in the following categories: (i) penicillins (ampicillin (69%), piperacillin (22%); (ii) pyrimethamines (trimethoprim, 65%); (iii) nitrofurans (nitrofurantoin, 63%), and (iv) third-generation cephalosporin cefotaxime (53%). These results underscore a high prevalence of MDR amongst clinical isolates from Panama. Conclusions: The present study indicates that prevalence of BlaTEM-carrying strains is increasing with subsequent multidrug resistance in Panamá and as well reported worldwide. The virulent factors identified in this study provide valuable information regarding the prevalence of resistance genes and their potential impact on treatments that exploit the unique physiology of the pathogen. To prevent further spread of MDR, the proportions of resistant strains of Pseudomonas aeruginosa should be constantly evaluated on healthcare institutions of Panamá. More importantly, this information can be used to better understand the evolution and dissemination of strains hoping to prevent the development of resistance in Pseudomonas aeruginosa. Future studies quantifying the expression of these virulent genes will emphasize on the acquisition of multidrug resistance.

Prevalence of antibiotic resistance and virulent factors in nosocomial clinical isolates of Pseudomonas aeruginosa from Panamá.

BACKGROUND: Pseudomonas aeruginosa is an important causative agent of nosocomial infections. As pathogen, P. aeruginosa is of increasing clinical importance due to its ability to develop high-level multidrug resistance (MDR). METHODS: The aim of the present study was to better understand the intrinsic virulence of circulating strains of Pseudomonas aeruginosa, by surveying and characterizing the antibiotic resistance profiles and prevalence of virulence factors in 51 clinical isolates of P. aeruginosa obtained from children admitted to Hospital del Niño-Panamá during the period of October 2016 until March 2017. Antimicrobial susceptibilities were assessed by determining the minimum inhibitory concentration for 12 antibiotics against P. aeruginosa clinical isolates using the VITEK system (https://www.biomerieux.com). Additionally, all isolates were examined by Polymerase Chain Reaction (PCR) for the presence of components of the MexAB-OprM efflux pump system (mexABR) and pyoverdine receptor genes and betalactamases resistance genes (ESBL) using gene-specific primers. RESULTS: A total of 51 pyoverdine producing clinical isolates were analyzed, all of which expressed resistance genes such as genes of the MexAB-OprM efflux pump system (mexABR) and pyoverdine receptor genes (fpvA). Out of 51 MDR isolates, 22 were ESBL producers. The most common ESBL gene was blaTEM expressed by 43% of the isolates. The isolates tested in this study showed increased resistance to antibiotics in the following categories: (i) penicillins (ampicillin (69%), piperacillin (22%); (ii) pyrimethamines (trimethoprim, 65%); (iii) nitrofurans (nitrofurantoin, 63%), and (iv) third-generation cephalosporin cefotaxime (53%). These results underscore a high prevalence of MDR amongst clinical isolates from Panama. CONCLUSIONS: The present study indicates that prevalence of BlaTEM-carrying strains is increasing with subsequent multidrug resistance in Panamá and as well reported worldwide. The virulent factors identified in this study provide valuable information regarding the prevalence of resistance genes and their potential impact on treatments that exploit the unique physiology of the pathogen. To prevent further spread of MDR, the proportions of resistant strains of Pseudomonas aeruginosa should be constantly evaluated on healthcare institutions of Panamá. More importantly, this information can be used to better understand the evolution and dissemination of strains hoping to prevent the development of resistance in Pseudomonas aeruginosa. Future studies quantifying the expression of these virulent genes will emphasize on the acquisition of multidrug resistance.

Bovine macrophages responses to the infection with virulent and attenuated Leptospira interrogans serovar Pomona.

Leptospirosis is a zoonosis, caused by pathogenic spirochetes of the genus Leptospira. Although cattle are usually the maintenance hosts of serovar Hardjo, Pomona is the most frequent serovar circulating in Argentina. The understanding of bovine innate immune response and the virulence of this serovar is important for future control measures. This work compares infection of bovine macrophages with the virulent L. interrogans sv Pomona strain AKRFB (P1) and its attenuated counterpart (P19). First, we confirmed attenuation in the hamster model. Mortality and lung hemorrhages occurred after P1 inoculation, while the survival rate was 100% in P19-infected animals. Cells infected with both strains showed statistically upregulated gene expression of pro-inflammatory cytokines, IL-1ß, IL-6 and TNFα. The level of expression of anti-inflammatory cytokine IL-10 was statistically different between strains. Increased expression of IL-10 was observed only in P1-infected cells. For the first time, we describe macrophages extracellular traps induced by infection of bovine macrophages (bMETs) with both, the virulent and attenuated Leptospira interrogans Pomona strains. P1 was found higher internalized when the phagocytosis was inhibited, suggesting a cell entrance of this strain also by an independent-phagocytosis pathway. Furthermore, P1 was higher colocalized with acidic and late endosomal compartments compared with P19. This data emphasizes the importance to deepen in Leptospira bovine macrophages particular invasion mechanisms and, furthermore, underline the value of studying the main hosts.

Anatomopathological and molecular studies of Marek's disease virus in India

In India, increasing incidence of Mareks Disease Virus (MDV) outbreaks are being reported even in vaccinated poultry farms. Hence identifying the new emerging pathotype of MDV is necessary for successful control through vaccination. Birds received in the post mortem section of The Avian Disease Laboratory, Indian Veterinary Research Institute, were screened for the presence of MDV by collecting neoplastic tissues, spleen and feather follicles. Screening was carried out by polymerase chain reaction (PCR) and histopathological examination. Among the tested 150 birds tissue samples, 35 bird tissue samples were found positive for MDV. Based on pathotyping specific PCR, it was found that 34 birds tissues were affected virulent MDV and one birds tissue was affected with very virulent MDV. Since, HVT vaccine will not protect the very virulent pathotype, combined vaccine of SB-1 and HVT can be administered to control the very virulent MDV. Among the MD infected birds, neoplastic liver is most commonly encountered. Spleen tissue samples was found to be more suitable for the DNA isolation for PCR.(AU)

Anatomopathological and molecular studies of Marek's disease virus in India

In India, increasing incidence of Marek’s Disease Virus (MDV) outbreaks are being reported even in vaccinated poultry farms. Hence identifying the new emerging pathotype of MDV is necessary for successful control through vaccination. Birds received in the post mortem section of The Avian Disease Laboratory, Indian Veterinary Research Institute, were screened for the presence of MDV by collecting neoplastic tissues, spleen and feather follicles. Screening was carried out by polymerase chain reaction (PCR) and histopathological examination. Among the tested 150 birds’ tissue samples, 35 bird tissue samples were found positive for MDV. Based on pathotyping specific PCR, it was found that 34 birds tissues were affected virulent MDV and one birds tissue was affected with very virulent MDV. Since, HVT vaccine will not protect the very virulent pathotype, combined vaccine of SB-1 and HVT can be administered to control the very virulent MDV. Among the MD infected birds, neoplastic liver is most commonly encountered. Spleen tissue samples was found to be more suitable for the DNA isolation for PCR.

Severe Paracoccidioidomycosis in a 14-Year-Old Boy.

Paracoccidioidomycosis (PCM) is the most important systemic mycoses in Latin America. We describe a severe case of paracoccidioidomycosis in a 14-year-old boy, with a rapid disease progression. The fungal strain was isolated and inoculated into a T and/or B cell immunocompromised mice, which revealed a highly virulent strain. The case report presented herein emphasizes the importance of considering PCM in the differential diagnosis of patients with other infectious diseases in endemic areas and highlights a novel isolate.

VapB type 8 plasmids in Rhodococcus equi isolated from the small intestine of pigs and comparison of selective culture media.

UNLABELLED: The virulence-plasmid profile of Rhodococcus equi strains isolated from Suidae and humans is similar. Recent evidence suggests that the consumption of pork products contaminated with faeces might be a potential source of R. equi infections in humans, mainly to patients with rhodococcosis without history of contact with pigs or pig farms. This study investigated the virulence-associated genes (vapA and vapB) and plasmid profiles of R. equi among the 150 samples of small intestinal content obtained from slaughtered pigs. In addition, all samples were subjected to microbiological culture in conventional sheep blood agar and CAZ-NB, TCP and TVP selective media. A total of 40 (26·7%) of the samples recovered R. equi, with two samples recovering isolates harbouring the VapB type 8 plasmid. Among the 150 pigs sampled herein, CAZ-NB was considered the best selective medium for the isolation of R. equi from faeces. Our results provide evidence that the contamination of slaughtered pig carcasses with pathogenic R. equi might occur through faeces, representing a public health concern. Furthermore, this study is the first description of R. equi strains carrying the VapB plasmid in the gut of pigs. SIGNIFICANCE AND IMPACT OF THE STUDY: Intermediately virulent (VapB) is a common plasmid-type harboured by R. equi isolated from pigs and humans with AIDS. Curiously, humans with rhodococcosis usually have no history of contact with pigs or pig farms. Virulence-plasmid profile of 40 R. equi isolated among 150 small intestine content samples from pigs revelled two carrying isolates with the VapB type-8 plasmids. Moreover, comparison of three selective culture media shows that CAZ-NB was the best. Our results provide evidence that contamination of slaughtered pig carcasses with pathogenic R. equi might occur through faeces, representing a public health concern. Furthermore, R. equi carrying VapB type-8 plasmids types are described for the first time in the gut of the pig.

Molecular and phylogenetic characterization based on the complete genome of a virulent pathotype of Newcastle disease virus isolated in the 1970s in Brazil.

Newcastle disease (ND) is caused by the avian paramyxovirus type 1 (APMV-1) or Newcastle disease virus (NDV) that comprises a diverse group of viruses with a single-stranded, negative-sense RNA genome. ND is one of the most important diseases of chickens, because it severely affects poultry production worldwide. In the 1970s, outbreaks of virulent ND were recorded in Brazil, and the strain APMV-1/Chicken/Brazil/SJM/75 (SJM) of NDV was isolated. This strain was characterized as highly pathogenic for chickens but not pathogenic for other bird species. Here we present the complete genome of NDV strain SJM and investigate the phylogenetic relationships of this virus with other NDV strains in terms of genome and proteins composition, as well as characterizing its evolution process. The NDV strain SJM is categorized as a velogenic virus and the complete genome is 15,192 nucleotides in length, consisting of six genes in the order 3'-NP-P-M-F-HN-L-5'. The presence of the major pathogenic determinant of NDV strains ((112)R-R-Q-K-R↓F(117)) was identified in the Fusion protein of the NDV strain SJM. In addition, phylogenetic analysis classified the NDV strain SJM as a member of class II, genotype V, and indicates that this virus help us in the understanding of the evolutionary process of strains belonging to this genotype. This study contributes to the growing interest involving the characterization of NDV isolates to improve our current understanding about the epidemiology, surveillance and evolution of the pathogenic strains.

Stress tolerant virulent strains of Cronobacter sakazakii from food

BACKGROUND: Cronobacter sakazakii is considered as an emerging foodborne pathogen. The aim of this study was to isolate and characterize virulent strains of Cronobacter sakazakii from food samples of Bangladesh. RESULT: Six (6) Cronobacter sakazakii was isolated and identified from 54 food samples on the basis of biochemical characteristics, sugar fermentation, SDS-PAGE of whole cell protein, plasmid profile and PCR of Cronobacter spp. specific genes (esak, gluA, zpx, ompA, ERIC, BOX-AIR) and sequencing. These strains were found to have moderately high antibiotic resistance against common antibiotics and some are ESBL producer. Most of the C. sakazakii isolates were capable of producing biofilm (strong biofilm producer), extracellular protease and siderophores, curli expression, haemolysin, haemagglutinin, mannose resistant haemagglutinin, had high cell surface hydrophobicity, significant resistance to human serum, can tolerate high concentration of salt, bile and DNase production. Most of them produced enterotoxins of different molecular weight. The isolates pose significant serological cross-reactivity with other gram negative pathogens such as serotypes of Salmonella spp., Shigella boydii, Shigella sonnei, Shigella flexneri and Vibrio cholerae. They had significant tolerance to high temperature, low pH, dryness and osmotic stress. CONCLUSION: Special attention should be given in ensuring hygiene in production and post-processing to prevent contamination of food with such stress-tolerant virulent Cronobacter sakazakii.

Characterization of a virulent Leptospira interrogans strain isolated from an abandoned swimming pool.

Pathogenic Leptospira spp. are the etiological agents of leptospirosis, an important disease of both humans and animals. In urban settings, L. interrogans serovars are the predominant cause of disease in humans. The purpose of this study was to characterize a novel Leptospira isolate recovered from an abandoned swimming pool. Molecular characterization through sequencing of the rpoB gene revealed 100% identity with L. interrogans and variable-number tandem-repeat (VNTR) analysis resulted in a banding pattern identical to L. interrogans serogroup Icterohaemorrhagiae, serovar Copenhageni or Icterohaemorrhagiae. The virulence of the strain was determined in a hamster model of lethal leptospirosis. The lethal dose 50% (LD50) was calculated to be two leptospires in female hamsters and a histopathological examination of infected animals found typical lesions associated with severe leptospirosis, including renal epithelium degeneration, hepatic karyomegaly, liver-plate disarray and lymphocyte infiltration. This highly virulent strain is now available for use in further studies, especially evaluation of vaccine candidates.

Characterization of a virulent Leptospira interrogans strain isolated from an abandoned swimming pool

Pathogenic Leptospira spp. are the etiological agents of leptospirosis, an important disease of both humans and animals. In urban settings, L. interrogans serovars are the predominant cause of disease in humans. The purpose of this study was to characterize a novel Leptospira isolate recovered from an abandoned swimming pool. Molecular characterization through sequencing of the rpoB gene revealed 100% identity with L. interrogans and variable-number tandem-repeat (VNTR) analysis resulted in a banding pattern identical to L. interrogans serogroup Icterohaemorrhagiae, serovar Copenhageni or Icterohaemorrhagiae. The virulence of the strain was determined in a hamster model of lethal leptospirosis. The lethal dose 50% (LD50) was calculated to be two leptospires in female hamsters and a histopathological examination of infected animals found typical lesions associated with severe leptospirosis, including renal epithelium degeneration, hepatic karyomegaly, liver-plate disarray and lymphocyte infiltration. This highly virulent strain is now available for use in further studies, especially evaluation of vaccine candidates.

Characterization of a virulent Leptospira interrogans strain isolated from an abandoned swimming pool

Pathogenic Leptospira spp. are the etiological agents of leptospirosis, an important disease of both humans and animals. In urban settings, L. interrogans serovars are the predominant cause of disease in humans. The purpose of this study was to characterize a novel Leptospira isolate recovered from an abandoned swimming pool. Molecular characterization through sequencing of the rpoB gene revealed 100% identity with L. interrogans and variable-number tandem-repeat (VNTR) analysis resulted in a banding pattern identical to L. interrogans serogroup Icterohaemorrhagiae, serovar Copenhageni or Icterohaemorrhagiae. The virulence of the strain was determined in a hamster model of lethal leptospirosis. The lethal dose 50% (LD50) was calculated to be two leptospires in female hamsters and a histopathological examination of infected animals found typical lesions associated with severe leptospirosis, including renal epithelium degeneration, hepatic karyomegaly, liver-plate disarray and lymphocyte infiltration. This highly virulent strain is now available for use in further studies, especially evaluation of vaccine candidates.(AU)

Partial VP1 sequencing of Brazilian infectious bursal disease virus strains

Infectious bursal disease virus (IBDV) is classified according to the antigenicity and virulence into classical virulent (cv), very virulent (vv), and antigenic variant strains. The molecular basis for the IBDV antigenic variation is well established and is associated to the capsid protein, VP2 (gene VP2 of segment A), whereas both VP2 and the RNA-dependent RNA polymerase, VP1 (gene VP1 of segment B), have been correlated with the virulence. In this study, seventeen Brazilian IBDV samples previously characterized by the VP2 gene as cv (three) and vv (fourteen) strains were genetically and molecularly analyzed for their VP1 gene. All of the strains kept with the same cv or vv classification except one sample, Br/03/DR. This sample was classified as vv by its VP2 gene, but it was most closely related to the cv strains by its VP1 partial sequence and phylogeny. Studies on the phylogeny of VP1 have suggested a possible reassortment event that originated the vvVP1. In this case, the sample carrying vvVP2 and cvVP1 could be a descendant of IBDV ancestors prior to the reassortment of vvVP1; alternatively, it could be the result of a genetic exchange between the segments of different strains or with a live attenuated vaccine. Nevertheless, this is the first report of natural genetic reassortment of IBDV in Brazil.

Partial VP1 sequencing of Brazilian infectious bursal disease virus strains.

Infectious bursal disease virus (IBDV) is classified according to the antigenicity and virulence into classical virulent (cv), very virulent (vv), and antigenic variant strains. The molecular basis for the IBDV antigenic variation is well established and is associated to the capsid protein, VP2 (gene VP2 of segment A), whereas both VP2 and the RNA-dependent RNA polymerase, VP1 (gene VP1 of segment B), have been correlated with the virulence. In this study, seventeen Brazilian IBDV samples previously characterized by the VP2 gene as cv (three) and vv (fourteen) strains were genetically and molecularly analyzed for their VP1 gene. All of the strains kept with the same cv or vv classification except one sample, Br/03/DR. This sample was classified as vv by its VP2 gene, but it was most closely related to the cv strains by its VP1 partial sequence and phylogeny. Studies on the phylogeny of VP1 have suggested a possible reassortment event that originated the vvVP1. In this case, the sample carrying vvVP2 and cvVP1 could be a descendant of IBDV ancestors prior to the reassortment of vvVP1; alternatively, it could be the result of a genetic exchange between the segments of different strains or with a live attenuated vaccine. Nevertheless, this is the first report of natural genetic reassortment of IBDV in Brazil.

Partial VP1 sequencing of Brazilian infectious bursal disease virus strains

Infectious bursal disease virus (IBDV) is classified according to the antigenicity and virulence into classical virulent (cv), very virulent (vv), and antigenic variant strains. The molecular basis for the IBDV antigenic variation is well established and is associated to the capsid protein, VP2 (gene VP2 of segment A), whereas both VP2 and the RNA-dependent RNA polymerase, VP1 (gene VP1 of segment B), have been correlated with the virulence. In this study, seventeen Brazilian IBDV samples previously characterized by the VP2 gene as cv (three) and vv (fourteen) strains were genetically and molecularly analyzed for their VP1 gene. All of the strains kept with the same cv or vv classification except one sample, Br/03/DR. This sample was classified as vv by its VP2 gene, but it was most closely related to the cv strains by its VP1 partial sequence and phylogeny. Studies on the phylogeny of VP1 have suggested a possible reassortment event that originated the vvVP1. In this case, the sample carrying vvVP2 and cvVP1 could be a descendant of IBDV ancestors prior to the reassortment of vvVP1; alternatively, it could be the result of a genetic exchange between the segments of different strains or with a live attenuated vaccine. Nevertheless, this is the first report of natural genetic reassortment of IBDV in Brazil.