A Cluster of Paralytic Poliomyelitis Cases Due to Transmission of Slightly Diverged Sabin 2 Vaccine Poliovirus.

UNLABELLED: Four cases of acute flaccid paralysis caused by slightly evolved (Sabin-like) vaccine polioviruses of serotype 2 were registered in July to August 2010 in an orphanage of Biysk (Altai Region, Russia). The Biysk cluster of vaccine-associated paralytic poliomyelitis (VAPP) had several uncommon, if not unique, features. (i) Until this outbreak, Sabin-like viruses (in distinction to more markedly evolved vaccine-derived polioviruses [VDPVs]) were reported to cause only sporadic cases of VAPP. Consequently, VAPP cases were not considered to require outbreak-type responses. However, the Biysk outbreak completely blurred the borderline between Sabin-like viruses and VDPVs in epidemiological terms. (ii) The outbreak demonstrated a very high disease/infection ratio, apparently exceeding even that reported for wild polioviruses. The viral genome structures did not provide any substantial hints as to the underlying reason(s) for such pathogenicity. (iii) The replacement of intestinal poliovirus lineages by other Sabin-like lineages during short intervals after the disease onsets was observed in two patients. Again, the sequences of the respective genomes provided no clues to explain these events. (iv) The polioviruses isolated from the patients and their contacts demonstrated a striking heterogeneity as well as rapid and uneven evolution of the whole genomes and their parts, apparently due to extensive interpersonal contacts in a relatively small closed community, multiple bottlenecking, and recombination. Altogether, the results demonstrate several new aspects of pathogenicity, epidemiology, and evolution of vaccine-related polioviruses and underscore several serious gaps in understanding these problems. IMPORTANCE: The oral poliovirus vaccine largely contributed to the nearly complete disappearance of poliovirus-caused poliomyelitis. Being generally safe, it can, in some cases, result in a paralytic disease. Two types of such outcomes are distinguished: those caused by slightly diverged (Sabin-like) viruses on the one hand and those caused by significantly diverged VDPVs on the other. This classification is based on the number of mutations in the viral genome region encoding a viral structural protein. Until now, only sporadic poliomyelitis cases due to Sabin-like polioviruses had been described, and in distinction from the VDPV-triggered outbreaks, they did not require broad-scale epidemiological responses. Here, an unusual outbreak of poliomyelitis caused by a Sabin-like virus is reported, which had an exceptionally high disease/infection ratio. This outbreak blurred the borderline between Sabin-like polioviruses and VDPVs both in pathogenicity and in the kind of responses required, as well as underscoring important gaps in understanding the pathogenicity, epidemiology, and evolution of vaccine-derived polioviruses.

Enterovirus A71 Meningoencephalitis Outbreak, Rostov-on-Don, Russia, 2013.

Seventy-eight cases of enterovirus infection, including 25 neuroinfections, occurred in Rostov-on-Don, Russia, during May-June 2013. The outbreak was caused by an enterovirus A type 71 (EV-A71) subgenotype C4 lineage that spread to neighboring countries from China ≈3 years earlier. Enterovirus associated neuroinfection may emerge in areas with a preceding background circulation of EV-A71 with apparently asymptomatic infection.

Recombination strategies and evolutionary dynamics of the Human enterovirus A global gene pool.

We analysed natural recombination in 79 Human enterovirus A strains representing 13 serotypes by sequencing of VP1, 2C and 3D genome regions. The half-life of a non-recombinant tree node in coxsackieviruses 2, 4 and 10 was only 3.5 years, and never more than 9 years. All coxsackieviruses that differed by more than 7 % of the nucleotide sequence in any genome region were recombinants relative to each other. Enterovirus 71 (EV71), on the contrary, displayed remarkable genetic stability. Three major EV71 clades were stable for 19-29 years, with a half-life of non-recombinant viruses between 13 and 18.5 years in different clades. Only five EV71 strains out of over 150 recently acquired non-structural genome regions from coxsackieviruses, while none of 80 contemporary coxsackieviruses had non-structural genes transferred from the three EV71 clades. In contrast to earlier observations, recombination between VP1 and 2C genome regions was not more frequent than between 2C and 3D regions.

Non-Polio Enteroviruses Isolated by Acute Flaccid Paralysis Surveillance Laboratories in the Russian Federation in 1998-2021: Distinct Epidemiological Features of Types.

More than 100 types of non-polio enteroviruses (NPEVs) are ubiquitous in the human population and cause a variety of symptoms ranging from very mild to meningitis and acute flaccid paralysis (AFP). Much of the information regarding diverse pathogenic properties of NPEVs comes from the surveillance of poliovirus, which also yields NPEV. The analysis of 265 NPEV isolations from 10,433 AFP cases over 24 years of surveillance and more than 2500 NPEV findings in patients without severe neurological lesions suggests that types EV-A71, E13, and E25 were significantly associated with AFP. EV-A71 was also significantly more common among AFP patients who had fever at the onset and residual paralysis compared to all AFP cases. In addition, a significant disparity was noticed between types that were common in humans (CV-A2, CVA9, EV-A71, E9, and E30) or in sewage (CVA7, E3, E7, E11, E12, and E19). Therefore, there is significant evidence of non-polio viruses being implicated in severe neurological lesions, but further multicenter studies using uniform methodology are needed for a definitive conclusion.

Detection of Polioviruses Type 2 among Migrant Children Arriving to the Russian Federation from a Country with a Registered Poliomyelitis Outbreak.

The widespread use of the oral poliovaccine from Sabin strains (tOPV) radically reduced poliomyelitis incidence worldwide. However, OPV became a source of neurovirulent vaccine-derived polioviruses (VDPVs). Currently, circulating type 2 VDPVs (cVDPV2) are the leading cause of poliomyelitis. The novel OPV type 2 vaccine (nOPV2), based on genetically modified Sabin strain with increased genetic stability and reduced risk of cVDPV formation, has been used to combat cVDPV2 outbreaks, including one in Tajikistan in 2021. In order to identify the importation of cVDPV2 and nOPV2-derivates, stool samples from 12,127 healthy migrant children under 5 years of age arriving from Tajikistan were examined in Russia (March 2021-April 2022). Viruses were isolated in cell culture and identified via intratype differentiation RT-PCR, VP1 and whole-genome sequencing. cVDPV2 isolates closely related with the Tajikistan one were isolated from two children, and nOPV2-derived viruses were detected in specimens from 106 children from 37 regions of Russia. The duration of nOPV2 excretion ranged from 24 to 124 days post-vaccination. nOPV2 isolates contained 27 mutations per genome (0.36%) on average, with no critical genetic changes, which confirms the genetic stability of nOPV2 during field use. The possibility of epidemiologically significant poliovirus introduction into polio-free countries has been confirmed. The screening of special populations, including migrants, is required to maintain epidemiological well-being.

Ligilactobacillus salivarius 7247 Strain: Probiotic Properties and Anti-Salmonella Effect with Prebiotics.

The Ligilactobacillus salivarius 7247 (LS7247) strain, originally isolated from a healthy woman's intestines and reproductive system, has been studied for its probiotic potential, particularly against Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST) as well as its potential use in synbiotics. LS7247 showed high tolerance to gastric and intestinal stress and effectively adhered to human and animal enterocyte monolayers, essential for realizing its probiotic properties. LS7247 showed high anti-Salmonella activity. Additionally, the cell-free culture supernatant (CFS) of LS7247 exhibited anti-Salmonella activity, with a partial reduction upon neutralization with NaOH (p < 0.05), suggesting the presence of anti-Salmonella factors such as lactic acid (LA) and bacteriocins. LS7247 produced a high concentration of LA, reaching 124.0 ± 2.5 mM after 48 h of cultivation. Unique gene clusters in the genome of LS7247 contribute to the production of Enterolysin A and metalloendopeptidase. Notably, LS7247 carries a plasmid with a gene cluster identical to human intestinal strain L. salivarius UCC118, responsible for class IIb bacteriocin synthesis, and a gene cluster identical to porcine strain L. salivarius P1ACE3, responsible for nisin S synthesis. Co-cultivation of LS7247 with SE and ST pathogens reduced their viability by 1.0-1.5 log, attributed to cell wall damage and ATP leakage caused by the CFS. For the first time, the CFS of LS7247 has been shown to inhibit adhesion of SE and ST to human and animal enterocytes (p < 0.01). The combination of Actigen prebiotic and the CFS of LS7247 demonstrated a significant combined effect in inhibiting the adhesion of SE and ST to human and animal enterocytes (p < 0.001). These findings highlight the potential of using the LS7247 as a preventive strategy and employing probiotics and synbiotics to combat the prevalence of salmonellosis in animals and humans caused by multidrug resistant (MDR) strains of SE and ST pathogens.

Anti-Salmonella Defence and Intestinal Homeostatic Maintenance In Vitro of a Consortium Containing Limosilactobacillus fermentum 3872 and Ligilactobacillus salivarius 7247 Strains in Human, Porcine, and Chicken Enterocytes.

Limosilactobacillus fermentum strain 3872 (LF3872) was originally isolated from the breast milk of a healthy woman during lactation and the breastfeeding of a child. Ligilactobacillus salivarius strain 7247 (LS7247) was isolated at the same time from the intestines and reproductive system of a healthy woman. The genomes of these strains contain genes responsible for the production of peptidoglycan-degrading enzymes and factors that increase the permeability of the outer membrane of Gram-negative pathogens. In this work, the anti-Salmonella and intestinal homeostatic features of the LF3872 and LS7247 consortium were studied. A multi-drug resistant (MDR) strain of Salmonella enteritidis (SE) was used in the experiments. The consortium effectively inhibited the adhesion of SE to intact and activated human, porcine, and chicken enterocytes and reduced invasion. The consortium had a bactericidal effect on SE in 6 h of co-culturing. A gene expression analysis of SE showed that the cell-free supernatant (CFS) of the consortium inhibited the expression of virulence genes critical for the colonization of human and animal enterocytes. The CFS stimulated the production of an intestinal homeostatic factor-intestinal alkaline phosphatase (IAP)-in Caco-2 and HT-29 enterocytes. The consortium decreased the production of pro-inflammatory cytokines IL-8, TNF-α, and IL-1ß, and TLR4 mRNA expression in human and animal enterocytes. It stimulated the expression of TLR9 in human and porcine enterocytes and stimulated the expression of TLR21 in chicken enterocytes. The consortium also protected the intestinal barrier functions through the increase of transepithelial electrical resistance (TEER) and the inhibition of paracellular permeability in the monolayers of human and animal enterocytes. The results obtained suggest that a LF3872 and LS7247 consortium can be used as an innovative feed additive to reduce the spread of MDR SE among the population and farm animals.

Adenovirus isolation rates in acute flaccid paralysis patients.

Adenoviruses usually cause asymptomatic or mild infection, but occasionally they produce various severe syndromes including neurological disorders. Association of adenovirus infection with acute flaccid paralysis has been investigated. Shedding of adenovirus with feces was detected in 1.05% of young children (mostly infants) with acute flaccid paralysis syndrome versus 0.42% in healthy contact children (P < 0.01). However, 85% of adenoviruses in the pediatric AFP patients belonged to HAdV-C species, which does not have a known neuropathogenic potential. Also, 40% of adenoviruses were isolated from patients with consequently established diagnosis of traumatic neuritis at the discharge, which was not compatible with virus ethology of neurological lesions. Higher adenovirus prevalence in young neurological patients could be affected by an underlying immune deficiency or by congestion in children's hospitals. Indeed, among 70 patients (40 infants, 30 adults) with primary immune deficiencies, asymptomatic shedding of adenoviruses was found in 10-17%; in one adult patient a mixture of HAdV-C2 and HAdV-D15 persisted for several months. Adenoviruses also could be detected in feces of 12% and 57% of healthy young children from two orphanages, respectively. A significant fraction of samples in these groups contained adenovirus mixtures. Therefore, immune deficiencies and congested groups in children's facilities (orphanages and hospitals) could affect significantly the prevalence of adenovirus shedding. The role of adenoviruses in AFP requires further study.

Antimicrobial resistance of commensal Enterococcus faecalis and Enterococcus faecium from food-producing animals in Russia.

Background and Aim: Although Enterococcus faecalis and Enterococcus faecium are common members of human and animal gut microbiota, their resistance to different antimicrobials makes them important pathogens. Multidrug-resistant enterococci often contaminate foods of animal origin at slaughterhouses. The World Health Organization and the World Organization for Animal Health recommend including animal-derived enterococci in antimicrobial resistance (AMR) monitoring programs. This study aimed to fill a literature gap by determining the current AMR prevalence of E. faecalis and E. faecium from different food-producing animals in Russia. Materials and Methods: Samples of biomaterial were taken from chickens (n=187), cattle (n=155), pigs (n=49), turkeys (n=34), sheep (n=31), and ducks (n=31) raised at 28 farms in 15 regions of Russia. Isolates of E. faecalis (n=277) and of E. faecium (n=210) (487 isolates in total; 1 isolate per sample) were tested for resistance to 12 antimicrobials from 11 classes using the broth microdilution method. Three criteria were used for the interpretation of minimum inhibitory concentration: Epidemiological cutoff values (ECOFFs) from the European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical and Laboratory Standards Institute (CLSI) clinical breakpoints. The AMR cloud online platform was used for data processing and statistical analysis. Results: A difference of >10% was found between E. faecalis and E. faecium resistance to several antimicrobials (erythromycin, gentamycin, tetracycline, chloramphenicol, ciprofloxacin, and streptomycin). In total, resistance to most antimicrobials for enterococci isolates of both species taken from turkeys, chicken, and pigs was higher than cattle, sheep, and ducks. The highest levels were found for turkeys and the lowest for ducks. Among antimicrobials, resistance to bacitracin and virginiamycin was 88-100% in nearly all cases. High levels of clinical resistance were found for both bacteria species: Rifampicin (44-84%) from all animals, tetracycline (45-100%) from poultry and pigs, and erythromycin (60-100%), ciprofloxacin (23-100%), and trimethoprim-sulfamethoxazole (33-53%) from chickens, turkeys, and pigs. No vancomycin-resistant isolates were found. Most isolates were simultaneously resistant to one-three classes of antimicrobials, and they were rarely resistant to more than three antimicrobials or sensitive to all classes. Conclusion: Differences in resistance between enterococci from different farm animals indicate that antimicrobial application is among the crucial factors determining the level of resistance. Conversely, resistance to rifampicin, erythromycin, tetracycline, and ciprofloxacin found in enterococci from farm animals in our study was notably also found in enterococci from wild animals and birds. Our results may be partly explained by the intrinsic resistance of E. faecium and E. faecalis to some antimicrobials, such as trimethoprim/sulfamethoxazole and bacitracin.

Vaccine-associated paralytic poliomyelitis in a child: fast transformation from Sabin-like virus to vaccine-derived poliovirus triggered an epidemiological response in two countries of the European region.

OBJECTIVES: The detection of a vaccine-derived poliovirus (VDPV) requires an epidemiological assessment and response. Using repeated stool sampling from a child who is immunocompetent and was vaccinated against poliomyelitis with acute flaccid paralysis, a case of an extremely rapid evolution of Sabin-like poliovirus (PV) type 3 was traced in the child's body. METHODS: The case was independently identified in two countries-Tajikistan and Russia. Stool samples for the study were also independently collected in two countries on different days from the onset of paralysis. Virological, serological, and molecular methods; full genome Sanger; and high-throughput sequencing were performed to characterize isolates. RESULTS: PV isolates from samples collected on days 2, 3, and 14 contained eight, seven, and seven mutations in the VP1-coding region, respectively, and were classified as Sabin-like PV type 3. The isolates from samples collected on days 15 and 18 had 11 mutations and were classified as vaccine-derived PVs, which required an epidemiological response in the two countries. CONCLUSION: The results indicate the need to continue acute flaccid paralysis surveillance, maintain high vaccination coverage, and develop and introduce new effective, genetically stable PV vaccines.

Cases of Acute Flaccid Paralysis Associated with Coxsackievirus A2: Findings of a 20-Year Surveillance in the Russian Federation.

Surveillance for acute flaccid paralysis syndrome (AFP) in children under 15 is the backbone of the Global Polio Eradication Initiative. Laboratory examination of stool samples from AFP cases allows the detection of, along with polioviruses, a variety of non-polio enteroviruses (NPEV). The etiological significance of these viruses in the occurrence of AFP cases has been definitively established only for enteroviruses A71 and D68. Enterovirus Coxsackie A2 (CVA2) is most often associated with vesicular pharyngitis and hand, foot and mouth disease. Among 7280 AFP cases registered in Russia over 20 years (2001-2020), CVA2 was isolated only from five cases. However, these included three children aged 3 to 4 years, without overt immune deficiency, immunized with 4-5 doses of poliovirus vaccine in accordance with the National Vaccination Schedule. The disease resulted in persistent residual paralysis. Clinical and laboratory data corresponded to poliomyelitis developing during poliovirus infection. These findings are compatible with CVA2 being the cause of AFP. Molecular analysis of CVA2 from these patients and a number of AFP cases in other countries did not reveal association with a specific phylogenetic group, suggesting that virus genetics is unlikely to explain the pathogenic profile. The overall results highlight the value of AFP surveillance not just for polio control but for studies of uncommon AFP agents.

Evolution of the Sabin vaccine into pathogenic derivatives without appreciable changes in antigenic properties: need for improvement of current poliovirus surveillance.

The Sabin oral polio vaccine (OPV) may evolve into pathogenic viruses, causing sporadic cases and outbreaks of poliomyelitis. Such vaccine-derived polioviruses (VDPV) generally exhibit altered antigenicity. The current paradigm to distinguish VDPV from OPV and wild polioviruses is to characterize primarily those poliovirus isolates that demonstrate deviations from OPV in antigenic and genetic intratypic differentiation (ITD) tests. Here we report on two independent cases of poliomyelitis caused by VDPVs with "Sabin-like" properties in several ITD assays. The results suggest the existence of diverse pathways of OPV evolution and necessitate improvement of poliovirus surveillance, which currently potentially misses this class of VDPV.

Mega-plasmid found worldwide confers multiple antimicrobial resistance in Salmonella Infantis of broiler origin in Russia.

Plasmids which are the mobile part of the bacterial genome can acquire and carry over genes conferring antimicrobial resistance, thus contributing to rapid adaptation of bacterial community to human-defined environment. In 2014, Israeli scientists have reported a large conjugative mega-plasmid pESI (plasmid for emerging S. Infantis) that provides multiple drug resistance (MDR) of Salmonella Infantis isolated from broilers. Later, very similar pESI-like plasmids have been found in Salmonella isolated from poultry in the United States, Italy, Switzerland, Hungary, and Japan. Here we report detection of pESI-like plasmids in Salmonella Infantis isolated from chicken food products in Russia. Whole genome sequencing of three MDR isolates revealed pESI-like plasmids in all three cases. These plasmids have such typical pESI features as a locus for siderophore yersiniabactin, a cluster of IncI1 conjugative genes, a cluster of type IV pilus genes, and three toxin-antitoxin modules. The pESI-like plasmids carry from two to five resistance genes in each isolate. In total, we observed six antimicrobial resistance genes associated with pESI-like plasmids (aadA1, blaCTX-M-14, dfrA14, sul1, tetA/tetR, tetM). Besides plasmid genes of antimicrobial resistance, all three MDR isolates of S. Infantis harbor a mutation in chromosomal gene gyrA (p.S83Y or p.D87Y) that is associated with resistance to fluoroquinolones. In addition, we performed a comparative bioinformatics meta-analysis of 25 pESI-like plasmids hosted by S. Infantis from the USA, Europe, Latin America, Israel, and Japan. This analysis identified a 173 kB sequence that is common for all pESI-like plasmids and carries virulence operons and toxin-antitoxin modules.

Antimicrobial resistance of commensal Escherichia coli from food-producing animals in Russia.

BACKGROUND AND AIM: Commensal Escherichia coli is an important indicator of antimicrobial resistance (AMR) in animals and food of animal origin. Therefore, it was recommended by the World Health Organization and OIE for inclusion in resistance surveillance programs. At the same time, the data on E. coli isolates from animals in Russia are scarce. The aim of this work was to determine the current prevalence of resistance and genetic markers of non-pathogenic commensal E. coli collected from major food-producing animals (poultry, pigs, and cows) in different regions of Russia and to compare these data with data from other countries to prioritize antimicrobials for limiting their use according to the National Action Plan. MATERIALS AND METHODS: Samples (n=306) were collected from biomaterial of chicken, turkey, cows, and pigs raised on 11 farms in the European part of Russia, Siberia, and North Caucasus. Isolates (n=306) of E. coli were tested for resistance to 11 antimicrobials from ten classes using the broth microdilution method. MICs were interpreted against EUCAST microbiological and clinical breakpoints. For data analysis and statistical processing, the AMRcloud online platform was used. The data are presented in comparison with other countries. RESULTS: In Russia, higher levels of microbiological and clinical resistance of E. coli to critically important antimicrobials, including colistin, cefotaxime, and ciprofloxacin, were found compared to other countries, especially in poultry: About 30% of isolates from chicken were resistant to colistin, 8% to cefotaxime, and 88% to ciprofloxacin according to EUCAST ECOFFs. Only 10% of isolates from cows were resistant to cefotaxime. About 47% of isolates of E. coli from chicken had a moderate relative resistance for ampicillin and 56% for tetracycline. For most antimicrobials, isolates from cows demonstrated a lower resistance than isolates from poultry and pigs. All tested isolates from chicken, turkey, and pigs showed a simultaneous microbiological resistance to at least three classes of antimicrobials. No pan-resistant isolates were found. CONCLUSION: High levels of AMR of commensal E. coli from poultry, especially for critically important drugs, are a matter of concern and should be taken into account when choosing antimicrobials to be restricted for use in animal husbandry according to the National Action Plan.

Case of Poliomyelitis Caused by Significantly Diverged Derivative of the Poliovirus Type 3 Vaccine Sabin Strain Circulating in the Orphanage.

Significantly divergent polioviruses (VDPV) derived from the oral poliovirus vaccine (OPV) from Sabin strains, like wild polioviruses, are capable of prolonged transmission and neuropathology. This is mainly shown for VDPV type 2. Here we describe a molecular-epidemiological investigation of a case of VDPV type 3 circulation leading to paralytic poliomyelitis in a child in an orphanage, where OPV has not been used. Samples of feces and blood serum from the patient and 52 contacts from the same orphanage were collected twice and investigated. The complete genome sequencing was performed for five polioviruses isolated from the patient and three contact children. The level of divergence of the genomes of the isolates corresponded to approximately 9-10 months of evolution. The presence of 61 common substitutions in all isolates indicated a common intermediate progenitor. The possibility of VDPV3 transmission from the excretor to susceptible recipients (unvaccinated against polio or vaccinated with inactivated poliovirus vaccine, IPV) with subsequent circulation in a closed children's group was demonstrated. The study of the blood sera of orphanage residents at least twice vaccinated with IPV revealed the absence of neutralizing antibodies against at least two poliovirus serotypes in almost 20% of children. Therefore, a complete rejection of OPV vaccination can lead to a critical decrease in collective immunity level. The development of new poliovirus vaccines that create mucosal immunity for the adequate replacement of OPV from Sabin strains is necessary.

Poliovirus-binding inhibition ELISA based on specific chicken egg yolk antibodies as an alternative to the neutralization test.

The first application results of enzyme immunoassay system (ELISA) - binding inhibition ELISA (BI ELISA) for the detection of antibodies to polioviruses of three types based on the use of specific antibodies from chicken yolk (IgY) are presented. This variant of ELISA is a "surrogate" neutralization test (NT). When comparing the results of the detection of antibodies in 90 sera of children who were vaccinated with oral and inactivated poliovirus vaccines, good correlation (r = 0.67, 0.61, 0.76 for types 1, 2, 3 respectively) between the BI ELISA and the NT results was shown. The presented variant of ELISA is the further stage of the development of "IgY-technology" for laboratory diagnostics of viral infections, namely poliovirus infection, which can be used for seroepidemiological studies as an analogue of the NT which requires the use of life poliovirus with the required standard of biosafety containment facilities.

Environmental Surveillance for Poliovirus and Other Enteroviruses: Long-Term Experience in Moscow, Russian Federation, 2004⁻2017.

Polio and enterovirus surveillance may include a number of approaches, including incidence-based observation, a sentinel physician system, environmental monitoring and acute flaccid paralysis (AFP) surveillance. The relative value of these methods is widely debated. Here we summarized the results of 14 years of environmental surveillance at four sewage treatment plants of various capacities in Moscow, Russia. A total of 5450 samples were screened, yielding 1089 (20.0%) positive samples. There were 1168 viruses isolated including types 1-3 polioviruses (43%) and 29 different types of non-polio enteroviruses (51%). Despite using the same methodology, a significant variation in detection rates was observed between the treatment plants and within the same facility over time. The number of poliovirus isolates obtained from sewage was roughly 60 times higher than from AFP surveillance over the same time frame. All except one poliovirus isolate were Sabin-like polioviruses. The one isolate was vaccine-derived poliovirus type 2 with 17.6% difference from the corresponding Sabin strain, suggesting long-term circulation outside the scope of the surveillance. For some non-polio enterovirus types (e.g., Echovirus 6) there was a good correlation between detection in sewage and incidence of clinical cases in a given year, while other types (e.g., Echovirus 30) could cause large outbreaks and be almost absent in sewage samples. Therefore, sewage monitoring can be an important part of enterovirus surveillance, but cannot substitute other approaches.

Analysis of echovirus 30 isolates from Russia and new independent states revealing frequent recombination and reemergence of ancient lineages.

We studied two genome regions, VP1 and 3D, of 48 echovirus 30 (E30) isolates from Russia and the new independent states. In VP1, most isolates were similar to European strains reported earlier, and frequent change of circulating subgroups was noticed. We also observed, in 2003-2006, the reemergence of a group of E30 strains with a VP1 region very distant from most modern E30 strains and remotely similar to E30 isolates from the 1960s and the 1970s. A study of the 3D genome region detected multiple recombination events among the studied strains. Recombination presumably occurred every few years, and therefore, the study of a single VP1 genome region cannot accurately describe the phylogenetic history of the virus or predict pathogenetic properties of an isolate. In general, a comparison of the VP1 and 3D genome region phylogenies revealed, in some instances, virtually independent circulation of enterovirus genome fragments on a scale of years.

Vaccine-associated paralytic poliomyelitis in the Russian Federation in 1998-2014.

OBJECTIVES: Different polio vaccination schemes have been used in Russia: oral polio vaccine (OPV) was used in 1998-2007 and inactivated polio vaccine (IPV) followed by OPV in 2008-2014. This article presents the characteristics of vaccine-associated paralytic poliomyelitis (VAPP) cases in Russia during this period. METHODS: VAPP cases were identified through the acute flaccid paralysis surveillance system, classified by the National Expert Classification Committee. Criteria for a 'recipient VAPP' (rVAPP) case were poliomyelitis symptoms 6-30days after OPV administration, isolation of the vaccine virus, and residual paralysis 60days after disease onset. Unvaccinated cases with a similar picture 6-60days after contact with an OPV recipient were classified as 'contact VAPP' (cVAPP) cases. RESULTS: During 1998-2014, 127 VAPP cases were registered: 82 rVAPP and 45 cVAPP. During the period in which only OPV was used, rVAPP cases prevailed (73.8%); cases of rVAPP were reduced during the sequential scheme period (15%). Poliovirus type 3 (39.5%) and type 2 (23.7%) were isolated more often. Vaccine-derived poliovirus types 1, 2, and 3 were isolated from three cases of cVAPP. The incidence of VAPP cases was higher during the period of OPV use (1 case/1.59 million OPV doses) than during the sequential scheme period (1 case/4.18 million doses). CONCLUSION: The risk of VAPP exists if OPV remains in the vaccination schedule.

Pressure for Pattern-Specific Intertypic Recombination between Sabin Polioviruses: Evolutionary Implications.

Complete genomic sequences of a non-redundant set of 70 recombinants between three serotypes of attenuated Sabin polioviruses as well as location (based on partial sequencing) of crossover sites of 28 additional recombinants were determined and compared with the previously published data. It is demonstrated that the genomes of Sabin viruses contain distinct strain-specific segments that are eliminated by recombination. The presumed low fitness of these segments could be linked to mutations acquired upon derivation of the vaccine strains and/or may have been present in wild-type parents of Sabin viruses. These "weak" segments contribute to the propensity of these viruses to recombine with each other and with other enteroviruses as well as determine the choice of crossover sites. The knowledge of location of such segments opens additional possibilities for the design of more genetically stable and/or more attenuated variants, i.e., candidates for new oral polio vaccines. The results also suggest that the genome of wild polioviruses, and, by generalization, of other RNA viruses, may harbor hidden low-fitness segments that can be readily eliminated only by recombination.