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Non-typhoidal Salmonella(NTS) is an important cause of acute gastroenteritis in children. The study was undertaken to determine the isolation rate, serovar prevalence, antimicrobial resistance (AMR) profiles, and molecular subtypes of NTS from a hospital-based diarrheal disease surveillance in Kolkata, India. Rectal swabs were collected from children (< 5 years of age) with acute gastroenteritis from 2000 to 2016. Samples were processed following standard procedures for identification of NTS. The isolates were tested for antimicrobial susceptibility, AMR genes, plasmid profiles, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE) subtypes. A total of 99 (1.0%) Salmonellaisolates were recovered from 9957 samples processed. Of the 17 Salmonellaserovars identified, S. Worthington (33%) was predominant followed by S. Enteritidis (13%), S. Typhimurium (12%), and others. The isolates showed high resistance towards nalidixic acid (43%), ampicillin (34%), third-generation cephalosporins (32%), and azithromycin (25%), while low resistance was observed for fluoroquinolones (2%). Extended-spectrum beta-lactamase production (blaCTX-M-15and blaSHV-12genes) and azithromycin resistance (mphAgene) were common in S. Worthington, while fluoroquinolone resistance (gyrAand parCmutations) was found in S. Kentucky. Diverse plasmid profiles were observed among the isolates. PFGE analysis identified genetically related strains of each serovar in circulation. MLST also revealed phylogenetically clonal isolates of which S. Worthington ST592 and ciprofloxacin-resistant S. Kentucky ST198 were not reported earlier from India. NTS resistant to current drugs of choice poses a potential public health problem. Continuous monitoring of AMR profiles and molecular subtypes of NTS serovars is recommended for controlling the spread of resistant organisms.

Multiple structure alignment (MStA) is a fundamental tool for correlating the structural similarity of proteins with their functional similarity. A number of algorithms are extant, MUSTANG, POSA, MultiProt, CE-MC to name a few. In this paper we propose a new algorithm, MASCOT. This uses the DSSP program to map a protein structure into a DSSP-sequence, reducing the structural alignment problem to a sequence alignment problem. We have used a center-star approach to select a center-protein with respect to which to create an alignment. The root mean square deviation (RMSD) has been used to measure alignment quality for a large variety of datasets. We compared the execution times of our algorithm with the well-known algorithm MUSTANG for all the tested alignments. MASCOT outperformed MUSTANG on all but one sample. Another measure (Alignment Accuracy), was used to compare the performance of MASCOT and MUSTANG for protein structures drawn from the manually curated database HOMSTRAD.

Aims: The Quantum-dot Cellular Automata explores a unique perspective in the arena of the architectural design of future quantum computers, precisely due to its ultra-low packing density, high operating speed, and low power dissipation. On the other side, reversible computing allows the implementation of extreme low power-consuming circuits by avoiding energy dissipation during the time of computation. Objective: In this paper, we have explored the QCA design of reversible binary to gray and gray to binary code converters based on the application of a unique model of Feynman gate using the layered T exclusive-OR module (abbreviated in this work as LTEx Feynman gate). Methods: We have proposed algorithms to produce multi-control reversible binary to gray and gray to binary code converters and to develop cost-efficient QCA layouts. Results: Our systematic literature survey on the existing QCA designs of reversible binary to gray and gray to binary code converters helped us to compare and analyze the proposed design with the existing ones and identify it as the best design in terms of reversible, and QCA design metrics. Conclusion: Significant improvements in design metrics owing to successful experimentations over the previous designs are reported while instantiating 3X3,4X4, and 8X8 counterpart layouts.

Background: The advancement of VLSI in the application of emerging nanotechnology explores quantum-dot cellular automata (QCA) which has got wide acceptance owing to its ultra-high operating speed, extremely low power dissipation with a considerable reduction in feature size. The QCA architectures are emerging as a potential alternative to the conventional complementary metal oxide semiconductor (CMOS) technology. Experimental: Since the register unit has a crucial role in digital data transfer between the electronic devices, such study leading to the design of cost-efficient and highly reliable QCA register is expected to be a prudent area of research. A thorough survey on the existing literature shows that the generic models of Serial-in Serial Out (SISO), Serial-in-Parallel-Out (SIPO), Parallel-In- Serial-Out (PISO) and Parallel-in-Parallel-Out (PIPO) registers are inadequate in terms of design parameters like effective area, delay, O-Cost, Costα, etc. Results: This work introduces a layered T gate for the design of the D flip flop (LTD unit), which can be broadly used in SISO, SIPO, PISO, and PIPO register designs. For detection and reporting of high susceptible errors and defects at the nanoscale, the reliability and defect tolerant analysis of LTD unit are also carried out in this work. The QCA design metrics for the general register layouts using LTD unit is modeled. Conclusion: Moreover, the cost metrics for the proposed LTD layouts are thoroughly studied to check the functional complexity, fabrication difficulty and irreversible power dissipation of QCA register layouts.

Background: In this article, photonic extinction performance of Metal Dielectric Semiconductor (MDS) nanostructure has been improved by noble metallic nanosphere such as gold, silver and copper into various wideband dielectrics like silicon di-oxide, aluminum oxide and silicon nitride. Methods: Presently, Plasmonics gives very much interest and closely involves in the main domains of nanophotonics that can control of optical fields at the nanoscale level as well as it can concentrate and enhance the electromagnetic field on the nanometer scale especially in metal dielectric semiconductor (MDS) nanostructure. Results: In plasmonics, noble metals used as nanoparticle where density of electron gas which oscillates at surface Plasmon frequency so we investigate impact of various wideband dielectrics with nanoparticle size for enhancement of extinction in terms of absorption and scattering by using surface Plasmon resonance. Conclusion: At Plasmonic resonance the efficiency will be maximum. If the size of the metallic nanosphere increases, initially the efficiency increases up to a certain wavelength then it becomes sharply decreased.

Purpose:Helicobacter pyloricauses various gastro-intestinal diseases. Antibiotic resistance to commonly used antibiotics for the treatment of H. pyloriinfection is the major cause for treatment failure. The aim of this study is to determine the antimicrobial susceptibility pattern for clarithromycin and levofloxacin and find the evolutionary relationship of the partial sequence of 23S rRNAand gyraseAgene of H. pyloriby phylogenetic analysis. Materials and Methods:A total of 46 H. pyloristrains were tested for clarithromycin and levofloxacin susceptibility pattern and phylogenetic tree were reconstructed by PhyML software. Results:In this study, we observed that only 6.5% of North-East Indian H. pyloristrains were resistant for clarithromycin showing mutation at A2143G and T2182C positions of 23S rRNAgene. Resistance for levofloxacin was observed in 89.1% of the H. pyloristrains showing mutations at asparagine to lysine at 87 and aspartic acid to glycine/tyrosine/asparagine at 91 positions of gyraseAgene. The phylogenetic tree of the partial sequence of 23S rRNAand gyraseAgene depicts that the North-East Indian strains falls in different cluster when compared to other countries. Conclusions:Resistance for clarithromycin was less in North-East Indian strains but high for levofloxacin indicating that first-line therapy may be best and effective for eradication of H. pyloriin this region. This study is the first report that showed antibiotic susceptibility pattern for clarithromycin and levofloxacin by mutation analysis. By partial sequencing of 23s rRNAand gyraseAgene, we found that North-East Indian strains are geographically distinct.

Clostridium perfringensis one of the most important globally recognised gastroenteric pathogen in humans as well as animals. The present study was aimed to know the similarities/divergence among C. perfringenstype A isolates of human and animal origin using the pulsed-field gel electrophoresis (PFGE) as a molecular tool. The enterotoxic isolates obtained by screening of human diarrhoeal cases (n = 130), diarrhoeal cases of pig (n = 52) and goat (n = 50), meat samples viz., pork (n = 59) and chevon (n = 57) were characterized by standard cultural and biochemical methods followed by PCR Assays. Accordingly, a total of 11 C. perfringenstype A characterized isolates (16S rRNA+, cpa+, cpb2+and cpe+) recovered from human diarrhoeal cases (n = 3); diarrhoeal cases of pig (n = 2) and goat (n = 2); meat samples viz. pork (n = 2) and chevon (n = 2) were examined employing PFGE. The observed clustering pattern in PFGE analysis showed the relatedness between isolates from diarrhoeal goat and chevon (90–100%); diarrhoeal pig and pork (65–68%); moreover, isolates from human diarrhoeal cases were exhibiting lineage to cases from goat and pig diarrhoea as well pork and chevon by 62–68% relatedness. The outcome of the present study indicates the probable contamination of this pathogen to the human food chain through faeces from suspected food animals viz. goat and pig and their improperly cooked meat.

AbstractClostridium perfringensis one of the most important globally recognised gastroenteric pathogen in humans as well as animals. The present study was aimed to know the similarities/divergence among C. perfringenstype A isolates of human and animal origin using the pulsed-field gel electrophoresis (PFGE) as a molecular tool. The enterotoxic isolates obtained by screening of human diarrhoeal cases (n = 130), diarrhoeal cases of pig (n = 52) and goat (n = 50), meat samples viz., pork (n = 59) and chevon (n = 57) were characterized by standard cultural and biochemical methods followed by PCR Assays. Accordingly, a total of 11 C. perfringenstype A characterized isolates (16S rRNA+, cpa+, cpb2+and cpe+) recovered from human diarrhoeal cases (n = 3); diarrhoeal cases of pig (n = 2) and goat (n = 2); meat samples viz. pork (n = 2) and chevon (n = 2) were examined employing PFGE. The observed clustering pattern in PFGE analysis showed the relatedness between isolates from diarrhoeal goat and chevon (90–100%); diarrhoeal pig and pork (65–68%); moreover, isolates from human diarrhoeal cases were exhibiting lineage to cases from goat and pig diarrhoea as well pork and chevon by 62–68% relatedness. The outcome of the present study indicates the probable contamination of this pathogen to the human food chain through faeces from suspected food animals viz. goat and pig and their improperly cooked meat.

The quantum-dot cellular automata (QCA) which is the most promising technology in the paradigm of nano electronics has already been claimed to possess ultra-high packing density, high clocking speed and extremely low power dissipation. This work proposes a novel design of high fan-in exclusive-OR gate by using the layered T Gate of QCA. The 'robustness analysis' of layered T gate has also been done to focus the advantage of layered T architecture in generic sense considering the defects of QCA. The synthesis of 'three-literal standard functions' by using layered T gate reports an average 29.31% less area requirement as compared to the best reported design so far. Primarily two-input layered T exclusive OR shows 18.75% less cell requirement and 6.20% less area requirement as compared to the conventional two-input exclusive OR designs. Finally, two-input layered T exclusive OR module extends its design methodology to implement high fan-in exclusive OR gate designs with proper formulation of O-Cost and delay in QCA.

•High prevalence of clarithromycin-sensitive H. pyloristrains allows use of this drug.•Surveillance studies need to be done at regular intervals.•First study on the mechanism of clarithromycin resistance in India.•Mutations A2143G and A2142G are associated with clarithromycin resistance.

•More than 70% of the isolated Helicobacter pyloristrains showed resistance to at least one of the antibiotics used for treatment.•Metronidazole showed the highest prevalence of resistance.•H. pyloriisolates show least resistance to amoxicillin and clarithromycin and thus they are appropriate for anti-H. pylorimanagement in India.

AbstractStrains of the enteric pathogen Vibrio parahaemolyticusharboring the thermostable hemolysin (TDH) encoding gene tdhis known to cause epidemic and pandemic diarrhea. In industrialized countries, this pathogen causes sporadic or outbreaks of diarrheal illness associated with consumption of raw or improperly cooked seafood. This report describes a foodborne outbreak of gastroenteritis caused by V. parahaemolyticusin June 2011 following consumption of food served at a funeral reception held at Habra, North 24 Parganas, West Bengal, India. About 650 people attended the function, of whom 44 had acute watery diarrhea with other clinical symptoms; 35 of them were admitted to the District Hospital for the rehydration treatment. Stool specimens collected from three hospitalized cases were positive for V. parahaemolyticus, of which two strains were identified as an O4:K8 serovar and one was identified as O3:K6 serovar. The O3:K6 strain also possessed the pandemic group-specific toxRSgene target (GS), whereas the O4:K8 strains were negative. All strains were polymerase chain reaction–positive for tdhbut were polymerase chain reaction–negative for trh. All of the strains were resistant to ampicillin but were pansensitive to other antimicrobials tested. Pulsed-field gel electrophoresis (PFGE) analysis using NotI showed that the O3:K6 strain was similar to that of a recent clinical strain from Kolkata, but had diverged from other strains during previous years. In contrast, PFGE analysis showed that the O4:K8 strains were closely related but differed from the Kolkata strain.

ABSTRACTA PCR-based assay was developed to discriminate the classical, El Tor, and Haitian types of ctxBalleles. Our retrospective study using this newly developed PCR showed that Haitian ctxBfirst appeared in Kolkata during April 2006, and 93.3% of strains isolated during 2011 carried the new allele. Dendrogram analysis showed a pulsed-field gel electrophoresis (PFGE) pattern of the new variant strains isolated recently that was distinct from the PFGE pattern of the strains carrying classical ctxBthat closely matched the 2006 to 2007 variant strains.

The paper proposes a call admission control (CAC) scheme to offer best services to the users in the next generation heterogeneous networks. It optimises the available resources without compromising the interest of the service providers. It has combined the three commonly used CAC schemes – guard channel, buffer-based and priority-based schemes. It considers wireless overlay model for analysing the heterogeneity with detailed analysis of the WLAN-cellular mixed cell environment. The scheme considers differentiated services for the real time and non-real time calls to provide appropriate quality of service (QoS). The proposed scheme has been evaluated through simulation. The results show that the scheme outperforms some significant CAC schemes and shows even better performance under cellular-WLAN mixed environment due to the dual subscription of the users with dual mobile terminal.

ABSTRACTTreatment failure is a major cause of concern for the Helicobacter pylori-related gastroduodenal diseases like gastritis, peptic ulcer, and gastric cancer. Curcumin, diferuloylmethane from turmeric, has recently been shown to arrest H. pylorigrowth. The antibacterial activity of curcumin against 65 clinical isolates of H. pyloriin vitro and during protection against H. pyloriinfection in vivo was examined. The MIC of curcumin ranges from 5 μg/ml to 50 μg/ml, showing its effectiveness in inhibiting H. pylorigrowth in vitro irrespective of the genetic makeup of the strains. The nucleotide sequences of the aroEgenes, encoding shikimate dehydrogenase, against which curcumin seems to act as a noncompetitive inhibitor, from H. pyloristrains presenting differential curcumin MICs showed that curcumin-mediated growth inhibition of Indian H. pyloristrains may not be always dependent on the shikimate pathway. The antimicrobial effect of curcumin in H. pylori-infected C57BL/6 mice and its efficacy in reducing the gastric damage due to infection were examined histologically. Curcumin showed immense therapeutic potential against H. pyloriinfection as it was highly effective in eradication of H. pylorifrom infected mice as well as in restoration of H. pylori-induced gastric damage. This study provides novel insights into the therapeutic effect of curcumin against H. pyloriinfection, suggesting its potential as an alternative therapy, and opens the way for further studies on identification of novel antimicrobial targets of curcumin.

AbstractThis paper presents techniques adopted to defend against Sybil Attack in Mobile Ad Hoc Networks. Sybil attack and the existing defense mechanisms against this type of attack have been reviewed and their loopholes are indicated. Multifactor Authentication Scheme has been discussed pointing out its superiority over traditional Cryptography-based Authentication Schemes. Afterwards, Passive Ad Hoc Sybil Identity Detection techniques differentiating a Sybil attacker from a group of legitimate nodes moving together is also discussed. Merits and demerits of these methods are mentioned and also the scopes for future research to improve these detection schemes have been indicated.

ABSTRACTThe molecular mechanisms of drug resistance in 19 strains of Vibrio fluvialisisolated from 1998 to 2002 in Kolkata, India, were investigated. Class 1 integrons were detected in eight strains, and four strains were found to carry SXT integrases. In the presence of carbonyl cyanide m-chlorophenylhydrazone or reserpine, all nalidixic acid- and ciprofloxacin-resistant strains became sensitive, suggesting that drug efflux plays a major role in quinolone resistance in V. fluvialis. It was further seen that strains which had MICs of >25 μg/ml for nalidixic acid had a sense mutation (Ser to Ile) at position 83 of the quinolone resistance-determining region of gyrA. All except one of the integron- and SXT integrase-bearing strains belonged to the same ribotype.

ABSTRACTWe developed and evaluated a simple, novel multiplex PCR assay for rapid detection of Helicobacter pyloriinfection and for the determination of vacAand cagAgenotypes directly from gastric biopsy specimens. This assay did not require culturing of strains or extraction of DNA from biopsy samples. This multiplex PCR assay would be of particularly great value for laboratories in developing countries.

ABSTRACTVirulence-associated genes and neutral DNA markers of Helicobacter pyloristrains from the Santhal and Oroan ethnic minorities of West Bengal, India, were studied. These people have traditionally been quite separate from other Indians and differ culturally, genetically, and linguistically from mainstream Bengalis, whose H. pyloristrains have been characterized previously. H. pyloriwas found in each of 49 study participants, although none had peptic ulcer disease, and was cultured from 31 of them. All strains carried the cagpathogenicity island and potentially toxigenic s1 alleles of vacuolating cytotoxin gene (vacA) and were resistant to at least 8 µg of metronidazole per ml. DNA sequence motifs in vacAmid-region m1 alleles, cagA, and an informative insertion or deletion motif next to cagAfrom these strains were similar to those of strains from ethnic Bengalis. Three mobile elements, IS605, IS607, and ISHp608, were present in 29, 19, and 10%, respectively, of Santhal and Oroan strains, which is similar to their prevalence in Bengali H. pylori.Thus, there is no evidence that the gene pools of H. pyloriof these ethnic minorities differ from those of Bengalis from the same region. This relatedness of strains from persons of different ethnicities bears on our understanding of H. pyloritransmission between communities and genome evolution.

ABSTRACTThe complex relation between the genotype of Helicobacter pyloriand its association with clinical outcome is not well understood. Studies in the West have showed that strains expressing certain virulence factors (vacAs1, vacAm1, and cagA) are associated with duodenal ulcer disease. However, the H. pylorigenotype is known to vary with geographic region. In the present study, we compared several virulence markers (cagA, vacA, and iceA) and neutral markers (IS605, IS606, and IS608) in H. pyloristrains isolated from 65 adult patients with peptic ulcer (PU) and 50 patients with nonulcer dyspepsia (NUD). PCR tests indicated that cagAis present in 75% of the strains from patients with PU compared to 55% in patients with NUD, and 80% of the isolates from patients with PU carried potentially toxigenic vacAs1alleles of the vacuolating cytotoxin gene (vacA) compared to 60% in isolates from patients with NUD. However, no significant difference in any other virulence marker was observed in isolates from both groups. Phylogenetic analysis of the vacAmiddle region and the 5' end of the cagAgene indicates that Bangladeshi isolates are more closely related to H. pyloriisolates from India and are different from isolates from East Asia.

ABSTRACTTetracycline is useful in combination therapies against the gastric pathogen Helicobacter pylori. We found 6 tetracycline-resistant (Tetr) strains among 159 clinical isolates (from El Salvador, Lithuania, and India) and obtained the following four results: (i) 5 of 6 Tetrisolates contained one or two nucleotide substitutions in one part of the primary tetracycline binding site in 16S rRNA (AGA965-967[Escherichia colicoordinates] changed to gGA, AGc, guA, or gGc [lowercase letters are used to represent the base changes]), whereas the sixth (isolate Ind75) retained AGA965-967; (ii) PCR products containing mutant 16S ribosomal DNA (rDNA) alleles transformed recipient strains to Tetrphenotypes, but transformants containing alleles with single substitutions (gGA and AGc) were less resistant than their Tetrparents; (iii) each of 10 Tetrmutants of reference strain 26695 (in which mutations were induced with metronidazole, a mutagenic anti-H. pyloriagent) contained the normal AGA965-967sequence; and (iv) transformant derivatives of Ind75 and of one of the Tetr26695 mutants that had acquired mutant rDNA alleles were resistant to tetracycline at levels higher than those to which either parent strain was resistant. Thus, tetracycline resistance in H. pyloriresults from an accumulation of changes that may affect tetracycline-ribosome affinity and/or other functions (perhaps porins or efflux pumps). We suggest that the rarity of tetracycline resistance among clinical isolates reflects this need for multiple mutations and perhaps also the deleterious effects of such mutations on fitness. Formally equivalent mutations with small but additive effects are postulated to contribute importantly to traits such as host specificity and virulence and to H. pylori's great genetic diversity.

ABSTRACTWe compared putative molecular markers of virulence (vacA, cagA, and iceA) of Helicobacter pyloristrains isolated from 52 adult duodenal ulcer patients from West Bengal, India, with those of H. pyloristrains isolated from 48 adult healthy volunteers from the same region. On the basis of genotyping by PCR, we conclude that the H. pyloristrains isolated from the two study groups were indistinguishable and that there are geographic variations in the association of certain putative H. pylorivirulence genes with clinical status.

ABSTRACTNitazoxanide (NTZ) is a redox-active nitrothiazolyl-salicylamide prodrug that kills Helicobacter pyloriand also many anaerobic bacterial, protozoan, and helminthic species. Here we describe development and use of a spectrophotometric assay, based on nitroreduction of NTZ at 412 nm, to identify H. pylorienzymes responsible for its activation and mode of action. Three enzymes that reduce NTZ were identified: two related NADPH nitroreductases, which also mediate susceptibility to metronidazole (MTZ) (RdxA and FrxA), and pyruvate oxidoreductase (POR). Recombinant His-tagged RdxA, FrxA, and POR, overexpressed in nitroreductase-deficient Escherichia coli, each rapidly reduced NTZ, whereas only FrxA and to a lesser extent POR reduced nitrofuran substrates (furazolidone, nitrofurantoin, and nitrofurazone). POR exhibited no MTZ reductase activity either in extracts of H. pylorior following overexpression in E. coli; RdxA exhibited no nitrofuran reductase activity, and FrxA exhibited no MTZ reductase activity. Analysis of mutation to rifampin resistance (Rifr) indicated that NTZ was not mutagenic and that nitrofurans were only weakly mutagenic. Alkaline gel DNA electrophoresis indicated that none of these prodrugs caused DNA breakage. In contrast, MTZ caused DNA damage and was strongly mutagenic. We conclude that POR, an essential enzyme, is responsible for most or all of the bactericidal effects of NTZ against H. pylori. While loss-of-function mutations in rdxAand frxAproduce a Mtzrphenotype, they do not contribute much to the innate susceptibility of H. pylorito NTZ or nitrofurans.

ABSTRACTCulture supernatants of nontoxigenic nonepidemic clinical strains of Vibrio choleraebelonging to diverse serogroups were found to induce vacuolation of nonconfluent HeLa cells. The vacuoles became prominent 18 h after introduction of culture supernatant, and vacuolated cells survived for 48 h and then died. Only a fraction of the vacuolated cells took up neutral red dye, implying that there were differences in the vacuolar microenvironment. Further tests showed that the factor responsible for vacuolation was heat labile and proteinaceous. Vacuolating activity was completely neutralized by antibody to hemolysin of V. choleraebut not by antibody to vacuolating cytotoxin of Helicobacter pylori. Partial purification of the vacuolating factor led to elution of fractions, which showed both hemolytic and vacuolating activity. PCR amplification and cloning of the hemolysin structural gene (hlyA) intoEscherichia coliDH5α led to isolation of clones producing cell vacuolating factor in a cell-associated form. Further, a null insertion mutation in the hlyAgene of a high-vacuolating-factor-producing strain led to complete abolition of both cell vacuolating and hemolytic activities. These analyses establish vacuolation as a potentially important but previously unrecognized property of V. choleraeEl Tor hemolysin.

This study reports the results of a molecular analysis of the CTX prophages in classical biotype strains of Vibrio choleraeO1 of clinical origin isolated between 1970 and 1979 in India. All strains were sensitive to group IV classical phage and polymyxin B but resistant to group 5 El Tor phage. These phenotypic traits are consistent to that exhibited by the classical biotype. PCR studies reconfirmed their biotype assignment and showed the presence of intact CTX prophages and the presence of the recently described toxin linked cryptic plasmid. Restriction fragment length polymorphism of rRNA genes and pulsed‐field gel electrophoresis showed clonal diversity among the strains. The most notable observation was the finding that one strain (GP13) has three CTX prophages while another (GP147) has four CTX prophages. This is the first time heterogeneity is reported in the arrangement of the CTX prophages among classical strains of V. choleraeO1.

A multiplex polymerase chain reaction assay was developed for concurrent detection of rfbsequences specific for the O1 and the O139 serogroups of Vibrio choleraeand for ctxAspecific sequences. The multiplex PCR assay was found to be highly specific and sensitive and was capable of detecting 65 cfu and 200 cfu per assay of V. choleraeO1 and O139, respectively. Evaluation of the multiplex PCR assay using 121 stool samples from patients admitted to the Infectious Diseases Hospital, Calcutta, showed the assay to be 100% sensitive and 95.2% specific when the culture method was taken as the standard. In addition to the 38 PCR positive stool samples, an additional four samples which were negative by culture method but positive by PCR assay belonged to the O139 serogroup. All the 38 stool samples positive for either O1 or O139 serogroup by PCR assay were also positive for the ctxAamplicon indicating that the O1 and O139 V. choleraestrains have the genetic potential of producing cholera toxin.

Stereospecific total syntheses of (±)-2-desoxystemodinone, (+)-2-desoxystemodinone, and (±)-stemodinol are described. Also described are the isolation of (+)-2-desoxystemodinone from S. maritimaand its characterization. A strategy for the elaboration of the C/D ring systems of the stemodane diterpenoids, stemarin and aphidicolin, from a common 6-hydroxybicyclo[2.2.2]octan-2-one system is delineated and its efficacy is demonstrated by the synthesis of the stemodane diterpenoids and our previous synthesis of stemarin.

The intersection radius of a finite collection of geometrical objects in the plane is the radius of the smallest closed disk that intersects all the objects in the collection. Bhattacharyaet al.showed how the intersection radius can be found in linear time for a collection of line segments in the plane by combining the prune-and-search strategy of Megiddo (J. Assoc. Comput. Mach.31(1) (1984), 114–127) with the strategy of replacing line segments by lines or points (B. K. Bhattacharya, S. Jadhav, A. Mukhopadhyay, and J. M. Robert,in“Proceedings of the Seventh Annual ACM Symposium on Computational Geometry,” pp. 81–88, 1991). In this paper, we enlarge the scope of this technique by showing that it can also be used to find the intersection radius of a collection of convex polygons inO(n) time, wherenis the total number of polygon vertices.

ABSTRACTThere was an inexplicable upsurge in the incidence of non-O1, non-O139 Vibrio choleraeamong hospitalized patients admitted to the Infectious Diseases Hospital, Calcutta, India, between February and March 1996. Of the 18 strains of V. choleraeisolated during this period, 15 belonged to the non-O1, non-O139 serogroups (4 belonged to O144, 3 belonged to O11, 1 each belonged to O6, O8, O12, O19, O39, and O58, and 2 strains could not be typed), 2 belonged to the O139 serogroup, and 1 belonged to the O1 serogroup. Cell-free culture supernatants of 13 representative non-O1, non-O139 V. choleraestrains evoked a distinct cytotoxic effect on CHO and HeLa cells, and the strains examined produced the nonmembrane-damaging cytotoxin. By several PCR assays, it was determined that none of the non-O1, non-O139 strains were positive for the ctxA, zot, ace, andtcpAgenes and for the genes representing the heat-labile toxin, heat-stable toxin, and verotoxin of Escherichia coliand the various variants of these genes. Studies on the clonality of non-O1, non-O139 V. choleraestrains by restriction fragment length polymorphism (RFLP) analysis of rRNA genes and of other genes (hlyA, hlyU,hlx, toxR, and attRS1) and by pulsed-field gel electrophoresis (PFGE) collectively indicate that the upsurge which occurred in February and March 1996 was caused by strains belonging to different clones. Overall, there was an excellent correlation between the results of ribotyping, RFLP analysis of various genes, and PFGE, with strains belonging to a particular serogroup showing nearly identical restriction patterns and PFGE profiles. It is clear from this study that some serogroups of V. choleraecan cause diarrhea by a mechanism quite different from that of toxigenic V. choleraeO1 and O139, and we have proposed the nomenclature of enteropathogenic V. choleraeto include these serogroups.

After a lapse of 33 months,Vibrio choleraeO139, the new serogroup associated with cholera, has re-emerged in Calcutta, India and has become the dominant serogroup causing cholera from September 1996. In neighbouring Bangladesh,V. choleraeO1 biotype El Tor continues to be the dominant cause of cholera with the O139 serogroup accounting for only a small proportion of cases. Comparison of the phenotypic traits of representative O139 strains from Calcutta and Dhaka isolated between December 1996 and April 1997 showed similar phenotypic traits with the exception that Dhaka O139 strains were susceptible to streptomycin whilst Calcutta O139 strains were resistant. The Dhaka and Calcutta O139 strains displayed identical ribotypes but showed remarkable differences in the structure and organization of the CTX genetic element. In the Dhaka O139 strains, two copies of the CTX element were arranged in tandem and this resembled the pattern displayed by the 1992 epidemic strains of O139. The Calcutta O139 strains, in contrast, carried three copies of the CTX genetic element arranged in tandem with the loss of a conservedBglII restriction site in the RS1 element and the appearance of a newHindIII site in the same region. While there may be other factors, it appears that the reorganization of the CTX genetic element in the Calcutta O139 strains may have contributed to the resurgence of this serogroup in Calcutta.

ABSTRACTWe report the prevalence of the O139 serogroup in Calcutta, India, after its reemergence in August 1996 and the spread of the reemerged clone to other parts of the country by using previously established molecular markers. Phenotypically, the reemerged Vibrio choleraeO139 displayed a difference compared to those that appeared in late 1992 and 1993 in that the current O139 strains are sensitive to co-trimoxazole. Ribotyping with the enzymeBglI produced two rRNA restriction patterns in the O139 strains isolated after August 1996, and these patterns were identical to those exhibited by strains of O139 isolated in 1992. Three clones ofV. choleraeO139 are currently prevailing in the country, with strains exhibiting three bands after HindIII digestion and hybridization with a ctxAprobe being dominant. The reemergence of V. choleraeO139 in Calcutta after a 32-month quiescent period reestablishes the O139 serogroup as an entity which is likely to play a crucial role in the temporal antigenic variations among the serogroups of V. choleraecausing cholera.

Helicobacter pylori(H. pylori) is known to cause several gastroduodenal diseases including chronic Gastritis, Peptic Ulcer disease and Gastric Cancer. Virulent genes of H. pylorilike cagA, vacAare known to be responsible for the disease pathogenesis. However, these virulence genes are not always found to be associated with disease outcome in all populations around the world. Tumor necrosis factor alpha inducing protein tipαis a newly discovered virulence gene of H. pyloriand is an inducer of certain cytokines and chemokines that are responsible for causing stomach cancer. Therefore, we conducted a study, which aims to find the prevalence of tipα gene in the Indian patients with gastroduodenal symptoms, and its association with H. pylorirelated gastroduodenal diseases. 267 clinical H. pyloriisolates are included in our study for finding the prevalence of tipαgene and its association with cagAand vacAgene using PCR assay. The current study shows that the prevalence rate of tipαgene is 59.9%. Our study has found a significant association (p< 0.05) of tipαgene with Non Ulcer Dyspepsia (NUD) and an association of cagAand vacAs1m1 with Gastritis and Duodenal Ulcer. Our study demonstrates for the first time the presence of tipαas virulence factor of H. pyloristrain in Indian population isolated from patients suffering from gastroduodenal diseases. Further, tipαis significantly associated with NUD but not with other gastroduodenal diseases in India.

Cholera continues to be a global concern, as large epidemics have occurred recently in Haiti, Yemen, and countries of sub-Saharan Africa. A single lineage of Vibrio choleraeO1 has been considered to be introduced into these regions from South Asia and to cause the spread of cholera. Using genomic epidemiology, we showed that two distinct lineages exist in Bengal, one of which is linked to the global lineage. The other lineage was found only in Iran, Iraq, and countries in Asia and differed from the global lineage regarding cholera toxin variant and drug resistance profile. Therefore, the potential transmission of this lineage to other regions would likely cause worldwide cholera spread and may result in this lineage replacing the current global lineage.

AbstractSalmonella entericaserovar Weltevreden and Vibrio fluvialiswere identified as etiological agents of a foodborne gastroenteritis outbreak after an Iftar feast in North Dumdum. Of the 278 cases admitted to the Infectious Diseases Hospital, Kolkata, 44 stool samples were tested for the enteric pathogens. Six were positive for SalmonellaWeltevreden, 5 for Vibrio fluvialis, and 8 contained both of the pathogens. Consumption of mutton-ghogni might have been the likely vehicle of this outbreak. In the pulsed-field gel electrophoresis, SalmonellaWeltevreden was identified as a single clone but the V. fluvialisstrains were heterogeneous.

Antimicrobial peptides play an important role in host defense against Vibrio cholerae. Generally, the V. choleraeO1 classical biotype is polymyxin B (PB) sensitive and El Tor is relatively resistant. Detection of classical biotype traits like the production of classical cholera toxin and PB sensitivity in El Tor strains has been reported in recent years, including in the devastating Yemen cholera outbreak during 2016-2018. To investigate the factor(s) responsible for the shift in the trend of sensitivity to PB, we studied the two-component system encoded by carRS, regulating the lipid A modification of El Tor vibrios, and found that only carRcontains a single nucleotide polymorphism (SNP) in recently emerged PB-sensitive strains.

ABSTRACTAntimicrobial susceptibility of 120 Helicobacter pyloriisolates to metronidazole, tetracycline, clarithromycin, and amoxicillin was determined, and 77.5, 15, 10, and 6.6% of the isolates, respectively, were resistant. Only rdxAinactivation and both rdxAand frxAinactivation were responsible for metronidazole resistance in 66% (8 of 12) and 33% (4 of 12) of the isolates, respectively.

This study reports the results of a molecular analysis of the CTX prophages in classical biotype strains of Vibrio cholerae O1 of clinical origin isolated between 1970 and 1979 in India. All strains were sensitive to group IV classical phage and polymyxin B but resistant to group 5 El Tor phage. These phenotypic traits are consistent to that exhibited by the classical biotype. PCR studies reconfirmed their biotype assignment and showed the presence of intact CTX prophages and the presence of the recently described toxin linked cryptic plasmid. Restriction fragment length polymorphism of rRNA genes and pulsed-field gel electrophoresis showed clonal diversity among the strains. The most notable observation was the finding that one strain (GP13) has three CTX prophages while another (GP147) has four CTX prophages. This is the first time heterogeneity is reported in the arrangement of the CTX prophages among classical strains of V. cholerae O1.

A series of monoclonal antibodies of different isotypes specific for Vibrio cholerae O139, the new pandemic strain of cholera, was produced. These mAbs reacted only with the reference strain (MO45) representing serovar O139 but did not react with any of the other reference strains representing serovars O1 to O140. Significantly, the mAbs did not agglutinate the R-cultures of V. cholerae (CA385, 20–93) which demonstrated the exceptional specificity of these mAbs and indicated that the mAbs recognized antigenic determinants unique for the O139 serovar. There was heterogeneity in the intensity of reactivity of the mAbs with strains of V. cholerae O139 isolated from diverse sources. Apart from 4H6, the other mAbs agglutinated all the O139 strains examined. 2D12 and 2F8 were the best mAbs based on the intensity of agglutination with all the O139 strains. Evaluation of 3A10 in comparison with a polyclonal anti-O139 antibody raised in rabbit using the slide agglutination format revealed that 3A10 fared as well as the polyclonal antibody for the laboratory identification of the O139 serovar. The acquisition of these mAbs provide reagents which would be very useful in the development of simple immunodiagnostic assays for the diagnosis of V. cholerae O139 infections.

Vibrio cholerae serogroup O139 Bengal, a novel strain with epidemic potential, completely displaced V. cholerae serogroup 01 in Calcutta in January 1993, which was followed by an epidemic caused by V. cholerae O139 in March–May 1993. From November 1992 to July 1993, 95.6% of 916 V. cholerae isolates submitted to the National Institute of Cholera and Enteric Diseases from 28 locations in India were confirmed as serogroup O139. As of July 1993, V. cholerae O139 had been isolated from 13 Indian states and a union territory, and large outbreaks of cholera caused by the O139 serogroup had occurred in several cities. The extent of spread of V. cholerae O139 Bengal in India and its ability to swiftly disseminate leaves little doubt that this is the beginning of the eighth pandemic of cholera.

A multiplex polymerase chain reaction assay was developed for concurrent detection of rfb sequences specific for the O1 and the O139 serogroups of Vibrio cholerae and for ctxA specific sequences. The multiplex PCR assay was found to be highly specific and sensitive and was capable of detecting 65 cfu and 200 cfu per assay of V. cholerae O1 and O139, respectively. Evaluation of the multiplex PCR assay using 121 stool samples from patients admitted to the Infectious Diseases Hospital, Calcutta, showed the assay to be 100% sensitive and 95.2% specific when the culture method was taken as the standard. In addition to the 38 PCR positive stool samples, an additional four samples which were negative by culture method but positive by PCR assay belonged to the O139 serogroup. All the 38 stool samples positive for either O1 or O139 serogroup by PCR assay were also positive for the ctxA amplicon indicating that the O1 and O139 V. cholerae strains have the genetic potential of producing cholera toxin.