Bimal K. Das

Great diversity of group A rotavirus strains and high prevalence of mixed rotavirus infections in India.

ABSTRACT We previously observed a marked diversity of rotavirus strains and a high prevalence of the uncommon serotype G9 in a small survey of rotavirus strains collected from six centers in India. In the present study, we characterized a larger collection of strains from children hospitalized with severe diarrhea in seven Indian cities between 1996 and 1998. A total of 287 strains were G and P genotyped by reverse transcription-PCR, and some were further characterized by electropherotyping and subgrouping. Of the four strains common globally, three were found in only 43% of samples (P[8], G1, 15%; P[4], G2, 22%; P[8], G4, 6%), whereas G9 strains made up 17% of the total. Three different G9 strains were present: a P[8], G9 strain, which displayed the long electropherotype and subgroup II VP6 specificity, and two P[6], G9 strains, one with the long electropherotype and subgroup II specificity and the other with the short electropherotype and subgroup I specificity. Marked diversity was observed among strains collected from different cities and collected over time. Of the 253 strains that were fully typed, 54 (21%) had a mixed G or P genotype. Serotype G2 strains were detected more often in infections caused by single strains than in mixed infections (P < 0.05), whereas serotype G1 strains were found more often in mixed infections than in infections caused by single strains (P < 0.05). The diversity of rotavirus strains and the high prevalence of mixed infections confirm trends reported earlier and help to better characterize the strains of rotavirus circulating in India. Vaccines under development should clearly target G9 strains, and G9 should be included as one of the common global serotypes.

Sequence analysis of NSP4 gene of human rotavirus allows classification into two main genetic groups

The rotavirus nonstructural glycoprotein NSP4 may represent the first identified viral enterotoxin. We have sequenced reverse transcription‐polymerase chain reaction (RT‐PCR)‐generated fragments of 16 NSP4 genes of human rotavirus (HRV) strains from six different countries, representing seven different G and P type combinations. Based on the amount of sequence divergence between these and 11 previously sequenced NSP4 genes of human and animal rotaviruses, three distinct genetic groups could be recognized. Most strains within a group were closely related to each other at the nucleotide (nt) and amino acid (aa) levels (usually <10% divergence) but more distantly related (maximum 30.0% nt divergence and 24.7% aa divergence) to members of the other groups. Intergroup variation occurred in two highly variable regions of NSP4 (aa 16–34 and aa 131–148). The NSP4 “toxic peptide” (aa 114–135) exhibited aa variation at its carboxy terminus both within and between genetic groups. The largest group (genetic group II) contained HRV strains of subgroup II specificity (including genotypes P[8]G1, P[8]G3, P[6]G3, and P[8]G5 and serotype P8[11]G9), and the smaller group (genetic group I) contained HRV strains of subgroup I specificity (genotype P[4]G2). The NSP4 sequence of the rhesus rotavirus vaccine strain was distinct from all other strains and formed the third group (genetic group III). The NSP4 genes of animal rotaviruses UK, NCDV, and SA11 (genetic group I) and YM (genetic group II) and two possible human‐animal rotavirus reassortant strains, Brazilian P[8]G5 and Indian P[11]G9 (genetic group II), could also be classified into one of these groups, suggesting a close evolutionary relationship between human and animal NSP4 genes. These results will facilitate studies of the host immune response to NSP4, which may be relevant to future HRV vaccine design. J. Med. Virol. 53:41–50, 1997. Published 1997 Wiley‐Liss, Inc.

The cag Pathogenicity Island of Helicobacter pylori Is Disrupted in the Majority of Patient Isolates from Different Human Populations

ABSTRACT The cag pathogenicity island (cag-PAI) is one of the major virulence determinants of Helicobacter pylori. The chromosomal integrity of this island or the lack thereof is speculated to play an important role in the progress of the gastroduodenal pathology caused by H. pylori. We determined the integrity of the cag-PAI by using specific flanking and internally anchored PCR primers to know the biogeographical distribution of strains carrying fully integral cag-PAI with proinflammatory behavior in vivo. Genotypes based on eight selected loci were studied in 335 isolates obtained from eight different geographic regions. The cag-PAI appeared to be disrupted in the majority of patient isolates throughout the world. Conservation of cag-PAI was highest in Japanese isolates (57.1%). However, only 18.6% of the Peruvian and 12% of the Indian isolates carried an intact cag-PAI. The integrity of cag-PAI in European and African strains was minimal. All 10 strains from Costa Rica had rearrangements. Overall, a majority of the strains of East Asian ancestry were found to have intact cag-PAI compared to strains of other descent. We also found that the cagE and cagT genes were less often rearranged (18%) than the cagA gene (27%). We attempted to relate cag-PAI rearrangement patterns to disease outcome. Deletion frequencies of cagA, cagE, and cagT genes were higher in benign cases than in isolates from severe ulcers and gastric cancer. Conversely, the cagA promoter and the left end of the cag-PAI were frequently rearranged or deleted in isolates linked to severe pathology. Analysis of the cag-PAI genotypes with a different biogeoclimatic history will contribute to our understanding of the pathogen-host interaction in health and disease.

Geographical difference in antimicrobial resistance pattern of Helicobacter pylori clinical isolates from Indian patients: Multicentric study

Aim:  To assess the pattern of antimicrobial resistance of Helicobacter pylori isolates from peptic ulcer disease patients of Chandigarh, Delhi, Lucknow, Hyderabad and Chennai in India, and to recommend an updated anti‐H. pylori treatment regimen to be used in these areas.

Prevalence of Duodenal Ulcer‐Promoting Gene (dupA) of Helicobacter pylori in Patients with Duodenal Ulcer in North Indian Population

Background:   The duodenal ulcer (DU)‐promoting gene (dupA) of Helicobacter pylori has been identified as a novel virulent marker associated with an increased risk for DU. The presence or absence of dupA gene of H. pylori present in patients with DU and functional dyspepsia in North Indian population was studied by polymerase chain reaction (PCR) and hybridization analysis.

High prevalence of rotavirus infection among neonates born at hospitals in Delhi, India: predisposition of newborns for infection with unusual rotavirus.

Although rotavirus is the most common cause of diarrhea in children older than 3 months of age, neonatal infections, which are asymptomatic, have rarely been surveyed and have been identified in only a few discrete nosocomial outbreaks. After such a nosocomial outbreak of rotavirus infection among newborns at a hospital in Delhi, we screened infants born at five other nurseries in the immediate area to assess the prevalence of neonatal infections and to determine whether the unique neonatal rotavirus strain, 116E, previously identified in Delhi, was present in other settings. Infection was documented in 43 to 78% of hospitalized infants between 4 and 6 days of life born at five of the six hospitals. Infection with strains related to 116E were the most common, but other unusual strains and no strains common in the community were detected. In addition a shift in genotype was observed among specimens collected from two of these hospitals during a 2-year period. Our observation that neonatal rotavirus infections are more common than recognized previously would encourage the administration of rotavirus vaccines during the newborn period and suggests that the low efficacy of vaccines observed during trials in developing countries may be caused by early natural exposure of infants before immunization. The extraordinary predisposition of neonates for unusual rotavirus strains not commonly found in the community should encourage others to screen neonates for this infection, characterize the strains more fully and attempt to understand at a molecular level the unique relationship between the infecting strain type and the age of the host.

Antibiogram pattern and seasonality of Salmonella serotypes in a North Indian tertiary care hospital

The antibiogram pattern and seasonal distribution of Salmonella serotypes were analysed retrospectively over a 6-year period from January 1999 to December 2004. Blood cultures received in the Bacteriology Laboratory were processed by standard procedures and the Salmonella spp. isolates were identified with specific antisera and standard biochemical tests. Antimicrobial susceptibility testing was carried out by a standard disc diffusion method and the minimum inhibitory concentration (MIC) of ciprofloxacin for 332 representative Salmonella isolates was determined by E test. Salmonella Typhi (75.7%) was the predominant serotype among 830 Salmonella spp. isolated during the study period followed by S. Paratyphi A (23.8%). The maximum number of enteric fever cases occurred during April-June (dry season) followed by July-September (monsoon season). There was a decrease in multidrug-resistant (MDR) S. Typhi, but MDR S. Paratyphi A isolates increased. There was also a dramatic increase in nalidixic acid-resistant isolates. All isolates were susceptible to third-generation cephalosporins and ciprofloxacin except one S. Typhi strain which demonstrated high-level ciprofloxacin resistance with a MIC of 16 mug/ml. A knowledge of the seasonal distribution and antibiotic resistance pattern of Salmonella in a particular geographical region is helpful in the delineation of appropriate control measures required for prevention of enteric fever.

Characterization of Pseudomonas aeruginosa isolated from chronically infected children with cystic fibrosis in India

BackgroundPseudomonas aeruginosa is the leading cause of morbidity and mortality in patients with cystic fibrosis (CF). With chronicity of infection, the organism resides as a biofilm, shows multi-drug resistance, diversifies its colony morphology and becomes auxotrophic. The patients have been found to be colonized with multiple genotypes. The present work was carried out to characterize P. aeruginosa isolated from children with cystic fibrosis using phenotypic and genotypic methods.ResultsWe studied 56 patients with CF attending the Pediatric Chest clinic at All India Institute of Medical Sciences, New Delhi, India during August 1998-August 2001. These patients were regularly followed up at the clinic. Out of 56 patients, 27 were culture positive for P. aeruginosa where 8 were chronically infected (Group1) and 19 were intermittently colonized with the organism (Group2). Patients under Group1 had significantly higher rates of hospitalization, death and colonization with different colony morphotypes (p < 0.05). The isolates from Group1 patients were the positive producers of extended spectrum beta lactamase. A total of 5 auxotrophs were recovered from 2 patients where one was chronically infected with P. aeruginosa and the other was a recently enrolled patient. The auxotrophs had the specific requirement for methionine and arginine. Molecular typing revealed 33 ERIC-PCR (E1-E33) and 5 PCR-ribotyping (P1-P5) patterns. By ERIC-PCR, 4 patients were colonized with 2–4 genotypes and the remaining 23 patients were colonized with the single genotype.ConclusionWith chronicity of infection, P. aeruginosa becomes multidrug resistant, diversifies its colony morphology, acquires mucoidity and shows auxotrophy for amino acids. The chronically infected patients can be colonized with multiple genotypes. Thus in a particular clinical set up, high index of suspicion should be there for diagnosis of CF patients so as to prevent the delay in diagnosis and management of CF patients.

Molecular mechanism of action of major Helicobacter pylori virulence factors

Although Helicobacter pylori infects 50% of the total human population, only a small fraction of the infected people suffer from severe diseases like peptic ulcers and gastric adenocarcinoma. H. pylori strains, host genotypes and environmental factors play important role in deciding the extent and severity of the gastroduodenal diseases. The bacteria has developed a unique set of virulence factors to survive in the extreme ecological niche of human stomach. Together these virulence factors make H. pylori one of the most successful human pathogenic bacteria colonizing more than half of the human population. Understanding the mechanism of action of the major H. pylori virulence factors will shed light into the molecular basis of its pathogenicity.

Nasopharyngeal carriage ofHaemophilus influenzae

Objective: Nasopharyngeal colonization ofHaemophilus influenzae (H. influenzae) in young children may be important in developing countries.Method: In this study, we screened school going children for carriage ofH. influenzae. A total of 44H. influenzae isolates out of a collection of 162 were characterized for biotypes, capsular serotypes and antibiotic resistance.Results:A significant proportion ofH. influenzae (25/44) isolates were serotype b. High antibiotic resistance was observed against commonly administered antibiotics like ampicillin (79%), chloramphenicol (20%), trimethoprim sulfamethoxazole (84%) and erythromycin (95%). Comparison of antibiotic resistance profile of nasopharyngeal isolates was observed to be correlated with those ofH. influenzae from disease.Conclusion: Multidrug resistant nasopharyngealH. influenzae in young healthy children may act as reservoir. Monitoring of antibiotic resistance among nasopharyngealH. influenzae as a surrogate for invasiveH. influenzae seems an attractive option.