Progression of chronic pulmonary tuberculosis in mice intravenously infected with ethambutol resistant Mycobacterium tuberculosis.

Purpose: Ethambutol (EMB) is an important first line drug, however little information on its molecular mechanism of resistance and pathogenicity of resistant isolates is available. Present work was designed to study virulence of the EMB resistant M. tuberculosis strains and the host responses in-vivo on infection of EMB resistant M. tuberculosis using Balb/c mouse model of infection. Methods: Three groups of Balb/c mice (female, age 4-6 wk; 21 mice in each group) were infected intravenously with 106 CFU of M. tuberculosis H37Rv and two EMB resistant clinical isolates. Age and sex matched control animals were mock inoculated with Middlebrook 7H9 broth alone. At 10, 20, 30, 40, 50, 60, and 70 days post-infection three animals from each group were sacrificed by cervical dislocation and lung tissue was collected for further analysis. Results: Infection with EMB resistant M. tuberculosis led to progressive and chronic disease with significantly high bacillary load (p=0.02). Massive infiltration and exacerbated lung pathology with increased expression of IFN-gamma and TNF-alpha was observed in lungs of mice infected with EMB resistant strains. The present study suggests that infection with EMB resistant M. tuberculosis leads to chronic infection with subsequent loss of lung function, bacterial persistence with elevated expression of TNF-alpha resulting in increased lung pathology. Conclusion: These findings highlight that EMB resistant M. tuberculosis regulates host immune response differentially and its pathogenicity is different from drug sensitive strains of M. tuberculosis.

Bacterial isolates from mechanically ventilated patients with nosocomial pneumonia within intensive care unit of a tertiary care center.

Nosocomial pneumonia is a common complication in mechanically ventilated patients. A study was carried out to determine the incidence, common bacterial etiologic agents and their antimicrobial susceptibility, and outcome of such pneumonia in an Intensive Care Unit (ICU) of a tertiary care center. In Surgical ICU (SICU) 176 patients required mechanical ventilation for more than 72 hours. A total of 39 (22.1%) of these patients developed nosocomial bacterial pneumonia as determined by microbiological assays. Endotracheal aspirate cultures detected a single bacterial isolate in 22 (56.4%) patients while two and three organisms were isolated from 10 (25.6%) and 7 (17.9%) patients respectively. Fifty three (84.1%) of a total of 63 isolates were Gram negative bacilli. The most frequently encountered pathogens were Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter species among the Gram negative bacilli and Staphylococcus aureus among the Gram positives. Resistance of bacterial isolates varied from 24 to 90% against commonly used antibiotics. Amikacin had the best profile, with 14% to 55% resistance against various isolates. Twenty three (59%) of 39 patients with pneumonia expired in the ICU. P. aeruginosa (25.6%) and K. pneunmoniae (17.9%) were the predominant isolates in these patients. Nosocomial pneumonia with high mortality is a frequent occurrence in mechanically ventilated patients in our ICU setting. Gram negative organisms with high levels of antimicrobial resistance are the most common isolates. Regular surveillance and monitoring of changes in antibiotic susceptibility of bacterial pathogens and appropriate therapeutic measures are likely to reduce the mortality in these patients.

Molecular characterization of echovirus 11 isolates from India.

BACKGROUND & OBJECTIVES: Echovirus 11 (ECV11) is one of the most frequent non-polio enteroviruses isolated from stool samples of children with acute flaccid paralysis in north India. The present work was undertaken to study the sequence variability in the 440 bp of 5'-non-translated region of ECV11 genome using heteroduplex mobility assay (HMA). METHODS: Twelve ECV11 isolates were studied for sequence variability in the 5'-non-translated region (5'NTR) using the HMA followed by nucleotide sequencing. HMA was used to determine sequence diversity between Indian ECV11 isolates and prototype Gregory strain. HMA results were confirmed by 5'NTR nucleotide sequencing of five Indian ECV11 isolates. RESULTS: HMA results showed high genomic diversity between the prototype Gregory strain and Indian ECV11 isolates. All isolates were grouped into five different types of heteroduplex mobility patterns with respect to Gregory strain. A 440 bp 5'NTR fragment of five ECV11 isolates representing different heteroduplex patterns, was sequenced. The sequence alignment showed that 5'NTR of Indian isolates was different from prototype Gregory strain and identical to the ECV11 isolates of Finland and Hungary. Phylogenetic analysis including ECV11 isolate sequences from different parts of the world showed that Indian ECV11 isolates represented a different subgroup. INTERPRETATION & CONCLUSION: The results of the present study suggested that the HMA could be successfully used as a preliminary screening method for sequence variability determination of enterovirus field isolates. The sequence data generated on ECV11 isolates from India will be useful for future studies of endemic genotypes of echovirus.

Ralstonia mannitolilytica infection in renal transplant recipient: First report.

Ralstonia mannitolilytica is being increasingly identified as an opportunist pathogen in immunocompromised patients. We report the first case of post renal transplant infection by R. mannitolilytica, in a 14-year-old recipient. The graft and the patient were saved with prompt microbiological identification, sensitivity testing and subsequent administration of appropriate antibiotic.

Cryptococcal infection in patients with clinically diagnosed meningitis in a tertiary care center.

A retrospective analysis of 326 clinically diagnosed cases with meningitis over a period of five-and-a-half years was carried out to determine the prevalence of cryptococcal infection, its associated risk factors and therapeutic outcome. Fifty-four (16.6%) patients with cryptococcal meningitis were identified by smear examination, culture and/or cryptococcal antigen latex agglutination test. Records of 45 cryptococcal meningitis patients were available; 18 (40%) of them were apparently healthy immunocompetent individuals, 13 (28.9%) had human immunodeficiency virus (HIV) infection, 9 (20%) were renal transplant recipients, 4 (8.9%) were diabetic and 1 (2.2%) had systemic lupus erythematosus. Ten (22.2%) patients died and 11 (24.4%) patients (all HIV-positive) left against medical advice. The present study indicates that cryptococcal infection is associated with high mortality. Presenting symptoms being indistinguishable from other causes of central nervous system infection, all patients with a clinical diagnosis of meningitis, irrespective of their immune status should be investigated for cryptococcal infection.

Transmission of filarial infection through blood transfusion.

Microfilariae can be transmitted by blood transfusion and they may be circulated in the recipient's blood but they do not develop into adult worms. Mortality associated with transfusion associated filarial infection is not documented but it may give rise to morbidity in transfusion recipients in terms of allergic reaction. The present study was carried out to investigate the association of post transfusion reactions and filarial infections in an endemic area. About 11,752 transfusion recipients were followed up and in 15 months period, 47 (0.4%) post transfusion reactions (PTR) were reported. Routine investigations for post transfusion reaction were carried out in all 47 patients and their respective blood donor. Moreover, blood culture, microfilaria detection by concentration technique, filarial antibody and antigen detection (both by ELISA) were done in all subjects. Out of 47 patients showing post transfusion reaction, 29 (61.7%) patients developed allergic reaction. Eighteen (38.3%) patients having allergic reaction did not have previous history of blood transfusion and 14 (29.8%) of them received transfusion from blood donors who was either positive for microfilaria, filarial antigen or antibody. Microfilaremia was demonstrated in 4 (8.5%) patients and 5 (10.6%) blood donors. Microfilaria was concurrently present in 2 patients and their respective donors. Filarial antibody was detected in 27 (56.5%) patients and 26 (55.3%) blood donors but microfilaria was detected in 3 (6.4%) and 4 (8.5%) subjects, respectively. Antigen detection test correlated with microfileraemic state of subjects. The result shows that transfusion associated filarial infection may be a probable cause for transfusion-associated morbidity in endemic areas. In 14 (29.8%) patients having allergic reactions, the probable cause was transfusion-associated filarial infection. Filarial antigen detection test was found to be more useful in detecting infections. Blood donors with active history of filarial infection should be deferred from donating blood. Filarial antigen detection test may be employed as screening test for blood donors, if possible.

Candidaemia in patients of a tertiary health care hospital from north India.

BACKGROUND & OBJECTIVES: Candidaemia is an important cause of mortality in hospital settings. Limited information is available from India on nosocomial candidaemia. The objective of the present study was to isolate and identify yeasts from patients suspected to have nosocomial bloodstream infection (BSI) and to determine the carriage rate of Candida species, risk factors for acquisition of infection and mortality in this group of patients. METHODS: Blood samples from 4871 patients suspected to have BSI at least 48 h after admission were cultured following standard protocol to isolate and identify the pathogens. Clinical details, possible risk factors and outcome of all candidaemic patients were recorded and analysed. Samples of hand washings and throat gargles from these patients were also cultured to determine the carriage rate. Candida albicans isolated from patients and their carriage sites were genotyped by randomly amplified polymorphic DNA (RAPD) analysis to study strain relatedness. RESULTS: Twenty one patients with candidaemia were detected with mortality of 55 per cent. Candidaemia per 1000 admissions was 1.61. Isolation of non-C. albicans Candida species was significantly higher than C. albicans (14/21 vs 7/21: P < 0.05). Use of broad-spectrum antibiotics (43%), gastrointestinal surgery (23%), immunosuppressive therapy (23%), protein calorie malnutrition with parenteral hyperalimentation (23%) and neutropaenia (14%) were identified as probable risk factors. The seven C. albicans strains isolated from patients with BSI were typed into 6 genotypes. Yeast carriage rate among the patients was 71.4 per cent. C. albicans isolated from the hand, throat and blood of two patients had identical genotype. INTERPRETATION & CONCLUSION: BSI due to non-C. albicans Candida species is more common than C. albicans in our patients and candidaemia is associated with high mortality. RAPD appears to be a simple method to study strain relatedness for C. albicans. There is a need for early diagnosis and systematic surveillance to meet the challenges of nosocomial candidaemia.

Antibiotic associated diarrhoea: Infectious causes.

Nearly 25% of antibiotic associated diarrhoeas (AAD) is caused by Clostridium difficile, making it the commonest identified and treatable pathogen. Other pathogens implicated infrequently include Clostridium perfringens, Staphylococcus aureus, Klebsiella oxytoca, Candida spp. and Salmonella spp. Most mild cases of AAD are due to non-infectious causes which include reduced break down of primary bile acids and decrease metabolism of carbohydrates, allergic or toxic effects of antibiotic on intestinal mucosa and pharmacological effect on gut motility. The antibiotics most frequently associated with C. difficile associated diarrhoea are clindamycin, cephalosporin, ampicillin and amoxicillin. Clinical presentation may vary from mild diarrhoea to severe colitis and pseudomembranous colitis associated with high morbidity and mortality. The most sensitive and specific diagnostic test for C. difficile infection is tissue culture assay for cytotoxicity of toxin B. Commercial ELISA kits are available. Though less sensitive, they are easy to perform and are rapid. Withdrawal of precipitating antibiotic is all that is needed for control of mild to moderate cases. For severe cases of AAD, oral metronidazole is the first line of treatment, and oral vancomycin is the second choice. Probiotics have been used for recurrent cases.

UreC PCR based diagnosis of Helicobacter pylori infection and detection of cag A gene in gastric biopsies.

Polymerase chain reaction assay using ureC gene specific primers for the detection of Helicobacter pylori in gastric biopsy specimens from 116 dyspeptic patients was compared with other routine invasive diagnostic methods (culture, rapid urease test [RUT] and histology). In parallel, gastric biospy specimens from 54 patients and their corresponding Helicobacter pylori isolates were subjected to PCR with cagA targeting primers using standard protocols. Helicobacter pylori were detected in 53%, 43%, 48% and 50% of patients by PCR, RUT, culture and histological examination respectively. Based on histology and culture positive and at least three test positive result, 44 (37%), 46 (39%) and 26 (22%), and 56 (48%), 52 (44%) and 8 (6%) patients were classified as Helicobacter pylori positive, negative and indeterminate respectively. The sensitivity and specificity of PCR assay was the highest-95% and 100% when compared with both culture and histology positive, and at least any three positive results respectively. The result of cagA positivity in 54 gastric biopsy specimens and their corresponding Helicobacter pylori isolates were identical; 18 of 20 (90%) duodenal ulcer patients and 23 of 28 (82%) patients with chronic gastritis and 2 (40%) of 5 patients with portal hypertension and one gastric biopsy specimens from gastric cancer patients were found to be cagA positive. PCR-based method to detect Helicobacter pylori and the virulence gene cag A directly from gastric biopsy specimens appears to be promising and can curtail the lengthy process of culture-based approaches. The procedure proved to be rapid and reliable and could be utilized for diagnostic purposes.

Non-polio enteroviruses in acute flaccid paralysis.

OBJECTIVE: Human enteroviruses are the major cause of aseptic meningitis and also cause a wide range of other acute illnesses, including neonatal sepsis like disease, meningitis, acute flaccid paralysis and acute hemorrhagic conjunctivitis. Infection in neonates is particularly life threatening. METHODS: Stool samples of 523 children (age < 4 years) showing symptoms of acute flaccid paralysis (AFP) were studied. National Polio Surveillance Project workers from different parts of Uttar Pradesh and Bihar collected the samples during June to October 1998. Non-polio enteroviruses (NPEV) were isolated in 191 cases only, by cell culture based neutralization assay. These NPEV isolates were further studied to find the frequent enterovirus serotype detected in stool of children having AFP. RESULTS: Data generated will help future studies on NPEV serotypes circulating in this area. CONCLUSION: In addition it may reduce unnecessary hospitalization, allow immune globulin batches of high titres to frequently circulating serotypes, to be reserved for intravenous therapy of neonates and guide the formulation of antigens for rapid and less expensive diagnosis.

Campylobacter species associated with diarrhoea in patients from a tertiary care centre of north India.

BACKGROUND & OBJECTIVES: Most laboratories do not routinely distinguish the various Campylobacter species, though almost all Campylobacter species have been isolated from human faeces. The epidemiological and clinical aspects of its infection and the species involved in genesis of diarrhoea are least understood in the developing countries. The aim of the present study was to find out frequency of Campylobacter species isolated from patients with diarrhoea over a 12-year period and to analyse their features. METHODS: Campylobacter strains isolated from stool samples of patients with diarrhoea were identified to the species level on appropriate media at 42 degrees C micro-aerobically. Patients' demography and clinical data were analyzed retrospectively; 25 Campylobacter jejuni strains were tested for toxin production and 23 strains were typed by Penner scheme. RESULTS: A total of 62 strains were isolated from 59 patients and the various species were C. jejuni 51 (82.3%), C. coli 8 (12.9%), C. lari 2 (3.2%), and C. upsaliensis 1 (1.6%). Children < 5 yr of age were most affected (34/59; 57.6%), followed by patients in 15-30 yr of age (12/59; 20.3%). Presentation of watery diarrhoea was significantly more common than inflammatory diarrhoea (50/59, 84.7% vs 9/59, 15.3%; P < 0.001). Recurrence occurred in 3 (5.1%) patients. Majority of the infections resolved within one week; one HIV-positive patient had chronic diarrhoea. Two patients developed Guillain-Barré syndrome following Campylobacter infection. Twenty (80%) of 25 strains were toxigenic and 20 (87%) of 23 strains could be typed by Penner scheme. INTERPRETATION & CONCLUSION: In our patients, 4 different Campylobacter species and various C. jejuni serotypes were involved in gastroenteritis. Majority of the infections were watery diarrhoea and in children < 5 yr of age. There is a need of a population-based systematic study to know the epidemiology of whole spectrum of campylobacters in India.

Drug resistant Haemophilus influenzae from respiratory tract infection in a tertiary care hospital in north India.

Haemophilus influenzae is an important respiratory pathogen. Emergence of resistance to various antibiotics is a major problem in patient management. A total of 90 strains of H. influenzae were characterized from specimens obtained from patients of acute respiratory tract infection; 13 (14.4%) belonged to type beta. On biotyping, 90% strains belonged to biotype II. The frequency of resistance to various antibiotics was as follows: cotrimoxazole 33.3% ampicillin 21.1%, cephalexin 7.8%, chloramphenicol 7.8%, ciprofloxacin 2.5% erythromycin and tetracycline 5% each. All the ampicillin-resistant strains produced beta-lactamase as detected by nitrocefin disc method. None of the strains exhibited resistance to cefaclor and third generation cephalosporins. The present study showed emergence of variable resistance to ampicillin, cotrimoxazole and other antibiotics. It is important for the clinical microbiology laboratory to monitor drug resistant strains for instituting appropriate antibiotic therapy of respiratory infections due to H. influenzae.

Comparison of various conventional methods with a polymerase chain reaction assay for detecting methicillin-resistant & susceptible Staphylococcus aureus strains.

BACKGROUND & OBJECTIVES: Methicillin-resistant Staphylococcus aureus (MRSA), a major nosocomial pathogen world-wide, is often difficult to detect due to the heterogeneous nature of expression of oxacillin resistance. In the present study, various conventional methods were compared with polymerase chain reaction on 106 clinical isolates of Staph. aureus for detection of oxacillin resistance. METHODS: A total of 106 clinical isolates of Staph. aureus were tested for oxacillin resistance by disc diffusion, screen agar plates (3 micrograms and 6 micrograms/ml of oxacillin), oxacillin broth (3 micrograms/ml) and mecA based PCR. RESULTS: PCR detected mecA gene amplified product of 604 bp in 57 strains. Disc diffusion failed to detect 7 mecA positive strains but identified 5 mecA negative strains as oxacillin resistant. Screen agar 3 micrograms, screen agar 6 micrograms and oxacillin broth 3 micrograms detected 55, 53 and 55 respectively of the 57 mecA positive strains; however, they also falsely identified 5, 3 and 3 strains of mecA negative strains respectively as oxacillin resistant. The sensitivity, specificity and accuracy of disc diffusion, 3 micrograms screen agar, 6 micrograms screen agar and 3 micrograms oxacillin broth against PCR as gold standard were as follows: 87.7, 89.9 and 88.7 per cent; 96.5, 89.8 and 93.4 per cent; 93.0, 93.9 and 93.4 per cent; 96.5, 93.9 and 95.3 per cent respectively. INTERPRETATION & CONCLUSIONS: The present study demonstrated that disc diffusion test was least reliable and 3 micrograms broth had the highest sensitivity and specificity when compared with PCR for detection of oxacillin resistance. Because of variations among the methods, a combination of tests should be used for the accurate detection of MRSA till new guidelines by an appropriate body are formulated.

Identification of enteric pathogens in HIV-positive patients with diarrhoea in northern India.

Enteric pathogens associated with chronic diarrhoea in HIV-positive patients were studied. The study was conducted during January 1995-December 1998. Stool specimens from all diarrhoea patients (n = 26) were examined microscopically for ova and parasites using wet preparations and stained smears. Stool samples from diarrhoea patients were also cultured on appropriate media to isolate enteric bacterial pathogens. Of the 59 patients, 26 (44%) had prolonged diarrhoea for more than 4 weeks. Enteric pathogens were detected in 19 (73%) of the 26 patients: 17 patients harboured a single pathogen, and 2 patients had mixed pathogens. The detection rate of emerging parasites, including Isospora, Cryptosporidium, Blastocystis hominis, and Strongyloides stercoralis as a single agent, was significantly higher than conventional pathogens (50% vs 19.2%; p < 0.05). Only one patient harboured both conventional and emerging pathogens (Entamoeba histolytica and Cryptosporidium). Isospora belli was detected in 8 (31%) of the 26 diarrhoea patients: in 7 (27%) patients as a single agent and in one patient with S. stercoralis. Cryptosporidium was identified in 3 (11%) diarrhoea patients: in 2 (8%) patients as a single agent and in one patient with E. histolytica, followed by B. hominis in 2 (8%) patients. E. histolytica was most commonly isolated (3/26; 11.5%), followed by Giardia lamblia, enteropathogenic Escherichia coli, and Campylobacter jejuni (one patient each). Parasitic pathogens were frequently associated with HIV-positive patients with diarrhoea in northern India. I. belli was the most frequent parasite isolated, followed by Cryptosporidium. Stools of all HIV-positive patients with diarrhoea should thoroughly be investigated to identify aetiologic agents for proper management.

Role of yeasts as nosocomial pathogens & their susceptibility to fluconazole & amphotericin B.

A total of 213 and 208 yeasts were isolated as nosocomial pathogens from various infected specimens during 1996 and 1997 respectively. Yeasts ranked fifth among uropathogens in both the years and from eighth to eleventh in other specimens. Increasing trend in nosocomial urinary tract yeast infection (11.9 in 1996 to 12.6 in 1997) and decreasing trend in wound and other infections (5.1 in 1996 to 2.9 in 1997) per 1000 patients' discharges were observed; blood stream infection remained unchanged (2/1000 discharges) in both the years. Eighty two (41 from each year) randomly selected yeasts were identified to species level following standard protocol and tested for antifungal susceptibility against fluconazole and amphotericin B by reference broth macrodilution technique and agar dilution (AD) method. The frequency of various yeast species identified was Candida albicans 39 (47.6%), C.tropicalis 29 (35.4%), C. krusei 4 (4.9%), C. glabrata 3 (3.7%), C. zeylanoides 2 (2.4%), C. guilliermondii 2 (2.4%), one strain (1.2%) each of C. kefyr, C. parapsilosis, and Trichosporon beigelii. Resistance to fluconazole (MIC > or = 64 micrograms/ml) as per NCCLS criteria was observed in 2 Candida sp. (2.4%). Significantly higher number of non-albicans Candida sp. (8/43; 18.6%) had MIC > 8 micrograms/ml as compared to C. albicans (2/39; 5.1%) (P < 0.05). Only one strain of C. tropicalis had MIC 8 micrograms/ml to amphotericin B and none had MIC > 8 micrograms/ml. Agreement between the reference and the AD methods for fluconazole was 88 per cent and for amphotericin B was 94 per cent. The present study indicates that Candida sp. are emerging as important nosocomial pathogens and the tendency of yeasts to develop resistance to antifungal agents appears to be a challenge for patient management.

Isoenzyme and molecular characterization of Entamoeba histolytica and Entamoeba dispar isolates from symptomatic and asymptomatic subjects.

AIM: To correlate the clinical features of amebic infections with the characteristics of Entamoeba culture isolates of stools. METHODS: Isolates from seven irritable bowel syndrome (IBS) patients, four asymptomatic cyst passers (ACP) and five patients with invasive amebic disease were subjected to hexokinase polyacrylamide electrophoresis (HK-PAGE) and their DNA subjected to restriction fragment (RF) analysis of amplified polymerase chain reaction (PCR) products. These findings were correlated with anti-amebic serology. Two axenic pathogenic strains (HM1:IMSS, NIH:200) and one xenic nonpathogenic strain (SAW1734) were used as standards. RESULTS: All isolates from IBS patients as well as ACP had slow-moving (nonpathogenic) band pattern, whereas those from patients with invasive disease had fast-moving (pathogenic) band pattern on HK-PAGE. Serological data using EIA and RF patterns of PCR-amplified genome corroborated these results. CONCLUSIONS: Our results support the view that there are two species of Entamoeba infecting humans--E. histolytica(pathogenic) and E. dispar (nonpathogenic), and HK-PAGE of culture isolates can differentiate between them.

Effect of bacterial association on virulence of Entamoeba histolytica to baby hamster kidney cell monolayers.

Axenic E. histolytica trophozoite strain NIH:200 and HMI:IMSS when co-associated with aerobic bacteria Escherichia coli strain K12 and serotype 056 showed marked increase in virulence as observed by destruction of baby hamster kidney (BHK) monolayers. However, when incubated with anaerobic bacterial strains Clostridium perfringens and Bacteroides fragilis virulence remained unaltered. Further, adherence of E. histolytica to BHK monolayer was found to be mediated by N-acetyl-D-galactosamine.

Raised IgM antibodies to parvovirus B19 in juvenile rheumatoid arthritis.

To delineate the role of human parvovirus B19 in the etiopathogenesis of juvenile rheumatoid arthritis (JRA), IgM and IgG antibodies specific for parvovirus B19 surface protein antigen(s) were estimated in the sera using commercial ELISA kits. Sera of 69 JRA patients (median age 16 yr, male : female ratio 1.1:1) satisfying the criteria of American Rheumatism Association along with 26 sera of rheumatoid arthritis (RA) and 12 sera of healthy children as disease and normal controls respectively were screened. Of the 69 patients with JRA, 19 (27.5%), 35 (50.7%) and 9 (13%) were positive for IgM, IgG and both IgG and IgM antibodies respectively. Of the 26 disease control sera, 11 (42.3%) were positive for IgG antibodies while none had elevated IgM antibodies. Among 12 healthy controls, 7 (58.3%) were positive for IgG and 1 was positive for both IgG and IgM antibodies. Thus, a statistically significant proportion of children with JRA had evidence of parvovirus B19 infection.

Does Entamoeba histolytica cause irritable bowel syndrome?

BACKGROUND: Symptoms of patients with irritable bowel syndrome (IBS) closely mimic those of patients with non-dysenteric amebic colitis. AIM: To examine the clinical relevance of presence and types of Entamoeba histolytica in stools of patients with IBS. METHODS: IBS was diagnosed by Manning's criteria. Stool examination was done 4-weekly for 48 weeks to detect E. histolytica cysts or trophozoites. Patients underwent initial sigmoidoscopy. Sera of 22 IBS patients, 23 asymptomatic cyst passers and 36 healthy volunteers whose stools were also examined were tested for presence of antiamebic antibodies. Stools were cultured for amebae; positive cultures were subjected to polyacrylamide-gel electrophoresis (PAGE) using hexokinase (HK) isoenzyme to distinguish between pathogenic (fast-moving band) E. histolytica infection and nonpathogenic (slow band) species of Entamoeba dispar. RESULTS: E. histolytica cultured from stool samples of four IBS patients had slow-moving band of HK on PAGE. All patients spontaneously eradicated the infection during the next eight to 24 weeks; all had negative serology for antiamebic antibodies, and normal rectal mucosa on sigmoidoscopy. No change in symptom score occurred on follow up in IBS patients, although all of them cleared the infection. Three additional E. histolytica isolates from IBS patients obtained from another laboratory also showed nonpathogenic isoenzyme pattern. CONCLUSION: Bowel symptoms in IBS patients were not related to E. histolytica infection. The term non-dysenteric amebic colitis thus appears to be inappropriate, since it may be used erroneously for patients with IBS with nonpathogenic ameba, leading to injudicious treatment with antiamebic drugs.

The effect of in vitro bacterial association on virulence of Entamoeba histolytica.

When trophozoites of axenic E. histolytica strains NIH : 200 were associated in vitro with Escherichia coli K12 for three hours at 37 degrees C, the virulence was enhanced as shown by increased cytopathogenicity to baby hamster kidney (BHK) cell monolayer. Further, the trophozoites were observed to adhere to the polystyrene surface, a hitherto unreported phenomenon. The co-association of E. histolytica trophozoites with Bacteroides fragilis and Clostridium perfringens for three hours duration at 37 degrees C neither led to increase in cytotoxicity potential nor to adherence phenomenon; in contrast significant inhibition of cytotoxicity was observed. We have thus shown that while co-association of E. histolytica (NIH : 200) with E. coli K12 leads to enhanced amoebic virulence, that with anaerobic bacteric leads to its inhibition.