Neluka Fernando

Helicobacter pylori Infection in an Urban African Population

ABSTRACT We have studied 221 adults drawn from an impoverished urban population with high human immunodeficiency virus (HIV) seroprevalence (35%) to determine the prevalence of gastroduodenal pathology and its relationship to serological markers of Helicobacter pylorivirulence proteins and other potential environmental and immunological determinants of disease including HIV infection. Eighty-one percent were H. pylori seropositive, and 35% were HIV seropositive. Urban upbringing and low CD4 count were associated with a reduced likelihood of H. pylori seropositivity, as was current Ascaris infection, in keeping with recent evidence from an animal model. One hundred ninety-one adults underwent gastroduodenoscopy, and 14 had gastroduodenal pathology. Mucosal lesions were a major cause of abdominal pain in this population. While the majority of patients with gastroduodenal pathology (12 of 14) were seropositive for H. pylori, none were seropositive for HIV. Smoking was associated with increased risk of macroscopic pathology, and a history of Mycobacterium bovis BCG immunization was associated with reduced risk. Antibodies to H. pylorilipopolysaccharide were associated with pathology. HIV infection was associated with protection against mucosal lesions, suggesting that fully functional CD4 lymphocytes may be required for the genesis of gastroduodenal pathology.

HLA Class I and Class II Associations in Dengue Viral Infections in a Sri Lankan Population

Background HLA class I and class II alleles have been shown to be associated with the development of dengue hemorrhagic fever (DHF)/dengue shock syndrome (DSS) in different populations. However, the majority of studies have been based on limited numbers of patients. In this study we aimed to investigate the HLA-class I and class II alleles that are positively and negatively associated with the development of DSS in a cohort of patients with DHF and also the alleles associated with development of DHF during primary dengue infections in a Sri Lankan population. Methodology/Principal Findings The allele frequencies of HLA class I and class II alleles were compared in 110 patients with DHF and 119 individuals from the population who had never reported a symptomatic dengue infection at the time of recruitment. We found that HLA-A*31 (corrected P = 0.01) and DRB1*08 (corrected P = 0.009) were associated with susceptibility to DSS when infected with the dengue virus, during secondary dengue infection. The frequency of DRB1*08 allele was 28.7 times higher than in the normal population in patients with DSS. HLA-A*31 allele was increased 16.6 fold in DHF who developed shock when compared to those who did not develop shock. A*24 (corrected P = 0.03) and DRB1*12 (corrected P = 0.041) were strongly associated with the development of DHF during primary dengue infection. Conclusions/Significance These data suggest that certain HLA alleles confer susceptibility/protection to severe dengue infections. As T cell epitope recognition depend on the HLA type of an individual, it would be now important to investigate how epitope specific T cells associate with primary and secondary dengue infections and in severe dengue infections.

Prevalence of Helicobacter pylori in Sri Lanka as Determined by PCR

ABSTRACT Fifty-seven Sinhalese patients were investigated for the presence of Helicobacter pylori by PCR. A prevalence of 70.1%, with 47.5% positive for cagA, was demonstrated. The most common vacA allele was s1am1. There was no significant association between either the s1 allele or the cagA allele and severe gastroduodenal disease. There was an association between the s1 allele and the cagA locus.

IE63-specific T-cell responses associate with control of subclinical varicella zoster virus reactivation in individuals with malignancies

Background:Reactivation of the varicella zoster virus (VZV) is more common in patients with malignancies; however, the molecular and cellular mechanisms underlying this susceptibility are unclear.Methods:Using ex vivo interferon-γ ELISpot assays, we set out to analyse VZV-specific immune responses in a large cohort of patients with malignancies.Results:We observed that patients with malignancies had impaired VZV-specific T-cell responses, particularly in those with haematological malignancies and breast carcinoma. Immediate-early protein 63 (IE63)-specific T-cell responses were significantly impaired in those with subclinical VZV re-activation.Conclusions:Our results suggest that T-cell responses to IE63 are important in controlling VZV replication.

Identification of serotype‐specific T cell responses to highly conserved regions of the dengue viruses

Determining previous infecting dengue virus (DENV) serotypes has been difficult due to highly cross‐reactive immune responses from previous DENV infections. Determining the correlates of serotype‐specific immune responses would be crucial in understanding dengue transmission in the community and would also help to determine the correlates of protective immune responses. Therefore, we set out to define highly conserved, serotype‐specific regions of the DENVs. Serotype‐specific and highly conserved regions of the four DENV serotypes were identified using Basic Local Alignment Search Tool (BLAST) searches and custom perl scripts. Using ex‐vivo and cultured enzyme‐linked immunospot (ELISPOT) assays, we identified serotype‐specific T cell epitopes within the four DENV serotypes in healthy adult donors from Sri Lanka. We identified T cell responses to 19 regions of the four DENV serotypes. Six peptides were from the NS2A region and four peptides were from the NS4A region. All immune donors responded to peptides of at least two DENV serotypes, suggesting that heterologous infection is common in Sri Lanka. Eight of 20 individuals responded to at least two peptides of DENV‐4, despite this serotype not being implicated previously in any of the epidemics in Sri Lanka. The use of these regions to determine past and current infecting DENV serotypes will be of value to characterize further the dynamics of silent dengue transmission in the community. In addition, these T cell responses to these regions could be used to characterize DENV serotype‐specific immune responses and thus possibly help us to understand the immune correlates of a protective immune response.

Characteristics of Staphylococcus aureus colonization in patients with atopic dermatitis in Sri Lanka

Background.  Colonization of the skin of patients with atopic dermatitis (AD) by Staphylococcus aureus (SA) is associated with more severe disease.

Presence of Helicobacter pylori in betel chewers and non betel chewers with and without oral cancers

AbstractBackgroundBetel chewing has been shown to predispose to periodontal disease and oral cancer. Studies show that people with gum disease are more likely to test positive for Helicobacter pylori (H. pylori). It is not known if the lesions produced by betel quid and the resulting, chemical changes predispose to colonization by H. pylori. Further the role of this organism in oral cancer is not known. Our objective was to determine the presence of H. pylori in oral lesions of thirty oral cancer patients and to determine the presence of IgG antibodies to H. pylori in oral cancer patients who are betel chewers and non betel chewers, healthy betel chewers and healthy non-betel chewers and to compare the presence of H. pylori in these four groups. This case control study was conducted at the Cancer Institute Maharagama and the Department of Microbiology, Faculty of Medical Sciences, University of Sri Jayewardenepura.MethodsOne hundred and seventy three subjects, of whom fifty three were patients presenting with oral cancer to the Cancer Institute Maharagama, sixty healthy betel chewers and sixty healthy non-betel chewers from the Religious and Welfare Service Centre Maharagama were tested for H. pylori by serology. Thirty oral biopsies from oral cancer patients were cultured under microaerophilic condition to isolate H. pylori. The statistic used was Chi-square test.ResultsOf the fifty-three oral cancer patients, forty-four were betel chewers. Among the 53 oral cancer patients examined, ten of forty-four (10/44 = 22.7%) patients who are betel chewers and four of nine (4/9 = 44.4%) patients who are non-betel chewers were detected positive for IgG antibody against H. pylori. In the healthy group (betel chewers and non betel chewers) ten (16.7%) of the healthy betel chewers tested positive for H. pylori by serology. None of the healthy non-betel chewers tested positive for H. pylori Fourteen [26.4%] of oral cancer patients tested positive for H. pylori by serology, of which two were also culture positive (Only thirty samples were cultured). The presence of H. pylori in betel chewers (with or without cancer) compared to non-betel chewers was statistically significant. (Chi-square test p < 0.05) The use of tobacco and areca nut in betel chewers was significant with the presence of H. pylori (p < 0.05).ConclusionThere is a significant higher proportion of H. pylori in betel chewers compared to non-betel chewers but not between oral cancer patients compared to patients without oral cancer. Hence Betel chewing may predispose to colonisation with H. pylori in the digestive tract through swallowing the quid or during betel chewing.

Culture media profoundly affect Candida albicans and Candida tropicalis growth, adhesion and biofilm development

As there are sparse data on the impact of growth media on the phenomenon of biofilm development for Candida we evaluated the efficacy of three culture media on growth, adhesion and biofilm formation of two pathogenic yeasts, Candida albicans and Candida tropicalis. The planktonic phase yeast growth, either as monocultures or mixed cultures, in sabouraud dextrose broth (SDB), yeast nitrogen base (YNB), and RPMI 1640 was compared, and adhesion as well as biofilm formation were monitored using MTT and crystal violet (CV) assays and scanning electron microscopy. Planktonic cells of C. albicans, C. tropicalis and their 1:1 co-culture showed maximal growth in SDB. C. albicans/C. tropicalis adhesion was significantly facilitated in RPMI 1640 although the YNB elicited the maximum growth for C. tropicalis. Similarly, the biofilm growth was uniformly higher for both species in RPMI 1640, and C. tropicalis was the slower biofilm former in all three media. Scanning electron microscopy images tended to confirm the results of MTT and CV assay. Taken together, our data indicate that researchers should pay heed to the choice of laboratory culture media when comparing relative planktonic/biofilm growth of Candida. There is also a need for standardisation of biofilm development media so as to facilitate cross comparisons between laboratories.

Biosynthesized silver nanoparticles: are they effective antimicrobials?

BACKGROUND Silver nanoparticles (AgNPs) are increasingly being used in medical applications. Therefore, cost effective and green methods for generating AgNPs are required. OBJECTIVES This study aimed towards the biosynthesis, characterisation, and determination of antimicrobial activity of AgNPs produced using Pseudomonas aeruginosa ATCC 27853. METHODS Culture conditions (AgNO3 concentration, pH, and incubation temperature and time) were optimized to achieve maximum AgNP production. The characterisation of AgNPs and their stability were evaluated by UV-visible spectrophotometry and scanning electron microscopy. FINDINGS The characteristic UV-visible absorbance peak was observed in the 420–430 nm range. Most of the particles were spherical in shape within a size range of 33–300 nm. The biosynthesized AgNPs exhibited higher stability than that exhibited by chemically synthesized AgNPs in the presence of electrolytes. The biosynthesized AgNPs exhibited antimicrobial activity against Escherichia coli, P. aeruginosa, Salmonella typhimurium, Staphylococcus aureus, methicillin-resistant S. aureus, Acinetobacter baumannii, and Candida albicans. MAIN CONCLUSION As compared to the tested Gram-negative bacteria, Gram-positive bacteria required higher contact time to achieve 100% reduction of colony forming units when treated with biosynthesized AgNPs produced using P. aeruginosa.

Candida infection in oral leukoplakia: an unperceived public health problem.

Abstract Objectives: The study aimed to determine the proportion, known risk factors and etiology for Candida infection in leukoplakia lesions among patients with oral leukoplakia attending the Oral and Maxillofacial Clinic at a Tertiary Care Hospital in Sri Lanka. Materials and methods: Eighty clinically suspected oral leukoplakia patients were included. Two oral swabs each, from leukoplakia patients: one swab from the lesion and the other one from the contralateral unaffected corresponding area (as a control) were collected. Direct microscopy and culture followed by colony count and phenotypic identification were performed to identify pathogenic Candida species. Results: Candida infection was seen in 47% of patients with oral leukoplakia. Candida albicans (94.7%) was the most common Candida species followed by Candida tropicalis (5.3%). Majority of Candida-infected lesions were seen in the buccal mucosa region. Alteration of taste (p = 0.021), having other oral lesions (p = 0.008), angular cheilitis (p = 0.024) and periodontitis (p = 0.041) showed a significant association with Candida-associated leukoplakia. Increasing age showed a significant tendency for Candida infection (p = 0.020). Smoking (p = 0.026) and betel-quid chewing (p = 0.006) were also found to be significantly associated, although alcohol consumption alone did not show a significant association. Oral leukoplakia patients who had all three habits: alcohol consumption, smoking and betel-quid chewing had a significant association with Candida infection (p = 0.004). Conclusions: Patients who had a combination of risk factors: smoking, betel-quid chewing and alcohol consumption were seen to have a significant association with Candida infection. Further betel-quid chewing alone and smoking singly was also significantly associated with Candida infection in oral leukoplakia.