Padma Srikanth

Chikungunya: A Potentially Emerging Epidemic?

Chikungunya virus is a mosquito-borne emerging pathogen that has a major health impact in humans and causes fever disease, headache, rash, nausea, vomiting, myalgia, and arthralgia. Indigenous to tropical Africa, recent large outbreaks have been reported in parts of South East Asia and several of its neighboring islands in 2005–07 and in Europe in 2007. Furthermore, positive cases have been confirmed in the United States in travelers returning from known outbreak areas. Currently, there is no vaccine or antiviral treatment. With the threat of an emerging global pandemic, the peculiar problems associated with the more immediate and seasonal epidemics warrant the development of an effective vaccine. In this review, we summarize the evidence supporting these concepts.

A DNA Vaccine against Chikungunya Virus Is Protective in Mice and Induces Neutralizing Antibodies in Mice and Nonhuman Primates

Chikungunya virus (CHIKV) is an emerging mosquito-borne alphavirus indigenous to tropical Africa and Asia. Acute illness is characterized by fever, arthralgias, conjunctivitis, rash, and sometimes arthritis. Relatively little is known about the antigenic targets for immunity, and no licensed vaccines or therapeutics are currently available for the pathogen. While the Aedes aegypti mosquito is its primary vector, recent evidence suggests that other carriers can transmit CHIKV thus raising concerns about its spread outside of natural endemic areas to new countries including the U.S. and Europe. Considering the potential for pandemic spread, understanding the development of immunity is paramount to the development of effective counter measures against CHIKV. In this study, we isolated a new CHIKV virus from an acutely infected human patient and developed a defined viral challenge stock in mice that allowed us to study viral pathogenesis and develop a viral neutralization assay. We then constructed a synthetic DNA vaccine delivered by in vivo electroporation (EP) that expresses a component of the CHIKV envelope glycoprotein and used this model to evaluate its efficacy. Vaccination induced robust antigen-specific cellular and humoral immune responses, which individually were capable of providing protection against CHIKV challenge in mice. Furthermore, vaccine studies in rhesus macaques demonstrated induction of nAb responses, which mimicked those induced in convalescent human patient sera. These data suggest a protective role for nAb against CHIKV disease and support further study of envelope-based CHIKV DNA vaccines.

BIO-AEROSOLS IN INDOOR ENVIRONMENT: COMPOSITION, HEALTH EFFECTS AND ANALYSIS

Bio-aerosols are airborne particles that are living (bacteria, viruses and fungi) or originate from living organisms. Their presence in air is the result of dispersal from a site of colonization or growth. The health effects of bio-aerosols including infectious diseases, acute toxic effects, allergies and cancer coupled with the threat of bioterrorism and SARS have led to increased awareness on the importance of bio-aerosols. The evaluation of bio-aerosols includes use of variety of methods for sampling depending on the concentration of microorganisms expected. There have been problems in developing standard sampling methods, in proving a causal relationship and in establishing threshold limit values for exposures due to the complexity of composition of bio-aerosols, variations in human response to their exposure and difficulties in recovering microorganisms. Currently bio-aerosol monitoring in hospitals is carried out for epidemiological investigation of nosocomial infectious diseases, research into airborne microorganism spread and control, monitoring biohazardous procedures and use as a quality control measure. In India there is little awareness regarding the quality of indoor air, mould contamination in indoor environments, potential source for transmission of nosocomial infections in health care facilities. There is an urgent need to undertake study of indoor air, to generate baseline data and explore the link to nosocomial infections. This article is a review on composition, sources, modes of transmission, health effects and sampling methods used for evaluation of bio-aerosols, and also suggests control measures to reduce the loads of bio-aerosols.

H2S as an Indicator of Water Supply Vulnerability and Health Risk in Low-Resource Settings: A Prospective Cohort Study

In this large-scale longitudinal study conducted in rural Southern India, we compared a presence/absence hydrogen sulfide (H2S) test with quantitative assays for total coliforms and Escherichia coli as measures of water quality, health risk, and water supply vulnerability to microbial contamination. None of the three indicators showed a significant association with child diarrhea. The presence of H2S in a water sample was associated with higher levels of total coliform species that may have included E. coli but that were not restricted to E. coli. In addition, we observed a strong relationship between the percent positive H2S test results and total coliform levels among water source samples (R(2) = 0.87). The consistent relationships between H2S and total coliform levels indicate that presence/absence of H2S tests provide a cost-effective option for assessing both the vulnerability of water supplies to microbial contamination and the results of water quality management and risk mitigation efforts.

Mobile phones: emerging threat for infection control

This study was conducted to determine whether mobile phones of healthcare workers (HCWs) and T corporate users harbour micro-organisms. Swabs collected from mobile phones were inoculated in solid and liquid media, and incubated aerobically. Growth was identified as per standard microbiological procedures. Antibiotic susceptibility was determined for Staphylococcus aureus. A questionnaire was used for data collection on awareness of mobile phone use. Of 51 HCWs and 36 corporate mobile phones sampled, only 5 (6%) showed no growth. Pathogens isolated from HCW samples included S. aureus [meticillin-sensitive S. aureus (4), meticillin-resistant S. aureus (2)], Escherichia coli (1), Klebsiella pneumoniae (1) and Pseudomonas aeruginosa (1). Coagulase-negative Staphylococci (43) were also isolated. Among corporate isolates, 29% were pathogenic. Polymicrobial growth was detected in 71% of HCW and 78% of corporate mobile phones. Only 12% of HCWs used disinfectants to wipe their mobile phones. Mobile phones serve as a ready surface for colonisation of nosocomial agents indicating the importance of hand hygiene to prevent cross-transmission.

Rapid and Long-Term Immunity Elicited by DNA-Encoded Antibody Prophylaxis and DNA Vaccination Against Chikungunya Virus

Abstract Background. Vaccination and passive antibody therapies are critical for controlling infectious diseases. Passive antibody administration has limitations, including the necessity for purification and multiple injections for efficacy. Vaccination is associated with a lag phase before generation of immunity. Novel approaches reported here utilize the benefits of both methods for the rapid generation of effective immunity. Methods. A novel antibody-based prophylaxis/therapy entailing the electroporation-mediated delivery of synthetic DNA plasmids encoding biologically active anti–chikungunya virus (CHIKV) envelope monoclonal antibody (dMAb) was designed and evaluated for antiviral efficacy, as well as for the ability to overcome shortcomings inherent with conventional active vaccination and passive immunotherapy. Results. One intramuscular injection of dMAb produced antibodies in vivo more rapidly than active vaccination with an anti-CHIKV DNA vaccine. This dMAb neutralized diverse CHIKV clinical isolates and protected mice from viral challenge. Combination of dMAb and the CHIKV DNA vaccine afforded rapid and long-lived protection. Conclusions. A DNA-based dMAb strategy induced rapid protection against an emerging viral infection. This method can be combined with DNA vaccination as a novel strategy to provide both short- and long-term protection against this emerging infectious disease. These studies have implications for pathogen treatment and control strategies.

Study of the Indoor Air Quality in Hospitals in South Chennai, India — Microbial Profile

A 3-month pilot study (February—April 2006) was conducted to determine the quality of indoor air in hospitals in the Tamil Nadu region of India and to characterize the predominant aerobic bacteria and fungi present. The main objectives were (1) to sample the indoor air of three different hospitals in Chennai for bioaerosols to generate baseline data using the Petri plate gravitational settling (passive) method of sampling; and (2) to isolate and identify potentially pathogenic organisms prevalent in the hospital environment. Indoor air samples were collected from various wards at the different hospitals and processed for the identification of various predominant bacteria and fungi. The overall counts of Gram-positive organisms were found to be higher than Gram-negative organisms. Of these isolates, Staphylococci and Micrococci were the predominant Gram-positive bacteria, while Klebsiella sp. and Pseudomonas sp. were the predominant potentially pathogenic Gram-negative bacteria isolated. Among yeasts and molds, Aspergillus niger and A. flavus were commonly isolated.

Molecular characterization of Chikungunya virus during an outbreak in South India

INTRODUCTION Re-emergence of Chikungunya is a major public health problem in the southern states of India. OBJECTIVES This study was undertaken to investigate an outbreak of Chikungunya, in June-August 2008 using PCR and determine the prevalent genotypes of Chikungunya virus (CHIKV) associated with the outbreak. MATERIALS AND METHODS Samples of blood were collected (in heparinized vacutainer tubes) from suspected patients of CHIKV infection from both Government Taluk Hospital in Kerala and a tertiary care hospital in Chennai, Tamil Nadu. A one-step RT-PCR was carried out on a block thermo-cycler targeting the E2 gene that codes for the viral envelope protein. The amplicons were verified for 305 bp size by standard agarose gel electrophoresis. The PCR products were purified, sequenced, and compared with other CHIKV strains reported from different geographical regions. A phylogenetic tree was constructed using MEGA 4. RESULTS Altogether 118 samples were collected from patients who presented with sudden onset of fever and/or joint pain, myalgia, and headache. CHIKV infection was confirmed by RT-PCR in 14 patients and all these cases were from Kerala. The positivity correlated with the early stage of the disease as all these patients had fever of less than seven days duration. The study isolates have been allotted the GenBank accession nos. GQ272368-GQ272381. Phylogenetic analysis of recent CHIKV isolates by partial sequencing of E2 region shows that isolates are closely related to strains from neighboring states and the African type. CONCLUSION RT-PCR is a useful technique for the early detection of CHIKV infection during outbreaks. Molecular characterization of the strains indicates that majority of the strains have originated from the Central/East African strains of CHIKV.

Molecular and Nanotechnologic Approaches to Etiologic Diagnosis of Infectious Syndromes

Infectious diseases are a major global public health problem. Multiple agents are now recognized to cause indistinguishable illnesses. The term ‘syndrome’ applies to such situations, for which early and rapid diagnosis of the infecting agent would enable prompt and appropriate therapy. Public health physicians would also get timely information on the specific etiology of the infectious syndrome, facilitating intervention at the community level in the face of outbreaks or epidemics. A variety of molecular techniques have been evaluated for rapid diagnosis of infectious syndromes. These techniques include real-time multiplex PCR, DNA microarray, loop-mediated isothermal amplification, and other similar assays. This review surveys such state-of-the-art technologies.

Gut Microbiota in Type 2 Diabetes Individuals and Correlation with Monocyte Chemoattractant Protein1 and Interferon Gamma from Patients Attending a Tertiary Care Centre in Chennai, India

Background: Type 2 diabetes mellitus (T2DM) and obesity are associated with changes in gut microbiota and characterized by chronic low-grade inflammation. Monocyte chemoattractant protein-1 (MCP-1) and interferon gamma (IFNγ) are proinflammatory cytokines which play an important role in the development of T2DM. We undertook this study to analyze the gut microbiota of T2DM and nondiabetic subjects and to determine the profile of MCP 1 and IFNγ in the same subjects attending a tertiary care center in Chennai, Tamil Nadu, India. Methods: The study included 30 subjects with clinical details. Stool and blood samples were collected from all the subjects. DNA was extracted from fecal samples and polymerase chain reaction was done using fusion primers. Metagenomic analysis was performed using ion torrent sequencing. The reads obtained were in FASTA format and reported as operational taxonomic units. Human MCP 1 and IFNγ enzyme linked immunosorbent assay (ELISA) were performed for 23 serum samples. Results: The study consisted of 30 subjects; 17 were T2DM and 13 were nondiabetics. The gut microbiota among T2DM consisted predominantly of Gram negative bacteria; Escherichia and Prevotella, when compared with the nondiabetic group with predominantly Gram positive organisms suchas Faecalibacterium, Eubacterium, and Bifidobacterium. The mean MCP-1 values in the diabetic group were 232.8 pg/ml and in the nondiabetic group 170.84 pg/ml. IFNγ (mean 385.5 pg/ml) was raised in glycated hemoglobin (HbA1c) group of 6.5–7.5% which was statistically significant. Association of Escherichia with T2DM and association of Bifidobacteria in the nondiabetics were also statistically significant. Conclusion: Escherichia counts were elevated in T2DM with HbA1c of 6.5–8.5% which was statistically significant suggesting that lipopolysaccharides present in the cell wall of Gram-negative bacteria may be responsible for low-grade inflammation as evidenced by elevated MCP-1 and IFNγ levels in T2DM with the same HbA1c levels.