Jothimani Pradeep

Enterobacteriaceae represent a clinically challenging bacterial family owing to the global emergence of multidrug resistance. Bacteriophages, the natural predators of these bacteria, have emerged as powerful tools for detecting, targeting, and inhibiting these pathogens. This review provides a comprehensive overview of bacteriophages targeting Enterobacteriaceae hosts, focusing on their diversity, virion architecture, and the molecular determinants of host specificity. The dynamic co-evolution between bacterial defence strategies and phage counter-defences is discussed to illustrate the complexity of the phage-Enterobacteriaceae host interactions. Translational applications of Enterobacteriaceae phages, including phage therapy, engineered phages, phage-derived lysins as antimicrobials, and phage-based diagnostics for rapid and specific pathogen detection is also explored alongside their limitations including limited large-scale clinical trials, regulatory and manufacturing hurdles, and the need for robust host-range prediction and standardization. Overall, this review elaborates implications of bacteriophage-Enterobacteriaceae interactions to combat antimicrobial resistance and support the development of next-generation antibacterial therapies and diagnostics.

Tobacco-related diseases are the foremost cause of death globally. This research investigates the impact of smoking on lung function and the colonization of respiratory pathogens in asymptomatic smokers. Forty male smokers and forty age-matched non-smoker controls aged between 25-45 years were recruited. Nicotine dependence was evaluated using the Fagerstrom test for nicotine dependence questionnaire, while cumulative tobacco consumption was measured in pack-years. Pulmonary function test (PFT) was performed and morning sputum samples were collected for the molecular detection of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis using the conventional polymerase chain reaction (PCR) method. PFT parameters FVC (L), FEV1 (L), FEV1/FVC%, PEFR (L/m) and FER25-75% (L/s) were lower in smokers when compared to controls. H. influenzae was detected in 65% of smokers and 20% of controls, whereas S. pneumoniae was detected in 57.5% of smokers and 12.5% of controls. M. catarrhalis was detected 5% in only smokers. After sequencing, the identified virulent H. influenzae strain SC50876 was found in smokers. Through the application of multiple regression analysis, it was found that there are significant negative correlations between H. influenzae and both FVC and PEFR in individuals who smoke. This study provides novel evidence that smoking impairs lung function and promotes early colonization of the lower respiratory tract by Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, particularly the virulent H. influenzae strain SC50876. Multiple regression analysis revealed a significant negative association between bacterial presence and FVC and PEFR in asymptomatic smokers, suggesting that such colonization may accelerate functional decline and contribute to the early development of respiratory disease in otherwise asymptomatic individuals.

Enzyme linked Immunosorbent Assay (ELISA) and Immunofluorescence Assay (IFA) are specific serological tests for Scrub Typhus (ST). The etiological agent, Orientia tsutsugamushi DNA is demonstrable by PCR. Different countries apply ST IgM IFA cut-off titres ranging from 1:10 to 1:10240. To avoid confusion, Scrub Typhus Inclusion Criteria (STIC) was proposed. One criterion was a fourfold increase to or single IFA titre of ≥1:10240, later lowered to ≥1:3200. Equally sensitive and specific ELISA has no place in STIC. Modification of STIC is needed for robust laboratory confirmation of ST. One hundred and forty clinically suspected ST patients, including 58 patients who provided paired blood samples, were subjected to ST IgM ELISA, IgM IFA and Real time PCR targeting 56kDa, 47kDa and groEL genes. Among paired samples, all 58 (100%) acute sera were positive for IgM ELISA while 49 were positive in IgM IFA (84.5%). Among convalescent samples, 50 and 43 were positive in ST IgM ELISA and ST IgM IFA (86.2% and 74.1%) respectively. Regarding 82 unpaired samples, IgM ELISA and IgM IFA positivity was observed in 82 (100%) and 72 (87.8%) cases, respectively. PCR positivity in 140 ST cases for all three or any two gene targets, 56kDa, 46kDa and groEL as per STIC was 84, while an additional 40 samples were positive for any one gene. In Indian context, STIC requires modification to include IgM ELISA positivity, lower IgM cutoff IFA titre of ≥1:64 and any one gene positivity in Real time PCR.

Scrub typhus (ST) is a re-emerging zoonotic disease caused by Orientia tsutsugamushi and is transmitted by chiggers. Serological tests targeting IgM and/or IgG antibodies play a major role in the detection of ST cases. Orientia 56kDa genome is common target for the molecular diagosis of ST to identify the prevalence of specific serotypes of O. tsutsugamushi in and around Puducherry by targeting 56kDa gene with the application of phylogenetic analysis. This prospective laboratory-based study was conducted in a tertiary care teaching hospital, from November 2105 to March 2018. Blood samples were collected from out-patients/in-patients, and those tested positive for ST IgM ELISA (n=140) and an equal number of negative samples were archived and anonymized. Genomic DNA was extracted and analyzed by using Nested PCR and LAMP assay. The positive products were purified and sequenced. Phylogenetic tree was constructed based on the sequences. Among 280 samples, 45 (16.1%) N-PCR and 102 LAMP (36.43%) positivity was observed for 56kDa gene. Forty-one N-PCR positive products were sequenced and accession numbers were obtained (MG601875 to MG601917) for the isolates. Phylogenetic analysis was done by Maximum Likelihood methods and this study has showed that 32.3% are similar to the Karp isolates. Molecular diagnosis of Scrub typhus has become essential in case of doubtful serology and early acute phase of illness. Gene sequencing result indicates that most of them were different from the existing ones, which may belong to the newer strains. The identification of newer strains will be helpful in future for development of scrub typhus vaccine.

Background and Aim: Diagnosis of query fever (QF) is mostly done on the basis of serological/molecular tests, due to the stringent requirement of biosafety level-3 containment facilities for isolating Coxiella burnetii in culture. QF is an important zoonosis and is considered to be an occupational hazard to livestock handlers. This report describes our study on the serological as well as molecular evidence of QF in animal handlers from Puducherry and surrounding Tamil Nadu, from where, to the best of our knowledge, no such reports are available so far. Materials and Methods: Seventy-five animal handlers were recruited, comprising veterinarians, slaughterhouse workers, butchers, and animal attendants of various government veterinary clinics from Puducherry and surrounding areas of Tamil Nadu state. QF serology was performed to identify Phase I and Phase II immunoglobulin G antibodies to C. burnetii. Nested polymerase chain reaction (N-PCR) was carried out to detect C. burnetii DNA in buffy coat samples by targeting IS1111 gene element. N-PCR-positive samples were sequenced and phylogenetic analysis was performed using MEGA software version 10.0. Results: A total of 21 animal handlers (28.1%) were positive for either serology or PCR. PCR alone was positive in 10 (13.4%), only serology was positive in 8 (10.7%), and both serology and PCR were positive in three samples (4.0%). GenBank accession numbers were obtained for 13 N-PCR-positive samples (MG548608-MG548620). Six of our study sequences showed close similarity with the reference isolates from Bengaluru, Colombia, Brazil, France, and Iran. Conclusion: A significant percentage of QF positivity in animal handlers of this part of South India, Puducherry, warrants a prospective study with follow-up of a large number of this occupational group.