Recombinant viral proteins delivered orally through inactivated bacterial cells induce protection in Macrobrachium rosenbergii (de Man) against White Tail Disease

White tail disease (WTD) is a disease of Macrobrachium rosenbergii caused by Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV) with the potential to devastate the aquaculture industry. The present study aimed to explore the possible protection of M. rosenbergii against the disease by oral administration of bacterially expressed recombinant capsid proteins of MrNV and XSV. Juvenile M. rosenbergii were fed with the feed coated with inactivated bacteria encapsulated expressed recombinant viral proteins either individually or in combination for 7 days. Challenge studies using WTD causing agents were carried out after 3 (group I), 10 (group II) and 20 (group III) days post-feeding of viral proteins. Recombinant capsid protein of MrNV showed better protection when compared to other treatments with relative per cent survival of 62.5% (group I), 57.9% (group II) and 39.5% (group III). Treatment controls of groups I, II and III showed 100%, 95% and 95% mortality, respectively. The study demonstrates that oral administration of recombinant capsid proteins of MrNV and XSV provides effective protection against WTD in freshwater prawn.

Molecular investigation of the dengue outbreak in Karnataka, South India, reveals co-circulation of all four dengue virus serotypes

The growing incidence of dengue outbreaks in the state of Karnataka prompted us to study the circulating dengue virus (DENV) and their proportion among the suspected cases of dengue patients during the disease outbreak at Mysuru district of Southern India. The presence of the DENV in a patient's serum sample was identified by RT-PCR using previously published primer pairs targeting CprM gene. DENV serotyping was carried out by semi-nested multiplex PCR using serotype-specific primers and nucleotide sequencing. Three hundred fifty-five samples of serum from suspected dengue cases were collected, and 203 samples (57.18%) were found positives. In 2016, DENV-4 (97.87%) was found to be the most dominant DENV serotype either alone or as co-infection, followed by DENV-2 (8.51%) and DENV-3 (4.25%). In 47 positive cases, co-infection with more than one serotype was detected in 4 cases (8.51%). The analysis of the dengue cases in 2017, DENV-4 was dominating serotype (33.97%), followed by the emergence of DENV-2 (32.05%), DENV-3 (25.64%), and DENV-1 (25.00%). Our study also reports the circulation of all four DENV serotypes in the Mysuru district of Southern India, with concurrent infections rate of 16.66% in 2017. The present study provides information regarding the genetic variation among the circulating DENV serotype in an Indian state of Karnataka. The need for the studying genetic diversity of DENV will be useful during the continuous monitoring for disease burden as well as the development of appropriate prophylactic measures to control the spread of dengue infection.

Phenotypic characterization of auxotrophic mutant of nontyphoidal Salmonella and determination of its cytotoxicity, tumor inhibiting cytokine gene expression in cell line models

An auxotrophic mutant of nontyphoidal Salmonella (NTS) strain (Salmonella Oslo) was phenotypically characterized in this study. The characterization was based on phenotype, morphology, motility, biofilm forming ability, growth kinetics, etc. The phenotypic results from the above experiments determined that the mutant showed variation in phenotypic characters from that of wild-type strain. Subsequently, mutant and wild-type NTS were subjected to epithelial cell invasion and intracellular replication assays. The real-time PCR analysis was also performed to analyse expression of tumor inhibiting cytokine genes and virulence genes post-bacterial infection in cell lines. The mutant showed highest invasion potential than wild-type NTS whereas the replication of mutant was slower in both the cell lines. Similar to the wild-type strain, the mutant also retained the cytotoxic potential when analysed in vitro. Furthermore, the expression of proinflammatory cytokine genes such as TNF-α and IL-1β was upsurged with the downregulation of anti-inflammatory cytokine genes like TGF-β, IL-6 and IL-10 post-infection of the mutant strain in cell lines. In addition, virulence genes of Salmonella pathogenicity island one and two of mutant were downregulated in vitro except invA in HeLa cell line. Therefore, the auxotrophic mutant showed positive attributes of a potential antitumor agent in terms of expressing tumor inhibiting cytokine genes when assessed in vitro. Though the study did not check the tumor inhibitory effect of NTS strain directly, findings of the study emphasizes on the development of a novel strain of NTS with less virulence and more immunogenic traits to inhibit tumor cells.

Molecular analysis shows the presence of periodontal bacterial DNA in atherosclerotic plaques from patients with coronary artery disease

Links between periodontitis and atherosclerosis can be predicted based on inflammatory mechanisms initiated by bacteria associated with periodontal lesions, which then influence the initiation or propagation of the atherosclerotic lesion. This study aimed to detect the presence of three periodontal pathogens, in atheromatous plaques of patients with coronary artery disease. Subgingival and atherosclerotic plaque samples were obtained from 80 patients scheduled for CABG or angioplasty. A nested PCR was done for the detection of the pathogens in the plaque samples. Porphyromonas gingivalis, Tanarella forsythia, and Treponema denticola were detected in 10%, 12.5%, and 1.3% of the atherosclerotic plaque samples respectively. It was also observed that patients whose atherosclerotic plaques tested positive for one or more of the pathogens had chronic periodontitis.

Evaluation of loop-mediated isothermal amplification assay along with conventional and real-time PCR assay for sensitive detection of pathogenic Vibrio parahaemolyticus from seafood sample without enrichment

The primary reason for foodborne illness is improper seafood safety testing, and hence, an appropriate tool for testing is the key to control the outbreaks. The current study aimed to develop a loop-mediated isothermal amplification (LAMP) assay to detect pathogenic Vibrio parahaemolyticus, important foodborne pathogen, targeting tdh, and trh genes. The specificity of the LAMP assay was good without any false-positive and false-negative results. The assay was highly sensitive and could detect the pathogenic V. parahaemolyticus as low as 1 CFU/reaction in spiked seafood samples and 1 pg of extracted DNA. Out of 62 seafood samples from India’s southwest coastal region tested with LAMP assay, eight (12.9%) were positive for trh, and seven (11.29%) samples were positive tdh gene. LAMP-based on tdh and trh was found to be significantly more sensitive (p < 0.05) than conventional PCR and nearly equal sensitive as real-time PCR (RT-PCR) for the detection of pathogenic V. parahaemolyticus. Our study shows that LAMP assay can be a better approach as a point-of-care (POC) diagnostic tool and could detect pathogenic V. parahaemolyticus on seafood samples directly without enrichment and isolation. The high sensitivity and simplicity make LAMP assay a better alternative method than the conventional method and RT-PCR for the detection of pathogens. LAMP assay can be considered as a good alternative to PCR for the routine detection of pathogenic V. parahaemolyticus in seafood.

Deletion in the C-terminal region of the envelope glycoprotein in some of the Indian SARS-CoV-2 genome

The envelope glycoprotein (E) is the smallest structural component of SARS-CoVs; plays an essential role in the viral replication starting from envelope formation to assembly. The in silico analysis of 2086 whole genome sequences from India performed in this study provides the first observation on the extensive deletion of amino acid residues in the C-terminal region of the envelope glycoprotein in 34 Indian SARS-CoV-2 genomes. These amino acid deletions map to the homopentameric interface and PDZ binding motif (PBM) present in the C-terminal region of E protein as well as immediately after the reverse primer binding region as per Charité protocol in 26 of these genomes, hence, their detection through RT-qPCR may not be hampered and therefore E gene-based RT-qPCR would still detect these isolates. Eight genomes from the State of Odisha had deletion even in the primer binding site. It is possible that the deletions in the C-terminal region of E protein of these genomes are a result of adapting to a newer geographical area and host. The information on the clinical status was available only for 9 out of 34 cases and these were asymptomatic. However, further studies are indispensable to understand the functional consequences of amino acid deletion in the C terminal region of SARS-CoV-2 envelope protein in the viral pathogenesis and host adaptation.

Genomic and antibody-based assays for the detection of Indian strains of Macrobrachium rosenbergii nodavirus and extra small virus associated with white tail disease of Macrobrachium rosenbergii

White tail disease (WTD) of cultured Macrobrachium rosenbergii is caused by Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV). Since both the viruses have small single strand RNA as genetic material with short generation time, they are more prone to mutations. Hence detection methods developed for one strain may be suboptimal for the detection of isolates from the different geographical locations. In the present study two new genomic based methods (RT-PCR and dot-blot hybridization) along with one immunological method (polyclonal antibodies based detection) were developed for the detection of Indian isolates of MrNV and XSV. Among genomic based methods, RT-PCR assay developed was most sensitive. Sensitivity of detection of RT-PCR was 1 fg (both MrNV and XSV) of total RNA extracted from purified viral inoculum preparation. In case of WTD positive whole tissue total RNA, the limit of detection was 10 fg for both MrNV and XSV. Dot-blot hybridization had a detection limit of 10 pg and 0.1 ng for MrNV and XSV respectively when RNA extracted from viral inoculum preparation was used; 0.1 ng and 1 ng when WTD positive whole tissue total RNA was used. Polyclonal antibodies against recombinant proteins (MrNV and XSV capsid) were synthesised. Western blotting and indirect ELISA revealed that the antibodies produced to be specific and highly sensitive. Recombinant protein (antigen) of MrNV and XSV capsid were detected at the dilution of 1:8000. However in case of infected prawn tissue sample, MrNV and XSV were detected at the dilution of 1:32,000 and 1:64,000 respectively. All methods developed are field applicable.

Development of a rapid and low-cost method for the extraction of dermatophyte DNA

Background:

Polymerase chain reaction (PCR) is the most optimized method for the rapid detection and analysis of any environmental or clinically significant organism. While PCR amplification directly from samples has been shown effective for several bacteria and viruses, for filamentous fungus and yeast, extraction of genomic DNA is a must. The extraction of DNA from fungal cultures is often reported using user-friendly commercially available kits, which are designed to decrease the time, extensive manual work in extraction procedures but are often expensive. Dermatophytes pose an added drawback to efficient DNA extraction due to their poor recovery on culture media and slow growth rate.

Aims and Objectives:

In the present study, we developed and validated a method for effective genomic DNA extraction from dermatophytes.

Materials and Methods:

DNA yield from standard dermatophytes extracted from spore suspensions and mycelia mat by commercially available kits was compared. A modified method using lyticase buffer and phenol-chloroform extraction was developed. The yield obtained was compared with the existing methods (kit-based method and cetyl trimethyl ammonium bromide method). The yield and quality of the total genomic DNA were estimated spectrophotometrically and by successful PCR amplification of the ITS region. The results were validated using 21 clinical isolates from recalcitrant dermatophytosis.

Results:

Minimal fungal DNA was obtained from the spores compared to that obtained from mycelial mat. Commercially available kits yielded lower amounts of DNA compared to the CATB method. The modified method developed in this study yielded better quality and quantity of DNA.

Conclusion:

Of the three extraction methods evaluated, the developed method gave significantly higher total genomic DNA yield and better purity than the reference methods. In addition, the turnaround time for DNA extraction was reduced to half based on modifications in culture conditions.

Occurrence of antibiotic resistance among Gram negative bacteria isolated from effluents of fish processing plants in and around Mangalore

The presence of antibiotic-resistant bacteria in seafood not only poses a serious health risk for the consumers but also contributes to the spread of these antibiotic-resistant bacteria in the natural environments through the effluents discharged from the fish processing plants. The aims of this study were to isolate Gram-negative bacteria from the effluents of fish processing plants in and around Mangalore, India and to profile their antibiotic resistance pattern. Maximum resistance was seen for ampicillin (40.78%) followed by tetracycline (40.22%) and nitrofurantoin (29.05%). Further, the detection of genes that contribute to antibiotic resistance revealed the presence of sulfonamide resistance genes (sul1 and sul2) and extended spectrum β-lactamase genes (bla _CTX-M, bla _TEM) in a few isolates. The presence of such bacteria in fish processing effluents is a matter of great concern because they can contribute significantly to the antibiotic resistance in the natural environment. It is imperative that seafood processing plants follow the safe disposal of effluents in order to reduce or eliminate the antibiotic resistance menace.

Composition and Laboratory Correlation of Commercial Probiotics in India

Objectives Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer health benefits to the host. Probiotics are currently being recommended and considered for many medical conditions. The Asia-Pacific region contributes to more than 40% of the global industry. Quality of commercial probiotics remains a challenge globally and has been a major concern in various countries in Europe, South Africa, Taiwan, India, Pakistan, and the USA. Research from these countries indicate that the contents do not correspond to the label information in terms of identity, viability, number of microorganisms or purity. The objective of this study is to assess the commercial probiotic bacterial contents and their label accuracy in India. No previous research has been done in this area in India, on commercial probiotics that are sold as "pharmaceuticals". Methods A random selection of the most prescribed probiotics for various clinical indications were chosen with a minimum shelf life of 12 months. The probiotics were single and multiple strains and these were evaluated by culture, viable plate count, DNA isolation and targeted metagenomics. Our study is the first step in scrutinizing probiotics in terms of quality and quantity analysis which are used across various age groups for multiple indications. Results Out of the 20 chosen probiotics eight products were single strain and 12 products were multiple strains. These probiotics showed very poor correlation between the declared contents on the pack and lab values in viable cell count colonies, the genus and species strain identification, presence of contaminants and these were confirmed with 16s RNA and next generation sequencing. Conclusion Poor correlation in the quality and quantity of probiotics proves that the label claim and actual claim of these "drugs" show exceptionally poor correlation and raises safety concerns in clinical use, especially in vulnerable age groups such as neonates, children and the elderly. Our study shows that "policing" of these probiotics is essential in protecting these patients who are at risk and ensuring quality control and helping clinicians making the right choice.

Fate of respiratory droplets in tropical vs temperate environments and implications for SARS-CoV-2 transmission

The new pandemic of SARS-CoV-2 has shown stark differences in number of affected patients between countries in the tropics and those with temperate environments. Though there have been many theories on reasons for these differences, we hypothesise that this could be due to differences in the fate of respiratory droplets in the two environments. A simple understanding of the mechanics of droplet size, dispersion and displacement could help infection control and public health measures to minimize spread and mitigate the risk of people getting infected especially in hotspots like hospital environments or other closed spaces. This paper discusses the possibility of differences in number of infections and spread between different countries based on the spread of droplets.

Application of Outer Membrane Protein-Based Vaccines Against Major Bacterial Fish Pathogens in India

Aquaculture is one of the fastest-growing food-producing sectors in the world. However, its growth is hampered by various disease problems due to infectious microorganisms, including Gram-negative bacteria in finfish aquaculture. Disease control in aquaculture by use of antibiotics is not recommended as it leads to antibiotic residues in the final product, selection, and spread of antibiotic resistance in the environment. Therefore, focus is on disease prevention by vaccination. All Gram-negative bacteria possess surface-associated outer membrane proteins (OMPs), some of which have long been recognized as potential vaccine candidates. OMPs are essential for maintaining the integrity and selective permeability of the bacterial membrane and play a key role in adaptive responses of bacteria such as solute and ion uptake, iron acquisition, antimicrobial resistance, serum resistance, and bile salt resistance and some adhesins have virulence attributes. Antigenic diversity among bacterial strains even within the same bacterial species has constrained vaccine developments, but OMPs that are conserved across serotypes could be used as potential candidates in vaccine development, and several studies have demonstrated their efficacy and potential as vaccine candidates. In this review, we will look into the application of OMPs for the design of vaccines based on recombinant proteins, subunit vaccines, chimeric proteins, and DNA vaccines as new-generation vaccine candidates for major bacterial pathogens of fish for sustainable aquaculture.

Exploring the Pathogenic Potential of Vibrio vulnificus Isolated from Seafood Harvested along the Mangaluru Coast, India

It has been observed that not all strains of Vibrio vulnificus are virulent. Determining the virulence of strains that are frequently present in seafood is of significance for ensuring seafood safety. This study is an attempt to predict the virulence of seafood-borne V. vulnificus isolated along the Mangaluru Coast, India. The isolates tested possessed a vcgC gene sequence with high similarity to that in the clinical strain. Transcriptional analysis of core virulence genes in seafood isolate E4010 showed the phenomenon of contact-mediated expression of rtxA1 which correlated well with the actin disintegration and cytotoxicity. These results suggest that the seafood isolates tested in this study possess a functional RtxA1 which could help in initiating the infection. However, other putative virulence genes such as vvpE encoding an extracellular protease, vvhA encoding hemolysin, flp encoding tad pilin and ompU encoding fibronectin-binding protein were also constitutively expressed. Virulence-associated attributes such as cytotoxicity and adherence matched the response of the clinical strain (p > 0.05). On the other hand, the environmental strains showed higher serum sensitivity compared with the clinical strain. These findings show that the part of virulence attributes required for the disease process might be intact in these isolates.

Burkholderia vietnamiensis causing a non-lactational breast abscess in a non-cystic fibrosis patient in Tamil Nadu, India

Burkholderia cepacia complex is a Gram-negative opportunistic pathogen usually found in people with an immunocompromised condition such as cystic fibrosis (CF). In a tropical country like India, this organism has been associated with a number of hospital-acquired infections including sepsis. We present here a report of a case of Burkholderia vietnamiensis causing a non-lactational breast abscess in a non-CF patient. The pathogen was identified as B. cepacia using Vitek system and matrix-assisted laser desorption ionisation-time of flight. This was confirmed by polymerase chain reaction (PCR) using recA genus-specific gene and sequencing of the PCR amplicons. recA-restriction fragment length polymorphism and recA gene sequencing revealed that the isolate is B. vietnamiensis. This is the first description of B. vietnamiensis isolated from a clinical case from India.

Effect of bile on growth and biofilm formation of non-typhoidal salmonella serovars isolated from seafood and poultry

Bacterial cells adopt various strategies to adapt themselves in diverse environmental conditions. Salmonella is one such bacteria with diverse mechanisms to survive, replicate and infect in wide host range. This study aims at investigating the biofilm-forming ability of multidrug-resistant and sensitive Salmonella serovars on exposure to bile. Antibiogram of all the isolates was determined by disk diffusion method and their biofilm-forming ability in the presence or absence of bile was assessed by microtiter plate assay. Biofilm results were validated by calcofluor, Congo red plate and test tube method. Few isolates were selected for further study of their expression of biofilm related genes on exposure to bile using real time PCR. Among the 59 isolates of Salmonella isolated from seafood and poultry, 30 isolates were multi-drug resistant (MDR). Under control conditions, 57% (n = 25) of the serovars were able to form biofilm. While, 86% (n = 51) of the serovars produced biofilm in the presence of bile. The relative gene expression study of the selected serovars for 8 different genes showed a striking difference in the expression levels, supporting the hypothesis that the presence of bile triggers biofilm formation in food associated strains of non-typhoidal Salmonella by upregulation of genes involved in biofilm production.

Cancer Theranostics: Bridging Conventional and Nano-photodynamic Therapy

Cancer is of various kinds, so are the treatment modalities. Worldwide, cancer is the second leading cause of death, accounting for a whopping 9.6 million deaths in 2018. Globally, approximately one in six deaths is attributed to cancer. Photodynamic therapy (PDT) is a therapeutic strategy for the treatment of superficial lesions, warts, Barrett’s esophagus, premalignant lesions, malignant tumors, and ophthalmic diseases. The literature on PDT is approximately one-third of that in radiation therapy, yet the clinical implementation of PDT in cancer is relatively less. Despite substantial research, the clinical application of photodynamic strategy in cancer therapy is still in its infancy with only a limited number of case studies reported so far. The limitations of the photosensitizer and the shallow depth of penetration of light source are the key technical impediments. However, the use of nanomedicine in PDT can overcome these obstacles. Thus, it is necessary to gain knowledge on how nanomaterials can be merged with PDT and how it can be utilized in cancer theranostics. In this article, the focus is to understand how PDT works and how it can be utilized in improving the sensitivity of the existing diagnostic and therapeutic techniques. The article also addresses the current challenges for PDT and the future prospects of this technique, particularly in the area of diagnosis and treatment of cancer.

Hospital wastewater treatment reduces NDM-positive bacteria being discharged into water bodies

New Delhi metallo-β-lactamase-1 (NDM-1) is a novel type of metallo-β-lactamase (MBL) associated with Enterobacteriaceae constitutes an important growing public health threat. The present study aims to characterize the NDM-1 producing Gram-negative bacteria (GNB) from the effluents of two tertiary care hospitals in Mangalore, South India and to profile their antibiotic resistance pattern. A total of 134 GNB were isolated from 30 hospital wastewater samples (treated and untreated) and analyzed. High-level resistance among untreated effluent sample was found toward nalidixic acid (74.52%), followed by cefotaxime (72.64%) and ampicillin (66.03%). Among the treated effluent isolates, the high resistance was found toward ampicillin (85.71%) followed by cefotaxime (85.71%) and piperacillin-tazobactam (53.57%). From untreated effluent isolates, 9 were NDM-1 positive by PCR; no isolates from treated effluent samples harbored bla_NDM-1 . Untreated hospital wastewater is found to be important reservoirs of antibiotic-resistant bacteria carrying bla_NDM-1 , and the presence of such bacteria in the effluents is a matter of great concern because they can contribute the antibiotic resistance to the natural environment. However, the absence of NDM in treated effluents emphasizes the importance of effluent treatment in reducing the dissemination of antibiotic-resistant bacteria. PRACTITIONER POINTS: Hospital wastewater is the important reservoir of antibiotic-resistant bacteria especially metallo-β-lactamase producers (NDM-1). Wastewater treatment procedures in hospitals reduce the NDM isolates in the treated effluent. Thereby reduces the risk of resistance spread in the environment.

Facile coconut inflorescence sap mediated synthesis of silver nanoparticles and its diverse antimicrobial and cytotoxic properties

Green synthesis of nanoparticles (NPs) involves the use of diverse extracts of biological origin as substrates to synthesize NPs and can overcome the hazards associated with chemical methods. Coconut inflorescence sap, which is unfermented phloem sap obtained by tapping of coconut inflorescence, is a rich source of sugars and secondary metabolites. In this study, coconut inflorescence sap was used to synthesize silver NPs (AgNPs). We have initially undertaken metabolomic profiling of coconut inflorescence sap from West Coast Tall cultivar to delineate its individual components. It was found to comprise of 64% secondary metabolites, 9% sugars, 12% lipids/fats and 9% peptides in positive mode, whereas in the negative mode, it was 33, 20, 9 and 11%, respectively. The concentration of silver nitrate, inflorescence sap and incubation temperature for the synthesis of AgNPs were optimized. Incubating the reaction mixture at 40 °C was found to enhance AgNP synthesis. The AgNPs synthesized were characterized using UV-visible (UV-Vis) spectrophotometry, X-Ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). The particles were crystalline in nature and the bulk of the particles were spherical with smooth (thin) shell and poly-dispersed with a diameter ranging from 10 nm to 30 nm. Antimicrobial property of AgNPs was tested in tissue culture of arecanut (Areca catechu L.) where bacterial contamination (Bacillus pumilus) was a frequent occurrence. A significant reduction in the contamination was observed when plantlets were treated with aqueous solutions of AgNPs. Notably, treatment with AgNPs did not affect the growth and development of the arecanut plantlets. Antimicrobial properties of AgNPs synthesized from inflorescence sap were also evaluated in human pathogenic bacteria viz., Escherichia coli ATCC 25922; Salmonella Typhimurium ATCC 14028 and Vibrio parahaemolyticus AQ4037. The antibacterial action was confirmed by determining the production of reactive oxygen species (ROS) and protein leakage studies. Cytotoxicity of AgNPs was quantified in HeLa cells. The viability (%) of HeLa cells declined significantly at 10 mg L^-1 concentration of AgNP and complete mortality was observed at a concentration of 60 mg L^-1. The study concludes that unfermented inflorescence sap, with above neutral pH, serves as an excellent reducing agent to synthesize AgNPs from Ag+.

Draft genome sequences of Salmonella Oslo isolated from seafood and its laboratory generated auxotrophic mutant

In recent years, the concept of bacteria-mediated cancer therapy has gained significant attention as an alternative to conventional therapy. The focus has been on non-typhoidal Salmonella (NTS), particularly S. Typhimurium, for its anti-cancer properties, however, other NTS serovars such as Salmonella Oslo, which are associated with foodborne illnesses could potentially be effective anti-cancer agents. Here, we report the draft genome sequence of Salmonella Oslo isolated from seafood and its laboratory generated auxotrophic mutant.

Plasmid-mediated fluoroquinolone resistance associated with extra-intestinal Escherichia coli isolates from hospital samples

Background & objectives

Infection from fluoroquinolone-resistant extra-intestinal Escherichia coli is a global concern. In this study, isolation and characterization of fluoroquinolone-resistant extra-intestinal E. coli isolates obtained from hospital samples were undertaken to detect plasmid-mediated quinolone resistance (PMQR) genes.

Methods

Forty three isolates of E. coli obtained from patients with extra-intestinal infections were subjected to antibiogram to detect fluoroquinolone resistance. The mechanism of fluoroquinolone resistance was determined by the detection of PMQR genes and mutations in quinolone resistance determining region (QRDR).

Results

Of the 43 isolates, 36 were resistant to nalidixic acid (83.72%) and 28 to ciprofloxacin (65.11%). Eight E. coli isolates showed total resistance to both the antimicrobials without any minimum inhibitory concentration. The detection of PMQR genes with qnr primers showed the presence of qnrA in two, qnrB in six and qnrS in 21 isolates. The gene coding for quinolone efflux pump (qepA) was not detected in any of the isolates tested. The presence of some unexpressed PMQR genes in fluoroquinolone sensitive isolates was also observed.

Interpretation & conclusions

The detection of silent PMQR genes as observed in the present study presents a risk of the transfer of the silent resistance genes to other microorganisms if present in conjugative plasmids, thus posing a therapeutic challenge to the physicians. Hence, frequent monitoring is to be done for all resistance determinants.

Mismatch amplification mutation assay-polymerase chain reaction: A method of detecting fluoroquinolone resistance mechanism in bacterial pathogens

The mismatch amplification assay is a modified version of polymerase chain reaction (PCR) that permits specific amplification of gene sequences with single base pair change. The basis of the technique relies on primer designing. The single nucleotide mismatch at the 3’ proximity of the reverse oligonucleotide primer makes Taq DNA polymerase unable to carry out extension process. Thus, the primers produce a PCR fragment in the wild type, whereas it is not possible to yield a product with a mutation at the site covered by the mismatch positions on the mismatch amplification mutation assay (MAMA) primer from any gene. The technique offers several advantages over other molecular methods, such as PCR-restriction fragment length polymorphism (RFLP) and oligonucleotide hybridization, which is routinely used in the detection of known point mutations. Since multiple point mutations in the quinolone resistance determining region play a major role in high-level fluoroquinolone resistance in Gram-negative bacteria, the MAMA-PCR technique is preferred for detecting these mutations over PCR-RFLP and sequencing technology.

CTX-M type extended-spectrum β-lactamase in Escherichia coli isolated from extra-intestinal infections in a tertiary care hospital in south India

Background & objectives:

Infections caused by extended-spectrum β-lactamase (ESBL)-producing Escherichia coli carrying bla_CTX-M genes have been spreading globally, but there are geographical variations in the type of bla_CTX-M genes prevalent and there are scanty data from India. This study was conducted to determine the CTX-M type ESBLs in E. coli isolates obtained from clinical specimens from patients with extra-intestinal infections attending a tertiary care hospital in south India.

Methods:

ESBL-producing E. coli isolated from patients with extra-intestinal infections were subjected to PCR using CTX-M group-specific primers. From a representative isolate, full-length CTX-M-15 gene was amplified and sequenced. An internal fragment of this gene was sequenced in 10 representative isolates.

Results:

Of the 300 isolates of E. coli tested, 88 per cent carried CTX-M genes and bla_CTX-M-15 was the most dominant gene present in 90 per cent of the positive isolates. Most (91%) of the isolates positive for bla_CTX-M were sensitive to meropenem.

Interpretation & conclusions:

Our findings showed bla_CTX-M-15 to be the dominant gene. Based on the data on antimicrobial susceptibility, cefoperazone-sulbactum could be an antimicrobial of choice.

Phenotypic & genotypic study of antimicrobial profile of bacteria isolates from environmental samples

Background & objectives

The resistance to antibiotics in pathogenic bacteria has increased at an alarming rate in recent years due to the indiscriminate use of antibiotics in healthcare, livestock and aquaculture. In this context, it is necessary to monitor the antibiotic resistance patterns of bacteria isolated from the environmental samples. This study was conducted to determine the phenotypic and genotypic profile of antimicrobial resistance in Gram-negative bacteria isolated from environmental samples.

Methods

Two hundred and fifty samples were collected from different sources, viz. fish and fishery products (99), livestock wastes (81) and aquaculture systems (70), in and around Mangaluru, India. Isolation, identification and antimicrobial profiling were carried out as per standard protocols. The isolates were screened for the presence of resistance genes using PCR.

Results

A total of 519 Gram-negative bacteria comprising Escherichia coli (116), Salmonella spp. (14), Vibrio spp. (258), Pseudomonas spp. (56), Citrobacter spp. (26) and Proteus spp. (49) were isolated and characterized from 250 samples obtained from different sources. A total of 12 antibiotics were checked for their effectiveness against the isolates. While 31.6 per cent of the isolates were sensitive to all the antibiotics used, 68.4 per cent of the isolates showed resistance to at least one of the antibiotics used. One-third of the isolates showed multidrug resistance. Maximum resistance was observed for ampicillin (43.4%), followed by nitrofurantoin (20.8%). Least resistance was seen for carbapenems and chloramphenicol. PCR profiling of the resistant isolates confirmed the presence of resistance genes corresponding to their antibiotic profile.

Interpretation & conclusions

This study results showed high rate of occurrence of antimicrobial resistance and their determinants in Gram-negative bacteria isolated from different environmental sources.

Presence & mobility of antimicrobial resistance in Gram-negative bacteria from environmental samples in coastal Karnataka, India

To understand antimicrobial resistance (AMR) patterns and mechanisms of horizontal gene transfer in human-associated environments is essential to AMR surveillance. Gram-negative bacteria (1122 isolates) from food-animal environments were characterized for antimicrobial susceptibility and AMR genes. Seventy five per cent of the isolates (837 of 1122) were resistant to at least one of the antibiotics tested. Resistance to more than three groups of antimicrobials (multidrug resistance) was observed in 43 isolates with most often encountered (12 of 43) resistance to β-lactams, tetracycline, quinolones and nitrofurantoin. The profile of frequently reported plasmid-mediated resistance gene in these isolates was determined. The mobility of these elements as plasmids or phages was examined. The bla_CTX-M gene was present in the plasmid of 61 per cent and packed in induced phage fractions in 72 per cent of the isolates and bla_TEM in 69 per cent phage fractions compared to 15 per cent presence in the plasmid.