Characterisation of Antimicrobial Resistance in Salmonellae during 2014–2015 from Four Centres Across India: An ICMR Antimicrobial Resistance Surveillance Network Report

Clinical and antimicrobial susceptibility profile of typhoid fever in children in the era of antibiotic resistance

Enteric fever remains a significant public health problem in low- and middle-income countries with further challenges from emerging antimicrobial resistance. Our prospective study evaluated the current clinical and antimicrobial susceptibility profile of enteric fever in 88 children and compared it to previously established literature. Enteric fever usually presents with nonspecific signs and symptoms, with predominant respiratory complaints. A paradigm shift in the antimicrobial sensitivity pattern has been noted, with increasing resistance for first-line antibiotics and older antibiotics such as ampicillin, cotrimoxazole, and chloramphenicol showing good sensitivity. Thus, the introduction of the latter merits consideration.

Ceftriaxone-resistant Salmonella Typhi isolated from paediatric patients in north India: Insights into genetic profiles and antibiotic resistance mechanisms

PURPOSE

To investigate the antibiotic resistance and genetic profile of ceftriaxone-resistant Salmonella Typhi isolated from the blood culture of two paediatric cases of typhoid fever and one from the stool culture of their household contact, in North India.

METHODS

In this study, whole-genome sequencing was carried out with paired-end 2 ​× ​150 bp reads on Illumina MiSeq (Illumina, USA) employing v2 and v3 chemistry. To check data quality, adapters and low-quality sequences were removed through Trimmomatic-v0.36. High quality reads were then assembled de novo using A5-miseq pipeline. For further refinement, reference-guided contig ordering and orienting were performed on the scaffold assemblies using ABACAS (http://abacas.sourceforge.net/). The assembled genome was annotated using Prokka v1.12 to identify and annotate the gene content. Plasmid replicons in bacterial isolates were identified by PlasmidFinder, whereas mobile genetic elements were predicted using Mobile Element Finder. Referenced-based SNP tree with maximum likelihood method was built with CSI phylogeny v1.4.

RESULTS

All three isolates exhibited resistance to ceftriaxone, cefixime, ciprofloxacin, ampicillin, and co-trimoxazole, while demonstrating sensitivity to azithromycin and chloramphenicol. The whole-genome sequencing of these strains revealed the presence of blaCTX-M-15 gene for cephalosporin resistance in addition to gyrA, qnr and IncY plasmid replicon. A 5 ​kb IS91 Sbo1 gene cassette (IncY plasmid) was identified which carried extended spectrum β-lactamase blaCTX-M-15, blaTEM-1D (resistance to ampicillin and cephalosporin), sul2, dfrA14 (resistant to trimethoprim-sulfamethoxazole) and qnrS (resistant to ciprofloxacin). These isolates belong to H58 lineage and grouped as sequence type 1 (ST1) on multilocus sequence typing (MLST) analysis.

CONCLUSION

In the present study we report the isolation of blaCTX-M-15 positive S. Typhi from two paediatric patients presenting with fever and one from stool culture of their contact from North India and highlight the need for further investigations to understand the different factors contributing to ceftriaxone resistance in Salmonella Typhi.

Targeting novel sites in DNA gyrase for development of anti-microbials

Antimicrobial resistance in bacteria poses major challenges in selection of the therapeutic regime for managing the infectious disease. There is currently an upsurge in the appearance of multiple drug resistance in bacterial pathogens and a decline in the discovery of novel antibiotics. DNA gyrase is an attractive target used for antibiotic discovery due to its vital role in bacterial DNA replication and segregation in addition to its absence in mammalian organisms. Despite the presence of successful antibiotics targeting this enzyme, there is a need to bypass the resistance against this validated drug target. Hence, drug development in DNA gyrase is a highly active research area. In addition to the conventional binding sites for the novobiocin and fluoroquinolone antibiotics, several novel sites are being exploited for drug discovery. The binding sites for novel bacterial type II topoisomerase inhibitor (NBTI), simocyclinone, YacG, Thiophene and CcdB are structurally and biochemically validated active sites, which inhibit the supercoiling activity of topoisomerases. The novel chemical moieties with varied scaffolds have been identified to target DNA gyrase. Amongst them, the NBTI constitutes the most advanced DNA gyrase inhibitor which are in phase III trial of drug development. The present review aims to classify the novel binding sites other than the conventional novobiocin and quinolone binding pocket to bypass the resistance due to mutations in the DNA gyrase enzyme. These sites can be exploited for the identification of new scaffolds for the development of novel antibacterial compounds.

MurC ligase of multi-drug resistant Salmonella Typhi can be inhibited by novel Curcumin derivative: Evidence from molecular docking and dynamics simulations

Emerging multi-drug resistance in recent Salmonella Typhi isolates, causative agent of enteric Typhoid fever, compelled us to investigate alternative therapeutic strategies. The present study encompassed virtual screening, ADMET screening as well as antibacterial activity prediction to shortlist potent lead molecules whose binding affinities (BAs) were checked against major druggable S. Typhi targets. BA profile revealed a deoxy-tetradeutero- curcumin derivative to be novel bioactive compound having high BA towards UDP-N-acetylmuramate-L-alanine ligase (MurC) protein involved in peptidoglycan synthesis. Molecular docking indicated that our lead {Binding energy (BE)= -8.00 ± 0.02 kcal/mol}could competitively bind to MurC with respect to its natural ligand ATP (BE= -7.65 ± 0.19 kcal/mol). The lead also possessed superior binding and inhibition profile against MurC than other commercial antibiotics. This BE was contributed by Hydrogen (H-) bonds and numerous non-canonical interactions with the evolutionary conserved active-site residues. From molecular docking and coarse-grained dynamics simulations, it was inferred that the novel curcumin derivative was predicted to be potential competitive inhibitor of ATP for MurC-catalytic domain having low relative RMSF (0.59 Å) to inhibit MurC-induced peptidoglycan biosynthesis. The inferences drawn from the study can open new portals for designing efficient therapeutic strategies against S. Typhi.

Evaluation of Antimicrobial Susceptibility Profile in Salmonella Typhi and Salmonella Paratyphi A: Presenting the Current Scenario in India and Strategy for Future Management

Background

Systematic studies to estimate the disease burden of typhoid and paratyphoid in India are limited. Therefore, a multicenter study on the Surveillance of Enteric Fever in India was carried out to estimate the incidence, clinical presentation, and antimicrobial resistance (AMR) trend. The data presented here represent the national burden of AMR in Salmonella Typhi and Salmonella Paratyphi A.

Methods

Antimicrobial susceptibility testing was performed for S. Typhi and S. Paratyphi A (n = 2373) isolates collected prospectively during a 2-year period from November 2017 to January 2020.

Results

Of 2373 Salmonella isolates, 2032 (85.6%) were identified as S. Typhi and 341 (14.4%) were S. Paratyphi A. Approximately 2% of S. Typhi were multidrug-resistant (MDR), whereas all 341 (100%) of S. Paratyphi A isolates were sensitive to the first-line antimicrobials. Among 98% of ciprofloxacin nonsusceptible isolates, resistance (minimum inhibitory concentration [MIC] >0.5 µg/mL) was higher in S. Typhi (37%) compared with S. Paratyphi A (20%). Azithromycin susceptibility was 99.9% and 100% with a mean MIC of 4.98 μg/mL for S. Typhi and 7.39 μg/mL for S. Paratyphi A respectively. Ceftriaxone was the only agent that retained 100% susceptibility. Moreover, beta-lactam/beta-lactamase inhibitors showed potent in vitro activity against the study isolates.

Conclusions

Data obtained from this systematic surveillance study confirms the declining trend of MDR Salmonella isolates from India. The higher prevalence of ciprofloxacin nonsusceptibility enforces to limit its use and adhere to the judicious usage of azithromycin and ceftriaxone for enteric fever management.

Structure based drug discovery and in vitro activity testing for DNA gyrase inhibitors of Salmonella enterica serovar Typhi

The emerged resistance in Typhoidal Salmonella has limited the treatment options for typhoid fever. In this scenario, there is a need to find alternate treatment modalities against this pathogen. Amongst the therapeutic agents currently being used to treat enteric fever, quinolones have enjoyed considerable success since past three decades. These drugs act upon DNA gyrase and the acquired resistance is due to mutations at Ser83 and Asp87 of gyrase A subunit. In the present study DNA gyrase enzyme was targeted to seek out potential new inhibitors which are not affected by these mutations. Molecular modelling and docking studies were performed in Schrödinger's molecular modelling software. Homology model of DNA gyrase-DNA complex was built using templates 1AB4 and 3LTN. Molecular dynamic simulations were performed in SPC solvent for 100 ns. Total 17,900,742 drug like molecules were downloaded from ZINC library of chemical compounds. The Glide XP score of the compounds ranged from -5.285 to -13.692. All the ligands bound at the four base pair staggered nick in the DNA binding groove of DNA gyrase enzyme with their aromatic rings intercalating between the bases of two successive nucleotides stabilized by π - π stacking interactions. The binding pocket of DNA gyrase B comprising conserved residues Lys 447, Gly 448, Lys 449, Ile 450, Leu 451, Gln 465 and Val 467 interacts with the ligand molecules through van der Waals interactions. The MIC (minimum inhibitory concentration), MBC (minimum bactericidal concentration) and IC₅₀ of the tested compounds ranged from 500 to 125 mg/L, 750 to 500 mg/L and 100 to 12.5 mg/L, respectively. The selected hits bind to quinolone binding pocket, but their mode of binding and conformation is different to fluoroquinolones, and hence, their binding is not affected by mutations at Ser83 or Asp87 positions. These lead compounds can be further explored as a scaffold to design inhibitors against DNA gyrase to bypass quinolone resistance.

Changes in antimicrobial resistance and molecular attributes of Salmonellae causing enteric fever in Kolkata, India, 2014-2018

Globally, enteric fever caused by Salmonella Typhi (S. Typhi, ST) and S. Paratyphi A (SPA) remain one of the major diseases of public health importance. In this study, a total of 457 (380 ST, 77 SPA) blood isolates were collected from three tertiary care hospitals in Kolkata during 2014-18. Additionally, 66 (3.4%) ST and 5 (0.25%) SPA were recovered from blood culture of 1962 patients attending OPD of one pediatric hospital during 2016-18. The study isolates were tested for antimicrobial resistance (AMR) profiles; AMR genes; molecular sub-types by PFGE, MLVA and CRISPR. Among the total 446 ST and 82 SPA isolates, fluoroquinolone (FQ) resistance was very common in both serovars. Ciprofloxacin resistance of 24.9% and 9.8% & ofloxacin resistance of 20.9% and 87.8% were found in ST and SPA respectively. Majority (>70%) of the isolates showed decreased susceptibility to ciprofloxacin (DCS). A single point mutation in gyrA gene (S83F) was responsible for causing DCS in 37.5% (n = 42/112) ST and 63% (n = 46/73) SPA isolates. Multidrug resistance (MDR) was found only in 3.4% ST isolates and encoded the genes bla_TEM-1, catA, sul, strA-strB, class 1 integron with dfrA7. All MDR ST (n = 15) possessed non-conjugative non-IncHI1 (180 kb) plasmid except one having conjugative IncHI1 (230 kb) plasmid and one without plasmid. The MDR genes were integrated near chromosomal cyaA gene site in ST with/without the presence of plasmid (nonIncH1). Almost 65.7% resistant ST belonged to H58 haplotype. PFGE showed clonally related isolates with 81% similarity in ST and 87% in SPA. Similarly, CRISPR typing showed less diversity among the isolates. However, the isolates (ST and SPA) were found to be more diverse by MLVA typing (D value 0.987 and 0.938). The study reports decrease in MDR and increase in FQ resistance among typhoidal Salmonella isolates over the years giving interesting information for enteric fever treatment.

Genomic profiling of antimicrobial resistance genes in clinical isolates of Salmonella Typhi from patients infected with Typhoid fever in India

The development of multidrug resistance in Salmonella enterica serovar Typhi currently forms a major roadblock for the treatment of enteric fever. This poses a major health problem in endemic regions and extends to travellers returning from developing countries. The appearance of fluoroquinolone non-susceptible strains has resulted in use of ceftriaxone as drug of choice with azithromycin being recommended for uncomplicated cases of typhoid fever. A recent sporadic instance of decreased susceptibility to the latest drug regime has necessitated a detailed analysis of antimicrobial resistance genes and possible relationships with their phenotypes to facilitate selection of future treatment regimes. Whole genome sequencing (WGS) was conducted for 133 clinical isolates from typhoid patients. Sequence output files were processed for pan-genome analysis and prediction of antimicrobial resistance genes. The WGS analyses disclosed the existence of fluoroquinolone resistance conferring mutations in gyrA, gyrB, parC and parE genes of all strains. Acquired resistance determining mechanisms observed included catA1 genes for chloramphenicol resistance, dfrA7, dfrA15, sul1 and sul2 for trimethoprim-sulfamethoxazole and bla_TEM-116/bla_TEM-1B genes for amoxicillin. No resistance determinants were found for ceftriaxone and cefixime. The genotypes were further correlated with their respective phenotypes for chloramphenicol, ampicillin, co-trimoxazole, ciprofloxacin and ceftriaxone. A high correlation was observed between genotypes and phenotypes in isolates of S. Typhi. The pan-genome analysis revealed that core genes were enriched in metabolic functions and accessory genes were majorly implicated in pathogenesis and antimicrobial resistance. The pan-genome of S. Typhi appears to be closed (B_pan  =  0.09) as analysed by Heap’s law. Simpson’s diversity index of 0.51 showed a lower level of genetic diversity among isolates of S. Typhi. Overall, this study augments the present knowledge that WGS can help predict resistance genotypes and eventual correlation with phenotypes, enabling the chance to spot AMR determinants for fast diagnosis and prioritize antibiotic use directly from sequence.

Azithromycin resistance mechanisms in typhoidal salmonellae in India: A 25 years analysis

Background & objectives

: Azithromycin has been in use as an alternate treatment option for enteric fever even when the guidelines on the susceptibility testing were not available. There is lack of data on susceptibility and mechanisms of resistance of azithromycin in Salmonella Typhi and S. Paratyphi A. The aim of the present study was to determine the azithromycin susceptibility and resistance mechanisms in typhoidal salmonellae isolates archived in a tertiary care centre in north India for a period of 25 years.

Methods

: Azithromycin susceptibility was determined in 602 isolates of S. Typhi (469) and S. Paratyphi A (133) available as archived collection isolated during 1993 to 2016, by disc diffusion and E-test method.PCR was done for ereA, ermA, ermB, ermC, mefA, mphA and msrA genes from plasmid and genomic DNA and sequencing was done to detect mutations in acrR, rplD and rplV genes.

Results

: Azithromycin susceptibility was seen in 437/469 [93.2%; 95% confidence interval (CI), 90.5 to 95.1%] isolates of S. Typhi. Amongst 133 isolates of S. Paratyphi A studied, minimum inhibitory concentration (MIC) of ≤16 mg/l was found in 102 (76.7%; 95% CI, 68.8 to 83.0). MIC value ranged between 1.5 and 32 mg/l with an increasing trend in MIC₅₀and MIC₉₀with time. Mutations were found in acrR in one and rplV in two isolates of S. Typhi. No acquired mechanism for macrolide resistance was found.

Interpretation & conclusions

: Azithromycin could be considered as a promising agent against typhoid fever on the basis of MIC distribution in India. However, due to emergence of resistance in some parts, there is a need for continuous surveillance of antimicrobial susceptibility and resistance mechanisms. There is also a need to determine the breakpoints for S. Paratyphi A.

A Systematic Review and Meta-analysis of the Prevalence of Community-Onset Bloodstream Infections among Hospitalized Patients in Africa and Asia

Community-onset bloodstream infections (CO-BSI) are major causes of severe febrile illness and death worldwide. In light of new data and the growing problem of antimicrobial resistance (AMR) among pathogens causing BSI, we undertook a systematic review of hospital-based studies of CO-BSI among patients hospitalized with fever.

Community-onset bloodstream infections (CO-BSI) are major causes of severe febrile illness and death worldwide. In light of new data and the growing problem of antimicrobial resistance (AMR) among pathogens causing BSI, we undertook a systematic review of hospital-based studies of CO-BSI among patients hospitalized with fever. Without restriction to language or country, we searched PubMed, Web of Science, and Scopus for prospective hospital-based studies of culture-confirmed CO-BSI among febrile inpatients. We determined by study the prevalence of BSI among participants, the pathogens responsible for BSI, and the antimicrobial susceptibility patterns of pathogens causing BSI, according to place and time. Thirty-four (77.3%) of 44 eligible studies recruited 29,022 participants in Africa and Asia combined. Among participants in these two regions, the median prevalence of BSI was 12.5% (range, 2.0 to 48.4%); of 3,220 pathogens isolated, 1,119 (34.8%) were Salmonella enterica, 425 (13.2%) Streptococcus pneumoniae, and 282 (8.8%) Escherichia coli. Antimicrobial susceptibility testing was reported in 16 (36.4%) studies. When isolates collected prior to 2008 were compared to those collected in the period of 2008 through 2018, the proportions of typhoidal Salmonella and Staphylococcus aureus isolates resistant to several clinically relevant antimicrobials increased over time, while S. pneumoniae susceptibility was stable. CO-BSI remain a major cause of severe febrile illness among hospitalized patients in Africa and Asia, with S. enterica, S. pneumoniae, and E. coli predominating. There is a concerning increase in AMR among serious infections caused by community-onset pathogens. Ongoing surveillance is needed to inform empirical management and strategies to control AMR.

A systematic review of antimicrobial resistance of typhoidal Salmonella in India

Background & objectives:

The temporal trends in the development of antimicrobial resistance (AMR) among Salmonella Typhi and Salmonella Paratyphi in India have not been systematically reported. We aimed to systematically review the temporal AMR trends (phenotypic and molecular mechanisms) in bacterial isolates from patients with enteric fever over two decades in India.

Methods:

To identify trends in AMR in India, resistance patterns among 4611 individual S. Typhi isolates and 800 S. Paratyphi A isolates, reported from 1992 to 2017 in 40 publications, were analysed. Molecular resistance determinants were extracted from 22 publications and also reviewed in accordance with the PRISMA guidelines. Articles were sourced using a predefined search strategy from different databases.

Results:

The analyses suggested that multidrug-resistant (MDR) enteric fever was declining in India and being replaced by fluoroquinolone (FQ) resistance. Mutations in gyrA and parC were key mechanisms responsible for FQ resistance, whereas MDR was largely driven by resistance determinants encoded on mobile genetic elements (plasmids, transposons).

Interpretation & conclusions:

The results reflect the effect of antimicrobial pressure which has been driving AMR in typhoidal Salmonella in India. Understanding these trends is important in planning future approaches to therapy, which serve as a baseline for assessment of the impact of new typhoid conjugate vaccines against these resistant organisms.

Current antibiotic use in the treatment of enteric fever in children

Background & objectives

Antimicrobial resistance is a major challenge in the treatment of typhoid fever with limited choices left to empirically treat these patients. The present study was undertaken to determine the current practices of antibiotic use in children attending a tertiary care hospital in north India.

Methods

This was a descriptive observational study in children suffering from enteric fever as per the case definition including clinical and laboratory parameters. The antibiotic audit in hospitalized children was measured as days of therapy per 1000 patient days and in outpatient department (OPD) as antibiotic prescription on the treatment card.

Results

A total of 128 children with enteric fever were included in the study, of whom, 30 were hospitalized and 98 were treated from OPD. The mean duration of fever was 9.5 days at the time of presentation. Of these, 45 per cent were culture positive with Salmonella Typhi being aetiological agent in 68 per cent followed by S. Paratyphi A in 32 per cent. During hospitalization, the average length of stay was 10 days with mean duration of defervescence 6.4 days. Based on antimicrobial susceptibility ceftriaxone was given to 28 patients with mean duration of treatment being six days. An additional antibiotic was needed in six patients due to clinical non-response. In OPD, 79 patients were prescribed cefixime and additional antibiotic was needed in five during follow up visit.

Interpretation & conclusions

Based on our findings, ceftriaxone and cefixime seemed to be the first line of antibiotic treatment for typhoid fever. Despite susceptibility, clinical non-response was seen in around 10 per cent of the patients who needed combinations of antibiotics.

Antimicrobial susceptibility profile & resistance mechanisms of Global Antimicrobial Resistance Surveillance System (GLASS) priority pathogens from India

Antimicrobial resistance is a major concern globally. Infections due to drug-resistant pathogens are becoming difficult and a challenge to treat. As treatment choices are limited due to the high-drug resistance rates, there is an increase in the health care cost, duration of hospital stay, morbidity and mortality rates. Understanding the true burden of antimicrobial resistance for a geographical location is important to guide effective empirical therapy. To have a national data, it is imperative to have a systemic data capturing across the country through surveillance studies. Very few surveillance studies have been conducted in India to generate national data on antimicrobial resistance. This review aims to report the cumulative antibiogram and the resistance mechanisms of Global Antimicrobial Resistance Surveillance System (GLASS) priority pathogens from India.

Establishing Antimicrobial Resistance Surveillance & Research Network in India: Journey so far

The Indian Council of Medical Research, in 2013, initiated the Antimicrobial Resistance Surveillance & Research Network (AMRSN) to enable compilation of data on six pathogenic groups on antimicrobial resistance from the country. The overarching aim of this network was to understand the extent and pattern of antimicrobial resistance (AMR) and use this evidence to guide strategies to control the spread of AMR. This article describes the conception and implementation of this AMR surveillance network for India. Also described are the challenges, limitations and benefits of this approach. Data from the Network have shown increasing resistance in Gram-negative bacteria in the hospitals that are part of this network. Combined resistance to third-generation cephalosporins and fluoroquinolones and increasing carbapenem resistance are worrisome, as it has an important bearing on the patients’ outcome and thus needs to be addressed urgently. Data generated through this Network have been used to develop treatment guidelines, which will be supportive in harmonizing treatment practices across the tertiary level healthcare institutions in the country. While, the major benefit of having a surveillance system is the collection of real-time accurate data on AMR including the mechanisms of resistance, representativeness to community, sustaining the current effort and expanding the current activities to next levels of healthcare settings are the major challenges. The data emanating from the network besides providing evidence, expose several gaps and lacunae in the ecosystem and highlight opportunities for action by multiple stakeholders.

Simultaneous and high sensitive detection of Salmonella typhi and Salmonella paratyphi a in human clinical blood samples using an affordable and portable device

Enteric fever is one of the leading causes of infection and subsequent fatality (greater than 1.8 million) (WHO 2018), especially in the developing countries due to contaminated water and food inter twinned with unhygienic practices. Clinical gold standard technique of culture-based method followed by biochemical tests demand 72+ hours for diagnosis while newly developed techniques (like PCR, RT-PCR, DNA microarray etc.) suffer from high limit of detection or involve high-cost infrastructure or both. In this work, a quick and highly specific method, SMOL was established for simultaneous detection of Salmonella paratyphi A and Salmonella typhi in clinical blood samples. SMOL consists of (i) pre-concentration of S. typhi and S. paratyphi A cells using magnetic nanoparticles followed by (ii) cell lysis and DNA extraction (iii) amplification of select nucleic acids by LAMP technique and (iv) detection of amplified nucleic acids using an affordable portable device (costs less than $70). To identify the viability of target cells at lower concentrations, the samples were processed at two different time periods of t = 0 and t = 4 h. Primers specific for the SPA2539 gene in S. paratyphi A and STY2879 gene in S. typhi were used for LAMP. Within 6 h SMOL was able to detect positive and negative samples from 55 human clinical blood culture samples and detect the viability of the cells. The results were concordant with culture and biochemical tests as well as by qPCR. Statistical power analysis yielded 100%. SMOL results were concordant with culture and biochemical tests as well as by qPCR. The sensitive and affordable system SMOL will be effective for poor resource settings.

Multidrug resistant enteric fever in South Asia: unmet medical needs and opportunities

Investments in newer diagnostics and antimicrobial treatments are critical to improve management of enteric fever in South Asia, say Christopher Parry and colleagues

Epidemiological Profile and Antimicrobial Resistance Pattern of Enteric Fever in a Tertiary Care Hospital of North India – a Seven Year Ambispective Study

Introduction: Enteric-fever is a major public-health problem in developing countries emerging as multidrug-resistant, Nalidixic-acid resistant and extremely drug-resistant Salmonella (Pakistan, 2016), has intensified the use of WHO watch/reserve group antimicrobials such as azithromycin and meropenem. Methods: This ambispective-study was conducted on 782 non-repeat blood-culture isolates of S. Typhi, S. Paratyphi A and S. Paratyphi B obtained from 29,184 blood cultures received at a 1000-bedded tertiary-care hospital of North-India from 2011–2017. Identification and antibiograms were obtained by Vitek-2 compact and Kirby-Bauer’s disc diffusion with resistance to ampicillin, chloramphenicol and cotrimoxazole being labeled as multidrug-resistant. Decreased ciprofloxacin-susceptibility and ciprofloxacin-resistance were defined as MIC 0.125–0.5 and >1 μg/ml. Results: S. Typhi and S. Paratyphi A in a ratio of 3.9:1 were seen between July–September predominantly distributed between 6–45 year age group. Resistance to co-trimoxazole, chloramphenicol, ceftriaxone and azithromycin was 6.1%, 13.8%, 16.1 and 5.78% respectively. Multidrug-resistant S. typhi and S. paratyphi A were 2.73% and 1.91% respectively. Conclusion: Enteric-fever is a major public-health problem in India. Emergence of multidrug-resistant, Nalidixic-acid resistant and extremely-drug resistant Salmonella mandates ongoing surveillance for targeted empirical therapy and containment of spread. Repeated epidemics call for water, sanitation, hygiene and vaccination strategies to sustain herd-immunity.

Changing trends of culture-positive typhoid fever and antimicrobial susceptibility in a tertiary care North Indian Hospital over the last decade

Purpose

The present study was undertaken to analyse the trend in prevalence of culture-positive typhoid fever during the last decade and to determine antimicrobial susceptibility profile of Salmonella Typhi and Salmonella Paratyphi A isolated from patients of enteric fever presenting to our hospital.

Methods

All the culture-positive enteric fever cases during 2005-2016 presenting to our Hospital were included in the study. Antimicrobial susceptibility was done against chloramphenicol, amoxicillin, co-trimoxazole, ciprofloxacin, ofloxacin, levofloxacin, pefloxacin, ceftriaxone and azithromycin as per corresponding CLSI guidelines for each year. We also analysed the proportion of culture positivity during 1993-2016 in light of the antibiotic consumption data from published literature.

Results

A total of 1066 strains-S. Typhi (772) and S. Paratyphi A (294) were isolated from the blood cultures during the study. A maximum number of cases were found in July-September. Antimicrobial susceptibility for chloramphenicol, amoxicillin and co-trimoxazole was found to be 87.9%, 75.5%, 87.3% for S. Typhi and 94.2%, 90.1% and 94.2% for S. Paratyphi A, respectively. Ciprofloxacin, ofloxacin and levofloxacin susceptibility were 71.3%, 70.8% and 70.9% for S. Typhi and 58.1%, 57.4% and 57.1% for S. Paratyphi A, respectively. Azithromycin susceptibility was 98.9% in S. Typhi. Although susceptibility to ceftriaxone and cefixime was 100% in our isolates, there is a continuous increase in ceftriaxone minimum inhibitory concentration (MIC)₅₀and MIC₉₀values over the time. The proportion of blood culture-positive cases during 1993-2016 ranged from a minimum of 0.0006 in 2014 to a maximum of 0.0087 in 1999.

Conclusion

We found that the most common etiological agent of enteric fever is S. Typhi causing the majority of cases from July to October in our region. MIC to ceftriaxone in typhoidal salmonellae is creeping towards resistance and more data are needed to understand the azithromycin susceptibility.

Typhoid fever: issues in laboratory detection, treatment options & concerns in management in developing countries

Multidrug-resistant Salmonella enterica subsp. enterica serovar Typhi (resistant to ampicillin, chloramphenicol and cotrimoxazole), was significantly reduced with the increased usage of fluoroquinolones and azithromycin. This has led to declining multidrug resistance rates in India with increasing ciprofloxacin nonsusceptibility rates and clinical failures due to azithromycin. However, for the available agents such as ceftriaxone, azithromycin and fluoroquinolones, the dose and duration for treatment is undefined. The ongoing clinical trials for typhoid management are expected to recommend the defined dose and duration for better clinical outcome. We made an attempt to summarize the issues in laboratory detection, treatment options and responses, and the concerns in clinical practice seen in the developing countries.

Typhoid fever is an important cause of mortality in developing countries and is a major public health concern. Cephalosporins or azithromycin are the drugs of choice for treating infection caused by the reduced fluoroquinolone susceptibility of S. Typhi. Emergence of cephalosporin resistance in S. Typhi and azithromycin-associated clinical and microbiological failure is of significant concern in developing countries. An approach of cephalosporin–azithromycin combination therapy has been suggested, which could be a potential alternative in treating uncomplicated S. Typhi infection in endemic areas. This review summarizes the field so far.

Highly-sensitive detection of Salmonella typhi in clinical blood samples by magnetic nanoparticle-based enrichment and in-situ measurement of isothermal amplification of nucleic acids

Enteric fever continues to be a major cause of mortality and morbidity globally, particularly in poor resource settings. Lack of rapid diagnostic assays is a major driving factor for the empirical treatment of enteric fever. In this work, a rapid and sensitive method ‘Miod^’ ‘has been developed. Miod includes a magnetic nanoparticle-based enrichment of target bacterial cells, followed by cell lysis and loop-mediated isothermal amplification (LAMP) of nucleic acids for signal augmentation along with concurrent measurement of signal via an in–situ optical detection system. To identify positive/negative enteric fever infections in clinical blood samples, the samples were processed using Miod at time = 0 hours and time = 4 hours post-incubation in blood culture media. Primers specific for the STY2879 gene were used to amplify the nucleic acids isolated from S. typhi cells. A limit of detection of 5 CFU/mL was achieved. No cross-reactivity of the primers were observed against 10⁶ CFU/mL of common pathogenic bacterial species found in blood such as E. coli, P. aeruginosa, S. aureus, A. baumanni, E. faecalis, S. Paratyphi A and K. pneumonia. Miod was tested on 28 human clinical blood samples. The detection of both pre-and post-four-hours incubation confirmed the presence of viable S. typhi cells and allowed clinical correlation of infection. The positive and negative samples were successfully detected in less than 6 hours with 100% sensitivity and specificity.

Detection of blaCTX-M Extended Spectrum Beta-lactamase Producing Salmonella enterica Serotype Typhi in a Tertiary Care Centre

Introduction

Infections caused by Salmonella are an important public health threat in tropical and subtropical countries. Due to the emergence of resistance to ampicillin, chloramphenicol and trimethoprim/sulfamethoxazole (multidrug resistant salmonellae) in the late 1980s, fluoroquinolones and extended spectrum cephalosporins became the drugs of choice. Resistance to cefotaxime and ceftriaxone due to the production of Extended Spectrum Beta-Lactamase (ESBL) and reduced susceptibility to ciprofloxacin have emerged resulting in treatment failure. The Cefotaximase (CTX-M) type ESBLs are the most widespread beta lactamase among Enterobacteriaceae including salmonellae.

Aim

To detect the presence of bla_CTX-M in salmonellae causing human infections. Detection of qnr genes to identify the coexistence of bla_CTX-M and qnr gene.

Materials and Methods

The study included 103 consecutive, non-repetitive salmonellae isolated from clinical specimens obtained from July 2015- June 2016 which were identified up to species level by conventional/automated methods. Susceptibility to various classes of antimicrobial agents was determined by disc diffusion method. Minimum Inhibitory Concentration (MIC) to cefotaxime and ceftriaxone was determined by agar dilution method. The results were interpreted in accordance with Clinical & Laboratory Standard Institute (CLSI) (guidelines 2015. Detection of the ESBL phenotype was performed by the combined disk method. Polymerase Chain Reaction (PCR) amplification of all isolates was performed using group specific primers to characterize the presence of bla_CTX-M, qnrA, qnrB and qnrS.

Result

Of the 103 study isolates two isolates of Salmonella typhi were resistant to cefotaxime and ceftriaxone and had a MIC of 128μg/ml. PCR amplification and sequencing detected the presence of bla_CTX-M-15 in these two isolates. These two isolates exhibited resistance to ciprofloxacin in vitro but qnr gene was not detected in these isolates.

Conclusion

Resistance to third generation cephalosporins among salmonellae is a cause for concern as it may lead to treatment failure. It is imperative to continuously monitor the susceptibility pattern as enteric fever is endemic in India.