Ceftriaxone resistant Salmonella enterica serovar Paratyphi A identified in a case of enteric fever: first case report from Pakistan.

BACKGROUND: Enteric fever is an acute systemic infectious disease associated with substantial morbidity and mortality in low- and middle-income countries (LMIC), with a global burden of 14.3 million cases. Cases of enteric fever or paratyphoid fever, caused by Salmonella enterica serovar Paratyphi A (S. Para A) have been found to rise in many endemic and non-endemic countries. Drug resistance is relatively uncommon in S. Para A. Here we report a case of paratyphoid fever caused by ceftriaxone resistant S. Para A from Pakistan. CASE PRESENTATION: A 29-year-old female presented with a history of fever, headache, and shivering. Her blood culture revealed a S. Para A isolate (S7), which was resistant to ceftriaxone, cefixime, ampicillin and ciprofloxacin. She was prescribed oral Azithromycin for 10 days, which resulted in resolution of her symptoms. Two other isolates of S. Para A (S1 and S4), resistant to fluoroquinolone were also selected for comparison. DST and whole genome sequencing was performed for all three isolates. Sequence analysis was performed for identification of drug resistance and phylogeny. Whole Genome Sequencing (WGS) of S7 revealed the presence of plasmids, IncX4 and IncFIB(K). blaCTX-M-15 and qnrS1 genes were found on IncFIB(K). The gyrA S83F mutation conferring fluoroquinolone resistance was also found present. Multi-locus sequence typing (MLST) showed the S7 isolate to belong to ST129. S1 and S4 had the gyrA S83Y and S83F mutations respectively. CONCLUSIONS: We highlight the occurrence of plasmid-mediated ceftriaxone resistant strain of S. Para A. This is of significance as ceftriaxone is commonly used to treat paratyphoid fever and resistance in S. Para A is not known. Continuous epidemiological surveillance is required to monitor the transmission and spread of antimicrobial resistance (AMR) among Typhoidal Salmonellae. This will guide treatment options and preventive measures including the need for vaccination against S. Para A in the region.

Extraintestinal Seeding of Salmonella enterica Serotype Typhi, Pakistan.

We evaluated Salmonella enterica serotype Typhi strains isolated from all body sites in Pakistan during 2013-2018. Despite an increase in overall number of localized, extensively drug-resistant Salmonella Typhi in organ infections during 2018, there was no increase in the proportion of such isolates in comparison with non-extensively drug-resistant isolates.

Prevalence and risk factors associated with multi-drug resistant organisms (MDRO) carriage among pediatric patients at the time of admission in a tertiary care hospital of a developing country. A cross-sectional study.

BACKGROUND: The rise of Multidrug-resistant organisms (MDROs) poses a considerable burden on the healthcare systems, particularly in low-middle income countries like Pakistan. There is a scarcity of data on the carriage of MDRO particularly in the pediatrics population therefore, we aimed to determine MDRO carriage in pediatric patients at the time of admission to a tertiary care hospital in Karachi, Pakistan, and to identify the risk factors associated with it. METHODS: A cross-sectional study conducted at the pediatric department of Aga Khan University Hospital (AKUH) from May to September 2019 on 347 children aged 1-18 years. For identification of MDRO (i.e., Extended Spectrum Beta-Lactamase (ESBL) producers, Carbapenem Resistant Enterobacteriaceae (CRE), Vancomycin Resistant Enterococci (VRE), Methicillin Resistant Staphylococcus aureus (MRSA), Multidrug-resistant (MDR) Acinetobacter species and MDR Pseudomonas aeruginosa), nasal swabs and rectal swabs or stool samples were cultured on specific media within 72 h of hospitalization. Data was collected on a predesigned structured questionnaire on demographics, prior use of antibiotics for > 48 h in the last 6 months, history of vaccination in last 6 months, exposure to health care facility regardless of the time of exposure, ICU stay for > 72 h, and about the prior use of medical devices (urinary catheter, central venous lines etc.) in last 1 year. Statistical analysis was performed by Standard statistical software. RESULTS: Out of 347 participants, 237 (68.3%) were found to be MDRO carriers. Forty nine nasal swabs from 346 children (14.2%) showed growth of MRSA. The majority of the stool/rectal swabs (n = 222 of 322; 69%) collected were positive for MDRO. The most isolated species were ESBL Escherichia coli 174/222 (78.3%) followed by ESBL Enterobacter species 37/222 (16.7%) and ESBL Klebsiella pneumoniae 35/222 (15.8%). On univariate analysis, none of the risk factors showed statistically significant association with MDRO carriage. CONCLUSION: Overall, a high prevalence of MDRO carriage was identified among admitted pediatric patients. Implementation of systematic screening may help to identify true burden of MDROs carriage in the health care settings.

Increase in Penicillin and multidrug resistance in Streptococcus pneumoniae (1993-2016): Report from a tertiary care hospital laboratory, Pakistan.

OBJECTIVE: To determine the trend of resistance to antimicrobials in Streptococcus pneumoniae infections, and the impact of new Clinical and Laboratory Standards Institute guidelines on 1211 among meningeal isolates. METHODS: The descriptive observational retrospective study was conducted at the Aga Khan University Hospital laboratory in Karachi, and comprised Streptococcus pneumoniae isolation and antimicrobial susceptibility data over a period of 24 years, from 1993 to 2016, which was compared in terms of pre-2008 and post-2008 data, which was analysed using SPSS 19. RESULTS: Of the 7415 non-duplicate isolates identified, 4700(63.4%) were from male patients and 2,715(36.6%) were from female patients. The overall mean age of the patients was 38±27 years. Penicillin resistance in non-meningeal isolates during the two periods was not significantly different (p>0.05), but a significant rise in penicillin resistance in meningeal isolates was observed in the second period (p<0.05). High resistance rates were observed for co-trimoxazole, tetracycline and erythromycin, and an increased trend of multi-drug resistant strains was also noted from 1999 {n=35/317(11%)} to 2016 {n=110/314 (36%)}. CONCLUSIONS: The emergence of multi-drug resistant strains was evident. The spike in penicillin-resistant Streptococcus pneumoniae in meningeal isolates may have been due to the revised guidelines by the Clinical and Laboratory Standards Institute.

Burden of Culture Confirmed Enteric Fever Cases in Karachi, Pakistan: Surveillance For Enteric Fever in Asia Project (SEAP), 2016-2019.

BACKGROUND: The Surveillance for Enteric Fever in Asia Project (SEAP) is a multicenter, multicountry study conducted in Pakistan, Nepal, and Bangladesh. The objectives of the study were to characterize disease incidence among patients with enteric fever. We report the burden of enteric fever at selected sites of Karachi, Pakistan. METHODS: During September 2016 to September 2019, prospective surveillance was conducted at inpatient, outpatient, surgical departments, and laboratory networks of Aga Khan University Hospital, Kharadar General Hospital, and surgery units of National Institute of Child Health and Jinnah Postgraduate Medical Centre. Socio-demographic, clinical, and laboratory data were obtained from all suspected or confirmed enteric fever cases. RESULTS: Overall, 22% (2230/10 094) of patients enrolled were culture-positive for enteric fever. 94% (2093/2230) of isolates were Salmonella Typhi and 6% (137/2230) were S. Paratyphi. 15% of isolates multi-drug resistant (MDR) to first-line antibiotics and 60% were extensively drug-resistant (XDR), resistant to first-line antibiotics, fluoroquinolones and third generation cephalosporin. CONCLUSION: Enteric fever cases have increased during the last 3 years with large proportion of drug resistant S. Typhi cases. However, the burden of paratyphoid is still relatively low. Strengthening the existing surveillance system for enteric fever and antimicrobial resistance at the national level is recommended in Pakistan to inform prevention measures. While typhoid vaccination can significantly decrease the burden of typhoid and may also impact antimicrobial resistance, water, sanitation, and hygiene improvement is highly recommended to prevent the spread of enteric fever.

Antimicrobial Resistance in Typhoidal Salmonella: Surveillance for Enteric Fever in Asia Project, 2016-2019.

BACKGROUND: Clinicians have limited therapeutic options for enteric as a result of increasing antimicrobial resistance, and therefore typhoid vaccination is recommended as a preventive measure. As a part of the Surveillance for Enteric Fever in Asia Project (SEAP), we investigated the extent measured the burden of antimicrobial resistance (AMR) among confirmed enteric fever cases in Bangladesh, Nepal, and Pakistan. METHODS: From September 2016-September 2019, SEAP recruited study participants of all age groups from its outpatient, inpatient, hospital laboratory, laboratory network, and surgical sites who had a diagnosis of febrile illness that was either suspected or blood culture confirmed for enteric fever. Antimicrobial resistance of isolates was determined by disc diffusion using Clinical and Laboratory Standard Institute cut-off points. We reported the frequency of multidrug resistance (MDR)(resistance to ampicillin, cotrimoxazole, and chloramphenicol), extensive drug resistance (XDR) (MDR plus non-susceptible to fluoroquinolone and any 3rd generation cephalosporins), and fluoroquinolone (FQ) and azithromycin non-susceptibility. RESULTS: We enrolled 8,705 blood culture confirmed enteric fever cases: 4,873 (56%) from Bangladesh, 1,602 (18%) from Nepal and 2,230 (26%) from Pakistan. Of these, 7,591 (87%) were Salmonella Typhi and 1114 (13%) were S. Paratyphi. MDR S. Typhi was identified in 17% (701/4065) of isolates in Bangladesh, and 1% (19/1342) in Nepal. In Pakistan, 16 % (331/2084) of S. Typhi isolates were MDR, and 64% (1319/2074) were XDR. FQ nonsusceptibility among S. Typhi isolates was 98% in Bangladesh, 87% in Nepal, and 95% in Pakistan. Azithromycin non-susceptibility was detected in 77 (2%) in Bangladesh, 9 (.67%) in Nepal and 9 (.59%) isolates in Pakistan. In Pakistan, three (2%) S. Paratyphi isolates were MDR; no MDR S. Paratyphi was reported from Bangladesh or Nepal. CONCLUSIONS: Although AMR against S. Paratyphi was low across the three countries, there was widespread drug resistance among S. Typhi, including FQ non-susceptibility and the emergence of XDR S. Typhi in Pakistan, limiting treatment options. As typhoid conjugate vaccine (TCV) is rolled out, surveillance should continue to monitor changes in AMR to inform policies and to monitor drug resistance in S. Paratyphi, for which there is no vaccine.

Efforts to improve diagnosis of bacteraemia by reducing blood culture contamination in an emergency department: strategies and outcome.

OBJECTIVE: To assess the strategies and outcome for reducing blood culture contamination in order to improve the diagnosis of bacteraemia. METHODS: The interventional study was conducted at a tertiary care hospital in Karachi from January 1, 2013, to December 31, 2016. The blood culture contamination data related to the first year of the study was taken as the baseline pre-intervention data. Strategies were planned as intervention for improvement by consolidating training and education in the form of dedicated lectures, practising on mannequins and developing in-house video, replacing povidone with 2% chlorhexidine preparation spray plus 70% isopropyl alcohol swabs and inducting dedicated phlebotomy team whose only responsibility was blood sample collection and minimising the probability of error. RESULTS: In 2013, there were 8868 samples; 7402 in 2014; 6897 in 2015; and 9756 samples in 2016. The contamination rate in 2013 was 8% which went down to 7.75% in 2014, 4.25% in 2015 and 3.9% in 2016. The decline became statistically significant (p<0.001) after implementing a dedicated phlebotomy team in the emergency department. CONCLUSIONS: Apart from teaching and training, the concept of blood culture collection kit with checklist and dedicated blood collection team was found to be vital in reducing blood culture contamination.

Antimicrobial sensitivity pattern, demographic findings and risk factors amongst meningitis and non-meningitis invasive Streptococcus pneumoniae at Aga Khan University Hospital Clinical Laboratory, Karachi, Pakistan.

OBJECTIVE: To determine the resistance rate of penicillin and ceftriaxone amongst invasive meningitis and nonmeningitis isolates of streptococcus pneumoniae. METHODS: The prospective cross-sectional study was conducted from January 2011 to March 2014 at the Clinical Microbiology Laboratory of Aga Khan University, Karachi, and comprised all invasive strains of streptococcus pneumoniae. Penicillin and ceftriaxone susceptibilities were performed and interpreted based on minimum inhibitory concentration breakpoints recommended by Clinical and Laboratory Standards Institute guidelines. Data was analysed using Stata 12. RESULTS: There were 163 strains isolated from sterile body fluids of 109 patients. Of the total, 46(28%) samples were meningitic while 117(72%) were non-meningitic. Of the meningeal isolates, 12(26%) were resistant to penicillin, while none was resistant to ceftriaxone and vancomycin. None of non meningeal isolates showed resistance to penicillin, ceftriaxone or vancomycin. CONCLUSION: There was considerable penicillin resistance among meningeal strains of streptococcus pneumoniae, but here appeared to be no need to add vancomycin for empirical treatment of invasive streptococcus pneumonia infection.

Microbiological safety of areca nut-containing, ready-to-eat chewing substances common among Pakistani paediatric population: A pilot study.

OBJECTIVE: To evaluate microbiological contamination of areca nut-containing, ready-to-eat chewing substances easily accessible to vulnerable paediatric population. METHODS: A pilot study was conducted at the Aga Khan University Medical College from June to October 2016 on twelve samples of areca nut-containing chewing substances (four supari, paan masala and gutka each) collected from various localities of Karachi. These were evaluated individually for total colony counts, hygiene indicator organisms, pathogenic organisms, and levels of aflatoxin. Microbial contamination was analysed using pour-plate method. Fungal aflatoxin levels were measured by enzyme-linked immunosorbent assay (ELISA).. RESULTS: Wet gutka preparations were contaminated by Escherichia coli and Enterobacteriacaea. High levels of fungal aflatoxin (range: 0.43-1.84 mg/kg), a proven carcinogen, were identified in all the 12(100%) products. No sample contained pathogenic bacteria. However, 1(8.33%) sample did not meet hygiene criteria cut-off. CONCLUSIONS: Habitual use of unhygienic chewing substances containing fungal toxins is a public health concern that needs to be addressed through a preventative, behaviour-changing strategy..

Contamination assessment of orthodontic bands after different pre-cleaning methods at a tertiary care hospital.

INTRODUCTION: Infection control in dentistry is a major concern due to risk of transmission of communicable diseases. The aim of this study is to evaluate and compare the efficacy of various pre-cleaning methods for the tried-in orthodontic bands. MATERIAL AND METHODS: An in-vitro experimental study was conducted at the Central Sterilization Services Department (Dental Clinic) and the Microbiology lab at our university hospital. A total of 130 bands were included in our study which comprised 10 controls and the rest were equally divided into three groups according to the pre-cleaning methods, i.e. manual scrubbing, enzymatic solution and a combination of both. The orthodontic bands were incubated in the brain heart infusion broth at 37 °C for five days after pre-cleaning and sterilisation in a steam autoclave and were assessed for any bacterial growth. The chi-square test was applied to determine any significant association between the various pre-cleaning methods and the frequency of bands that showed growth. Effect size was calculated using the phi coefficient. RESULTS: The enzyme method revealed 5% of the sample to exhibit bacterial growth, whereas manual scrubbing and the combination of both showed no growth. There was no statistically significant difference among the three methods (P = 0.131). Further investigations showed the presence of Staphylococcus non-aureus bacterial species in contaminated bands from group II. CONCLUSIONS: All pre-cleaning methods were found to be equally effective in the decontamination of bands. Hence, the tried-in bands can be safely reused after pre-cleaning and sterilisation.

Pelvic abscess caused by a slow growing anaerobic bacterium, Eggerthella lenta: First case report from Pakistan.

We report a case of intrauterine contraceptive device (IUCD) related pelvic abscess caused by a challenging to grow anaerobic Gram positive rod named Eggerthella lenta. A middle aged lady presented with complaints of lower abdomen pain, intermittent vaginal bleeding since two weeks. Ultrasound of abdomen and pelvis showed right adnexal mass involving fallopian tubes, right ovary and gut omentum. She underwent removal of adnexal mass and total abdominal hysterectomy and was treated empirically with vancomycin, ciprofloxacin and metronidazole. Histopathological examination disclosed adenomyosis and chronic non-specific endometritis. Microbiological evaluation of pus aspirate grew Eggerthella lenta.

Dissemination and spread of New Delhi Metallo-beta-lactamase-1 Superbugs in hospital settings.

OBJECTIVE: To find out frequency of isolation of carbapenem-resistant enterobacteriaceae and the predominantly responsible metallo-beta-lactamasegene in a hospital setting. METHODS: The descriptive, cross-sectional study was conducted from May 2009 to June 2012 at the Aga Khan University Hospital, Karachi, and comprised non-duplicate clinical carbapenem-resistant enterobacteriaceae isolates obtained from different collection units across Pakistan. Kirby-Bauer disk diffusion screening of carbapenem-resistant enterobacteriaceae was confirmed by minimum inhibitory concentration using E-test. Polymerase chain reaction assay was performed to detect blaKPC, blaNDM-1, blaIMP, and blaVIM genes. In addition variable number tandem repeat typing was performed on selected cluster of New Delhi metallo-beta-lactamase-1-positive Klebsiella pneumoniae. RESULTS: Of the 114 carbapenem-resistant enterobacteriaceae isolates, 104(94%) tested positive for blaNDM-1 gene. At 68(66%), Klebsiella pneumoniae was the most frequent species isolated, followed by E.coli 33(31%). Moreover, 89(78%) of the blaNDM-1 gene positive Klebsiella pneumonia isolates were from the clinical samples of patients admitted to the critical care units and 75(66%) were from neonates and the elderly. Of the 65(67%) patients suffering from bacteraemia and sepsis, 32(57%) had expired, of which 22(60%) were aged <1 month. Variable number tandem repeat analysis of hospital-acquired New Delhi metallo-beta-lactamase-1-positive Klebsiella pneumoniae showed similarities between the isolates. CONCLUSIONS: New Delhi metallo-beta-lactamase-1-positive enterobacteriaceae was found widely disseminated in major hospitals across Pakistan. Patients at extreme ages and those in critical care units were found to be the most affected with fatal outcomes.

Clinical isolates of Salmonella enterica serovar Agona producing NDM-1 metallo-ß-lactamase: first report from Pakistan.

We report two cases of infantile diarrhea due to multidrug-resistant, NDM-1 metallo-ß-lactamase-producing Salmonella enterica serovar Agona from Pakistan. This study alerts toward possible risk of NDM-1 transmission to enteric fever pathogens and encourages microbiologists to consider active screening of carbapenem resistance in nontyphoidal Salmonella isolates.

Microbiological Evaluation of Commercial Hand Sanitisers Available in Pakistan Using European Standard and Membrane Filtration Method.

OBJECTIVE: To evaluate the antibacterial efficacy of various commercially available alcohol-based hand sanitisers (ABHS) using European standard (EN 1500) method and perform ABHS testing with membrane filtration method. STUDY DESIGN: A Cross-sectional observational study. Place and Duration of the Study: Quality Control Section of the Microbiology Laboratory, The Aga Khan University Hospital, Karachi, Pakistan, from February to April 2023. METHODOLOGY: Efficacy of 14 commercially and widely accessible hand sanitisers was defined as reducing micro-organism growth. It was determined using the EN 1500 European standard test and membrane filtration method. RESULTS: Majority (92.8%) ABHS showed a significant bacterial reduction except one ABHS tested with the EN 1500 method. Only six ABHS products were tested through the membrane filtration method because high viscosity of hand sanitisers was causing damage to filter membranes. CONCLUSION: Continued vigilance in evaluating hand sanitiser's efficacy through robust testing methods is essential to ensure public health and prevent the dissemination of misleading products that may compromise hand hygiene practices. KEY WORDS: Hand sanitisers, European standard, Membrane filtration method, Antibacterial efficacy.

Daptomycin MICs by Broth Microdilution Method Against Staphylococcus aureus in Clinical Specimens: A Cross-Sectional Study from Pakistan.

OBJECTIVE: To explore the distribution of daptomycin (DAP) minimum inhibitory concentrations (MICs) in Staphylococcus aureus isolated from complicated skin, soft tissue, and bloodstream infections collected from the Pakistani population using broth microdilution (BMD). STUDY DESIGN: Descriptive, cross-sectional study. Place and Duration of the Study: Department of Pathology and Laboratory Medicine, The Aga Khan University Hospital, from May to October 2021. METHODOLOGY: Through consecutive sampling techniques, 169 Staphylococcus aureus (S. aureus) isolated from clinical specimens including pus, tissue, and blood were collected. Patients' data including age, gender, geographical location, specimen site, and methicillin susceptibility were collected from the laboratory data. BMD was used to determine MICs of clinical isolates and S. aureus ATCC 29213. DAP MIC ≤1.0 µg/ml was considered susceptible according to the Clinical and Laboratory Standards Institute M100. RESULTS: Among all the clinical isolates, 144 (85%) and 25 (15%) were from skin and soft tissue and blood, respectively. All isolates were susceptible to DAP with MIC50, MIC90, and MIC range of 0.25 µg/ml, 0.5 µg/ml, and 0.06 - 0.5 µg/ml, respectively. CONCLUSION: These study findings demonstrated low in-vitro MICs for DAP against S. aureus in tested isolates from a diverse variety of patient specimens from across Pakistan. KEY WORDS: Daptomycin, Staphylococcus aureus, Broth microdilution, Minimum inhibitory concentrations.

Longevity of immune response following a single dose of typhoid conjugate vaccine against Salmonella Typhi among children in Hyderabad, Pakistan.

OBJECTIVES: Typhoid remains a persistent contributor to childhood morbidity in communities lacking sanitation infrastructure. Typhoid conjugate vaccine (TCV) is effective in reducing disease risk in vaccinees, but the duration of protection is unknown. This study measured the longevity of immune response to TCV in children under 10 years in Hyderabad, Pakistan where an outbreak of extensively drug resistant (XDR) typhoid has been ongoing. METHODS: A subset of children who received the TCV as part of the outbreak response were enrolled purposively from March 2018-February 2019. The participants were followed until January 2023. Blood samples were taken at baseline, 4-6 weeks, 6 months, and annually 1-4 years post-vaccination to measure anti-Vi-IgG levels using ELISA. Active phone-based surveillance was performed to identify breakthrough infections. Blood culture was offered to any child with a history of fever ≥3 days within the last 7 days. 81 children received a second dose of TCV in November 2019 during a catch-up campaign organized by Sindh government. RESULTS: Nearly all participants seroconverted (802/837; 95·8 %) at 4-6 weeks following vaccination. Four years after vaccination, 438/579 (75·6%) participants remained above the seroconversion threshold. The geometric mean titer (GMT, U/ml) of anti-Vi-IgG at 4-6 weeks was 832·6 (95% CI: 768·0, 902·6); at 4 years post-vaccination, the GMTs in children 6 months-2 years (12·6, {95% CI: 9·8, 16·3}), and >2 - 5 years (40·1, {95% CI: 34·4, 46·6}) were lower than in children >5-10 years (71·1, {95% CI: 59·5, 85·0}). During 4 years of follow-up, 9 children had culture-confirmed S. Typhi infection, these infections occurred after a median duration of 3·4 years. All enteric fever cases seroconverted at 4-6 weeks post-vaccination and 7 (70·0%) remained seroconverted four years post-vaccination. CONCLUSION: We observed 95·8% seroconversion following a single dose of TCV. There was decay in anti-Vi-IgG titers, and at four years approximately 75·6% remained seroconverted. There was a faster decay in children ≤2 years. Breakthrough infections were documented after a median 3·4 years following vaccination.

Mixed Salmonella infection: a report of two cases from the Aga Khan University Hospital, Karachi.

Enteric fever remains a major health problem in the developing world, including Pakistan. Poor sanitation and hygienic conditions are the major predisposing factors. Salmonella infection with different strains in the same patient has rarely been reported previously. We are reporting two cases of bacteraemia with simultaneous detection of two strains of Salmonella in a single episode of infection. In both the cases, 2 different serotypes of Salmonella were causing bacteraemia leading to fever. In highly endemic area, one must be aware of mixed Salmonella infections as inappropriate diagnosis of such infections may lead to treatment failure.

Field evaluation of typhoid conjugate vaccine in a catch-up campaign among children aged 9 months to 15 years in Sindh, Pakistan.

BACKGROUND: Typhoid conjugate vaccine (TCV) has recently been introduced in the expanded program for immunization (EPI) in Pakistan. Before its introduction in routine immunization, a onetime catchup campaign among children 9 months to 15 years old was conducted in November 2019. We performed field evaluation of TCV against culture confirmed Salmonella Typhi (S. Typhi) among 9 months to 15 years old children during the catch up campaign in Karachi and Hyderabad. METHODS: A rapid assessment of blood culture confirmed S. Typhi was performed. Age eligible cases of culture confirmed S. Typhi were identified from the laboratory networks of Aga Khan University Hospital Karachi and Hyderabad, Kharadar General Hospital Karachi, and Liaqat University of Medical & Health Sciences (LUMHS) Hyderabad. Information on sociodemographic, typhoid vaccination history and antimicrobial resistance was collected using a structured questionnaire. Patient medical records and lab reports were also reviewed to collect information on diagnosis and antimicrobial susceptibility information. Information about the population vaccination coverage during catch-up campaign was obtained from the provincial EPI office. Field performance of TCV in catchup campaign was measured by calculating the effectiveness using rapid screening method which is less resource-intensive technique of calculating vaccine effectiveness (VE). RESULTS: Overall, 968 culture confirmed typhoid cases were enrolled. Among them, 82% (793/968) were from Karachi and 18% (175/968) from Hyderabad. The average age of the participants was 5.68 years, and 54% (523/968) were male. 6% (62/968) of the culture confirmed S. Typhi cases were multidrug resistant (MDR), and 61% (586/968) were extensively drug resistant (XDR). The VE using the TCV coverage data provided by EPI was 98%. CONCLUSION: TCV is effective against culture confirmed S. Typhi among children aged 9 months to 15 years in the catch-up campaign setting. While typhoid vaccination can significantly decrease the burden of typhoid disease, improvements in sanitation and hygiene are necessary for the prevention of spread of enteric fever. Longer term follow up will be needed to assess the duration of protection and requirement for booster doses of TCV.

The international and intercontinental spread and expansion of antimicrobial-resistant Salmonella Typhi: a genomic epidemiology study.

BACKGROUND: The emergence of increasingly antimicrobial-resistant Salmonella enterica serovar Typhi (S Typhi) threatens to undermine effective treatment and control. Understanding where antimicrobial resistance in S Typhi is emerging and spreading is crucial towards formulating effective control strategies. METHODS: In this genomic epidemiology study, we sequenced the genomes of 3489 S Typhi strains isolated from prospective enteric fever surveillance studies in Nepal, Bangladesh, Pakistan, and India (between 2014 and 2019), and combined these with a global collection of 4169 S Typhi genome sequences isolated between 1905 and 2018 to investigate the temporal and geographical patterns of emergence and spread of antimicrobial-resistant S Typhi. We performed non-parametric phylodynamic analyses to characterise changes in the effective population size of fluoroquinolone-resistant, extensively drug-resistant (XDR), and azithromycin-resistant S Typhi over time. We inferred timed phylogenies for the major S Typhi sublineages and used ancestral state reconstruction methods to estimate the frequency and timing of international and intercontinental transfers. FINDINGS: Our analysis revealed a declining trend of multidrug resistant typhoid in south Asia, except for Pakistan, where XDR S Typhi emerged in 2016 and rapidly replaced less-resistant strains. Mutations in the quinolone-resistance determining region (QRDR) of S Typhi have independently arisen and propagated on at least 94 occasions, nearly all occurring in south Asia. Strains with multiple QRDR mutations, including triple mutants with high-level fluoroquinolone resistance, have been increasing in frequency and displacing strains with fewer mutations. Strains containing acrB mutations, conferring azithromycin resistance, emerged in Bangladesh around 2013 and effective population size of these strains has been steadily increasing. We found evidence of frequent international (n=138) and intercontinental transfers (n=59) of antimicrobial-resistant S Typhi, followed by local expansion and replacement of drug-susceptible clades. INTERPRETATION: Independent acquisition of plasmids and homoplastic mutations conferring antimicrobial resistance have occurred repeatedly in multiple lineages of S Typhi, predominantly arising in south Asia before spreading to other regions. FUNDING: Bill & Melinda Gates Foundation.