Antimicrobial resistance (AMR) is an increasing threat to global health. There are > 14 million cases of enteric fever every year and > 135,000 deaths. The disease is primarily controlled by ...antimicrobial treatment, but this is becoming increasingly difficult due to AMR. Our objectives were to assess the prevalence and geographic distribution of AMR in Salmonella enterica serovars Typhi and Paratyphi A infections globally, to evaluate the extent of the problem, and to facilitate the creation of geospatial maps of AMR prevalence to help targeted public health intervention.
We performed a systematic review of the literature by searching seven databases for studies published between 1990 and 2018. We recategorised isolates to allow the analysis of fluoroquinolone resistance trends over the study period. The prevalence of multidrug resistance (MDR) and fluoroquinolone non-susceptibility (FQNS) in individual studies was illustrated by forest plots, and a random effects meta-analysis was performed, stratified by Global Burden of Disease (GBD) region and 5-year time period. Heterogeneity was assessed using the I
statistics. We present a descriptive analysis of ceftriaxone and azithromycin resistance.
We identified 4557 articles, of which 384, comprising 124,347 isolates (94,616 S. Typhi and 29,731 S. Paratyphi A) met the pre-specified inclusion criteria. The majority (276/384; 72%) of studies were from South Asia; 40 (10%) articles were identified from Sub-Saharan Africa. With the exception of MDR S. Typhi in South Asia, which declined between 1990 and 2018, and MDR S. Paratyphi A, which remained at low levels, resistance trends worsened for all antimicrobials in all regions. We identified several data gaps in Africa and the Middle East. Incomplete reporting of antimicrobial susceptibility testing (AST) and lack of quality assurance were identified.
Drug-resistant enteric fever is widespread in low- and middle-income countries, and the situation is worsening. It is essential that public health and clinical measures, which include improvements in water quality and sanitation, the deployment of S. Typhi vaccination, and an informed choice of treatment are implemented. However, there is no licenced vaccine for S. Paratyphi A. The standardised reporting of AST data and rollout of external quality control assessment are urgently needed to facilitate evidence-based policy and practice.
PROSPERO CRD42018029432.
Unregulated antimicrobial use is common in both hospital and community settings of low- and middle-income countries (LMICs). However, discrete data regarding the use/misuse of antimicrobials at ...pharmacies in LMICs are limited. This study was conducted to understand knowledge, attitude, and practice of pharmacy employees on antimicrobial dispensing in Nepal.
We conducted a cross-sectional survey using a structured questionnaire on 801 pharmacy employees working in community and hospital pharmacies located in Lalitpur metropolitan city (LMC) of Kathmandu, Nepal between April 2017 and March 2019.
A majority (92%) of respondents agreed that demand for non-prescription antimicrobials was common. Asking for prescription before dispensing was ranked as the first preference by majority (69%) of participants. Suspected respiratory tract infection was the most common reason demanding for non-prescription antimicrobials with the highest mean rank of 1.5. Azithromycin was the most commonly prescribed and sold antimicrobial, as reported by 46% and 48% of participants respectively. A majority (87%) of respondents agreed on antimicrobial resistance (AMR) to be a global public health threat; and misuse/overuse of antimicrobials was perceived as the most common cause of AMR with a mean rank of 1.93.
Our study revealed that unfounded dispensing and use of antimicrobials is prevalent among pharmacies in Kathmandu, Nepal. This over reliance on antimicrobials, notably azithromycin, may escalate burden of AMR. We identified several drivers of inappropriate antimicrobial dispensing practice in pharmacies, which will aid public health authorities in addressing these issues. Further studies considering role of other stakeholders, such as doctors, veterinarians, general public, and policy makers are required to obtain a more holistic perspectives on practices of antimicrobial use so to curb the extant AMR crisis.
Southeast Asia, a vibrant region that has recently undergone unprecedented economic development, is regarded as a global hotspot for the emergence and spread of antimicrobial resistance (AMR). ...Understanding AMR in Southeast Asia is crucial for assessing how to control AMR on an international scale. Here we (i) describe the current AMR situation in Southeast Asia, (ii) explore the mechanisms that make Southeast Asia a focal region for the emergence of AMR, and (iii) propose ways in which Southeast Asia could contribute to a global solution.
The case of Mary Mallon, an asymptomatic carrier who infected 51 people while working as a cook and laundress in New York in 1906-15, showed that Salmonella enterica serovar Typhi (S Typhi) is able ...to lurk in the gallbladder without overt clinical signs and spread enteric fever through person-to-person transmission.
Adaptive evolution in humans has rarely been characterized for its whole set of components, i.e. selective pressure, adaptive phenotype, beneficial alleles and realized fitness differential. We ...combined approaches for detecting polygenic adaptations and for mapping the genetic bases of physiological and fertility phenotypes in approximately 1000 indigenous ethnically Tibetan women from Nepal, adapted to high altitude. The results of genome-wide association analyses and tests for polygenic adaptations showed evidence of positive selection for alleles associated with more pregnancies and live births and evidence of negative selection for those associated with higher offspring mortality. Lower hemoglobin level did not show clear evidence for polygenic adaptation, despite its strong association with an EPAS1 haplotype carrying selective sweep signals.
The interplay between bacterial antimicrobial susceptibility, phylogenetics and patient outcome is poorly understood. During a typhoid clinical treatment trial in Nepal, we observed several treatment ...failures and isolated highly fluoroquinolone-resistant Salmonella Typhi (S. Typhi). Seventy-eight S. Typhi isolates were genome sequenced and clinical observations, treatment failures and fever clearance times (FCTs) were stratified by lineage. Most fluoroquinolone-resistant S. Typhi belonged to a specific H58 subclade. Treatment failure with S. Typhi-H58 was significantly less frequent with ceftriaxone (3/31; 9.7%) than gatifloxacin (15/34; 44.1%)(Hazard Ratio 0.19, p=0.002). Further, for gatifloxacin-treated patients, those infected with fluoroquinolone-resistant organisms had significantly higher median FCTs (8.2 days) than those infected with susceptible (2.96) or intermediately resistant organisms (4.01)(pS. Typhi clade internationally, but there are no data regarding disease outcome with this organism. We report an emergent new subclade of S. Typhi-H58 that is associated with fluoroquinolone treatment failure.
Antimicrobial resistance (AMR) is a pressing global health concern driven by inappropriate antibiotic use, which is in turn influenced by various social, systemic, and individual factors. This study, ...nested within FIND's AMR Diagnostic Use Accelerator clinical trial in Nepal, aimed to (i) explore the perspectives of patients, caregivers, and healthcare workers (HCWs) on antibiotic prescription adherence and (ii) assess the impact of a training and communication (T&C) intervention on adherence to antibiotic prescriptions.
Using qualitative, semi-structured interviews, pre-intervention and Day 7 follow-up components, and the Behaviour Change Wheel process, we investigated the facilitators of and barriers to the use and misuse of antibiotic prescriptions.
Results of the study revealed that adherence to antibiotic prescriptions is influenced by a complex interplay of factors, including knowledge and understanding, forgetfulness, effective communication, expectations, beliefs and habits, attitudes and behaviours, convenience of purchasing, trust in medical effectiveness, and issues of child preferences. The T&C package was also shown to play a role in addressing specific barriers to treatment adherence.
Overall, the results of this study provide a nuanced understanding of the challenges associated with antibiotic use and suggest that tailored interventions, informed by behaviour frameworks, can enhance prescription adherence, may be applicable in diverse settings and can contribute to the global effort to mitigate the rising threat of AMR.
Salmonella Paratyphi A, one of the major etiologic agents of enteric fever, has increased in prevalence in recent decades in certain endemic regions in comparison to S. Typhi, the most prevalent ...cause of enteric fever. Despite this increase, data on the prevalence and molecular epidemiology of S. Paratyphi A remain generally scarce. Here, we analysed the whole genome sequences of 216 S. Paratyphi A isolates originating from Kathmandu, Nepal between 2005 and 2014, of which 200 were from patients with acute enteric fever and 16 from the gallbladder of people with suspected chronic carriage. By exploiting the recently developed genotyping framework for S. Paratyphi A (Paratype), we identified several genotypes circulating in Kathmandu. Notably, we observed an unusual clonal expansion of genotype 2.4.3 over a four-year period that spread geographically and systematically replaced other genotypes. This rapid genotype replacement is hypothesised to have been driven by both reduced susceptibility to fluoroquinolones and genetic changes to virulence factors, such as functional and structural genes encoding the type 3 secretion systems. Finally, we show that person-to-person is likely the most common mode of transmission and chronic carriers seem to play a limited role in maintaining disease circulation.
Tuberculosis (TB) remains the most common cause of infectious disease deaths worldwide. What is perhaps less appreciated is that the caseload of tuberculosis patients in South Asia is ...staggering.South Asia has almost 40% of the global TB burden with 4,028,165 cases in 2015. This region also has a disproportionate share of TB deaths (681,975 deaths, 38% of the global burden). Worldwide just 12.5% of TB cases are in HIV positive individuals, but much research and investment has focused on HIV-associated TB. Only 3.5% of patients with tuberculosis in South Asia have HIV co-infection. Not surprisingly with such a huge burden of disease, this region has an estimated 184,336 multi drug resistant (MDR) cases among notified TB cases which accounts for a third of global MDR burden. Crucially, at least 70% of the estimated MDR cases remain untreated in this region and MDR treatment success ranged from only 46% for India to 88% for Sri Lanka in the 2012 cohort that received treatment. This region represents many of the drivers of the modern TB epidemic: rapid urbanization and high density populations with dramatically rising incidence of diabetes, a burgeoning and largely unregulated private sector with escalating drug resistance and high air pollution both outdoor and household.
From bacterial biochemistry to policy implementation, we suggest ways in which South Asia can seize the opportunity lead global TB elimination by demonstrating feasibility in some of the world's most densely populated cities and remotest reaches of the Himalayas. Clearly political will is essential, but we cannot defeat TB without understanding how to eliminate it in South Asia.
Despite recent advances in typhoid fever control, asymptomatic carriage of Salmonella Typhi in the gallbladder remains poorly understood. Aiming to understand if S. Typhi becomes genetically adapted ...for long-term colonisation in the gallbladder, we performed whole genome sequencing on a collection of S. Typhi isolated from the gallbladders of typhoid carriers. These sequences were compared to contemporaneously sampled sequences from organisms isolated from the blood of acute patients within the same population. We found that S. Typhi carriage was not restricted to any particular genotype or conformation of antimicrobial resistance genes, but was largely reflective of S. Typhi circulating in the general population. However, gallbladder isolates showed a higher genetic variability than acute isolates, with median pairwise SNP distances of 21 and 13 SNPs (p = 2.8x10-9), respectively. Within gallbladder isolates of the predominant H58 genotype, variation was associated with a higher prevalence of nonsense mutations. Notably, gallbladder isolates displayed a higher frequency of non-synonymous mutations in genes encoding hypothetical proteins, membrane lipoproteins, transport/binding proteins, surface antigens, and carbohydrate degradation. Specifically, we identified several gallbladder-specific non-synonymous mutations involved in LPS synthesis and modification, with some isolates lacking the Vi capsular polysaccharide vaccine target due to the 134Kb deletion of SPI-7. S. Typhi is under strong selective pressure in the human gallbladder, which may be reflected phylogenetically by long terminal branches that may distinguish organisms from chronic and acute infections. Our work shows that selective pressures asserted by the hostile environment of the human gallbladder generate new antigenic variants and raises questions regarding the role of carriage in the epidemiology of typhoid fever.
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