Antimicrobial Resistance in Salmonella Typhi Isolated From a Referral Hospital of Kathmandu, Nepal

Purpose:

The morbidity and mortality due to typhoid fever can be significantly reduced with the use of effective antibiotics. At present, fluoroquinolones, third generation cephalosporins, and azithromycin are widely used to treat typhoid fever. However, changing antibiotic susceptibility among Salmonella Typhi and Salmonella Paratyphi poses a particular challenge to the therapeutic management of enteric fever. The objective of this study was to assess the antibiotic susceptibility pattern of Salmonella Typhi isolates.

Patients and Methods:

A total of 706 blood specimens were collected from febrile patients attending the outpatient department of Kathmandu Model Hospital during June to September, 2018. The antibiotic susceptibility testing for 11 different antibiotics (nalidixic acid, ciprofloxacin, ofloxacin, levofloxacin, cefixime, ceftriaxone, cefotaxime, azithromycin, cotrimoxazole, chloramphenicol, and amoxicillin) was performed by disk diffusion method. Furthermore, minimum inhibitory concentration (MIC) values of ciprofloxacin, ofloxacin, and azithromycin were determined by agar dilution method. Mutation at gyrA ser83 associated with reduced susceptibility to fluoroquinolones was determined by PCR-RFLP.

Results:

Out of 706 blood samples, 6.94% (n = 49) were culture positive for Salmonella enterica (S. Typhi, n = 46). It was revealed that 97.8% S. Typhi isolates were susceptible to conventional first-line antibiotics (ampicillin, chloramphenicol, and cotrimoxazole), 97.3% to cephalosporins and 95.7% to azithromycin. S. Typhi were either resistant or intermediately susceptible to fluoroquinolones: 97.8% to ciprofloxacin, 91.3% to ofloxacin, and 89.1% to levofloxacin. The MIC of ciprofloxacin, ofloxacin, and azithromycin for S. Typhi ranged from 0.008 to 32, 0.03 to 16, and 2 to 8 μg/mL, respectively. Out of 46 S. Typhi isolates, 44 (95.65%) had gyrA ser83 mutation.

Conclusion:

Fluoroquinolones have poor activity against Salmonella Typhi. The trends of increasing azithromycin MIC value among S. Typhi might limit its use for the treatment of typhoid fever. Effectiveness of conventional first-line antibiotics in vitro suggests considering their clinical use after large-scale studies.

Antimicrobial Susceptibility Pattern of Salmonella spp. Isolated from Enteric Fever Patients in Nepal

INTRODUCTION

Enteric fever, a systemic infection caused by Salmonella enterica Typhi and S. enterica Paratyphi is one of the most common infections in developing countries such as Nepal. Aside from irrational practices of antibiotic use, mutations in chromosomal genes encoding DNA gyrase and Topoisomerase IV and by plasmid mediated quinolone resistant (PMQR) genes are suggested mechanisms for the development of resistance to nalidixic acid and reduced susceptibility to ciprofloxacin. Regardless of high endemicity of enteric fever in Nepal, there is paucity of studies on prevalence and drug-resistance of the pathogen. Therefore, this study aimed to assess the antibiotic susceptibility pattern of Salmonella isolates and determine the minimum inhibitory concentration of ciprofloxacin.

METHODS

A total of 1298 blood samples were obtained from patients with suspected enteric fever, attending Sukraraj Tropical and Infectious Disease Hospital (STIDH) during March-August, 2019. Blood samples were inoculated immediately into BACTEC culture bottles and further processed for isolation and identification of Salmonella Typhi and S. Paratyphi. Axenic cultures of the isolates were further subjected to antimicrobial susceptibility testing (AST) by using the modified Kirby-Bauer disc diffusion method based on the guidelines by CLSI. The minimum inhibitory concentration (MIC) of ciprofloxacin was determined by agar-dilution method.

RESULTS

Out of 1298 blood cultures, 40 (3.1%) were positive for Salmonella spp. among which 29 (72.5%) isolates were S. Typhi and 11 (27.5%) isolates were S. Paratyphi A. In AST, 12.5% (5/40), 15% (6/40) and 20% (8/40) of the Salmonella isolates were susceptible to nalidixic acid, ofloxacin and levofloxacin, respectively, whereas none of the isolates were susceptible to ciprofloxacin. The MIC value for ciprofloxacin ranged from 0.06-16 µg/mL in which, respectively, 5% (2/40) and 52.5% (21/40) of the isolates were susceptible and resistant to ciprofloxacin. None of the isolates showed multidrug-resistance (MDR) in this study.

CONCLUSION

This study showed high prevalence of quinolone-resistant Salmonella spp., while there was marked re-emergence of susceptibilities to traditional first option drugs. Hence, conventional first-line-drugs and third-generation cephalosporins may find potential usage as the empirical drugs for enteric fever. Although our reporting was free of MDR strains, extensive surveillance, augmentation of diagnostic facilities and treatment protocol aided by AST report are recommended for addressing the escalating drug-resistance in the country.

The challenges and successes of implementing a sustainable antimicrobial resistance surveillance programme in Nepal

Background

Antimicrobial resistance (AMR) is a major global public health concern and its surveillance is a fundamental tool for monitoring the development of AMR. In 1998, the Nepalese Ministry of Health (MOH) launched an Infectious Disease (ID) programme. The key components of the programme were to establish a surveillance programme for AMR and to develop awareness among physicians regarding AMR and rational drug usage in Nepal.

Methods

An AMR surveillance programme was established and implemented by the Nepalese MOH in partnership with the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR, B) from 1998 to 2003. From 2004 to 2012, the programme was integrated and maintained as a core activity of the National Public Health Laboratory (NPHL) and resulted in an increased number of participating laboratories and pathogens brought under surveillance. The main strategies were to build national capacity on isolation, identification and AMR testing of bacterial pathogens, establish laboratory networking and an External Quality Assessment (EQA) programme, promote standardised recording and reporting of results, and to ensure timely analysis and dissemination of data for advocacy and national policy adaptations. The programme was initiated by nine participating laboratories performing AMR surveillance on Vibrio cholerae, Shigella spp., Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria gonorrhoeae.

Results

The number of participating laboratories was ultimately increased to 13 and the number of pathogens under surveillance was increased to seven (Salmonella spp. was added to the surveillance programme in 2002 and extended spectrum β-lactamase producing Escherichia coli in 2011). From 1999 to 2012, data were available on 17,103 bacterial isolates. During the AMR programme, we observed changing trends in serovars/ species for Salmonella spp., Shigella spp. and V. cholerae and changing AMR trend for all organisms. Notably, N. gonorrhoeae isolates demonstrated increasing resistance to ciprofloxacin. Additionally, the performance of the participating laboratories improved as shown by annual EQA data evaluation.

Conclusions

This Nepalese AMR programme continues and serves as a model for sustainable surveillance of AMR monitoring in resource limited settings.

Antimicrobial resistance in Salmonella enterica serovar typhi and paratyphi in South Asia-current status, issues and prospects

The human race owes a debt of gratitude to antimicrobial agents, penicillin and its successors that have saved people from tremendous pain and suffering in the last several decades. Unfortunately, this consideration is no more true, as millions of people are prone to the challenging threat of emergence of antimicrobial resistance worldwide and the menace is more distressing in developing countries. Comparable with other bacterial species, Salmonella enterica serovar Typhi (S. typhi) and Paratyphi (S. paratyphi) have been evolving multidrug resistance (MDR) against a wide array of antibiotics, including chloramphenicol, ampicillin and co-trimoxazole, and globally affecting 21 million people with 220,000 deaths each year. S. typhi and S. paratyphi infections are also endemic in South Asia and a series of antibiotics used to treat these infections, have been losing efficacy against enteric fever. Currently, quinolones are regarded as a choice to treat MDR Salmonella in these regions. Travel-related cases of enteric fever, especially from South Asian countries are the harbinger of the magnitude of MDR Salmonella in that region. Conclusively, the MDR will continue to grow and the available antimicrobial agents would become obsolete. Therefore, a radical and aggressive approach in terms of rational use of antibiotics during treating infections is essentially needed.

Trends of etiology and drug resistance in enteric fever in the last two decades in Nepal: a systematic review and meta-analysis

Prospective time-trend analyses on shifting etiology and trends of drug resistance in enteric fever are scarce. Using published and unpublished datasets from Nepal, we performed a systematic review and meta-analysis to understand the trends in etiology and resistance to antimicrobials that have occurred since 1993. Thirty-two studies involving 21 067 Salmonella enterica serotype Typhi (ST) and S. enterica serotype Paratyphi A (SPA) isolates were included. There was an increasing trend in enteric fever caused by SPA during the last 2 decades (P < .01). We observed sharply increasing trends in resistance to nalidixic acid and ciprofloxacin for both ST and SPA. In contrast, multi-drug resistance (MDR), resistance to traditional first-line antibiotics such as chloramphenicol and co-trimoxazole have significantly decreased for both organisms. The resistance to ceftriaxone has remained low, suggesting it is likely to remain useful as a reserve antibiotic for treatment. Trends in decreasing resistance to traditional first-line antibiotics and decreasing MDR provide an opportunity to reconsider these first-line antimicrobials as therapeutic options.

Antibiotic susceptibility pattern and the indicator of decreased ciprofloxacin susceptibility of Salmonella enterica serovar Typhi isolated from Dhulikhel Hospital, Nepal

Monitoring the antibiotic susceptibility pattern of Salmonella enterica serovar Typhi (S. Typhi) is important for efficiently managing cases of typhoid fever. In this study, the antimicrobial susceptibility patterns of 114 S. Typhi isolates, which were collected from a university hospital in Nepal during July 2009-December 2010, were investigated by disc diffusion assays. All of the S. Typhi isolates were sensitive to amoxycillin-clavulanic acid. More than 95% of the isolates were sensitive to chloramphenicol, ceftazidime, ceftriaxone, and cotrimoxazole. In addition, 1.7% of the studied isolates showed multiple drug resistance patterns. Of the 40 S. Typhi isolates, 32 strains (80%) showed nalidixic acid (NA) resistance with decreased susceptibility to ciprofloxacin (CIP). Importantly, we found the simultaneous presence of NA resistance and decreased susceptibility to CIP, suggesting that the resistance to NA is a reliable indicator of decreased CIP susceptibility (sensitivity, 97.5%; specificity, 100.0%). Furthermore, the sequencing of NA-resistant S. Typhi isolates showed a predominant amino acid alteration in the quinolone resistance-determining region (QRDR) of gyrA gene at position 83 from Ser→Phe. Two isolates with resistance to both CIP and NA had a double-mutation (Ser83→Phe and Asp87→Asn) in the QRDR of the gyrA gene, of which one had an additional amino acid mutation (Ser80→Ilu) in the QRDR of the parC gene.

Serotyping, PCR, phage-typing and antibiotic sensitivity testing of Salmonella serovars isolated from urban drinking water supply systems of Nepal

AIMS

To study the occurrence and diversity of Salmonella serovars in urban water supply systems of Nepal.

METHODS AND RESULTS

Occurrence of Salmonella was detected in 42 out of 300 water samples by enrichment culture technique in selenite F broth followed by plating on Salmonella Shigella agar. A total of 54 isolates identified to genus level by standard tests were subsequently confirmed by serotyping, phage typing and PCR detection of virulence genes (inv A and spv C). The predominant serotype was Salmonella Typhimurium, followed by Salm. Typhi, Salm. Paratyphi A and Salmonella Enteritidis. Most of the Salm. Typhi isolates were E1 phage type followed by UVS4, A and UVS1. All isolates of Salm. Paratyphi A and Salm. Enteritidis were an untypable (UT) phage type. The majority of isolates were multi-drug resistant as revealed by Kirby-Bauer disc diffusion technique. Ceftriaxone resistant isolates of Salm. Enteritidis indicated the presence of one of the ESBL genes, blaSHV, whereas the genes blaTEM and blaCTX were absent.

CONCLUSIONS

The microbiological quality of the urban water supply is poor and indicates possibility of fatal outbreaks of enteric fever and related infections in Nepal.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study will be useful in water borne disease control and prevention strategy formulation in Nepal and in the global context.