Antimicrobial Sensitivity Pattern of Salmonella Typhi: Emergence of Resistant Strains

Tracking the shift in enteric fever trends and evolving antibiotic sensitivity patterns

Objective

This study aims to examine the frequency of Salmonella Paratyphi found in blood cultures and evaluate the antibiotic susceptibility pattern of Salmonella isolates to different antibiotics. Additionally, the study aims to assess the paradigm shift in the trend of enteric fever caused by Salmonella Typhi (S. Typhi) to Salmonella Paratyphi(S. Paratyphi) .

Study Design

Retrospective study.

Participant

The study enrolled patients aged 12 years and above diagnosed with enteric fever (positive blood culture) and admitted to Peelamedu Samanaidu Govindasamy Naidu (PSG) Hospital.

Interventions

The study analyzed demographic and antibiotic susceptibility profiles of Salmonella isolates collected from 106 enteric fever patients in the hospital between 2010 and 2022. The susceptibility profiles of Salmonella isolates to multiple antibiotics were assessed.

Results

There were 106 participants, and 95 (89.62%) of them had enteric fever linked to Salmonella Typhi, while only 11 (10.38%) had enteric fever linked to Salmonella Paratyphi A. From 2010 to 2022, the study discovered a general decline in the prevalence of enteric fever caused by Salmonella species. But between 2014 and 2022, the incidence of enteric fever linked to S. Typhi rapidly increased. Azithromycin (100% , n = 106) and ceftriaxone (99% , n = 105) were highly effective against the Salmonella isolates, whereas nalidixic acid was resisted by 3 isolates (4.72%, n = 3).

Conclusion

The study observed a higher incidence of Salmonella Typhi in comparison to Paratyphi A and a greater susceptibility of males to enteric fever.

Funding

None declared.

A pattern of antibiotic drug resistance of Salmonella Typhi and Salmonella Paratyphi among children with enteric fever in a tertiary care hospital in Lahore, Pakistan

AIM

To establish the pattern of antibiotic resistance and assess the frequency of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains of Salmonella Typhi and Salmonella Paratyphi among children with enteric fever.

METHODS

This cross-sectional study was carried out in the Department of Pediatrics, Sharif Medical City Hospital, Lahore, from July 2020 to January 2021. The study involved patients aged between 0 to 15 years who attended our outpatient department or were admitted to the ward with the suspicion of typhoid fever. A convenience sample of patients with blood cultures positive for S. Typhi and S. Paratyphi was enrolled.

RESULTS

Of the 105 participants, 70 (66.7%) were male. The mean age was 8.48±4.18 years, and the most affected age group was 6-10 years (n=46, 43.8%). Among the cultured organisms, 95 (90.5%) isolates were S. Typhi and 10 (9.5%) were S. Paratyphi A. Antibiotic resistance was highest against ampicillin (n=91, 86.7%), and all of the isolates were sensitive to imipenem and meropenem. Twenty-three (21.9%) cultured organisms were MDR and 54 (56.8%) were XDR.

CONCLUSION

An alarming antibiotic drug resistance pattern was observed among children with enteric fever in Lahore. The lowest resistance was noted for azithromycin, meropenem, and imipenem. Our findings warrant the immediate implementation of tailored antibiotic stewardship and infection control strategies.

Multi-Drug Resistance to Salmonella spp. When Isolated from Raw Meat Products

Salmonella spp. is the most frequent cause of foodborne diseases, and the increasing occurrence of MDR strains is an additional and increasing problem. We collected Salmonella spp. strains isolated from meat (poultry and pork) and analysed their antibiotic susceptibility profiles and the occurrence of resistance genes. To determine the susceptibility profiles and identify MDR strains, we used two MIC methods (MICRONAUT and VITEC2 Compact) and 25 antibiotics. Phenotypic tests showed that 53.84% strains were MDR. Finally, molecular analysis strains revealed the presence of blaSHV, blaPSE-1, blaTEM, but not blaCTX-M genes. Moreover, several genes were associated with resistance to aminoglycosides, cephalosporins, fluorochinolones, sulfonamides, and tetracyclines. This suggests that further research on the prevalence of antibiotic resistance genes (ARGs) in foodborne strains is needed, especially from a One Health perspective.

Emerging Trends of Multidrug-Resistant (MDR) and Extensively Drug-Resistant (XDR) Salmonella Typhi in a Tertiary Care Hospital of Lahore, Pakistan

Salmonella Typhi is a Gram-negative pathogen that causes typhoid fever in humans. The use of antibiotics to treat typhoid has considerably mitigated its fatality risk, but rising multidrug-resistant (MDR) and extensively drug-resistant (XDR) resistance in Pakistan threatens effective treatment. This study determined the prevalence of MDR and XDR S. Typhi at a local hospital in Lahore. Blood samples (n = 3000) were obtained and processed for bacterial identification. Antibiotic susceptibility test was performed using VITEK^® 2 Compound 30 System. Statistical data analysis was performed using a Mann–Whitney U and Kruskal–Wallis H test, respectively. The results revealed 600 positive cultures, of which the majority were found to be XDR S. Typhi (46.1%) and MDR S. Typhi (24.5%) strains. The disease burden of resistant Salmonella strains was greater in males (60.67%) than females (39.33%), with the most affected age group being 0–10 years old (70.4 %). In both the outpatient department (OPD) and general ward, the prevalence of XDR S. Typhi cases was found to be alarmingly high (48.24%), followed by MDR S. Typhi (25.04 %). The results of the statistical analysis demonstrated that the incidence of resistance in MDR and XDR S. Typhi strains was not affected by the age as well as the gender of patients (p > 0.05). The occurrence of resistant strains against four tested antibiotics (azithromycin, ciprofloxacin, imipenem, and meropenem) was found to be similar in different wards and among hospitalized and OPD patients (p > 0.05). Maximum resistance was observed against chloramphenicol and ampicillin in the OPD and pediatric ward. Piperacillin/Tazobactam was observed to be the most effective antibiotic, followed by co-amoxiclav (p < 0.001). This study is effective in validating the existence of MDR and XDR S. Typhi in Lahore, where stringent methods should be applied for controlling its spread.

Traditional Widal Agglutination Test Versus Rapid Immunochromatographic Test in the Diagnosis of Enteric Fever: A Prospective Study From South India

Introduction Early diagnosis and treatment are crucial to reducing the morbidity of patients with enteric fever/typhoid fever. Among the available diagnostic tests, the blood culture is considered a gold standard. However, in most of the developing and resource-limited settings, the diagnosis is made utilizing the traditional Widal test and rapid immunochromatographic test (ICT). This study was aimed to compare the diagnostic value and efficacy of ICT and traditional Widal test in the diagnosis of typhoid fever. Methods A prospective study was conducted, and 40 patients were included in the study. The Widal test and Salmonella enterica serovar Typhi IgM/IgG immunochromatographic test were performed for all the patients. The Widal is a tube agglutination test, and the rapid ICT utilizes the principle of enzyme-linked immunosorbent assay (ELISA). All the samples were also tested for the presence of antibodies (IgG and IgM) against the S. enterica serovar Typhi and the titers against 'O' and 'H' antigens of S. enterica serovar Typhi. An antibody titer of 1:80 or more against the 'O' and 'H' antigen was considered positive. Results In the ICT, 24 samples (60%) tested positive for the IgM antibodies, and only 15 samples tested positive and for IgG antibodies. In the Widal test, 27 samples (67.6%) returned positive for antibodies against the S. enterica serovar Typhi 'O' antigen. The sensitivity (90% vs 72.73%), specificity (81.25% vs 64%), and accuracy (82.12% vs 64.87%) for the Widal test were found to be more when compared to the ICT. Conclusion The results indicate that the traditional Widal agglutination test is superior to the rapid ICT in the diagnosis of enteric fever. However, both these tests cannot be considered as gold standards for the diagnosis owing to their low positive predictive values.

The molecular basis of extensively drug-resistant Salmonella Typhi isolates from pediatric septicemia patients

Sepsis is a syndromic response to infections and is becoming an emerging threat to the public health sector, particularly in developing countries. Salmonella Typhi (S. Typhi), the cause of typhoid fever, is one primary cause of pediatric sepsis in typhoid endemic areas. Extensively drug-resistant (XDR) S. Typhi is more common among pediatric patients, which is responsible for over 90% of the reported XDR typhoid cases, but the majority of antibiotic resistance studies available have been carried out using S. Typhi isolates from adult patients. Here, we characterized antibiotic-resistance profiles of XDR S. Typhi isolates from a medium size cohort of pediatric typhoid patients (n = 45, 68.89% male and 31.11% female) and determined antibiotic-resistance-related gene signatures associated with common treatment options to typhoid fever patients of 18 XDR S. Typhi representing all 45 isolates. Their ages were 1–13 years old: toddlers aging 1–2 years old (n = 9, 20%), pre-schoolers aging 3–5 years old (n = 17, 37.78%), school-age children aging 6–12 years old (n = 17, 37.78%), and adolescents aging 13–18 years old (n = 2, 4.44%). Through analyzing bla_TEM1, dhfR7, sul1, and catA1genes for multidrug-resistance, qnrS, gyrA, gyrB, parC, and parE for fluoroquinolone-resistance, bla_CTX-M-15 for XDR, and macAB and acrAB efflux pump system-associated genes, we showed the phenotype of the XDR S. Typhi isolates matches with their genotypes featured by the acquisitions of the genes bla_TEM1, dhfR7, sul1, catA1, qnrS, and bla_CTX-M-15 and a point mutation on gyrA. This study informs the molecular basis of antibiotic-resistance among recent S. Typhi isolates from pediatric septicemia patients, therefore providing insights into the development of molecular detection methods and treatment strategies for XDR S. Typhi.