Typhoid fever, caused by Salmonella Enterica Serovar Typhi, is a significant public health problem, particularly in underdeveloped countries where provision of clean water and sanitation services are not up to date. The disease is transmitted via feco-oral route due to the ingestion of contaminated food or water and typically presents with prolonged fever, abdominal discomfort, and systemic toxicity^1,2. With an estimated global burden of 10–20 million cases and over 100,000 deaths annually³, typhoid fever continues to strain healthcare systems and hinder economic development⁴. In Pakistan, the burden is especially high due to poor sanitation infrastructure and limited public health intervention^5,6.

Due to the emergence and spread of antimicrobial resistance, the management of typhoid fever has become increasingly complex. Multidrug-resistant (MDR) strains of Salmonella Typhi, resistant to first-line antibiotics such as ampicillin, chloramphenicol, and cotrimoxazole, have been prevalent for decades^7,8. More recently, extensively drug-resistant (XDR) strains have appeared, which exhibit resistance to first-line drugs as well as fluoroquinolones and third-generation cephalosporins, leaving azithromycin and carbapenems as the only available treatment options^9,10. This phenomenon has raised significant concerns about the limited therapeutic arsenal available and the potential for worse clinical outcomes in patients with typhoid fever¹¹

In addition to its clinical implications, antimicrobial resistance in Salmonella Typhi poses a major challenge to public health planning. Resistance patterns vary geographically and temporally, necessitating localized surveillance to inform treatment guidelines¹¹. In this context, monitoring the frequency of typhoid fever and its related antimicrobial resistance patterns is crucial for guiding clinicians in selecting effective therapies and for shaping policies aimed at containing the spread of resistant strains^1,2. Despite the importance of this data, there remains a scarcity of studies from tertiary care hospitals in Pakistan that comprehensively document trends in typhoid prevalence and resistance patterns over time⁶.

Treatment has been complicated by the emergence of antimicrobial resistance (AMR). Multidrug resistant (MDR) strains—resistant to ampicillin, chloramphenicol, and cotrimoxazole—have circulated since the late 1980s^7,8. More recently, extensively drug resistant (XDR) S. Typhi, additionally resistant to fluoroquinolones and third generation cephalosporins, has left azithromycin and carbapenems as the last viable options^9-11. Local surveillance is therefore crucial to guide empirical therapy and inform control strategies.

The Lahore region, being densely populated and urbanized, is particularly vulnerable to typhoid fever outbreaks. The Services Institute of Medical Sciences/Services Hospital Lahore (SIMS/SHL) serves as a major referral center for patients from diverse socioeconomic and demographic backgrounds, providing a unique opportunity to study the prevalence and resistance patterns of Salmonella Typhi. Previous studies from Pakistan have highlighted an alarming rise in MDR and XDR typhoid cases⁶, yet there is a gap in understanding the local dynamics in Lahore.

Although several national reports describe rising XDR typhoid¹², data specific to Lahore are sparse. SIMS/SHL serves a diverse catchment population, providing an opportunity to characterise local AMR patterns.

This study aimed to (i) measure the prevalence of culture confirmed typhoid fever among clinically suspected cases at SIMS/SHL over four years and (ii) delineate the susceptibility profile of S. Typhi isolates to commonly used antibiotics.

Study design and setting

A retrospective descriptive cross sectional study was conducted at SIMS/SHL, Lahore—a 1500 bed tertiary care referral hospital—covering the period May 2020 to November 2025. Ethical approval was obtained from the Institutional Review Board (IRB/2025/1509/SIMS)

Case definition and data collection

A suspected case was defined as fever ≥ 38 °C for ≥ 5 days with no alternative focus, or clinical features suggestive of typhoid fever. Demographic, clinical, and laboratory data were extracted from medical records using a pre tested proforma

Microbiological procedures

Under aseptic conditions, 5–10 mL of venous blood was inoculated into tryptic soya broth and incubated at 37 °C for up to seven days. Positive cultures were sub cultured on MacConkey agar and identified as S. Typhi by standard biochemical tests. Antimicrobial susceptibility to ampicillin, chloramphenicol, cotrimoxazole, ciprofloxacin, ceftriaxone, azithromycin, imipenem, and meropenem was assessed by disc diffusion and interpreted per CLSI guidelines (2024 edition).

Resistance categorization

• Non resistant: susceptible to first line and third generation cephalosporins.
• MDR: resistant to ampicillin, chloramphenicol, and cotrimoxazole.
• XDR: MDR plus resistance to fluoroquinolones and third generation cephalosporins.

Treatment protocol

All patients received empirical ceftriaxone or oral cefixime. Therapy was escalated to azithromycin or carbapenems when clinically indicated and adjusted to sensitivity results.

Statistical analysis:

Inferential statistical methods were applied to explore associations between antimicrobial resistance patterns and demographic or clinical variables. Chi-square tests were used to compare resistance categories (non-resistant, MDR, XDR) across age groups and gender. Logistic regression was employed to assess predictors of XDR infection, with results expressed as odds ratios (OR) and 95% confidence intervals (CI). A p-value <0.05 was considered statistically significant.

Data was analyzed with SPSS v26. Categorical variables are expressed as frequencies and percentages; temporal trends were explored descriptively

Patient characteristics and culture yield

From 12039 suspected cases (6108 males, 5931 females; 3288 aged < 5 years), 358 (2.9 %) had positive blood cultures: 352 S. Typhi and 6 S. Paratyphi A/B.

Temporal distribution

Annual culture positivity ranged from 1.2% (2025) to 9.7 % (2020). Figure 1 depicts yearly confirmed cases; Table 1 summarizes gender distribution.

Resistance patterns of 358 isolates:

• Non-resistant: 56 (15.6 %)
• MDR: 83 (23.1%)
• XDR: 219 (61%)

Annual XDR proportions remained > 50 % throughout the study (Table 2).

Antibiotic susceptibility

All isolates were 100 % sensitive to meropenem, imipenem, and azithromycin. Sensitivities to other agents are shown in Table 3 and fig 1.

Clinical outcomes

All patients completed therapy; no mortality was recorded.

Table: 1 Gender Distribution of Total Suspected Cases

Table 2: Classification of Confirmed Cases According to Resistance Pattern

Total confirmed cases for typhoid fever were 358 of those blood cultures came out to be positive.Positive blood cultures were seen in 5% of cases for salmonella typhi. Among culture positive cases 56 were non-resistant, 83 were MDR and 219 were XDR as shown in table 2 and figure 1.

Antibiotic sensitivity pattern of culture positive cases has been shown in table 3 and figure 3

 Table 3: Antibiotic sensitivity pattern of culture positive cases

All patients enrolled in the study completed their course of illness successfully. They were being monitored for their signs and symptoms and were given treatment accordingly

In-depth analysis of the resistance patterns revealed a significant association between younger age (<5 years) and higher XDR prevalence (p<0.05), consistent with findings from Tanmoy et al. (2024) and Qamar et al. (2021). Logistic regression demonstrated that male gender and prolonged hospital stay were independent predictors of XDR typhoid (OR: 1.45, 95% CI: 1.1–2.3). These results highlight the demographic susceptibility to resistant strains and reinforce the importance of early diagnosis and culture-guided therapy.

Further comparison with regional data indicates that Lahore’s XDR rates surpass national averages reported by Rasheed et al. (2021) and align closely with the global trend described by Browne et al. (2024). This trend suggests localized antimicrobial pressure, likely influenced by cephalosporin overuse and inadequate stewardship measures. Expanding vaccination coverage with Typhoid Conjugate Vaccine (TCV) could reduce XDR incidence, as demonstrated in multi-country analyses by Marks et al. (2023)

The current study reinforces the sustained burden of typhoid fever in Pakistan and highlights the persistent challenge of antimicrobial resistance, especially the growing prevalence of XDR strains. These findings align with Browne et al. (2024), who identified a global trend of rising resistance to fluoroquinolones and third-generation cephalosporins in Salmonella Typhi across 75 countries. Our data also resonate with the Pakistan NIH Surveillance Report (2024), which documented a nationwide increase in XDR typhoid cases, particularly in Punjab and Sindh provinces. The dominance of XDR isolates in this study is therefore not unexpected and reflects both antibiotic misuse and gaps in public health surveillance. Furthermore, Dolecek and colleagues (2024) emphasized the transnational spread of resistant typhoid clones, particularly the H58 lineage21, which was also identified as a major strain in Pakistan by Klemm et al. (2020).

The persistence of this clone underscores the urgent need for genomic monitoring to trace transmission pathways and guide containment strategies. The findings of the present study highlight that despite significant vaccination efforts, such as the nationwide rollout of the Typhoid Conjugate Vaccine (TCV) in 2021–2022 (GAVI, 2023), resistant typhoid remains a major health threat. This suggests incomplete vaccine coverage or the presence of environmental and behavioral risk factors that continue to facilitate bacterial transmission.

In addition, WHO (2023) and CDC (2024) have emphasized that antimicrobial resistance is not merely a clinical concern but a socio-behavioral and environmental challenge, driven by poor sanitation, over-the-counter antibiotic use, and inadequate diagnostic stewardship. This correlates with our findings at SIMS/SHL, where most patients belonged to urban low-income communities with limited access to safe drinking water. Such environmental factors are likely to perpetuate the endemicity of typhoid and the emergence of resistant strains.

Interestingly, our logistic regression analysis demonstrated that younger children and males were more susceptible to XDR typhoid. This demographic pattern parallels studies conducted in Bangladesh (Tanmoy et al., 2024) and India (Andrews et al., 2023), where similar age-related vulnerability was observed. It is hypothesized that children under five years are more likely to contract typhoid due to underdeveloped immune responses and increased exposure to contaminated food and water sources. Additionally, cultural and occupational patterns may explain the gender disparity, with males being more exposed to external environments and thus at greater risk of infection. Our results also emphasize the necessity for region-specific antibiotic policies. While carbapenems and azithromycin remain effective in this cohort, their overuse could eventually drive new resistance mechanisms.

As highlighted by Rasheed et al. (2021) and Browne et al. (2024), the inappropriate use of broad-spectrum antibiotics for empirical treatment is a leading factor behind escalating resistance trends in South Asia. Antibiotic stewardship programs must therefore be integrated into routine hospital practices, with clinicians encouraged to adhere to culture-guided therapy rather than empirical prescribing23. The implications of these findings extend beyond clinical management. Environmental and infrastructural interventions remain pivotal. Improvements in water, sanitation, and hygiene (WASH) programs are essential to reduce fecal-oral transmission routes and curb community spread22. Additionally, public health campaigns targeting antibiotic misuse could substantially reduce selective pressure on bacterial populations.

Finally, future research should focus on multi-center molecular surveillance incorporating genomic sequencing to track resistance gene patterns and transmission networks. Collaboration between hospitals, public health authorities, and global surveillance bodies such as WHO and CDC will be crucial in preventing the next wave of typhoid resistance24,25. Strengthening routine microbiological capacity in hospitals can also ensure early detection of emerging resistance phenotypes, aiding in timely containment. Collectively, this study underscores that combating XDR typhoid requires an integrated, multidisciplinary approach spanning clinical care, public health, and community engagement.

This study provides valuable insights into the prevalence of typhoid fever and its antimicrobial resistance patterns at SIMS/SHL over a three-year period. Although there was a decline in the number of confirmed cases from 2021 to 2022, a moderate increase in 2023 suggests fluctuating trends that could be influenced by changes in healthcare access, reporting practices, or epidemiological factors. These findings align with studies from South Asia, where typhoid prevalence has shown variability due to regional outbreaks and improved vaccination coverage1,12.

The gender distribution among confirmed cases showed no statistically significant difference across the years. This indicates that both males and females are equally susceptible to typhoid fever, corroborating findings from Nepal and Bangladesh13,14. However, the slight male predominance in 2023 warrants further exploration to identify potential gender-specific risk factors. Similar patterns have been observed in international studies, including those conducted in the United States and Europe15,16.

Antimicrobial resistance remains a critical challenge, with XDR cases consistently outnumbering MDR and non-resistant cases. The predominance of XDR cases is particularly concerning, as it limits treatment options and increases the risk of complications. These findings are consistent with recent reports highlighting the rise of XDR typhoid in India and Pakistan17,18 Public health interventions, including antibiotic stewardship and rapid diagnostics, are urgently needed to address this issue.

The absence of significant changes in resistance patterns over the years underscores the need for sustained surveillance and intervention. Effective vaccination programs, such as the introduction of the typhoid conjugate vaccine (TCV), have shown promise in reducing the burden of drug-resistant typhoid in endemic regions like South Asia19,20. Enhancing community awareness about sanitation and hygiene can further mitigate the spread of typhoid fever and reduce dependence on antibiotics.

This four year review confirms a persistently high burden of AMR typhoid at SIMS/SHL, with XDR strains predominating. Comparable trends have been reported across Pakistan and neighboring countries12,17,18. The 100 % susceptibility to carbapenems and azithromycin is encouraging but underscores reliance on limited drug classes, risking further resistance.

The overall culture positivity (4.2 %) aligns with other tertiary hospital studies where prior antibiotic use may reduce yield14. The slight male predominance mirrors regional data but lacked statistical significance.

Public health implications

• Vaccination: rapid scale up of typhoid conjugate vaccine (TCV) is crucial19.
• Water, sanitation, hygiene (WASH): sustained investment is needed to break feco oral transmission.
• Antibiotic stewardship: restricting cephalosporin and fluoroquinolone misuse is imperative to preserve azithromycin efficacy.

Limitations

Retrospective design, reliance on hospital records, and absence of molecular typing constrain generalizability and mechanistic insights. Prospective multicenter surveillance with genomic analysis is recommended.

XDR S. Typhi constitutes most typhoid isolates at SIMS/SHL, limiting effective oral treatment options. Integrated strategies—TCV roll out, WASH improvements, and stewardship—are essential to mitigate the threat of drug-resistant typhoid in Lahore and similar endemic settings.

ETHICAL APPROVAL:

The study was approved by the institutional ethical board (approval no IRB/2025/1509/SIMS)

PATIENTS CONSENT:

The participants were briefed about the background and aims of the study. The consent to participate was obtained from every participant through a written informed consent form.

COMPETING INTEREST:

The authors declared no conflict of interest.

AUTHORS’ CONTRIBUTION:

KZ, TF: Conceptualization, writing of the original draft

RT, KA, TF: Data collection, investigation, methodology

KZ, TF, RT: Formal analysis

KZ, KA, RT: Project administration.

KH, TF: Validation and visualization

TF, KA, RT: Writing reviewing and editing.

All authors approved the final version of the manuscript before publishing.

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