Typhoid fever, caused by Salmonella enterica subsp. enterica serovar Typhi (S. typhi), remains a major public health concern, particularly in low-resource settings with poor sanitation. The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains have significantly complicated treatment, especially in vulnerable pediatric populations. This study aimed to characterize the genetic profiles of drug resistance in MDR and XDR S. typhi isolates from pediatric patients. Methods: A cross-sectional study was conducted on 800 blood samples from pediatric typhoid patients. S. typhi isolates were identified using the BacT/ALERT 3D system, followed by culture on MacConkey and blood agar. Antimicrobial susceptibility was assessed using the disk diffusion method according to CLSI 2022 guidelines. Whole-genome sequencing (WGS) was performed on 29 isolates using Illumina MiSeq technology, and resistance genes and mutations were analyzed. Results: Antimicrobial susceptibility testing revealed that 68 (48.57%) of S. typhi isolates were XDR and 61 (43.57%) were MDR, exhibiting widespread resistance to ciprofloxacin, ampicillin, chloramphenicol, ceftriaxone, and co-trimoxazole. WGS identified key resistance genes across all 29 isolates, including bla_CTX-M-15, bla_TEM-1B, qnrS1, aac(6′)-Iaa, catA1, dfraA7, sul1, qacEΔ1, and the gyrA-S83F mutation. Notably, gyrA-S83F and qnrS1 were detected in all isolates and strongly correlated with ciprofloxacin resistance. Virulence genes were consistently present in all isolates, indicating a high pathogenic potential. The IncY plasmid, found in four (14%) isolates, was linked to resistance against third-generation cephalosporins, including ceftriaxone. Conclusion: This study underscores the alarming prevalence of MDR and XDR S. typhi isolates among pediatric patients, driven by resistance genes such as bla_CTX-M-15, bla_TEM-1B, and gyrA-S83F. These findings highlight the urgent need for targeted therapeutic strategies and robust surveillance systems to combat the growing threat of drug-resistant typhoid fever.

Tuberculosis (TB), caused by bacteria of the Mycobacterium tuberculosis complex (MTBC), remains a global health challenge, exacerbated by multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains. This study employs whole-genome sequencing (WGS) to characterise genetic mutations associated with pyrazinamide (PZA) and fluoroquinolone (FQ) resistance in MDR-TB isolates from KPK. MDR and pre-XDR TB samples were collected and processed at the Provincial Tuberculosis Reference Laboratory under Biosafety Level III conditions. Samples underwent microscopy, GeneXpert MTB/RIF assay, culture, and drug susceptibility testing. DNA was extracted from positive cultures and subjected to WGS. Bioinformatics tools were used to analyse sequencing data, identify resistance-associated mutations, and assess genetic diversity among isolates. Out of the 78 MTBC isolates analysed, 67 (85.9 %) were identified as MDR-TB, with 48 categorized as pre-XDR, while 11 were drug-susceptible. The isolates predominantly came from young patients (mean age: 29.5 years, SD ±12.64), with a higher proportion of female patients (61.53 %). Mutations in the pncA gene, associated with PZA resistance, were identified in 51 isolates. Resistance to fluoroquinolones was linked to mutations in the gyrA and gyrB genes in 48 isolates. WGS confirmed PZA resistance in 51 isolates, 39 (76.47 %) of which also exhibited FQ resistance. Phylogenetic analysis revealed that Lineage 3 (L3) was predominant (58.97 %), followed by L4, L2, and L1 strains. The clustering of drug-resistant strains within L3 suggests ongoing localized transmission. These findings underscore the urgent need for targeted interventions, including enhanced molecular surveillance and tailored treatment strategies, to combat MDR-TB in KPK.