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.

Background: Cholera, caused by Vibrio cholerae, remains endemic in many developing countries, including Pakistan. The extensive use of antibiotics has led to the emergence of antimicrobial resistance in V. cholerae, limiting available treatment options. In this study, we performed molecular characterisation of antibiotic-resistant V. cholerae serotype Ogawa isolates from a recent cholera outbreak in Khyber Pakhtunkhwa, Pakistan. Methodology: Suspected cholera stool samples were collected from hospitalised patients at various district hospitals of Khyber Pakhtunkhwa Province (KPK), Pakistan. The samples were transported to the Public Health Reference Microbiology Laboratory at Khyber Medical University, Peshawar. V. cholerae were identified based on colonial morphology, Gram staining, and biochemical tests using EPI 10E. For serotype identification, monovalent antisera were used. Antibiotic susceptibility testing (AST) was performed using CLSI M45 and EUCAST guidelines. DNA was extracted from pure colonies of multidrug-resistant (MDR) V. cholerae and subjected to whole-genome sequencing (WGS) for genomic characterisation using an Illumina MiSeq platform. Results: Of the 350 active diarrheal cases investigated, 70 were confirmed as V. cholerae. The outbreak was initially reported in Dir and was subsequently followed by a high incidence of cholera in the Peshawar district of KPK. All strains belong to the Ogawa serotype, which shows high antibiotic resistance, particularly to ampicillin (n = 62, 88.57%), Sulfamethoxazole/Trimethoprim (n = 60, 85.71%), Erythromycin (n = 59, 84.29%), and Tetracycline (n = 53, 75.71%). The lowest resistance was against Meropenem (n = 1, 1.4%), followed by amikacin (n = 7, 10.0%) and levofloxacin (n = 13, 18.57%). Furthermore, 34 (48.57%) of the isolates were MDR, while 13 (18.57%) were extensively drug-resistant. Six samples were selected for whole-genome sequencing. The selection of six V. cholerae samples for WGS was based on their drug resistance pattern and origin of isolation. At the genomic level, all sequenced V. cholerae strains harboured multiple antimicrobial resistance determinants. Quinolone resistance was associated with mutations and genes in gyrA, gyrB, parC, and parE; resistance to sulfamethoxazole–trimethoprim with folA, folP, and dfr; tetracycline resistance with tetA and tet35; chloramphenicol resistance with catB and S10p; and aminoglycoside resistance with hns, S12p, and gigB. In addition, β-lactam resistance was linked to the presence of efflux and β-lactamase genes, including blaSHV and mox-3. Mutations were identified in gyrA at positions S83I, S177A, and S202A, and in parC at positions S85L and I231V. Collectively, the presence of these resistance determinants likely enables V. cholerae to survive exposure to high concentrations of multiple antibiotics. Conclusions: Our V. cholerae isolates showed close genetic relatedness to previously sequenced strains from Pakistan (2010 and 2022), as well as to recently reported international strains from the USA, Australia, and China. These findings highlight both the long-term persistence of these lineages within Pakistan and their international dissemination, likely facilitated by globalisation.

Background: Klebsiella pneumoniae is a World Health Organization-listed critical priority pathogen and a major cause of healthcare-associated infections, driven by the global emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) lineages and their alarming convergence with hypervirulence. Methods: In this study, 152 clinical specimens, including urine, blood, pus, wound swabs, and respiratory samples, were collected from tertiary care hospitals in Peshawar, Pakistan. Standard microbiological and biochemical methods identified 55 K. pneumoniae isolates. Antimicrobial susceptibility testing (AST) was performed using the Kirby–Bauer disk diffusion and broth microdilution methods, with results interpreted according to Clinical and Laboratory Standards Institute (CLSI) guidelines. MDR and XDR phenotypes were defined based on European Centre for Disease Prevention and Control (ECDC) criteria. Whole-genome sequencing (WGS) was conducted on 16 phenotypically confirmed MDR/XDR isolates, followed by comprehensive bioinformatic analyses to characterize sequence types (STs), acquired antimicrobial resistance genes, resistance-associated chromosomal mutations, virulence determinants, plasmid replicons, and phylogenetic relationships. Results: Among 55 confirmed K. pneumoniae isolates, 19 (34.5%) were classified as MDR and 10 (18.2%) as XDR. WGS revealed substantial genomic heterogeneity, identifying 11 distinct STs, with ST39 being the most prevalent. Resistance to multiple antibiotic classes was mediated by the combined presence of plasmid-borne carbapenemases and extended-spectrum β-lactamases, alongside chromosomal mutations affecting outer membrane porins (OmpK35/OmpK36), fluoroquinolone targets (gyrA/parC), efflux regulation (ramR, marR), and lipid A modification pathways associated with colistin resistance (mgrB, pmrA/pmrB, arnC, crrB). IncF-family plasmids predominated and frequently co-occurred with additional resistance-associated replicons. Notably, one isolate exhibited an expanded virulence gene repertoire, including multiple siderophore systems and a complete type II secretion system, consistent with a hypervirulence-associated genomic profile. Phylogenetic analyses demonstrated close relatedness to international lineages from Asia, the Middle East, and Europe, indicating regional and transnational dissemination. Conclusions: This study highlights the complex interplay between plasmid-mediated gene acquisition and chromosomal adaptive mutations driving MDR and XDR phenotypes in K. pneumoniae circulating in Peshawar, Pakistan. The identification of hypervirulence-associated genetic features within an MDR background underscores the growing threat posed by convergent lineages and emphasizes the need for sustained WGS-based surveillance to inform infection control and antimicrobial stewardship strategies.

Background: Resistance to first-line anti-tuberculosis drugs in Mycobacterium tuberculosis represents a significant public health challenge, particularly in high-burden tuberculosis (TB) settings such as Pakistan, where multidrug-resistant (MDR) forms further complicate disease control efforts. Drug resistance is primarily associated with mutations in rpoB, inhA, katG, embA, embB, embC, and pncA. The emergence of novel, region-specific variants underscores the urgent need for integrating genomic surveillance into routine TB diagnostics and regional control programs. This study aimed to identify the spectrum of mutations contributing to first-line drug resistance in MDR-TB isolates from Khyber Pakhtunkhwa, Pakistan. Methods: Whole-genome sequencing was performed on 16 clinical isolates (12 MDR and 4 drug-susceptible) to identify resistance-associated mutations in rpoB, inhA, katG, embA, embB, embC, and pncA. Detected variants were interpreted using the World Health Organization (WHO) mutation catalogue to determine their association with drug resistance. Phylogenetic relationships were inferred using the Bacterial and Viral Bioinformatics Resource Center (BV-BRC) platform. Results: A total of 16 M. tuberculosis isolates were analyzed to evaluate resistance to first-line anti-tuberculosis drugs. In rpoB, 76 distinct variants were identified, including canonical mutations such as Ser450Leu and His445Arg, as well as a potentially novel substitution, Ser431Phe, predicted to confer high-level rifampicin resistance. The katG and inhA genes harbored 24 and 27 mutations, respectively, including well-characterized substitutions such as Ser315Thr and Ala114Glu, which are strongly associated with isoniazid resistance. Mutations in embA and embB were linked to ethambutol resistance, with several variants localized within conserved transmembrane domains critical for drug interaction. Phylogenetic analysis revealed substantial genetic diversity and evidence of local transmission among MDR-TB isolates. Conclusions: This study suggests that the genetic landscape of drug resistance in M. tuberculosis is highly dynamic in endemic regions. The findings highlight the importance of integrating region-specific mutation profiles into molecular diagnostic frameworks to enhance early detection, guide individualized therapeutic interventions, and strengthen strategies aimed at controlling the transmission of MDR-TB.

Multidrug-resistant (MDR) Klebsiella pneumoniae represents a major clinical and public health challenge worldwide, particularly in regions with limited genomic surveillance. This study investigated the clinical, phenotypic, and genomic characteristics of clinical K. pneumoniae isolates recovered from a tertiary-care hospital in Peshawar, Pakistan. A total of 2400 non-duplicate clinical specimens were processed, and antimicrobial susceptibility testing was performed according to CLSI guidelines. Whole-genome sequencing (WGS) was conducted on a purposively selected subset of 18 isolates representing diverse resistance and phenotypic profiles. Genomic analyses included multilocus sequence typing, resistome and virulome profiling, identification of resistance-associated chromosomal mutations, plasmid replicon typing, and phylogenomic comparison with publicly available international genomes. K. pneumoniae was identified in 256/2400 (10.7%) specimens, predominantly from urine samples. MDR and extensively drug-resistant (XDR) phenotypes were detected in 83.2% and 13.3% of isolates, respectively. WGS revealed substantial genomic heterogeneity, with ST147 identified as the most frequent lineage among sequenced isolates. Extended-spectrum β-lactamase genes, particularly bla_CTX-M-15, together with carbapenemase genes including bla_OXA-48-like and bla_NDM-5, were identified in multiple isolates alongside resistance-associated chromosomal alterations in gyrA, parC, ompK36, mgrB, pmrB, and ramR. Yersiniabactin-associated loci were detected in all sequenced isolates, whereas canonical hypervirulence-associated determinants (rmpA, iuc, iro) were absent. These findings highlight the complex genomic landscape of MDR K. pneumoniae in Pakistan and underscore the need for continued genomic surveillance and antimicrobial stewardship.