Introduction

The global spread of multidrug-resistant bacteria has increased hospital mortality and reduced effective treatment options, making antimicrobial resistance (AMR) a major public health threat. In 2019, an estimated 1.27 million deaths were directly attributable to antibiotic-resistant bacterial infections, while approximately 4.95 million deaths were associated with antimicrobial resistance overall [1]. By 2050, antimicrobial resistance has been projected to cause up to 10 million deaths annually if effective interventions are not implemented [2]. More recent modeling suggests this early projection is proving accurate rather than overstated, estimating that AMR could account for approximately 1.91 million attributable and 8.22 million associated deaths each year by 2050, with South Asia projected to bear one of the highest regional burdens [3]. As part of this region, Pakistan is likely to face a substantial AMR burden because of challenges including inappropriate antibiotic use, surveillance gaps, and inadequate antimicrobial stewardship [1,3].

The ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) are highly virulent, multidrug-resistant bacteria that pose serious health care challenges and contribute substantially to morbidity, mortality, and health care costs [4]. The group is sometimes expanded to ESKAPEE to include Escherichia coli [5]. Because of their ability to evade commonly used antibiotics, these Gram-positive and Gram-negative pathogens are leading causes of life-threatening nosocomial infections, particularly in immunocompromised and critically ill patients [6].

The ESKAPEE pathogens employ multiple mechanisms to evade antimicrobial action, including drug inactivation, target modification, reduced intracellular drug accumulation, and biofilm formation. Drug inactivation occurs through enzymes such as β-lactamases, aminoglycoside-modifying enzymes, and chloramphenicol acetyltransferases. Target modification involves alterations in structures such as penicillin-binding proteins or ribosomal sites, exemplified by PBP2a in methicillin-resistant S. aureus and D-Ala-D-Lac substitutions in vancomycin-resistant Enterococcus faecium and Enterococcus faecalis [7]. Reduced intracellular accumulation results from decreased membrane permeability due to porin loss and increased efflux activity, particularly RND-type pumps such as MexAB-OprM and AcrAB-TolC, which expel multiple antibiotic classes [7]. Biofilm formation further enhances resistance by limiting antibiotic penetration and promoting a metabolically dormant, drug-tolerant state. These mechanisms are frequently encoded on plasmids, transposons, or chromosomes, enabling horizontal gene transfer and rapid dissemination among pathogens [7].

According to Magiorakos et al. [8], bacteria are classified as multidrug-resistant (MDR), extensively drug-resistant (XDR), or pandrug-resistant (PDR). In addition, the Infectious Diseases Society of America and the Centers for Disease Control and Prevention highlight other clinically relevant resistant groups, including extended-spectrum cephalosporin-resistant (ESCR), carbapenem-resistant Enterobacteriaceae, difficult-to-treat (DTR) bacteria, carbapenem-resistant A. baumannii, and fluoroquinolone-resistant (FQR) organisms [9].

Given the substantial global burden of antimicrobial resistance, the particularly high projected burden in South Asia, where Pakistan is situated [1,3], and the prominent role of ESKAPEE pathogens in nosocomial infections, this study aims to determine the prevalence and antimicrobial resistance patterns of ESKAPEE pathogens in Pakistan, where comprehensive regional surveillance data on their distribution and resistance profiles remain limited. These findings are essential to inform infection-control strategies, antimicrobial stewardship, and clinical management in local health care settings.