Prevalence of blaTEM and mecA resistance genes, their molecular characteristics, and associated risk determinants in bacterial isolates from patients suspected of having bacteraemia at Yarmouk Teaching Hospital, Baghdad, Iraq

Abstract

Antimicrobial resistance (AMR) is a leading global health threat, responsible for 1.27 million attributable deaths in 2019, and Iraq has experienced a poorly characterised escalation in multidrug-resistant nosocomial infections. The blaTEM and mecA genes are among the most clinically significant antimicrobial resistance determinants, yet their co-prevalence and predictors in Baghdad bloodstream infection (BSI) isolates remain undocumented.To determine and compare blaTEM and mecA prevalence in bacteraemia patients versus healthy controls at Yarmouk Teaching Hospital, Baghdad; characterise antimicrobial susceptibility profiles; reconstruct phylogenetic relationships; and identify independent predictors of resistance gene carriage. This cross-sectional comparative study (March–September 2024) enrolled 50 bacteraemia patients and 20 healthy controls. Isolates were identified by Gram stain, VITEK-2, and MALDI-TOF MS; susceptibility was tested by Kirby-Bauer disc diffusion (CLSI M100-S34). blaTEM and mecA were detected by PCR, with selected amplicons Sanger-sequenced and phylogenetically analysed. Independent predictors were identified by multivariable logistic regression. Blood cultures were positive in 44/50 (88.0%) clinical and 8/20 (40.0%) control samples. S. aureus (31.8%), K. pneumoniae (25.0%), and E. coli (20.5%) predominated. blaTEM was detected in 56.8% of clinical versus 12.5% of control isolates (OR 9.21, p=0.046); mecA in 29.5% versus 25.0% (p=0.795). MRSA accounted for 71.4% of clinical S. aureus isolates. Resistance was high to ampicillin (88.6%), trimethoprim–sulfamethoxazole (61.4%), and ceftriaxone (56.8%); imipenem resistance was 15.9%. Clinical group membership (aOR 9.17), prior antibiotic use (aOR 4.52), and K. pneumoniae species (aOR 8.63) independently predicted blaTEM carriage. Sequenced isolates clustered with regional TEM-1b lineages.  This study reveals a high prevalence of blaTEM (56.8%) and MRSA (71.4%) among bacteraemia patients at a Baghdad tertiary hospital, with prior antibiotic use as the strongest modifiable predictor. These findings support urgent antibiotic stewardship, infection control, and molecular AMR surveillance in Iraqi hospitals.