Phenotypic and Molecular Characterization of Klebsiella pneumoniae Species Complex Isolates from Clinically Healthy Poultry, with Identification of Novel K. quasipneumoniae ST9812

This cross-sectional, culture-based study aimed to recover Klebsiella pneumoniae species complex (KpSC) isolates from fecal samples collected from clinically healthy chicken and turkey flocks in Diyarbakır, Türkiye, and to characterize the sequence-confirmed isolates. A total of 419 fecal samples from small-scale, family-operated farms were examined. Presumptive isolates were screened by MALDI-TOF MS and confirmed by 16S rRNA and rpoB gene sequencing. Antimicrobial susceptibility testing, phenotypic ESBL and carbapenemase assays, targeted PCR detection of resistance- and virulence-associated genes, multilocus sequence typing (MLST), and phylogenetic analyses were performed. Six KpSC isolates were confirmed from the 419 samples examined (6/419, 1.43%): K. pneumoniae (n = 4), K. quasipneumoniae (n = 1), and K. variicola (n = 1). All six were resistant to ampicillin, amoxicillin, and enrofloxacin; two were multidrug-resistant, and one showed an ESBL phenotype. No carbapenemase phenotype or targeted carbapenemase genes were detected. intI1 and blaSHV were each detected in four isolates, while wabG and entB were present in all isolates. MLST identified six distinct sequence types, one of which, K. quasipneumoniae ST9812, was novel and associated with the novel rpoB allele 593, while one turkey-origin K. pneumoniae isolate belonged to ST15. These findings demonstrate phenotypic and molecular diversity among poultry-origin KpSC isolates and provide a basis for broader genomic investigation of their epidemiological significance.