Emergence of K1 ST23 and K2 ST65 hypervirulent klebsiella pneumoniae as true pathogens with specific virulence genes in cryptogenic pyogenic liver abscesses Shiraz Iran

Abstract

Hypervirulent Klebsiella pneumoniae (hvKp) pathotype is emerging worldwide in pyogenic liver abscesses (PLAs). However, the role of virulence factors in pathogenicity remains unclear. On the other hand, the epidemiology of PLAs in Iran is unknown. From July 2020 to April 2022, bacterial species were isolated and identified from the drainage samples of 54 patients with PLAs. K. pneumoniae as the most common pathogen of pyogenic liver abscesses was identified in 20 (37%) of the 54 patients. We analyzed the clinical and microbiological characteristics of K. pneumoniae-related pyogenic liver abscesses. Antibiotic susceptibility testes and string test were performed. 16S rRNA, antibiotic resistance, and virulence genes were determined by polymerase chain reaction amplification. Clonal relatedness of isolates was identified by multilocus sequence typing. Virulence levels were assessed in the Galleria mellonella larval infection model. Four hvKp isolates (K1/K2) were found to be responsible for cryptogenic PLAs, and 16 classical K. pneumoniae isolates (non-K1/K2) were associated with non-cryptogenic PLAs. Three capsular serotype K1 strains belonged to sequence type 23 (ST23) and one K2 strain to ST65. Meanwhile, the non-K1/K2 strains belonged to other STs. ST231 was the most common strain among the classical K. pneumoniae strains. Compared with the non-K1/K2 strains, capsular serotypes K1/K2 strains were less resistant to antibiotics, had positive string test results, and had more virulence genes. In Galleria mellonella, a concentration of 106 colony-forming units of the K1 hvKp strain resulted in 100% death at 24 hours, confirming the higher virulence of the hvKp strain compared with cKp. K. pneumoniae isolates represented that the acquisition of any plasmid or chromosomal virulence genes contributes to pathogenicity and high prevalence in PLAs. Meanwhile, hvKp isolates with a specific genetic background were detected in cryptogenic PLAs.

Molecular epidemiology and clinical characteristics of the type VI secretion system in Klebsiella pneumoniae causing abscesses

“…K1 and K2 were strongly associated with high virulence in the previous study, and our results also found that K1 and K2 showed lower drug resistance ( Lee et al, 2017 ; Sohrabi et al, 2022 ). In our study, T6SS-positive strains had a higher detection rate of the K1 capsular serotype than T6SS-negative strains.…”

Diversity of hypervirulent Klebsiella pneumoniae clones causing cryptogenic liver abscesses and metastatic complications in Argentina.

“…Identi cation of virulence-associated genes. Four genes for virulence including iucA, iroB, plasmid-borne rmpA and an isoform rmpA2 were identi ed by PCR with the speci c primers previously reported [25][36] [30] (Table 1). Characterization of capsular types.…”

The Antibacterial Effect of Boron Compounds and Evaluation of the Effects on Biofilm Formation in the Infection Model of Klebsiella pneumoniae on the HepG2 Cell Line

“…[4] In addition, virulence factors in Klebsiella pneumoniae, capsular serotype, mucoviscosity-associated gene A (magA), rmpA and aerobactin are important in the formation of liver abscesses. [4,5] Klebsiella pneumoniae strains expressing the capsular type K1 or K2 antigen are virulent. These serotypes have a high prevalence of resistance to phagocytosis and intracellular killing by neutrophils and bactericidal complements in a patient's serum.…”

“…Although Klebsiella pneumoniae serotypes K1 and K2 isolated from patients with liver abscesses usually show hypermucoviscosity, they are known to be an indicator of capsular polysaccharide expression, which is related to resistance to phagocytosis. [5] magA has been identified as the gene that causes Klebsiella pneumoniae liver abscess and septic metastatic complications. [6] RmpA aids in capsule synthesis in addition to magA and capsular serotype K1/ K2.…”