Virulence Gene Analysis And Molecular Genotyping Of Klebsiella Pneumoniae In Liver Abscess

Background: The prevalence of K.pneumoniae infection in mainland China wasremaining unknown. Our aims were to perform a retrospective comparison ofbacterial liver abscess (BLA) among patients with Klebsiella pneumoniae andnon-Klebsiella pneumoniae associated abscesses, then analyse the virlence gene andmolecular genotyping of these pathogens. Methods: Between2008and2011,131confirmed cases of BLA patients, admitted to three big medical centers in Beijing,China, were enrolled. Serology of the underlying pathogen was determined fromclinical isolates obtained from the liver abscess of the enrolled patients. Basicclinical data, including patient information, underlying diseases, clinicalmanifestations, laboratory tests, and ultrasound and computer tomography imagingcharacteristics were obtained and compared from all enrolled patients. PCR andPFGE were used to analyse the virlence gene and molecular genotyping Results: Ofthe131cases,101(77.10%) were due to Klebsiella pneumoniae (KP) and30(22.90%) due to non-Klebsiella pneumoniae (non-KP). The KP cohort showedsignificantly more robust expression of the regulator of mucoid phenotype gene A(rmpA) and aerobactin gene, but not the mucoviscosity-associated gene A (magA).Whereas diabetes was significantly more associated with KP cases, prior history ofabdominal surgery or chemoradiation therapy were significantly associated withnon-KP cases. Ultrasound imaging showed significantly more abscess in the gaschamber among KP cases. Pre-contrast computerized tomographic images showedthat the non-KP group (66.67%) had a higher chance of a clear edge than the KPgroup (25.00%); P <0.001. However, the KP group showed significantly more gasin the abscess (38.75%in KP vs22.22%in non-KP; P <0.05). Of the101KP cases,K1and K2serotypes were found in43(42.57%) and37(36.63%) cases, respectively; the remaining21(20.79%) cases were due to non-K1/K2serotypes. Ahypermucoviscosity(HM) phenotype was determined in90(89.11%) cases. A highproportion of the KP-positive isolates expressed rmpA and aerobactin, but not magA.All of the101KP isolates was belong to the same cluster. Conclusions: Klebsiellapneumoniae liver abscess (KPLA) and non-Klebsiella pneumoniae liver abscess(NKPLA) have distinctive risk factors, unique ultrasonographic and computedtomography features. KPLA was suffered mostly by men, diabetes mellitus was themajor risk factor followed by hepatobilliary disease, most cases showed singleabscess located at right hepatic lobe. The mortality was lower than that from othercountries and regions.The structure feature added to HM phenotype of K.pneumoniae should be considered as to the formation of abscess. rmpA, which aidscapsule synthesis, had also been proposed as a virulence factor in addition to magAand capsular serotypes K1/K2...