Abstract
Klebsiella pneumoniae is not only a major hospital-acquired pathogen but also an important food-borne pathogen that can cause septicaemia, liver abscesses, and diarrhea in humans. The phenotypic and genotypic characteristics of K. pneumoniae in retail foods have not been thoroughly investigated in China. The objective of this study was to characterize K. pneumoniae isolates through biotyping, serotyping, determination of virulence factors, antibiotic resistance testing, enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR), and (GTG)5-PCR molecular typing. From May 2013 to April 2014, a total of 61 K. pneumoniae isolates were collected from retail foods in China. Using API 20E test strips, five different biotype profiles were identified among these isolates. The majority of isolates belonged to biochemical profile “5215773” (50 isolates, 80.6%). The capsular serotypes of the 61 K. pneumoniae isolates and one reference strain were determined by PCR. Of the seven capsular serotypes tested, four different capsular serotypes were identified. Serotypes K1, K20, K57, and K2 were detected in two, three, two, and one isolates, respectively. Serotypes K3, K5, and K54 were not detected. The presence of 11 virulence genes was assessed by PCR. The most common virulence genes were fimH (85.5%), ureA (79.0%), wabG (77.4%), uge (56.5%), and kfuBC (29.0%). ERIC-PCR and (GTG)5-PCR molecular typing indicated high genetic diversity among K. pneumoniae isolates. We identified 60 different ERIC patterns and 56 distinct (GTG)5 patterns. Genotypic results indicated that isolates carrying similar virulence factors were generally genetically related. Some isolates from the same geographic area have a closer relationship. The isolates showed high levels of resistance to ampicillin (51/62, 82.2%). Resistance to streptomycin (11/62, 17.7%) and piperacillin (10/62, 16.1%) was also common. The presence of virulent and antibiotic-resistant K. pneumoniae in foods poses a potential health hazard for consumers. Our findings highlight the importance of surveillance of K. pneumoniae in foods.
Highlights
Klebsiella pneumoniae is an important opportunistic pathogen that causes a variety of infectious diseases in humans, including septicaemia, liver abscesses, diarrhea, and pneumonia (Bi and Xu, 2013; Cao et al, 2014; Guo et al, 2017)
Capsular serotyping results of the 61 K. pneumoniae isolates and one reference strain showed that eight isolates were typeable serotypes and 53 were untypeable serotypes
A total of four different capsular serotypes were identified, with serotype K1 detected in two isolates from fish samples, K20 detected in three isolates, K57 detected in two isolates, and K2 detected in the reference strain
Summary
Klebsiella pneumoniae is an important opportunistic pathogen that causes a variety of infectious diseases in humans, including septicaemia, liver abscesses, diarrhea, and pneumonia (Bi and Xu, 2013; Cao et al, 2014; Guo et al, 2017). Several PCRs targeting the wzy genes have been developed for capsule typing of K. pneumoniae (Turton, 2010; Cheng et al, 2015) Other virulence factors such as the rmpA gene (regulator of mucoid phenotype A); allS gene (encoding the activator of the allantoin regulon, associated with allantoin metabolism); endotoxin-related genes wabG, uge, and wcaG; iron acquisition system-related genes iucB, iroNB, ybtA, and kfuBC; adhesin gene fimH (type I fimbriae); and ureA gene (α-subunit of the urease, invasin related) are believed to be involved in virulence processes (Brisse et al, 2009; Turton, 2010; El et al, 2013; Calhau et al, 2014). The detection of such virulence factors is important in understanding the pathogenic characteristics of K. pneumoniae isolates and enhancing our knowledge of the health risks posed by this pathogen
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