ISOLATION AND IDENTIFICATION OF KLEBSIELLA ON SEA FOOD (catfish, prawns, Titus fish, shrimps, periwinkles)
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). It is a well-known hospital-acquired pathogen and associated with increased patient morbidity and mortality (Brisse et al., 2009; Cabral et al., 2012). In addition to the clinical environment, K. pneumoniae is frequently found in foods including raw vegetables, powdered infant formula, meat, fish, and street foods, and has been considered as an important food-borne pathogen (Haryani et al., 2007; Sun et al., 2010; Puspanadan et al., 2012; Overdevest et al., 2014; Kim et al., 2015; Davis and Price, 2016). In powdered infant formula, K. pneumoniae is included in the hazard identification category “B” according to the FAO and WHO guidelines on microorganisms (FAO-WHO, 2004). In recent years, an increasing number of food-borne outbreaks caused by K. pneumoniae have been reported in different countries (Calbo et al., 2011; Tambekar et al., 2011; Zhou et al., 2011; Bi and Xu, 2013; Yu and Zhou, 2013).
K. pneumoniae can express a variety of virulence factors including capsules, endotoxins, siderophores, iron-scavenging systems, and adhesins, which have been shown to play important roles in its pathogenesis. Capsule is an important virulence factor, which is involved in at least two pathogenic mechanisms: (1) protection of the bacteria from phagocytosis, and (2) direct inhibition of the host immune response (Kang et al., 2015). Some capsular (K) types, particularly K1, K2, K54, K57, K20, and K5, are often associated with community-acquired invasive pyogenic liver abscess syndrome, septicemia, and pneumonia (Fang et al., 2007; Siri et al., 2011; He, 2012). K1, K2, K20, K54, and K57 are highly virulent in experimental infections in mice and are often associated with severe infections in humans and animals (Turton et al., 2008; Yu et al., 2008; Cheng et al., 2015; Wei et al., 2016). K2 and K5 are frequent causes of metritis in mares and are associated with community-acquired pneumonia (Brisse et al., 2009). K3 is generally associated with rhinoscleroma (He, 2012). Capsule typing is currently the most widely used technique for typing K. pneumoniae isolates and exhibits good reproducibility in differentiating clinical isolates (Siu et al., 2011). 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 also 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.
The emergence of antimicrobial resistance in Klebsiella spp. isolates is of great concern worldwide in human medicine (Hu et al., 2013). Multidrug-resistant K. pneumoniae strains have been isolated from different samples (Nawaz et al., 2012; Falomir et al., 2013; Guo et al., 2016; Yaici et al., 2017). Dietary intake is one of the primary routes for the introduction of antibotic-resistant bacteria and their genes into the human digestive tract. Consumption of specific food categories might influence gut antibiotic resistance gene diversity (Milanović et al., 2017). Moreover, such bacteria may transfer antibiotic resistance determinants to other pathogenic bacteria (Machado et al., 2008). Therefore, surveillance and monitoring of drug-resistant bacteria in foods is important for implementing targeted control strategies and selecting effective drugs for treatment.
Molecular typing is a useful tool for determining the genetic relationships of food-borne bacteria and identifying probable sources of infections. This is particularly important in endemic and epidemic nosocomial outbreaks of K. pneumoniae infections to improve the management of such outbreaks. A variety of methods have been used for K. pneumoniae typing, including pulsed-field gel electrophoresis (PFGE), enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR), randomly amplified polymorphic DNA (RAPD), and (GTG)5 oligonucleotide PCR (Haryani et al., 2007; Ryberg et al., 2011; Barus et al., 2013; Sachse et al., 2014). The ERIC, RAPD, and (GTG)5-PCR assays are relatively simple and cost-effective methods that have been successfully used for genotyping K. pneumoniae isolates from various sources (Ryberg et al., 2011; Barus et al., 2013).
In recent years, the number of food-borne illness outbreaks caused by K. pneumoniae has increased. However, until now, limited information has been available on the characteristics of K. pneumoniae isolated from foods. The purpose of the present study was to determine the biotypes, serotypes, virulence genes, and antimicrobial resistance patterns of food isolates and to further analyse their genetic diversity using ERIC-PCR and (GTG)5-PCR molecular typing.
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