Determination of the prevalence of Helicobacter heilmannii-like organisms type 2 (HHLO-2) infection in humans and dogs using non-invasive genus/species-specific PCR in Korea.

Helicobacter spp. are gram-negative and spiral-shaped bacteria. Till now, almost 24 Helicobacter spp. have been reported, and most are suspected or proven gastric or hepatic pathogens [1]. Spiral organisms, such as Helicobacter spp., have been observed in domestic feline and canine gastric tissues since the last 100 years. These gastricbacteria have received special attention, and it seems that the stomachs of many types of domestic or companion animal species harbor their own Helicobacter spp. with long-term evolution. The Helicobacter spp. infection rate is 40 to 80% throughout the world in humans, and the most common Helicobacter spp. infection in humans in half of the world’s population is H. pylori [2]. Recently, H.pylori was identified in domestic cats obtained from a commercial breeder, which suggests that pets may be a potentialsource of H. pylori infection [3]. General diagnostic methods for Helicobacter infection are divided into invasive and non-invasive methods [4]. ELISA has been developed and used for making the diagnosis of Helicobacter species, and direct observation of Helicobacter spp. organisms in biopsied specimens usually requires the use of special stains, e.g. Giemsa, WSS, Genta and alcian yellow-toluidine blue stains. Typically, H.pylori is not visualized by HE however, this method is less sensitive in most Helicobacter species. In non-invasive methods, the PCR assay has a higher sensitivity and specificity than the other non-invasive methods, such as serological tests, and nested PCR analysis for Helicobacter spp. increases both the sensitivity and specificity than a single PCR analysis [6]. However, epidemiologic data of other Helicobacter spp., such as H. felis and H. bizzozeronii, are lacking to support the animal and public health implications. Helicobacter spp. have been detected continuously in humans, mainly H. pylori, and Helicobacter spp., such as H.felis and H. bizzozeronii, have been detected in pets in Korea [7]. Despite the advances in understanding the pathophysiology and virulence determinants of H. pylori infection, knowledge of H. felis or H. bizzozeronii is lacking till now [8]. Animal and public health implications of Helicobacter species have been continuously debated since their introduction to the seroepidemiologic studies of H. pylori with transmission occurring from cats to humans [9] or from sheep milk to humans [10]. Recently, circumstantial evidence has suggested that these bacteria, also referred to as “Helicobacter heilmannii-like organisms” (HHLO), may be transmitted through animals [11]. At least two genotypically different types of HHLO have been identified based on the analysis of 16S rRNA genes, and type II was found to be highly related to H. felis and H. bizzozeronii. Although HHLO-2 (HHLO type II) was found in a small percentage of 0.2 to 0.6% in humans, approximately 50% of non-pylori Helicobacter species inducing gastritis, gastric ulcer and MALT lymphoma in humans are associated with HHLO-2 [12]. The infection with HHLO-2 is common in domestic animals with or without gastric diseases, and various studies have reported the prevalence rate as 41 to 100% in dogs and 57 to 100% in cats [13, 14]. The identification of HHLO-2 in humans that have mostly been identified in pets arouses interest in the zoonotic potential of HHLO-2; however, this finding is not clear as yet. The aims of this study were to evaluate the prevalence and morphologic types of Helicobacter spp. using Helicobacter genus-specific PCR and Helicobacter species-specific PCR and to assess the relation of exposure to pets with HHLO-2 prevalence in a population-based study of pet owners in Korea.