State of the globe: Diagnostic tests to detect Helicobacter pylori tonsillitis

Infection with Helicobacter pylori is a worldwide public health problem which chronically affects the gastric system. Asymptomatic infection with this bacterial organism has been widely reported; however, its association with gastritis, peptic ulcers, and gastric cancer[1] has been frequently recorded in the literature. The presence of H. pylori in the upper aerodigestive tracts and locations including oral cavity[2] and saliva,[3,4] tonsils, and adenoid glands,[5,6] nose and sinuses mucus,[7–10] and even in middle ear[11] has been documented.

Some researchers believe that the tonsil and the adenoid tissue may constitute a reservoir of the H. pylori colonization and consecutive oropharyngeal and gastric infections and clinical outcomes;[12–15] whereas, others reported controversial findings.[16–18] To resolve this debate, also to determine the significance of H. pylori tonsillitis, diagnosis of the infection in these tissues should be improved. This editorial writing is to summarize the state of the globe in diagnostic tests applied for the detection of H. pylori tonsillitis.

A variety of laboratory methods, mostly rapid urease test (RUT), conventional PCR and real-time PCR, have been used for the detection of H. pylori in the clinical samples of suspected patients.

The RUT is easy to use and has been broadly used as one of the most conventional methods for the diagnosis of H. pylori infections in clinical samples. However, the specificity of RUT was found insufficient when used in the detection of throat and tonsil specimens.[19,20] Urease production by other bacterial species colonized in tonsil, throat, and mouth is documented; this can interfere with the RUT, leading to low specificity for the detection of H. pylori.[21] Yilmaz et al. used the CLO-test on the adenotonsillectomy specimens obtained from 50 children; they found no infection in the specimens, though the H. pylori Ag was detected in the stools of 50% of the children.[16]

In another study, Eyigor and colleagues examined 47 patients with chronic tonsillitis and adenoid hypertrophy for the detection of H. pylori using RUT and found only 5.5% positivity.[20] Due to the lack of gold standard, it is difficult to discuss about the accurate validity of this test in this study. Less accuracy of RUT compared to PCR in detection of H. pylori in adenotonsillectomy specimens was observed in a study sample of 20 children with the specificity of only 56%;[15] in this study, samples with consistent H. pylori positive with both RUT and PCR were considered as a “gold standard”. There is not yet a single method capable of serving as a “gold standard” for detection of the infection in upper digestive tract samples, but a combination of two or three methods can confirm actual positive samples to establish a gold standard for the methodology surveys.

Immunoflourescence, immunoelectron microscopy, and application of cytotoxin-associated antigen A are also of important and useful methods for investigation of H. pylori in the clinical materials. These have been used by Kusano et al. in a survey of 55 tonsillectomy specimens from recurrent pharyngotonsillitis or immunoglobulin A (IgA) nephropathy and detected the organism in 78.2% of the samples.[14] They found a significant association between tonsillar and gastric H. pylori infections, also concluded that tonsillar H. pylori may be one of the antigens causative of IgA nephropathy. In an earlier study on palatine tonsil of pharyngotonsillitis and IgA nephropathy patients, using immuno-tissue based techniques and in situ hybridization, Kusano et al. found similar results.[22] Light microscopy seems to be an inaccurate technique for H. pylori diagnosis. Aslan and colleagues could not detect it in pronto dry test positive tonsil tissues stained with hematoxylin–eosin, Giemsa, or Warthin–Starry silver stains.[23]

Culture and isolation of the organism from clinical samples is difficult. Kusano et al. used conventional cultures for H. pylori with different circumstances,[14] but the culture failed to detect and isolate the organism in the same specimens that were positive at 78.2% by the other methods described earlier. In contrast with this study, isolation of H. pylori from culture media inoculated by tonsillar specimens was successful in a few studies.[24,25] In a recent study, Wibawa et al.[26] utilized the culture method in combination with other methods, including immunohistochemistry and modified Giemsa stained histological survey; they could isolate H. pylori and found bacterial colonization in 15.7% of tonsillar tissues of chronic tonsillitis cases.

PCR-based methods have been also considered by several workers to detect H. pylori; satisfactory specificity has been more frequently reported with these techniques in comparison with the RUT. However, insufficient specificity with the conventional PCR, targeting ureC gene, is also reported.[27] Studies on different clinical samples, including gastric juice[28] and peptic ulcer,[29] demonstrated a high sensitivity with the PCR assay. PCR was also used for H. pylori detection in adenotonsillar samples and presented good results.[13,15] However, no PCR test was found to be positive when used for investigation of 47 samples of chronic tonsillitis using glmM gene.[20,30] It should be noted that only three samples were positive with the RUT test in this study and no other confirmatory method has been used here, therefore the PCR sensitivity cannot be discussed based on these study data.

Both the real time PCR and the scorpion real time PCR have been reported to show high specificity and sensitivity for the detection of H. pylori in various clinical samples.[31] The scorpion real-time PCR has been used by a number of researchers.[12,13,21,32,33] Utilization of the conventional PCR and the scorpion real time PCR in comparison with URT showed a strong agreement between PCR-based methods in detection of the bacterium DNA in the specimens of chronic tonsillitis and found the scorpion real-time PCR as a preferred method for diagnosis of such specimens.[34]

The PCR-based methods, in particular the real-time PCR and the scorpion real-time PCR, proved to be more valid comparing to the other methods, i.e. RUT, immunohistochemistry, light microscopy, and in vitro cultures. However, the precise validity of the available diagnostic methods for the detection of tonsillitis H. pylori in the relevant clinical samples require further evaluation with characterization and usage of a gold standard.

The PCR technology provided the tools for genotype characterization of the H. pylori isolates with concern to a variety of resolutions, i.e. pathogenic relevance, common or different colonization sources, drug resistance, etc. There are many studies focused on gastric isolates using cagA and vacA genes, but this sort of studies on upper digestive tract isolates and the pertaining data are limited. A report by Cirak et al. showed 71% cagA in the H. pylori-positive adenotonsillar specimens.[12] In another genotyping, Bulut et al. found association of cagA(+) H. pylori with adenotonsillar hypertrophy.[13] In addition, Pavlik et al. found isolates from otorhinolaryngology patients having different genotypes from those of other patients.[32] Genotype characterization of H. pylori isolates from tonsil in comparison with those of peptic isolates may be of important requirements to examine possible connection between the two sources of the bacterial colonization and their contribution to the relevant diseases.

In addition to the suitability for bacterial detection, the molecular methods showed to be an appropriate alternative to the traditional phenotypic methods in distinguishing drug (clarithromycin)-resistant isolates. Elviss et al. used 3’-mismatched reverse primer PCR in comparison with real-time PCR and PCR-RFLP developed earlier.[35] The DNA-based techniques completely correlated with the traditional methods.[36] A single-step PCR process based on the scorpion primer technology was used to discriminate between resistant and/or sensitive-associated specific alleles.[36] As one of the important diagnostic dimensions, methods for identification of drug-resistant isolates of H. pylori require further development.

In overall oropharyngeal H. pylori investigations, the attempts resulted in valuable findings that provided insight into the issue; however, small size samples in some studies may interfere with the appropriate interpretation of methodological diagnostic investigations of tonsil-related H. pylori infections. It worth noting that, to date, a single method may not be exclusively relied for detection of oropharyngeal H. pylori and a combination of diagnostic methods can be recommended.