**1. Introduction**

*Helicobacter pylori* infects about 50% of the world's population and is a major cause of chronic gastritis, is strongly associated with the development of gastric and duodenal ulcers and has been linked with gastric adenocarcinoma and B-cell mucosa-associated lymphoid tissue lymphoma [1, 2].

*H. pylori* Infection results in a sequence of events, ultimately resulting in the development of some gastrointestinal disorders. The sequence was first suggested by Correa et al. in 1975 and has since been supported by many other studies. Colonization of the gastric mucosa by *H. pylori* first lead to the induction of an inflammatory response, predominantly by Th1 (T helper cells type 1). The initial acute gastritis is followed by active chronic gastritis, which lasts for life if the infection is not treated. Nevertheless, *H. pylori*-positive subjects are mostly unaware of this inflammation due to the lack of clinical symptoms. The Th1 response results in epithelial cell damage rather than in the removal of *H. pylori* because *H. pylori* is not an intracellular pathogen. The ongoing presence of *H. pylori* thus causes a lifelong proinflammatory response coupled to cellular damage and initiates the histological cascade. The continuous production of reactive oxygen species that results from the ongoing inflammation can result in DNA damage, thus inducing the multiple mutations thought to be required for initiation of the cancer cascade depicted in Figure 1 (3, 4).

Among the new methods of magnifying endoscopy, a prototype of endocytoscopy developed by Olympus was used for ex vivo visualization of *Helicobacter pylori* on experimentally infected gastric biopsies. Moving bacteria were observed at 1100× magnification, giving hope for a possible direct detection during endoscopy. Kim et al. also used magnifying endoscopy on 103 patients to classify the gastric surface according to four patterns: flat, irregular, papillary or nonstructured, which were then compared to the updated Sydney System for histologic gastritis. Histologic gastritis was found in 91% of the biopsy sections with a nonflat type, and among them, 96% were confirmed to harbor *H. pylori* infection. In another study, the magnified endoscopic findings in the gastric body

Clarithromycin Resistance and *23S rRNA* Mutations in *Helicobacter pylori* 101

Specificity

culture >95% Alternative gold

RUT >90% Cost-effective and

UBT >95% Alternative gold

antigen >90% Not widely used

Typical application

Gold standard in routin hospital diagnostics

standard

rapid test

standard

yet

Mainly used for epidemiological studies

Methods Sensitivity and

Histology >95%

Serology 80-90%

with the causes of this phenomenon still being the subject of speculation [6].

many cases with greater in vitro activity than erythromycin [7].

*H. pylori* infection can be cured by antibiotics, however the ideal anti-*H. pylori* treatment has yet to be found. Many factors have been implicated in treatment failure, including ineffective penetration of antibiotics into the gastric mucosa, antibiotic inactivation by low gastric pH, lack of compliance, and emergence of acquired antibiotic resistance by *H. pylori*. Despite the success of the current anti-*Helicobacter* therapies, it is suggested that eradication rates among patients with gastritis are lower than among patients with peptic ulcer disease,

The macrolide class of antimicrobial agents is over 30 years old and is still at the forefront of antimicrobial therapy as well as drug discovery and development. Clarithromycin is a recently approved 14-membered macrolide with increased stability in acid and improved pharmacokinetics, including the appearance of a microbiologically active metabolite in humans. Clarithromycin possesses broad-spectrum antimicrobial activity, inhibiting a range of gram-positive and gram-negative organisms, some anaerobes, and atypical pathogens, in

Clarithromycin is a semi-synthetic macrolide antibiotic. Chemically, it is 6-*0*-methylerythromycin. The molecular formula is C38H69NO13, and the molecular weight is 747.96 (Figure 2). Clarithromycin is a white to off-white crystalline powder. It is soluble in acetone, slightly soluble in methanol, ethanol, and acetonitrile, and practically insoluble in

Currently, a seven-day, triple-drug regimen has been recommended as one of the first-line therapies for *H. pylori* management. This treatment includes omeprazole (a proton-pump inhibitor), clarithromycin, and amoxicillin or metronidazole [2, 8]. However, this therapy is being investigated because of increased eradication failures due to the prevalence of clarithromycin resistant *H. pylori* infections. Many studies have shown that between 0–50% of *H. pylori* isolates were clarithromycin resistant, which leads to a need for long term

Biopsy

Fecal

Table 1. Non-PCR base diagnosis of *H. pylori* infection (3)

Invasive methods

Noninvasi ve methods

**3. Macrolide resistance** 

water.

were classified into four patterns and then correlated with histology results. Type 1 pattern corresponded to normal gastric mucosa, types 2 and 3 to *H. pylori* -infected mucosa and type 4 to atrophy. The sensitivity and specificity for these endoscopic findings were 92.7% and 100% for type 1, and 100% and 92.7% for types 2 and 3 together, respectively (5).

Fig. 1. Model representing the role of *H. pylori* and other factors in gastric carcinogenesis, based on the cascade proposed by Correa et al (3, 4)

#### **2.** *H. pylori* **detection**

Various diagnostic assays for the detection of an *H. pylori* infection are available. Histological detection and culturing of the pathogen are gold standard, which require invasive gastroduodenoscopy to obtain gastric biopsy specimens. In the last decade, noninvasive approaches, such as serological detections, the [13C] and [14C]urea breath test (UBT), and detection *H. pylori* antigen or DNA in feces, helped and improved the evaluation of *H. pylori* infection status in patients. Because of low sensitivities of most serological assays for younger than 12 years of age patients, they are not suitable for pediatric. The UBT is a well-established noninvasive diagnostic assay and gives excellent performance for both adults and children, but its specificity decreases for infants and young children and need. In addition, the performance of UBT with infants and young children requires trained staff for air sampling with a face mask, and the test also requires expensive instruments, such as an isotope ratio mass spectrometer or an infrared isotope ratio spectrometer. Enzyme immunoassays (EIAs) for the identification of *H. pylori* antigens in fecal specimens circumvent these difficulties. EIAs based on monoclonal antibodies have shown consistent excellent results, with very high sensitivities and specificities for both adults and children. A major disadvantage of all the noninvasive tests described above is their inability to provide information on the susceptibility or resistance of *H. pylori* to antibiotics [2].


Table 1. Non-PCR base diagnosis of *H. pylori* infection (3)
