**8. Conclusions**

*Helicobacter pylori* is a complex microorganism that is difficult to cultivate, and treat also presenting particular characteristics of pathogenicity and virulence markers. Much progress has been made since 1983 when it was discovered first by Warren and Marshall [1] making it one of the most studied bacteria. *Hp* is well adapted to the human host as evidenced by its chronical persistence in the gastric niche and by the finding that the bacterial surface carries structures (antigens) which are identical to those found on human cells [54].

The markers of virulence such as CagA and VacA are seen to greatly influence the outcome of *Hp* infection. The combination of different virulence genotypes is the most important factor that strongly affects the bacterial virulence making some strains more pathogenic than others.

The heteroresistance is a big problem in the evaluation and management of *Hp* resistance in the infections. In fact the heteroresistance detected in five of our patients worsens the situation being an important issue as an isolate could be mistakenly considered susceptible if a single biopsy is used for antimicrobial tests possibly leading to a resistance underestimation [31].

The emergence of PCR method provides a quick, convenient way to guide tailored therapy in clinical practice of *H. pylori* [55]. In this situation without performing the susceptibility tests which are time-consuming and expensive, the gastroenterologists could establish a suitable treatment for *Hp* infected patients who in any case underwent a gastroscopy. The use of genotypic tests directly on the clinical specimens could predict the antibiotic resistance addressing changes in previous treatments. The real-time PCR detects the resistant population at a very low concentration not detectable by phenotypic tests which primarily show susceptible bacteria. The genotypic-resistance is useful in case of absence of live bacteria, contamination or for identifying mixed infections.

The CLA-resistance levels and mainly the local susceptibility turn out to be crucial to establish a correct therapy. The quadruple therapy (BQT) with proton pump inhibitor, bismuth and a combination of two antibiotics, specifically MZ and TE then unaffected by CLA and LEV resistance, turns out to be appropriate in the *Hp* infected- patients resulting in an effective eradication rate.

The lack of data on local susceptibility patterns and on eradication success rates was identified as a knowledge gap that has a major impact on the choice of therapy and hence best management. Periodic susceptibility testing should be considered by health authorities and clinicians should be encouraged to record their successes.

All in all we can say that this microorganism since its discovery in 1983 by Marshall and Warren, has been deeply studied and considered one of the most important gastric pathogen involved in a wide range of pathologies other than the classical ones, such as cancer, atherosclerosis and endothelial dysfunction leading to vascular diseases.

### **Acknowledgements**

I wish to thank Mrs. Maria Paola Hassemer for her valuable support in finding and organizing the bibliography.

### **Conflict of interest**

The authors declare no conflict of interest.

*Virulence Markers, Genotypic versus Phenotypic Resistance and New Treatment Strategies... DOI: http://dx.doi.org/10.5772/intechopen.97026*
