Helicobacter pylori is a spiral Gram-negative bacterium that is related to gastritis, gastric ulcer, and cancer. Associating Hp with breath malodor also started with an anecdotal observation. In the mid 1980s, Marshall ingested the cultivated bacteria to develop gastritis and fulfill Koch’s postulate (Marshall et al. 1985). While being infected, his colleagues noticed “putrid” odor in his breath.

Several studies were conducted in order to test the possible association between Hp infection and breath odors. Some of these studies (Gasbarrini et al. 1998; Moshkowitz et al. 2007; Schubert et al. 1992; Werdmuller et al. 2000) failed to find a link between the two. Again, these studies relied on self-reported halitosis rather than an objective means as the criterion for determining the presence of breath odors. Furthermore, few, if any, attempts were made to examine possible oral causes for the presence of malodor. Conversely, other studies (Candelli et al. 2003; Claus et al. 1996; Li et al. 2005) did show an association between Hp infection and halitosis. One of these studies (Claus et al. 1996) did rely on objective parameters (i.e., odor judge scores and GC measurements) in order to establish the presence of halitosis. Moreover, oral malodor-related parameters (PI-plaque index, GI-gingival index, PPD-periodontal pockets depth, TC-tongue coating) were also determined. Results of this study showed significantly higher mouth air malodor and H₂S levels in Hp-positive subjects, whereas no difference was seen in oral health parameters (however they did differ in age groups). Interestingly, this study links between the presence of an Hp infection and breath odors of oral origin (mouth air) rather than extra oral origin (lung air) (Table 6.2).

Another factor that may cause physicians to link Hp infection and breath odors is the clinical observation that the malodor tends to disappear following Hp eradication treatment. The first report to this effect was published in the early 1990s (Tiomny et al. 1992), showing the disappearance of breath malodor (as reported by respective family members) in four out of five patients following Hp eradication treatment (4 weeks) with metronidazole (although an earlier case report by Tydd in 1974, showed the same effect with tetracycline in pyloric stenosis patients). Several other larger studies (Ierardi et al. 1998; Katsinelos et al. 2007; Serin et al. 2003; Shashidhar et al. 2000) have also reported similar results. However, malodor production is for the most part bacterial in origin and any use of antibiotics, especially those targeted against Gram-negatives and anaerobes such as metronidazole, would be expected to affect the oral population of malodor producing bacteria and decrease or eliminate the malodor for a certain period of time.

To shed more light on this problem, one study (Ierardi et al. 1998) employed an antiseptic mouthwash containing chlorhexidine as a control showing no effect on oral volatile sulfide compounds levels in HP-positive subjects, whereas eradication therapy did reduce them. Another study (Katsinelos et al. 2007) offered long-term follow-up that showed the resolving of the malodor over a period of more than 6 months.

Nevertheless, other reports (Delanghe et al. 1996) and clinical experience show that 3–6 weeks following the end of the antibiotic course, the malodor gradually returns even though Hp is completely eradicated from the stomach (Table 6.3).