Treatment of Pediatric Helicobacter pylori Infection

Helicobacter pylori infection can cause gastritis, gastric or duodenal ulcers, mucosa-associated lymphoid tissue lymphoma, gastric cancer, and extra-gastrointestinal manifestations. Ideal treatment should be guided by antibiotic susceptibility testing. However, this is not feasible in many regions, so the treatment generally relies on clinical experience and regional culture sensitivity profiles. We aimed to integrate the treatment of pediatric H. pylori infection through a systematic literature review. Databases including PubMed, Cochrane Library, EMBASE, and Scholar were searched using terms containing (Helicobacter OR Helicobacter pylori OR H. pylori) AND (child OR pediatric) for all relevant manuscripts and guidelines, published from January 2011 to December 2021. The eradication rate for pediatric H. pylori infection was not satisfactory using triple therapy, sequential therapy, concomitant therapy, bismuth-based quadruple therapy, or adjuvant therapy with probiotics as the first-line therapy. Most therapies could not achieve the recommended eradication rate of >90%, which may be attributed to varying regional antibiotic resistance and possible poor children’s compliance. More studies are required to establish a best practice for pediatric H. pylori infection treatment.


Introduction
Helicobacter pylori (H. pylori) is a gram-negative bacterium, first isolated by Warren and Marshall in 1983 on the surface of the stomach [1,2]. H. pylori colonize gastric mucosa and could produce urease-dependent ammonia locally, raising the stomach pH, which promotes bacterial survival and solubilizes the mucous gel to facilitate bacterial motility [3]. H. pylori infection can cause gastritis, gastric or duodenal ulcers, mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric cancer especially adenocarcinoma [1,4]. In addition, extragastrointestinal manifestations were reported, including iron deficiency anemia [5], chronic immune thrombocytopenic purpura, and impaired growth [6]. An inverse association was found between H. pylori infection and inflammatory bowel disease [7].
The global prevalence of H. pylori infection in adults was significantly higher than in children (48.6% vs. 32.6%, respectively), after an analysis of 410,879 participants from 73 countries on 6 continents [4]. A similar condition was also reported in China (adults 46.1% vs. children and adolescents 28.0%) [8]. The prevalence of pediatric H. pylori infection in Taiwan has varied in the past decades and in different areas. The declining prevalence rate between 1993 and 2012 was shown in a study conducted by Yeung et al., explained by urbanization and public health education regarding proper sanitation and food handling [9].
"Test and treat" strategy for H. pylori infection in children is not recommended [5,10] since no substantial evidence has been documented regarding the health benefits of treatment to eliminate H. pylori infection in children [11]. Testing for H. pylori is suggested in

Methods
Databases including PubMed, Cochrane Library, EMBASE, and Scholar were searched using terms containing (Helicobacter OR Helicobacter pylori OR H. pylori) AND (child OR pediatric) for all relevant abstracts, manuscripts, and guidelines, published from January 2011 to December 2021. The non-human studies and manuscripts that did not involve children or adolescents were excluded. The association and management eligibility were initially screened based on the title and the abstract. Then a full-text assessment was performed with the evaluation of the references in the included studies to identify additional information. The flow chart of literature selection was shown in Figure 1.
The standard triple therapy mentioned in this review included a proton pump inhibitor, amoxicillin, and clarithromycin. The standard sequential therapy included a proton pump inhibitor with amoxicillin for 5 days followed by a proton pump inhibitor with clarithromycin and metronidazole for 5 days. The standard concomitant therapy included proton pump inhibitor, amoxicillin, metronidazole, and clarithromycin for 14 days.
If intention-to-treat analysis and per-protocol analysis were both stated in the relevant articles, the results of the per-protocol analysis were listed in the report to represent the eradication rate.

First-Line Treatment
Current guidelines still recommend standard triple therapy as the first-line treatment for the eradication of H. pylori infection in children worldwide (Table 1). However, the eradication rate did not achieve the desired level in children. As a first-line treatment for pediatric H. pylori infection, sequential therapy had a better eradication rate than triple therapy in recent studies. Huang et al. conducted a systematic review with meta-analysis to compare triple therapy with sequential therapy for treating H. pylori infection in children [19], which included all literature previously reviewed by Horvath et al. [20] except a retracted one. A Cochrane review including 44 randomized controlled trials discussing the issue with only six studies addressing children; however, one study [21] was excluded as the triple therapy using metronidazole instead of clarithromycin [22]. In addition, another study [23] included in the meta-analysis by Huang et el. compared concomitant therapy to sequential therapy instead of standard triple therapy. Additionally, some data reported by Baysoy et al. overlapped with those in the study by Huang et al. Table 2 lists the details of the literature included in this review except for one original article [24], which was not available; therefore, the data was extracted from a systematic review with a meta-analysis collated by Gatta et al. [25]. The treatment dosage mentioned in the associated articles is listed in Table 3. Due to the heterogenicity of the study design, treatment regimen, and follow-up methods, a meta-analysis of these studies was not performed.  [30] (abstract)

China
Not available 100 Standard triple therapy for 10 days * OME + AMO + CLA 69.0% (33) Triple therapy for 10 days * OME + AMO + MET 76.7% (33) Standard sequential therapy for 10 days * OME + AMO for 5 days followed by OME + CLA + MET for 5 days 91.2% (34)    : OME was given once or twice a day, AMO was given three times or four times a day, MET was given twice or three times a day, and BIS was given twice or three times a day.

Sequential Therapy
The eradication rates with standard sequential therapy for 10 days were 80.4-91.2% [28,30,34,39], except for one study with a low eradication rate of 56.1% [38], in which the clarithromycin resistance rate was 25.7%. The eradication rate with standard sequential therapy for 14 days in one prospective study was only 69.5%, lower than standard triple therapy with an eradication rate of 74.1% [40]. The eradication rate with a different regimen using tinidazole instead of metronidazole were 84.6-97.3% [21,23,24,26,27,29,36], except for one study with a low eradication rate of 57.1% [35]. However, the participants in that study were asymptomatic and diagnosed with positive H. pylori immunoglobulin G and urea breath test, which was contrary to the recommendation against "test and treat". One study using amoxicillin-clavulanate instead of amoxicillin in triple therapy and sequential therapy had similar results as the standard therapy mentioned above [32]. Only one study stated a higher eradication rate by standard triple therapy than sequential therapy using ornidazole instead of metronidazole, albeit with low rates in both (54.2% vs. 48.6%, p > 0.05) [37].
Bontems et al., tailored the therapy according to the antimicrobial susceptibility testing. Subgroup analysis indicated that eradication rates tended to be higher using the sequential treatment except for children harboring CLA-resistant strains with a per-protocol eradication rate of 80% in triple therapy and 64% in sequential therapy [28].

Concomitant Therapy
The eradication rate of concomitant therapy regimen using omeprazole, amoxicillin, clarithromycin, and metronidazole for 14 days was 84.6% in one recent study [40]. The eradication rate of concomitant therapy for 5 days with a different regimen using tinidazole instead of metronidazole was 93.3%, higher than 86.7% in sequential therapy for 10 days also using tinidazole in one study [23].

Bismuth-Based Quadruple Therapy
Bismuth-based quadruple therapy, including a proton pump inhibitor, amoxicillin, metronidazole, and bismuth citrate, has been reported in one study with an eradication rate of 83.9%, significantly higher than 67.7% in standard triple therapy [31]. The eradication rate of bismuth-based quadruple therapy could reach 89.8%, which is superior to 74.1% of standard triple therapy in another study [40].

Adjuvant Therapy with Probiotics
Some studies have proposed that probiotics can inhibit H. pylori by immunological and non-immunological mechanisms, including regulating pro-inflammatory cytokines in the gastric mucosa, increasing local IgA concentration, and secreting antibacterial substances such as lactic acid, short-chain fatty acids, hydrogen peroxide and bacteriocin [41]. A tendency of decreasing specific anti-H. pylori IgG antibodies was found with probiotics use in an animal model, yet not to a statistically significant level [42].
A review included eight studies comparing the group treated with antibiotics to those using with same antibiotics therapy plus probiotics. Most of them imply a benefit of the probiotics, but only two studies reached a significant difference [43]. One randomized, double-blind study addressed that the probiotics group experienced less frequent diarrhea, nausea, or vomiting during eradication therapy and a better eradication rate (30/33, 90.9%) compared to the placebo group (23/33, 69.7%) [44]. A meta-analysis including five studies with 484 pediatric patients indicated that Lactobacillus-supplemented triple therapy could increase the eradication rate by approximately 13% (84.0% vs. 71.4%) and reduce the incidence of therapy-related diarrhea [45].
Standard sequential therapy includes a proton pump inhibitor with amoxicillin for 5 days followed by a proton pump inhibitor with clarithromycin and metronidazole for 5 days.

Second-Line Treatment
If eradication fails after first-line therapies, an endoscopy should be performed to obtain specimens for H. pylori culture and antibiotic susceptibility tests to tailor the subsequent therapy [5,10,18,46]. The current recommendation of second-line therapy for pediatric H. pylori infection in Korea is the same as that in the Joint ESPGHAN and NASPGHAN 2016 guidelines (Table 4). Whereas the JSPGHAN 2020 guidelines recommend that a proton pump inhibitor-based triple regimen with amoxicillin and metronidazole for 7 days as second-line therapies if H. pylori strains are resistant to clarithromycin and first-line therapy fails [5].  There was scarce data concerning the efficacy of second-line therapy for the treatment of pediatric H. pylori infection. Only two conference abstracts [47,48] were found ( Table 5). The former was a mono-center, non-randomized, retrospective study that enrolled naïve children with H. pylori infection treated with a sequential regimen, and the initial eradication rate was 82.6% (181/219). Among the 38 children who remained infected, 30 children received second-line treatment, with 24 of them using a tailored triple therapy according to antimicrobial susceptibility test and 6 of them using a repeated sequential therapy; however, eradication rates of both therapies were low (65% and 40%). There were no sufficient details described in the latter. However, the overall eradication rate was only 67.3% after second-line treatment with sequential treatment or triple therapy.

Adverse Event
Adverse events were mentioned in some studies, and most were resolved once the treatment was stopped. Bontems et al. reported abdominal pain found in 20% (sequential 24% vs. triple therapy 17%), diarrhea in 14% (12% vs. 16%), nausea in 6% (8% vs. 5%) and vomiting in 2% (4% vs. 0%) in pediatric patients while receiving H. pylori eradication therapy [28]. Another report on adverse events showed no significant differences between sequential and triple therapy [22]. The overall incidence of adverse events was 12.3%, including rash and diarrhea, with no significant difference in the incidence of adverse effects following standard triple therapy (12.1%), sequential therapy (6.8%), bismuth-based quadruple therapy (15.3%), and concomitant therapy (15.4%) in a Chinese study [40]. Black tongues and dark stool were observed in some children using bismuth-based therapy.

Discussion
Successful eradication of pediatric H. pylori infection depends on the knowledge of H. pylori susceptibility to antibiotics and adherence to treatment [39]. The desirable goal of first-line therapy is at least a 90% eradication rate. A high initial eradication rate will prevent the emergence of antibiotic-resistant strains [15,49]. However, unsatisfactory eradication rates were encountered in pediatric patients with H. pylori infection.
If the strain is known to be susceptible to clarithromycin, both the Joint ESPGHAN and NASPGHAN 2016 guidelines and the JSPGHAN 2020 guidelines recommend the triple combination PPI-CA (proton pump inhibitor, clarithromycin, and amoxicillin) for 14 days as the preferred regimen [5,10]. However, the eradication rates of standard triple therapy for 14 days were only 54.2-67.7%, which is inferior to 80.4 to 91.2% with standard sequential therapy for 10 days in most studies. In the 2016 Cochrane review, sequential therapy was more beneficial than standard triple therapy (76% vs. 64%) but still lower than the eradication rates in the adult population, sequential vs. triple (83% vs. 75%). Lower eradication rates in children than in adults using the same regimen have been reported before. Still, no well-founded explanation was addressed except for some assumptions such as different antibiotic susceptibility or adherence to therapy between children and adults [12]. The different eradication rates between sequential and triple therapy were more impressive in Europe than in Asia, Africa, and South America [22]. However, a relatively low eradication rate of sequential therapy below 70-80% was also reported in four articles [35,37,38,40], which can possibly be attributed to different regional H. pylori resistance rates as two of the articles were performed in Turkey. Another estimated reason is the risk of increasing resistance rate to sequential therapy in recent years as the study conducted by Zhou et al. was performed from 2017 to 2018. Whether prioritizing sequential therapy to triple therapy when antibiotic susceptibility testing is not available is worthy of consideration.
An alternative first-line therapy for pediatric H. pylori infection should be chosen according to the regional H. pylori resistance rate to clarithromycin and metronidazole. H. pylori resistance to antibiotics varies geographically and throughout the decades. A study in Zagreb showed H. pylori resistance to antibiotics in treatment-naïve pediatric patients: clarithromycin (11.9%), metronidazole (10.1%) and amoxicillin (0.6%) [33]. A study using a registry from nine European centers in 2015 reported antibiotic resistance rates: clarithromycin (17.7%) and metronidazole (18.6%) [39]. In Swedish children, 21% (46/222) of H. pylori strains were clarithromycin-resistant from 2005 to 2016 [50]. In a meta-analysis of six studies in Iranian children, the prevalence of resistance to clarithromycin, metronidazole, and ciprofloxacin was 12%, 71%, and 16%, respectively [51]. Much higher resistance to clarithromycin (50.9%), metronidazole (65.3%), but not amoxicillin (0.5%) was shown in children aged 3-15 years old in a Vietnamese study [52]. Overall, the resistance rate to clarithromycin ranged from 11.9% to 50.9%; metronidazole, from 10.1% to 71%; amoxicillin, from 0.5% to 0.6%; ciprofloxacin, 16%, from various regions and periods. Savoldi et al. conducted a systematic review with meta-analysis regarding the antibiotic resistance in H. pylori in World Health Organization (WHO) regions in 2018, including 178 studies and 65 countries, reported resistance rates to clarithromycin, metronidazole, and levofloxacin were 15% in all WHO regions [53]. In Taiwan, Lu et al. conducted a study to investigate the antimicrobial susceptibility of H. pylori isolated from children in southern Taiwan in the past two decades, and the overall antimicrobial resistance rates of clarithromycin and metronidazole were 22.9% and 21.4%, respectively; the dual resistance rate of clarithromycin and metronidazole was 10%, and the resistance rates of levofloxacin and amoxicillin were 8.3% and 2.9%, respectively [54]. Increasing resistance to clarithromycin, metronidazole, and dual resistance to clarithromycin/metronidazole were noted from the period 1998-2008 to the period 2009-2018, from 17.2% to 26.8%, 5.3% to 9.8%, and 6.9% to 12.2%, respectively [54]. Therefore, regional antibiotic resistance should be monitored longitudinally, especially in areas with declining or low eradication rates.
Ideal first-line treatment should be guided by antibiotic susceptibility testing. If H. pylori strains are clarithromycin-resistant, triple therapy with metronidazole and amoxicillin (PPI-MA) is recommended as first-line therapy in the Joint ESPGHAN and NASPGHAN 2016 guidelines [10] and the JSPGHAN 2020 guidelines [5]. However, if the antimicrobial susceptibility of the strain is unknown, the triple combination of PPI-CA for 14 days is still recommended in the JSPGHAN 2020 guidelines [5]. The Joint ESPGHAN and NASPGHAN 2016 guidelines recommend a 14-day bismuth-based therapy or high dose triple therapy with PPI-MA if bismuth is not available [10]. The Korean study by Hong et al. also found that bismuth-PPI-MA (metronidazole-amoxicillin) for 7 days was more effective than standard triple therapy [18,31]. Concomitant therapy is an alternative without susceptibility testing. Anania et al. applied concomitant therapy with PPI-amoxicillin-clarithromycintinidazole for 5 days and achieved a high eradication rate of 93.3%. Zhou et al. compared four different regimens and found only bismuth-based therapy and concomitant therapy showed higher eradication rates [40]. The association with eradication outcome and susceptibility to antimicrobial agents in treatment for children truly exists as the eradication rates were significantly lower with the standard sequential treatment in the case of clarithromycin-resistant strains compared with strains susceptible to both metronidazole and clarithromycin in the study (64% vs. 93%) conducted by Bontems et al. in 2011 [28].
The eradication rate for pediatric H. pylori infection is not satisfactory, whether using first-line or second-line therapies. Standard 10-day sequential therapy seemed more effective (88.3-91.2%) than standard 14-day triple therapy (54.2-74.1%), especially if the strains are susceptible to clarithromycin [28]. However, some studies showed contrary results [37,40]. Some studies showed the addition of probiotics in the treatment regimens mitigated the side effects and improved the eradication rate [43][44][45]. Still, the evidence is not strong enough to be routinely recommended in the society guidelines.
Intrafamilial spreading is an important route of H. pylori transmission [55]. Zhao et al. concluded that whole family-based H. pylori treatment could partially increase the eradication rate in children and reduce recurrence over a single-infected patient treatment strategy [56]. However, family-based eradication therapy needs more research to weigh the benefit and harm of antibiotic exposure to the host and the environment, including the influence on the gut microbiome.

Conclusions
The eradication rates for pediatric H. pylori infection, compared to adult populations, are not satisfactory, no matter using triple, sequential, concomitant, or bismuth-based quadruple therapies, and most studies could not achieve the goal of 90% or above. In addition, the efficacy data of second-line therapy is sparse. Otherwise, retreatment as double resistance strains using high dose amoxicillin plus metronidazole, bismuth-based therapy, or concomitant therapy for 14 days is recommended in current guidelines modified from adult guidelines. However, the treatment protocol still varies by area and is practiced by clinical experience without consensus. The regimen may show superior results compared to other regimens in some studies, but the contrary results may be disclosed in other studies. More studies are required to improve the eradication therapy for pediatric H. pylori infection. The best strategy is still tailored treatment guided by culture with antibiotic sensitivity test and regional data about the eradication rates of different therapies need to be created for the best policy.