Beyond H. pylori: Streptococcal Co-Infections and Their Hidden Impact on Gastric Lesions in Vietnam

Abstract

Background/Objectives: Helicobacter pylori (H. pylori) is a well-established pathogen associated with chronic gastritis and gastric malignancies. Recent studies suggest that members of the Streptococcus anginosus group (SAG), particularly S. anginosus and S. constellatus, may also contribute to gastric mucosal damage, especially when co-infecting with H. pylori. This study aimed to evaluate the prevalence of these three bacterial species and their associations with gastric lesions in Vietnamese patients. Methods: A cross-sectional study was conducted on 200 adult patients with gastritis diagnosed by endoscopy and biopsy. PCR analysed gastric tissue samples from the antrum and corpus for H. pylori, S. anginosus, and S. constellatus. Gastric lesions were classified histologically, and associations with bacterial infections were assessed using odds ratios (OR) and 95% confidence intervals. Results: Infection rates were 62.5% for H. pylori, 62% for S. constellatus, and 48.5% for S. anginosus. Coinfections were frequent, with 25% of patients infected by all three bacteria. Atrophic gastritis was the most common lesion (80%) and was significantly associated with all three bacteria, particularly H. pylori (OR = 7.7), and in co-infections (e.g., H. pylori + S. constellatus, OR = 7.4, p < 0.0001). Triple infection was strongly linked to both atrophy (OR = 5.1) and intestinal metaplasia/dysplasia (OR = 3.4, p = 0.007). Conclusions: Polymicrobial infections involving H. pylori and SAG bacteria are common in Vietnamese patients with gastritis and are significantly associated with more severe gastric lesions. These findings highlight the need for broader microbial screening and integrated management strategies to improve gastritis treatment and gastric cancer prevention in high-prevalence settings.

1. Introduction

Gastritis is a widespread gastrointestinal condition affecting millions globally, particularly in developing countries like Vietnam, where high infection rates, poor hygiene, and dietary habits contribute significantly to disease prevalence [1]. Among the microbial agents implicated, Helicobacter pylori (H. pylori) has long been recognised as a major pathogen responsible for chronic gastritis, peptic ulcer disease, and gastric malignancies [2,3,4]. However, recent studies suggest that other bacteria, such as Streptococcus anginosus (S. anginosus) and Streptococcus constellatus (S. constellatus), members of the Streptococcus anginosus group (SAG), may also play a role in gastric inflammation, potentially interacting with H. pylori to exacerbate mucosal damage [5,6,7].

In Vietnam, gastritis remains a significant public health burden, with H. pylori infection affecting an estimated 50–70% of adults [8,9]. Contributing risk factors include consumption of spicy or unhygienically prepared foods, psychological stress, and frequent use of non-steroidal anti-inflammatory drugs (NSAIDS) [10,11,12,13]. Despite evidence from international studies indicating that SAG members can act as opportunistic pathogens, their role in gastric disease, especially in co-infection with H. pylori [6,14,15], is almost unstudied in Vietnam [16]. Co-infections may amplify mucosal inflammation, accelerate atrophic processes, and potentially increase the risk of precancerous lesions such as intestinal metaplasia or dysplasia [2,15,17].

Given the limited local data, this study was conducted to: (i) determine the prevalence of H. pylori, S. anginosus, and S. constellatus in Vietnamese patients with gastritis; (ii) evaluate the associations between bacterial infections (mono- and coinfections) and different types of gastric lesions; and (iii) provide a scientific basis for improving diagnosis and treatment strategies for gastritis in Vietnam.

2. Materials and Methods

2.1. Study Population

This cross-sectional study included 200 patients diagnosed with gastritis based on upper gastrointestinal endoscopy and biopsy at 108 Military Central Hospital between January 2023 and June 2024 (No 1229/HDDD, approved date: 15 March 2023, by the Institutional Review Board of 108 Military Central Hospital). The inclusion criteria were age ≥ 18 years, clinical symptoms of gastritis (epigastric pain, nausea, or dyspepsia), and informed consent. Exclusion criteria included recent use (within four weeks) of antibiotics, proton pump inhibitors, or NSAIDS; history of gastric or duodenal cancer; or prior gastric resection.

2.2. Data Collection

Upper GI endoscopy was performed using high definition flexible gastroscopes (Olympus GIF-H190, Olympus Corporation, Tokyo, Japan) with narrow band imaging (NBI) to improve visualization of mucosal lesions and allow for targeted biopsies. Examinations were conducted by experienced, board-certified gastroenterologists from the Institute of Gastroenterology and Hepatology in 108 Military Central Hospital with a minimum of 10 years’ experience in diagnostic upper GI endoscopy practising as specialists. Gastric lesions were classified based on endoscopic and histopathological findings, including edematous/hyperemic gastritis, erosive gastritis, ulceration, atrophic gastritis, and intestinal metaplasia/dysplasia. Gastric tissue samples were collected from the antrum and corpus based on the updated Sydney System protocol for the histological typing of gastritis. The urease test was performed first in all samples to check the presence of H. pylori. Subsequently, total DNA was extracted from the tissue, and qPCR using SYBR Green with primer sequences as described previously [18], was performed to detect the presence of H. pylori, S. anginosus, and S. constellatus. Clinical data, including age, sex, symptoms, and laboratory results, were also documented in detail.

2.3. Statistical Analysis

The prevalence of bacterial infections and associated gastric lesions was presented as counts and percentages. Associations between infection status and lesion types were assessed using odds ratios (OR) with 95% confidence intervals (CI). A p-value < 0.05 was considered statistically significant. Analyses were performed using SPSS version 25.0 (IBM Corp., Armonk, NY, USA).

3. Results

3.1. Bacterial Prevalence

The prevalence of the three bacterial species in gastric tissue samples from the 200 study patients is described in

Table 1. Prevalence of bacterial infections in 200 gastritis patients.

Bacteria/Combination	Number of Patients	Percentage (%)
Helicobacter pylori	125	62.5
Streptococcus anginosus	97	48.5
Streptococcus constellatus	124	62
Co-infection of H. pylori and S. anginosus	64	32
Co-infection of H. pylori and S. constellatus	76	38
Co-infection of S. anginosus and S. constellatus	76	38
Triple infection	50	25

H. pylori, Helicobacter pylori; S. anginosus, Streptococcus anginosus; S. constellatus, Streptococcus constellatus.

. Among 200 patients, H. pylori was detected in 62.5% (125 cases), S. constellatus in 62% (124 cases), and S. anginosus in 48.5% (97 cases). Coinfection was common, with 32% coinfected with H. pylori and S. anginosus, 38% with H. pylori and S. constellatus, and 38% with S. anginosus and S. constellatus. Notably, 25% of patients (50 cases) were infected by all three bacterial species.

3.2. Gastric Lesion Patterns

The most frequently observed lesion was mucosal atrophy (80%, 160/200), followed by erythematous gastritis (68%, 136/200), erosions (51.5%, 103/200), intestinal metaplasia/dysplasia (16%, 32/200), and ulcers (10.5%, 21/200) (

Table 2. Classification of gastric lesions in 200 patients.

Lesion Type	Number of Patients	Percentage (%)
Edematous/erythematous gastritis	136	68
Erosive gastritis	103	51.5
Ulcers	21	10.5
Atrophic gastritis	160	80
Metaplasia/dysplasia	32	16

).

3.3. Association Between Bacteria and Gastric Lesions

The association between bacterial presence and gastric lesions is presented in

Table 3. Associations between bacterial infections and types of gastric lesions in 200 Vietnamese gastritis patients. Odds ratios (OR) with 95% confidence intervals (CI) were calculated to assess the likelihood of each lesion type concerning specific bacterial infection patterns. Statistical significance was evaluated using the chi-square or Fisher’s exact test, with a p-value of <0.05 considered significant. Bolded values indicate statistically significant associations. OR, Odds ratio; CI, Confidence interval; H. pylori, Helicobacter pylori; S. anginosus, Streptococcus anginosus; S. constellatus, Streptococcus constellatus.

	Edematous/ Erythematous Gastritis		Erosive Gastritis		Ulcers		Atrophic Gastritis		Metaplasia/Dysplasia
	OR [95% CI]	p Value	OR [95% CI]	p Value	OR [95% CI]	p Value	OR [95% CI]	p Value	OR [95% CI]	p Value
Helicobacter pylori	1.8 [0.9–3.2]	0.08	0.8 [0.5–1.4]	0.6	6.5 [1.6–28.9]	0.01	7.7 [3.4–16.4]	<0.0001	2.3 [0.9–5.8]	0.9
Streptococcus anginosus	0.6 [0.3–1.1]	0.09	1 [0.8–1.3]	0.9	1.5 [0.6–3.5]	0.5	5.0 [2.1–10.8]	0.0001	2.0 [0.9–4.5]	0.1
Streptococcus constellatus	0.9 [0.8–1.2]	0.3	0.6 [0.3–1.1]	0.1	0.8 [0.3–1.9]	0.8	2.1 [1.0–4.3]	0.04	1.9 [0.8–4.9]	0.2
Co-infection of H. pylori and S. anginosus	1.0 [0.8–1.23]	0.9	0.7 [0.4–1.3]	0.3	2.6 [1.1–6.7]	0.04	4.1 [1.5–10.0]	0.002	2.6 [1.2–6.1]	0.03
Co-infection of H. pylori and S. constellatus	1.1 [0.6–2.1]	0.8	0.6 [0.4–1.1]	0.1	1.9 [0.8–4.8]	0.2	7.4 [2.7–19.9]	<0.0001	2.7 [1.2–6.0]	0.02
Co-infection of S. anginosus and S. constellatus	0.8 [0.4–1.4]	0.8	0.8 [0.5–1.5]	0.6	1.3 [0.5–2.9]	0.6	7.4 [2.7–19.9]	<0.0001	2.3 [1.0–5.4]	0.05
Triple infection	1.0 [0.8–1.2]	0.9	0.7 [0.4–1.3]	0.2	2.5 [1.1–6.2]	0.06	5.1 [1.6–16.4]	0.004	3.4 [1.4–7.9]	0.007

. H. pylori infection was significantly associated with gastric ulcers (OR = 6.5, 95% CI: 1.6–28.9, p = 0.01) and mucosal atrophy (OR = 7.7, 95% CI: 3.4–16.4, p < 0.0001). Both S. anginosus (OR = 5.0, p < 0.05) and S. constellatus (OR = 2.1, p < 0.05) were also linked to atrophic changes. Coinfection with H. pylori and S. anginosus increased the risk of ulcers (OR = 2.6, p = 0.04), atrophy (OR = 4.1, p = 0.002), and intestinal metaplasia/dysplasia (OR = 2.6, p = 0.03). Coinfection with H. pylori and S. constellatus was strongly associated with atrophy (OR = 7.4, p < 0.0001) and metaplasia/dysplasia (OR = 2.7, p = 0.02). Triple infection was linked to the highest risk of atrophic gastritis (OR = 5.1, p = 0.004) and intestinal metaplasia/dysplasia (OR = 3.4, p = 0.007) (Table 3).

4. Discussion

This study provides valuable insights into the epidemiology of Helicobacter pylori (H. pylori), Streptococcus anginosus (S. anginosus), and Streptococcus constellatus (S. constellatus) infections in patients with gastritis in Vietnam, while also shedding light on the role of bacterial co-infections in exacerbating gastric lesions. Two hundred individuals were included in the study, to whom a diagnosis of gastritis was made at UGI endoscopy and biopsy. Exclusion criteria were use of antibiotics, PPIs, or nonsteroidal anti-inflammatory drugs (NSAIDs) in the four weeks before inclusion; a previous diagnosis of gastric or duodenal cancer; and previous gastric surgery. Given the possibility that antibiotics, PPIs, and NSAIDs might result in biased microbial identification by inhibiting H. pylori colonisation or altering gastric microbiota composition, and thereby impairing PCR assays for H. pylori, S. anginosus, and S. constellatus, treatment with these drugs was restricted for 4 weeks prior to sample collection. Nevertheless, the analysis did not account for a structured evaluation of long pre-exposure (>four weeks), and there could be residual biases if previous treatment sustained over time altered the gastric ecosystem.

The prevalence of H. pylori infection (62.5%) in this study is consistent with reports from other Asian countries, where H. pylori has been documented at rates ranging from 50% to 70% in countries such as China, India, and Vietnam [19,20]. However, the observed rates of SAG bacteria (S. anginosus 48.5% and S. constellatus 62%) were notably higher than those reported in Western studies (20–30%), suggesting geographic or environmental differences in gastric microbiota composition [14].

The key finding of this study is the high co-infection rate, particularly the simultaneous presence of all three bacterial species (25%). This highlights the complex interactions between H. pylori and the S. anginosus group (SAG) within the gastric environment. Previous studies have demonstrated that H. pylori can alter the gastric microbiota, thereby facilitating the colonization and proliferation of opportunistic bacteria such as S. anginosus and S. constellatus [5,21]. Co-infection with S. anginosus and S. constellatus may potentiate a heightened inflammatory response, promoting increased cytokine production and mucosal damage, as evidenced by their strong association with atrophic gastritis (OR = 7.4, p < 0.0001) and intestinal metaplasia/dysplasia (OR = 3.4, p = 0.007).

Atrophic gastritis, identified as the most prevalent lesion in this study (80%), is a chronic pathological condition frequently linked to prolonged H. pylori infection [22]. In addition, its occurrence may also be associated with colonization by S. anginosus or S. constellatus (Table 3). Our analysis revealed that infection with any of the three bacterial species was significantly correlated with an increased risk of developing atrophic gastritis (OR = 7.7 for H. pylori; OR = 5.0 for S. anginosus; OR = 2.1 for S. constellatus). Notably, bacterial co-infections appeared to exert a synergistic effect, further elevating the risk of atrophic changes. Co-infection with H. pylori and S. constellatus was strongly associated with atrophic gastritis (OR = 7.4, p < 0.0001), likely due to their combined contribution to epithelial injury and sustained inflammatory responses. Likewise, the risk of gastric ulceration was significantly increased in patients harboring H. pylori alone (OR = 6.5, p = 0.01) or co-infected with H. pylori and S. anginosus (OR = 2.6, p = 0.04), consistent with previous findings regarding H. pylori’s role in compromising the gastric mucosal barrier and promoting ulcer formation [23].

Notably, intestinal metaplasia and dysplasia—precancerous lesions—were significantly associated with triple infection involving all three bacterial species (OR = 3.4, p = 0.007). This suggests that the simultaneous presence of H. pylori, S. anginosus, and S. constellatus may promote malignant transformation through mechanisms such as increased oxidative stress, DNA damage, and disruption of microbial homeostasis [24]. In addition, metaplasia/dysplasia was also closely associated with dual infections involving H. pylori (Table 3). This finding is particularly relevant in the context of Vietnam, where H. pylori prevalence is high, and antibiotic resistance remains a growing concern. Our results provide further scientific evidence linking the rising burden of gastric cancer in Vietnam with H. pylori infection [25,26].

Although the specific molecular mechanisms by which SAG bacteria exert a synergistic effect on gastric pathogenesis remain to be tested in experiments, the contributions of components such as nutritional stress and enhanced resistance to inflammation may be deduced from well-defined streptococcal virulence factors. For instance, SAG strains may contribute to local inflammatory reaction by secretion of virulence factor(s) (e.g., hemolysins, proteases, and DNase) that can enhance this process. These factors induce an excess secretion of proinflammatory cytokines such as IL-1β, IL-6, and TNF-α from the gastric epithelial cells along with immune cells. This interaction enhances the Helicobacter pylori-induced inflammatory milieu and sustains ongoing tissue injury [6,15]. Furthermore, SAG-driven immunomodulation could potentially emerge via resistance against host innate immunity as SAG nuclease-induced cleavage of neutrophil extracellular traps (NETs) causes compromised bacterial clearance, disturbed activity of the innate signaling cascade and expansion toward chronic inflammatory environment where epithelial metaplasia and dysplasia can develop. These cross-linked pathways are likely to collaborate in the polymicrobial setting to drive gastritis toward pre-malignancy, especially when coinfected with H. pylori. Validation using advanced experimental models, including organoid systems, murine infection models and proteomic identifications, is required to test these hypotheses and support the development of specific therapeutics [5,6,7,15].

In comparison to international studies, our research offers new insights into the roles of S. anginosus and S. constellatus in gastritis, a topic that remains underexplored. Nevertheless, this study has several limitations. First, this cross-sectional study design does not allow for the proof of causality between bacterial infections and gastric lesions, as associations are recorded at a single point in time without consideration of timing. Second, the sample size of 200 patients is not sufficient to represent all Vietnamese patients. Third, other potential risk factors, such as dietary habits, smoking, or socioeconomic status, have not been evaluated in this study, which could affect bacterial colonisation and lesion severity. Fourth, in the absence of bacterial culture, other components of the gastric microbiota might be under-detected due to the inherent limitations of PCR alone. Furthermore, NGS-based methods can be applied to analyse the entire gastric microbiome in a more comprehensive manner and may have potential explanatory power at the exposure level. Furthermore, for verifying the relationship between H. pylori, S. anginosus, and S. constellatus in relation to lesion progression, prospective cohort studies and mechanistic studies (in vitro or animal models) are also necessary.

From a clinical perspective, our findings emphasize the importance of testing for bacterial co-infections in diagnosing gastritis. Treatment strategies should consider broad-spectrum or combination antibiotics targeting H. pylori and SAG bacteria. Moreover, long-term monitoring of patients with co-infections and lesions such as intestinal metaplasia or dysplasia is essential for the early detection of gastric cancer risk.

5. Conclusions

This study highlights the high prevalence of Helicobacter pylori, Streptococcus anginosus, and Streptococcus constellatus in Vietnamese patients with gastritis and underscores their individual and combined contributions to gastric mucosal damage. Notably, coinfections—especially involving all three bacteria—were significantly associated with more severe lesions such as atrophic gastritis and intestinal metaplasia/dysplasia. These findings suggest that counseling for gastritis in Vietnam should consider polymicrobial infections. Broader microbial screening and long-term follow-up may help identify high-risk patients early and improve gastric cancer prevention strategies in high-burden settings.