The use of Helicobacter pylori stool antigen test for the diagnosis of Helicobacter pylori in Lagos, Nigeria

OBJECTIVES

This study was carried out to screen the use of Helicobacter pylori stool antigen (HpSA) tests for diagnosis and monitoring of H pylori in Nigeria.

METHODS

Seven hundred and forty participants were enrolled after informed consent was obtained, while 83 came back for a post-eradication test. The stool samples were taken from the patients at endoscopy and tested for HpSA.

RESULTS

The proportion of patients that were positive at the pretest, 520 (70.3%) was significantly higher (Fisher's exact p = 0.001) than those positive at the post-test, 44 (53%). There was a significant difference (F = 4.106, p = 0.043) between the mean age of those that came for the pretest (40.0 +/- 14.5 years) and those that came for the post-test, 43.6 +/- 11.6 years. More males than females had the tendency to come back for a post-eradication test.

CONCLUSION

Although potential bias was introduced during this study, HpSA using monoclonal antibody could still be used for diagnosis and monitoring of H pylori in Nigeria.

Antibiotic susceptibility patterns in Helicobacter pylori strains from patients with upper gastrointestinal pathology in western Nigeria

A total of 186 Helicobacter pylori isolates and 532 gastric biopsies recovered from 532 patients with varying degrees of gastroduodenal pathology are subjected to in vitro antibiotic susceptibility testing using the disc-diffusion method, Etest (MIC breakpoints) and molecular testing using the polymerase chain reaction (PCR). In the isolates studied, antibiotic resistance was as follows: piperacillin (72%), amoxicillin (66%), erythromycin (78%), tetracycline (100%) and metronidazole (95%). All isolates were sensitive to ofloxacin, ciprofloxacin and norfloxacin. None of the 245 amplicons (positive for H. pylori) from the biopsies were digested with the Bbs1 and Bsal restriction enzyme used in the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique, showing sensitivity to clarithromycin. However, a 238 bp fragment from H. pylori chromosomal DNA (corresponding to the quinolone resistance determining region [QRDR]) of the gyrA gene was amplified successfully. Twelve (4.9%) of the 245 strains studied had the described mutation at position 91, from asparagine (Asn) to glycine (Gly). The study showed that all the H. pylori strains were sensitive to clarithromycin and ciprofloxacin. It also highlighted PCR as a potential tool for faster diagnosis and determination of antibiotic susceptibility (within 24 h) of H. pylori from biopsies and/or isolates recovered from peptic ulcer and gastritis patients.

Fingerprinting of Nigerian Helicobacter pylori isolates by plasmid profile and PCR

Plasmid profiling and digestion of amplified PCR product of ureA genes were used to determine genomic variation in 56 strains of Helicobacter pylori isolated from patients with peptic ulcers and subjects with gastritis recruited in Lagos and Ife, Nigeria. Twenty-five (45%) of the strains were found to harbour plasmids ranging in size from 0.9 kb to > 10 kb. The plasmid profile was able to detect differences between the strains, and also to distinguish between different strains isolated from the same patient. The expected amplified ureA gene PCR product was detected in all strains and digestion with the restriction enzyme DdeI did not produce discrimination amongst the strains, however, digestion with MluI produced little discrimination amongst strains. In conclusion, plasmid profiling produced better discrimination amongst H. pylori strains than ureA PCR gene profiling.

Use of direct Gram stain of stomach biopsy as a rapid screening method for detection of Helicobacter pylori from peptic ulcer and gastritis patients

Four hundred and thirty five stomach mucosal biopsies were taken from 145 consecutive patients (3 from each patient) during investigations for dyspepsia in three hospitals in Western Nigeria. The aim was to determine the best suited rapid screening method to aid fast diagnosis of ulcer/gastritis in this environment, using Gram stain, CLO test kit (urease production test) and culture methods. Eighty-nine (61.4%) biopsies were positive using Gram stain, 61 (42.1%) using CLO test kit and only 28 (19.3%) using culture. Based on the various limitations of CLO test kits and culture methods, Gram stain was adjudged the best suited rapid method. The clinical implication of this finding is discussed.

Use of direct Gram stain of stomach biopsy as a rapid screening method for detection of Helicobacter pylori from peptic ulcer and gastritis patients

Four hundred and thirty five stomach mucosal biopsies were taken from 145 consecutive patients (3 from each patient) during investigations for dyspepsia in three hospitals in Western Nigeria. The aim was to determine the best suited rapid screening method to aid fast diagnosis of ulcer/gastritis in this environment, using Gram stain, CLO test kit (urease production test) and culture methods. Eighty-nine (61.4%) biopsies were positive using Gram stain, 61 (42.1%) using CLO test kit and only 28 (19.3%) using culture. Based on the various limitations of CLO test kits and culture methods, Gram stain was adjudged the best suited rapid method. The clinical implication of this finding is discussed.

Evaluation of a locally-made urease test for detecting Helicobacter pylori infection

We studied the efficacy of a home-made urease test (HUT) in the detection of Helicobacter pylori (HP) infection in patients undergoing upper gastrointestinal endoscopy. In the first phase of the study, two antral biopsies each were obtained from 43 patients for urease tests using the CLOtest and a home-made buffered 2% urea solution with phenol red as indicator at pH 6.8 (2% HUT). Twenty-six patients (60.5%) were HP positive, both by the 2% HUT and CLOtest with 100% concordance. In the second phase of the study three antral biopsies each and blood were obtained from 42 patients for the determination of HP status using a 10% HUT and a combination of culture and serology. Twenty-three patients (54.8%) were HP positive using the 10% HUT, while 32 patients (76.2%) were positive using the combination of 2 tests. Compared to this the sensitivity and specificity of the 10% HUT were 72% and 100% respectively. The CLOtest produced a colour change in a shorter time than the 2% and 10% HUT (median 1 hour versus 10 hours versus 16 hours p < 0.0001). In the third phase of the study, we observed that by doubling the biopsy size, the time required to obtain a colour change was significantly reduced (median 4.5 hours versus 10 hours p < 0.05). The HUT is easy to prepare, cheap, sufficiently sensitive and it is reliable enough to start treatment when positive. With 100% concordance and 1% the cost per test when compared to the commercially available CLOtest; the 10% HUT is hereby recommended for the detection of UP infection in our region.

Lactobacilli in human dental caries and saliva

Samples (98 plaque and 72 saliva) from 93 patients with dental caries were investigated for Lactobacillus species which comprised 65 (62.5%) of 104 isolates. Yeasts (20.1%), Streptococcus spp. (8.7%), Staphylococcus spp. (2.9%) and a few unidentified species (5.8%), were also found. The Lactobacillus isolates were L. brevis (24.6%) L. fermentum (18.5%) L. casei (16.9%), L. delbrueckii (15.4%), L. plantarum (9.23%), L. acidophilus (7.69%), L. jensenii (4.62%), L. salivarius (1.54%) and L. gasseri (1.54%). The most common species was L. brevis (24.6%). The strains tested for beta-lactamase production showed 75.4% positive. All the Lactobacillus strains were tested for bacteriocin production against Escherichia coli, Salmonella spp., Shigella dysenteriae, S. sonnei, Klebsiella spp. and Campylobacter sp. All the lactobacilli except L. jensenii produced bacteriocin against at least one of the indicator organisms. The involvement of Lactobacillus in dental caries was established, although its role and mechanism is not well understood. The ability of Lactobacillus spp. to protect their host against certain diseases by inhibiting the growth of potential pathogens was evident.

Gastric antral juxtamucosal pH in helicobacter pylori positive and negative dyspeptic patients

Maintenance of gastric juxtamucosal pH at a stable near neutral value may be the cumulative effect of the various components of the mucosal defense system. In order to assess the effect of helicobacter pylori (HP) infection on mucosal defense, we measured the gastric antral juxtamucosal pH in 40 dyspeptic patients by using a flexible glass pH microelectrode which can be passed down the instrument channel of standard gastroscopes. HP status was determined using serology, culture, histology and urease test. We also investigated the relationship between juxtamucosal pH and the severity of antral HP infection. The mean antral juxtamucosal pH in 26 (65%) HP positive patients was 6.49 +/- 0.20 compared to 6.19 +/- 0.21 in 14 (35%) HP negative patients (p < 0.00001). Other factors like age, sex, duodenogastric reflux or presence of chronic duodenal ulcer did not significantly affect juxtamucosal pH (p > 0.05). Subset analysis of data on HP positive patients (n = 26) revealed no significant correlations between antral chronic gastritis anti-HP IgG titre and antral juxtamucosal pH (p > 0.05). This study shows that HP increases gastric antral juxtamucosal pH. This finding supports the suggested role of HP in producing hypergastrinaemia and gastric acid hypersecretion.

Gastric acid secretion in Helicobacter pylori positive and negative dyspeptic Nigerians

The pathological role of Helicobacter pylori is largely unproven in our region of high incidence of infection but very low incidence of serious gastroduodenal lesions. The aim of this study was to investigate the effect of H. pylori infection on gastric acid secretion. One week after gastroduodenoscopy, basal and pentagastrin (8 micrograms/kg) stimulated gastric acid secretion were measured in 39 dyspeptic Nigerians. H. pylori status was determined using urease test, culture, histology and serology, while gastritis was assessed using the Sydney system criteria. The median maximal acid output (MAO) and peak acid output (PAO) in mmol/h were significantly higher in H. pylori positive (29.3, range 7.4-81.6 and 34.4, range 7.6-144.0) than in H. pylori negative (16.6, range 4.2-44.1 and 22.4, range 5.6-48.6) patients, p = 0.019 and p = 0.029, respectively. Stimulated gastric acid secretion was significantly higher in patients with duodenal ulcer (n = 8) than in H. pylori negative (n = 11) patients, but was similar in non-ulcer dyspeptics (n = 20) and H. pylori negative patients. The median basal acid output was not significantly different between the groups of patients. Our patients (median age 32 years) had normal mucosa (12.1%), pangastritis with corpus predominance (12.1%), antrum-only gastritis (24.3%) and pangastritis with antral predominance (51.5%). In the subset of H. pylori positive patients (n = 28, 71.8%), there were no significant correlations between grade of antral chronic inflammation, gastritis index score, anti-H. pylori IgG titre and gastric acid secretion, p > 0.05. H. pylori infection increases MAO and PAO in our relatively young patients with antral predominant chronic gastritis.