ISOLATION OF CagA AND VacA GENES FROM H . PYLORI INFECTED PATIENTS WITH VARIOUS GASTRODUODENAL LESIONS

This study aimed to learn the incidence of Helicobacter pylori infection in patients with various gastroduodenal endoscopic lesions and the frequency of virulence H.pylori associated genes CagA and VacA in these patients. One hundred seventy six patients (96 males and 80 females) attending endoscopy units for various dyspeptic symptoms were studied. Antral biopsies were obtained to detect H.pylori by rapid urease test, culturing and histopathologic examination. Twenty five patients with positive H.pylori isolates who were found to be mannose resistant, were tested for cytotoxic associated (CagA) and vacuolating cytotoxin A (VacA) genes. Among studied patients, positive H.pylori detected by rapid urease test, culturing and histopathologic examination (from 50 patients only) were 113 (63%), 127 (71%) and 25 (50%) respectively. Out of 25 patients with positive H.pylori isolates who were found to be mannose resistant, positive genes of either CagA or VacA were detected in 18 (72%) patients with positive isolates, while positivity of both genes were detected in 13(52%) patients with positive isolates. Five (45.4%) and 5 (45.4%) out of patients with duodenal ulcers and gastritis respectively were positive for both (CagA) and (VacA) genes. In conclusion, the highest detection rate of H.pylori infection was by bacterial culture. A correlation between CagA and VacA genes and endoscopic lesions of duodenal ulcers and gastritis was found. Introduction .pylori is a human specific pathogen lives deep beneath the mucus layer closely attached to the gastric epithelium. The infection with H. pylori is the most frequent infection worldwide as more than half of the world's population are infected. H. pylori is now recognized as the cause of gastritis and most cases of peptic ulcer disease. Its long term carriage increases the risk of gastric adenocarcinoma six times and it is designated as a class I carcinogen. H. pylori has also been implicated as a cause of gastric mucosa associated lymphoid tissue (MALT) lymphomas. It is estimated that 0.4–1.0% of uninfected adults acquire H. pylori each year, and the incidence of H. pylori infection tends to increase with age. However, detailed information of the prevalence of the bacteria in developing countries and on the factors that may influence the pattern of distribution remains scanty. The main risk factors for H. pylori acquisition are childhood, low H Isolation of CagA and VacA genes from H.pylori Mohamed H Khudor, Sarkis K Strak & Awatif H Issa Bas J Surg, March, 16, 2010 ٣٢ socio-economic status, the presence of H. pylori positive family members, and poor sanitation. The mechanism by which H. pylori causes gastric mucosal damage and peptic ulcer is not fully elucidated, but it is clear that it involves several H. pylori virulence factors enabling it to survive within the strong gastric acid. In addition, host dependent noxious substances lead to progressive damage to the gastric mucosa, deregulation of acid production, induction of gastric metaplasia and development of chronic gastritis. These H. pylori virulence factors and host noxious substances include cytotoxin associated gene A (CagA), vacuolating cytotoxin A (VacA), ammonia, lipopolysaccharide (endotoxin), platelet activating factors, nitric oxide and interleukin–8 . Vac A cytotoxin, which is synthesized as a 140KDa precursor and released from the bacterium as a 95KDa mature toxin. Vac A cytotoxin secreted by about 50% of H. pylori isolates in western countries. Infection with vacuolating cytotoxin positive strains is reported to be associated with peptic ulcer disease. They showed that strains with vacuolating cytotoxin activity were found in 16 out of 24(67%) patients with peptic ulcers but in only 16 of 53 (30%) patients without. Infection with H. pylori strain expressing cytotoxin associated Cag A protein is more virulent and is associated with increased risk of development gastric cancer. There is evidence that Cag A positive strains are more infectious , achieve higher bacterial density on the gastric mucosa and cause more inflammation than Cag A negative strains. Cag A positive H. pylori strains have been shown to be associated with interleukin–8 (IL.8) induction in gastric epithelium, neutrophilic infiltration and thus be related to gastric inflammation and gastroduoderal diseases. Expression of Cag A protein is closely associated with that of vacuolating cytotoxin, although the underlying mechanism is not understood,thus Xiang et al. classified H. pylori strains in two groups type I and type II. These studies stated that type I strains, which are positive for both Vac A and CagA, were strongly associated with peptic ulcer diseases in the host. The present study was conducted with the following objectives; To show the incidence of Helicobacter Pylori in patients with variable gastroduodenal endoscopic lesions. To study the frequency of virulence associated genes Cag A and Vac A in the studied patients with positive H. pylori isolates. Patients and methods A total of 176 patients 96 males and 80 females, whose ages ranged from 14 – 80 years, with various dyspeptic symptoms attending endoscopy unit at Al-sadder Teaching Hospital (Basrah) during the period from October 2004 through August 2005 were underwent upper gastroduodenal endoscopic examination. Patients with recent upper gastrointestinal bleeding, on nonsteroidal anti inflammatory drugs, antibiotics or proton pump inhibitors were excluded from the study. Two antral biopsy samples were obtained from each patient one for rapid urease test and the second for bacterial culturing as described by Barn et a. A third biopsy sample was obtained from (50 patients only) due to cost constraints for histologic examination. Culture colonies that exhibited characteristic morphologies were studied also biochemically by catalase and oxidase according to Finegold and Baron to confirm the identity of positive H. pylori isolates. Patients from whom H. pylori were isolated and identified biochemically were studied for toxigenic strains by mannose resistant heamagglutination test (MRHA). Isolation of CagA and VacA genes from H.pylori Mohamed H Khudor, Sarkis K Strak & Awatif H Issa Bas J Surg, March, 16, 2010 ٣٣ Grown cultures were suspended in phosphate buffer saline (PBS) at pH. 7.2, and tested against human erythrocyte. Blood was drawn from volunteer donors and placed into a tube containing 1.0 ml of 3.8% citric acid, in distilled water per 9.0 ml of blood. Blood was diluted 1:4 with PBS to test for mannose resistant haemagglutination. MRHA test was performed by mixing equal volume of each bacterial suspension with erythrocyte suspension, with and without (1%) D-mannose, in PBS. Glass tile with round depressions were rocked gently with swirling action at (20–22C). Mixture was subsequently incubated at (4 C)for up to (20 min) before reading. Positive toxigenic strains, which revealed haemagglutination with erythrocyte cells, were preceded by polymerase chain reaction (PCR) technique by using primer sequences. table I. Table I:Oligonucleotide primer sequences of Cag A and Vac A for H. pylori clinical isolates A T m L en th Primer sequences P im rs 56C 48C ١٨ 5AGTAAGGAGAAACAATGA-3 Forward CagA gene ٥٦C 74C 28 5-AATAAGCCTTAGAGTCTTTTTGGAAATC-3 Reverse A T m L en th Primer sequences P im rs 55C 60C ٢٠ 5-GCTTCTCTTACCACCAATGC-3 Forward VacA gene ٥٥C 60C 20 5-TGTCAGGGTTGTTCACCATG-3 Reverse *Tm= melting temperature, TA= Annealing temperature Results Sex and age distribution of patients are illustrated in table II. Ninety-six (54%) and 80(45.5%) were males and females respectively. Forty-nine (52%) of males and 46 (57.5%) of females showed positive H. pylori isolates by culture, the differences were statistically not significant (P>0.05). Table II: Age and sex distribution of patients with H. pylori infection. Sex Age groups (years) ≤20 21–30 31–40 41–50 51–60 > 60 Total Male +/total 0/2 9/18 15/31 7/11 7/14 11/20 49/96 % 0% 50% 48.4% 63.6% 50% 55% 52% Female +/total 2/5 8/14 5/11 10/19 10/16 11/15 46/80 % 40% 57.1% 45.6% 52.6% 62.5% 73.3% 57.5% Total +/total 2/7 17/32 20/42 17/30 17/30 22/35 % 28.5% 53.1% 47.6% 56.7% 56.7% 62.8% Isolation of CagA and VacA genes from H.pylori Mohamed H Khudor, Sarkis K Strak & Awatif H Issa Bas J Surg, March, 16, 2010 ٣٤ The highest detection of H. pylori isolates was recorded in the age group more than 60 years 22/35 (62.8%), while the lowest detection rate was recorded in the age group below 20 years 2/7 (28.5%), the differences were statistically not significant (p>0.05). Out of 176 studied patients ,124 (70.4%) showed abnormal endoscopic findings. In 52 (29.5%) patients, the endoscopic examination was normal table III. Table III: Endoscopic findings, Rapid urease test&culture results in studied cases. Endoscopic findings Total No. No. and (%) of RUT +ve patients No. and (%) of Culture +ve patients Ca. Stomach 10 6 (60) 10(100) Gastric ulcer 19 13(69) 15(79) Duodenal ulcer 12 8 (67) 9(75) Gastric and duodenal ulcer 1 1(100) 1(100) Gastritis and gastric ulcer 4 2(50) 4(100) Gastritis 62 40(64.5) 43(70) Gastritis and duodenitis 5 3(60) 5(100) Gastritis and duodenal ulcer 6 4(67) 5(83.3) Duodenitis 5 4(80) 5(100) Total 124 81(64) 97(77) Normal 52 32(61.5) 30(57.6) Total 176 113(64.2%) 127(72.2%) Table III also shows positive H. pylori cases detected by (RUT) and culture. RUT and culture were positive in 81 (64%) and 97 (77%) out of 124 with positive endoscopic lesions respectively, while RUT and culture were positive in 32 (61.5%) and 30 (57.6%) out of 52 with normal endoscopic examination. Table IV shows the histopathologic findings and positive H. pylori among 50 of examined biopsy specimens, 24 (48%) of biopsy specimens showed abnormal histopathological findings. H. pylori was positive in 3 (75%) 6 (54.5%) and 3 (33.3%) of histopathologic specimens with severe, moderate and mild gastritis respectively, 26 (52%) of biopsy specimens showed normal gastri


Introduction
.pylori is a human specific pathogen lives deep beneath the mucus layer closely attached to the gastric epithelium 1 .The infection with H. pylori is the most frequent infection worldwide as more than half of the world's population are infected 2 .H. pylori is now recognized as the cause of gastritis and most cases of peptic ulcer disease.Its long term carriage increases the risk of gastric adenocarcinoma six times and it is designated as a class I carcinogen 3 .H. pylori has also been implicated as a cause of gastric mucosa associated lymphoid tissue (MALT) lymphomas. 4t is estimated that 0.4-1.0% of uninfected adults acquire H.pylori each year, and the incidence of H. pylori infection tends to increase with age 5 .However, detailed information of the prevalence of the bacteria in developing countries and on the factors that may influence the pattern of distribution remains scanty.The main risk factors for H. pylori acquisition are childhood, low H Bas J Surg, March, 16, 2010 ٣٢ socio-economic status, the presence of H. pylori positive family members, and poor sanitation 6,7 .The mechanism by which H. pylori causes gastric mucosal damage and peptic ulcer is not fully elucidated, but it is clear that it involves several H. pylori virulence factors enabling it to survive within the strong gastric acid.In addition, host dependent noxious substances lead to progressive damage to the gastric mucosa, deregulation of acid production, induction of gastric metaplasia and development of chronic gastritis.These H. pylori virulence factors and host noxious substances include cytotoxin associated gene A (CagA), vacuolating cytotoxin A (VacA), ammonia, lipopolysaccharide (endotoxin), platelet activating factors, nitric oxide and interleukin-8 8,9 .Vac A cytotoxin, which is synthesized as a 140KDa precursor and released from the bacterium as a 95KDa mature toxin 10 .Vac A cytotoxin secreted by about 50% of H. pylori isolates in western countries 11 .Infection with vacuolating cytotoxin positive strains is reported to be associated with peptic ulcer disease.They showed that strains with vacuolating cytotoxin activity were found in 16 out of 24(67%) patients with peptic ulcers but in only 16 of 53 (30%) patients without [12][13][14][15] .Infection with H. pylori strain expressing cytotoxin associated Cag A protein is more virulent and is associated with increased risk of development gastric cancer 16 .There is evidence that Cag A positive strains are more infectious [17] , achieve higher bacterial density on the gastric mucosa and cause more inflammation than Cag A negative strains.Cag A positive H. pylori strains have been shown to be associated with interleukin-8 (IL.8) induction in gastric epithelium, neutrophilic infiltration and thus be related to gastric inflammation and gastroduoderal diseases 18,19 .Expression of Cag A protein is closely associated with that of vacuolating cytotoxin 20 , although the underlying mechanism is not understood,thus Xiang et al. 21classified H. pylori strains in two groups type I and type II.These studies stated that type I strains, which are positive for both Vac A and CagA, were strongly associated with peptic ulcer diseases in the host 21,22 .The present study was conducted with the following objectives; To show the incidence of Helicobacter Pylori in patients with variable gastroduodenal endoscopic lesions.To study the frequency of virulence associated genes Cag A and Vac A in the studied patients with positive H. pylori isolates.Patients and methods A total of 176 patients 96 males and 80 females, whose ages ranged from 14 -80 years, with various dyspeptic symptoms attending endoscopy unit at Al-sadder Teaching Hospital (Basrah) during the period from October 2004 through August 2005 were underwent upper gastroduodenal endoscopic examination.Patients with recent upper gastrointestinal bleeding, on nonsteroidal anti inflammatory drugs, antibiotics or proton pump inhibitors were excluded from the study.Two antral biopsy samples were obtained from each patient one for rapid urease test and the second for bacterial culturing as described by Barn et a 23 .A third biopsy sample was obtained from (50 patients only) due to cost constraints for histologic examination.Culture colonies that exhibited characteristic morphologies were studied also biochemically by catalase and oxidase according to Finegold and Baron 24 to confirm the identity of positive H. pylori isolates.Patients from whom H. pylori were isolated and identified biochemically were studied for toxigenic strains by mannose resistant heamagglutination test (MRHA) 25 .
Bas J Surg, March, 16, 2010 ٣٣ Grown cultures were suspended in phosphate buffer saline (PBS) at pH. 7.2 26 , and tested against human erythrocyte.Blood was drawn from volunteer donors and placed into a tube containing 1.0 ml of 3.8% citric acid, in distilled water per 9.0 ml of blood.Blood was diluted 1:4 with PBS to test for mannose resistant haemagglutination.MRHA test was performed by mixing equal volume of each bacterial suspension with erythrocyte suspension, with and without (1%) D-mannose, in PBS.Glass tile with round depressions were rocked gently with swirling action at (20-22C).Mixture was subsequently incubated at (4 º C)for up to (20 min) before reading.Positive toxigenic strains, which revealed haemagglutination with erythrocyte cells, were preceded by polymerase chain reaction (PCR) technique by using primer sequences.table I 27 .

Results
Sex and age distribution of patients are illustrated in table II.Ninety-six (54%) and 80(45.5%)were males and females respectively.Forty-nine (52%) of males and 46 (57.5%) of females showed positive H. pylori isolates by culture, the differences were statistically not significant (P>0.05).

Discussion
In the present study, no statistically significant differences (P>0.05) were found in the detection of H. pylori among males (52%) and females (57.5%).These differences were also not reported in other studies 28,29 .
Regarding the age groups, the highest detection rates of bacteria were recorded in the age group more than 60 year (62.8%), while the lowest detection rates were recorded in the age group below 20 year( 28.5%)This result was nearly similar to other study 30 .The higher prevalence of the infection in elderly people is partly due to a cohort effect 31 , in addition, the low immunity in the elderly may be a cause of increased incidence in this age group.
In the present study, the percentage of positive biopsy rapid urease test was 64% (81/124) of positive endoscopic lesions ,which was similar to other several studies 30,[32][33][34] .The use of biopsy urease test in the endoscopy unit is convenient since it is easy to perform and read and sensitive enough 35 .Culture of gastric biopsies is the golden standard technique for H. pylori diagnosis, although primary isolation of H. pylori from a biopsy specimen is a difficult process, but the typical reports success rates in culturing the organisms are in the range of 70% -80% to 95% sensitivity and 100% specificity 36 In the present study, the total isolation rate of H. pylori was reaching a percent of 77% (97/124) of positive endoscopic lesions (table III).This rate is compatible with the above mentioned international results [36] There are several factors, which might affect culturing of the organism.Patchy distribution and loss of viability of the organism during transportation may be responsible for a poor negative predictive value associated with culture of H. pylori.Helicobacter pylori provokes an inflammatory response that damages the Bas J Surg, March, 16, 2010 ٣٧ gastric protective mucosa and exposes the mucosal surface to acid and pepsin 37- 39 .Some investigators have shown that this inflammatory response is associated with the organisms ability to secrete vacuolating cytotoxin or release lipopolysaccharides, which in turn induce recruitment and release of soluble mediators of inflammations including interleukin 8 28,40 .These mediators alone or in combination induce inflammatory response 41,42 44 .Potential benefits also include its high sensitivity and the potential to identify toxigenic strains on the basis of the specific genes that they possess 45 .In the present study PCR technique was used for the detection of virulence associated genes (CagA and VacA genes) in the isolates of H.pylori .The study shows that 18 of 25 isolates (72%) were positive for either CagA or VacA genes, 13(52%) were positive for both CagA and VacA genes.These results were in line with the other studies in this field 40 .Atherton et al 39 20 , although the underlying mechanism is not understood.Maeda et al 11 reported that most H. pylori strains isolated in Japan were positive for vacuolating cytotoxin and CagA protein.
Fifty-four out of sixty-eight (79%) isolates were positive for the vacuolating and CagA protein and were therefore type I strains.Weel et al 22 reported that infection with type I strains was found in 43/76 (57%) patients with peptic ulcers, but in only 28/76 (37%) patients with non-ulcer dyspepsia in the Netherlands.
In conclusion, H. pylori has proved to be one of the most genetically divers bacteria yet found.Almost any technique that looks at gene arrangements or that disrupts the chromosome, e.g.digestion by restriction enzymes, shows that strains from each individual are different.Genetic diversity in Helicobacter pylori strains may affect the function and antigenicity of virulence factors associated with bacterial infection and, ultimately, disease outcome.

Table V : PCR detection of selected genes (CagA and VacA) in patients with H. pylori isolates
Bas J Surg, March, 16, 2010 ٣٦

Table VI : Identification of CagA and VacA genes by PCR in H. pylori positive isolates from 25 patients with endoscopic lesions
46d Wong et al46had detected Vac A gene in 93% and 95.8% of H. pylori positive gastric biopsy specimen by using the PCR in