Abstract
Helicobacter pylori (H. pylori) is bacteria considered to be present in half of the population and it is a public health problem worldwide. Most patients infected with H. pylori show no clinical symptoms; nonetheless, approximately 10% to 20% of these patients will develop peptic ulcers and 1% will develop gastric cancer. The International Agency for Research on Cancer has classified H. pylori as a Group 1 carcinogen, recognized as the only bacteria capable of producing cancer. Samples of drinking water (n = 44) from aqueducts with chlorination treatment in selected areas with high prevalence of gastric cancer were analyzed in Costa Rica. Samples of drinking water from Panama (n = 44) from aqueducts supplying untreated water for human consumption in the province of Chiriqui were also analyzed. The molecular marker of H. pylori, glmM, was used, and to optimize the Real Time PCR (qPCR) technique, annealing temperature, concentration of primers and probe were standardized; also, by analyzing different standard curves, the best reaction conditions that allowed detecting and quantifying the gene were determined. The LightCycler® 480 II (LC480II) equipment from Roche Diagnostics GmbH was used, as well as the Absolute Quantification Analysis by means of the Second Derivative Maximum Method. In the case of the samples from Costa Rica, it was determined that 79.5% were positive for H. pylori; removing outlier high average, quantification of bacteria was determined in 3.6 × 103 copies/100 mL. For Panama it was determined that 86% of the samples were found positive for the presence of H. pylori; removing outlier high average quantification of bacteria was determined at 3.3 × 102 copies/100 mL. The difference in values between the aqueducts in both countries revealed an environmental distribution of the bacteria of epidemiological interest in each case.
Highlights
Shahamat et al demonstrated that gene glmM was the major target for detection of H. pylori for PCR amplification [24], and it is considered to form part of the housekeeping genes [25] [26]; for these reasons, the use of genes other than 16S is recommended for phylogenetic analysis and identification within the Helicobacter genus, for example RNAr 23S genes and glmM [23]
The number of copies of the gene in each of the dilutions used was calculated using the standard curve by plotting the logarithm of the concentration calculated by the equipment vs Crossing point (Cp) value of each standard.To determine the detection limit of the technique, the minimum number of copies/mL quantified by the equipment in Standard 6—which, theoretically, contained three copies of the gen—was analyzed
As for Costa Rica, 25% of the samples showed an average value of residual chlorine of 0.1 mg/L; the remaining 75% of the samples showed no residual chlorine, despite having gone through a chlorination process in the respective aqueducts; slight water turbidity was observed in some samples
Summary
H. pylori was discovered in 1982 by doctors Barry Marshall and Robin Warren from Perth, Australia, who observed the bacterium for the first time in stomach biopsies from a patient with active chronic gastritis. In recognition for their discovery, they were awarded the 2005 Nobel Prize in Medicine and Physiology. Since 1994 and to this date, the International Agency for Research on Cancer (IARC) of the World Health Organization has declared H. pylori as a carcinogenic in humans, classified in group I (there exists enough evidence that confirms it can cause cancer in human beings); being the only bacterium capable of causing this pathology amongst all groups of toxic substances. Other routes have been suggested for viable transmission of the bacterium, such as water and foodstuffs. Authors agree that the relative importance of these transmission routes varies among developed and developing countries [2] [3]
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