Helicobacter
Helicobacter is a genus of bacteria known to inhabit the gastric mucosa of various vertebrates, including humans. The most studied species, Helicobacter pylori, is linked to several significant health issues such as chronic gastritis, peptic ulcers, and stomach cancer. Helicobacter pylori, identified in 1983, is a gram-negative, microaerophilic bacterium that thrives in low-oxygen environments. It can take on various shapes and is characterized by sheathed flagella, which aid in its mobility.
Infections are commonly transmitted through direct contact, often via saliva or fecal matter, especially in crowded living conditions or where sanitation is poor. While approximately half of the global population may be infected with H. pylori, many individuals remain asymptomatic. However, those affected can experience painful symptoms and complications if left untreated. Diagnosis can be achieved through several methods, including breath tests and endoscopy. Treatment generally involves a combination of antibiotics and medications to reduce stomach acid, though some strains have developed resistance to common drugs. Understanding Helicobacter's role in digestive health is crucial for effective prevention and treatment strategies.
Helicobacter
- TRANSMISSION ROUTE: Direct contact, ingestion
Definition
Species of the bacterial genus Helicobacter cause a number of gastric and digestive accessory organ diseases in vertebrates. In humans, these diseases include chronic gastritis, peptic ulcer disease, and stomach cancer.
Natural Habitat and Features
Helicobacter was defined as a genus in 1989, and many of its species have since been discovered. Helicobacter spp. inhabit the gastric mucosa of many vertebrate animals, primarily birds and mammals. H. pylori was described by Robin Warren and Barry Marshall in 1983. It is the species most often found in humans and has been extensively studied; most other Helicobacter spp. are like it in characteristics and growth patterns.
H. pylori is a gram-negative, S-shaped, or curved-rod bacterium. The bacterium is a microaerophile, requiring small amounts of oxygen and growing best in the presence of 5 to 10 percent oxygen and 5 to 10 percent carbon dioxide. Specimens range from 0.5 to 0.9 micrometers (µm) wide and 2 to 4 µm long. Occasionally, V-shaped, U-shaped, straight, or spherical forms of H. pylori are found either in culture or within the human host.
Members of this genus are characterized by possessing sheathed flagella (usually seven in H. pylori), which have a covering continuous with the outer membranes of the body wall, an external glycocalyx, the presence of menaquinone-6, and G+C content of chromosomal DNA (deoxyribonucleic acid) of 35 to 40 mol percent. Cultured colonies of H. pylori grow within about three to five days and are convex, circular, and translucent in appearance.
In addition to pylori, human infections have been caused by canis, cinaedi, fennelliae, hepaticus, and heilmannii. Some researchers have suggested a link between hepaticus and gallbladder cancer in humans; this bacterium is primarily found in rodents. Heilmannii, usually restricted to cats and dogs, may infect humans and cause chronic gastritis.
Pathogenicity and Clinical Significance
H. pylori is the causative factor of stomach ulcers and of many cases of chronic gastritis and stomach cancer, particularly gastric mucosa-associated lymphoid tissue (MALT) lymphoma (MALToma). The bacterium is also associated with cases of iron deficiency anemia.
Approximately 50 percent of the world’s population is infected with H. pylori. Most people have no ill effects, but for those who do, the outcome without treatment can be painful, debilitating, and even fatal. About 10 percent of individuals with H. pylori infection will develop an ulcer. Less will develop stomach cancer.
Research indicates that most infections are acquired during childhood by person-to-person contact, primarily through direct contact with the saliva or fecal material of an infected person, often a family member. There is some evidence that H. pylori can also be transmitted through untreated water. Living in crowded conditions, living in areas where there is no reliable source of hot water, and living with someone who is already infected with H. pylori are all important risk factors influencing the spread of this bacterial disease.
Symptoms of an H. pylori infection include an ache or burning sensation in the stomach or abdomen, nausea, vomiting, frequent burping, a bloated feeling, and unexplained weight loss. Physicians test for the presence of H. pylori by blood tests, urea breath tests, stool sample tests, and endoscopy. The blood test for this bacterium has some inaccuracy because if a person has had H. pylori in the past and has been treated for it, antibodies for the bacterium may remain in the blood. The urea breath test is considered to be a more accurate indicator of an infection. It is based upon the ability of the bacteria to break down urea into carbon dioxide. The patient swallows a capsule containing a tiny amount of radioactive urea, and ten to twenty minutes later, a breath sample is collected and analyzed. If radioactive carbon dioxide is present, this indicates an active H. pylori infection.
Endoscopy can also be used to check for ulcers and stomach cancer, as gastric tissue can be removed for biopsy during the procedure.
Drug Susceptibility
A combination of antibiotic drugs and either proton pump inhibitors (PPIs) or histamine (H-2) blockers generally provide an effective treatment for H. pylori infections. Usually, amoxicillin and clarithromycin are prescribed together, or a combination of metronidazole, tetracycline, and bismuth subsalicylate may be given to the patient. PPIs, including omeprazole, lansoprazole, pantoprazole, rabeprazole, or esomeprazole, are prescribed to control the production of stomach acid. Histamine blockers such as ranitidine, famotidine, cimetidine, and nizatidine may also be effective in suppressing acid production.
Antibiotic treatment should be closely supervised because some strains of H. pylori have become resistant to metronidazole and clarithromycin. Vonoprazan-based regimens (a potassium-competitive acid blocker) are used in areas with high clarithromycin resistance. Treatment protocols usually last two weeks; however, longer-term treatment, especially acid-reduction medicines, may be needed for some patients.
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