Microbiology
Pathogens
A patient presents to ED recurrently with symptoms of dyspepsia. Your consultant asks you to find out if the patient has previously been tested for Helicobacter pylori. Diagnosis of H. pylori infection can be made with which of the following tests:
Answer:
Diagnosis of Helicobacter pylori can be made in a number of ways, initially through the urea breath test, stool antigen test or serology or through gastric biopsy at endoscopy.Helicobacter Pylori
Microbiology / Pathogens / Gram-negative Gastrointestinal Disease
Last Updated: 25th July 2020
| Microorganism | Helicobacter Pylori |
|---|---|
| Gram stain | Gram negative |
| Shape | Rod (spiral flagellate) |
| Oxygen requirements | Microaerophilic |
| Oxidase | Positive |
| Reservoir | Gastric mucosa |
| Diseases | Peptic ulcer disease, gastric malignancy |
Pathogenesis
Helicobacter pylori is a motile Gram-negative spiral bacillus that lives only on gastric mucosa, and may be transmitted via the faecal-oral route.
Helicobacter pylori infection causes inflammation of the mucosal lining of the stomach, depleting the layer of protective alkaline mucus and altering gastric acidity. H. pylori expresses urease, which raises the pH in the surrounding area and protects the bacterium from the effects of gastric acid.
Clinical Disease
H. pylori infection is often asymptomatic, but may cause dyspepsia or gastritis and predisposes to peptic ulceration and gastric malignancy.
Diagnosis
Investigations for diagnosis:
- Urea breath test (PPI must be stopped 14 days prior to testing and withhold testing for 28 days after treatment with an antibiotic)
- Stool antigen test (PPI must be stopped 14 days prior to testing and withhold testing for 28 days after treatment with an antibiotic)
- Serology for IgG antibodies (unhelpful where patients have previously been treated for H. pylori infection)
- Gastric biopsy
Treatment
Treatment is with a one week triple-therapy twice-daily dosing regimen that comprises a proton pump inhibitor (e.g. lansoprazole 30 mg, omeprazole 20 mg or pantoprazole 40 mg), amoxicillin (1 g) and either clarithromycin (500 mg) or metronidazole (500 mg).
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
