Microbiology
Principles
Question 1 of 180
Which of the following microbes is sexually transmitted:
Answer:
Neisseria gonorrhoeae is spread via sexual transmission. Neisseria meningitidis is spread via the respiratory droplet route. Staphylococcus epidermidis is primarily spread via direct skin contact. Streptococcus pyogenes is spread via the respiratory droplet route or via direct skin contact. Plasmodium falciparum is spread via a vector.Sources and Spread of Infection
Microbiology / Principles / Controlling Infection
Last Updated: 21st April 2019
Sources of Infection
Infection is caused either by organisms from the host's normal flora (endogenous infection) or by organisms transmitted from another source (exogenous infection).
Endogenous infection will only occur if circumstances permit. For example:
- Inhalation of stomach contents may cause aspiration pneumonia.
- Staphylococcus aureus normally found in the nose may cause infection if inoculated into a surgical wound or cannulation site.
- N.B. Neutropenic patients are especially prone to infection from conditional pathogens.
Examples of exogenous infections include:
- Salmonella enterica spread via ingested poultry.
- Legionella pneumophila spread via poorly maintained air-conditioning cooling towers.
Spread of Infection
Examples of routes of transmission of infection include:
| Route of Transmission | Examples |
|---|---|
| Airborne | Mycoplasma tuberculosis, Measles virus |
| Respiratory droplet | Neisseria meningitidis, Influenza virus |
| Faecal-oral | Salmonella enterica, Campylobacter jejuni |
| Sexual | Neisseria gonorrhoea, HIV |
| Vector-borne | Plasmodium falciparum |
| Transcutaneous (through intact skin) | Leptospira spp., Treponema pallidum |
| Percutaneous (through breached skin) | Staphylococcus epidermidis |
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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 |
