Microbiology
Pathogens
Regarding dermatophytes, which of the following statement is CORRECT:
Answer:
Diagnosis is made from microscopy and culture of skin scrapings, hair samples or nail clippings depending on the site of infection. The lesions of ringworm typically have a dark outer ring with a pale centre. Tinea capitis is ringworm affecting the head and scalp. Spread is via direct skin contact. Treatment is usually topical, oral antifungals are reserved for refractory infection.Dermatophytes
Microbiology / Pathogens / Yeasts and Fungi
Last Updated: 21st April 2019
Three genera of filamentous fungi are implicated in dermatophytosis: Epidermophyton spp., Microsporum spp. and Trichophyton spp..
Transmission
Dermatophyte infection is spread via close personal contact.
Clinical Features
It may occur on the head and scalp (tinea capitis), body (tinea corporis) and feet (tinea pedis).
Ringworm typically presents as itchy, red, scaly, patch-like lesions that spread outwards, leaving a pale centre.
Chronic nail infection produces discolouration and nail thickening.
Scalp infection is often associated with hair loss and scarring.
Diagnosis
Diagnosis is often clinical and does not require laboratory confirmation. The scalp may demonstrate a characteristic fluorescence when examined under Wood's light dependent on the infecting fungal species.
If laboratory confirmation is required (e.g. if diagnosis is unclear, if infection has not responded to treatment or if oral antifungals are being considered) skin scrapings, nail clippings and hair samples should be collected as appropriate. Diagnosis may be made by direct microscope examination of wet mounts or by culture.
Treatment
Treatment is usually topical with imidazole antifungals (e.g. miconazole, clotrimazole or ketoconazole) but if severe or refractory may require oral terbinafine for several weeks.
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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 |
