Microbiology
Principles
Question 12 of 180
Which of the following is the most frequent source of healthcare associated bacteraemia:
Answer:
Intravenous access is the most frequent source of healthcare associated bacteraemia. The risk of infection from any intravenous device increases with the length of time it remains in situ. It provides a route for invasion by organisms such as Staphylococcus aureus and Staphylococcus epidermidis.Hospital Acquired Infection
Microbiology / Principles / Controlling Infection
Last Updated: 21st April 2019
A hospital acquired infection (HAI) is defined as an infection which was not present or incubating at the time of hospital admission. Infection is a major cause of mortality and morbidity in patients admitted to hospital.
Spread of Infection
Spread may occur via:
- food supply (issues of hygiene standards, temperature of food, transport to ward)
- air supply (via theatre air supply and air conditioning systems)
- fomites (any inanimate object that may act as a vehicle for transmission e.g. MRSA on a stethoscope, Pseudomonas spp. on vases)
- water supply (Legionella pneumophila may colonise the system in redundant areas of lukewarm pipework and be transmitted to the air conditioning system - to reduce this risk hot water supplies should be maintained at temperatures above 45°C and cold water supplies below 20°C)
Risk Factors for Infection
Patient centred risk factors include:
- Underlying illness or treatment e.g. immunosuppressive drugs
- Antibiotic therapy
- Patients tend to be older and less mobile
- Patients tend to be kept in close contact with other patients/staff
- Patients have less access to washing facilities
- Invasive devices e.g. indwelling urinary catheters provide a route for ascending infections into the bladder due to urinary stasis with secondary bacterial colonisation
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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 |
