Microbiology
Pathogens
Regarding Pseudomonas aeruginosa which of the following statements is CORRECT:
Answer:
Moist places such as sink-traps, drains and flower vases can harbour P. aeruginosa and it has a remarkable ability to withstand disinfectant. It may be spread via direct contact or indirect contact on the hands of healthcare workers or by contaminated equipment, via ingestion of contaminated food or via inhalation of aerosols.Pseudomonas Aeruginosa
Microbiology / Pathogens / Pseudomonas
Last Updated: 21st April 2019
| Microorganism | Pseudomonas Aeruginosa |
|---|---|
| Gram stain | Gram negative |
| Shape | Rod |
| Oxygen requirements | Obligate aerobe |
| Oxidase | Positive |
| Additional features | Non-fermenting, often multidrug resistant |
| Reservoir | Soil, water, intestinal flora, fomites |
| Transmission | Direct and indirect contact spread |
| Disease | Nosocomial infection (mainly pneumonia, UTI and wound infection), colonisation of cystic fibrosis and burns patients, sepsis, 'hot tub rash', otitis externa, ecthyma gangrenosum, infective endocarditis, corneal infections |
| Risk factors | Cystic fibrosis, burns, IV drug users, diabetes mellitus, neutropenia, immunosuppression, indwelling urinary catheters |
Most pseudomonas spp. are aerobic, motile, Gram-negative bacilli that cause opportunistic infections, particularly in a healthcare environment in patients with lowered host defences (especially in intensive care units and in neutropenic patients).
P. aeruginosa is the primary human pathogen. P. aeruginosa produces damaging cytotoxins and proteases and has other adaptive mechanisms that increase its virulence.
Transmission
Moist places such as sink-traps, drains and flower vases can harbour P. aeruginosa and it has a remarkable ability to withstand disinfectant. It may be spread via direct contact or indirect contact on the hands of healthcare workers or by contaminated equipment, via ingestion of contaminated food or via inhalation of aerosols.
Clinical Disease
Pseudomonas aeruginosa is implicated in:
- Hospital-acquired septicaemia (with high mortality, neutropenic patients at particular risk)
- Catheter-related urinary tract infection
- Respiratory infection
- Chronic pulmonary infection in cystic fibrosis
- Ventilator-associated pneumonia
- Hospital acquired pneumonia
- Skin and soft tissue infection
- Colonisation and chronic infection of venous ulcers
- Colonisation of burns and secondary septicaemia
- Surgical site infection
- Hot tub rash (acute self-limiting folliculitis)
- Ecthyma gangrenosum (a destructive skin complication of septicaemia)
- Osteomyelitis
- Septic arthritis
- Ocular infection
- Rapidly progressive corneal infection (in contact lens wearers)
- Ear infection
- Otitis externa
- Malignant otitis externa (in diabetics or patients with HIV)
- Infective endocarditis (in IV drug users)
- Meningitis
Diagnosis
Diagnosis is by culture on selective media.
Treatment and Prevention
Organisms are often multidrug resistant, therefore treatment is guided by sensitivities.
Prevention of infection can be achieved by maintaining good hygiene and handwashing practice, minimising unnecessary antibiotic use, minimising the use of medical devices and using sterile medicated solutions.
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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 |
