Environmental pathogens

Legionella pneumophilia + L. longbeachae

Infectious organism for legionellosis

Presentations of legionellosis

• Legionnaires disease (atypical pneumonia)

• Pontiac fever (mild URTI)

Reservoir/ prevention of legionellosis

• Potting mix, environmental amobea and freshwater protozoa

• Regular cleaning and maintenance of water storage

Mode of transmission of legionella/ prevention

• Inhalation of contaminated aerosols in watersprays or aspiration of contaminated water

• Hygiene (i.e. wearing mask and gloves while potting)

People at risk of legionella

• AIDS/ immunocompromised

• Elderly

• Smokers and alcohol consumption

Diagnosis of legionella

• Culture of lower respiratory secretions on selective media/ PCR

• Legionella urinary antigen test

Giardia duodenalis/ G. lamblia

Infectious organism for giardia

Giardia life cycle

1. Cysts of giardia ingested from contaminsed water/ food

2. Excystation follows exposure to stomachacid and intestinal proteases, releasing trophozoite which multiply by binary fission and reside adherent to upper SI

Signs of giardiasis

• Diarrhoea

• Gas

• Steatorrhea

• Stomach/ abdominal cramps

• Nausea and vomiting

• Dehydration

Mode of transmission of giardia + cyrptosporidium

Ingestion of food/ water w faecal contamination from animals, humans, water

Treatment of giardiasis

Metronidazole + tinidazole

Pathogenesis of cryptosporidium infection

Form cysts which damage SI epithelium, before being excreted through faeces. Causes severe/ potentially fatal infection

Signs of cryptosporidium

• Watery diarrhoea

• Fever

• Stomach/ abdominal cramps

• Nausea and vomiting

• Weight loss

Treatment of cryptosporidium

Nitazoxanide (does not work in HIV/ immunocompromised patients)