Thread by @MayoClinicINFD

Weekend Digest

Name the pathogen and its treatment.

Clues:
1. Grows within protozoa
2. Decorative fountains
3. Hotel stay during travel
4. Cough + diarrhea
5. Antigen test

2/
#Legionella species

Aerobic “intracellular” GNB
>60 species

L. #pneumophila serogroup 1 - most common cause of human illness (water exposure)

L. #longbeachae (ANZ / soil, potting mix and compost exposure)

3/
#Legionella #pneumophila

Lakes. Streams. Reservoirs.

In water:
1. Planktonic
2. Biofilms
3. Intracellular in protozoa / free-living amoeba (protects bacteria from disinfection)

4/
#Legionella exposures
1. Hotels
2. Hospitals
3. LTC facilities
4. Cruise ships
5. Apartment bldg

Check “water systems, AC units, cooling towers, water installations, hot tubs, drinking fountains, showers, aquariums, birthing pools”

#Longbeachae: soil, compost, potting mix

5/
#Legionella

Inhalation of aerosols
Infective dose: >1000 organisms

#Legionnaires disease: cough + GI s/s + myalgia; low Na+
1. CAP
2. Nosocomial (check water systems in hospitals / LTC facilities)

#Pontiac Fever / self-limited febrile illness
- Endotoxin-mediated illness

6/
#Legionella

Risk Groups
1. Older age
2. ICH / AIDS / Heme CA / SOT / TNF inhibitors / DM
3. Smoking (past / current)
4. Alcohol use
5. Chronic lung, heart, kidney disease

7/
Diagnostics

Urinary antigen test detects only
#Legionella #pneumophila serogroup 1

Antigen test does not detect the other species / serogroups
- Culture detects all (BYCE agar)
- PCR detects all

cdc.gov/legionella/cli…

8/
#Legionella Rx

FQ (Levo)
Macrolide (Azithromycin)

Tetracycline (note: L longbeachae R)

NOTE:
#Pontiac Fever: self limited illness. Toxin-mediated. No antibiotics needed!

9/
#Legionellosis is mostly sporadic
Person to person spread RARE

#Outbreaks may occur. If suspected, check for common source - contaminated water systems or soil.

ncbi.nlm.nih.gov/pmc/articles/P…