24. Gram +ve Aerobic Rods & Mycobacteria Flashcards
Name the Aerobic gram +ve rods.
- Bacillus
- Lactobacillus
- Corynebacterium diphtheria
- Listeria monocytogenes
- Norcadia
- Actinomyces
Most species of Corynebacterium is commensal on skin, which is species is pathological?
Corynebacterium diphtheria.
- produces diphteria toxin that can cause 1. Myocarditis 2. Nerve damage
What are the symptoms of coryndebacterium diphtheria?
- Bull neck (lymphadenopathy)
- Sore throat/ pseudomembrane (basically leathery white layer at the back of the throat w lots of pus)
- Cutaneous lesions
Toxin mediated effects
1. Myocarditis
2. Nerve damage (neuropathy)
How is C. Diphtheria managed?
- Toxoid vaccine given in childhood.
- Can be treated w ABs : penicillin & erythromycin
- PEP: post exposure antibiotic prophylaxis
What does the c. Diphtheriae vaccine do?
- doesnt prevent infection, only prevents colonisation
- most sgporeans are protected cuz vaccine is given at birth, more worried in foreign workers who havent been vacciated
How is Listeria transmitted?
- food borne
- special, can thrive even at cold temps, unlike many other bacteria
Listeria is more common in the..
Immunocompromised or extremes of ages (very young or very old)
How does Listeria manifest?
- usually gastroenteritis (foodborne outbreaks)
- invasive diseases 1. Bacteremia 2. Meningitis/Focal CNS lesions
- is why pregnant women are advised against eating cheese. Can cause miscarriage
(Bacteria prolly invades through GI)
How is Listeria managed?
Ampicillin (+ gentamicin for synergistic effect)
What is Actinomyces/ Actinomycosis characterised by?
- pus
- sulphur granules
- filamentous gram +ve branching rods (when u look closer w microscope)
[T/F] actinomyces is usually commensal
true
- colonises almost every part of the body
What are the 3 most common actinomycosis sites?
- Orocervicofacial (50%)
- Thoracic (15-20%)
- Abdominopelvic (20%)
What is empyema necessitans?
Empyema necessitans is a rare complication of pleural space infections and occurs when the infected fluid dissects spontaneously into the chest wall from the pleural space
- very few pathogens cross planes
- actinomyces is one of them, invades onwards and doesnt confine to one organ
treatment of actinomycosis
- natural penicillin usually works
- 2 phases of tx 1. intensive 2. consolidative
- takes rlly long to treat
when culturing nocardia, what is significant about it
- most bacteria lies flat on agar plate
- but nocardia grows upwards like a fungus
[T/F] Nocardia usually occurs in immunosuppressed
true
- solid organ tranplant recipients
- systemic immunosuppression
- systemic corticosteroids
nocardia often affects..
pulmonary/skin/soft tissue infection, brain abscess
- one of the bacteria that lead to lung brain syndrome
what are the bacteria that lead to lung brain syndrome
- nocardia
- aspergillus
- cryptococcus
bacillus looks like a fungus on culture dish but is a..
(fat) gram +ve rod
we usually consider bacillus a ____________ .
contaminant
- majority is environmental
anthrax is due to..
bacillus anthracis
- been tested in MCQ exams as the african drum/hat brought back and caused disease how come? its cuz theres anthrax spores on the animal hide
what is the most common infection caused by anthrax? what are other manifestations
pneumonia
- happens when spores are inhaled
could also be 1. cutaneous via direct contact 2. gastrointestinal when ingested
what are the 2 pathogenic mycobacteria species (that we gotta know)
M. tuberculosis complex (causes tuberculosis)
M. leprae (causes leprosy)
mycobacteria can be cultured in?
lowenstein-jensen medium (2-6 weeks)
what are the characteristics of mycobacteria?
- rod shaped bacteria
- thick mycolic cell wall (mycolic acids in cell wall) => acid fast bacilli (AFB), stains red
key drugs/tx against mycobacterium tuberculosis?
- isoniazid and rifampicin
- minimum 6 months
- required by law to notify authorities, if not can be detained by infectious disease act
- to be treated in -ve pressure room
symptoms of tuberculosis
cough blood, night sweats
