Clinical Microbiology — SCT II [Vol. 4] Flashcards
Mention at least 2 drugs that can be used to treat diseases caused by Clostridioides difficile
- Vancomycin
- Metronidazole
- Fidaxomicin
What diseases may be associated with Helicobacter pylori? Specify at least 3
- Gastritis
- Peptic and duodenal ulcers
- Gastric carcinoma
- MALT lymphoma
What is the most important virulence factor of Corynebacterium diphtheriae?
Diphtheria toxin
What is the mechanism of action of the diphtheria toxin?
Inhibits protein synthesis. Inhibits peptide elongation in eukaryotic ribosomes by ADP-ribosylation of EF-2 (elongation factor-2)
How long does immunity against diptheria last? Which immune effector mechanism is involved?
Long lasting immunity; antitoxic antibodies
Which assays must be performed in the laboratory diagnosis of diptheria?
Smears of the throat swab should be stained with methylene blue or Neisser stain.”
Bacteria are cultured on Löffler’s or tellurite (Clauberg) medium; toxin productionmust be demonstrated by agar precipitation (ELEK-test)
What feature of Myobacteria make them acid fast?
The cell envelope contains a high amount (60-70%) of complex lipids: mycolic acid, cord factor
Once the cells are stained (by carbol-fuchsin) they resist decolorisation by acid-ethanol
Mention 2 atypical Myobacterium species
- M. kansaii
- M. marinum
- M. avium-intracellular complex
- M. fortuitum-chelonae complex
How can one demonstrate the presence of Myobacterium tuberculosis in clinical samples?
- Acid-fast staining (Ziehl-Neelsan)
- Culture on selective media (Löwenstein-Jensen agar, liquid BACTEC medium)
- PCR amplification of bacterial DNA
Why is multi-drug therapy used for tuberculosis?
To prevent the overgrowth of drug-resistant mutants during the long treatment period (if bacteria resistant to one drug emerge, they are most probably inhibited by the other drugs)
What is the main immune defense mechanism against Myobacterium tuberculosis?
Activated macrophages
Mention 3 antituberculotic drugs that are of first choice against Mycobacterium tuberculosis?
- Isoniazid (INH)
- Pyrazinamid
- Rifampin
- Ethambutol
What disease is caused by Mycobacterium avium-intracellulare? What patients are characteristically susceptible to infection?
It causes tuberculoss, especially in immunosuppressed patients (e.g. AIDS)
What is the reservoir of Mycobacterium tuberculosis?
Human
What is the reservoir of atypical Mycobacteria?
Environment (soil, water)
What are the 2 main forms of leprosy?
Tuberculoid (paucibacillary) or lepromatous (multibacillary) form
Mention 3 Gram-negative bacteria belonging to different genera causing zoonosis
- Brucella
- Francisella tularensis
- Yersinia pestis
- Pasteurella
Mention 2 Gram-positive bacteria belonging to different genera causing zoonosis
- Listeria monocytogenes
- Baillus anthracis
- Erysopelothrix rhusiopathiae
Mention 3 bacterial species belonging to different genera that are frequent causes of urinary tract infections
- E. coli
- Klebsiella
- Proteus
- Pseudomonas aeruginosa
- Enterococcus faecalis
Mention one aerobic and one anaerobic bacterium of the normal flora of the skin
Aerobic: Staphylococcus epidermidis
Anaerobic: Cutibacterium(Propionibacterium) acnes
Give two genera of each category of bacteria
Gram positive aerobic: Staphylococcus, Streptococcus, Bacillus, Corynebacterium
Gram positive anaerobic: Clostridium, Actinomyces, Propionibacterium
Give two genera for each category of bacteria
Gram negative aerobic: *Virbrio, Neisseria, Haemophilus
Gram negative anaerobic: *Bacteroides, Prevotella, Porphyromonas, Veillonella
Give 2 genera for each category of bacteria
Gram positive coccus: Staphylococcus, Streptococcus
Gram negative coccus: Neisseria, Veillonella
Gram positive rod: Clostridium, Bacillus
Give 2 genera of each category of bacteria
Gram negative rod: E. coli, Salmonella, Shigella
Spirochetes: Treponema, Borrelia, Leptospira
Describe the color and the shape of Clostridia in a Gram stained smear of gas gangrene exudate
Gram positive (dark blue) rod
(It usually does not form spores in vivo)
Mention 2 antibiotics which can be used in the empirical treatment against Gram negative obligate anaerobic bacteria
- Metronidazol
- Amoxicillin + Clavulanic acid
- Imipenem
Which 3 bacterial species are the most important causative agents of neonatal (<1 month of age) meningitis?
- Streptococcus agalactiae
- E. coli
- Listeria monocytogenes
Which 3 bacterial species are the most important causative agents of meningitis among babies (>1 month of age) and children?
- Neisseria meningitidis
- Haemophilus influenzae
- Streptococcus pneumoniae
What is the empirical antibiotic therapy of bacterial meningitis?
Ceftriaxone / Cefotaxime
What is the causative agent of febris undulans (undulant fever)?
Brucellae
