Which bacteria cause most frequently typhoid fever and enteric fever, respectively?
Salmonella typhi (typhoid)
Salmonella paratyphi A, B, C (enteric fever)
When typhoid fever is suspected, what kinds of clinical samples should be used to isolate the causative agent in the first 2 weeks of the disease?
Blood, (bone marrow)
What is the route of infection in Salmonella gastroenteritis?
Ingestion of contaminated food (such as eggs, cream, mayonnaise, creamed foods, etc.)containing a sufficient number of Salmonella.
Which antibacterial drugs should be administered in gastroenteritis caused by Salmonella?
Antibiotics are not usually necessary unless the infection is generalised. In case of extraintestinal infection (very young, very old or immunosuppressed patients):ampicillin, gentamicin, trimethoprim/sulfamethoxazole, or ciprofloxacin.
List the 4 Shigella species causing human disease!
Shigella dysenteriae, S. flexneri, S. boydii, S. sonnei
Mention 2 bacterial species belonging to different genera that cause bacillary dysentery
Mention 2 bacteria causing intestinal infections which have animal reservoirs
Salmonella (not Typhi and Paratyphi!), Campylobacter jejuni, Yersinia enterocolitica, Listeria monocytogenes, E. coli O157
What are the modes of transmission for the 2 different epidemiologic forms of plague?
- Bubonic plague is transmitted by the bite of infected rat fleas from rats to humans.
- Primary pneumonic plague spreads directly from human to human via respiratory droplets.
What are the possible portals of entry of Francisella tularensis? Specify at least 4!
tick bite, mucous membranes, skin abrasions, resp. tract, gastroint. tract
How do humans acquire brucellosis? Where do the bacteria replicate in the human body?
Via contaminated milk products or through skin abrasions (contact with animals).Organisms spread to the mononuclear phagocytes of the reticuloendothelial system(lymph nodes, liver, spleen, bone marrow).
What are the reservoirs of the different Brucella species, respectively?
B. abortus: cattle
B. melitensis: goat, sheep
B. suis: swine
What is the mechanism of action of cholera toxin?
Cholera toxin activates the adenylate cyclase enzyme in cells of the intestinal mucosa leading to increased levels of intracellular cAMP, and the secretion of large amount of water, Na+, K+, Cl-, and HCO3- into the lumen of the small intestine.
What is the principle of the treatment for cholera?
Rapid intravenous or oral replacement of the lost fluid and ions. (Administration of isotonic maintenance solution should continue until the diarrhea ceases.) In severe cases:administration of tetracycline (in addition to rehydration).
Mention 4 diseases caused by Haemophilus influenzae!
epiglottitis (obstructive laryngitis)
otitis media and sinusitis
Which disease is caused by Haemophilus ducreyi?
Chancroid (soft chancre or ulcus molle)
What can serve as source of infections caused by Pseudomonas aeruginosa?
Pseudomonas species are normally present in the environment and can be isolated from the skin, throat, and stool of some healthy persons. They often colonize hospital food,sinks, taps, mops, and respiratory equipment.
Mention 4 diseases that are frequently caused by Pseudomonas aeruginosa!
urinary tract infections
wound infections (burns)
pneumonia, sepsis (immunosupression)
Mention at least 3 drugs which may be effective to treat infections caused by Pseudomonas aeruginosa!
certain penicillins: piperacillin/tazobactam combination
a 3rd generation cephalosporin: ceftazidim
a 4th generation cephalosporin: cefepime
certain aminoglycosides: gentamycin, tobramycin, amikacin
carbapenems: imipenem, meropenem
Which 2 diseases are caused by Legionella pneumophila?
Which is the most important gas gangrene Clostridium? What is its main virulence factor?
Mention 3 Clostridium species causing gas gangrene! How are they acquired?
Clostridium perfringens, C. novyi, C. septicum, C. histolyticum, C. tertium, C.bifermentans, C. sporogenes
The site of infection is usually a wound that comes into contact with Clostridium spores that germinate in an anaerobic environment.
How can be tetanus prevented in patients who have wounds possibly contaminated with C.tetani spores?
Wound should be cleaned and debrided; tetanus toxoid booster injection given;tetanus immunoglobulin (TETIG) in previously unvaccinated patients and in case of heavy contamination of wound; penicillin may be added prophylactically
What are the main symptoms of tetanus infection? Specify at least 3!
Spastic paralysis: muscle spasms; lockjaw(trismus), rhisus sardonicus (grimace of theface), opisthotonus (spasm of the back); respiratory paralysis
What is the mechanism of action of the botulinus toxin?
Blocks release of acetylcholine in peripheral nerve synapses;
What are the main symptoms of botulism? Specify at least 3!
Treatment: respiratory support + trivalent antitoxin
Explain whether or not antibiotic treatment is useful in botulism!
Not, because antibiotics are not effective against preformed toxins.
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?
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 diphtheria exist? Which immune effector mechanism is involved?
Antitoxic antibodies, long lasting immunity
Which assays should be done in the lab in order to prove diphtheria?
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 production must be demonstrated by agar precipitation ( ELEK-test)
What feature of Mycobacteria 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 Mycobacterium species!
M. kansasii, M. marinum, M. avium-intracellulare complex, M. fortuitum-chelonei complex
How can one demonstrate the presence of Mycobacterium tuberculosis in clinical samples?
Acid-fast staining (Ziehl-Neelsen)
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 Mycobacterium tuberculosis?
Mention 3 antituberculotic drugs that are of first choice against Mycobacterium tuberculosis!
What is the causative agent of febris undulans (undulant fever)?
What is the precise definition of bacterial food poisoning?
Acute disease, usually with vomiting and diarrhea, caused by preformed toxins produced by bacteria contaminating the food. The period between consumption of food and the appearance of symptoms is short (< 4-6 hours).