This site is 100% ad supported. Please add an exception to adblock for this site.

3rd year Microbiology II SCT


undefined, object
copy deck
5 diseases by Staph Aureus ?
Impetigo, Furunculus, Pneumonia, Osteomyelitis, Food poisoning
2 toxin mediated Staphyloccal diseases
Toxic Shock syndrome (TSS), Scalded Skin Syndrome (SSS)
3 toxic products of Staph Aureus
TSST, Enterotoxin, Leukocidin
Most viruent species of Staphylococcus
Enzymatic virulence factor -exclusive- for Staph Aureus
How can we identify the source of infection in a staphylococcal food poisoning?
Phage Typing
Which antibacterial drug is the first choice in serious infections caused by methycillin
resistant Staphylococcus aureus (MRSA) strains?
In which disease is Staphylococcus saprophyticus considered an obligate pathogen?
Cystitis in young women
Which cell constituents determine the group-specific, and the type specific antigens of
Streptococcus pyogenes, respectively?
Group specific : C-Polysaccharide
Type specfici : M protein
Mention 3 enzymes produced by Streptococcus pyogenes that enhance the spread of
the bacterial infection in the body!
Streptokinase (fibrinolysin), hyaluronidase, streptodornase (DNAse)
List 3 diseases caused by Streptococcus pyogenes in the skin or in subcutaneous
Impetigo(Pyoderma), Cellulitis, Fasciitis
Mention a toxin-mediated streptococcal disease, specify the name of the toxin and its
mechanism of action!
Scarlet fever - erythrogenic toxin – superantigen causing capillary destruction
2 Post-streptococcal diseases
Golmerulonephritis, Rheumatic fever
Which product of Streptococcus pyogenes has a major pathogenic role in
poststreptococcal diseases?
M Protein : May induce hyper--sensitivity reaction
How long does immunity against scarlet fever exist? Which immune effector
mechanism is involved?
Life-long immunity. Antitoxic antibodies are involved.
What is the drug of first choice in Streptococcus pyogenes infection?
What is the patomechanism of post-streptococcal rheumatic fever?
Type II Hyper-sensitivity (Cytotoxic Antibodies)
What is the patomechanism of post-streptococcal glomerulonephritis?
Type III Hyper-sensitivity (Immune complexes)
Which Streptococcus species plays major role in the meningitis of newborn babies?
Group B Strep (S.Agalactiae
What is the major causative agent for subacute bacterial endocarditis?
Streptococcus Viridans
What are the characteristics of Enterococci that can be used in their identification?
D group polysaccharide antigen; tolerance to bile and hydrolysis of esculin (BEA
medium: bile esculin agar); growth in the presence of 6,5 % NaCl
What are the specific morphologic features of Streptococcus pneumoniae
Gram positive diplococcus, lancet shape, capsule
3 diseases that can be caused by Streptococcus pneumoniae
Pneumonia, meningitis, sinusitis
What fast diagnostic procedure can be used in acute Neisseria gonorrhoeae infection?
Demonstration of bacteria (intracellular in PMNs) from urethral discharge by Gram
or methylene blue stain
What kind of immunity develops after Neisseria gonorrhoeae infection?
Partial immunity of short duration, no protection from reinfection
Most important manifestations of disseminated gonorrhoeal infections
Arthritis, Skin erutption, Meningitis, Endocarditis
major complication of Neisseria gonorrhoeae infection in newborns? How
can it be prevented?
Blenorrhoea (ophtalmia) neonatorum, silver acetate eye drops or erythromycin
4 major virulence factors of Neisseria gonorrhoeae?
pilus, outer membrane proteins, LOS (lipooligosaccharide), IgA protease
3 major virulence factors of Neisseria meningitidis?
polysaccharide capsule, LPS, IgA protease
What is the site of entry Neisseria meningitidis infection? What diseases are caused by
this bacterium?
The site of entry is the nasopharynx. Diseases: Meningococcemia, Acute bacterial meningitis
What kinds of prophylactic and therapeutic measurements are available against
Neisseria meningitidis infections?
Chemoprophylaxis: rifampin or ciprofloxacin.
Vaccination: capsular polysaccharide (types A, C, Y and W135). No vaccine against
type B!
Which rapid diagnostic methods can be used in the presumptive diagnosis of purulent
bacterial meningitis?
Gram or methylene blue stain of CSF sediment,
Demonstration of bacterial capsular antigens by latex agglutination (from CSF)
3 pathogenic bacteria that account for the majority of purulent meningitis
Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae
Which are the portals of entry of Bacillus anthracis?
Skin, lung, gastrointestinal tract
3 important bacteria involved in nosocomial (hospital-acquired) infections!
Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aer
4 E. coli pathogenetic groups involved in enteric diseases!
Enteropathogenic E. coli (EPEC)
Enterotoxic E. coli (ETEC)
Enteroinvasive E. coli (EIEC)
Enterohemorrhagic E. coli (EHEC)
most important extraintestinal infections caused by E. coli?
urinary tract infections, neonatal meningitis, nosocomial wound infections
most frequent causative agent of urinary tract infections is
Escherichia coli
What disease is caused by E. coli O157:H7?
hemorrhagic colitis +/- HUS (hemolytic uraemic syndrome)
What is the reservoir of Salmonella typhi?
humans (with disease, or healthy carriers)
Which bacteria cause most frequently typhoid fever and enteric fever?
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 of otherwise healthy adults?
Ingestion of contaminated food containing a sufficient number of Salmonella (such as
eggs, cream...)
Which antibacterial drugs should be administered in gastroenteritis by Salmonella?
Antibiotics are not usually necessary unless the infection spreads from the intestines.
In case of extraintestinal infection (very young, very old or immunosuppressed
patients): ampicillin, gentamicin, trimethoprim/sulfamethoxazole, or ciprofloxacin.
List the Shigella species causing human disease!
Shigella dysenteriae, S. flexneri, S. boydii, S. sonnei
2 bacterial species belonging to different genera that cause bacillary dysentery
Shigella dysenteriae,enteroinvasive
E. coli (EIEC)
Mention 3 bacterial species belonging to different genera that cause enteritis or
Campylobacter jejuni, Escherichia coli, Salmonella enteritidis
two bacteria causing intestinal infections which have animal reservoirs!
Campylobacter jejuni, Yersinia
Yersinia pestis may infect humans in 2 ways resulting in 2 different courses of disease.
How is plague acquired? How are the 2 different forms of plague termed?
- Bubonic plague is transmitted by the bite of infected rat fleas.
- The pneumonic form spreads directly from human to human via respiratory droplets.
What are the possible portals of entry of Francisella tularensis?
tick bite, mucous membranes, skin abrasions, resp. tract, gastroint. tract
How do humans acquire brucellosis? The Brucellae are located primarily in which organ
system and cells?
Portals of entry are the mucosal surfaces and abraded skin. Organisms spread to the
mononuclear phagocytes of the reticuloendothelial system (lymph nodes, liver,
spleen, bone marrow).
What are the reservoirs of the Brucella species, respectively?
B. abortus: cattle
B. melitensis: goat, sheep
B. suis: swine
What is the mechanism of action of the 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.
How to treat a patient suffering from cholera?
How to treat a patient suffering from 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.
4 diseases caused by Haemophilus influenzae!
purulent meningitis
epiglottitis (obstructive laryngitis)
otitis media and sinusitis
Which disease is caused by Haemophilus ducreyi?
Chancroid (soft chancre or ulcus molle). Sexually transmitted disease (STD).
What can serve as source of infections by Pseudomonas aeruginisa?
Pseudomonas species are normally present in the environment and can be isolated from
the skin, throat, and stool of healthy persons. They often colonize hospital food, sinks,
taps, mops, and respiratory equipment.
4 diseases that are frequently caused by Pseudomonas aeruginosa!
urinary tract infections
wound infections (burns)
pneumonia, sepsis (immunosupression)
otitis externa
Mention at least 3 drugs which may be effective to treat infections caused by
Pseudomonas aeruginosa!
penicillins: piperacillin
3. generation cephalosporins: ceftazidim,
aminoglycosides:tobramycin, carbapenems: imipenem
Which diseases are caused by Legionella pneumophila?
- atypical pneumonia (legionellosis, legionnaires disease)
- Pontiac fever (mild, flu like illness without pneumonia)
4 important virulence factors of Bordetella pertussis!
filamentous hemagglutinin, pertussis toxin, adenylate-cyclase toxin, tracheal
3 bacterium species causing food poisoning!
Staphylococcus aureus, Clostridium perfringens, Clostridium
Which bacterium has the highest germ number in the colon?
Bacteroides fragilis
4 bacterial genera that are obligate anaerobes!
Clostridium, Bacteroides, Prevotella, Porphyromonas,
Which is the most important gas gangrene Clostridium? What is its main virulence factor?
Clostridium perfringens
alpha-toxin (lecitinase)
Mention 3 gas gangrene Clostridium species! How are they acquired?
Clostridium perfringens, C. novyi, C. septicum.
The site of infection is usually a wound that comes into contact with C. perfringens 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; 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?
Spastic paralysis: muscle spasms; lockjaw(trismus), rhisus sardonicus (grimace of the
face), opisthotonus (spasm of the back); respiratory paralysis
What is the mechanism of action of the botulinus toxin? What symptoms does it cause?
What kind of therapy is available?
Blocks release of acetylcholine in peripheral nerve synapses; flaccid paralysis: diplopia
(double vision), dysphagia (difficulty to swallow), dysphonia (hoarseness),
respiratory paralysis; 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 are caused by Helicobacter pylori?
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 ribosomes by ADP
ribosylation of EF-2 (elongation factor-2)
How long does immunity against diphtheria exist? Which immune effector mechanism is
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
2 atypical Mycobacterium species!
M. kansasii, M. marinum
How can one demonstrate the presence of Mycobacterium tuberculosis in clinical
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?
activated macrophages
Mention 3 antituberculotic drugs that are of first choice against Mycobacterium
isoniazid (INH), pyrazinamid, rifampin
What disease is caused by Mycobacterium avium-intracellulare? What patients are
characteristically susceptible to infection?
It causes TB, especially in immunosuppressed patients (such as AIDS patients).
What is the reservoir of Mycobacterium tuberculosis?
What is the reservoir of atypical Mycobacteria?
environment (soil, water)
What are the 2 distinct forms of leprosy?
Tuberculoid, lepromatous forms
3 Gram-negative bacteria belonging to different genera causing zoonosis
Brucella, Francisella tularensis, Yersinia pestis
2 Gram-positive bacteria belonging to different genera causing zoonosis!
Listeria monocytogenes, Bacillus anthracis
3 bacterial species belonging to different genera that are frequent causes of
urinary tract infections!
E. coli, Klebsiella, Proteus
one aerobic and one anaerobic bacterium of the normal flora of the skin!
aerobic: Staphylococcus epidermidis
anaerobic: Propionobacterium acnes
2 Genuses for each category :
Gram + aerobic Gram + anaerobic, Gram - Aeorbic, Gram - Anaerobic
Gram + Aerobic : Staph, Strep
Gram + Anaerobic : Clostridium, Lactobacillus
Gram - Aerobic : Vibrio, Nisseria
Gram - Anerobic : Bacteroids, Prevotella
1 example for each category!
Gram + Coccus, Gram - Coccus, Gram + rod, Gram - rod, Spirochetes
Gram positive coccus: Streptococcus
Gram negative coccus: Neisseria
Gram positive rod: Bacillus
Gram negative rod: E. coli
Spirochetes: Treponema
Describe the color and the shape of Clostridia in a Gram stained smear of gas
gangrene exudate!
Gram positive (dark blue) rod
2 antibiotics which can be used in the empirical treatment against Gram
negative obligate anaerobic bacteria!
Imipenem, Augmentin (amoxicillin + clavulanic acid)
Which 3 bacterial species are the most important causative agents of neonatal (< 1
months of age) meningitis?
Streptococcus agalactiae, E. coli, Listeria monocytogenes
Which 3 bacterial species are the most important causative agents of meningitis
among babies (> 1 months of age) and children?
Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae
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)

Deck Info