Bacteriology Flashcards
Which bacteria are beta-hemolytic?
agh
Nocardia produce which gas?
On triple sugar media H2S.
Which bacteria produces H2S?
Erythripolocsis rhuisiopathe
Which bacteria have gelatinase?
Enterococci, Ba
Urease positive
Corynebacterium urealyticum, Corynebacterium ulcerans, Corynebacterium pseudotuberculiosis, Nocardia
Which bacteria are especially dangerous during pregancy?
Listeria monocytogenes, Strectociccus pyogenes, S. agalactiae
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What type of organisms stain purple/blue with Gram staining?
Gram-positive organisms
Gram-positive organisms are commonly classified into which two shapes?
Cocci or rods (bacilli)
Name four gram-positive rods.
Clostridium, Listeria, Bacillus, and Corynebacterium
Name one gram-positive anaerobic rod.
Clostridium
Staphylococcus and Streptococcus are differentiated by which enzyme?
Catalase; Staphylococcus is catalase positive, and Streptococcus is catalase negative
Which gram-positive cocci are found in clusters?
Staphylococcus
Which gram-positive cocci are found in chains?
Streptococcus
What differentiates Staphylococcus aureus from and other staph species?
Other staph species are coagulase negative
Name two coagulase-negative Staphylococcus species.
Staphylococcus saprophyticus and Staphylococcus epidermidis
Which Staphylococcus species is novobiocin sensitive?
Staphylococcus epidermidis
Which Staphylococcus species is novobiocin resistant?
Staphylococcus saprophyticus
If agar shows clear hemolysis, which Streptococcus species could be present?
Streptococcus pyogenes or Streptococcus agalactiae
What type of hemolysis do both group A and group B streptococci have in common?
β-Hemolysis
Streptococcus pyogenes is a type of group _____ Streptococcus, whereas Streptococcus agalactiae is a type of group _____ Streptococcus.
A, B
How are -hemolytic streptococci differentiated from each other?
By their bacitracin sensitivity (Streptococcus pyogenes is sensitive, Streptococcus agalactiae is resistant)
Name two streptococci that are -hemolytic.
Enterococcus and Peptostreptococcus (anaerobic)
True or False: Enterococcus faecalis is a -hemolytic, gram-positive, catalase-negative cocci.
True
Which -hemolytic streptococcal species is bacitracin resistant?
Group B Streptococcus (Streptococcus agalactiae)
Which -hemolytic streptococcal species is bacitracin sensitive?
Group A Streptococcus (Streptococcus pyogenes)
Staphylococcus saprophyticus is novobiocin _____ (resistant, sensitive); staphylococcus epidermidis is novobiocin _____ (resistant, sensitive).
Resistant; sensitive (remember: On the staph retreat there was NO StRES; Novobiocin: Saprophyticus Resistant, Epidermidis Sensitive)
Group A streptococci are bacitracin _____ (resistant, sensitive); group B streptococci are bacitracin _____ (resistant, sensitive).
Sensitive; resistant (remember: Bacitracin: group B are Resistant, whereas group A are Sensitive (B-BRAS)
Streptococcus viridans is optochin _____ (resistant, sensitive); streptococcus pneumoniae is optochin _____ (resistant, sensitive).
Resistant; sensitive (remember, Optochin: Viridans Resistant and Pneumonia Sensitive; OVRPS- overpass)
What bacterial enzyme degrades hydrogen peroxide?
Catalase
What antimicrobial product produced by polymorphonuclear lymphocytes is a substrate for myeloperoxidase?
Hydrogen peroxide
Which gram-positive cocci are catalase positive?
Staphylococci
What differentiates Staphylococcus aureus from Staphylococcus epidermidis and Staphylococcus saprophyticus?
Coagulase (Staphylococcus aureus is coagulase positive)
Why do people with chronic granulomatous disease (nicotinamide adenine dinucleotide phosphate oxidase deficiency) get recurrent infections by catalase-producing organisms?
Bacterial catalase easily degrades the little hydrogen peroxide produced, compromising the ability of neutrophils to kill bacteria
What is the function of Protein A, a Staphylococcus aureus virulence factor?
Binding to fragment crystallizable region-immunoglobulin G, to inhibit complement fixation and phagocytosis
Name five types of infections caused by Staphylococcus aureus.
Skin infections, organ abscesses, pneumonia, acute bacterial endocarditis, and osteomyelitis
Staphylococcus aureus can cause which toxin-mediated conditions?
Toxic shock syndrome (toxic shock syndrome toxin 1), scalded skin syndrome (exfoliative toxin), and rapid-onset food poisoning (enterotoxins)
Which organism produces toxic shock syndrome toxin 1?
Staphylococcus aureus
What is the pathophysiology of toxic shock syndrome?
Toxic shock syndrome toxin 1 acts as a superantigen and causes widespread release of cytokines from T cells
Staphylococcus aureus can cause rapid-onset food poisoning as a result of what product?
Preformed enterotoxins
Methicillin-resistant Staphylococcus aureus is resistant to methicillin because of its altered structure of what protein?
Penicillin-binding protein
What bacterium found in normal skin flora commonly contaminates blood cultures and infects prosthetic devices and catheters?
Staphylococcus epidermis
How does Staphylococcus epidermis infect prosthetic devices and intravenous catheters?
By producing adherent biofilms
What four common infections does Staphylococcus pneumoniae cause?
Meningitis, Otitis media, Pneumonia, and Sinusitis (remember: MOPS are Most OPtochin Sensitive)
What is distinct about the pneumonia caused by pneumococcus?
“Rust”-colored sputum
Streptococcus pneumoniae sepsis occurs at a higher rate in what two patient populations?
Sickle cell anemia and asplenic patients
Name two ways Streptococcus pneumoniae evades the immune system.
Immunoglobulin A protease, encapsulation
What three pyogenic infections does Streptococcus pyogenes cause?
Pharyngitis, cellulitis, and impetigo
What two toxigenic diseases does Streptococcus pyogenes cause?
Scarlet fever and toxic shock syndrome
What two immunologic conditions does Streptococcus pyogenes cause?
Rheumatic fever and glomerulonephritis (remember: PHaryngitis gives you rheumatic “PHever” and glomerulonePHitis)
Streptococcus pyogenes is associated with what three major classes of disease?
Infectious, immunogenic, and toxigenic
Human antibodies to Streptococcus M protein enhance host defenses but increase the risk for which complication of streptococcal infection?
Rheumatic heart disease
What blood test would detect a recent Streptococcus pyogenes infection?
An antistreptolysin O titer
Rheumatic fever is associated with what five symptoms?
Subcutaneous nodules, Polyarthritis, Erythema marginatum, Chorea, and Carditis (remember, there is no “RHEUM” for SPECCulation)
Streptococcus agalactiae are bacitracin _____ (sensitive/resistant) and _____(//) -hemolytic.
Resistant
In what population does group B Streptococcus (Streptococcus agalactiae) cause pneumonia, meningitis, and sepsis?
Babies (remember: B for Babies)
What two infections do enterococci cause?
Urinary tract infection and subacute bacterial endocarditis
How can group D enterococci be differentiated from nonenterococcal group D streptococci by lab testing?
Enterococci can grow in 6.5% sodium chloride, other group D streptococci cannot
Lancefield grouping is based on differences in what components of the bacteria?
C carbohydrate on the bacterial cell wall
True or False? Penicillin G is effective treatment against enterococci.
False; enterococci are resistant to penicillin G
Enterococci resistant to which antibiotic are an important source of nosocomial infection?
Vancomycin
What two infections does Streptococcus bovis cause in colon cancer patients?
Bacteremia and subacute endocarditis
A young patient presents with pseudomembranous pharyngitis; what medium could be used to culture the most likely etiologic agent?
Corynebacterium diphtheriae grows on tellurite agar (coryne = club shaped)
The symptoms of diphtheria are caused by what kind of toxin?
Exotoxin (encoded on the -prophage)
How does diphtheria toxin inhibit protein synthesis?
By the adenosine diphosphate ribosylation of elongation factor 2
What disease is caused by Corynebacterium diphtheriae?
Diphtheria; characterized by pseudomembranous pharyngitis (grayish-white membrane) with lymphadenopathy
How is a laboratory diagnosis of diphtheria made based on microscopic appearance?
The presence of gram-positive rods with metachromatic granules (blue and red in color)
How can diphtheria be prevented?
Toxoid vaccine; usually administered in combination with tetanus vaccine
What type of bacteria form spores?
Gram-positive rods
What advantages do bacteria gain by taking the form of a spore?
They become highly resistant to destruction by heat and chemicals and require no metabolic activity in nutrient-poor settings
Why is it important to autoclave surgical equipment?
To kill bacterial spores
What five soil-dwelling, gram-positive rods are spore formers?
Bacillus anthracis, Bacillus cereus, Clostridium perfringens, Clostridium botulinum, and Clostridium tetani
Which bacteria are gram-positive, spore-forming, obligate anaerobic bacilli?
Clostridia species
Name four clostridia species that produce exotoxins.
Clostridium tetani, Clostridium botulism, Clostridium perfringens and Clostridium difficile
What kind of toxin produced by Clostridium tetani causes symptoms of tetanus?
An exotoxin called tetanospasmin
Describe the pathogenesis of the symptoms caused by Clostridium tetani?
Clostridium tetani toxins block glycine (an inhibitory neurotransmitter) release from Renshaw cells in the spinal cord, leading to spastic paralysis, lockjaw (trismus), and risus sardonicus (remember: TETanus is TETanic paralysis)
Which gram-positive bacilli are responsible for the flaccid paralysis caused by exposure to improperly canned foods?
Clostridium botulinum (remember: BOTulinum is from bad BOTtles of food)
What are the characteristics of the toxin produced by Clostridium botulinum?
Preformed, heat-labile toxin
What is the predominant symptom of botulism?
Flaccid paralysis
How does the toxin produced by Clostridium botulinum cause flaccid paralysis?
It inhibits acetylcholine release
How does the pathogenesis of botulism differ between adults and babies?
Adults consume preformed toxin whereas babies consume spores in honey (floppy baby syndrome)
Which exotoxin-producing, gram-positive bacillus is responsible for gas gangrene?
Clostridium perfringens (remember: PERFringens PERForates a gangrenous leg)
What is the effect of the toxin produced by Clostridium perfringens?
Toxin (lecithinase) causes myonecrosis, gas gangrene, and hemolysis
Which gram-positive bacillus is responsible for pseudomembranous colitis?
Clostridium difficile (remember: DIfficile causes DIarrhea)
Pseudomembranous colitis often follows a course of which antibiotics?
Clindamycin and ampicillin
What kind of toxin is produced by Clostridium difficile?
A cytotoxin, which is an exotoxin that kills enterocytes and causes pseudomembranous colitis
