Gram (+) Bacteria Flashcards
Name the 2 major categories of Gram (+) Cocci.
Staphylococci and Streptococci
Are Gram + cocci motile or spore-forming?
NEITHER
What lab test definitively tells you staph or strep?
Catalase test.
Staph are catalase +
Strep are catalase -
A Gram +, catalase +, coagulase + microorganism would be what species?
Staph aureus - Defined by the coagulase test.
Name the virulence factors of Staph aureus.
Coagulase - clot formation = antiphagocytic
Protein A - binds IgG, prevents complement activation and is antiphagocytic
Cell wall has endotoxic properties- leads to sepsis
Enzymes that cause skin damage.
Superantigens - TSST and heat-labile enterotoxin that causes food poisoning.
What is one of the most important clinical attributes to look for to visually ID staph aureus?
PYOGENIC INFLAMMATION (Pus)
Name the Pyogenic Infections caused by Staph Aureus.
Abscesses Impetigo Endocarditis Pneumonia Osteomyelitis
What are the 2 options for the ID of a bacteria if the tests reveal it is a gram +, catalase +, COAGULASE (-) organism?
Coagulase (-) indicates it is NOT staph aureus.
Must be:
Staph epidermidis
Staph saprophyticus
One of your admitted patients has an infection in their in-dwelling catheter. There is evidence of BIOFILM formation, but no exotoxins. What bacteria is it, most likely?
Staph epidermidis.
Almost always hospital-squired.
Common infection of implants/in-dwelling catheters
Biofilm formation = virulence
Staph saprophyticus is part of the normal flora where?
GI tract
Staph saprophyticus is second to only E.coli in causing ____________.
UTI’s.
Which of the staph strains produce B-lactamases?
Staph aureus and Staph epi. Penicillin resistant.
What are the 2 lab tests that differentiate between types of Streptococci?
Hemolysis test - alpha, beta, non
Lancefield Antigen - A,B,D, or not types
Lancefield antigen is specifically good for differentiating between what type of hemolytic bacteria?
Beta-hemolytic
If a blood agar plate shows colonies with green tint surrounding them, what type of hemolysis is indicated?
Alpha.
Beta hemolysis is complete RBC lysis and will have clear rings surrounding a colony.
Non hemolytic will show nothing but bacteria growth.
GAS (Group A Strep) is also known as…..
btw is also B-hemolytic
Strep pyogenes
What’s the most common pus-related disease caused by Strep progenies?
Name a couple of less common ones.
PHARYNGITIS: Strep throat
Cellulitis (skin), impetigo, necrotizing fasciitis.
Name the main virulence factors of Strep pyogenes.
M protein (80 serotypes) -pilus, antiphagocytic,
Inflammatory enzymes - streptokinase (dissolves clots)
Streptolysin O - Oxygen-labile hemolysin
____________________ is more commonly known as GBS.
Gram +, catalase -, B-hemolytic
Strep agalacticae
Strep agalacticae inhabits the UG tract of some women and causes what diseases?
Neonatal meningitis and sepsis.
What is the main virulence factor of Strep agalacticae?
Capsule
when you see meningitis, automatically assume capsule
Which bacteria has the virulence factor Streptolysin O?
Strep pyogenes
Which 2 bacteria are Catalase (-), alpha hemolytic, and not lance field typed?
Viridans streptococci and Strep pneumoniae
What is the main virulence factor for Strep Pneumoniae?
Polysaccharide capsule (over 80 serotypes)
What diseases does Strep Pneumoniae cause?
Pyogenic Lobar pneumonia.
Pyogenic meningitis
Pyogenic Otitis media.
WHat bacteria refers to the normal flora of the oropharynx in general? (aka… mixture of bacteria)
Viridans streptococci
Viridans streptococcie cause….? Main virulence factor?
Form biofilms: Pyogenic endocarditis after dental procedures.
You go to the dentist…. (automatically think what?)
Viridans streptococci
GDS (Group D strep) is formally known as….
Enterococci
Enterococci are normal flora of the __________.
Colon.
What is significant about the resistance carried by Enterococci?
Vancomycin resistance is carried in a plasmid within Enterococci. Source of resistance for many bacteria.
A gram positive, spore forming rod with a “boxcar” appearance would be classified as a ___________.
Bacillus
Name the 2 medically significant bacillus species.
B. anthracis
B. cereus
There has been a presumed act of bioterrorism. What bacterial species was involved?
B. anthracis.
You have a black lesion developing on your arm. It’s been there for a while, and eventually you start coughing up dark green sputum in addition to the lesions. Then you think back to the other day when you were at the white house and opened a letter that was meant for President Obama. What are you infected with?
B. anthracis.
Cutaneous anthrax is characterized by black “eschar” lesions on the skin due to spore introduction to a wound.
If left intreated, cutaneous anthrax spreads to the lungs.
Oh shit. You sniffed anthrax spores. What happens now and what are the virulence factors that make it happen?
Inhalational Anthrax:
Fatal if left untreated, due to 2 AB toxins that share a common B subunit.
What happens if you eat reheated rice contaminated with B. cereus?
What virulence factors make it happen?
Food poisoning due to 2 enterotoxins.
Similar to cholera toxin (watery stool), and staph enterotoxin.
Which gram (+) bacteria are obligate anaerobes?
Clostridium. All of them.
This gram + anaerobe is responsible for Gas Gangrene. Name it and its main virulence factor.
Clostridium perfringens has an alpha toxin (lecithinase) that disturbs the integrity of cell membranes. YOUR cell membranes = gas gangrene.
What bacteria is the most common cause of nosocomial diarrhea?
C. difficile.
Resistant to many antibiotics.
C. difficile causes nosocomial diarrhea in patients who have already been treated with antibiotics. Why?
Opportunistic. The patient’s normal flora has been depleted, leaving C. difficult room to inhabit the colon.
What virulence factor does C. difficile have?
Exotoxin A and B.
Which obligate anaerobe causes spastic paralysis?
Clostridium tetani
What are C. tetani cells shaped like?
Tennis rackets
How does tetanus toxin work?
It is a metalloprotease that cleaves SNARES, preventing the release of GABA (inhibitory neurotransmitters). Cells stay stimulated.
Your mom gave your little sister some of her homemade jam and now she has floppy kid syndrome. What bacteria was in mom’s strawberry jam?
Clostridium botulinum - leads to flaccid paralysis
The most potent bacterial toxins known come from which 2 species?
C. tetani and C. botulinum.
How does botulism toxin work?
Metalloprotease that cleaves SNARES to block the release of EXCITATORY NEUROTRANSMITTERS.
Leads to flaccid paralysis.
Tetanus and botulism are treated with ________ rather than antibacterials.
Antitoxins
What bacteria causes diphtheria? (Severe pharyngitis with a pseudomembrane at the back of the throat)
Corynebacterium diphtheria - AB exotoxin
You eat an unpasteurized cheese and deli meat sandwich for lunch. You have watery diarrhea (characteristic of this bacterium) and little do you know, the bacterium you ate just took up transient residence in your vagina. Lucky you aren’t pregnant or you’d have to worry about______________ caused by _________________. (A gram + rod with no spores)
Sepsis or Newborn meningitis caused by Listeria monocytogenes
Nonpathogenic Corynebacteriua are opportunistic commensals called_____________.
Diptheroids
Does Corynebacterium diphtheria form spores?
No
Rusty colored sputum is characteristic of what condition and what bacteria?
Pneumonia caused by Strep Pneumoniae
Both staph aureus and staph epi are resistant to ___________ because they produce _____________.
Resistant to Penicillin G because they produce B-lactamases.
Superantigens are what type of toxin? What bacteria produces 2 of them? Causing what?
Superantigens are EXOTOXINS (secreted)
Staph aureus secrets 2 of them, one causing food poisoning, the other causing Toxic Shock from tampons.
You have an in-dwelling catheter. What bacteria will most likely infect it? What virulence factor will it use?
Staph Epi. due to biofilm formation.
Almost always hospital acquired.
You’ve been having UTI’s related to sex but you know it’s not E.coli. WHat is it, most likely? What lab tests can you run to be sure?
Staph saprophyticus.
Catalase +
Coagulase -
Not Staph epi.
What drug do you give to treat staph?
Vancomycin
You have strep throat. Aka Pharyngitis. What is causing it?
Strep Pyogenes. It’s a pyogenic infection of the throat.
Following a dental procedure, you get pyogenic endocarditis. What bacteria caused this?
Viridans streptococci. (normal flora of the oropharynx gone wrong) Biofilm formation is their biggest virulence factor.
What is the gram (+) version of LPS?
LTA - lipotechoic acid
What enzymes are responsible for the B-hemolytic properties of Strep. progenies?
Streptokinase (dissolves clots- virulence factor)
Streptolysin O (oxygen-labile hemolysin)
Can Strep Pyogenes cause toxic shock?
YES! It has exotoxin properties.
Name the SPORE FORMING Gram (+) Rods.
Any Bacillus (anthracis, cereus)
Clostridium (perfringens, diff, tetani, botulinum)
Pyogenic otitis media, pyogenis memingitis, and LOBAR PNEUMONIA. Name the culprit.
Strep pneumoniae
Inhalational anthrax has 2 AB toxins as its key virulence factors. They share a common B subunit. What do they do to the host?
Edema factor: an adenylate cyclase that spurs fluid secretion
Lethal factor: PROTEASE that inhibits cell growth
The Exotoxins of C. diff cause what to happen to a cell.
C.difficile = #1 cause of nosocomial diarrhea.
Toxins lead to depolymerization of actin and cell death.
How do you get tetanus?
Spores get in an open wound.
Describe tetanus toxin.
Metalloprotease that cleaves SNARES preventing the release if INHIBITORY NEUROTRANSMITTERS (GABA)
Spastic paralysis
Describe Botulism Toxin.
metalloprotease that cleaves SNARES and block the release of EXCITATORY NEUROTRANSMITTERS (Ach)
Flaccid paralysis.
The consumption of pre-formed exotoxin from improperly canned food is an _________, not an infection.
Intoxication.
How do you treat tetanus and botulism?
Antitoxins.
Name the 2 non-spore forming Gram (+) rods.
Corynebacterium diphtheria and Listeria Monocytogenes.
What kind of toxin does Diptheria have and what does it do?
AB exotoxin - ADP-ribosylates EF-2, blocking translation.
Listeriosis is what?
Watery diarrhea caused by listeriamonocytogenes’
