Micro - Clinical Bacteriology Flashcards
What are the two functions of the peptidoglycan layer in bacteria?
Rigid support and protection against osmotic damage
What is the chemical composition of the bacterial peptidoglycan layer?
A sugar backbone with cross-linked peptide side chains
What is the major surface antigen in gram-positive bacteria?
Cell wall
Which two cytokines does teichoic acid induce?
Tumor necrosis factor and interleukin-1
What structure in gram-negative bacteria induces tumor necrosis factor and interleukin-1?
The lipid A component of lipopolysaccharide
What is the major surface antigen in gram-negative bacteria?
Outer membrane (polysaccharide component of lipopolysaccharide)
Where is endotoxin (lipopolysaccharide) located in gram-negative bacteria?
In the outer membrane
Which bacterium has a nonpolysaccharide capsule?
Bacillus anthracis (which has D-glutamate)
_____ are bacterial structures that mediate adherence to the host cell surface and
are composed of glycoprotein.
Fimbriae (pili)
What bacterial structure establishes attachment between two bacteria during
conjugation?
Sex pili
_____ are bacterial structures that provide motility and are composed of protein.
Flagella
What bacterial structure provides resistance to desiccation, heat, and chemicals?
Spores
What is the chemical composition of a spore?
Keratin-like coat and dipicolinic acid
What kind of genetic information is stored in the bacterial plasmid?
Genes for antibiotic resistance, enzymes, and toxins
What structure aids bacteria in adhering to foreign objects, such as indwelling
catheters?
Glycocalyx
What is the chemical composition of glycocalyx?
Polysaccharide
What structures are common to both gram-positive and gram-negative bacteria?
Flagellum, pilus, capsule, peptidoglycan, and cytoplasmic membrane
What structure is unique to gram-positive organisms?
Teichoic acid
What structures are unique to gram-negative organisms?
Outer membrane (endotoxin/lipopolysaccharide)-lactamases in periplasmic space
What is between the capsule and peptidoglycan layers in gram-negative
organisms?
The outer membrane (which contains endotoxin/lipopolysaccharide)
What is the difference between the peptidoglycan layer of gram-positive organisms and that of gram-negative organisms?
The peptidoglycan layer in gram-positive bacteria is much thicker than that of gram-negative bacteria
What is between the inner cytoplasmic and outer membranes in gram-negative
organisms?
Periplasmic space (the location of many enzymes, including -lactamases)
Name the two major gram positive cocci.
Staphyloccus and Streptococcus
What are the major gram negative cocci?
Neisseria
Clostridium is a _____ (gram positive/gram negative) _____ (coccus/bacillus) .
Gram positive bacillus
Corynebacteriumis a _____ (gram positive/gram negative) _____
(coccus/bacillus).
Gram positive bacillus
Listeria is a _____ (gram positive/gram negative) _____ (coccus/bacillus).
Gram positive bacillus
What unique staining characteristic do Mycobacteriumand Nocardiapossess?
Mycobacterium and Nocardia are acid fast
Haemophilus is a _____ (gram positive/gram negative) _____ (coccus/bacillus).
Gram negative bacillus
Legionella is a _____ (gram positive/gram negative) _____ (cocci/bacillus).
Gram negative bacillus
Bordatella is a _____ (gram positive/gram negative) _____ (coccus/bacillus).
Gram negative bacillus
Yersinia is a _____ (gram positive/gram negative) _____ (coccus/bacillus).
Gram negative bacillus
Francisella is a _____ (gram positive/gram negative) _____ (coccus/bacillus).
Gram negative bacillus
Brucella is a _____ (gram positive/gram negative) _____ (cocci/bacillus).
Gram negative bacillus
Pasteurella is a _____ (gram positive/gram negative) _____ (coccus/bacillus).
Gram negative bacillus
Bartonella is a _____ (gram positive/gram negative) _____ (cocci/bacillus).
Gram negative bacillus
Gardnerella is a _____ (gram positive/gram negative) _____ (coccus/bacillus).
Gram negative bacillus (gram staining can be variable)
What are the two types of gram positive branching, filamentous bacteria?
Actinomyces and Nocardia
Name three types of spirochetes.
Leptospira, Borrelia, Treponema
What type of bacteria contains sterols but lacks cell walls?
Mycoplasma
What type of bacteria contain mycolic acid in their cell walls and have high lipid
content?
Mycobacteria
Name six organisms that do not stain well by Gram stain.
Treponema, Rickettsia, Mycobacteria, Mycoplasma, Legionella pneumophila,
and Chlamydia
Remember: These rascals may microscopically lack color
Name two methods used for visualizing treponemes.
Dark field microscopy and fluorescent antibody staining
Name three predominantly intracellular parasites that do not Gram stain well.
Rickettsia, Legionella, and Chlamydia
Mycobacteria can be visualized by acid-fast stain as a result of what characteristic?
High lipid content in the cell wall
What is the reason that Mycoplasma do not Gram stain?
It does not have a cell wall
Which primarily intracellular organism does not Gram stain well but can be seen
with silver stain?
Legionella pneumophilia
Borrelia, Plasmodium, Trypanosoma, and Chlamydiaspecies can be visualized
using what type of stain?
Giemsa stain
Periodic acid-Schiff (PAS) staining is used to stain what types of metabolic
substances?
Glycogen and mucopolysaccharides (PASs the sugar)
True or False: Periodic acid-Schiff staining is used to diagnose Whipples disease.
True
Ziehl-Neelsen stain is used to stain what organisms?
Acid-fast bacteria
India ink and mucicarmine can be used to visualize what pathogen?
Cryptococcus neoformans
Silver stain is used to stain what organisms?
Pneumocystis and Legionella
Haemophilus influenzae requires what medium to grow?
Chocolate agar with factors V (NAD) and X (hematin)
Neisseria gonorrhoeae requires what medium to grow?
Thayer-Martin (VPN) media
Bordetella pertussis requires what medium to grow?
Bordet-Gengou (potato) agar
Which media are used to culture Corynebacterium diphtheriae?
Tellurite plate, Loefflers medium
Mycobacterium tuberculosis requires what medium to grow?
L&wenstein-Jensen agar
Lactose-fermenting enterics on MacConkeys agar grow colonies that are what
color?
Pink
Legionella requires what medium to grow?
Charcoal yeast extract agar buffered with cysteine
Fungi require what medium to grow?
Sabourauds agar
In what medium can Mycoplasma pneumoniae grow?
Eatons agar
Escherichia colic an grow on what medium other than MacConkeys agar?
Eosin-methylene blue agar
What is the appearance of Escherichia coliwhen it is grown on eosin-methylene
blue agar?
Colonies with blue-black color and metallic sheen
Which bacteria are obligate aerobes?
They are all obligate aerobes (remember: Nocardia, Pseudomonas
aeruginosa, Mycobacterium tuberculosis,
and Bacillus = Nagging Pests Must Breathe)
Why does Mycobacterium tuberculosis have a predilection for the apices of the
lung?
The apices of the lung have the highest partial pressure of oxygen
Which aerobe is commonly associated with burn wound infections, nosocomial
pneumonia, and pneumonias in patients with cystic fibrosis?
Pseudomonas aeruginosa (remember: Pseudomonas AERuginosa is an AERobe)
What do Clostridium, Bacteroides, and Actinomyceshave in common?
They are obligate anaerobes (remember, they Cannot Breathe Air)
The lack of which enzymes makes obligate anaerobes susceptible to oxidative
damage?
Catalase and/or superoxide dismutase
What are characteristics of anaerobe infections in tissue?
They are generally foul smelling and difficult to culture and produce carbon
dioxide and hydrogen gas
Why are aminoglycosides ineffective against anaerobes?
AminOglycosides require Oxygen to enter a bacterial cell
Which organisms are obligate intracellular organisms that cannot make their own
ATP?
Rickettsia and Chlamydia(remember: Stay inside (cells) when it is Really Cold)
Which bacteria are facultative, intracellular organisms?
Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, and Yersinia
(remember: Some Nasty Bugs May Live FacultativeLy)
Name five encapsulated bacteria.
Klebsiella pneumoniae, Salmonella, Streptococcus pneumoniae, Haemophilus
influenzae and Neisseria meningitidis
(remember: Kapsules Shield SHiN)
A polysaccharide capsule adds virulence by what mechanism?
Preventing phagocytosis
Which test is used to see if an organism is encapsulated?
The Quellung reaction, in which the capsule swells (remember: Quelling =
capsular swellung)
What part of the bacteria is used as antigen in vaccines against Streptococcus
pneumoniae, Haemophilus influenzae type B, and Neisseria meningitidis?
The capsule
In the synthesis of vaccines against encapsulated bacteria, conjugation of
polysaccharides with protein has what effect on the bodys immune response?
Increases immunogenicity and T-cell-dependent response
Which four bacteria are urease-positive?
Helicobacter pylori, Proteus, Klebsiella, and Ureaplasma
(remember: Particular Kinds Have Urease
Staphylococcus aureus produces a _____ (yellow, red, or blue-green) pigment.
Yellow
Pseudomonas aeruginosaproduces a _____ (yellow, red, or blue-green) pigment.
Blue-green
Serratia marcescensproduces a _____ (yellow, red, or blue-green) pigment.
Red
_____ produces yellow “sulfur” granules.
Actinomyces israelii
remember: Israelhas yellow sand
Protein A in Staphylococcus aureus binds to the _____ region of immunoglobulin
and disrupts two immune functions, _____and _____.
Fc; Opsonization and phagocytosis
Immunoglobulin A protease is secreted by which bacteria?
Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria
What protein from Group A Streptococcusprevents phagocytosis by the bodys
immune cells?
M protein
Exotoxins are found in which of the following: gram-negative bacteria, gram-
positive bacteria, or both?
Both gram-negative and gram-positive bacteria
In what structures and in what type of bacteria are endotoxins found?
Endotoxins are found in the outer membrane of most gram-negative bacteria and
in Listeria
Exotoxins _____ (are, are not) secreted; Endotoxins _____ (are, are not) secreted.
Exotoxins are secreted; endotoxins are not secreted
What is the difference in the chemical composition of endotoxin vs exotoxin?
Exotoxins are polypeptides whereas endotoxins are lipopolysaccharides
Where are the genes for exotoxin located?
In the plasmid or the bacteriophage
Where are the genes for endotoxin located?
In the bacterial chromosome
What are the major clinical effects of endotoxin and how are they induced?
Fever and shock due to induction of tumor necrosis factor and interleukin-1
Which bacterial toxin (endotoxin or exotoxin) can be used as a vaccine?
Exotoxin toxoid is used as a vaccine against exotoxin-producing organisms
_____ (endotoxin, exotoxin) is heat stable; _____ (endotoxin, exotoxin) is not.
Endotoxins (stable at 100°C for 1 hour), exotoxins (destroyed rapidly at 60°C,
except staphylococcal enterotoxin)
Which organism produces an exotoxin that is heat stable?
Staphylococcus aureus
Bacteria that cause tetanus, botulism, and diphtheria involve which kind of toxin?
Exotoxins
Gram-negative rods that cause meningococcemia and sepsis involve which kind of
toxin?
Endotoxins
Superantigens directly bind to which two receptors?
Major histocompatibility complex II and T-lymphocyte receptor
The binding of superantigens to MHC II and T-cell receptor results in the
widespread release of what factors?
Interferon and IL-2
Name two characteristic organisms with superantigen exotoxins.
Staphylococcus aureus and Streptococcus pyogenes
Which two Staphylococcus aureus toxins cause disease in humans?
Toxic shock syndrome toxin 1 and enterotoxin
What are the symptoms of toxic shock syndrome?
Fever, rash, and shock
Which toxin produced by Staphylococcus aureus causes food poisoning?
Enterotoxin
Staphylococcus aureus exfoliatin can cause what illness?
Staphylococcus scalded skin syndrome
The superantigen released by Streptococcus pyogenes causes what syndrome?
Toxic shock-like syndrome (caused by erythrogenic toxin)
What are the functions of the two components of the A-B toxins found in certain
bacteria, such as Corynebacterium diphtheriae?
B (binding) allows endocytosis and A (active) ADP-ribosylates host cell proteins
Name four organisms that have adenosine diphosphate ribosylating A-B toxin.
Corynebacterium diphtheriae, Vibrio cholerae, Escherichia coli, and Bordetella pertussis
Which two organisms adenosine diphosphate ribosylating A-B toxins stimulate
adenylate cyclase?
Vibrio choleraeand Escherichia coli
Diphtheria toxin causes pharyngitis and a pseudomembrane in the throat by the
adenosine diphosphate ribosylation of what factor?
Elongation factor 2
What organism causes pharyngitis with pseudomembrane formation?
Corynebacterium diphtheriae
What is the effect of increased adenylyl cyclase activity caused by cholera toxin?
Increased chloride pumping into gut and decreased sodium absorption, pulling
excess water into the gut
The toxin released by what bacterium produces what is commonly referred to as
rice-water diarrhea?
Vibrio cholerae
_____ (adenylate, guanylate) cyclase is stimulated by the heat-labile toxin
of Escherichia coli, whereas _____ (adenylate, guanylate) cyclase is stimulated by
the heat-stabile toxin of Escherichia coli.
Adenylate, guanylate (remember: labile like the air, stable like the ground)
Which organism causes whooping cough?
Bordetella pertussis
How does Bordetella pertussis toxin cause lymphocytosis?
By the inhibition of the chemokine receptor
Pertussis toxin causes the _____ (stimulation/inhibition) of Gi, which results in an
_____ (increase/decrease) in cAMP
Inhibition; increase
Which organism causes gas gangrene and what toxin is responsible?
Clostridium perfringens causes gas gangrene by release of its toxin (lecithinase)
What is the characteristic finding of Clostridium perfringens plated on blood agar?
Double zone of hemolysis
Clostridium tetani tetanus causes lockjaw by decreasing the level of what
neurotransmitters?
Glycine and GABA (both are inhibitory neurotransmitters)
What is the mechanism of botulinum toxin-induced paralysis?
Inhibition of the release of acetylcholine
What foods are associated with botulism?
Canned food and honey
Name two organisms that produce Shiga toxin.
Shigella and Escherichia coli O157:H7
What does Shiga toxin do in the host cell?
Shiga toxin cleaves host cell rRNA inactivating the 60S ribosomal subunit
Exaggerated release of cytokines caused by Shiga toxin can lead to what
syndrome?
Hemolytic-uremic syndrome
Which antibody is used to help diagnose rheumatic fever?
Antistreptolysin O antibody
Antistreptolysin O antibody
Vibrio cholerae toxin causes watery diarrhea by permanently activating which
protein?
Gs
Pertussis toxin causes whooping cough by permanently disabling which protein?
Gi (Turns the off off)
Both cholera and pertussis toxins act by adenosine diphosphate ribosylation that permanently _____ (activates/inactivates) adenyl cyclase, thereby _____ (increasing/decreasing) cAMP.
Activates; increasing
What is the mechanism of action of Bacillus anthracis edema factor?
Edema factor is a bacterial form of adenylate cyclase, which increases levels of cAMP
How does anthrax edema factor differ from pertussis, cholera, and Escherichia colitoxin induction of cAMP production?
Anthrax edema factor is itself an adenylate cyclase, whereas pertussis, cholera,
and Escherichia colitoxins permanently activate endogenous adenylate cyclase
What is the chemical composition of endotoxin and where is it found?
It is a lipopolysaccharide found in the cell walls of gram-negative bacteria
What type of bacteria has endotoxins, gram-positive or gram-negative?
Gram-negative bacteria (remember: eNdotoxin is an integral part of the cell wall of
gram-Negative bacteria)
What is the most active part of an endotoxin?
Lipid A
Which cell type is activated by endotoxins?
Macrophages
How is complement activated by endotoxins?
Via the alternative pathway
Endotoxins activate the coagulation cascade via what factor?
Hageman factor
The activation of macrophages by endotoxin results in the release of which
substances?
Interleukin-1, tumor necrosis factor, and nitric oxide
The release of which cytokines by endotoxin-activated macrophages results in
fever?
Interleukin-1 and tumor necrosis factor
The release of nitric oxide by endotoxin-activated macrophages results in what
condition?
Hypotension (shock)
Which component of the alternative complement pathway causes hypotension and
edema?
C3a
The activation of the coagulation cascade by endotoxins results in what condition?
DIC
What are the four phases of the bacterial growth curve?
Lag phase, log phase, stationary phase, and death phase
During which phase of the bacterial growth curve is there metabolic activity without division?
Lag phase
During which phase of the bacterial growth curve is there rapid cell division?
Log phase
What is the cause of slowed growth during the stationary phase of the bacterial
growth curve?
Nutrient depletion
During which phase of the bacterial growth curve does spore formation occur in
some bacteria?
Stationary phase
What causes cell death during the death phase of the bacterial growth curve?
Prolonged nutrient depletion and a buildup of waste products
The process of direct DNA transfer from one bacterium to another is called what?
Conjugation
What type of bacterial genetic transfer involves the phage-mediated transfer of
DNA between prokaryotes?
Transduction
What kind of DNA is transferred during transformation: chromosomal, plasmid, or
both?
Both
What type of bacterial genetic transfer involves the direct uptake of purified DNA
by both prokaryotes and eukaryotes?
Transformation
Are chromosomal and plasmid genes transferred in F+ F- conjugation or in Hfr F-
conjugation?
Hfr F-conjugation; ONLY plasmid genes are transferred in F+F- conjugation
What kind of DNA is transferred during transposition: chromosomal, plasmid, or
both?
Both
When DNA is transferred from one chromosome (or plasmid) to another within the
same cell it is called _____.
Transposition
When an F+plasmid is incorporated into the chromosomal DNA of a bacterial cell,
that cell is then termed an _____ cell.
Hfr
What type of transduction is described here: a lytic phage infects a bacterium,
cleaves the bacterial DNA, and repackages bacterial DNA in viral capsids to infect
other bacteria.
Generalized transduction
What type of transduction is described here: a lysogenic phage infects a bacterium,
inserts DNA into the chromosomal DNA of the bacterium, and repackages
flanking chromosomal DNA into its capsid upon excision to infect other bacteria.
Specialized transduction
Specialized transduction
In which of the following can chromosomal DNA not be incorporated into
transferred DNA: generalized transduction, specialized transduction, F+ F-
conjugation, Hfr F- conjugation and transposition.
F+ F- conjugation
Name 5 bacterial toxins coded for in a lysogenic phage.
ShigA-like toxin, Botulism toxin, Cholera toxin, Diptheria toxin, Erythrogenic
toxin of Streptococcus pyogenes
(remember: ABCDE)
