Bacteria (Part I) Flashcards
1
Q
what are the three methods of transfer of plasmids?
A
direct conjugation, infective viral transduction, or transformation
2
Q
Why are plasmids significant?
A
they confer various factors and traits to bacteria allowing them additional virulence factors or antibiotic resistance
3
Q
What are the 4 steps following heat fixing material to slide?
A
1) Crystal violet (primary dye) 2) Iodine (dye trapping agent) 3) Alcohol (decolorizer) 4) Safranin (counterstain)
4
Q
Why are gram positive bacteria purple?
A
they have a relatively thick cross-linked cell wall made up of peptidoglycan which helps to retain the crystal violet stain
5
Q
What is the composition of gram negative cell walls?
A
they have thinner cell walls with a high lipid content which is primarily washed away by the alcohol
6
Q
What gives gram negative bacteria their pink stain?
A
the safranin (the counterstain)
7
Q
the gram positive bacteria have a thick peptidoglycan wall with embedded what? (2)
A
techoic and lipoteichoic acids
8
Q
What is used in serologic bacterial identification? (2)
A
techoic and lipoteichoic acids
9
Q
What do the lipopolysaccharides on the gram negative bacteria cell wall contain?
A
lipid A- which can act as an endotoxin
10
Q
What are 2 gram stain exceptions?
A
gram variable bacteria and acid fast bacilli
11
Q
what are 2 examples of gram variable bacteria?
A
clostridium and bacillus species
12
Q
What is an example of an acid fast bacilli?
A
mycobacterium tuberculosis
13
Q
What do acid fast bacilli contain and why is this important?
A
they contain mycolic acids, which make it difficult for the gram stain to penetrate the waxy cell wall
14
Q
How is the acid fast stain different from the gram stain?
A
the acid fast stain has a different primary stain and counter stain the the typical gram stain. It also utilizes an acid decolorizer step
15
Q
how are cocci bacteria characterized?
A
spherical balls
16
Q
how can cocci be arranged? (3)
A
in pairs called diplococci, chains called streptococci, or clusters called staphylococci
17
Q
Some bacilli have unique features such as what?
A
the presence of spores or the presence of club shaped ends
18
Q
when a bacteria has an ovoid shape in between a rod and a sphere what is it referred to as?
A
coccobacillus
19
Q
what are the helical shaped bacteria called?
A
spirochete
20
Q
what are the curvilinear bacteria referred to as?
A
spirilla
21
Q
Besides gram stains, what else can be used to see spirochetes and spirilla bacteria?
A
silver stain
22
Q
what are the comma shaped bacteria?
A
vibrio
23
Q
What are the pros and cons of molecular techniques for microbiology?
A
pros: sensitive and specific cons: expensive
24
Q
what is serology utilized for?
A
organisms that don’t culture well (fastidious organisms) and for which there is not a good nucleic acid test developed
25
what is an example of an organism that uses serologic tests for diagnosis?
syphilis- from Treponema pallidum
26
What are the 6 major types of gram positive disease causing bacteria?
1) Staphylococcus 2) Streptococcus/Enterococcus 3) Bacillus 4) Clostridium 5) Corynebacterium 6) Listeria
27
the major gram positive disease causing bacteria consist of two main groups. What are these groups?
Cocci and Bacilli
28
How can the gram positive cocci be further broken down?
based on whether the organisms are catalase + or Catalase -
29
How can the gram positive bacilli be further broken down?
based on whether the organism is spore forming or non spore forming
30
how can the gram positive spore forming bacilli be further broken down?
based on whether the organism can grow in oxygen or whether it is anaerobic
31
how can the gram positive non-spore forming bacilli be further broken down?
whether they are club shaped or whether they are motile at 25 degrees C
32
What is catalase?
an enzyme that breaks down hydrogen peroxide- some bacteria produce it as a defense mechanism to the hydrogen peroxide produced by macrophages and neutrophils
33
what is the catalase test?
a test that shows that a catalase positive organism will reduce hydrogen peroxide which produces bubbles and water when exposed to hydrogen peroxide
34
What is the main group of catalase + gram positive cocci?
staphylococcus
35
what is the main groups of catalase - gram positive cocci?
streptococcus/enterococcus
36
what are the two main groups of spore-forming gram positive bacilli?
bacillus and clostridium
37
which spore-forming gram positive bacilli is aerobic?
bacillus
38
which spore-forming gram positive bacilli is anerobic?
Clostridium
39
What are the two main groups of non-spore forming gram positive bacilli?
Corynebacterium diptheriae and listeria monocytogenes
40
Which non-spore forming gram positive bacilli is non-motile?
corynebacterium
41
which non-spore forming gram positive bacilli is motile at cooler temperatures below 25-30 degrees C?
listeria
42
what are the three principal pathogens that make up the staphylococcus species?
1) Staphylococcus aureus 2) Staphylococcus epidermis 3) staphylococcus saprophyticus
43
How can the catalase positive staphylococcus group be further broken down/ organized?
based on whether the organism is coagulase positive or negative
44
Which principal pathogen(s) of the staphylococcus species is coagulase positive?
Staphylococcus aureus
45
which principal pathogen(s) of the staphylococcus species is coagulase negative?
staphylococcus epidermis and staphylococcus saprophyticus
46
how does staphylococcus aureus appear on the agar plate?
as golden yellow colonies
47
what is the significance of staphylococcus aureus being coagulase positive?
coagulase is a protective protein that activates the fibrin clot (creates a surrounding protective clot)
48
what are the other protective proteins/ virulence factors that staphylococcus aureus has? (4)
hemolysins (destroys RBCs), leukocidins (destroy white blood cells), penicillinase (breaks up penicillin), and a protein A which prevents antibody mediated binding
49
What are the 3 tissue destroying proteins/enzymes that staphylococcus aureus produces?
hyaluronidase, staphylokinase, and lipase
50
What are the four main diseases that are caused by staphylococcus aureus?
pneumonia, superficial skin and underlying soft tissue infections, septic osteomyelitis, endocarditis
51
what are the majority of infections due to staphylococcus aureus in healthy individuals?
that of superficial skin and soft tissue infections
52
what are 4 examples of the superficial skin and underlying soft tissue infections that staphylococcus aureus can cause?
folliculitis, impetigo, cellulitis, and furuncles/carbuncles
53
what is cellulitis?
infection of the subcutaneous tissue just adjacent to the skin which manifests with erythema and tenderness
54
What is the difference between a carbuncle and a furuncle?
a carbuncle is the contiguous multiple pus filled cavities; a furuncle is the subcutaneous abscess
55
septic arthritis/ septic osteomyelitis caused by staphylococcus aureus is more prevalent in who?
children <12 years and the elderly
56
what are the characteristics of the PNA caused by staphylococcus aureus?
necrotizing PNA with high fever and chills, productive cough and lung abscesses seen on chest x-ray; it does not typically occur in the normal healthy patient, but rather it is seen after an initial infection which weakens the body's defenses (such as as initial viral illness)
57
what is the acute necrotizing endocarditis caused by staphylococcus aureus characterized by?
high fever, chills, and weakness
58
who is at risk for developing acute necrotizing endocarditis caused by staphylococcus aureus?
an IV drug abuser using dirty needles
59
what valve is the first to be infected/ most commonly affected by acute necrotizing endocarditis caused by staphylococcus aureus?
the tricuspid valve
60
what is one major problem that is associated with staphylococcus aureus?
these infections are increasingly resistant to multiple antibiotics
61
What are 3 examples of staphylococcus aureus toxin mediated diseases?
Gastroenteritis, scalded skin syndrome, and TSS
62
what happens when staphylococcus aureus contaminates food?
it creates a preformed enterotoxin
63
what does the preformed enterotoxin cause?
12-24 hours of nausea, vomiting, diarrhea, and abdominal pain
64
what causes scalded skin syndrome (be specific)?
exfoliative toxin A and B
65
who is at higher risk of scalded skin syndrome (caused by staphylococcus aureus exfoliative toxin A and B)?
children and infants
66
What foods are at risk of being contaminated with staphylococcus aureus?
foods that are not cooked after handling, such as sandwiches, sliced meats, puddings and pastries
67
What can be seen in patients with scalded skin syndrome before the skin manifestations occur?
fever, irritability, and poor feeding
68
What causes TSS (be specific)?
the TSST-1 toxin (this is a superantigen)
69
what does the TSST-1 toxin cause the release of?
TNF and IL-1
70
what are the signs/ symptoms/ clinical presentations of TSS? (3)
1) gastroenteritis symptoms (fever, nausea, vomiting, watery diarrhea) 2) diffuse rash (involves the palms and soles) 3) shock, hypotension, and death
71
Where could staphylococcus epidermidis be found normally?
it is normal skin flora
72
what is the key virulence factor that staphylococcus epidermidis has?
the creation of a biofilm
73
what is a biofilm?
an extracellular polysaccharide matrix which adheres to the foreign device substrate and forms a scaffold in which the organism exists
74
What types of infections do staphylococcus epidermidis cause? (1 general term and 2 big examples)
nosocomial infections: prosthetic components (like heart valves) and catheters
75
after penetration through the skin, what happens to staphylococcus epidermidis?
it finds its way into the blood stream where it can cause a subacute endocarditis
76
what is the difference between the endocarditis that is caused by staphylococcus aureus and the endocarditis that is caused by staphylococcus epidermidis?
unlike the endocarditis seen with staphylococcus aureus, which is a necrotizing endocarditis with a high fever, staphylococcus epidermidis subacute endocarditis presents with a low grade fever
77
why are multiple positive blood cultures for staphylococcus epidermidis typically necessary to prove infection?
since it is frequently an incidental contaminating organism to a standard blood culture
78
What does staphylococcus saprophyticus cause?
it is a common cause of community acquired urinary tract infections
79
Who is more at risk for a urinary tract infection caused by staphylococcus saprophyticus?
sexually active young women "honeymoon cystitis"
80
How can the streptococci be further organized?
based on their colony growth pattern on standard blood agar plate--> beta hemolytic, alpha hemolytic, and gamma hemolytic
81
what is beta hemolytic?
complete hemolysis
82
what is alpha hemolytic?
partial hemolysis
83
what is gamma hemolytic?
no hemolysis
84
how do alpha-hemolytic species appear?
the surrounding colony appears green to the partial breakdown
85
once we have group the beta-hemolytic organisms together, how can they further be organized/ separated?
based on their sensitivity to bacitracin
86
what are the 2 broad groups of beta-hemolytic streptococcus organisms?
streptococcus pyogenes and streptococcus agalactiae
87
What are the 2 broad groups of alpha hemolytic streptococcus organisms?
streptococcus pneumoniae and viridans strep
88
what are the 2 broad groups of gamma-hemolytic streptococcus organisms?
enterococci and nonenterococcus
89
What is another name for the streptococcus pyogenes group?
group A streptococcus
90
what is the most common disease caused by streptococcus pyogenes?
streptococcal pharyngitis
91
How does strep throat present?
with an exudative white purulent infection of the palatine tonsils; high fever and lymphadenopathy can occur
92
what are the virulence factors associated with streptococcus pyogenes? (2)
****M protein**** and streptolysins
93
what is the effect of the virulent factor M protein?
it inhibits activation of complement
94
what is the effect of the virulent factor streptolysins?
they destroy RBCs (beta-hemolytic)
95
why is it important to adequately treat a streptococcus pyogenes infection?
subsequent immune response can lead to rheumatic fever or post-strep glomerulonephritis
96
besides streptococcal pharyngitis, what other diseases can streptococcus pyogenes cause? (7)
scarlet fever, erysipelas, necrotizing faciitis, impetigo, cellulitis, rheumatic fever, and post-strep glomerulonephritis
97
what specifically causes scarlet fever?
the pyrogenic (erythrogenic) exotoxin of streptococcus pyogenes
98
how does scarlet fever present?
fever, an erythematous rough "sandpaper" rash on trunk and neck (spares the face), an erythematous "strawberry" tongue
99
Who is most susceptible to getting scarlet fever caused by streptococcus pyogenes?
school aged children
100
scarlet fever typically occurs in association with what?
pharyngitis
101
how does erysipelas caused by streptococcus pyogens present?
as a sunburn like appearance often involving the face, warm to the touch, sharp demarcation
102
what does erysipelas infection involve?
the upper dermis and superficial lymphatics
103
what is the peak incidence of erysipelas caused by streptococcus pyogenes?
age 60-80
104
how does necrotizing fasciitis present?
as a purplish discoloration which is very painful; rapidly progressive
105
streptococcus pyogens can cause many of the same infections as staphylococcus aureus including what? (2)
impetigo and cellulitis
106
what is rheumatic fever?
a multisystem inflammatory disorder following group A streptococcus pharyngitis
107
what causes rheumatic fever?
antibodies and CD4+ T cell reaction against M streptococcal antigen following streptococcal pharyngitis
108
what are 6 common signs and symptoms of acute rheumatic fever?
1) fever (101 or above), 2) migratory polyarthritis (large joints) 3) pancarditis (pericarditis, mitral valvulitis) 4) subcutaneous nodules 5) erythema marginatum 6) Sydenham chorea
109
what is erythema marginatum?
curved, ring shaped macular rash
110
what is syndham chorea?
hopping, halting, gait, asymmetric jerking, grimacing
111
what causes post-streptococcal glomerulonephritis?
it is immune complex mediated--> antibody-antigen complex (strep antigen), deposit in the glomerular basement membrane; it is caused by group A streptococcus pharyngitis or skin infection
112
who is at risk for post-strep glomerulonephritis and how does it present?
children; edema, hypertension, hematuria, and proteinuria
113
how can acute rheumatic fever and post-strep glomerulonephritis be diagnosed?
with detection of certain post streptococcal antibodies in the proper clinical context- namely detection of antibodies to streptolysin O and DNAse B
114
Where does streptococcus agalactiae colonize?
vagina
115
what can streptococcus agalactiae result in?
neonatal meningitis, PNA, and sepsis; maternal sepsis can also occur
116
when does antepartum screening for streptococcus agalactiae occur?
during pregnancy during 3rd trimester (36-37 weeks)
117
what is the number one cause of neonatal meningitis?
streptococcus agalactiae
