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Micro, Ass 4, Renee's Questions
I heart Renee
178
Microbiology
Graduate
08/21/2011

Additional Microbiology Flashcards

 


 

Cards

Term
1.     What are the 3 main species of Staphylocci that cause infections in humans?
Definition
1.     S. aureus, S. epidermidis, S. saprophyticus
Term
2.     What makes Staphylcocci so hardy?
Definition
2.     grow in many different media, resistant to drying out.
Term
3.     What are the results of a catalase test with Staph?
Definition
3.     Positive
Term
4.     Which Staph species is the only one that is coagulase positive?
Definition
4.     S. aureus
Term
5.     What makes a coagulase test positive?
Definition
5.     Coagulase is an enzyme bound to S. aureus that activates prothrombin, converting fibrinogen to fibrin, clotting the colonies and fibrin.
Term
6.     How is coagulase anti-phagocytic?
Definition
6.     Fibrinogen bound to bacteria masks them from phagocytes.
Term
7.     When you think of Pus-Filled Abscesses what pyogenic cocci should you think of?
Definition
7.     S. aureus
Term
8.     What is S. aureus’ favorite niche?
Definition
8.     anterior nares
Term
9.     What hemolysis class are S. aureus?
Definition
9.     β-hemolytic
Term
10.  A gram stain showing clusters of Gram+ organisms would be what organism?
Definition
10.  Staphylococci
Term
11.  Gram+, Catalase +, Coagulase Negative organism could be what?
Definition
11.  S. epidermidis or S. saprophyticus
Term
12.  What species of staph colonizes the GI tract and perineum?
Definition
12.  S. saprophyticus
Term
13.  What species of staph produces a polysaccharide capsule?
Definition
13.  S. aureus
Term
14.  What species of staph produces a very heavy capsule called slime?
Definition
14.  S. epidermidis
Term
15.  What type of test is very rapid with >95% sensitivity?
Definition
15.  Fluorescent 16S rRNA
Term
16.  Why do biofilms cause such a problem in treatment?
Definition
16.  Bacteria within biofilms are essentially dormant and tolerant to antibiotic-induced killing
Term
17.  Which species of Staph do biofilms cause the biggest problem? Why?
Definition
17.  S. epi; can cause IV infections and infections of prosthetic devices
Term
18.  How do capsules increase virulence?
Definition
18.  have anti-phagocytic effects
Term
19.  What is the acronym for the surface adhesins?
Definition
19.  MSCRAMM (microbial surface component reacting with adherence matrix molecules)
Term
20.  How do MSCRAMMs bind to cell walls?
Definition
20.  covalently bound by membrane bound enzyme called sortase
Term
21.  How does the enzyme, sortase, bind MSCRAMMs?
Definition
21.  cleaves an LPXTG motif at the C-terminus of the proteins (between T and G); attaches to un-crosslinked peptide cros bridge of the peptidoglycan layer.
Term
22.  What are some MSCRAMMs?
Definition
22.  protein A, clumping factors A and B (clfA, clfB), collagen-binding protein (can), fibronectin-binding protein B (fnbB)
Term
23.  What disease is caused by exfoliatin?
Definition
23.  Scalded skin syndrome
Term
24.  What is exfoliatin?
Definition
24.  epidermolytic exotoxin
Term
25.  How does exfoliatin cause blistering of the skin?
Definition
25.  toxins are dispersed and become localized in stratum granulosum, degrades desmoglein-1
Term
26.  How do Superantigens work?
Definition
26.  binds to both MHC-class II and the T cell receptor and activates up to 20% of the entire lymphocyte population
Term
27.  What do superantigens cause?
Definition
27.  massive secretion of cytokines, driving an overwhelming inflammatory response, endotoxin-like shock.
Term
28.  How many different superantigens can S. aureus express?
Definition
28.  15
Term
29.  What are the symptoms of Toxic Shock Syndrome?
Definition
29.  high fever, diffuse erythematous rash followed by desquamation
Term
30.  How is TSST-1 different than other SAgs?
Definition
30.  can cross the mucosal barrier and distribute throughout the body.
Term
31.  What is the main causes of food poisoning?
Definition
31.  Enterotoxins
Term
32.  What is the difference between intoxication and infection?
Definition
32.  Live bacteria don’t have to be present to cause an intoxication
Term
33.  T/F Toxins can be eliminated by cooking.
Definition
33.  F – Toxins are heat stable and not denatured by cooking
Term
34.  How soon after ingestion does a food intoxication cause disease? How long does it usually last?
Definition
34.  2-6 hours; 6-12 hours
Term
35.  Is there Fever associated with food poisoning?
Definition
35.  NO
Term
36.  What does MRSA contain that makes it so resistant to antibiotics?
Definition
36.  Resistance island – staphylococcal chromosome cassette mec; mec encodes an unusual penicillin-binding protein
Term
37.  How do β-lactams kill bacteria?
Definition
37.  Analogs of D-ala-D-ala terminus of the peptide crossbridges, inhibit cell wall formation by binding to the penicillin-binding proteins.
Term
38.  How does S. aureus resist penicillin?
Definition
38.  secrets penicillinase to hydrolyze penicillin
Term
39.  What is the mechanism of methicillin resistance?
Definition
39.  mecA gene encodes PBP2A with low affinity for all β-lactams.
Term
40.  Where can staph cause disease?
Definition
40.  Anywhere the blood goes.
Term
41.  What clinical syndrome caused mostly by S. aureus involves only epidermis with Red macula that evolve into blisters due to epidermolytic toxins?
Definition
41.  Impetigo
Term
42.  What is Folliculitis?
Definition
42.  Pyoderma that involves the hair follicle and immediate surroundings
Term
43.  If a patient has recurrent furuncles, what should they be tested for and why?
Definition
43.  nasal carriage of CA-MRSA; CA-MRSA is a frequent cause of furuncles that can progress to abscesses and cellulitis
Term
44.  What type of infection presents with fever, tachycardia, hypotension, dyspnea, and a new cardiac murmur?
Definition
44.  Infective Endocarditis
Term
45.  What are the main risk factors for Infective Endocarditis?
Definition
45.  IV drug use, being elderly with valve sclerosis, being a patient with intravascular prostheses, being on hemodialysis
Term
46.  Which type of Endocarditis is easier to treat?
Definition
46.  Right-side endocarditis
Term
47.  What is the percentage of hospital acquired pneumonia that is caused by S. aureus?
Definition
47.  20-30%
Term
48.  What is the leading cause of Osteomyelitis?
Definition
48.  S. aureus
Term
49.  When you think of indwelling medical devices, biofilms, indolent infections, and drug resistance what comes to mind?
Definition
49.  CoagNS!!!
Term
50.  What is the most common cause of primary bacteremia? Why?
Definition
50.  S. epi; because its niche is the skin and we shove stuff through it all the time.
Term
51.  Compare the pathogenicity of S. aureus and S. epi.
Definition
51.  S. aureus; true human pathogen with enough virulence factors to cause infection in a health person
Term
52.  What type of adhesion does S. epi express?
Definition
52.  fibrinogen, fibronectin, collagen, vitronectin and elastin.
Term
53.  T/F Polysaccharide intercellular adhesion is a major part of S. epi and S. aureus biofilms.
Definition
53.  F – major part of S. epi, not S. aureus
Term
54.  What allows biofilms to detach and spread to other potential sites?
Definition
54.  Dispersal products – phenol-soluble modulins (PSMs)
Term
55.  What is PGA?
Definition

55.  Poly-gamma-DL-glutamic acid; antiphagocytic capsular material.

 

It is found in the capsules of S. epi species which allows them to colonize skin and mucosal surfaces.

Term
56.  What organisms make PGA?
Definition
56.  S. epi (facilitates colonization of and persistence on skin, makes sense why S. epi has it and S. a does not)
Term
57.  What types of bacteriocins does S. epi make?
Definition
57.  epidermin, Pep5 and epilancin
Term
58.  Infections in Cardiac Devices is mostly cause by which organisms?
Definition
58.  CoagNS, 50-60% or cases
Term
59.  Orthopedic prosthetic device infections can be classified as early, delayed, and late. Which type of organisms are associated with each classification?
Definition
59. Early: within 3 months – S. aureus Delayed: 3 months – 2 years –CoagNS Late: longer than 2 years – hematogenous inoculation of organisms form another source
Term
60.  A patient with a recent CF shunt placement and local signs of inflammation, nausea and vomiting most likely has an infection from what type of organism?
Definition
60.  CoagNS – S. Epi
Term
61.  Why is it hard to determine if S. epi is the culprit of an infection?
Definition
61.  inhabit human skin and mucous and are considered part of the normal microbiota in humans; very likely to show up in any sample.
Term
62.  How do Streptococci grow?
Definition
62.  in chains
Term
63.  What is the result of a catalase test on a streptococcal species?
Definition
63.  Negative
Term
64.  How are streptococci distinguished from Neisseria?
Definition
64.  Streptococci are Oxidase negative and Nisseria species are oxidase positive.
Term
65.  What Lancefield group is S. pyogenes?
Definition
65.  Group A
Term
66.  What is the most common bacterial cause of acute pharyngitis?
Definition
66.  S. pyogenes
Term
67.  T/F S. pyogenes is pyogenic
Definition
67.  T – Duh that’s practically it’s name
Term
68.  What type of hemolytic reaction does S. pyogenes have?
Definition
68.  β
Term
69.  What does it mean to be nutritionally fastidious?
Definition
69.  require specialized environments due to complex nutritional requirements
Term
70.  Why do the S. pyogenes colonies have a mucoid appearance?
Definition
70.  produce copious amounts of a hyaluronic acid capsule
Term
71.  Why is the S. pyo capsule a poor immunogen?
Definition
71.  because it is structurally identical to human HA
Term
72.  What is the major somatic virulence factor of S. pyogenes?
Definition
72.  M protein
Term
73.  What makes strains of S. pyogenes that are rich in M protein resistant to phagocytosis?
Definition
73.  inhibition of the alternate pathway for activating complement
Term
74.  How do M-related proteins cooperate in the antiphagocytosis effect?
Definition
74.  Bind IgG or IgA at the non-antigen-binding site.
Term
75.  What is a hemolysin?
Definition
75.  exotoxin produced by bacteria that cause lysis of red blood cells
Term
76.  What type of hemolysins does S. pyogenes produce?
Definition
76.  Streptolysin O (SLO) and SLS
Term
77.  Which hemolysin is labile in the presence of oxygen?
Definition
77.  Streptolysin O
Term
78.  How is SLO inhibited?
Definition
78.  reversibly inhibited by oxygen
Term
79.  What can be measured to indicate a recent Group A streptococcal infection?
Definition
79.  anti-SLO antibodies
Term
80.  Which Lancefield group is responsible for the majority of the bacterial pharyngitis?
Definition
80.  Group A
Term
81.  What is the drug of choice for S. pyogenes?
Definition
81.  penicillin
Term
82.  What type of skin infection is a superficial purulent pyoderma with weeping vesicles that form honey-colored crusts?
Definition
82.  Impetigo
Term
83.  What organisms primarily cause pyoderma impetigo?
Definition
83.  β-hemolytic streptococci and S. aureus
Term
84.  What is a type of streptococcal cellulitis?
Definition
84.  Erysipelas
Term
85.  What is the treatment for Necrotizing fasciitis?
Definition
85.  Debridement of tissue, broad spectrum antibiotics immediately, massive amounts of IV fluids, monitor cardiac out put closely
Term
86.  What are 2 forms of Nonsuppurative Poststreptococcal Sequelae?
Definition
86.  Acute Rheumatic Fever and Acute Glomerulonephritis
Term
87.  What are the guidelines for Diagnosis of Initial Attack of ARF, The Jones Criteria?
Definition
87.  Major Manifestations: Carditis
Polyarthritis
Chorea
Erythema marginatum (rash on trunk and limbs, charactaristic of ARF)
Term
88.  What are the Guidelines for Diagnosis of AGN?
Definition
88.  Major Manifestations: Edema
Hypertension
Hematuria
Proteinuria
Malaise, headache, backache
Term
89.  What is the Treatment for AGN?
Definition
89.  Benzathine penicillin
Term
90.  What is Group B Strep resistant to?
Definition
90.  Bacitracin
Term
91.  What is the major virulence factor for GBS?
Definition
91.  Capsule, Capsule, Capsule!
Term
92.  What binds with factor H to downregulate complement deposition?
Definition
92.  Surface β-protein (GBS?)
Term
93.  Why is GBS testing in pregnancy so important?
Definition
93.  GBS very harmful to neonate – septicemia, respiratory distress, meningitis
Term
94.  Which organism is present in dental plaque?
Definition

94.  Viridans Streptococci

Typically S. mutans

Term
95.  What is the hemolysis of Viridans Streptococci?
Definition
95.  α-hemolytic
Term
96.  What is an important cause of nosocomial infections?
Definition
96.  Enterococcus
Term
97.  How do you distinguish between Viridans Streptococci and pneumococci?
Definition
97.  Viridans resistant to optochin, pneumococci susceptible to optochin
Term
98.  How is pneumococci diagnosed?
Definition
98.  culture sputum, blood or CSF
Term
99.  What are the risk factors for Pneumonia?
Definition
99. viral infection
chronic pulmonary disease
splenic disorders
alcoholism
Term
100.        What are preventative measures against pneumococcal infections?
Definition
100. Pneumovax Prevnar13 Flu Vaccine!
Term
101.        What are the symptoms of Bacterial meningitis?
Definition
101.       Headache, fever, vomiting, photophobia, stiff neck, irritability, and varying degrees of neurologic dysfunction
Term
102.        What CSF findings are associated with meningitis?
Definition
102.       Large #PMNs, reduced glucose, elevated protein
Term
103.        What is the most common cause of bacterial meningitis in the US?
Definition
103.       Pneumococcus
Term
104.        What combination of drugs are often used in the treatment of bacterial meningitis?
Definition
104.       cephalosporin and vancomycin
Term
105.        How is Neisseria meningitides distinguished from other bacterial species we have discussed?
Definition
105.       Gram-negative, kidney bean-shaped, osidase-positive diplococcic
Term
106.        What type of Virulence Factors does N. meningitides have?
Definition
106.       Pili, LPS, Polysaccharide capsules
Term
107.        Where does N. meningitides reside in the body?
Definition
107.       nasopharynx
Term
108.        What populations are at risk of contracting bacterial meningitis?
Definition
108.       Children ages 2-18, Adults in crowded conditions, alcoholism
Term
109.        What organism is a small nonmotile gram-negative bacillus, that causes meningitis?
Definition
109.       Haemophilus influenza
Term
110.        What are the 3 main causes of otitis media in children?
Definition
110.
1. Strep pneumo
      2. H. influenza
      3. Moraxella
Term
111.        What treatment is used for otitis media?
Definition
111.       third generation cephalosporin with dexamethasone
Term
112.        Why is dexamethasone used?
Definition
112.       to control inflammation
Term
113.        How is Listeria monocytogenes usually contracted?
Definition
113.       foodborne
Term
114.        How long did I spend studying Micro?
Definition
114.       To long for only 8 questions on the exam.
Term
115. T/F: Penicillin is the drug of choice for treatment of a staphylococcal infection?
Definition
F
Virtually all strains of Staph carry bacterial plasmids encoding Beta-lactamases making them resistant to penicillin (therefore Pen is never the first choice)

Methicillins or 1st gen Cephalosporins are the first choice (assuming the strain is sensitive).
Term
116. MRSA
Definition

Methacillin-resistant Staph aureus

 

A major problem!

MRSA have a unique penicillin binding protein that makes them resistant to methicillins, penicillins, and cephalosporins.

 

For serious MRSA infections tx w IV vancomycin Daptomycin is also effective against MRSA and VRE (Vanc-R enterococci), depolarizes bacterial membranes.

Term
What type of infections is S. epidermis responsible for and how are these infections typically treated?
Definition
S. epi is the leading cause of mosocomial bacteremia (as a result of the use of IV catheters).

Is also the most common cause of prosthetic heart valve infections.

S. epi tends to be methicillin resistant which makes treatment difficult.
Vancomycin is typically used, sometimes in combination with rifampin or an aminoglycoside.
Term
116. How do you distinguish S. saphrophyticus from S. epi?
Definition
S. saprophytic us is resistant to Novobiocin while S. epi is sensitive.
Term
117. What is the most significant cause of CA-UTIs?
Definition
E. coli (by far)
but S. saphrophyticus (which is normal flora of the skin and periurethral areas) is the second leading cause of this infection.
Term
118. Cystitis
Definition
An infection of the bladder, typically caused by bacteria (in which case it is called a UTI)

Symptoms: suprapubic pain, dysuria, frequency/urgency of urination, PMN in urine, significant bacteruria.
Typically not accompanied by fever*

If these symptoms exist without significant bacteruria, pt should be tested for STIs.
Term
119. T/F: Sterptococcal species die in the presence of oxygen?
Definition
F. Strep species are aerotolerant, however, they are anaerobes.

Note that there is an exception to this (peptostreptococcus) which is a strict anaerobe important in wound infections. [will be discussed in the anaerobes lecture]
Term
120. Name an example of a Group A streptococcal agent.
Definition
S. pyogenes
Term
121. Name an example of a Group B streptococcal agent.
Definition
S. agalactiae
Term
122. Name examples of agents which are grouped into Lancefield Group D
Definition

Strep bovis,

Enterococcus faecalis,

Enterococcus faecium

Term
123. To which Lancefield group does S. pnumoniae belong?
Definition
None!
Strep pnumo is a non-typable alpha-hemolytic strep.
Term
124. Name examples of alpha hemolytic streptococcal species.
Definition
Strep pneumo
Viridans strep

Note that most group A and B members are beta hemolytic, many non-typable strains (such as step pneumo and viridans) are alpha hemolytic and many group D members are gamma hemolytic.
Term
125. Describe the polysaccride capsules of the following species:
S. pneumonia
S. pyogenes
S. mutans
Definition
S. pneumo (no group) has a capsule containing many different types of carbohydrates.

S. pyogenes (GAS): has a capsule containing a lot of Hyaluronic acid.

S. mutans capsule contains polydextrans that help it form dental plaques.
Term
126. What is Protein A? Where is it found and what does it do?
Definition

Protein A is a major component of the bacterial cell wall.

It is also sloughed off of some bacteria and can be anti-phagocytic.

 

In S. aureus protein A is a MSCRAMM. It is recgonized (along with clumping factors A and B) on the surface of S. aureus in Latex Aggulutination Tests.

 

Protein A binds to the Fc portion of IgG and prevents activation of complement (anti-phagocytic property).

Term
127. What two things are encoded for in the genomes of all G(+) bacteria?
Definition

1) MSCRAMMs

 

2) LPXTG Motif (a specific amino acid sequence that is cleaved by the enzyme sortase to attach the protien to uncrosslinked peptidoglycans to allow interaction with a host).

Term
130. What type of infection(s) are Chronic Granulomatous Dz pt succptible to and why?
Definition

Staphlococcal infections.

 

Granulomatous Dz pts do not make ROS used to kill many types of bacteria.

Staph species are catalase positive which means they are able to break down the minimal amounts of hydrogen peroxide in the phagcytes of these pts leaving their phagocytes helpless to fight infection.

 

Strep infections do not present a problem to these pt because Strep is catalase negative.

Term
131. What is another name for Coagulase?
Definition

Coagulase = Clumping Factor

 

A MSCRAMM found in S. aureus species.

Term
132. What is a Thermonuclease Test and what is it used to determine?
Definition

Thermonucleases are DNases.

 

They are present in S. aureus but not in other forms of staph.

Term
133. What are Panton-Valentine Leukocidins?
Definition

These leukocidis are capable of lysing PMNs and are found in most CA-MRSA.

These isolates cause particularily severe infections.

Term
134. Describe the differences in growth charactaristics on BAP between Coag+ and Coag- staph strains.
Definition

Both can grow on blood agar plates and both are beta-hemolytic.

 

S. aureus produces golden-colored colonies while CoagNS typically produce white colonies.

Term
135. Name some dz caused by Staphlococcal Exotoxins (ETs)
Definition

Stahplococcal Scalded Skin Syndrome (SSSS),

Staphlococcal Scarlet Fever (which is a generalized form of SSSS),

Bullous Impetigo (blisters)

Term
136. T/F TSS is caused by Staph only
Definition

F.

Can be caused by Staph or Strep superantigens.

Specifically those of Staph aureus and Strep pyogenes.

Term
137. Name some GAS MSCRAMMs
Definition

M protein is the most significant, although there are others (M-like protein, F1/2, Epa)

 

M protein is anti-phagocytic (either due to binding fibrinogen or C4b binding protien, either way inhbiting complement activation and thereby hindering phagocytosis).

 

M protein is implicated in the development of acute rheumatic fever.

 

anti-M abs are protective but there are multiple serotypes of M.

Term
138. Explain the role of fimbriae in S. pyogenes virulence.
Definition

Fimbriae are a key mechanism of virulance for many species.

 

In GAS, fimbriae are made up of M protein (a MSCRAMM) and Lipoteicholic Acids (LTA, pro-inflammatory adhesins).

Both of these components contribute to its virulence.

Term
139. What symptoms are streptococcal pyrogenic exotoxins (SPEs) responsible for?
Definition

The rash and fever associated with Scarlet Fever.

 

Streptococcal TSS

 

Necrotizing fasciitis pathogenesis.

 

Myositis

Term
140. What are SLO and SLS responsible for and what is the difference between them?
Definition

SLO and SLS (Streptolysin O and S) are hemolysins responsible for beta hemolysis on a blood agar plate.

 

SLO is oxygen labile while SLS is oxygen stabile.

 

SLO is used to dx ARF.

Term
141. How does S. pyogenes react to Bacitracin exposure?
Definition

S. pyogenes is Bacitracin Sensitive.

 

Bacitracin is used to distinguish Group A strep (BacitracinS) from Group B strep (Bacitracin R)

Term
142. What is most commonly the cause of a sore throat?
Definition

VIRUSES*

 

If it is bacterial it is likely to be GAS but it is most likely viral.

(if it is GAS, tx with PenV)

Term
143. What is Scarlet Fever? What causes it?
Definition

A dz caused by SPE+ (Strep pyogenic exotoxin) strains of S. pyogenes.

 

It is the toxin, rather than the strep itself which causes the symptoms (Strawbery tounge, red rash, sore throat, and fevers).

Term
144. What causes Necrotizing Fasciitis and Myositis?
Definition

Can be a mono or polymicrobial infection!

 

In either case GAS and/or S. pyogenes can be involved (as can other organisms).

 

 

Term
145. T/F ARF may follow a GAS skin infection
Definition

False.


GAS my follow strep throat but does not follow streptococcal skin infections.

Term
146. Acute glomeruloneprhitis
Definition

May follow either a streptococcal pharyngitis OR a skin infection (unlike ARF).

 

Associated with speficic M proteins which are siad to be nephritogenic.

 

An immune complex dz

Term
147. What is the key example we studied of GBS?
Definition

S. agalactiae (detectible by rapid group B carbohydrate latex agglutination test).


Beta-hemolytic, Bacitracin R, has multiple antiphagycitc cpasule types which contain sialic acid and are the major source of virulence for this GBS.


Normal flora of the GI and oropharynx but also colonize the vagina during pregnancy.

Term
148. Name a disease caused by GBS
Definition

 Neonatial sepsis

 

Mothers now screened.

E. coli and some G- enterics also imporant.

Causes septicemia, respiratory distress, early onset after birth.

Can lead to meningitis and respiratory disease.

 

GBS can aslo cause infections, septicemia and endocarditis in immunocomprimised adults.

 

Term
149. What are some of the defining charactaristics of Enterococcus species.
Definition

It is considered an "honorary strep"

G(+) cocci

 

All are Lancefield Group D (but some strep are also D)

 

Bile esculin +

Salt tolorant

Some resistance to heat (overall hardy)

 

Noraml folor of the skin, upper RT, GI and GU tracts.

 

Most dz caused by this group is by E. faecalis and E. faecium is the strain most frequently VancR (VRE)

Term
150. T/F Enterococcus infections can be treated with Cephalosporins.
Definition

False.

 

Enterococcus species are naturally resistant to Pen and to Cephalosporins with some strains being Vancomycin resistant (VRE).

 

Some of the world's most resistant bacteria are in this group!

Term
151. Name 3 dz caused by Lancefield Group D species.
Definition

1. Nosocomial Infections (ex: UTI, septicemia, wound infection; Enterococci commonly involved in all)

 

2. Subacute endocarditis (SBE), particularily involving the valves (Enterococci)

 

3. Bacteremia: occurs when the colonic mucoas is disurpted by a tumor and S. bovis gets into to blood.

Is indication for a colonoscopy (intestinal cancer).

Term
152. Vancomycin
Definition

A glycopeptide abx which inhbits crosslinking of NAM and NAG in PG cell wall formation.

 

Effective against G + species only.

 

Used to treat potentially debilitating/fatal Dz:

MethR Staph infections (though there are Vanc alternatives here),

Pneumococcal meningitis (empirical tx, bf sensitivity profiles get back from the lab),

C. difficile infections/psudomembranous enterocolitis (again, alternative options are avail.)

 

Always adjust tx when sensitivities are known.

 

Term
153. What are some organisms that are VancR
Definition

 

VRE: VancR Enterococcus, typically E. faecium

(the original VancR organism)

 

VRSA: VancR S. aureus

(aquired resistance from Enterococcal species).

Term
154. What drugs are used to tx VancR strain infections?
Definition

Linezolid is typically a first choice

 

Synercid (a combo quinupristin/daflopristin) + Streptogramns

[Inhibition of bacterial protein synthesis]

 

Daptomycin (lipoprotein that depoloarizes G+ bacterial cell walls causing bacterial cell death)

Term
155. What classifies a specieis as a member of the Viridans group?
Definition

Viridans are a group of streptococci that excludes S. pneumo.

 

Are non-typable by Lancefield groups.

Alpha-hemolytic

 

Normal flora in the oral/pharyngeal cavities.

Important opportunists (SBE, bacteremia)

 

Notable member of this group: S. mutans has a slimy capsule of sucrose which allows it to attach to teeth and cause dental carries.

Term
156. What causes dental carries?
Definition

S. mutans

 

Viridans group strep (alpha hemolytic)

Term
157. What is the most common cause of Subacute bacterial endocarditis (SBE)?
Definition
Viridans group strep.
Term

158. Streptococcus pneumoniae

Classification, identifying charactaristics, related illnesses.

Definition

Non-typable alpha hemolytic strep that is not (for some unknown reason) considered a part of the Viridans group.

Can be normal flora of the pharynx.

Lancet-shaped

Diplococci*

 

OptochinS

(used to identify it from other alpha-hemolytic strep species like S. viridans which are OptochinR)

Bile-soluble

(to distinguish from S. bovis and Enterococci which are not dissolved by bile).

 

Capsule of S. pneumo=major virulence factor

(Anti-phagocytic, basis of pnumo vaccines, detectible by rapid agglutination tests).

Term
159. What is pneumolysin and why is it important?
Definition

Pnumolysin is a key virulence factor of Strep pneumo.

 

Can lyse cells by binding to membrane cholesterol and forming a pore.

Term
160. How does S. pneumo cause dz?
Definition

S. pneumo establishes infection (in RT, lungs, meninges, blood) by escaping host natural and adaptive immune responses and inducing inflammation (has C-substance which binds to C-reactive protein, inducing the release of acute phase reactants=inflammation).

 

Ex: death from pneumonia is the result of an inflammatory response elading to excessive fluid accumulation in the lungs which causes suffocation.

Term

161. Pneumonia

Cause(s), charactaristics/symptoms, risk factors.

Definition

Leading cause of bacterial pneumonia is Strep pneumo.

 

Is most common in the elderly.

 

Presents with a shaking chill (single rigor), rusty sputum (productive cough), pleuritic pain, and fever.

CXR shows lobar consolodation (due to fluid accumulation).

 

Risk Factors: recent viral infection, chronic pulmonary dz, splenic disorders (SSA, DM, asplenia).

Term
162. How is pneumococcal pneumonia treated?
Definition

Variable resistance patterns make abx tx difficult.

Multiresistant Strep pneumo (MSRP) = problematic.

Sensitivies should be ordered for all isolates.

 

If sensitivity allows, tx with Pen or ceftriaxone (3rd gen cephalosporin).

 

In PenR strains, tx with a fluroquinone liek Levofloxacin (broad spectrum, high toxicity)

Term
164. What is the best thing one can do to prevent pneumococcal pneumonia?
Definition

Prevent inflenza via flu vaccine!

 

Viral illness predisposes to pneumonia!

Term
164. Other the pneumonia, what other illnesses can S. pneumo cause?
Definition

URI

(otitis media, sinusistis, conjunctivitis)

 

Septicemia

 

Meningitis

(S. pneumo is the leading cause of bacterial meningitis in adults)

Term
165. What are the causes and symptoms of bacterial meningitis?
Definition

Causes: First weeks of life (GBS)

3 mo-18 yrs (Neisseria meningitis)

18-50+yrs (S. pneumo)

*Haemophilus, Listeria, E. coli are also causes.

 

Symptoms:Stiff neck, Headache, photophobia, fever, vomiting, neuro dysfunction.

 

CSF Findings: High opening pressure, large numbers of PMNs*, elevated protien levels.

 

If bacterial meningitis is suspected a combination of Cephalosporin and Vancomycin is often used (tx S. pneumo-caused meningitis).

Term
166. T/F, one can be vaccinated against pneumonia?
Definition

True

 

Pneumovax is a non-conjugated vaccine for older people and those at high risk due to AIDS, asplenia, transplant.

Not effective in kids.

Protects against invasive pneumococcal dz.

 

Prevnar is a new, expensive but safe, conjugated vaccine effective in children as young as 2 mo, creates a memory response.

Term

167. Nisseria meningitidis

Qualities/identifying charactaristcs and related dz.

Definition

G(-) *unique in this assessment material

Kidney-bean shaped

Diplococcal

Oxidase positive.

 

The most common cause of bacterial menigitis in children (3 mo-18 yrs); can have very rapid dz progression leading to death.

Also a cause of bacteremia (Meningococcemia)

Throat (normal flora) → Blood → Meninges

 

Virulence Factors: Pili, LPS, polysaccride capsule (distinguishes N. mengitidis from N. gonorrheae)

*Capsule is the basis for detection by rapid agglutination and for vaccine formulations.

 

Risk Factors:Crowded populations and alcoholism, endemic in some areas.

 

While rapid tx is vital, resistance is not a huge problem with N. meningitidis infections.

 

Term
168. A maculopaplar to petechial or pupuric skin rash (with fever, headache and neuro signs) indicates what type of infection?
Definition

Meningococcemia

(bacteremia caused by N. meningitidis)

 

Is more rare than bacterial meningitis caused by N. meningitidis.

 

While prompt tx is vital, resistance is not a huge problem with N. meningitidis.

Term
169. T/F one can receive prophylaxis for N. meningitidis infections.
Definition

True

 

Ciprofloacin (floroquinalone abx which inhbits DNA synth) is given to those at high risk: colse contacts, medical personal etc...

Term

170. Haemophilis influenzae (H. flu)

Identifying charactaristcs, related dz and prevention

Definition

 G- rod *unique in this assessment

Non-motile

Does not grow on BAP

(distinguishes from Strep/staph/enterococcus)

Does grow on Chocolate Agar Plate

(CAP, contains grwoth requirements for fussy bacteria)

 

Since the vaccine, the incidence of H. flu caused bacterial meningitis has plumeted (only now occurs in partially/unvaccinated infants).

 

Unencapsulated H. flu is a huge cause of otitis media in children (2nd behind S. pneumo)

Type b (the invasive type) has a capsule which allows it to cause severe systemic dz: meningitis, epiglottitis, cellulitis, osteomyelitis, pneumonia.

 

Tx: Ceftriaxone typically used to tx H. flu infections

AmpR is common.

 

Prevention: There is an effective conjugated type b vaccine that is part of standard vaccination series.

 

 

 

Term

171. Listeria monocytogenes

Identifying charactaristics, sources of infection, and related dz.

Definition

G(+)

Club-shaped Rod

Motile over a ltd. temp range.

 

A facultative intracellular parasite that infects mucoasl epi cells and non-immune macropahges.

 

Sources: The environment (animals); human infection is typically food-borne (unpasturized cheeses, hot dogs, deli meat).

 

Dz: Uncommon but serious food-borne illness with req hospitalization and high mortality.

Infections are flu-like in normal adults and more prevalent in pregnant women.

Can also cause bacteremia, meningitis in the immunocomrimised and neonates.

Term

172. An otherwise healthy 18 yo girl presents to the ED with a headache, altered mental status, neck stiffness and a high fever.

What are the first two things you do?

Definition

You suspect bacterial meningitis.

 

1) Take blood/CSF cultures (send off for succeptibilites)

 

2) Treat empirically

Cephtriaxone (broad spec abx, 3rd gen Cephalosporin)

+ Ampicillin (if listeria is suspected)

or + Vanc (if R S. pneumo is common in your area).

Term
173. What are some causes of actue pharyngitis
Definition

Bacterial: GAS, N. gonorrhoeae

 

Many viral causes incl Rhinovirus/Coronovirus (common cold viruses) and Adnenovirus.

Term
174. Name some agents of acute bronchitis (uncomplicated)
Definition

90% is caused by viruses and therefore should not be tx w/ Abx unless culture indicates.

 

Viruses: Coronavirus, Rhinovirus, adenovirus (URT)

Influenza (LRT)

 

Bacteria can cause more bronchitis in pt with underlying lung/respiratory problems*

S. pneumo, H. flu can cause in this case.

Term

175. Tx of S. pneumo infections causing:

Acute Otitis Media (AOM)

Pneumonia

Meningitis

 

Definition

AOM: Amoxicillin

 

Pneumonia: Amoxicillin or PenG (if PenS)

High dose Pen or Cephtriaxone (if Pen intermediate)

Fluroquinilone [Linezolid or Synercid] (if PenR)

 

Meningitis: High dose PenG or Cephtriaxone (if PenS)

Vanc+Ceph (if PenR)

 

All S. pneumo are B-lactam resistant due to altered penicillin binding proteins (PBP) not due to beta lactamases*

 

All S. pneumo are VancS at this time.

Term
176. Bile esculin/High Salt medium
Definition

Used to tell Group B strep and Enterococci apart from other Strep strains and from one another.

 

GBS is the only type of strep that can grow in a high-salt medium.

 

Enterococcal species can not only grow on this media but can convert bile esculin to a black breakdown product (distinguishing it from GBS).

 

 

Term
177. What test is useful in distinguishing S. aureus from S. epidermis?
Definition

Thermonuclease Test

 

S. aurueus (but not other staph, incl. epidermis) produces a heat-resistant DNase (a thermonuclease).

 

Samples are boiled in blood broth culture and then inoculated on a thermonuclease plate.

 

If S. aureus was present in the original culture its thermonucleases will have survived the boiling and will turn the blue agar pink.

Term
178. What test is useful in distinguishing S. pneumo from S. viridans?
Definition

Bile Solubility

 

S. pneumo contain autolysins that are activated by bile salts. When bile salts are dropped onto a S. pneumo culture the entire culture will autolyse and disappear!

 

Viridans and other species will persist.

 

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