Micro 1 Flashcards
0
Q
What organisms naturally colonize the large intestine?
A
Anaerobes - bacteroides (10^11 /g fecal mater)
1
Q
What organisms naturally colonize the skin?
A
Yeast and gram + organisms
2
Q
What organisms naturally colonize the mouth?
A
anaerobes - density sim to lg. intestine
3
Q
What organisms colonize the nose and pharynx?
A
Gram + and - cocci (Neisseriae and Moraxella)
Gram + rods (Corynebacterium)
The rest of the respiratory tract is sterile
4
Q
What organisms normally colonize the urogenital tract?
A
Urethra - transiently colonized
Vagina - changes w/ age: gram + cocci (staph, strep) before puberty; Lactobacillus Acidophilus after puberty (reduces pH and maintains uniform flora)
5
Q
What is the procedure for gram staining?
A
Heat fix Crystal Violet - then rinse Iodine - then rinse Acetone or Isopropyl alcohol - then rinse Safranin - rinse then dry
6
Q
What is the mechanism of Gram staining?
A
Iodine - crystal violet complex is too large to wash out of gram +
7
Q
Describe acid fast bacteria
A
Mycobacterium (TB)
Cell walls contain long chain fatty (mycolic) acids, do not gram stain well.
Stain w/ carbol fuchsin, decolorize w/ 3% HCl and ETOH - acid fast will remain red
8
Q
What is lipoteichoic acid and where is it found?
A
Part of gram + cell wall - strengthens
Endotoxin - can evoke immune response from humans
9
Q
Where are gram - toxins housed?
A
Periplasmic space - between inner cell membrane and peptidoglycan cell wall
ex: cholera toxin
10
Q
Cell wall components
A
Disaccharide-pentapeptide subunits
N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
Peptide bridges between NAM cross link subunits (determine thickness of wall)
Gram +: pentaglycine links D-ala and lysine
Gram -: direct link between D-ala and diaminopimelic acid
11
Q
What is mycolic acid?
A
Component of Acid Fast Bacteria cell wall
resistant to phagocyte killing and drying
12
Q
What are components of gram - outer membrane?
A
Lipopolysaccharides (LPS) and phospholipids
LPS: virulence factor (endotoxin), mediates inflammation, septic shock
LPS composed of
-O antigen: repeating sugars - used for typing bacteria
-core sugars
-fatty acid moieties - bioactive portion of LPS
13
Q
What is a bacterial capsule?
A
Both Gram + and - bacteria
High MW polysaccharides or amino acids
production depends on enviro and growth conditions
Virulence factor
Protection from complement mediated killing
14
Q
What are pili and what are they made of?
A
proteinaceous structures extending from cell membrane
made of pilin, tipped w/ adhesins which bind host tissue (receptors) - virulence factor- antigenic
1. common type: mediate adhesion to host eukaryotic cells
2. sex type: join conjugating bacteria
15
Q
What are flagella made of? Are they antigenic?
A
Flagellin
highly antigenic - H antigen
16
Q
3 spore forming bacteria and assoc. diseases
A
clostridium tetani - tetanus
bacillus anthracis - anthrax
clostridium botulinum - botulism
17
Q
How do Beta-Lactams work?
A
Inhibit final step of cell wall synthesis - transpeptidation by Penicillin Binding Proteins (PBPs)
18
Q
What is the mechanism of penicillinase resistance in resistant penicillins?
A
Bulky side chains - sterically hinder B-lactamase binding
19
Q
What coverage do beta-lactam / beta-lactamase inhibitor combo drugs offer?
A
Improved gram (-) and anaerobe MSSA
20
Q
What classes of bacteria are highly resistant to pecinillins?
A
aerobic gram - bacilli
anaerobes
21
Q
What are beta-lactamase inhibitors?
A
Suicide inhibitors
Bind beta-lactamase -> inactive compound
22
Q
What are common side-effects of Penicillin drugs?
A
Allergic reaction - from a rash to anaphylaxis
-may be due to B-lactam ring or to side chains
Acute Interstitial Nephritis - allergic rxn in kidney
- fever, rash, eosinophilia
- non-oliguric renal failure, may progress to anuria and kidney failure
- eosinophilic cells and tubular damage seen on biopsy
23
Q
Probenecid
A
Gout medication given to prolong effect of Penecillin - blocks renal elimination
Used for persistent infections - syphillis
24
What do cephalosporins NOT have activity against?
Enterococcus
25
What drugs would most likely be used to treat community acquired intra-abdominal infections or for surgical prophylaxis?
2nd gen cephalosporins - cephamycins
| Cefotetan or Cefoxitin
26
What is the drug of choice for community acquired pneumonia (s.pneumo)?
Cephtriaxone - 3rd gen cephalosporin
27
What are the SPICE organisms?
Serratia, Providencia, Indole (+) Proteus, Citrobacter, Enterobacter
- all have B-lactamase
- lab may say susceptible to 3rd gen Cephalosporin, but use may select resistant strain
- usually use cefepime or carbapenems
28
What cephalosporins have activity against anaerobic bacteria?
Cefotetan, Cefoxitin - 2nd gen (2B or GI) cephamycins
29
Ceftaroline
Advanced generation cephalosporin
Binds PBP2A and 2X
MRSA - first B-lactam w/ activity against.
Gram (-) activity between 2nd and 3rd gen
30
Cephalosporin / Penicillin cross-reactivity
Chance of those w/ penicillin allergy having allergy to cephalosporin
5-15% according to book, actually much lower (0-2%)
-may be due to lactam ring (unlikely) or side chains
--Ceftazadime and Aztreonam: identical side chains. Az billed as having no x-reactivity w/ Penicillins. If Cef allergic, probably Az allergic
31
What organisms are most commonly associated with ESBL?
ESBL - extended spectrum beta-lactamase
E.coli K.pneumoniae
Carbapenem is drug of choice
32
B-lactams and renal dosing
Almost all renally eliminated and need renal dosing adjustments
exceptions:
-Ceftriaxone
-Penicillinase resistant Penicillins
33
1st generation cephalosporins and what used for
Cephalexin, Cefazolin, Cefadroxil
Skin, lower UTI
Good gram +, Staph, MSSA, Strep (variable S.pneumoniae)
Bad gram -, no anaerobic activity
Not for use in neonates - bind Ca++ -> gallstones, biliary sludging
34
2nd Generation cephalosporins and what for
2A: Cephlacor, Cefuroxime - Respiratory infections
good gram(+), better S.pneumoniae,
2B: Cefotetan, Cefoxitin - cephamycins - GI infections *excellent for anaerobes*
community acquired intra-abdominal infections and surgical prophylaxis.
35
3rd generation cephalosporins and what used for
Ceftriaxone(IV), Cefotaxime, Cefixime, cefpodoxime(PO)
Ceftriaxone - *DOC for CAP*, *DOC for CAM* unless B-lactone resistant
Ceftazadime - Pseudomonas aeruginosa (PSA)
Excellent nosocomial gram(-)
Not great staph - quesionable MSSA
No PSA, no anaerobes
SPICE organisms - tendency to induce resistance
36
4th generation cephalosporins and what used for
```
Cefepime
Good gram (+): Strep, staph, MSSA
Good gram (-): excellent against nosocomial infections
SPICE organsism (Serratia, Providencia, indole (+) proteus, citrobacter, enterobacter)
```
37
Advanced generation cephalosporin and what used for
Ceftaroline
Binds PBP2A and PBP2X
MRSA coverage
better S.pneumoniae, ampicillin-sensitive E.faecalis
Gram(-) is between 2nd and 3rd gen. ability
38
What is ESBL and what are most common organisms encountered?
Extended Spectrum Beta-Lactamase
E.coli and K.pneumoniae - can be transferred to other enterobacteria
Renders resistance to all penicillins, cephalosporins and aztreonam
***Carbapenems are DOC*****
39
What are the carbapenems and what do they cover?
```
group 1: Ertapenem - DOC for ESBL organisms
good gram (+)
great gram (-) except APE: acinetobacter, PSA, enterobacter
```
group 2: Imipenem, Meropenem, Doripenem
good gram (+)
great gram (-): ESBL, PSA, A.Baumanii (decreasing effectiveness)
anaerobes: excellent, but no c.diff
**in general - used for multi-drug resistant organisms***
40
What do carbapenems not cover?
```
MRSA
ampicillin resistant enterobacteria
stenotrophomonasmaltophilia
KPC (carbapenemase)
C.diff (can cause c.diff)
```
41
What is the biggest side effect of carbapenems?
```
Seizures
Not likely, though.
Prob related to cilastatin (added to increase half-life)
More likely w/ high dose.
Cross-reactivity w/ penicillins 1-50%
```
42
Aztreonam
Used for empiric treatment of gram (-) organisms in patients w/ Penicillin allergy
PSA activity, but not great
No ESBL, no x-reactivity w/ penicillins
43
What drugs are useful against Acinetobacter baumannii?
DOC: ampicillin/sulbactam - given for sulbactam alone
| Imipenem, Meropenem, Doripenem - decreasing effectiveness
44
How do aminoglycosides work?
Bind 30s ribosomal subunit - inhibit protein synthesis
BacterioCIDAL, concentration dependent killing (high dose preferred)
Oxygen dependent transport - so no activity vs. anaerobes
Note: no oral absorption, high conc. in urine - good for UTI
45
What are the individual aminoglycosides and what are they used for?
Gentamycin: staph and enterococcus in comb. w/ B-lactam
-also eye ointment
Tobramycin / Amikacin: Empiric nosocomial (double coverage)
-sometimes definitive as well. Ami: mycobacterial
Neomycin: Oral - GI decontam pre-op. Topical - neosporin
Streptomycin: enterococcal infection when gentamycin resistant.
-mycobacterial infection
46
Mechanisms of aminoglycoside resistance
1. Addition of side chains by Transferase enzymes - prevent drug binding
2. 30s modification
3. Efflux pumps / decreased porin production -> decreased intracellular concentration
47
Aminoglycoside adverse events
Nephrotoxicity - most common. Minimize trough concentrations
Vestibular/ Ototoxicity - assoc. w/ total drug exposure (irreversible)
Neuromuscular Blockade - additive w/ other drugs (myasthenia gravis)
48
What are the floroquinalone drugs and what are they used for?
Moxifloxacin, Levofloxacin, Ciprofloxacin, Gemifloxacin and Norfloxacin
Respiratory: Levo and Moxi: Excellent against all CAP
PSA: Cipro and Levo: also enteric gram (-)
Anaerobes: Moxi (some B.fragilis activity)
49
Floroquinolone side effects
CNS toxicity: headache, dizziness, insomnia, seizures
Damage to growing cartilage: no use w/ peds
Dysglycemia
Cardiac arrhythmia / torsades (min risk unless prone to arr. or on QT prolonging drugs - Moxi highest risk
50
What drug interactions are floroquinalones prone to
Chelation effect: Reduced absorption when taken w/ divalent cations (Ca++, Mg++, Fe++)
51
What is Red Man Syndrome?
Histamine response to rapid infusion of vancomycin - not a true allergic reaction
non-specific mast cell degranulation
infusion should not exceed 1g/hr. pretreatment w/ diphenhydramine
52
What are the treatment options for VRE?
Linezolid
Daptomycin
Quinupristin / dalfopristin (E. faecium only)
Tigecyclin (other tetracyclines maybe)
53
What is the mechanism of Vancomycin resistance in Enterococci and Staph A?
D-ala D-ala becomes D-ala D-lac or D-ser
| Vancomycin can't bind
54
What is the "erm" gene?
Confers MLS resistance to S.aureus (Macroside, Lincosamide, Streptogramin)
- all 3 work at same ribosome site
If isolate says erythromycin resistant and clindamycin susceptible
D test to check for MLS before using clindamycin
55
How do you deal with yeast in the blood?
```
Confirm not at risk for Cryptococcus (immunosuppressed, HIV)
Is almost always Candida
-Albicans > Glabrata
Risk for fluconazole resistance?
-recent exposure or known colonizer of C.glabrata
Critically ill?
Yes -> Echinocandin
No -> Fluconazole
```
56
What mechanisms do microorganisms employ to avoid ciliary action of the respiratory system?
Development of strong adhesins
-Rhinovirus: capsid protein attaches to ICAM-1
-Mycoplasma pneumonia attaches to neuraminic acid on host respiratory epithelium
Paralysis of ciliary action
-Bordatella pertussis - tracheal cytotoxin
-Influenza virus -> ciliated cell disfunction
57
What organisms are most associated with skin infections?
S. aureus
| S. pyogenes
58
What is impetigo?
Skin infection commonly caused by S.aureus or S.pyogenes
More common in children
Intraepithelial vesicles w/ surrounding erythema - weeping yellow crusty lesions.
Patients irritable, uncomfortable, afebrile
S.pyogenes infections can lead to glomerulonephritis
59
What is Erysipelas?
Skin infection usually caused by Streptococcus pyogenes - involves epidermis and dermis
Bright red, inflamed w/ sharp borders, painful. Usually face and lower limbs. Patients often febrile
60
What is cellulitis?
Skin infection usually caused by S.aureus involving epidermis, dermis, and subcutaneous tissue
Patients often febrile, involved skin is edematous, erythmatous, warm, tender, and painful with bullae common. Ecchymosis
61
What is a carbuncle?
Multiple furuncles in a confined area forming a large confluent, suppurative infection.
Patients are often acutely ill and require surgery and systemic antibiotics
62
What organisms are involved in fasciitis and myonecrosis?
Strep pyogenes, Staph aureus, Vibrio vulnificus (if seawater exposure), Clostridia (gas gangrene)
63
What causes Scarlet Fever?
Strep pyogenes - primary infection in pharynx - sore throat
Streptococcal pyrogenic exotoxins produced
strawberry tongue, diffuse rough red rash, desquamation of skin on recovery
64
What is the cause of Toxic Shock Syndrome?
S. aureus produces TSST-1 (toxin) during infection on minor skin wound, female genital tract (tampon), post-influenza pneumonia.
Hematogenous spread of toxin -> very high fever, hypotension, multi-organ damage, diffuse erythmatous rash
65
What usually causes hot tub folliculitis?
Psuedomonas infect dilated pores in under-chlorinated hot tub.
66
What organism is associated with animal bites?
Pasturella multocida
| Penicillin works well.
67
What causes Whitlow?
Herpes symplex virus - finger infection assoc. with healthcare workers, esp. dentists.
68
What organism causes gangrene?
Clostridium spp
69
Cowdry Type A nuclear Inclusion - suggestive of what?
Herpes Symplex Virus - if seen in a cervical smear
or
Cytomegalovirus - if seen in respiratory cell
70
binucleate epithelial cells with perinuclear halo is suggestive of what?
papilloma virus
71
Staphylococcus virulence factors
alpha toxin: Complement like pore forming cytolysin - kills erythrocytes and leukocytes.
TSST-1: exotoxin. super-antigen cross-links Tcell receptor to MHC class II of host -> cytokine release.
Exfoliative toxins (scalded skin syndrome): intercellular splitting at desmosome
Exoproteins - allow spreading: hyaluronidase (hydrolyzes CT) staphylokinase (fibrinolysis)
Antiphagocytics: Protein A (binds Fc), Coagulase (surface polymerization of fibrin - resist phagocytosis), Catalase (resist H2O2)
72
What is quorum sensing?
Alteration of gene expression according to density of local cell population
Staph a.
- upreg. coagulase at low cell density - colonization
- upreg. staphylokinase at high density - spread
73
Scalded skin syndrome
Caused by staph a. exfoliative toxin in neonates and children.
Bullous impetigo is localized SSS
74
Staph aureus identification
```
gram + cocci in clusters
positive catalase (diff. from strep)
positive coagulase (diff staph epidermidis and staph saprophyticus)
```
75
Virulence factors of strep pyogenes
M protein: mediates binding to epidermis. anti-phagocytic. variable. cross-reactive Ab -> glomerulonephritis
Protein F: adhesin - mediates fibronectin binding at wound site
Streptolysins O and S - cause B- hemolysis on blood agar
SLO: oxygen labile, sulfhydryl activated cytolysin. Antibodies against -> self immunity
Streptococcal pyrogenic exotoxins (Spe A-C): Superantigens
-Spe A produced by bacteriophage carrying Grp. A Strep
-induce cytokine release -> fever, rash, Tcell stim, endotoxin sensitivity -TSST like
Hydrolytic enzymes - responsible for thin runny pus
streptokinase dissolves fibrin,
76
What is post-streptococcal glomerulonephritis?
Caused by cross-reaction with M-protein
-M-protein / Ab immune complexes deposit in glomerulus
Edema, hypertension, hematuria, proteinurina about 3 weeks post-infection
Rare in US. More in developing countries
77
What causes Toxic Shock-like syndrome?
Group A strep
Streptococcal pyrogenic exotoxin A is responsible - SUPERANTIGEN
Fever, hypotension, rash, renal impairment, respiratory failure, diarrhea
78
Streptococcus pyogenes identification
```
gram + cocci in chains
B-hemolytic on blood agar (SLO, SLS)
Pyogenic
Catalase negative
Lancefield group A antigen
```
79
What is propionibacterium?
Causes acne
predominant anaerobe of normal skin flora
breaks down lipids in sebum
Acne vulgaris - inflammation of hair follicle associated with sebaceous glands
keratin + sebum + bacteria -> blackhead
can cause infections in severely immunocompromised
endocarditis, contam prosthetic valves, cerebrospinal shunts
can contam blood cultures - must diff. from true pathogen
80
Pasteurella multocida
animal bite bacteria
| gram - rod
81
Clostridium perfringens
Gram + rod, anaerobic, spore producing
| gas gangrene
82
Clostridium Tetani
Gram + rod, spore producing, anaerobic
| Tetanus
83
What is indicated by chronic candidiasis
Tcell deficiency
84
Sporothrix shenckii
Causes sporotrichosis - subQ infection
| Fungal infection after thorn prick or gardening injury - causes pyogenic and granulomatous reaction
85
What are Dermatophytes?
Fungi that commonly infect skin -> tinea
-epidermophyton, trichophyton, microsporum
->ringworm, athlete's foot, jock itch
Invasion of nail bed -> malformed growth
86
What are the alphaherpesviruses?
HSV1,2 and Varicella-Zoster Virus
87
What are the betaherpesviruses?
Human Herpes Virus 6 (A and B),7 and Cytomegalovirus
88
What are the gammaherpesviruses?
Epstein-Barr Virus, Human Herpes Virus 8 (Karposi's Sarcoma assoc. Herpesvirus)
89
What is the structure of Herpes Symplex Virus?
```
Large encapsulated (icosahedral) DNA virus (dsDNA)
152k BPs, 70-80 genes
```
90
3 phases of viral gene expression
Immediate gene expression : adapt cell for virus replication
Early gene expression: vDNA replication
Late gene expresson: structural proteins
91
What do antiherpes virus drugs require for activation? What is method of action?
Phosphorylation by virus encoded thymodine kinase
acyclovir -> acyclovir monophosphate
cellular kinases -> acyclovir triphosphate -> inhibition of virus encoded DNA polymerase
- triphosphorylated drug embeds in viral DNA acting as chain terminators.
92
Where are latent VZV infections established?
Dorsal Root Ganglion
93
What cells are infected by beta herpesviruses?
HHV 6A and B: Tcell tropic. Also monocytes and macrophages
| Cytomegalovirus: myeloid cells.
94
Exanthm subitem
Roseola - common childhood infection
Caused by HHV 6B, sometimes 7.
Fever and rash on trunk and face spreading to legs.
Complications: fever >40C, neurological involvement - seizures, aseptic meningitis, hepatitis, mono-like symptoms
95
What disease is HHV 8 associated with?
Kaposi's sarcoma
| usually older men of mediterranean ancestry and HIV patients
96
Papillomavirus morphology
```
Non-enveloped icosahedral - small
circular dsDNA (8-10 genes)
```
97
HPV-16 transforming genes and major capsular protein
E6: p53 tumor suppressor protein destruction
E7: Inactivation of Rb tumor suppressor protein
L1 protein: major surface marker - target for antiviral Ab and component of Gardasil HPV vaccine
98
What HPV viruses are most closely associated with cervical cancer?
HPV 16 and 18
| -relatively uncommon
99
2 HPV vaccines and approved ages for admin.
Gardasil - age 9 - 26 (types 6,11, 16, 18)
| Cervarix - age 10-15 (types 16, 18)
100
Picornaviurs - description and example
Small, non-enveloped, single strand +RNA
Coxsackievirus: tends to occur in outbreaks
-hand, foot and mouth
-most common source of aseptic meningitis
101
What is coxsackie virus?
Picornavirus
Prone to occur in outbreaks - most common in infants and children
Hand food and mouth disease, aseptic meningitis
- fever, sore throat, headache, anorexia
- vomiting and convulsions - usually in children
- w/in 2 days - lesions of mouth, tonsils, soft palate
- healing in 1-5 days
faster resolution than HSV
102
Necotizing fasciitis is most commonly associated with what organism?
S.pyogenes
| also - CA-MRSA (does not respond to methacillin or cefazolin normally given for skin infections)
103
In presentation of scalded skin syndrome there is the presence of large vessicles or bullae. What organism is likely? What is less likely?
More likely: S.aureus
| Less likely: S. pyogenes
104
If a person develops blistering dermatitis after swimming in the ocean, what organism would be of concern?
Vibrio
- also assoc. w/ raw or undercooked oysters
- high mortality rate
105
What is the treatment for impetigo?
Topical abx (mupirocin) or oral abx
106
What is dermatitis/arthritis syndrome?
Dermatitic lesions with accompanying joint pain
- in sexually active young adult - Think Neisseria gonorrhoeae
- spreads through lymph and blood
107
What antibacterials are known for false elevation of creatinine, elevated INR (w/ warfarin), and hyperkalemia?
Sulfamethoxazole
Trimethoprim - hyperkalemia
SMX/TMP = Bactrim
108
How is Viridians Strep identified?
Blood culture
Gram +
Lacks lancefield group and any specific surface markers
Biochemical testing for definitive identification
109
How are Group D strep and enterococci clinically identified?
Blood culture
Gram +, catalase -
Serologic test for group D antigen
Enterococci grow in 6.5% NaCl, hydrolyze esculin in 40% bile
110
How is candida identified in the lab in the setting of a systemic or blood stream infection?
Blood culture
| KOH or Gram stain - budding round oval yeast cells w/ hyphae
111
How is aspergillus identified in the setting of a systemic or bloodstream infection?
Blood culture returned negative
Biopsy of infected tissue
Aspergillus cultured in lab - branched septate hyphae
112
Describe the plasmodium lifecycle
Anopheles mosquito bites host
Sporozoite -> blood -> Liver - form schizont - asexual reproduction -> merozoite -> blood
Merozoite enters RBC: Trophozoite -> schizont -> merozoite -> cell ruptures
Some cells for gametocytes -> mosquito for sexual reprod.
113
What is a hypnozoite?
Dormant form of Plasmodium
- P.vivax, P.ovale only
- responsible for long term relapses.
114
What are the erythrocyte receptors for P.vivax and P.falciparum?
P.vivax: Duffy receptor on reticulocyte
| P.falciparum: glycophorin A on all red cell types.
115
How is malarial fever induced?
Produced by asexual blood schizont. RBC ruptures -> release of:
-malarial metabolites, hemozoin (from hemoglobin): pyrogenic, antigenic,
-cytokines: IL-1, TNF
Fever is initially sporadic, then cyclical corresponding w/ parasitic replication cycles (48-72 hour bouts)
116
What is the effect of HbS on the spleen?
Person can become functionally asplenic -> increased susceptibility to encapsulated bacteria
117
What provides natural resistance to malaria?
Lack of Duffy receptor (P.vivax)
HbS heterozygous
HbC
- cells prevent parasite from rearranging actin to form adhesin -> decreased 'stickiness' of infected erythrocyte.
118
How are plasmodia organisms identified in clinical practice?
```
Blood smears
-thick smear: diagnose parasitemia
-thin smear: identify Plasmodia species
ELISA: Ab detection
gene probes, PCR for P.falciparum
```
119
How is Babesia microti spread?
Tick-bourne.
1-4 week incubation. Usually flu-like: Fever, myalgia, hepatosplenomegaly, hemolytic anemia,renal dysfunction
Spontaneous resolution in a few weeks.
Can be life threatening in asplenic patients.
120
What organism is the main cause of eye infections?
S. aureus
121
Infection of eyelid margin / sebaceous gland
Blepharitis
122
Inflamation of lacrimal sac
Dacrocystitis
123
Infection of aqueous or vitreous humor
Endophthalmitis
Requires ulceration or penetrating injury to compromise cornea and sclera
124
How is S.pneumoniae identified clinically?
Gram stain: gram +, lancet shaped diplococci
No Lancefield grouping
Capsular serotyping
Quelling reaction - anti-capsule Ab -> capsular swelling
Optochin (P disk) susceptibility
125
Hib vaccine
for Haemophilus influenzae b - most virulent strain
| -given to infants (@2 mos) since 1990
126
How is H.influenzae identified in a clinical setting?
Gram (-) rod - very small
Requires blood products for growth (grows on chocolate, but not blood agar)
Hematin (X factor) and/ or NAD (V factor) needed for growth
127
How does Pseudomonas aeruginosa Exotoxin A work?
ADP-ribosylation of Elongation Factor 2
NAD + EF2 ADPribose-EF2 (inactive) + nicotinamide + H+
**same activity as diphtheria toxin**
Inactivates protein synthesis - promotes tissue invasion and evasion of immune response.
128
What is the primary cause of corneal penetration in a Pseudomonal eye infection?
Elastase
| protease works on elastin, IgG, IgA, collagen, complement
129
How is pseudomonas identified in a clinical setting?
Gram - rod, motile on wet mount
Mostly aerobic, but facultative anaerobe
Fruity odor on solid media
Blue-green fluorescence under UV light (phyocyanin, pyoverdin)
High levels of cytochrome oxidase - pos. oxidase test
130
Trachoma
caused by Chlamydia trachomatis - chronic follicular conjunctivitis
Usually passed mother - child, mostly in less developed african/asian countries
Trichiasis - inward growth of eyelashes - corneal scraping
Recurrent infection, roughening of inner eyelid, can produce blindness
131
Diseases caused by Histoplasma capsulatum
Chorioretinitis - disseminated disease from primary respiratory infection
Presumed Ocular Histoplasmosis Syndrome - small areas of inflamation and scarring of retina - circular - if affects macula may produce blind spot
132
How is Histoplasma capsulatum identified?
Very slow growth on blood agar or Sabouraud agar from blood culture
Usually via biopsy- culture and identify bimorphic fungus
133
What is the drug of choice for Lyme disease?
Doxycycline
134
What valve of the heart is most frequently involved in endocarditis?
```
Mitral - L. side of heart: more pressure -> more turbulence
M - 28-45%
Aortic - 5-36%
M&A combined - 0-35%
Tricuspid - 0-6%
Pulmonic - <1%
```
135
What organisms are most frequently involved in bacterial endocarditis?
80% aerobic gram (+): S.viridians, S.aureus, enterococcus, etc.
20% unusual others: E.coli, yeast
136
What is mycotic aneurism?
Aneurysm due to infection - complication of infective endocarditis.
- occur at bifurcation points
- bacteria from IE - direct invation, embolic occlusion, or immune complex deposition
137
What are conjunctive petechiae?
Marker of acute endocarditis
| small pieces of vegetation break off - embolize in small vessels of conjunctiva
138
What are Osler's Nodes and Janeway's Lesions?
Both appear on hands and feet of individuals w/ infective endocarditis
Osler's: caused by immune complex deposition -> inflamation / necrosis. Painful.
Janeway: caused by septic emboli - microembolism - flat, necrotic, painless.
139
What abnormal lab results are associated with infective endocarditis?
Anemia - 70-90%
Thrombocytopenia - 5-15%
Leukocytosis - may be absent
Elevated sedimentation rate -almost always (70-90%)
140
How are blood cultures ordered in the setting of suspected infective endocarditis?
3 sets over the course of 24 hours - each a separate venopuncture
141
What is HACEK group endocarditis?
infective endocarditis caused by: Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominus, Eikinella corrodens, Kingella kingae
Sub-acute course. Fastidious - req. 2-3 weeks to grow.
If suspected, give lab special instructions - suppliment media and hold cultures longer
142
What is the most common cause of osteomyelitis?
S. Aureus
143
What is the preferred therapy for an animal bite? IV and PO
| What about penicillin allergic patient?
IV: ticarcillin / clavulanic acid
PO: Amoxicillin/clavulanic acid
Penicillin allergic: Doxycycline, Moxifloxacin
144
What is the treatment for bone/joint pseudomonal infection. How long?
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IV B-lactam, 4 weeks joint, 6 weeks bone
Use Aminoglycoside (G,T, A) or FQ (Cip, Lev) for 2 weeks
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