Infectious Disease Flashcards
1
Q
What is babesiosis?
A
- Ixodes tick born infection caused by Babesia microti
- Causes acute febrile illness, thrombocytopenia, hemolytic anemia (indirect hyperbilirubinemia, elevated lactate dehydrogenase, low haptoglobin) abnormal liver function tests and intraerythrocyte inclusions.
2
Q
What is the definite diagnosis for babesiosis?
A
- Giemsa-stained thin blood smear
- Intraerythrocyte inclusions of ringed shaped and maltese cross forms.
3
Q
Which patients are at increased risk for severe babesiosis?
A
- Splenectomy patients
- Manifests as acute respiratory distress syndrome
- Dyspnea, coarse crackles, bilateral infiltrates on chest x-ray.
4
Q
What is lyme disease?
A
- Ixodes tick born infection caused by Borrelia Bordoferi
5
Q
What is the best treatment for beta lactamase producing bacteroides?
A
A broad spectrum antibiotic such as a penicillin and a beta lactamase inhibitor (tazobactam, clavulanic acid and sulbactem) for diabetics
- Piperacillin and Tazobactam
- Can also use metronidazole, carbapenems and clindamycin for anaerobes
6
Q
What are transpetidases?
A
A form of penicillin binding protein that function to cross link peptidoglycan in the bacterial cell wall.
7
Q
What is the mechanism of action of penicillins and cephalosporins?
A
Irreversibly bind to penicillin binding proteins (such as transpeptidases) leading to cell wall instability and lysis.
8
Q
What is the mechanism of action of vancomycin?
A
- Bacteriostatic
- Binds terminal D-alanine residues of cell wall glycoproteins and prevents transpeptidases from forming cross links.
- Not susceptible to Beta-lactamases
9
Q
What is the mechanism of action of fluoroquinolones?
A
Interfere with DNA replication by binding to proteins such as DNA gyrase.
10
Q
Which antibiotics bind to ribosomal proteins?
A
Macrolides, ahminoglycosides and tetracyclines
11
Q
How can bacteria become resistant to cephalosporins?
A
- Change the structure of penicillin binding proteins that prevents cephalosporin binding
12
Q
How do bacteria become resistant to aminoglycosides?
A
- Methylation of the aminoglycoside-binding portion of the ribosome which inhibits the ability of amino glycoside to interfere with protein translation
13
Q
How do bacteria become resistant to vancomycin?
A
- Mutated peptidoglycan cell wall
- Impared influx / increased efflux
14
Q
How do bacteria become resistant to fluoroquinolones?
A
- Mutate their DNA gyrase
- Impared influx/ increased efflux
15
Q
What is the mechanism of action of aminoglycosides?
A
- Interfere with ribosomal 30s subunit causing the cell to misread messenger RNA and halting protein synthesis.
16
Q
What is the mechanism of action of protease inhibitors?
A
- Reversibly inhibit viral protease which is responsible for HIV polyprotein cleavage to form mature viral proteins.
- Never used as mono therapy
- Atazanavir, darunavir, indinavir, lopinavir and ritonavir
17
Q
What are the main side effects of protease inhibitors?
A
- Lipodystrophy
- Increased fat deposition in the back, abdomen and decreased adipose tissue on face, extremities and buttocks. - Hyperglycemia
- Due to increased insulin resistance - Inhibition of cytochrome p450
- Will increase serum levels of WEPT
18
Q
What is the most important side effect with acyclovir?
A
- Renal toxicity
19
Q
What are the main side effects with foscarnet?
A
- May cause nephrotoxicity and electrolyte disturbances
20
Q
Define febrile neutropenia and who is most susceptible?
A
- Fever with absolute neutrophil count < 500
- Commonly seen in patients with leukemia undergoing chemotherapy
- Patients are at increased risk for severe infection
21
Q
If a child presents with a fever and a sore throat and has never received any vaccines, what is the most likely pathogen?
A
- Corynebacteria diphtheriae
22
Q
What agar is C. diphtheriae best grown in?
A
- Cysteine-tellurite agar
- Will grow as black, iridescent colonies. - Loffler’s medium
- Will develop cytoplasmic metachromatic granules
- Must stain with aniline dye like methylene blue
23
Q
What do you see in a biopsy of Tuberculosis and which marker would you find?
A
- Caseating granulomas consist of large epithelioid macrophages with pale pink granular cytoplasm surrounding a central region of necrotic debris.
- CD 14 is the surface marker the monocyte-macrophage cell lineage.
24
Q
Properties of gram positives
A
- Minimum 40 layers of peptidoglycan wall
- More likely to have exotoxin (only 1 has endotoxin)
- Lipoteichoic acid is present
25
Properties of gram negatives
- One layer thin peptidoglycan wall
- More likely to have endotoxin (inside cell wall) LPS/LOS
- Contain periplasmic space (Beta-lactamase location)
- Contain outer membrane which is antigenic
26
Core antigen
- Outtermost portion of LPS
- Different for every gram negative family member
- The most variable
- Causes most inflammation (immune response)
27
O antigen
- Middle portion of the LPS
- Different for each gram negative family but the same for all members of that family
- All E.colis have the same, all klebsiellas have the same
28
Lipid A
- Innermost portion of the LPS, connects to outer membrane
- The same for every gram negative bacteria
- Lipid portion
- Responsible for toxicity of the endotoxin
- Such as DIC, stroke, renal failure, heart failure, etc.
- Lipid A induces TNF and IL-1; antigenic O polysaccharide component
29
Periplasmic space
- Space between the inner and outer membrane in gram negative bacteria
- Contains the thin peptidoglycan wall
30
What are early sepsis symptom signs?
- Increased cardiac output/HR
- Peripheral vasodilation
- Warm extremities
31
What are septic shock symptom signs?
- Hypotension
- Tachycardia
- Tachypnea
- Also markedly elevated or decreased body temperature
32
What are signs that sepsis is progressing?
- Stroke volume decreases
- Cardiac output decreases
- Distal hypoperfusion becomes evident
33
What are signs of advanced septic shock?
- Cool and clammy extremities
- Delayed capillary refill
- Altered mental status
- Decreased urine output
34
What mediates sepsis?
1. TNF-alpha is the most important
- It is produced by activated macrophages
2. IL-1
3. IL-6
35
What is the immune responses most important source of protection against influenza?
- Humoral response with antibodies directed against hemagglutinin
- Neutralize the virus by blocking its binding to host cells
- Obtained via prior infection or through vaccination of similar strain of virus
36
What is the mechanism of action of Zidovudine (AZT)?
- Nucleoside reverse transcriptase inhibitor
- It competitively binds to reverse transcriptase and is incorporated into the viral genome as a thymidine analog
- It has an azido group in place of a hydroxyl group normally found in the 3' end of thymidine
- A free 3' hydroxyl group (3'-OH) is required for new nucleotides to be added to replicating DNA
- Therefore the azido group prevents viral DNA chain elongation
37
Staphylococcus Epidermidis
- Gram positive cocci in clusters
- Novobiocin sensitive
- Catalase positive
- Urease positive
- Coagulase negative
- Found in normal skin flora, contaminates blood cultures
- Does not ferment mannitol
- Infects artificial or prosthetic devices such as hip implants and heart valves
- Infects IV catheters by producing adherent biofilms
- Most common cause of endocarditis infecting artificial heart valves
- Treat with vancomycin
38
Staphylococcus Saprophyticus
- Gram positive cocci in clusters
- Catalase positive
- Urease positive
- Coagulase negative
- Novobiocin resistant
- Normal flora of female genital tract and perineum
- 2nd most common cause of urinary tract infections in sexually active females
39
Enterococcus
- Gram positive cocci
- E. faecalis and E. feceum
- Grow in up to 6.5% NaCl
- Bile resistant
- UTIs, Endocarditis and Biliary Tree infections
- E. feceum is nosocomial infection resistant to almost all antibiotics including vancomycin
- Treat with Linezolid (IV) and Tigecycline
40
Coxsackievirus
- Picornavirus family
- Single stranded RNA, + sense, naked
Type A virus
- Hand, foot and mouth disease
- Red vesicular rash
- Can lead to aseptic meningitis
- More common in the summer
Type B Virus
- Causes dilated cardiomyopathy
- Devils grip (Bornholms/Pleurodynia)
- Characterized by sharp pain, unilateral and in the lower chest
Treatment is supportive care
41
Picornavirus family
- Single stranded, + sense, naked, RNA virus
- Transmitted via fecal oral route, except rhinovirus
- RNA is transmitted to long protein which is cleaved to active viral protein subunit
- Replicates in the cytoplasm (like mRNA)
Includes the following viruses:
- Hepatitis A
> Hepatosplenomegaly
- Enteroviruses (polio, cocksackie, echovirus)
> Can lead to aseptic meningitis in kids
> Spinal tap shows normal glucose, no organisms, increased protein
- Rhinovirus
> The common cold, transmitted via respiratory droplets
42
Rhinovirus
- Picornavirus
- Single stranded, RNA, + sense, naked virus
- Acid labile, can not go through GI tract
- Transmited via respiratory tract / fomites
- Attaches to ICAM-1 entering host csells
- Grows best at 33 degrees an likes the upper respiratory tract
- Causes URI
- There are 113 serotypes
- Treatment is supportive
43
Flavivirus Family
- RNA, + sense, single stranded, enveloped, non-segmented viruses
Includes the following viruses
1. Dengue
- Carried by Aedes Egyptei mosquitos
- Causes break bone fever, thrombocytopenia, hemorrhagic fever and can lead to renal failure
- Treat supportively
2. Yellow fever
- Caused by Aedes Egyptei mosquitos
- Jaundice, back ache, bloody vomit/diarrhea
- There is a live attenuated vaccine for travelers
3. West nile virus
- Birds are a reservoir
- Caused by Coolers mosquito
- Causes encephalitis, myelitis, flaccid paralysis, meningitis, seizure and coma
4. Hepatitis C
- Hepatitis
5. St louis encephalitis
6. Zikavirus
Treat all supportively
44
Calicivirus (AKA Norwalk or Norovirus)
- Single stranded, RNA, + sense, naked virus
- Common on cruise ships, day cares and schools
- Transmitted via consumption of shellfish
- Can also be transmitted in buffets
- Causes viral gastroenteritis
- Explosive diarrhea
- Treat supportively
45
Adenovirus
- Double stranded, naked DNA virus
- Most common cause of tonsillitis and infection of the adenoids
- Transmitted via respiratory droplets and fecal oral route
- Affects children in day cares and soldiers in closed quarters
- Common in public swimming pools
- May cause hemorrhagic cystitis and viral conjunctivitis.
- Live attenuated vaccine available for military recruits
46
Coronavirus
- Single-stranded, RNA, + sense, enveloped, helical virus
- Causes the common cold, SARS and MERS
- Acute bronchitis that may lead to ARDS
- Virus replicates in the cytoplasm
- Can diagnose with PCR or antibodies to SARS
- Treat with broad spectrum antibiotics, ribavirin or corticosteroids
47
Hepatitis A
- Picornavirus
- Single stranded, RNA, + sense, naked virus
- Causes hepatitis
- Acid stable, survives the GI tract
- Transmited via fecal oral route
- Prevent infection from water by chlorination, bleaching, UV irradiation or boiling to 85 degrees for 1 minute
- Can be transmitted via shellfish in contaminated water
- Symptoms include fever, hepatosplenomegaly and jaundice
- Kids may be anecteric and show no symptoms
- Illness lasts 1 month
- Self limiting
- No carrier or chronic state
- Inactivated vaccine for travelers, chronic liver diseased patients and gay men
48
Poliovirus
- Picornavirus
- Single-stranded, RNA, + sense, naked virus
- Acid stable, survives the GI tract
- Replicates in peters patches of the submucosa gut lymph tissue (2-3 weeks)
- Affects anterior horn of the spinal cord
- Causes asymmetric paralysis, respiratory insufficiency and aseptic meningitis
- No treatment
- Salk vaccine (killed) for children (IPV) leads to IgG Ab
- Sabin vaccine (live) not used in the US leads to IgG and IgA Ab
49
Togavirus family
- Single-stranded, RNA, + sense, enveloped virus
Includes the following
1. Arbovirus
- Western, Easter and Venezuelan Equine Encephalitis
> All cause headache, fever and encephalitis
2. Rubella (German or 3 Day Measles)
- Postauricular/occipital lymphadenopathy
- Macular papular rash begins at head and spreads downward
- Virus spreads via respiratory droplets
- Causes serious congenital disease (TORCHs)
- Mental retardation, microcephaly, deafness, blindness, cataracts, jaundice, patent ductus arteriosus, pulmonic stenosis
- Blueberry muffin rash is hallmark
- In adults causes arthritis and arthralgia
- There is a live attenuated vaccine (MMR)
- Vaccine induces humoral/cell mediated immunity
- Do not give to pregnant women or immunosuppressed patients
- CD4 count must be over 100 to give to HIV patients
- Rubella is common in immigrants
50
Hepatitis C
- Flavivirus
- Single-stranded, RNA, + sense, enveloped virus
- Transmitted via blood to blood by:
> Blood transfusions before 1990
> Needle sticks or IV drug sharing
> Via sex, placenta and breast feeding
- Antigenic variability and variation
- Virion encoded RNA polymerase has no proofreading in 3'-5' exonuclease activity
- Causes hepatitis, jaundice, RUQ pain and increased liver enzymes
- 60-80% of infections progress to chronic state
- Lymphocytes infiltrate the portal tract, hepatocytes die, leading to fibrosis and cirrhosis
- Increases risk of hepatocellular carcinoma
- In the acute state, the ALT rises and then falls in 6 months
- Associated with cryoglobulins (IgM precipitates in the cold)
- Treatment is with ribavirin, IFN-alpha and protease inhibitors
51
Giardia Lamblia
- Intestinal flagellate that has two forms
- Trophozoite form is the pathogenic form that is pear shaped with flagella and 2 nuclei (owls eyes) - Diagnostic
- The cyst form is the infective form contain up to 4 nuclei
- Transmitted by fecal oral route or by drinking contaminated water (campers or traveling to endemic areas)
- Can be asymptomatic
- Symptoms include watery diarrhea, nausea, abdominal cramps, malabsorption, steatorrhea (foul smelling stools)
- May lead to malabsorption of vitamins A,D,E,K
- Diagnosed by stool microscopy for ova and parasites or immunoassays for Giardia antigens (ELISA)
- Bowel biopsy may show atrophic villi and crypt hyperplasia
- Treat with metronidazole
52
What is the immune mechanism against Giardia?
| Who is most susceptible to giardiasis?
CD4+ T helper cells and secretory IgA production
- IgA helps prevent and clear infection by binding to trophozoites and impairing their adherence to upper small-bowel mucosa
- Children with IgA deficiency, X-linked agammaglobulinemia and common variable immune deficiency can develop chronic giardiasis
53
Streptococcus Pneumoniae
- Alpha hemolytic
- Encapsulated with polysaccharide capsule
- Optochin sensitive
- Gram positive lancet shaped diplococci
- Bile soluble
- Number one cause of community acquired pneumonia
- Produces rust colored sputum
- MOPS (Meningitis, Otitis Media, Pneumonia, Sinusitis)
- IgA protease degrades IgA
- Patients with sickle cell disease are susceptible
- Treat with Macrolides (erythro), 3rd generation cephalosporins (ceftriaxone)
- 7 valent vaccine is conjugated to protein in children and induces IgG
- 23 valent adult vaccine
54
Streptococcus Viridans
- Gram positive
- Non capsulated
- Optochin resistant
- Bile insoluble
- Associated with dental carries
- Can lead to sub acute endocarditis in the mitral valve, usually with previously damaged valves
- Adheres to platelets via dextrans (extracellular polysaccharide)
- Treat with amoxicillin or vanco
55
Most common cause of transient bacteremia after dental procedures in healthy and diseased individuals? What can it lead to?
- Streptococcus Viridans
| - In patients with pre-existing valvular lesions can lead to endocarditis
56
Live attenuated oral (sabin) poliovirus vaccine
- Produces a stronger mucosal secretory IgA immune response than does the inactivated poliovirus (Salk) vaccine.
- Increase in IgA offers immune protection at the site of viral entry by inhibiting attachment to intestinal epithelial cells
57
Describe the Acid Fast Stain
- Identifies organisms that have mycolic acid present in their cell walls (Mycobacteriam and Nocardia)
- Aniline dye (carbolfuchsin) is applied to the smear
- Stains the bacteria red by binding to mycolic acids
- It is decolorized with hydrochloric acid and alcohol
- This dissolves the outter membrane of nontuberous bacteria but mycolic acid prevents decolorization of mycobacteria.
- Counterstain is applied (methylene blue) which is taken up by non-acid fast bacteria
58
What are the primary, secondary, latent and tertiary Syphilis manifestations?
```
Primary
- Painless genital ulcer (chancre)
Secondary
- Diffuse rash (palms and soles)
- Lymphadenopathy
- Condyloma lata
- Oral lesions
- Hepatitis
Latent
- Asymptomatic
Tertiary
- CNS (tabes dorsalis, dementia)
- Cardiovascular (aortic aneurysm/insufficiency)
- Cutaneous (gummas-masses)
```
59
What are the nontreponemal serologic tests?
1. Rapid plasma reagin (RPR)
2. VDRL
These tests mix a patients serum with a cardiolipin-cholesterol-lecithin antigen
- Aggregation or flocculation indicates the presence of anticardiolipin antibodies in patients serum
- Antibodies are due to release of lipids from cells damaged by T. pallidum
- These antibodies however are nonspecific
- Can also develop in TB and Lupus
- These require confirmation with treponemal serologic tests
60
What are the treponemal serologic tests?
1. Fluorescent Treponemal Antibody Absorption
2. Treponema Pallidum Enzyme Immunoassay
- These tests evaluate for antibodies directly against T. pallidum
- The patients serum is mixed with killed T. Pallidum to evaluate for antibody adherence using immunofluorescence
61
What is required for Hepatitis D to infect cells?
- Hepatitis B surface antigen must coat Hepatitis D antigen before it is able to infect hepatocytes.
- Once it is coated, Hepatitis D can survive within the cell, integrate into the host genome, replicate its viral RNA and translate its genome into protein
62
What are alpha hemolytic bacteria?
- Gram + cocci
- Partially reduce hemoglobin which causes greenish/brownish color without clearing around growth of colony on blood agar
Organisms
- Streptococcus pneumoniae (catalase -, optochin sensitive)
- Streptococcus Viridans (catalase - and optochin resistant)
63
What are Beta-hemolytic bacteria?
- Gram + cocci
- Complete lysis of RBCs, clear area surrounding colony growth on blood agar
Organisms
- Staphylococcus aureus (catalase and coagulase +)
- Streptococcus pyogenes - group a strep (catalase -, bacitracin sensitive)
- Streptococcus agalactiae - group B strep (catalase - and bacitracin resistant)
64
Staph are catalase positive or negative?
| Strep are catalase positive or negative?
- Staph are catalase positive
| - Strep are catalase negative
65
What does it mean to be catalase positive?
Which people are at risk for catalase + infections?
Which are the catalase positive organisms?
- Catalase degrades H2O2 into H20 and bubbles of 02
- Does not allow it to be converted to microbicidal products by the enzyme myeloperoxidase
- People with granulomatous disease (NADPH oxidase deficiency) are at risk for infections
- Staphylococcus
- Pseudomonas
- Nocardia
- E. coli
- Serratia
- B. Capacia
- H. pylori
- Listeria
- Aspergillus
- Candida
66
What does it mean top be urease positive?
What can it predispose people to?
What are the Urease positive organisms?
- To hydrolyze urea to release ammonia and CO2 in order to increase the pH
- Predisposes to struvite stones (ammonium magnesium phosphate), particularly by Proteus
- PCHUNKSS
- Proteus
- Cryptococcus
- H. pylori
- Ureaplasma
- Nocardia
- Klebsiella
- Staphylococcus Saprophyticus
- Staphylococcus Epidermidis
67
What toxin does Corynebacterium Diptheriae produce and what is its mechanism of action?
- Produces Diphtheria Toxin
| - Inactivates elongation factor 2 via ribosylation, thus inhibiting host cell protein synthesis
68
What toxin does Pseudomans Areguinosa produce and what is its mechanism of action?
- Produces Exotoxin A
| - Innactivates elongation factor 2 via ribosylation thus inhibiting host cell protein synthesis
69
What toxin does Staphylococcus Aureus produce and what is its mechanism of action?
- Enterotoxin and Toxic Shock Syndrome Toxin
- Enterotoxin is a superantigen that acts locally in the GI tract causing vomiting
- TSS toxin is a superantigen that stimulates T-cells leading to widespread cytokine release and shock
70
What toxin does Clostridium Difficile produce and what its its mechanism of action?
- It produces Cytotoxin B
- It induces actin depolymerization leading to mucosal cell death, necrosis of colonic mucosal surfaces & pseudomembrane formation
71
What toxin does Clostridium Botulinum produce and what is its mechanism of action?
- It produces botulinum toxin
| - It blocks the release of presynaptic acetylcholine at the neuromuscular junction resulting in flaccid paralysis
72
What toxin does Bordatella Pertussis produce and what is its mechanism of action?
- It produces pertussis toxin
- It disinhibits adenylate cyclase via Gi ADP ribosylation, increasing cAMP production in the host cell; causes increased histamine sensitivity & phagocyte disfunction
73
What toxin does Vibrio Cholerae produce and what is its mechanism of action?
- It produces Cholera toxin
- It activates adenylate cyclase via Gs ADP ribosylation , increasing cAMP production in the host cell; causes secretory diarrhea, dehydration and electrolyte imbalances
74
Rabies Virus
- Enveloped, single stranded, linear RNA bullet shaped virus with knob like glycoproteins that bind to nicotinic acetylcholine receptors
- Transmitted due to a bite wound from an infected animal
- The virus replicates locally in muscle tissue over several days or weeks before spreading
- It spreads in retrograde fashion through the peripheral nerve axons to the CNS via dynein motors
- Negri bodies (cytoplasmic inclussions) are seen on biopsy in purkinje cells of the cerebellum and hippocampal neurons
- Post exposure prophylaxis is wound cleaning plus immunization with killed vaccine and rabies immunoglobulin (passive active immunity)
- Fever, malaise, agitation, photophobia, hydrophobia, hypersalivation paralysis, coma and death
- Aerosol transmission in bat caves is also possible
75
What are they key features of viral or aseptic meningitis?
| What are the most common organisms?
1. CSF cell differential shows:
- WBC <500 cells/mm3
- Lymphocyte predominance
2. Glucose is normal or slightly reduced
3. Protein is < 150 mg/dL
4. No organisms identified
5. Most commom causes are:
- Enteroviruses (Coxasckievirus, echovirus, poliovirus)
- Arbovirus
- Herpes simplex type 2
6. Less severe than bacterial meningitis, focal neurologic signs, seizures and alterations in mental status are absent
76
What are the key features of bacterial meningitis?
| What are the most common causes?
1. CSF cell differential shows:
- WBC > 1000 cells/mm3
- Neutrophilic predominance
2. glucose levels are < 45 mg/dL
3. Protein is often >250 mg/dL
4. Organisms are present
5. Most common causes are:
- 0-6 months: Group B Strep and E. Coli
- 6 months- 6 Years: S. Pneumoniae, N. Meningitidis and H. Influenzae
- 6-60 Years: S. Pneumoniae and N. Meningitidis
- 60 Years +: S. Pneumoniae, Gram negative rods and Listeria
6. More severe than viral meningitis with focal neurologic signs, seizures and alterations in mental status
77
What is the most common causes of meningitis in HIV patients?
Cryptococcus Spp.
78
What two medications do you use to treat meningitis?
- Ceftriaxone and Vancomycin empirically
| - Add ampicillin if Listeria is suspected
79
What do lab findings show for fungal meningitis?
Opening pressure increased
- Lymphocytes increased
- Protein increased
- Glucose decreased
80
Urinary Tract Infections
- Symptoms
- Causes
- What can they lead to?
- Present with dysuria, frequency, urgency, suprapubic pain and WBCs in urine (no casts)
- In males, in infants caused by congenital defects or vesicoureteral reflux, in elderly caused by enlarged prostate
- In women, more common due to short urethra colonized by feccal flora
- Other predisposing factors are obstruction, kidney surgery, catheterization, GU malformation, diabetes and pregnancy
- Can lead to pyelonephritis, ascension to the kidney leading to fever, chills, flank pain, costovertebral angle tenderness, hematuria and WBC casts
81
What are the most common UTI bugs?
- E. Coli
- Proteus Mirabilis
- Klebsiella
- Staphylococcus Saprofiticus
- Enterococcus
- Serratia Marcescens
- Pseudomonas Areginosa
82
What is the leading cause of UTIs?
- E. coli
| - Colonies show green metallic sheen on EMB agar
83
What is the 2nd leading cause of E. coli?
- Staphylococcus Saprophyticus
| - In sexually active women
84
What is the 3rd leading cause of UTI?
- Klebsiella pneumoniae
| - Large mucoid capsule and viscous colonies
85
Which strain of bacteria that causes UTI's produces red pigment; is nosocomial and drug resistant?
- Serratia Marcescens
86
Which strain of bacteria that causes UTIs is nosocomial and drug resistant?
- Enterococcus
87
Which strain of bacteria that causes UTI's has motility that causes "swarming" on agar; urease positive and associated with struvite stones?
- Proteus Mirabilis
88
Which strain of bacteria that causes UTIs produces a blue green pigment and fruity odor; usually nosocomial and drug resistant?
- Pseudomonas Aeruginosa
89
Bacterial Vaginosis
- Signs
- Labs
- Treatment
```
Signs
- No inflammation
- Thin white discharge with fishy odor
Labs
- Clue cells
- pH >4.5
Treatment
-Metronidazole
```
90
Trichomonas Vaginalis
- Signs
- Labs
- Treatment
```
Signs
- Inflammation (strawberry cervix)
- Frothy yellow-green, foul smelling discharge
Labs
- Motile Trichomonads
- pH >4.5
Treatment
- Metronidazole
- All partners treated
```
91
Candida Vulvovaginitis
- Signs
- Labs
- Treatment
```
Signs
-Inflammation
- Thick white cottage cheese like discharge
Labs
- Pseudohyphae
- pH normal (4-4.5)
Treatment
- Azoles
Associated with
- Antibiotics, contraceptives, pregnancy, diabetes mellitus and HIV
```
92
Oral Thrush
- Occurs in denture wearers, diabetics, immunosuppressed patients and patients receiving steroids, antibiotics or chemotherapy.
- In a healthy individual, oral thrush may be suggestive of immunosuppression and may be due to HIV infection
- Presents with white patches on the oral mucosa (pseudomembranous candidiasis) that can be easily scraped off, revealing erythematous mucosal surface underneath.
- Microscopic examination of KOH-treated scrapings shows Candida yeast and pseudohyphae
93
Cutaneous candidiasis
- Occurs in areas exposed to heat and high humidity
| - Such as the groin and perianal area in infants
94
What are the echinocandin antifungals?
- MOA
- Uses
- Caspofungin and Micafungin
- They block glucan synthesis
- The fungal cell wall is made up of 1,3-beta-D-glucan
- Caspofungin is effective against Candida and Aspergillus
- Not effect against Cryptococcus
- Limited use on Mucor and Rhizopus
95
Amphoteracin B
- MOA
- Uses
- Side effects
```
MOA
- Polyene antifungal that binds ergosterol in fungal cell membrane
- Leads to pore formation that allows leakage of electrolytes and cell lysis.
Uses
1. Cryptococcus
2. Blastomyces
3. Coccidioides
4. Histoplasma
5. Candida
6. Mucor
Side effects
- Fever and chills
- Hypotension
- Nephrotoxicity (supplement K+ and Mg 2+)
- Arrhythmias
- Anemia
- IV phlebitis
Hydration decreases nephrotoxicity
```
96
Flucytosine
- MOA
- Uses
- Side effects
MOA
- Inhibits synthesis of both DNA replication and RNA protein synthesis in fungal cells
Uses
- Used as a synergistic agent with Amphoteracin B for cryptococcal meningitis
Side effects
- Bone marrow suppression
97
Griseofulvan
| - MOA
```
MOA
- Enters fungal cells
- Binds microtubules
- Inhibits mitosis
- Deposits in keratin tissues (nails)
Uses
- Effective against dermatophytes (tinea, ringworm) only as it accumulates in keratin containing tissues.
Side effects
- Teratogenic
- Carcinogenic
- Confusion
- Headaches
- Disulfiram-like reaction
- Increases cytochrome P-450 (WEPT)
```
98
Azoles
- MOA
- Uses
- Side effects
MOA
- Inhibit ergosterol synthesis (cell membrane) by inhibiting cytochrome P-450 enzyme (14-alpha dymethilase) which converts lanosterol to ergosterol
- Does not affect polysaccharides of fungal cell wall
Uses
- Local and less serious systemic mycoses
- Fluconazole for suppression of cryptococcal meningitis in AIDS patients and any candida infection
- Itraconazole for blastomyces, coccidiodes and Histoplasma
- Clotrimazole and miconazole for topical fungal infections
- Voriconazole for aspergillus and some candida infections
- Isavuconazole for serious aspergillus and mucorales infections
Side effects
- Testosterone synthesis inhibition
- Gynbecomastia especially with ketoconazole
- Inhibits cytochrome P-450 (liver dysfunction)
99
Terbinafine
- MOA
- Uses
- Side effects
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MOA
- Accumulates in the skin and nails
- Used to treat dermatophytosis
- It inhibits the fungal enzyme squalene epoxidase (preventing ergosterol synthesis)
- Results in decreased ergosterol synthesis
Uses
- Dermatophytoses (onychomycosis)
Side effects
- GI upset
- Headaches
- Hepatotoxicity
- Taste disturbance
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100
What medications are used to treat primary tuberculosis?
RIPE
- Rifampin
- Isoniazid
- Pyrazinamide
- Ethambutol
101
Which type of meningitis benefits from glucocorticoid treatment?
- Only pneumococcal meningitis
- Treatment with dexamethasone prior to antibiotic therapy has been shown to decrease risk of adverse outcomes (seizures, focal neurologic deficits and death)
102
Young male patient presents with dysuria and discharge, what is the most likely cause?
Neisseria Gonorrhea
103
What is diagnostic test for Gonorrhea?
- Nucleic Acid amplification testing (NAAT)
| - Urethral gram stain can also be obtained for diagnosis and antibiotic sensitivities
104
What is the treatment for N. Gonorrhea?
Dual therapy with ceftriaxone (third generation cephalosporin) and azithromycin (macrolide) to cover for resistance and against co-infection with chlamydia
105
What are the complications of untreated gonorrhea and chlamydia infections in males and females?
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Males
- Prostatitis and epididymitis
Females
- Pelvic inflammatory disease
It can also infect anus with anal intercourse, pharynx in oral sex and conjunctivae of neonates in infected mothers
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106
Middle aged man with malaise, cough x 2 months, yellow sputum with streaks of blood. He smokes 1 pack per day, abused alcohol with prior binge drinking episodes. He has poor dentition, dental caries, gingivitis, enlarged submandibular lymph nodes. Right lung consolidation with air bronchograms are seen. What is most likely diagnosis?
Actinomyces
107
What is the mechanism of action of zidovudine?
- It is a Nucleoside reverse transcriptase inhibitor used to treat HIV infection
- Competitively binds to reverse transcriptase and is incorporated into the viral genome as a thymidine analogue
- AZT does not have 3'-OH group making 3'-5' phosphodiester bond formation impossible
108
What are the signs of herpes virus encephalitis?
- Acute/Subacute changes in mental status, seizures, headache and in some cases focal neurological deficits
- CSF may show hemorrhagic lymphocytic pleocytosis, increased protein and normal glucose
- MRI masy show abnormal temporal lobes
109
What is the treatment for Herpes encephalitis and what is the mechanism of action?
- Acyclovir, a nucleoside analog
- Once activated, competes with deoxyguanosine triphosphate for viral DNA polymerase (inhibits it)
- When acyclovir triphosphate becomes incorporated into the replicating viral DNA chain, viral DNA synthesis is terminated
110
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What causes Leprosy?
What type of organism is it?
What does it infect?
What is the reservoir?
How is it diagnosed?
What is the treatment?
```
- Caused by Mycobacterium Leprae
- Acid fast bacillus, likes cool temperatures
- It infects the skin and superficial nerves
- Causes glove and stocking loss of sensation
- Can not be grown in vitro
- Reservoir in the US in armadillos
- Diagnosed via skin biopsy or tissue PCR
- Dapsone and rifampin for Tuberculoid form
- Clofazimine is added to lepromatous
111
What are the two types of leprosy?
| How are they treated?
Lepromatous
- Presents diffusely over the skin with leonine (lion-like) facies
- Is communicable
- Characterized by low cell-mediated immunity with a humoral Th2 response
- This type can be lethal
- Treated with dapsone, rifampin and clofazamine
Tuberculoid
- Limited to a few hypoesthetic, hairless skin plaques
- High cell mediated immunity with large TH1 type immune response
- Treated with dapsone and rifampin
112
What are the segmented viruses?
| What can they undergo?
Orthomyxoviruses
Reoviruses
Bunyaviruses
Arenaviruses
- They can undergo genetic shift through reassortment
- Similar to how influenza viruses reasorts human strain with animal strain
113
Host defense against candida is done via which two immune system components?
1. T lymphocytes (Th cells in particular)
- Prevent superficial candida (oral / esophageal / cutaneous / vulvovaginitis)
- Immunocompromised patients have low T cell counts
2. Neutrophils
- Prevent hematogenous spread of candida
- Disseminated candidiasis is more common in patients who are neutropenic, immunocompromised, or those with impaired phagocytosis.
114
Hypogammaglobulinemia predisposes patients to?
Bacterial infections
115
What is so special about the capsule of Bacillus Anthracis?
Antiphagocytic capsule
| - Contains D-glutamate instead of polysaccharide
116
Bacillus Anthracis
- Leads to pulmonary anthrax, also known as woolsorters disease
- Spores are very small, when inhaled, enter the alveoli and are ingested by macrophages
- From lung they move to mediastinal lymph nodes and cause hemorrhagic mediastinitus
- Once spores germinate into vegetative cells, they produce three part anthrax toxin
- Symptoms consist of myalgia, fever and malaise but rapidly progress to hemorrhagic mediastinitis, bloody pleural effucion and septic shock and death
117
Streptococcus Gallolyticus endocarditis and bacteremia is most commonly associated with?
Gastrointestinal lesions (colon cancer)
118
Entamoeba Histolytic
- Protozoa
- Cyst form is infectious
- Acquired from contaminated water
- Associated with men who have sex with men (anal oral transmission)
- Right lobe of liver is most commonly involved in amoebic liver accesses
- Presents as right upper quadrant pain
- Abcess is described as anchovy paste consistency
- Intestinal amebiasis can cause ulceration sin the colon and lead to blood in stool
- Diagnose with stool O&P
- Microscopy shows trophozoite with endocytosed red blood cells under the microscope
- Treatment is with metronidazole
- Paramycin is used as a luminal agent to rid of the cysts
- Iodoquinol is another luminal agent used to rid of the cysts
119
Cryptosporidium
- Unicellular protozoa, stains acid fast
- Causes severe diarrhea in HIV patients
- Infectious cysts are ingested
- Each cyst is composed of 4 motile sporozoites
- The sporozoites attach to the intestinal wall, they cause diarrhea and small intestine damage
- Treat with Nitazoxanide
- Filtration can remove oocyst from infected water
- Spiramycin (macrolide) may also be used for treatment
120
Toxoplasma Gondii
- Protozoa of the CNS
- Pregnant women are at risk for transmission (ToRCHeS)
- Can be transmitted via cat feces
- Oocytes are present in the feces
- Can be transmitted via cysts in undercooked meat
- Immunocompromised are at risk
- Causes brain abscess seen as ring enhancing lesions on CT or MRI
- Can lead to encephalitis
- Perform brain biopsy to differentiate from CNS lymphoma
- Congenital Toxoplasmosis presents with classic triad of intracranial calcifications, hydrocephalus or seizures and chorioretinitis
- Congenital toxoplasmosis can also lead to deafness
- Treat with Sulfadiazine
- Begin prophylaxis treatment when CD4 count is < 100 and seropositive for IgG for Toxo
- Prophylaxis is with SMX/TMP
121
Trypanosome Brucei
- Tsetse fly is the vector
- Puts victims in a coma
- Causes cervical and axillary lymphadenopathy
- Leads to recurrent fevers
- Tripomastigotes seen in the blood smere
- Parasite has variable surface glycoprotein coats that undergo constant antigenic variation
- Motile with single flagella
- For CNS infection treat with Melarsoprol
- For peripheral blood infection treat with Suramin
122
Naegleria fowleri
- Associated with freshwater
- Trophozoite that enters CNS via cribiform plate
- Causes primary amebic meningoencephalitis
- Rapidly fatal disease with poor prognosis
- Affects patients involved in water sports
- Has been associated with nasal irrigation systems and contact lens solutions
- Diagnosed via lumbar puncture
- Treat with amphotericin
123
Enterobius Vermicularis
- Female pinworm lays eggs at the anus
- Transmitted via fecal oral route
- Scotch tape left overnight shows eggs under the microscope
- Pyrantel Pamoate and Albendazole for treatment
124
Ancyclostoma duodenale
Nector americanus
(Hookworms)
- Hookworms
- Obtain from walking barefoot
- Larvae penetrate the soles of the feet
- In the blood they make their way to the lungs
- At the bronchial tree, they are coughed up and swallowed
- Attach to the gut wall and feed from capillaries and intestinal villi
- Causes severe iron deficiency anemia
- Diagnose via eggs in stool
- Also there is a high eosinophil count
- Treat with Pyrantel Pamoate and Albendazole
125
Ascaris lumbricoides
- The giant roundworm
- Transmitted by eating eggs that are in contaminated food or water
- Once the eggs hatch in the intestines, they make their way into the blood
- In the blood they make their way to the lungs
- At the bronchial tree, they are coughed up and swallowed
- They then mature in the small intestine
- Causes respiratory symptoms and intestinal obstruction at the ileaocecal valve
- Patients have eosinophilia
- Treat with Pyrantel Pamoate and Albendazole
126
Strongyloides Stercoralis (Threadworm)
- They hatch from eggs laid in the intestinal wall, repenetrate the wall and enter the blood stream
- Larvae are then found in the stool (no eggs)
- Cause eosinophilia
- Treat with albendazole or ivermectin
127
Trichinella Spiralis
- Nematode found in undercooked meat like pork or bear
- Fever, vomiting and periorbital edema
- Severe myalgias
- After ingestion of the cysts, they develop into larvae in the blood stream, travel to striated muscle and cause inflammation
- Cause eosinophilia
- Treat with albendazole
128
Bacillus Anthracis
- Large gram positive rods in chains
- Encapsulated made of protein (Poly D Glutamate)
- Obligate aerobe (can only survive in O2)
- Spore forming
- Produces Edema Factor (Adenylate cyclase)
=> Increases cAMP, leads to fluid to go into extracellular space, leads to edema, inhibits host defenses and inhibits phagocytosis
- Also produces Lethal Factor
+>
- Presents as a black eschar
=> Black cutaneous necrotic lesion with a surrounding erythematous ring
-
129
What are the most common catalase positive organisms?
Staphylococcus aureus - Soft tissue infections
Burkholderia cepacia - Pneumonia in CF patients
Serratia marcescens - Nosocomial and resistant UTIs
Nocardia - Pulmonary infections in immunocompromised
Aspergillus - Aspergillomas in kung cavities after TB infect
130
What are the 4 main factors that make N. Meningitidis very infectious?
- Polysaccharide capsule impairing phagocytosis of bacteria
- Lipo-oligosaccharide which induces cytokine production leading to circulatory collapse
- Pili which permit the bacteria to attach to the respiratory mucosa
- IgA protease which cleaves secretory IgA that would otherwise inactivate the pili
131
What are the 5 virulence factors of E. coli?
1. Lipopolysaccharide
2. K1 capsular polysaccharide
3. Verotoxin
4. Heat stable/heat labile enterotoxins
5. P fimbriae
132
E. coli Lipopolysaccharides mechanism of virulence?
| How does it present in a patient?
- Macrophage activation causes IL-1, IL-6 and TNF-alpha
| - Presents as bacteremia and septic shock
133
E. coli k1 capsular polysaccharide mechanism of virulence?
| How does it present in a patient?
- Prevents phagocytosis & complement mediated lysis
| - Causes neonatal meningitis
134
E-coli verotoxin (shiga like toxin) mechanism of virulence?
- Innactivates the 60S ribosomal componetns, halting protein
