Micro: Respiratory

Question 1

• Gram + bacteria
• Cocci
• Catalase +
• Coagulase +
• Protein A: binds to Fc portion of hoist IgG
• Local: skin/subcutaneous: impetigo cellulitis, folliculitis, furuncles, carbuncles, respiratory, pneumonia w/ cavitations
• Systemic: Acute Endocarditis, Menigitis, Osteomyelitis (children), Septic arthritis
• Protein A – binds Fc portion of IgG
• Coagulase (forms fibrin coat around organism)
• Hemolysins, Leukocidins – destroy RBCs and WBCs
• Neutrophils localize to infection site -> purulent abscesses form -> skin/subcutaneous infections or pneumonia
• Bacterial invasion of bloodstream
  
  • Hyaluronidase – breaks down connective tissue
  • Staphylokinase – lyses formed clots
  • Lipase – breaks down fat
• Hematogenous spread to visceral organs -> systemic infection
• Dx: blood culture +, Gram + clusters, Catalase +, Coagulase +
• Tx: MSSA (methicillin-sensitive S. aureus) -> Penicillinase-resistand penicillins,
  MRSA (methicillin-resistant S. aureus) -> vancomycin

Answer 1

Staphylococcus aureus

Question 2

• Gram +
• Catalase –
• Bile-esculin negative
• Optochin susceptable
• Diplococci
• Quellung rxn +
• Local: Lobar pneumonia, Otitis media, Sinusitis
• Systemic: Meningitis, Septic arthritis, Endocarditis
• Evades host defenses by: Capsule (escapes phagocytosis), IgA proteases
• Alveoli inflammation: disseminate via pores fo Kohn -> Lobar pneumonia
• Tx: Penicillin, Cephalosporins (except Vanco for meningitis)
• Asplenic patients are especially susceptible, unable to remove Ab-coated organisms (give Pneumovax)

Answer 2

Streptococcus pneumoniae

Question 3

Common Causes of Pneumonia in?

• Adults (40 – 65 yrs)?
• Elderly (> 65 yrs)?
• Most common cause of meningitis in 60+ yrs?

Answer 3

• Adults (40 – 65 yrs)
  
  • S. pneumoniae
  • H. influenzae
  • Legionella
• Elderly (> 65 yrs)
  
  • S. pneumoniae
  • Gram – rods
  • H. influenzae
• Most common cause of meningitis in 60+ yrs
  
  • S. pneumoniae
  • Gram – rods
  • Listeria

Question 4

• Acid-fast bacteria w/ Mycolic acid cell wall
• Thin rods, non-motile, Obligate Aerobic
• Grows at body temperature
• Caseous granulomas
• Ghon complex on CXR (calcified pulmonary tubercles + Hilar lymph nodes)
• IFN-γ released by Lumphocytes exposed
• Primary – Lower Lobes of Lungs
• Secondary – Upper Lobes – High O₂ and Low Lymphatics
• (Miliary) disseminate to other sites thru Lymphatics
• Tx: RIPES

Answer 4

Mycobacterium tuberculosis

Question 5

Clinically important bacteria that have acid-fast positive staining?

Answer 5

• Mycobacteria
  
  • Mycobacterium tuberculosis
  • Mycobacterium avium
  • Mycobacterium intracellulare
• Nocardia

Question 6

• Fungi
• Systemic infection, immunocompromised, pneumonia
• Asymptomatic, immunocompetent
• Granulomas may form throughout the body
• Dx: Serology, Branched Hypae at 25°C, Single cells at 37°C
  
  • Intradermal inj. Of Coccidlidin antigen causes DTH response
• Tx: Supportive, anti-fungals (systemic), Amphotericin B (CNS not involved) and Fluconazole (if CNS is involved)

Answer 6

Coccidioides immitis

Question 7

Systemic mycoses are endemic to particular areas?

• Southwest U.S. -> ?
• Mississippi/Ohio River Valleys, Southeast U.S. river basins -> ?
• East of Mississippi River and Central America -> ?

Answer 7

• Southwest U.S. -> Coccidioido mycosis
• Mississippi/Ohio River Valleys, Southeast U.S. river basins -> Histoplasmosis
• East of Mississippi River and Central America -> Blastomycosis

Question 8

• Fungi
• Systemic infection, pneumonia
• At 37°C the spores become yeast -> local Lung infection -> Acute pneumonia and Granulomas throughout the body
• Dx: Serology, Branched Hypae at 25°C, Single cells at 37°C
• Biopsy: Large budding yeast

Answer 8

Blastomyces dermatitidis

Question 9

• Fungi
• Systemic infection, immunocompromised
• Asymptomatic, immunocompetent
• Bird droppings are inhaled -> Macrophages phagocytose spores -> budding yeast from w/in -> infection w/in epithelioid granulomas -> small Ca²⁺ deposits on CXR (esp. Adrenals, Liver, Spleen)
• Dx: Serology, Branched Hypae at 25°C, Single cells at 37°C
• Yeast cells w/in Histocytes (Macrophages)
• Histoplasmosis a sign of AIDS in HIV-positive exp. to Bird shit.
• Intradermal injection of Histoplasmin antigen -> DTH response
• Tx: Supportive, Antifungals (systemic), Amphotericin B, Ketoconazole, Itraconazole

Answer 9

Histoplasma capsulatum

Question 10

• No cell wall
• Marked Pleomorphism
• Resistant to b-lactam ABX
• No Gram stain
• Cultures have ‘fried-egg’ appearance
• Tracheobronchitis (via P1 adhesion) – Atypical pneumonia “walking pneumonia” – Vacuolation and Ciliostasis (inhibits ciliary motion)
• Young people – in Close Quarters (Prisons, Military, Colleges)
• Produces CARDS toxin – homolog to Pertussis toxin
• Dx: Cold Hemagglutination -> > 4x IgM Ab bind RBCs after 1-2 weeks w. Eaton’s agar
• CXR looks worse then symptoms suggest
• Tx: Tetracycline or Macrolides (Erythormycin or Azithromycin), b-lactam ABX are NOT effective

Answer 10

Mycoplasma pneumonia

Question 11

Common causes of atypical pneumonia?

Answer 11

• Mycoplasma
• Legionella
• Chlamydia
• Viruses

Question 12

Most common causes of pneumonia
in adults (18 – 40 yrs)?

Answer 12

• Mycoplasma
• C. pneumoniae
• S. pneumoniae

Question 13

• Atypical pneumonia
• Community acquired, Young adults
• Phagocytosed by macrophages -> lymphocye infiltration at site of infection -> local pulmonary edema, necrosis, and hemorrhage
• (2) Forms in the Life cycle

1. Extracellular elementary body (EB) -> infective form
2. Intracellular Reticular body (RB)

• EB upper respiratory -> EB phagocytosed -> EB transforms into RB -> special cell wall blocks phagosome lysosome fusion -> RB multiplies w/in intracellular body -> RB condenses to EB -> EB bursts
• Dx: Giemsa stain to visualize intracytoplasmic inclusions
• Tx: intracellular ABX: Doxycycline

Answer 13

Chlamydia pneumoniae (TWAR)

Question 14

Two obligate intracellular parasites
(require host ATP for energy)?

Answer 14

• Chlamydiae -> replicate w/in inclusion bodies
• Rickettsiae -> replicate freely w/in cytoplasm

Question 15

• Most frequent cause of bacterial STD in U.S.
• Most common cause of Blindness worldwide
• Serovars A-C: trachoma (chronic conjunctivitis)(hand-eye contact)
• Serovars D-K: Urethritis, PID, Neonatal pneumonia, Neonatal conjunctivitis, Cervicitis, Inclusion conjunctivitis (columnar epithelium)
• Serovars L1-L3: Lymphogranuloma venereum (LGV), STDs
• Complications: Fitz-Hugh-Curtis syndrome, Reiter’s syndrome (HLA-B27)
• Dx: PCR, Transcription-mediated amplification, Iodine stain +, Giemsa stain +
• Tx: Azithromycin, Tetracyclines (+ceftriaxone for concurrent N. gonorrhea), Oral Erythromycin for Neonates w/ infected mothers, Prophylactic Erythromycin eye drops for Neonates

Answer 15

Chlamydia trachomatis

Question 16

Common causes of non-gonoccal
urethritis (NGU)?

Answer 16

• Chlamydia trachomatis
• Ureaplasma urealyticum

Question 17

• Atypical pneumonia
• Endocarditis
• Carried by birds (parrots) -> bird feces -> Upper respiratory tract
• Phagocytosed by macrophages -> lymphocye infiltration at site of infection -> local pulmonary edema, necrosis, and hemorrhage
• (2) Forms in the Life cycle

1. Extracellular elementary body (EB) -> infective form
2. Intracellular Reticular body (RB)

• EB upper respiratory -> EB phagocytosed -> EB transforms into RB -> special cell wall blocks phagosome lysosome fusion -> RB multiplies w/in intracellular body -> RB condenses to EB -> EB bursts
• Dx: Visualize intracytoplasmic inclusions, Iodine stain -, Giemsa stain +, > 4x rise in Ab titer, Single IgM > 1:16, Microimmunofluorescence
• Tx: ABX that enter cell: Doxycycline, Macrolides(Erythromycin or Azithromycin)

Answer 17

Chlamydia psittaci

Question 18

• Atypical pneumonia
• Does NOT cause Rash
• Endospore w/in cell
• Carried in Cattle, Sheep, Goats
• Survives extracellularly as a spore -> inhalation -> atyp. pneu. -> leads to Hepatitis, Chronic Endocarditis
• Dx: Serology, Culture w/in cells, Weil-Felix –
• Tx: Tetracycline

Answer 18

Coxiella burnetii (a Rickettsia)(Q Fever)

Question 19

• RNA virus
• Helical nucleocapsid
• Enveloped
• SS- nonsegmented
• Paramyxoviridae
• HA/NA (binds sialic acid/cleaves, sialic acid interaction
• F (causes infected cells to fuse)
• M protein (involved in assembly)
• Children (croup – Laryngotraccheobronchitis, pneumonia)
• Adults (common cold)
• Hemagglutinin (HA) envelope protein binds sialic acid on cells
• Neuroaminidase (NA) envelope protein cleaves HA – sialic acid interaction to permit viral spread down Tracheal and Bronchial epithelium
• Obstruction of insipiration (insipiratory stridor) and expiration (barking cough) -> Croup
• Dx: Hemagglutination act. in resp. secretions, anti-HA ABX inhibit
• Tx: Supportive (cool mist, oxygen in severe cases), Corticosteroids

Answer 19

Parainfluenza Viruses (Paramyxoviridae Paramyxovirus, Paramyxoviridae Rubulavirus)

Question 20

Most common causes of pneumonia
in Young Children?

Answer 20

• RSV
• Parainfluenza virus

Question 21

• RNA virus – respiratory syncytial virus
• Helical nucleocapsid
• Enveloped
• SS- nonsegmented
• Paramyxoviridae
• G (allows virus to attach to cells)
• F (causes infected cells to fuse)
• Children (bronchiolitis -> Asthma + wheezing, pneumonia)
• Adults (common cold)
• Nasal secretions -> hand2hand and aerosol -> attaches to Bronchiolar and Alveoli epithelium via G protein on viral envelope
• Dx: Det. w/in resp. secretions, serology
• Tx: Supportive, Albuterol, Aerosolized Ribvirin (severe), Synagis (Fantigen vaccine) prevent infection in High-risk pts. (Premies, Lung disease, Heard disease)

Answer 21

Paramyxoviridae Pneumovirus –
Respiratory Syncytial Virus (RSV)

Question 22

• DNA viruses
• Icosahedra nucleocapsid
• Non-enveloped
• DS linear
• Adenoviridae
• HA fiber protruding from each of 12 vertices of capsid
• Respiratory tract infection, Conjunctivitis, Hemorrhagic cystitis, Gastroenteritis
• Fecal-oral route -> bind via hemagglutinin -> enters and lyses mucosal cells
  
  • Upper respiratory tract -> rhinitis, sore throat -> lower atyp. pneu.
  • Conjunctiva -> Conjunctivitis
  • Bladder -> Hemorrhagic cystitis -> Hematuria, Dysuria
  • GI tract in kids -> Gastroenteriris w/ non-bloody Diarrhea
• Dx: Serology, Isolation of virus in cell culture
• Tx: Vaccine w/ live viruses (only military)

Answer 22

Adenoviridae Mastadenovirus

Question 23

Causes of common cold?

Answer 23

• Rhinovirus
• Coronavirus
• Adenovirus
• Influenza C virus
• Coxsackivirus

Question 24

Most common causes of conjunctivitis?

Answer 24

• H. influenza
• Adenovirus
• S. pneumoniae

Question 25

• DNA viruses
• Icosahedral nucleocapsid
• Enveloped
• DS linear
• Herpesviridae
• Intranuclear inclusion bodies form in infected cells because virus replicates w/in nucleus
• Envelope (only virus that obtains envelope by budding from nuclear membrane)
• Infectious mononucleosis (“kissing disease”)
• Lymphoid orgain-related cancers: Burkitts’s Lymphoma (neoplasms), nasopharyngeal cancer (in East Asians)
• Infects B cells via C3d complement receptor -> latent in B cells as episomal DNA -> Lymph nodes, Spleen enlarge w/ flu like symptoms
• Dx: monospot test – detects heterophil Ab (agglutinates sheep RBCs), Blood smear – w/ cytotoxic T lymphocytes that react against B cells, anti-EBV IgM (acute infection) and IgG (past infection)
• Tx: Acyclovir (severe cases)

Answer 25

Herpesviridae Lymphocryptovirus

(EBV or Herpesvirus 4)

Question 26

• Gram – bacteria
• Coccobacilli, pleomorphic
• Growth of Bordet-Gengou medium
• Filamentous hemagglutinin (FHA)
• ‘Safety-pin shape’
• Children -> “Whooping cough”
• Adults -> cold w/ nagging cough
• Adheres to cilia of resp. epith. Via FHA -> release exotoxins
• Pertussis toxin -> AB toxin -> ADP-ribosylates and inactivates GI proteins -> uninhibited adenylate cyclase -> increase cAMP -> Lymphocytosis, decreased phagocytosis
• Cytotoxin -> kills ciliated epi. Cells -> impairs muccous clearance
• (3) Stages

1. Catarrhal stage (1 – 2 weeks) - flulike symptoms, highly contagious
2. Paroxysmal stage (3^rd week – 2 months) intermittent bouts of many coughs on a single expiration followed by whooping inspiration
3. Recovery stage (2 -3 months) – coughing subsides

• Dx: Gram - , Coccobacilli, Bordet-Gengou medium
• Tx: Prophylaxis: DtaP vaccine: acellular Pertussis antigens, treatment: erythromycin (only before paroxysmal phase), supportive care
• DTaP: 2, 4, 6, and 18 months and every 10 years

Answer 26

Bordetella pertussis

Question 27

• Gram – bacteria
• Bacilli
• Lactose non-fermenter
• Oxidase +
• Glucose non-fermenter
• Pneumonia (CF patients); UTIs, Burn wounds, Septicemia, Endocarditis (IV drug users), Oseomyeitis (DM, IV drug users), Malignant ext. otitis (DM), Folliculitis (Hot tubs)
• Exotoxin A -> ADP ribosylates host EF2 -> paralyzes host protein machinary
• Phospholipase C -> Cleaves phosphates from phospholipids
• Elastase -> cleaves elastin -> allows microorganism to disseminate to better nutrient sources
• Endotoxin -> shock
• Dx: Gram – rods, Blue-green colonies (pyocyanin pigment) w/ Fruity odor
• Tx: anti-Pseudomonal penicillin + aminoglycoside (piperacillin + gentamicin, mezlocillin + gentamicin), Gluoroquinolones, and other ABX combinations

Answer 27

Pseudomonas aeruginosa

Question 28

• Gram – bacteria
• Coccobacilli, pleomorphic
• Growth on charcoal yeast agar w/ Iron (Fe) and Cysteine (Cys)
• Pontiac fever -> acute flulike illnes lasting 2-5 days
• Legionnaire’s disease (atypical pneumonia) -> neutrophils arrive and form microabscesses
• Naturally inhabits water reservoirs -> inhaled aerosois from respiratory devices -> survives and proliferates inside nutrient-rich phagosome -> weakens macrophage resp. burst -> prevents phagosome from fusing w/ lysosome
• Dx: Gram stains poorly, Use Silver stain, culture on charcoal yeast extract w/ Fe and Cysteine, Urinary antigen detected by Radioimmunoassay serology
• Tx: Erythromycin

Answer 28

Legionella pneumophila