- 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
Staphylococcus aureus
- 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)
Streptococcus pneumoniae
Common Causes of Pneumonia in?
- Adults (40 – 65 yrs)?
- Elderly (> 65 yrs)?
- Most common cause of meningitis in 60+ yrs?
- 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
- 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
Mycobacterium tuberculosis
Clinically important bacteria that have acid-fast positive staining?
-
Mycobacteria
- Mycobacterium tuberculosis
- Mycobacterium avium
- Mycobacterium intracellulare
- Nocardia
- 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)
Coccidioides immitis
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 -> ?
- Southwest U.S. -> Coccidioido mycosis
- Mississippi/Ohio River Valleys, Southeast U.S. river basins -> Histoplasmosis
- East of Mississippi River and Central America -> Blastomycosis
- 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
Blastomyces dermatitidis
- 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
Histoplasma capsulatum
- 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
Mycoplasma pneumonia
Common causes of atypical pneumonia?
- Mycoplasma
- Legionella
- Chlamydia
- Viruses
Most common causes of pneumonia in adults (18 – 40 yrs)?
- Mycoplasma
- C. pneumoniae
- S. pneumoniae
- 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
- Extracellular elementary body (EB) -> infective form
- 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
Chlamydia pneumoniae (TWAR)
Two obligate intracellular parasites
(require host ATP for energy)?
- Chlamydiae -> replicate w/in inclusion bodies
- Rickettsiae -> replicate freely w/in cytoplasm
- 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
Chlamydia trachomatis
Common causes of non-gonoccal
urethritis (NGU)?
- Chlamydia trachomatis
- Ureaplasma urealyticum
- 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
- Extracellular elementary body (EB) -> infective form
- 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)
Chlamydia psittaci
- 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
Coxiella burnetii (a Rickettsia)(Q Fever)
- 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
Parainfluenza Viruses (Paramyxoviridae Paramyxovirus, Paramyxoviridae Rubulavirus)
Most common causes of pneumonia
in Young Children?
- RSV
- Parainfluenza virus
- 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)
Paramyxoviridae Pneumovirus –
Respiratory Syncytial Virus (RSV)
- 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)
Adenoviridae Mastadenovirus
Causes of common cold?
- Rhinovirus
- Coronavirus
- Adenovirus
- Influenza C virus
- Coxsackivirus
Most common causes of conjunctivitis?
- H. influenza
- Adenovirus
- S. pneumoniae
- 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)
Herpesviridae Lymphocryptovirus
(EBV or Herpesvirus 4)
- 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
- Catarrhal stage (1 – 2 weeks) - flulike symptoms, highly contagious
- Paroxysmal stage (3rd week – 2 months) intermittent bouts of many coughs on a single expiration followed by whooping inspiration
- 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
Bordetella pertussis
- 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
Pseudomonas aeruginosa
- 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
Legionella pneumophila