Flashcards in Micro 3 Deck (208):
What are common causes of meningitis in neonates?
Group B strep
What are common causes of meningitis in post-neonatal life?
Cause of chronic meningitis?
Causes of bacterial encephalitis?
Borrelia burgdorferi (Lyme Disease)
3 ways that microbes can penetrate the BBB
1. infection of the cells that comprise the barrier
2. passive transport through cells in vacuoles
3. carraige in WBCs
Why might steroidal anti-inflammatories be use in the treatment of meningitis?
Dampen the immune response
Decrease infiltration of PMNs, macrophages and pathogens
WBCs -> cytokines -> inflammation, edema, additional WBC recruitment
inflamation and edema are conducive to infiltration (diapedesis)
What are symptoms of meningitis?
high fever, sever and persistent stiff neck, photophobia, N/V
Changes in behavior: confusion, sleepiness, difficulty in waking (indicative of need for emergency treatment)
Infant: irritability, tiredness, poor feeding, fever, *bulging fontanel*
meningitis causing, gram +, catalase -, a-hemolytic, optochin sensitive
S.pneumo - most common cause of meningitis in US
Is there a vaccine for S.pneumo?
23-valent: capsular PS from strains responsible for 90% of infections
7-valent: capsular PS from strains responsible for infections in children, immunocompromised, elderly
What is the leading cause of bacterial meningitis in US?
What is second?
What are the most common capsular serotypes of meningitis causing N.meningitidis and what are the relative frequencies:?
In addition to typical meningitis symptoms, what may be seen in patients w/ N.meningitidis meningitis?
Hemorrhagic rash often w/ petechiae - reflective of assoc. septicemia
-1/3 of instances rash is fulminating w/ complications due to disseminated intravascular coagulation (DIC), endotoxemia, shock, renal failure
-DIC may -> gangrene / necrosis in extremities
What does H.influenzae require for growth?
Factors X: NAD and V: hemin
What organisms are typically responsible for outbreaks at universities?
Risks: poor diet, behavioral changes (ETOH consumption, smoking), pulmonary infections -> changes in immune function and microbiota composition
Some schools -> vaccination program
What is the fatality rate of neonatal meningitis?
How do survivors do?
1/3 of cases fatal
Survivors: often long-term sequelae: cerebral palsy, epilepsy, mental retardation, hydrocephalus
What organism causes Lyme Disease?
Disseminated disease can -> bacterial encephalitis
What is Guillan Barre Syndrome and what causes it?
Caused by Campylobacter jejuni
Disease is result of cross-reaction between bacterial ganglioside-like epitopes in LPS and Schwann cell myelin Ags
Immunologic attack ->Demyelination
How is a brain abscess diagnosed?
CT scan recommended before lumbar puncture
Characteristic ring-enhancing lesion w/ contrast is diagnosis
-fibrous capsule forms w/in 4-5 days of infection
Symptoms of brain abscess
headache, confusion, drowsiness, hemiparesis, seizures, fever
*usually no stiff neck*
What organisms are most often isolated from a brain abscess?
Gram +: Streptococcus (anginosis, milleri), Peptostreptococcus, Staphylococcus, Nocardia, Actinomyces
Gram -: Prevotella, Fusobacterium, Bacteroides, E.coli, Citrobacter koseri, P.mirabilis
AIDS pts: cryptococcus, toxoplasma
Almost always polymicrobial. Strep most common - synergy w/ gram negs
What often cause chronic meningoencephalitis?
What are the functions of bacterial capsules in CNS infection?
Prevent phagocytosis, Ab binding, complement activation
Toxicity to host cells
What is and what causes Valley Fever?
Fungal infection beginning in the lungs 7-21 days post infection
Typically clears quickly, but can disseminate to meninges, bones, joints, subcutaneous and cutaneous tissues
25% of disseminated cases -> meningitis (1% of total cases)
Initially flu-like, then symptoms of meningitis
Fatal if not treated.
Caused by Coccidiodes imitis (Fungus)
Risk: dust storms, earthquakes, excavation
What is Chagas Disease?
Caused by Trypanosoma cruzi - parasite carried by Triatome bugs
Initial sore at site of bite followed by fever and acute encephalitis
Chronic disease may have heart, colon, and nervous system manifestations
Where is Trypanosoma cruzi endemic?
Southern US - Southern Argentina
What is the CNS manifestation of malaria?
If malaria left untreated, infection can travel to brain causing lesions, coma and rapid death (24-72 hours)
Acute, widespread brain disease w/ fever
Greatest risk <10 years of age
5 genra of picornoviruses and associated diseases
1. Enterovirus (Polio, Coxsackie A and B, Echo) - diseases of alimentary (GI) tract
2. Rhino - cold - naspharyngeal
3. Cardiovirus - murine encephalomycarditis
4. Apthovirus - Foot + Mouth disease (cloven footed animals)
5. Hepatovirus - Hepatitis A
Properties of Cardio, Hepato and Entero viruses
Resistant to low pH, grow at 37C
Fecal-oral transmission, GI is site of primary infection
CNS infection results - paralysis and encephalitis
General properties of Aptho and Rhino viruses
Labile at low pH, grow at 33C
Aerosol transmission - Upper Respiratory Tract is site of infection
Unenveloped ss+RNA, 7-8kb
Long 5' untranslated end regulates translation - IREM (internal ribosome entry site)
VPg protein at 5' end - primer
3' end- short untranslated w/ poly-A tail
Where in the cell do picornaviruses replicate?
Describe protein product of picornovirus
Single polypeptide divided into 3 regions (P1,P2,P3)
3 regions cleaved - 11-12 proteins
P1: capsid proteins (VP1,2,3,4)
P2 and P3: protein processing and genome replication proteins
Describe the process of Picornavirus replication
virus attaches to host cell via VP1
Uncoating of genome
RNA translation -> P1 stays in cytoplasm, P2,3 and -RNA copies in vessicles
+RNA -> -RNA -> +RNA
Encapsidation and cell lysis
What do Picornaviruses do to host cell processes?
Shut off protein synthesis via cleavage of eIF-4G by VP 2A (entero and rhino) and L (aptho)
What are the non-structural proteins produced by Picornaviruses?
2A: protease (P1/P2)
2B: stim vessicle formation
2C: RNA helicase
3AB: stimulates 3D and 3CD protolytic cleavage
3C: protease (P2/P3)
3D: RNA dependent RNA polymerase
VPg: Poly(U) primer
How do picornaviruses infect?
infect via GI with primary target being lymph tissue of oropharynx and gut
If Ab does not clear infection, progression from blood to organs and major viremia, then CNS infection
Virus production in grey matter (motor neurons of anterior horn of SC and brain stem)
Severe illness, paralysis
What disease is caused by polio virus? symptoms?
Destruction of motor neurons in anterior horn of SC -> Flaccid paralysis
Bulbar poliomyelitis: more severe - destruction w/in medulla oblongotta
2 polio vaccines
Salk - Inactivated - less local GI immunity, duration of immunity unknown
Sabin - Attenuated - oral - probable life long immunity
What diseases are caused by Coxsackie viruses?
A and B: aseptic meningitis
A: Herpangina - sudden onset fever w/ ulcers on tonsils and palate
A16: Hand Foot and Mouth disease
Role in Acute Juvenile diabetes (type I)?
What does rhinovirus cause?
Drug designed against entero and rhinoviruses
-not FDA approved
-initially rejected due to side effects
What does Apthovirus cause?
Foot and Mouth in animals
Vaccine available - effective against symptoms, but does not protect against transmission
Slaughter infected animals
What is the role of HIV in CNS infections
Neurological complications are common in AIDS patients
Virus found in CSF of patients w/ dementia
Virus infects or activates macrophages and microglia -> release of toxins deleterious to neurons and astrocytes
2 viral subtypes
3 classes of HIV drugs and examples
Nucleoside RT inhibitor: Zidovudine, Didanosine, Zalcitabine, Stavudine, Lamivudine, AZT
Non-nucleoside RT inhibitor: Nevirapine, Delavirdine
HIV Protease inhibitor: Ritonavir, Indinavir, Saquinovir, Nelfinavir
What is HAART treatment?
Highly active anti-retroviral treatment
A "cocktail" of at least one nucleoside RT inhibitor and one or two Protease inhibitors
***Does not provide full protection against neurological damage in HIV infection - BBB only partially permeable to anti-retroviral agents***
What is HTLV and what does it cause?
Human T-cell Leukemia Virus
1. Adult Tcell Leukemia
2. Tropical Spastic Paraparesis / HTLV-1associated myelopathy (TSP/HAM)
What treatments exist for HTLV?
No definitive treatment
Combination IFNa and Zidovudine (NRTi)
Chemotherapy (limited success)
Zidovudine, Danazol, Vitamin C -> temporary relief
What is a virus spread to humans via an insect bite?
fleas, ticks, flies, etc. are vectors for transmission
Primary reservoir is birds
Name two families of viruses considered arboviruses
What are the 3 genera of flaviviridae? What diseases are each responsible for?
Flavivius: YFV, WNV, DFV, JE
Hepacivirus: Hep C
Pestivirus: no human disease (Hog cholera, Bovine viral diarrhea)
Enveloped, icosahedral virion, linear ss+RNA
3 structural proteins: envelope, prM (M separates @maturation, maturation signal), C (capsid)
Flavi, HepC: 5' cap, non-polyA 3'
Pesti: no caps, no poly-a IRES
What is Antibody Dependent Enhancement?
In Dengue Virus:
Initial infection with one serotype (strain 1) -> Ab response
Later infection with different serotype: anti-strain 1 Ab do not neutralize, but allow macrophage to take up virus more effectively. Inside macrophage virus repliates -> more severe infection due to additional mechanism of infection
Describe flavivirus process of cell infection / replication
Receptor mediated attachment and endocytosis (viral E protein)
pH induced membrane fusion and uncoating of virion
+RNA -> single viral protein
RNA synth via RdRp
C protein encapsidation in cytoplasm
Maturation of membranes in rER or golgi
Transport of virus to cell surface by secretory pathway
Structural and non-structural proteins of flavivirus
E: binds cell surface receptors, facilitates entry
NS1: hemagglutinin -elicits humeral immune response
NS2A and B: RNA synthesis
NS4A and B: RNA replication
NS5: RNA dependent RNA polymerase
West Nile symptoms
Moderate to high fever, flu-like
sore throat, headache, backache, fatigue
Rash, lymphadenopathy, myalgia
Acute aseptic meningitis or encephalitis
West nile treatment
Yellow Fever symptoms and treatment
High fever, chills, headache, vomiting
Jaundice, hemorrhagic complications, renal failure
Mosquito (aedis aegypti) control important for prevention
Dengue fever transmission and symptoms
Person to person, mosquitos
symptoms: fever, headache, lumbosacral pain
also - Dengue hemorrhagic fever DHF
Dengue Shock Syndrome DSS
What is the distribution of Dengue Fever serotypes?
Serotype 2 - North America
Serotypes 1 and 3 - Central and South America
Is there a Dengue vaccine?
A tetravalent vaccine has been tested in Thailand - favorable results
What is St. Louis Encephalitis?
Flavivirus caused encephalitis (epidemic disease)
Transmitted by mosquito from birds to human
Febrile headache to meningo-encephalitis
Milder in children
Elders at risk
Hepatitis C treatment
IFN induces genes that regulate viral proteins at transcriptional and translational levels
only effective in 15% of patients
IFN + ribavirin for relapsed patients
What viruses are Togaviruses?
EEE: eastern equine encephalitis
WEE: western equine encephalitis
Characteristics of Togavirus and major proteins
What is Eastern Equine Encephalitis?
togavirus transmitted from birds -> mosquitoes -> horses and humans
Fever, general muscle pain, severe headache, permanent brain damage, seizure, coma
Small brain hemorrhages and extensive neuronal damage
What virus causes Rabies?
bullet shaped, external glycoprotein coat and peripheral matrix protein
Ribonucleoprotein is most infectious component
What is the incubation time for rabies?
up to 12 mos.
difficulty breathing and swallowing
Increased muscle tone
cytoplasmic eosinophilic inclusion bodies (Negri bodies) in neuronal cells and neuronal necrosis
Treatment for rabies?
Not after symptoms appear - 100% fatal
1) wash wound w/ soap and water - seek medical attention immediately
2) passive immunization - admin human rabies immune globin
3) vaccination (inactivated virus)
what is the major problem in meningitis? Why?
Increased ICP is major problem.
leads to decreased cerebral blood flow, loss of cerebrovascular autoregulation
Subarachnoid space inflammation -> cerebral vasculitis -> possibility of cerebral infarction
What organisms are typically seen in meningitis following head trauma or neurosurgery?
aerobic gram neg. rods (including pseudomonas)
What organisms are most often seen in meningitis assoticated with a basilar skull fracture and/or CSF leak?
Group A B-hemolytic strep
What is normal CSF opening pressure?
What bacterial antigen identification kits are available?
S.pneumoniae, N.meningitidis, HiB, E.coli, GBS
What are early and late complications of meningitis?
Early: shock, disseminated intravascular coagulation, respiratory failure (adult resp. distress syndrome), cerebral edema
Late: behavioral / learnig disabilities, hearing loss, seizures, hydrocephalus
How might neonatal CSF differ from adult?
Normal neonate CSF may have up to 30 WBC/mm3 (normal for adult is 0.5)
and up to 150 mg/dL protein (normal for adult 15-45)
Definition of aseptic meningitis
Meningitis with lymphocytic predominant pleocytosis in which bacterial stains and cultures are negative
Most common viruses in aseptic meningitis
-most common in infants and young children
-usually less severe presentation
-most often late summer / early fall
-occurs in community outbreaks
What is the overall mortality for CA meningitis? What about individual pathogens?
CA meningitis: 25%
CD4 TH1 cells do what?
Activate macrophages enabling them to destroy intracellular organisms
CD4 TH2 cells do what
stimulate B cells to differentiate into plasma cells to produce specific antibodies
What is a primary vs. secondary defect of the innate immune system?
Secondary: acquired - breach of mechanical barrier
What is chronic granulomatous disease and what is it an example of?
Defect in NADPH oxidase that prevents neutrophils from releasing a respiratory burst during phagocytosis.
Example of primary defect of innate immunity
Results in increased susceptibility to catalase positive organisms, esp. Serratia and Aspergillus
What is the most common cause of intravascular catheter associated infection?
What infections are common at burn sites?
Polymicrobial infections due to bacteria and fungi
Mechanical breach, damage to neutrophil function and capacity for immune response
What is the most common cause of surgical wound infections? Why?
Often impaired blood supply and foreign bodies (sutures) -> ease of colonization
May progress to endocarditis or osteomyelitis
How do staph species "hide" from antibiotics on plastic catheter material?
Grow as biofilm - produce and multiply within slimy, adherent material
What is post-obstructive pneumonia? What organisms are often seen?
infection develops in the lung distal to an occlusion such as a tumor or fibrotic growths following surgery. Results in stasis of body fluids distal to obstruction - favorable medium for bacterial growth.
Oropharyngeal aerobes and anaerobes are common
Obstruction of bladder or ureters can result in what serious complications? What could cause obstruction?
hydronephritis or pyonephritis
Could be caused by neoplasm of prostate, cervix, rectum, ovary, etc.
Depressed neutrophil count. May be caused by a primary malignancy (leukemia) or chemotherapy.
What is the most commonly seen immune defect resulting in life threatening infections in compromised hosts?
What is more common in neutropenic patients - gram (-) or (+) infection? How is empiric treatment influenced?
Gram (+) is more common
Treatment still geared toward gram neg. Can rapidly lead to lethal infection. (+) species tend to be less virulent.
What is the most common cause of secondary defects in adaptive immunity worldwide?
Humoral immune impairment produces increased susceptibility to what organisms?
encapsulated orgs such as Streptoccus pneumonia, Haemophilus influenzae, Neisseria meningitidis
What disease states are associated with humoral immune abnormality?
Multiple myeloma, chronic lymphatic leukemia, Waldenstrom's macroglobulinemia, sickle cell
What diseases are associated with cellular immune deficiency or defect?
Hodgkins and non-Hodgkins Lymphoma, Hairy Cell Leukemia, Chronic Lymphatic Leukemia
Chemotherapy, Corticosteroid treatment, transplant also associated.
What infections are more likely with impairment of the cellular immune system?
Intracellular bacteria, mycobacteria, viruses, fungi, protozoan
-pretty much everything
-prompt diagnosis is vital
-fixing underlying cause of the deficit is key!
Neurotropic vs. Neuroinvasive vs. Neurovirulent
Neurotropic: can infect neurons and/or assoc. cells regardless of route of infection or pathogenic consequence
Neuroinvasive: can enter CNS after infecting peripheral site
Neurovirulent: can cause disease by damaging nervous tissue
linear dsDNA (80+ genes)
What is the most common cause of sporadic fatal encephalitis in adults?
What part of the brain is most often involved in HSV-1 encephalitis?
Fever, altered consciousness and behavior, disordered thinking
What abnormalities does brain tissue affected by HSV-1 encephalitis display?
Necrosis and punctate hemorrhage
Inferior frontal and temporal lobes
How are HSV infections of the CNS diagnosed and treated?
Diagnosis: PCR of CSF
MRI shows temporal lobe hemorrhage and/or edema
EEG spike and slow-wave activity
Treatment: acyclovir and other herpes viral drugs reduce mortality but most patients do not regain full mental function
What CNS diseases are caused by VZV?
encephalitis (.1-.2% cases)
transient cerebellar ataxia (.1%)
meningitis and transverse myelitis (rare)
post herpetic neuralgia (PNS)
Diagnosis and treatment of VZV infection of CNS
PCR of CSF
treat with Famciclovir or valacyclovir (higher bioavailability than fam)
Prevent w/ vaccines!!
What is the most common cause of birth defects and childhood disabilities in the US?
What are signs of congenital CMV that can be seen at birth?
Intrauterine growth retardation, hepatosplenomegaly, microcephaly
Later development of mental retardation, seizure, blindness, deafness, death
Non symptomatic at birth: 10-15% risk of developing hearing and vision problems, intellectual impairment.
What is treatment for CMV and prophylaxis for prevention of transplacental transmission?
IVIG to prevent congenital disease (result of uncontrolled trial)
Gancyclovir for treatment of congenital disease
Herpes B Virus
Cercopithecine herpesvirus 1
Biosafety Level 4 pathogen
Carried by monkeys, transmitted to humans via saliva, bodily secretions
High frequency of fatal encephalitis
treatable w/ high doses of acyclovir or gancyclovir
Polyomavirus and associated disorders
JC - Progressive Multifocal Leukoencephalopathy (immunodeficient patients, usually fatal)
BK - hemorrhagic cystitis (bone marrow transplant patients)
polyomavirus nephropathy (kidney transplant patients)
New: KIV, WUV - found in resp. sec., unknown pathogenicity
MCV - merkel cell cancer
SV40: humans infected via animal vaccines - unknown pathogenicity
PML: what is it, symptoms, treatment
Progressive multifocal leukoencephalopathy
JCV in immunocompromosed patients
Personality changes, intellectual deficit, loss of motor skills, sensory loss
Death in 2-12 months
Treament: HAART - immune recovery
What is the most common transmissable spongiform encephalopathy
What are the forms of CJD?
Sporadic - unknown cause
Familial - Autosomal dom (onset 50yrs)
Iatrogenic - neurosurg, transplant, brain derived hormones
Variant - bovine spongiform encephalopathy (mad cow) -> humans
List oral anaerobes
What virulence factors are associated with oral infections?
Oral bacteria produce lymphocyte activators that induce inflammatory response
Release of PMN contents and complement activation -> tissue damage.
What causes gingivitis?
Inflamation of the gums - marginal inflammation where teeth meet gums
Inflammatory infiltrate: PMNs and lymphocytes in tissue and connected to tooth
What is periodontitis?
Caused by progression of gingivitis. Results in resorption of bone around neck of tooth, destruction of periodontal ligament, and eventual loosening and loss of affected teeth.
Causative oral anaerobes live in dental plaque next to gingival tissues.
What organisms are associated with ulcerative gingivitis?
Prevotella, Fusobacteria - invade oral epithelium
ID, what it causes
Normal flora anaerobe in humans
Gram positive filamentous rod-shaped bacteria. "Sulfur granules" seen in pus - actinomyces elements mixed with tissue exudate
grows slowly in culture and may be overwhelmed by contaminating bacteria
Causes cervicofacial infections following oral trauma - tooth extraction - can travel down lymph tract
Viridans Streptococcus and oral infections
Virulence: attatch to teeth w/ glucans. May enter blood stream following dental procedure (tooth extraction) and produce subacute bacterial endocarditis
group includes Streptococcus Mutans - assoc. with dental carries.
ID Strep viridans
Gram pos, catalase neg
No lancefield group
Assoc. w/ dental caries.
Who is at risk for oral Candida infections?
Immunocompromised, chemo patients, those receiving antimicrobial therapy
Streptococcus pneumoniae virulence factors
Capsule - 84 serotypes
interferes with classical and alternative complement pathway
teichoic acid -> inflammation
specific Ab confers immunity
Upper respiratory infections caused by S.pneumoniae
acute otitis media - S.pneumo most common cause after 3 months old (viral infection or allergies predispose)
acute and chronic sinusitis (viral infection, allergies, mechanical blockage predispose)
P disk on agar innoculation
Streptococcus pneumoniae is suscetpible
Mnemonic: VROPS: Viridans Resistant to Optochin, Pneumoniae susceptible
Where does Haemophilus influenzae usually colonize? How does it differ from infectious HiB?
High carraige rate (50-80%) in URT
Normal flora strains lack capsule
Those isolated from cases of Otitis Media can't be typed - may not be protected by vaccine
Haemophilus influenzae ID
small, gram neg coccobacilli
requires X and V factor for growth
gram neg coccobacilli
normal flora of oropharynx
can cause otitis media
Throat flora in lab
What organism is associated with acute glomerulo nephritis and rheumatic heart disease? How does it contribute to those diseases?
M protein in capsule is cross-reactive with proteins in heart muscle (mostly respiratory strains) and kidney (mostly skin strains)
Can lead to autoimmune attack in those organs.
What are SLO and SLS?
Streptolysins produced by GAS
SLO: O2 labile - only causes B-hemolysis in low oxygen environment
SLS: O2 stable - B-hemolysis in presence of oxygen
What is Spe (A-C)
Streptococcal Pyrogenic Exotoxins type A-C produced by GAS
Spe A produced by minority of bugs
Induce cytokine release, -> fever and rash, ->enhanced sensitivity to endotoxic shock
Toxic Shock Like Syndrome
What is an Aschoff body associated with?
Rheumatic heart disease.
Lesion of lymphocytes and macrophates around fibrinoid deposits in hearts of affected individuals
Cell mediated response
What is the most common bacterial cause of pharyngitis?
must be treated promptly to prevent sequelae including scarlet fever and rheumatic heart disease
How does Diptheria toxin work?
B binds epidermal growth factor precursor -> endocytosis
Reduction in vessicle releases A subunit
A subunit ADP ribosylates elongation factor 2 (NAD + EF2 -> ADPR-EF2 + nicotinomide + H+
EF2 inactivated and translation ceases
How is diptheria toxin genetically regulated?
DT gene is carried by bacteriophages w and B
synthesis negatively regulated by iron - in humans iron is sequestered in RBCs - low levels in tissue where toxin acts
What is the pathogenesis of diptheria?
C.diptheria colonizes human pharynx
Spread by droplet, contact w/ cutaneous infection, or fomite
Causes "punched out" ulcer
Pseudomembrane forms - oropharynx down trachea - can obstruct breathing and -> death
Systemic manifestation: DT Can also attack heart and CNS
Describe the structure and function of pertussis toxin
AB toxin w/ 5 B subunits
A subunit ADP ribosylates Gs -> uncontrolled production of adenylate cyclase and massive increase in cAMP (same action as cholera toxin, but different target cells)
-promotion of lyphocytosis
-diminished oxidative killing by macrophages
How does B.pertussis interfere with ciliary function?
Filamentous hemaglutinin binds cilia of epithelial cells,
Two ways B.pertussis increases cAMP levels in host cells
1: Pertussis toxin: ADP-ribosylation of Gs
2: Bacteria produce invasive AC : enters cell and requires calmodulin for function
Explain regulation of B.pertussis virulence factors
BvgS: transmembrane histidine kinase
-activated at 37C or w/ ionic changes
-phosphorylates BvgA in bacterial cytoplasm
BvgA: transcription factor that controls 20+ genes
-temporal delay due to cascade
-first Fha and pili genes activated
-later Btx and invasive AC genes activated -> cytotoxicity
What systemic effects can B.pertussis have?
edema and hemorrhages in brain
How is B.pertussis identified in the lab?
direct fluorescent Ab assay available, but results should be confirmed w/ culture
Culture: deep nasopharyngeal - plate and culture immediately (poor survival)
Growth on Bordet-Gengou or Charcoal blood agar + Abx media
-slow grow, 3-7 days
Causative organism of malaria
What is the prognosis for untreated cerebral malaria?
if not treated: death in 24-72 hours
How is Legionella pneumophilia spread?
Not spread person to person
Organism exists inside amoebas
reservoirs include AC cooling towers, shower heads, faucets, hospital ventilators
Ubiquitous in nature
Reservoir is aerosolized and inhaled
Diseases caused by Legionella Pneumophilia
Legionnaires disease: severe pneumonia (2-10 days incubation), 60% mortality, nosocomial and community acquired
Pontiac disease: non-pneumonial fever 1-2 days incubation, self-limiting. May be immune response to dead or low virulence strains
Disseminated - rare
How does L.pneumophilia invade and survive within host cells?
coiling phagocytosis (alveolar macrophages) - does not necessitate opsonization
-inhibit phagosome/lysosome fusion
-induction of ribosome/ mitochondria accumulation around vessicle
-iron scavenging from ferritin
-reproduction w/in phagosome, then escape and cell-lysis
When is L.pneumophilia suspected and how is it identified?
Suspected in severe, progressive pneumonia with no known etiological agent
Rarely found in sputum and poor gram stain capability
Identified by ELISA, DNA homology
Gram neg rod
What does acinobacter cause?
severe blood and wound infections in immunocompromised patients
What organism causes "walking" pneumonia?
How is mycoplasma pneumoniae identified?
Rarely found in sputum, does not stain well.
Diagnosed based on presence of complement fixing antibody
-long incubation period, so patient presents with high Ab titer
Describe Mycoplasma's morphology and growth requirements
lacks a cell wall - surrounded by triple membrane containing sterols - requires cholesterol for growth
4 organisms that cause "atypical" pneumonia
What cells does Chlamydia pneumonia infect?
Columnar epithelial cells
Remember - 2 stage life cycle
-Elementary body is infectious (carries adhesin)
-Reticulate body replicates - uses host ATP generating potential
What kinds of respiratory infections are S.aureus responsible for?
Acute pneumonia - secondary to some other insult to lung (influenza)
Empyema - purulent infection of pleural space - from surgery or chest tube
Lung abscess - complication of peumonia - usually involves aspiration of oral or gastric contents
Virulence factors of Mybacoterium tuberculosis
-Mycolic Acid (cord factor) in cell wal
-long chain FA, resists drying and disenfectants,
hypersensitivity granuloma, promotes inflammatory response
(TNFa) - lung tissue dammage
-cell wall glycolipid. suppresses Tcell proliferation and
-Sulfolipids: inhibit lysosome - phagosome fusion in macrophage
-Catalase: degrades H2O2
-Ammonia prod: prevents acidification of phagosome
What does Mycobacterium bovis cause?
Rarely causes TB, found in milk, eradicated through pasteurization.
Infects bone -> hunchback
What causes systemic TB symptoms?
Helpers and cytotoxic Tcells activate alveolar macrophages -> release of cytokines and systemic response (fever, weight loss
What is a tubercle composed of?
Tubercle is a microscopic granuloma containing M.tuberculosis.
Composed of multinucleate giant cells, activated macrophages, lymphocytes
Fates of tuberculosis tubercle
become fibrotic or calcified w/ dead bacteria - visible on CXR
Dormancy - reactivation later
necrotic tubercle may erode to blood vessel -> disseminated disease.
What is the basis of the TB skin test?
Delayed type hypersensitivity- effector Tcells recognize pathogen, attract macrophages -> local inflammation on pos. test
How long does it take for a positive TB test after primary infection? what does a positive test indicate?
Indicates exposure, not necessarily active disease.
6 weeks coincides with tubercle formation
Need CXR to confirm active process
How is TB identified?
Specimen: sputum, biopsy, blood w/ miliary TB (seen on CXR)
Staining of sputum - diagnosis before bacteria will grow.
gram +, but doesn't stain well
Acid fast w/ Fuchsin stain
Culture: condition w/ NaOH - inhibit other bacteria
-24 hr. doubling time - very slow growth
Cystic Fibrosis is associated with what bacterial lung infection?
Initial infection may be S.aureus, later infection w/ Pseudomonas
What organism is involved in Farmer's lung?
Histoplasma capsulatum virulence factors (LRI)
-environmental mold -> infectious conidia
-conversion to pathogenic yeast at 37C
can grow w/in macrophages and survive oxidative burst.
How is H.capsulatum encountered and where is it most prevalent?
Grows in soil w/ abundance of bird and bat droppings.
Most abundant in Mississippi River valley and Ohio River valley
What respiratory disease does Histoplasma capsulatum cause?
Looks like TB - granulomas, necrosis - may disseminate to reticuloendothelial system
How is histoplasma capsulatum diagnosed / identified?
Sputum of no use
Need CXR and biopsy or blood sample
Very slow growth in culture (weeks) - dimorphic - yeast and mold
How does Blastomyces dermatitidis growth differ from Histoplasma?
extracelular growth in lung - too large for phagocytosis
How is Blastomyces dermatitidis identified in the lab?
very slow culture (4wks)
large yeast cells with broad buds
serodiagnosis not very good- cross rxn with many other fungi
What causes Valley Fever? How does pathology work?
Coccidioides immitis - soil fungus
Arthroconidia inhaled (can be phagocytized ) and covert to Spherule (too large for phagocytosis) filled with endospores (can be phagocytized)
Spherules burst -> large Ag release -> large inflammatory response
May induce anergy
What does a negative Coccidioides skin test indicate?
Performed test too soon (takes 1-4 weeks after onset of disease for pos. test)
What is Pneumocystis jiroveci?
Fungus causing PCP pneumonia in immunosuppressed patients
-AIDS, corticosteroids, leukemia
Classification uncertain: morphology - protist, gentic - fungus
Treatment: responds to antiprotozoal therapy - not antifungal
What is characteristic about PCP pneumonia?
Often concurrent infections
Alveoli filled with desquamated cells, organisms, monocytes, fluid - look "foamy"
Diffuse alveolar infiltrates on CXR
Symptomatic diagnosis of Pneumocytosis
Mild low grade fever
progressive dyspnea and tachypnea
Death by asphyxiation
What causes most respiratory infections/
What are mucins?
Protective proteins found in respiratory tract
Bind and occupy viral receptors rendering them unable to infect cells
Influenza is a member of what family? genome description? enveloped?
(-) segmented RNA genome
What are influenza virus subfamilies and what strain causes pandemic flu?
A: pandemic - antigenic shift
B: as serious as A, but no pandemic
C: most common, but causes minor infection - not included in trivalent vaccine
Process of influenza virus infection / replication / release
HA binds sialic acid on cell - receptor mediated endocytosis
reduction in pH (5.3) -> HA conf. change, fusion of virion envelope w/ endosome
M2 channel: H+ entry -> RNA release
RNA -> nucleus -> transcription, replication -> virion assembly
Virion-> cytoplasm -> release by budding
NA: cleaves sialic acid from cell surface to prevent new virion from re-binding cell
What is the major target of influenza drugs?
Olsemtamivir and Zamanivir
Amantidine and Rimantidine bind M2 - don't work on flu B
-most flu strains are resistant
-wide overuse and misuse, esp in Asia
Virus neutralizing antibodies target what protein on infuenza virus?
What Influenza A strains infect humans?
Seasonal flu vaccine contains what 3 viruses?
A: (CA 2009) H1N1pdm09 like
A: (Victoria 2011) H3N2 like
B: Wisconsin 2010 like
What is H5N1?
Have been a few cases of animal (ferret model) -> human transmission, but no human-> human
Being watched as next potential pandemic flu virus
What viruses are in family Paramyxoviridae?
Paramyxovirus: HPIV (Human Parainfluinza Virus) 1 and 3
Rubulavirus: Mumps, HPIV 2 and 4
Pneumovirus: Respiratory Syncytial Virus (RSV)
Metapneumovirus: Human Metapneumovirus (MPV)
What causes Croup and what is it?
Caused by HPIV-1
viral respiratory infection of infants and children
inflammation of larynx, trachea, bronchi
Stridor heard on exam - inspiratory sound
Respiratory distress - medical emergency
Viral cause of larnygitis?
HPIV - in adults and older children
vs. Croup in young children.
Infection and inflammation of bronchioles
Adults - rare
Children - life threatening (esp under 1yr.)
-Usually caused by Respiratory Syncytial Virus
-Also MPV, HPIV-3
May -> pneumonia
What is the most common cause of LRI in children?
MPV probably second.
Mumps virus and symptoms
Swelling of parotid gland (painful), swelling of cheeks and jaw, ear pain, fever and headache.
Less frequent: meningitis, inflammation of testes, rash
Measles virus and symptoms
More severe than mumps
Respiratory spread (14-18 day incubation)
Malaise, cough, coryza, headache, conjunctivitis
Koplik's spots - blue/white on buccal mucosa
Rash 5-7 days, face -> trunk -> limbs
Respiratory spread, 12-23 day incubation
Lymph node swelling, maculopapular rash, arthritis in adult women.
Risk of infection of fetus - congenital rubella syndrome
1st at 12-18 mos, 2nd at 4-6 yrs
Combo of 3 vaccines
What are heterophile antibodies?
Antibodies against unusual antigens to which host may not have been exposed
EBV activates Bcells -> Ab production
African (endemic) form associated with EBV - most common childhood cancer in equitorial Africa
Sporadic form is not
Hairy Oral Leukopenia
Caused by EBV
Oral infection in AIDS patients
Lesions on side of tongue are areas of active viral replication
In a case of pneumonia accompanied by HSV labialis, what is the most likely pathogen?
In a case of pneumonia accompanied by bullous myringitis, what is the most likely pathogen?
What pneumonia causing organisms do not show up in a gram stain?
Rusty colored sputum is a symptom of what pneumonia causing organism?
In mycoplasma pneumonia, where is the focus of infection?
Bronchi - not in alveoli
Infiltrate in lung is due to immune response
What pneumonias have positive urine antigen test?
Common causes and non-causes of nosocomial pneumonia
Gram neg aerobes
Candida commonly cultured - rare cause