SM_181a: Bacterial Infections Flashcards
Streptococcus pneumoniae is a [Gram stain, shape}
Streptococcus pneumoniae is a Gram-positive lancet-shaped diplococci (pneumococci)
What are the determinants of pathogenicity of Streptococcus pneumoniae?
Streptococcus pneumoniae
- Capsule: protects bacteria from phagocystosis, antibodies against them are protective in humans, 80 distinct serotypes
- Pneumolysin: degrades hemoglobin to greenish pigment, may form pores, activates complement
- Peptidoglycan fragments and teichoic acid: activate complement, leading to intense inflammation and tissue damage
- IgA protease
Describe the clinical disease caused by Streptococcus pneumoniae
Streptococcus pneumoniae
- Only infects humans
- Spread person-to-person by small droplets
- Colonizes oropharynx and nasopharnx of some healthy adults and kids
- Most common bacterial cause of community-acquired pneumonia
- Pnuemonia leading to bacteria in the very young and old
- Pneumonia leading to meningitis
- Pneumonia in healthy individuals and those with predisposing conditions
Describe the presentation of Streptococcus pneumoniae
Streptococcus pneumoniae
- Fever
- Cough productive of rusty-colored sputum
- Pleuritic chest pain
- Diminished respiratory excursion (splinting): not taking much effort to avoid pain
- Abrupt onset of symptoms
- Chest radiographs show lobar infiltrates
- May cause empyema
- Frequent cause of otitis media, acute bronchitis, sinusitis
Describe diagnostic testing for Streptococcus pneumoniae
Streptococcus pneumoniae
- Sputum sample: numerous Gram-positive cocci in pairs and chains, many neutrophils, no epithelial cells
- Culture on blood agar: alpha-hemolytic
- Catalase-negative
- Optochin-susceptible
- Pneumococcal urinary antigen test for urine
Describe the treatment for Streptococcus pneumoniae
Streptococcus pneumoniae
- Penicillin, although now there is significant resistance which is often associated with resistance to other antibiotics as well
- Vancomycin, cephalosporins, doxycyline, TMP-SMX, macrolides, clindamycin
- Moxifloxacin effective but cipro is not
Describe prevention of Streptococcus pneumoniae
Streptococcus pneumoniae
- Pneumococcal polysaccharide vaccine (Pneumovax 23)
- Pneumoccocal polysaccharide-protein conjugate vaccine (Prevnar-13): capsular polysaccharide from 13 serotypes conjugated to protein
- Vaccination recommended for young children 2-23 months, adults 65 years or older, all others at risk for pneumococcal infections (diabetes mellitus, chronic lung disease, HIV, etc)
Streptococcus pneumomiae is ______-hemolytic
Streptococcus pneumomiae is alpha-hemolytic
(partial/green hemolysis)
______ of Streptococcos pneumoniae degrades hemoglobin to a ______ pigment
Pneumolysin of Streptococcos pneumoniae degrades hemoglobin to a greenish pigment
Sputum sample shows Gram-positive cocci in pairs and chains along with many neutrophils. The organism is ________
Sputum sample shows Gram-positive cocci in pairs and chains along with many neutrophils. The organism is Streptococcus pneumoniae
Most common cause of community-acquired pneumoniae is ______
Most common cause of community-acquired pneumoniae is Streptococcus pneumoniae
Pneumonia from Streptococcus pneumoniae can cause _____ in very young and old people
Pneumonia from Streptococcus pneumoniae can cause bacteremia in very young and old people
Haemophilus influenzae is a [size, Gram-stain, shape]
Haemophilus influenzae is small Gram-negative coccobacilli
What are the determinants of pathogenicity of Haemophilus influenzae?
Haemophilus influenzae - polysaccharide capsule
- Six types (a-f), antiphagocytic
- Type b caused most serious disease but becoming less common with routine use of vaccination
- Type specific antibodies are protective
- Encapsulated H. influenza primarily infects children because most adults have protective antibodies
- Unencapsulated strains often isolated from adults and children
Describe the clinical disease caused by Haemophilus influenzae
Haemophilus influenzae
- May colonize the upper respiratory tract of healthy individuals
- Spread by airborne droplets or by direct contact with secretions
- Frequent cause of otitis media, sinusitis, community-acquired pneumonia, bronchitis, conjunctivitis, meningitis in children under age of 6, septic arthritis in children, may cause life-threatening epiglottitis
_______ may cause life-threatening epiglottitis
Haemophilus influenzae may cause life-threatening epiglottitis
_______ is the radiographic sign you would see in a patient with epiglottitis from Haemophilus influenzae
Thumb sign is the radiographic sign you would see in a patient with epiglottitis from Haemophilus influenzae
Haemophilus influenzae _____ grow on sheep blood agar
Haemophilus influenzae does not grow on sheep blood agar
(needs hemin and NAD which sheep blood agar does not have)
Haemophilus influenzae requires ______ and ______ for growth
Haemophilus influenzae requires hemin (X factor) and NAD (V factor) for growth
(can grow on chocolate agar)
Haemophilus influenzae can grow on ______ agar
Haemophilus influenzae can grow on chocolate agar
contains hemin (X factor) and NAD (V factor)
Describe treatment of Haemophilus influenzae
Haemophilus influenzae
- Ampicillin, amoxicillin, or penicillin G not effective against beta-lactamase producing strains (25%)
- Cephalosporins, TMP-SMX, macrolides, amoxicillin/clavulonic acid, and quinolones
Prevention of Haemophilus influenzae involves _______
Prevention of Haemophilus influenzae involves Type B capsular conjugate vaccine (Hib)
- Given to all infants starting at 2 months of age
- Dramatically reduced incidence of Haemophilus influenzae meningitis in infants and children
Describe Mycoplasma pneumoniae
Mycoplasma pneumoniae
- Extracellular pathogen
- Lacks cell walls
- Pleimorphic in shape
- Smallest organisms that can be free-living in nature and self-replicating on laboratory medium
Mycoplasma pneumoniae is an ______ pathogen and lacks ______
Mycoplasma pneumoniae is an extracellular pathogen and lacks cell walls
(pleimorphic in shape)
Describe the pathogenesis of Mycoplasma pneumoniae
Mycoplasma pneumoniae tightly adheres to respiratory epithelium via protein adhesin P1
Mycoplasma pneumoniae tightly adheres to _______ via _______
Mycoplasma pneumoniae tightly adheres to respiratory epithelium via protein adhesin P1
Describe the clinical disease caused by Mycoplasma pneumoniae
Mycoplasma pneumoniae
- Person to person spread by airborne small droplets
- May cause pharyngitis, rhinorrhea, acute bronchitis, or community-acquired pneumoniae
- Causes atypical pneumoniae: gradual onset, cough without sputum, common in young people aged 5-20, usually mild disease (walking pneumoniae), non-lobar on chest radiographs
Mycoplasma pneumoniae causes ______ pneumonia
Mycoplasma pneumoniae causes atypical pneumoniae
- Gradual onset
- Cough without sputum
- Common in young people ages 5-20 years
- Usually mild disease (walking pneumonia)
- Non-lobar infiltrates on chest radiographs
Describe the clinical presentation of someone with Mycoplasma pneumoniae
Mycoplasma pneumoniae
- Fever
- Headache
- Malaise
- Sore throat
- Non-productive cough
- Occasionally pneumonia accompanied by neurologic abnormalities (encephalitis), skin rashes, hemolytic anemia
Pneumonia accompanied by hemolytic anemia is caused by ______
Pneumonia accompanied by hemolytic anemia is caused by Mycoplasma pneumoniae
Classic CXR pattern of someone with ______ is diffuse reticulonodular or interstitital infiltrates
Classic CXR pattern of somone with Mycoplasma pneumoniae pneumonia is diffuse reticulonodular or interestitial infiltrates
(but any pattern can be seen)
Describe diagnostic testing for Mycoplasma pneumoniae
Mycoplasma pneumoniae
- Cultured from pharynx or sputum - requires sterols for growth
- Rise in specific antibody titers in the blood
- Cold hemagglutinins may be seen in 50% of patients: antibodies directed against mature RBCs that cause reversible agglutination at 4ºC
_______ may be seen in the diagnostic testing of many Mycoplasma pneumoniae patients
Cold hemagglutinins may be seen in the diagnostic testing of many Mycoplasma pneumoniae patients
(antibodies directed against mature RBCs that cause reversible agglutinations at 4ºC)
Describe the treatment of Mycoplasma pneumoniae
Mycoplasma pneumoniae
- Macrolides, tetracycline/doxycycline, quinolones
- Penicillins not active (no cell wall)
_____ are not active against Mycoplasma pneumoniae because they do not have a ______
Penicillins are not active against Mycoplasma pneumoniae because they do not have a cell wall
Describe prevention of Mycoplasma pneumoniae
Mycoplasma pneumoniae
- None (no vaccine)
Chlamydia pneumoniae is [location]
Chlamydia pneumoniae is obligate intracellular
(closely related species are Chlamydia trachomatis which causes STDs and Chlamydia psittaci which causes pneumonia contracted from birds)
Describe the clinical disease caused by Chlamydia pneumoniae
Chlamydia pneumoniae
- Community-acquired pneumonia: atypical pneumonia
- Relatively common (5-20%) cause of pneumonia in young adults
- Pneumonia often accompanied by pharyngitis
- Chest radiographs resemble those of patients with Mycoplasma pneumonia
Describe diagnosis of Chlamydia pneumoniae
Chlamydia pneumoniae
- Acute and convalescent antibody titers
Describe treatment of Chlamydia pneumoniae
Chlamydia pneumoniae
- Macrolides and tetracycline/doxycycline
Describe prevention of Chlamydia pneumoniae
Chlamydia pneumoniae
- None (no vaccine available)
Staphylococcus aureus are [Gram-stain, shape, appearance]
Staphylococcus aureus are Gram-positive cocci that may have a gold appearance
- Cause of community-acquired pneumonia and nosocomial pneumonia
- MRSA
- Treat with nafcillin/oxacillin (vancomycin or linezolid if MRSA)
Legionella pneumophila resembles [Gram-stain] but does not take up Gram-stain
Legionella pneumophila resembles Gram-negatives but does not take up gram stain
Legionella pneumophila causes ________
Legionella pneumophila causes Legionnaire’s disease
- May be community-acquired or hospital-acquired
- Considered an atypical pneumonia
- May be quite severe, with high fevers (greater than 40ºC)
- Associated with water, air conditioning systems, and cooling towers
- Treatment: macrolide or fluoroquinolone
Describe aspiration pneumonia
Aspiration pneumonia
- Seen in patients with depressed gag reflex: elderly patients, seizures, alcoholic blackouts
- Clinical presentation: cough, fever, malaise, foul-smelling sputum
- CXR: consolidation on dependent lung fields
- Causative organisms are pharyngeal flora: Prevotella, Fusobacterium, anaerobic cocci
- May evolve into lung abscesses or empyema
Patient has pneumonia with pleuritic chest pain. The causative organism is ________
Patient has pneumonia with pleuritic chest pain. The causative organism is Streptococcus pneumoniae
Gram-negative rod that is oxidase positive is ________
Gram-negative rod that is oxidase positive is Pseudomonas aeruginosa
Which organisms can cause ventilator-associated pneumonia?
Ventilator-associated pneumonia
- Staphylococcus aureus
- Enterobacteriaeceae (Escherichia coli, Klebsiella pneumoniae, Enterobacter spp., Serratia spp.)
- Legionella pneumophila
- Pseudomonas aeruginosa
- Acinetobacter baumannii
- Mixed anaerobic bacteria
- Aspiration pneumonia
Describe the Enterobacteriaeceae (Escherichia coli, Klebsiella pneumoniae, Enterobacter spp., Serratia spp.)
Enterobacteriaeceae (Escherichia coli, Klebsiella pneumoniae, Enterobacter spp., Serratia spp.)
- Gram-negative rods
- Oxidase negative
- Many inhabit the human GI tract
- May colonize the oropharynx in hospitalized patients -> HAP or VAP
- Hospital-acquired organisms tend to be resistant to multiple antibiotics
Describe Pseudomonas aeruginosa
Pseudomonas aeruginosa
- Gram-negative, aerobic bacilli
- Common cause of HAP and VAP
- Resistant to many antibiotics: must check susceptibilities for definitive treatment regimen
Describe Acinetobacter baumannii
Acinetobacter baumannii
- Gram-negative, aerobic bacillus or coccobacillus
- Causes HAP or VAP
- Resistant to many antibiotics
- 50% of isolates may be resistant to carbapenems
Which organisms caise acute bronchitis/tracheitis?
Acute bronchitis/tracheitis
- Streptococcus pneumoniae
- Haemophilus influenza
- Mycoplasma pneumoniae
- Chlamydia pneumoniae
- Bordetella pertussis
Describe Bordetella pertussis
Bordetella pertussis
- Tiny gram-negative coccobacilli, strict aerobe
- Cause of whooping cough
- Secretes pertussis toxin
- Historically a disease of children but recently outbreaks among adults have been repoted
Describe Corynebacterium diphtheria
Corynebacterium diphtheria
- Gram-positive bacilli, club-shape
- Diphtheria toxin (DT): ADP-ribosylating EF-2
- Causes diphtheria: patients (historically children) present with sore throat and fever, difficulty swallowing, cough, hoarseness, rhinorrhea - oropharyngeal pseudomembrane may lead to airway obstruction
Oropharyngeal ______ is characteristic of CCorynebacterium diphtheria infection
Oropharyngeal pseudomembrane is characteristic of Corynebacterium diphtheria infection
(may lead to airway obstruction)
Gram-positive cocci causing alpha-hemolysis: ________
Gram-positive cocci causing alpha-hemolysis: Streptococcus pneumoniae
Atypical pneumonia, hemolytic anemia, neutrophils and no growth on sputum: _______
Atypical pneumonia, hemolytic anemia, neutrophils and no growth on sputum: Mycoplasma pneumoniae
Air conditioner repair man, high fever, CXR shows bilateral patchy infiltrates, no growth on culture: _______
Air conditioner repair man, high fever, CXR shows bilateral patchy infiltrates, no growth on culture: Legionella pneumophila
Homeless, blood-tinged sputum, weight loss, right upper lobe rhonchi: _________
Homeless, blood-tinged sputum, weight loss, right upper lobe rhonchi: Mycobacterium tuberculosis
