Virus summary
Virus |
family |
Epi |
Pathogenesis/signs/symptoms |
Diagnosis/ Treatment/ control |
Miscellaneus |
---|---|---|---|---|---|
Rhinovirus |
Picornaviridae class IVa |
Human->human year round infection 110 serotypes |
Binds ICAM. Endocytosed. Goes to URT and rarely LRT. |
Nonspecific PH. No vaccine |
|
coronavirus |
Class IVb |
Human only. Peak incidence in winter, spring. Unknown serotypes |
URT only. Low grade fever, rhinorrhea, cough, sneezing, runny nose. |
Alpha-interferon vaccination not practical ELISA, IF |
|
Adenovirus |
Adenovirus Class I |
> 100 serotypes 2 antigenic determinants fibre has a specific HA determinant respiratory + fecal transmission worldwide, temperate zones. ARD transmitted by resp droplets |
Pharynx and tonsils. Fever, cough, vomiting, coryza, diarrhea, meningeal signs and pulmonary infiltrates. Antibodies against Serotypes 1, and 2 by age 2 pharyngo-conjuntival fever (PCF) (serotypes 3, 7) |
Topical alpha-interferon vaccines for serotypes 3,4,7,21
|
|
Parainfluenza |
Paramyxovirus class V |
|
Pharynx and tonsils |
|
|
RSV |
Paramyxovirus Class V |
|
Pharynx and tonsils |
|
|
Bacterial infections
URT defenses |
Lysozyme, lactoferrin, sIgA. Mucociliary escalator |
LRT defenses |
IgA and IgG, complement components, macrophages, Mucociliary escalator (not in alveoli) |
Uncommon infections |
C. diphteriae, K. pnemoniae, Pseudomonas spp., E. coli, C. albicans (is present in URT) |
Predisposing factors |
Damage to mucociliary cleaning mechanisms, irritants, intubation or other by-passing of normal defenses, general anaesthesia, inherited factors (cystic fibrosis), age |
Professional pathogens |
Capable of infecting healthy RT, adhere to normal mucosa, interfere w/ action of cilia, evade removal, damage local tissue |
Secondary pathogens |
Require impaired host defenses. Initial damage to RT, Chronic bronchitis, depressed immune response, or depressed resistance --> impared defenses. |
URT infections |
Conjunctivits, otitis media, sinusitis, Streptococcal pharyngitis, epiglottitis, diphtheria, bronchitis |
LRT infections |
Pneumonia, whooping cough, bronchitis?? pg 25-4 and 25-1 conflict |
Eye defenses |
Washing effect of tears (contain lysozyme) |
Eye infection transmission |
Poor hygiene, fomites, use of poor contact lens hygiene |
Eye infection symptoms |
Sore itchy eyes, purulent discharge, reddened conjunctiva |
Eye infection pathogens |
H. influenzae, S. pneumoniae, S. aureus |
Eye infection treatment |
Antibiotic drops and ointments |
Otitis media |
Mostly children 6-36 months. Edema and blockage of eustachian tube w/ impaired drainage of middle war fluid. Caused by S. pneumoniae, H. influenzae, S. aureus, beta-hemolytic streptococci. H. influenzae is MOST COMMON |
Otitis media symptoms |
Fever, headache, reddened bulging eardrums, if untreated -> drum perforation and purulent discharge. |
Chronic otitis media |
Fluid persists for weeks to months “glue ear” |
Acute otitis media |
form Common as a complication of thinovirus infection because normal flora become trapped in middle ear |
Otitis media diagnosis |
Gram stain & morphology. Catalase production – streps from staphs. Chocolate agar w/ C and V factors (H. influenzae) |
Acute sinusitis |
Range of secondary bacterial invaders same as for other URTIs. Blockage of eustachian tubes or openings of sinuses --> no mucociliary clearance --> local accumulation of inflammatory bacteria --> more swelling. H. influenzae is the MAJOR CAUSE in CHILDREN. Pneumococci also can cause it |
Sinusitis diagnosis |
Clinical features, microscopy and culture of aspirated pus (sinus puncture not usually carried out). |
Sinusitis treatment |
Elevation of head and decongestants |
Acute epiglottitis |
Most serious. Can be rapidly fatal. Destruction of airways due to swelling of epiglottis and surrounding structures. Most common in young children. Characterized by acute inflammation, edema and neutrophil infiltration. Initial low grade fever --> elevated temperature (39.5), sudden onset of breathing difficulties. H. influenzae is the most common cause. Severe invasive disease particularly associated w/ capsular ype B. Others of the 6 capsules can be present as local flora |
Haemophilus influenzae in epiglotittis |
Common component of URT microflora. G- coccobacillus. Facultative anaerobe. Polysaccharide capsue, IgA protease, naturally competent (transformation), produces catalase. Vaccine available. Diagnosis by culture on chocolate agar. Detection of capsular antigen (latex agglutination), radioimmunoassay. Can be prevented via vaccine, polyribose-ribitol phosphate coupled to protein carrier, T-cell response, can induce T-cell response in children as young as 2 months |
Pharyngitis |
Pharyngitis is the most common type of S. pyogenes infection. Can also be caused by C. diphtheriae, H. influenzae, N. gonorrhea. Severe purulent inflammation of oropharynx and tonsils. White exudate; enlarged erythematous tonsils, swollen anterior cervical nodes. Throat discomfort, malaise, fever, and headache. Complications include scarlet fever, rheumatic fever and acute glomerulonephritis, and invasive group A streptococcal diseasse |
Scarlet fever |
Complication of pharyngitis. Punctuate erythematous rash (sunburn-like) on neck, trunk and extermities. Spread of erythrogenic toxin |
Group A Streptococci |
S. pyogenes. Lancefield classification according to cell wall carbohydrate. Virulence factors streptokinase, hyaluranidase, hemolysins. Pharyngitis most common infection. Diagnosis on blood agar. Characteristic small opalescent colonies. Beta-hemolytic, bacitracin sensitive, optochin resistant. Antigen detection kits available. Rapid eradication of organism can prevent development of rheumatic fever. |
Diphteria |
Corynebacterium diphteriae. Vaccination makes this rare. Early diagnosis is critical. Block ADP-ribosylation of EF-2. 1B:1A toxin. Symptoms: swollen “bull” neck, temporary facial and neck paralysis, Greyish pseudomembrane, enlarged cervical lymph nodes. Heart, muscle, kidney, liver and other organ irregularities. Only toxin producing strains are virulent. Foreigners and unvaccinated people susceptible. Presence of a pseudomembrane. |
Tinsdale agar |
Contains potassium tellurite which inhibits growth of RT flora other than diphteria |
Precipitate bands |
Elek immunodiffusion test. Sterile filter paper impregnated w/ diptheria antitoxin is imbedded in agar. Isolates of C. diphteria streaked across plate. If toxin present, toxin diffuses away from bacteria and reacts w/ antitoxin --> lines of precipitin |
Pertussis |
Whooping cough. Caused by Bordetella pertussis. Exclusively human. Highly infectious. Adults provide main reservoir. Highly communicable amongst susceptible infants. Life threatening in infants w/ cardiac or pulmonary disease. Complications: CNS anoxia, exhaustion, secondary pneumonia. Incubation period of 1 to 3 weeks |
Neurologic sequelae |
Can be caused by pertussis |
B. pertussis |
Gram negative rod. Inhaled in respiratory droplets coughed by infected individuals. Bind to cilia of epithelial cells. Mediated by Fha (filamentous haemagglutinin). Number of virulence factors: pertussis toxin (1A:5B). Tracheal cytotoxin (inhibits ciliated epithelial cells). Diagnosed w/ FA test |
Bronchitis |
Inflammation of the tracheobronchial tree. Increase in mucus-producing goblet cells. May see impairment of mucociliary mechanisms. Can be of bacterial or viral origin. Acute and chronic forms. Acute: cough is most prominent symptom. Chronic: cough and excessive mucous. |
Chlamydia pneumoniae |
Small, obligate intracellular parasite. Community acquired respiratory tract infections. 50% of adults in US have antibodies to this organism. Infections of both upper and lower RT. Rarely causes invasive disseminated infections. Serologic tests and culturing usually not available. Use giemsa stain, immunofluorescence, FA stain, ELISA and DNA hybridization. |
Mycoplasma pneumoniae |
Increased incidence in late fall and winter. Virulence factor: P1 cytoadhesion. Culture on supplemented agar: small, “mulberry” shaped colonies (corrected from notes). Diagnosis via culture requires 8-15 days. Serologic test more frequently used. Complement fixation. 4 fold rise in tites. False positives can result from infectious mononucleosis, rubella, influenza, adenovirus, listeria infections |
Croup v. epiglottis
Croup vs. epiglottitis |
Croup |
epiglottitis |
---|---|---|
Onset |
Prodormal period 1-7 days |
Rapid: 4-12 hours |
Seasonal occurance |
Late autumn and early winter |
None |
Typical age |
3 months to 3 years |
1 to 6 years |
Clinical manifestations |
Barking, seal like cough, coryza, low-grade fever, insipiratory and expiratory stridor |
Dysphagia, drooling, muffled voice, high fever, inspiratory stridor |
Treatments for various infections
Infection |
Treatment |
Notes/prevention |
---|---|---|
Pharyngitis |
Penicillin G |
Resistance not yet observed in S. pyogenes |
Epiglottitis |
Ampicillin |
Rifampcin for close contacts. prevention = Hib vaccine |
Diphteria |
Erythromycin, penicillin G |
Antitoxin. Vaccine = DPT vaccine |
Otitis media |
Amoxycillin |
|
Sinusitis |
Ampicillin, amoxycillin |
|
Pertussis |
erythromycin |
|
C. pneumoniae (bronchitis) |
Doxycycline or azithromycin |
|
M. pneumoniae (bronchitis) |
Doxycycline or erythromycin |
|
Whooping
cough symptoms
Signs/symptoms |
Incidence in adults |
children |
---|---|---|
Protracted paroxysmal coughing (worse at night) |
100 |
100 |
SOB during coughing |
86*** |
0 |
Tingling sensation in throat |
86*** |
0 |
Sleep disturbed by cough |
57 |
100*** |
Whoop soung with cough |
7 |
40 |
Cyanosis with cough |
0 |
40 |
Pneumonia
Pneumonia |
Infection of the lung paranchyma. Most common cause of infection related death. Overwhelming inflammatory response (which gives pathology). Influx of fluid into the lung alveoli. Interferes w/ gas exchange. |
Signs/Symptoms |
Fever, general feeling of sickness, chest pain – frequently pleuritic, cough (productive/non-productive), SOB, rapid respiration, poor colour, cyanosis, rales, shadowy infiltrate on CXR. |
CXR |
Chest X-ray |
Systemic effects |
Fever, shock, wasting |
Local effects |
Interference of lung function |
Pneumococcal pneumonia |
Can heal w/ no scar formation. |
G- rods |
Permanent lung tisse destruction |
Anaerobic bacteria |
Permanent lung tisse destruction |
Anatomical involvement |
Lobar v. bronchopneumonia |
Lobar pneumonia |
Most commonly pneumococci than with Staphylococci |
Epidemiological markers |
Hospital/nursing home, chronic lung disease, elevated neutrophil count = bacterial infection, age, onset and course, anatomical involvement (lobar or bronchiole) |
Streptococcus pneumoniae |
CAP. Follows URTI. Occasional cause of pneumonia. Normal flora in 5-40% of healthy individuals. Causes lobar pneumonia. Spreads between the alveoli until contained by anatomical barriers. Highest incidence in children < 5 years of age and adults > 40. high incidence in African Americans and native americans. Penicillin resistant (altered target). |
Mycoplasma pneumoniae |
CAP, young adults, summer & fall. Gradual onset, nonspecific symptoms. Flu like symptoms progessing to Dry/scantily productive cough. Earache, CXR: patchy, diffuse bronchopneumonia (involves > 1 lobe). No gram stain (no cell wall). Nucleic acid hybridization test. Culture may require 7-10 days. **ELISA is prefered choice. Complement fixation also possible. Does not have “Fried egg” colonies, but mulberry shaped colonies. Probably won't be sick enough to require hospitalization. |
Haemophilus influenzae |
G- bacilli (is actually pleiomorphic). CAP, Follows URTI. Part of normal flora. Also causes epiglotittis, otitis media, and meningitis. DOES NOT CAUSE INFLUENZA. Type b (capsule) most virulent. Median age of infection is 1 year. False-negatives and false-positives common. Component of normal flora. Diagnosis via chocolate agar w/ X and V factors. IF detection of capsular antigens. |
Chlamydia pneumoniae |
CAP. Lobar pneumonia. Small gram -. obligate intracellular parasite. General symptoms: Headache, fever, cough (non-productive), mialgia. Chronic infections associated w/ cystic fibrosis, lung cancer, and asthma. Can not gram stain. Giemsa stain for intracytoplasmic inclusions. **Complement Fixation (CF) test is most widely used. ELIA and Fluorescent antibodies also available. |
Staphylococcus aureus |
CAP & NAP. Associated w/ influenza. Part of normal flora. Necrotizing pneumonia |
Klebsiella pneumoniae |
CAP & NAP. Chronic alcoholics, diabetes, COPD. Necrotizing pneumonia. Carried by 5% of healthy individuals. Has a large capsule. See a lot of damage to lung tisse. Most damage due to endotoxin. Positive to V-P reaction and citrate reaction. Culture is pink, very viscous, muccoid colonies. |
Moraxella catarrhalis |
CAP & NAP. Pre-existing lung disease |
Escherichia coli |
NAP |
Legionella pneumophila |
CAP & NAP. Exposure to contaminated source. Multi-system symptoms. Develops in 1-5% of people exposed to common source. Early symptoms non-specific: fever, myalgia, malaise, anorexia. System ic effects: Watery diarrhea (25-50% of cases), nausea, vomiting. Severity and range of associated symptoms varies widely. Much of local damage due to host inflammatory response. Virulence factors:intracellular growth, possibly endotoxin , and possibly extracellular protease. Can be picked up from water fountains or from tap water, showers, air conditioners. Predisposing factors: men, immunocompromised, age, heavy alcohol consumption, debilitation, exposure to contaminated source. |
Pathogenesis of pneumococcal pneumonia |
S. pneumoniae infection --> outpouring of fibrinous edema fluid into alveoli, early (red) consolidation (red cells and leukocytes) (good growth medium for bacteria) --> late (grey) consolidation (consolidation of portions of lung (alveolar walls remain intact) macrophages and cell debris) --> resolution. |
S. pneumoniae virulence factors |
Capsular polysaccharide (85 serotypes... now 90). IgA protease, or no toxin |
Pneumococcal pneumonia diagnosis |
Initially dry cough --> purulent, blood-streaked or rusty sputum. Diagnosis by nasopharyngeal swab: culture on blood agar: G+; pairs. Alpha-hemolytic, growth inhibited by optochin, Quellung test, coagulase negative |
Vaccination against pneumococcal pneumonia |
“polyvalent” capsular polysaccharide vaccine. Immunizes against 23 (85-90% of infections) of the most common serotypes. Heptavalent conjugate vaccine: 7 pneumococcal antigens conjugated to CRM197. |
CRM197 |
Mutant non-toxic diphteria toxin. Can be bound to pneumococcal antigens for vaccination |
Chlamydia psittaci |
Causes pneumonia following contact w/ sick birds. Can get pneumonia from this organism. Bird handlers. |
Differentiating L. pneumophila |
Gram stain to demonstrate neutrophils. Gimenez stain (intracellular). Culture from RT. Buffered charcoal yeast extract agar (BYCE). Supplement w/ L-cysteine; low sodium. Detection: all approaches have limited sensitivity. DFA test. Radioimmunoassay (antigen in urine) |
Necrotizing pneumonia |
>1 area of lung parenchyma replaced by cavities filled with debris. Large % of cases involve anaerobic bacteria and can be polymicrobial (grow in the center of biofilm). Aspiration of oropharyngeal contents into lungs (occurs w/ seizure, drug overdose, and excessive alcohol intake). Breathe has putrid smell. Fever of several weeks duration. Cough. |
Pseudomonas aeruginosa |
Gram – rod. Common oppurtunistic pathogen widely distributed. Culture in simple media: produces pyocyanin (yellow-green pigment). Oxidase positive. |
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