Respiratory tract infections Flashcards
Upper tract infections
Many isolates considered pathogenic are also considered to be colonizers depending upon culture predominating organisms. 60% of children carry S. pneumoniae by 2 y.o. The samples easily contaminated with NF. Nasal carriage cultures only for: MRSA
Immunocompromised screening for Aspergillus spp. or Mucor spp.
Lower tract infections
Infections are 6th leading cause of death in US, approximately 500,000 hospitalizations/year
40-60% of cases no pathogenic organism isolated
Common organisms causing lower respiratory tract infections (3)
- Mycoplasma pneumoniae - most common cause of community acquired pneumonia (CAP)
- Chlamydia pneumoniae, 2nd most common CAP
- Haemophilus influenzae 3rd, Legionella 4th
Clinical conditions associated with the respiratory tract (15)
- Candidiasis
- Cystic fibrosis
- Diptheria
- Epiglottitis
- Pharyngitis
- Laryngitis/bronchiolitis
- Lemierre’s disease
- Otitis externa
- Otitis media
- Chronic bronchitis
- Pneumonia - community and hospital acquired
- Empyema
- Lung abscess
- Sinusitis
- Nasopharyngeal screening
Mechanisms of transmission for respiratory tract infections (6)
- Person to person- airborne or contaminated secretions
- Environmental reservoirs
- Aspiration of endogenous flora
- Trauma
- Animal reservoirs
- Fomites
Epidemiology
Seasonal, travel, community information- epidemics, outbreaks or known exposures, eg. contacts of known TB cases
Structures of the upper respiratory tract (4)
- Nose
- Sinuses
- Throat
- Pharynx
Structures of the lower respiratory tract (3)
- Trachea
- Bronchial tree
- Lung parenchyma
Structures of the bronchial tree (3)
- Bronchus
- Bronchiole
- Alveolus
Other associated locations with the respiratory tract (2)
- Middle ear
- Eye
Colonization
Presence of an organism on epithelial cells of host without causing harm.
Infection
Process caused by growth of an organism which invades host tissues resulting in disease.
Normal respiratory flora species (8)
- S. pneumoniae
- S. aureus
- M. catarrhalis
- N. meningitidis
- Group B, C and G streptococci
- Order - Enterobacterales
- Acinetobacter, Stenotrophomonas
- Corynebacterium spp.
General considerations- lower respiratory tract
If less than normal flora, no identification needed, report as normal respiratory flora. If there are more than normal flora- full identification and sensitivity testing is required
Organisms to identify regardless of quantity (11)
- Group A streptococci
- Brucella
- Francisella tularensis
- Yersinia pestis
- Bacillus anthracis
- Pasteurella spp.
- P. aeruginosa
- Rhodococcus equi
- Actinomyctes, Norcardia spp. and Streptomyces
- Yeasts & molds not considered contaminants
- many others…Legionella, Mycobacteria, PCP, viruses
Specimens for candidiasis
swab of buccal mucosa, tongue or oropharynx
Specimens for cystic fibrosis
Young children- deep throat specimens
Specimens for diphtheria
nasopharyngeal swab
Specimens for epiglottitis
blood culture
Specimens for Pharyngitis
throat swab
Specimens for Lemierre’s disease
blood culture, starts as tonsillar abscess
Specimens for otitis externa
swab of inner ear canal
Specimens for otitis media
tympanocentesis fluid
Specimens for sinusitis
sinus aspirate
Nasopharyngeal screening samples
swab of nares
Diphtheria
Caused by C. diphtheriae. Acute, toxin-mediated disease (ADP-ribosylating toxin, interferes with protein synthesis, necrosis). Only strains infected with Beta phage produce the toxin and are pathogenic. Diphtheria is an upper respiratory infection with systemic toxin effects. Symptoms include sore throat, dysphagia, malaise, headache, fever, nausea.
What causes death in Diphtheria patients?
Obstruction of the airway by the pseudomembrane. There is a 10% mortality rate. Myocarditis -toxin adheres to myocardial, kidney and nerve tissue). CNS involvement is possible
Diphtheria diagnosis
Any throat or nasopharyngeal swabs for collection. Media - BAP, Cystine tellurite blood agar, Tinsdale agar (NOT FOR primary plating), or Loeffler agar. Incubate for 24 to 48 hours , aerobically NOT in 5% CO2. ID any beta hemolytic colonies on BAP, dark colonies on CTBA, dark zone around colony on Tinsdale agar. Pleomorphic GPR, Catalase+, Nonmotile, CAMP-neg, Urea-negative, halo on TINS = presumptive ID
Diphtheria treatment (3)
- First line – penicillin
- Second line – erythromycin
- Alternate - first generation cephalosporin or rifampin
Epiglottitis
Most commonly found in pre-school age children 2 to 4 y.o., experiencing acute respiratory distress. It is an infection of the epiglottis and surrounding soft tissues in upper airway. Intubation or endotracheal tube may be required due to swelling. S&S -fever, severe sore throat, difficulty swallowing, swollen red, edematous epiglottis, abrupt onset of fever, & drooling. There is a croup-like cough NOT found with epiglottitis, tonsillar or pharyngeal exudate absent.
Diagnosis of epiglottitis
Visualization of the epiglottis is important for diagnosis, need supportive care available due to risk of suffocation. The diagnosis can be made by epiglottis culture and blood culture
Organisms causing epiglottitis (5)
Haemophilus influenzae type B, non-typeable Haemophilus influenzae, S. aureus, S. pneumoniae, Group A strep
Treatment of epiglottitis
Hospitalization and IV treatment with beta-lactamase resistant antibiotics
Pertussis (Whooping cough) stages of infection
Caused by Bordetella pertussis. Other Bordetella species include B. parapertussis and B. bronchiseptica
Stages of infection:
1. Catarrhal stage: 1-3 week incubation period. Highly communicable
2. Paroxysmal stage: 1-4 weeks – severe repetitive cough resulting in whooping during this stage
3. Convalescent (recovery) weeks to months later – reduced frequency of coughing spells
Pertussis diagnosis
Isolated from the posterior nasopharynx. Use PCR, DFA. Media:
Regen-Lowe, Bordet-Gengou, BCYE
ID – “mercury drop” colonies, SBA(SBAP)-, Ox +
Pertussis treatment
Treat patient and contacts with erythromycin
Pharyngitis
Found in school age children, group A streptococci is found in 15 to 30% of patients, much less frequent in adults. Most commonly find viral cause of illness. Symptoms- pharyngeal exudate, fever, lymph adenopathy, NO cough
Streptococcus pyogenes
Includes group A streptococci; ß-hemolytic strep. Post-streptococcal sequelae: rheumatic fever & glomerulonephritis. Streptococci groups C & G and Arcanobacterium haemolyticum. Need to rule out infection with Neisseria gonorrhoeae or Corynebacterium diphtheriae. Treatment- penicillin, macrolides
Lemierre’s disease causative agents (4)
- Most common causative agent Fusobacterium necrophorum
- Bacteroides melanogenicus, Eikenella corrodens, non group A strep
Fusobacterium necrophorum
The most common causative agent of Lemierre’s disease. However, it is normal anaerobic flora, found in genital, GI, and upper respiratory tract.
Lemierre’s disease
Was commonly found in the pre-antibiotic era (1950s), but is still associated with a high mortality rate. Responsible for severe infection in children and young adults that begin as peritonsillar abscesses. The patient first has pharyngotonsillitis or associated with infectious mononucleosis. Proceeds to a localized infection that spreads to the neck and jugular vein septic thrombophlebitis. Progression to pleural effusion with empyema, metastatic abscesses (lung, liver, joints) resulting from bacteremia. Patient with pharyngitis and jaundice possible case.
Rhinitis
Inflammation of the mucous membranes in the nose. Main symptom is rhinorrhea - runny nose. When not allergy, usually caused by a virus. There is a 2-3 day incubation period. Symptoms: sneezing, nasal stuffiness, coryza, and scratchy throat. May be complicated by bacterial sinusitis or otitis media.
Laryngitis/bronchiolitis
Often has a viral cause. A cough is the most important symptom; fever may occur with influenza virus, adenovirus, or M. pneumoniae. It is important to distinguish from pneumonia. May cause cute exacerbations of chronic bronchitis. S. pneumoniae, S. aureus (including MRSA), GNR and respiratory virues