Lecture 3: Diseases of the Respiratory System Flashcards
Respiratory system
most common port of entry for many infectious agents
Upper respiratory tract resident microbes (3)
function
streptococcus pnuemoniae, haemophilus, influenzae, and staphylococcus aureus
function: provide barrier to pathogen entry and growth
Lower respiratory tract microbes
smilar to upper respiratory tract but decreased in number
Upper respiratory defenses (2)
defenses limit microbe colonization of the lower respiratory tract with both chemical and mechanical defenses
- mucociliary= clearance involves entrapment of microbes and particulates in a layer of mucous
- antimicrobial substances= lysozyme, lacterrin, antibodies and human defensins
Mucociliary Clearance
defense of upper respiratory system
- mucous secreted from goblet cells in the airway epithelium (made of glycoproteins)
- microbes and particulate matter are trapped in the mucous
- ciliated epithelial cells moved trapped matter toward the pharynx in the mucocilliary ladder
- trapped matter is cleared by swallowing or expectorating
- primary mechanism for keeping microbes out of lungs*
Goblet cells
cells in the upper respiratory system that sectrete mucous
Microbial ecosystem and respiratory health
commensal bacteria may inhibit growth of pathogenic strains by competing for adhesion receptors on mucosal surfaces as well as nutrients
certain commensal species may promote low-level inflammation and increase susceptibility to pathogenic strains
commensal strains may influence abiotic components like acidity and oxygen availability which would inhibit pathogenic strains
Streptococcal Pharyngitis
Pathogen
mode of entry
Dx
Symptoms/signs
P: Streprococus Pyogenes
E: through respiratory droplets- highly contagious
Dx: rapid strep test, cultures, and/or clinical examination
S: pharyngitis, fever, headache, swollen lymph nodes and tonsils, beefy red appearance to pharyngeal tissues
-some patient’s may develop scarlet fever exhibiting a rash caused by erythrogenic exotoxins
Streptococcus pyogenes complications (strep throat complications)
- suppurative- otis, media, sinusitis
- non-suppurative-rhuematic fever, scarlet fever, and glomerulonephritis
- scarlet fever arises in 10% of children with strep throat or strep skin condition
- pink-red skin rash, sore throat, fever, strawberry-like inflammed tongue
- rhuematic fever is a serious complicatoin resulting from lack fo treatment
- affects joints and heart
- causes permament heart damage called rhuematic heart disease
**antibiotics help reduce complications
Diptheria
pathogen
transmission
symptoms
treatment
life-threatening bacterial illness
P: caused by Corynebacterium Ciptheriae
T: respiratory droplets
S: sore throat, fever, pseudomembrane, exotoxin can lead to cardiac arrythmia and coma *biggest threat is the toxin
Tx: requires antibiotics and antitioxins
injection of diptheria toxoid is used for vaccination
Sinusitis
most common infection from microbiota of upper respiratory tract
- acute sinusitis: caused by variety of inidigenous microbes or URT
- pain, tenderness, and swelling over the affected sinuses - chornic sinusitis: 8-12 week. symptoms are more subtle and pain occurs less often
ear infections
- Otitis Externa- often caused by sreptococcus, staphylococcus, or psuedomonas
* swimmers ear - Acutre Otitis Media- short term infection of the middle ear. typically caused by S. pneumoniae and H. influenzae, moraxella catarrhalis
- chronic otitis media: long term infetion, inflammation and damage to the middle ear
Viral infections of the URT
most URI are caused by viruses-dont use abx to treat!
nose is the most commonly infected part of the URT
rhinoviruses and adenoviruses are often responsible for the common cold syndrome, coronaviruses also
transmitted via respiratory droplets
Rhinoviruses
produce inflammation in the upper respiratory tract
belong to the picornaviridae family
small, single stranded, naked, RNA viruses
transmitted by airbones repiratory droplets or contact with contaminated objects
acnt for 30-50% common colds
Adenovirus infections
belong to family adenoviridae
nondeveloped, isoahedral virions, double-stranded DNA
transmitted through respiratory droplets; fomites, fecal, oral
infection can cause:
- acute febrile phayngitis
- cough, lymph nodes in neck, whitish-gray material appears in throat
Diseased of the lower respiratory tract
- bordetella pertusis-whooping cough
- mycobacterium tuberculosis
- bronchitis
- bacterial pneumonia
- SARS-CoV-2
Pertusis (whooping cough)
Pathogen
Transmission
lower resp. disease
p: bordetella pertussis
- small, aerobic, gram-negative rod
t: respiratory droplet trnamission
exotoxin production paralyzes the ciliated cells and impairs mucus movement, potentially causing pneumonia
2 stages of pertusis
- initial (catarrhal) : general malaise, low grade fever, increasingly severe cough
- Second (parozysmal)- cells and mucus accumulate in the airways and cause labored breathing
* patients experience muluple paroxysms of coughs, followed by an inhalation of breath that sounds like a whoop
Tuberculosis
lower respiratory disease
-major cause of death world wide
P: mycobacterium tuberculosis enters respiratory tract in small aerosolized droplets
-90% of people who carrry latent tuberculosis will never develop and active infection
TB infection oin 3 stages
- Initial macrophage response (Primary TB)
- within 1st week of inhalation of bacillus
- bacillus reaches alveoli and is picked up my macrophages
- outcome depends on amount of TB bacilli and streangth of macrophage
- TB bacilli reproduce exponentially
- lasts until 3rd week after infection - Immune Control (latent TB)
- bacilli growth and destruction by macrophages are balanced
- 90% of patients infected stop at this stage and are not infectious
- no symptoms or signs of active disease
- in the lung the TB bacilli and macrophages build a round complex with bacilli and infected macrophages in the middle of healthy macrophages
- bacili are shielded from lung tissue and can survive for years - Lung cativation (active TB or secondary Active TB)
- primary complex doesn’t heal and TB becomes re-activated 12-24 months after initial infection
mycobacterium tuberculosis
-small, aerobic, acid-fast, nonmotile rod. cell wall froms waxy cell surface that is resistance to drying, chemical disinfectants and antibiotics
can’t be gram stained because 60% of their cell wall is lipid
acid fast stain
- mycobacteria appear red
- acid fast bacilli
4 drug cocktail used as first line of therapy, drug resistance is a concern
Tb disease detection
can be used for early detection of TB exposure
confimatory tests needed, can generate false positives due to previous TB test, recent TB immunizatoin
TB blood tests: interferon-gamma release measure how the immune system reacts to the bacteria that causes TB. a measure of exposure, not of active disease
- x ray and sputum test for active disease
- indicate if patient is contagious
Tuberculosis treatment
multidrug-resistance, mycobacterium tb is affecting which abx are used to treat TB
TB particularly a big problem for AIDS patients
leading cause of death in HIV-infected patients
attenuated M. Bovis is used in immunization
Drugs to treat TB
isoniazid, rifampicin, pyrazinamide, ethambutol
Acute bronchitis is inflammation of the bronchi
- viral or bacterial
- acute cough with or without sputum
- bronchitis producsed excessive mucous and a narrowing of the bronchi
- can be used by bacteria following a URT infection
- very few cases caused by bacteria, abx rarely indicated
- mycoplasma pneumoniae and chamydophila phemoniae can cause bacterial bronchitis in young adults
Pneumonis refers to diseae of bronchioles and alveoli
- lungs inflamed and filled with fluid
- caused by a variety of Alveoli
- bacterial pneumonia can be classifies as HAI or community acuired
- atypical phneumonia is caused by one of the CLaM organisms
- viral-influenza, SARS-CoV-2, rhinoviruses
Viruses can cause CAP
respiratory syncytial RS disease is caused by the respiratory syncytial virus
- commonly affects children under 1 year of age
- most common cause of fatal respiratory tract infections in infants under 12 months of age
- infects the bronchioles and alveoli of the lungs, causing cells to fuse together into synctia
*member of paramyxoviridae family of viruses
Paramyxoviridae family
parainfluenza and metapneumoviruses belong to this family
- parainfluenze infections usually caused by human parainfluenza viruses 1 & 3
- infectons milder than influenza
- symtpoms similar to cold, pneumonis and bronchitis may accompany disease
Human metapneumovirus (hMPV) are RSV-like viruses
- mild upper respiratory tract infection
- symptoms are milder than RSV disease
- rarely: ARDS and severe pneumonia
