respiratory tract infections Flashcards
what common viruses cause self-limiting URIs (“the cold”)
rhinovirus; adenovirus; coronaviruses; influenzaviruses; parainfluenzavirus
what proteins change between influenza subtypes (2)
hemagglutin; neuraminidase
what receptors do heamaglutinin bind to on host respiratory epithelial cells
sialic acid receptors
what kinds of virus more readily mutates
RNA viruses
what is “drift and shift”
antigenic drift - small changes (or mutations) in the genes of influenza viruses that can lead to changes in the surface proteins of the virus, the small changes in HA and NA that accumulate over time may result in viruses that are antigenically different, meaning a person’s antibodies bind differently or not at all to the virus, resulting in a loss or reduction in protection against that particular flu virus,an important reason why people can get flu multiple times over the course of their lives;
antigenic shift - an abrupt, major change in a virus, resulting in new HA and/or new HA and NA proteins in flu viruses that infect humans, Shift can happen if a flu virus from an animal population gains the ability to infect humans;
Type A viruses undergo both antigenic drift and shift and are the only flu viruses known to cause pandemics, while flu type B viruses change only by the more gradual process of antigenic drift
what is the S1 spike glycoprotein responsible for
virus-host range and cellular response
what is the S2 spike glycoprotein responsible for
virus-cell membrane fusion
what gram staining are bacilli normally
gram negative
what gram staining are bacilli normally
gram negative
what gram staining are cocci normally
gram positive
6 ways to classify bacteria
morophology; gram staining; growth requirement (aerobic/anerobic); biochem reactions; serotype (A vs B vs D); antibiotic resistance pattern (MSSA, MRSA); rRNA sequence analysis
4 additional important tests for bacteria classification
coagulase test; haemolysis; lancefield serotype ( based on carbohydrates present on bacterial wall); lactose fermentation
what are the 2 main pathogenic enterococci
E.faccalis; E.falcium
examples of atypical resp bacterial pathogens (5)
mycoplasma pneumoniae; mycobacterium tuberulosis; chlamydia pneumoniae; legionella pneumophila
why is mycoplasma atypical
no cell wall - so cant give B-lactams; highly pleomorphic
why is legionella pneumophilia atypical
does not grow on traditional media; obligate intracellular parasites
where can legionella pneumophilia be acquired from?
man-made stagnant water supplies - pipes, hot tubs, cooling towers etc.
what 2 disease can arise from legionella pneumonia and what are their features
- Pontiac fever - acute, self limiting, fever, chills, headache, sore muscles;
- legionnaire’s disease - presentation ranges from a mild cough to severe/fatal pneumonia, death can occur due to multi-organ failure, cough, anorexia, headache, lethargy, blood streaked phlegm
legionella penuophilia morphology
grame -ve flagellated bacillus
what information does that lab need when diagnosing an RTI (6)
identification; clinical details (symptoms, immunosuppression, duration etc.); antibiotic history; exposure; report destination
when can g-interferon release be used for TB diagnosis
testing for latent infection - based on T cell response to TB antigens
streptococcus penumoniae features
gram +ve diplococci/short chains; has a capsulre that helps it evade phagocytosis; can adhere to respiratory epithelium; usually only occurs in susceptible pts; childhood vaccination is effective
what can Strep A (a cause of bacterial throat infections) cause (other organ systems)
rheumatic heart disease; reactive arthritis; toxic shock syndrome; scarlet fever/strawberry tongue; used to be responsible for childbirth deaths
what differentates the different sereotypes of strep (biochem)
the N protein found in the outercapsules
strep A features (morphology)
gram +ve; has pyrogenic exotoxins that cause rash, fever etc.
diphteria (corynebacterium diptheria) morphology
gram +ve bacillus
diptheria symptoms
swollen glands; weakness; sore throat; fever; SOB; dysphagia; grey-mucous
diptheria MOA (6)
- spread by droplets and infected sores/ulcers;
- toxin produced when the bacillus itself is infected (e.g by a virus)
- destroys the epithelial lining of the RT forming a grey coating (pseudomembrane)
- pseudomembrane builds up in the airways which can make breathing difficult (fatal)
- toxins produces can enter blood stream/brain
- give erythromycin to close contact immediately
what can cause pharyngitis and what are the symptoms
Most cases caused by viruses but can be caused by group A Beta-haemolytic strep., Mycoplasma pneumoniae, or Chlamydophilia Pneumoniae; sore throat and there is erythema of the pharynx, often with the enlargement of the tonsils; self limiting
what can cause sinitis and what are the symptoms
H.influenzae, Strep. Pneumoniae, Staph. aureus and anaerobic bacteria; Infection of the maxillary sinuses causes facial pain, nasal obstruction and discharge, often accompanied by fever and malaise
haemophilus influenzae features
opportunistic pathogen - only causes trouble when other factors give it the opportunity (immunosuppression etc.) - otherwise usually resides in the RT of healthy people;
what serious symptom can H.influenzae B cause?
epiglottitis - blocks airways
what causes whooping cough
bordetella pertussis
whooping cough symptoms
intense bouts of coughing that makes it hard to breath - whooping sound when taking in breaths; sore throat; rhinorrea; temperaure
bordetella pertussis morophology
aerobic, gram -ve bacillus
where does fusobacterium inhabit
mucous of humans/animals
what can fusobacterium cause
Lemierres syndrome
signs of a fusobacterium infection
foul smelling discharge, abscess formation, gas in tissue
fusobacterium morphology
anerobe; gram -ve, spindle shaped bacilli; often in pairs
what lab techniques can be used to check samples for bacteria
microscopy; bacterial culture; antigen detection (ELISA); antibody detection
what is key in determing how useful a sample will be in testing for cultures
the quality - pus, epithelia cells, too much saliva etc.
how does vertical transmission of resistance occur
bacteria may carry resitance genes in their plasmids/transposers -> selection pressure leads to an evolutionary advantage for resisitant bacteria ->pass resistance onto offspring -> whole colony now populated by resistant bacteria
how does horizontal transmission of resistance occur (3)
transfer of resistant genes in any of the following ways;
1. conjugation - bacterial cells adhere to each other and plasmids/transposers can be transferred from donor to recipient via sex pilli;
2. transformation - when bacteria die the cells lyse and genetic material is released into the environment -> other bacterias may be able to take this up and incorporate it into their own genome (this is hoe B-lactams often become resistant to);
3. transduction - bacteria infected with a phage -> phae incorporates bacteria DNA and then multiplies ->. bacteria lyse and phage can pass on bacterial DNA to other bacteria it infects
what are the 3 β-Lactam classes and give examples
- penecillins - benzylpenicillin, amoxicillin, piperacillin
- cephalosporins - cefotaxime, ceftriaxone, ceftazidime
- carbapenems - meropenem, entapenem
examples of macrolides/lincosamides
erythomyocin; clarithromycin; clindamycin
macrolide MOA
bind the bacterial 50S ribosomal subunit causing the cessation of bacterial protein synthesis
β-Lactam MOA
interrupt bacterial cell-wall formation as a result of covalent binding to essential penicillin-binding proteins (PBPs), enzymes that are involved in the terminal steps of peptidoglycan cross-linking in both Gram-negative and Gram-positive bacteria.
what are the 3 categories of breakpoint testing
susceptible; intermediate; resistant
what is antibiotic susceptibilty testing and why is it done
specifies effective antibiotic dosage and formulates a profile of empirical therapy - i.e. finds the lowest conc for inhibition; needed to prevent resisitance
pH and humidity change along the resp tract
pH gradually increases along the resp tract; humidity increase generally occurs in the nasal cavity
role of microbiota in RT
protective - evidence that it helps stop invading pathogens (S.epidermis shown to destroy biofilms of S.aureus); may have an effect on the morphogenesis
examples of bacteria found in the nasal cavity
staphylococcus spp.; moraxella spp.; streptococcus spp.
examples of bacteria found in the oropharynx
streptococcus spp.; veillonella spp. etc.
examples of bacteria found in the lungs
prevotella spp.; streptococcus spp.; veillonella spp
what causes leishmaniasis and how is it spread
sand flies; Leishmania parasites are transmitted through the bites of infected female phlebotomine sandflies, which feed on blood to produce eggs
what causes Schistosomiasis and how is it spread
parasitic worms - considered a neglected tropical disease; live in certain types of freshwater snails, The infectious form of the parasite, known as cercariae, emerge from the snail into
the water -You can become infected when your skin comes in contact with
contaminated freshwater
treatment for schistomiasis
Praziquantel is taken for 1-2 days to treat infections caused by all
schistosome species
