The respiratory system - Microbiology Flashcards
How can bacteria be classified?
Morphology (cocci vs. rod/bacilli vs coccobacilli)
Gram stain (postive vs. negative vs. variable)
Growth requirements (aerobic vs. anaerobic)
Biochemical reactions (lactose fermenting vs. non-fermenting)
Serotypes (group A vs. B vs. D streptococcus)
Antibiotic resistance patterns (MSSA vs MRSA)
rRNA sequence analysis
How can bacteria be classified?
Morphology (cocci vs. rod/bacilli vs coccobacilli)
Gram stain (postive vs. negative vs. variable)
Growth requirements (aerobic vs. anaerobic)
Biochemical reactions (lactose fermenting vs. non-fermenting)
Serotypes (group A vs. B vs. D streptococcus)
Antibiotic resistance patterns (MSSA vs MRSA)
rRNA sequence analysis
Describe the process of gram staining
- Application of crystal violet
- Application of iodine
- Alcohol wash
- Application of safranin
a) Describe the role of the coagulase test
b) Give 2 examples of coagulase positive and negative bacteria
a) Coagulase is an enzyme produced by some bacteria that converts fibrinogen to fibrin
The presence of coagulase is used predominately to differentiate staphylococcus spp
b) Coagulase positive - S.aureus, some S.intermedius
Coagulase negative - Most other staphylococcus.spp (e.g., S.epidermidis, S.capitis, S.lugdunensis, S.saprophyticus)
a) Describe the role of the hemolysis test
b) What are the different groups of this test and provide 2 examples for each
a) The hemolysis test further classifies streptococcal species based on their ability to haemolyze red blood cells
b)
- Alpha haemolytic (partial hemolysis) - S.pneumoniae, Viridans strep.
- Beta haemolytic (complete hemolysis) - S.pyogens, S.agalactiae
- Gamma haemolytic (no hemolysis) - S.bovis, enterococcus
a) Describe the role of the lancefield stereotyping
b) What are the different groups and provide 2 examples
a) Group A- S.pyogens
Group B - S.agalactiae
Group D - Enterococcus, S.bovis
b) No lance field antigens - S.pneumoniae, viridan’s strep
a) Describe the role of lactose fermenting in classifying bacteria
b) What are the different classifications and provide at least 2 examples for each
a) The ability to ferment lactose is a differentiating characteristic of gram-negative rods
b)
Lactose ferments (i.e., “lactose positive”) e.g., E.coli, Klebsiella, Enterobacter
Lactose non-fermenters (i.e., “lactose negative”) e.g., psuedomonas, Proteus, H. Flu, Salmonella, Shigella, Stenotrophomonas, Acinetobacter
Lactose slow fermenters e.g., Citrobacter, Serratia
Atypical bacteria is an inexact term applied to bacteria which are particularly unusual in cellular structure, morphology, biochemistry, or life cycle.
Describe 4 examples of this
Mycoplasma (lack a cell wall, highly pleomorphic)
Chlamydia (lack peptidoglycan in the cell wall, multiphase life-cycle, obliterate intracellular parasites)
Rickettsia (obligate intracellular parasites, generally require arthropod vectors)
Legionella (does not grow on traditional media)
Streptoccocus pneumoniae
a) Type of bacteria
b) How can we prevent this infection?
b) Treatment
a) gram positive anaerobe
b) Pneumococcal vaccine for high-risk groups
c) Penicillin, macrolides e.g., erythromycin
Name 5 complications of group A strep (GAS) infections caused by streptococcus pyogenes
Local and very uncomfortable - quinsy, otitis media/sinusitis, mastoiditis
‘Systemic’; feeling systemically unwell and accompanying rash - Scarlet fever
‘Immune mediated’; life threatening - rheumatic fever, glomerulonephritis, rheumatic heart disease (myocarditis, pericarditis, lifelong valvular damage)
Corynebacterium diphtheria
a) Classification of bacteria
b) complications
c) Treatment
d) Prevention
a) Aerobic, gram-positive bacillus
b) Respiratory obstruction, toxic myocbrdopathy, toxic neuropathy, toxic neuropathy
c) Antitoxin, antibiotics (erythromycin)
d)
- Immunisation
- DTaP/IPV/Hib at 2, 3 & months
- Directed against the toxin
- Close contacts - 7 days eyrthromycin
Haemophilus influenzae
a) Classification
b) What types of illnesses can it cause?
c) Clinical features
d) Is there a prevention for this infection?
e) Treatment
a) Gram-negative coccobacilli
b) Ear infections, sinus infections, epiglottis, LRTI
c) Symptoms of URTI and can mimic viral infections e.g., fever (usually low grade)
d) Not really, The Hib vaccine only protects against group B; its other serotypes that are common in ear/sinus infection
e) Amoxycillin, co-amoxyclav, doxycycline
a) What is Pertussis (whooping cough) caused by?
b) Describe classification of this bacteria
a) Bordetella pertussis
b) Aerobic gram-negative coccobacilli
a) What does fusobacterium inhabit?
b) What are clues of infection by fusobacterium
a) It inhabits the mucous membrane of humans and animals
b) Foul-smelling discharge, proximity of infection to mucosal surfaces, abscess formation, necrosis and gas in tissues
Give 3 examples of culture techniques that diagnose respiratory infections
-Sputum
-Swabs
Microscopy - Gram stain and Immunofluorescence
Bacterial culture - Choice of media: support growth of expected pathogens, suppress growth of commensals
Antigen detection - EIA/ELISA
Antibody detection
