Major gram - bacteria Flashcards
types of bacteria and characterisiscs
Types bacteria
1) gram +
- purple
2) gram –
- stain pink
- 2 membranes
- LPS outside
flagellum
- called H antigen
- surface antigens used to class different bacteria
- allows bacteria to swim
K antigen
capsule
LPS O antigen use
outer membrane
LPS
- Deter complement proteins (therefore preventing complement cascade and antigens)
- Capsule repels complement proteins or antibodies
gram - cell envolope made of
LPS interacts with the immune system (can be called endotoxin)
Gram - quick summary
- Gram – bacteria have 2 membranes with the OM(outermembrane) connected to LPS layer
- thin peptidoglycan layer (between the membranes)
- do not retain gram stain
- Outer layers and released are LPS major antigens (K H O)
- LPS and Capsule help immune evasion
what type of bacteria is neisseria spp
Gram – diplococci
Common commensals
Pathogenic neissieria speciess
n meningitis
n gonorrhoeae
n meningitis
- meningitis/meningococcal septicaemia
- infection of CSF and meninges
- commensal carriage in pharynx/nasopharyx
what are oligosaccharides good for and found on
invading immune system
gonorrhoea
what can neisseria meningitis/gonorrhoea be grown on
Both fastidious growth (heated blood) + CO2
Nutritionally fussy, have to be grown on blood (dark), due to the iron leaked out as the blood cells have been heated and burst, incubated at 37 degrees
meningitis symptoms
- Rapid onset fever
- dislike to light
- rash (does not blanch when pressed unlike normally)
- stiff neck
- not feeling well
what is meningitis
Inflammation around brain and spinal column (meninges)
how many serogroups does meningitis have and what do these depend on
polysaccharide capsular antigen A B C Y W 135
how does meningitis spread
- Either directly to subarachnoid space
- or through nasopharyngeal mucosa to enter bloodstream
what does mengigitus have
IgA protease for serum resistance
diagnosis of meningitis
1) Cerebro spinal fluid
- mainly PMNLs, presence of bacteria - diplococci
2) blood/CSF/throat swab cultures and for DNA extraction
- sub culture on chocolate agar
how to serogroup meningitis
- Elisa for capsule types and surface OM antigens
- PCR for species and strain specific genes
- Whole genome sequencing – routine for strain epidemiology
treatment of meningitus
Antibiotics (often accompanied by steroids)
Cefotaxime and penicillin
Often with corticosteroids (to reduce inflammation )
Vaccines available for group A C Y and W135
neisseria summary
- gram – diplococci
- cause of gonorrhoea and meningitis
- variable surface capsule – major virulence factor
what causes haemophilus influenzae and how does the bacteria invade
gram - cocco bacillis
(causes septicaemia, pneumonia, meninigits)
- penetration of submucosa of nasopharynx
H influenza pathogenesis
6 capsule types a-f (some non capsulate commensals)
capsule is major virulence factor
IgA protease
how does capsule work for H influenza
avoidance of c3b binding
- most disease caused by type b capsule
diagnosis of h influenza
Sputum, throat swabs, blood culture
Chocolate agar 5-10% CO2
- check for development of gram - cultures
Meningitus
- antigen detection/ PCR
what do haemophili require for growth
X and V
H influenzae requires both X and V
H ducreyi requires only X
pseudomonas arguginosa
human commensal
grame -
motile rod
strictly aerobic
what does pseudomonas arguginosa look like on agar plate
Colonies on agar with characteristic green spreading shape and grape smell
what is a cause of infection after burns and what can it lead to
pseudomonas arguginosa
- septicaemia (ecythma gangrenous lesions)
kelbsiella
opportunistic pathogen
antibiotic resistant
mucoid colonies, capsule allows immune evasion
what is used to treat klebsiella
carbapenems and cephalosporins
