L46: Medically Important Gram -ve Bacilli Flashcards
1
Q
LPS structure
A
- Lipid A: endotoxaemia
- septic shock (20-40%), mortality rate (20-50%)
- activate cytokine cascade - O-antigen
- Core oligosaccharide
2
Q
3 important groups of gram -ve bacilli
A
- Enterobacteriaceae: Facultative anaerobes, oxidase -, glucose fermentation +
- Escherichia coli
- Salmonella
- Shigella
- Klebsiella
- Proteus, Providencia, Morganella
- Citrobacter, Enterobacter, Serratia - Vibrionaceae: Facultative anaerobes, oxidative +, glucose fermentation +
- Vibrio cholerae
- non-cholera vibrio (V. parahaemolyticus, V. vulnificus) - Pseudomonas aeruginosa: Strictly aerobic, oxidase +, glucose fermentation -
- Other non-fermenters (Acinetobacter baumannii, Stenotrophomonas maltophilia) - Others
- Bordetella pertussis
- Campylobacter
- Helicobacter pylori
- Haemophilus
- Brucella
- Legionella
- Spirochaetes
3
Q
Common clinical diseases of gram -ve bacteria
A
- UTI
- GI infection
- Intra-abdominal infection
- Hospital-acquired infection
4
Q
Characteristics of Enterobacteriaceae (big family) (ESSK: E. coli, Salmonella, Shigella, Klebsiella)
A
- large bowel (coliforms)
- O antigen (LPS)
- H antigen (flagella)
- K antigen (capsule)
5
Q
Escherichia coli
A
- Commonest gram -ve bacteria
- Intestinal: traveller’s diarrhoea, haemorrhagic colitis
- Extraintestinal: UTI, intra-abdominal
6
Q
Salmonella enterica
A
- > 2500 serotypes
- different O and H antigen
- Typhoidal (Typhi, Paratyphi) vs Nontyphoidal
- food and water
- Salmonellosis:
—> Gastroenteritis
—> Typhoid / Paratyphoid fever (systemic infection in human only)
—> Disseminated/focal infection (osteomyelitis, meningitis)
7
Q
Shigella
A
- e.g. Shigella dysenteriae
- causes bacillary dysentery
- contaminated food/water, faecal-oral route
- Shiga toxin
8
Q
Klebsiella pneumoniae
A
- pneumonia, UTI, abscess
- Mucoid colony
9
Q
Proteus, Providencia, Morganella
A
- Urease positive
- UTI, hospital-acquired infection
10
Q
Citrobacter, Enterobacter, Serratia
A
- hospital-acquired infections
11
Q
Vibrionaceae (big family), Aeromonas, Plesiomonas (under Enterobacteriaceae)
A
- curved
- oxidase +ve, glucose fermentation +ve
- fresh water
- GI infection, systemic infection
12
Q
Vibrio Cholerae
A
- Cholera, gastroenteritis
- profuse watery diarrhoea
- O antigen: O1, O139, non-O1-non-O139
- Cholera toxin: increase cAMP, inhibit NaCl reabsorption, increase water secretion
- Other non-cholera vibrio: V. parahaemolyticus (bacterial gastroenteritis) + V. Vulnificus (necrotising fasciitis)
13
Q
Pseudomonas aeruginosa
A
- Strictly aerobic
- Oxidase +ve, glucose fermentation -ve
- Saprophytes in soil, moist environment, skin
- Green pigment, fruity odour
- resistant to antibiotics and disinfectants
- IMPORTANT cause of Hospital-acquired infections
- Other non-fermenters: Acinetobacter baumannii, Stenotrophomonas maltophilia
14
Q
Bordetella pertussis
A
Whooping cough
15
Q
Campylobacter
A
- Microaerophilic
- Spiral
- Contamined animal products (nature in animals)
16
Q
Helicobacter pylori
A
Gastric ulcer, gastric cancer, gastric lymphoma
17
Q
Haemophilus influenzae
A
- Coccobacilli
- Facultative anaerobe
- Require blood: both X (haemin) and V factor (NAD/NADP)
- Only grow on chocolate agar (lysed blood cell) but not on blood agar (only X factor); may grow near S. Aureus on blood agar (satellite growth) since S. Aureus is haemolytic
- Pneumonia, meningitis
- polysaccharide capsule a-f, non-typeable
- Type b vaccine available (invasive disease in children/infants)
18
Q
Legionella pneumophila
A
- aerobic
- fresh water (cooling tower)
- Pontiac fever (flu-like illness)
- Legionnaire’s disease (pneumonia)
20
Q
Spirochaetes
A
- Spiral
- not readily visualised in light microscopy
- Treponema pallidum: ***not cultivable in-vitro, Syphilis, persist in body
- Leptospira interrogans: Corkscrew-shaped with end hooks, zoonosis, urine of animals, tropical and subtropical area
- Borrelia
21
Q
Brucella
A
- Coccobacilli
- non-motile
- non-sporting
- Brucellosis: zoonosis by ingestion
- Sheep, goat, cattle, pig
