micro lecture 14 Flashcards
is Campylobacter G+ or G-
IT IS G-
list facts about Campylobacter
Curved, spiral or S-shaped rods
Single flagellum (motile)
Microaerophilic
Don’t ferment carbohydrates
Infect intestine (jejunun, ileum, colon)
Bacteraemia possible though rare (extremes of age, co-morbidity)
Widely distributed in nature
Fowl (major reservoir) and Mammals
Faecal / oral route transmission
Cause intestinal disease – rarely extra-intestinal
99% of infections are C. jejuni species
Linked to subsequent Guillain-Barre syndrome
describe the common infection caused by Campylobacter jejuni?
Acute enteritis:
1-7 days incubation
Self-limiting (but several weeks)
Systemic symptoms: Fever, headache, myalgia
Intestinal symptoms: cramps, diarrhoea
what are the prevention and treatments for Campylobacter jejuni?
Thorough cooking (esp BBQ chicken), milk pasteurisation, disinfect surfaces
Fluid and electrolyte balance often sufficient
Antibiotics if needed (start early & if severe):
erythromycin / clarithromycin (resistance?)
ciprofloxacin
3rd generation cephalosporin if very severe
describe the implications Shigella?
Shigellosis (bacterial bacillary dysentery)
Most common in young children
Non-motile, unencapsulated,
does not ferment lactose (Lac-)
Person-to-person, contaminated stools
Also: flies, food, water
Low infectious dose (10 - 200 organisms)
Invade and destroy mucosa of large intestine
Shigatoxin – enterotoxic, cytotoxic
list major groups of Shigella?
Group A: S. dysenteriae (most severe)
Group D: S. sonnei
Shigella causes Bacillary dysentery
what are the features of Bacillary dysentery?
Diarrhoea with blood, mucous and painful abdominal cramps
Severe in children and elderly
Malnourished: dehydration and death
Resolves in 1 week (if survived)
what is the treatment for Shigella
Antibiotics reduce duration and shedding
Widespread resistance
ciprofloxacin, ceftriaxone or azithromycin
Vaccine in development (NB many serotypes)
describe Vibrio species
Short, curved rod-shaped
Single polar flagellum
Facultative anaerobes
Require NaCl – waterborne organisms, so seawater / estuaries
describe Vibrio cholerae
Transmitted via food and water
No known animal reservoirs or vectors
Carriage in humans uncommon
Associated with raw seafood
Outbreaks – poor sanitation of water supplies
what are the implication of Vibrio cholerae
Severe disease occurs in about 5% of cases:
If untreated: 50% death within hrs
Treatment: <1% death
Aggressive replacement of fluid & electrolytes
Antibiotics decrease duration and shedding
Tetracyclines, macrolides, quinolones
Public health measures to reduce faecal water contamination.
WHO vaccine programme
what are the three species of Yersinia
Y. enterocolitica (enterocolitis)
Y. pseudotuberculosis (enterocolitis, despite name)
(Y. pestis – bubonic plague)
describe the implication of Yersinia enterocolitica
and what is used in treatment
Contaminated food (abattoirs, raw meat)
Lesions in ileum, enlargement of lymph nodes
Enterocolitis: fever, abdominal pain, diarrhoea, right lower quadrant tenderness
(pseudoappendicitis)
Resolves in 2-3 weeks
May → Polyarthritis, pharyngitis, septicaemia
treatment
ciprofloxacin,
trimethoprim-sulphamethoxazole
what are the features of Helicobacter pylori
Curved or spiral organisms,
closely related to Campylobacter
Multiple polar flagellae (corkscrew motility) Produces urease (urea to ammonia, protects against acid)
what are the implications of Helicobacter pylori
World-wide distribution, very common
Person-to-person transmission
“Never” isolated from food or water
Untreated: chronic life-long condition
Colonises stomach, duodenum, oesophagus
Survives in mucus layer coating epithelium
how does Helicobacter pylori colonizes the colon and causes ulcer
Urease -> ammonia ions -> neutralises acid -> allows colonisation/multiplication
Ammonia ions
cytotoxin = low-grade destruction of mucous producing cells, exposing connective tissues to acid
what are Helicobacter pylori tendencies ?
Initial infection
1 week
Gastritis, diarrhoea
Chronic
Superficial gastritis, ulcers
Risk of carcinoma, B-cell lymphoma
what is the treatment for Helicobacter pylori?
Elimination requires combination therapy
Readily develops resistance,
always multiple agents
Proton pump inhibitor, amoxicillin, clarithromycin, metronidazole, …
what are the resistance mechanisms of Gram-negative organisms?
β-lactamases. Multiple variants, including activity against extended-spectrum agents (3rd , 4th gen cephalosporins, carbapenems). Efficacy much increased by outer membrane “holding” the enzyme near to the drug’s site of action in the periplasmic space
(also enzymes to deactivate aminoglycosides)
Porins. Selection of porin-poor strains can limit penetration of otherwise effective drugs
Efflux pumps. Active removal from within the cell. Better to pump it right out, rather than periplasmic space
Binding site mutation (common for quinolones)
