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Bacteria

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by

Lam Ip

on 7 April 2016

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Transcript of Bacteria

Bacteria
Gram positive
Gram negative
Aerobic
Aerobic
Anaerobic
Anaerobic
Cocci
Bacillus
Staphylococci
Streptococci
Coagulase positive
Coagulase negative
Staphylococcus aureus
Pus-forming infections
Blood-strem infections
Toxin illnesses
Protein A: prevents phagocytosis
Coagulase: coat bacteria, prevent phagocytosis
Hyalurorindase: hydrolyses host tissue
Haemolysis, Exotoxins
Staphylococcus epidemidis
Only pathogenic with foeign body e.g. prosthetic joint
Alpha-haemolytic
Beta-haemolytic
Lancefield grouping: carbohydrate antigen in bacterial cell wall
Group A strep
(Streptococcus pyogenes)
Tonsillitis
Cellulitis
Severe soft tissue infections
Puerperal sepsis
Similar to A
but more aggressive
Group C and G:
Cell wall: factor to promote adherence
M protein: antiphagocytic cell wall protein
Toxin - haemolysis
Lots more toxin
Group B strep (Streptococcus agalatiae)
Normal rectal and vaginal flora
Neonatal meningitis, bacteraemia, pneumonia
Occasionally pathogenic in adults
Streptococcus pneumoniae
Community acquired pneumonia
Meningitis
Broncitis in COPD
Others (viridans streps)
Mucosal flora
Stick to heart valves, cause endocarditis
Enterococci
Found in gut
More resistant to antibiotics
involved in intra-abdominal sepsis
Bacillus
Corynebacterium
Listeria
Bacillus anthracis
Disease of herbivores
Reservoir = soil
Human infacted by cutaneous innoculation or inhalation
Bacillus cereus
Food poisoning
pathogen if injected into sterile sites
Listeria monocytogenes
intrauterine/neonatal septicaemia/meningitis
Can multiply at 4C
Risk in pregnancy
Corynebacterium diptheria
agent of Dephtheria
Transmission: person-to-person by respiratory droplet
Bacteria in pseudomembrane in throat: potential suffocation
Diphtheria toxin produced in throat, via bloodstream then inhibits protein synthesis in heart and peripheral nerve
sensitive to metronidazole
Cocci
Bacillus
Clostridium
Clostridium tetani
Transmission: spores ubiquitous in soil, then wounds
Toxin-mediated disease: neuro toxin causes excitation of motor neurones by blocking release of GABA
Symptons: spasms/rigidity of voluntary muscle and autonomic system
Prevention: vaccine against toxins
Clostridium botulinum
Food-borne: spores germinate in food
Toxin-mediated disease: neuro-toxin prevents release of ACh
Symptoms: symetrical flaccid paralysis
use as BOTOX
prevention: standards of food preparation
Clostridium difficile
Major cause of healthcare-associated infection
Transmission: ingestion of spores (survives in alcohol)
Prevention: decrease host susceptibility (antibiotics)
Clostridium perfringens
Gas gangrene and other soft tissue infections
Transmission: spores ubiquitous in soil and gut
Toxin-mediated disease: main toxin in α-toxin, a lecithinase, damages cell membranes (haemolysis)
Cocci
Bacillus
Neisseria gonorrhoeae
Neisseria meningitidis
rash
Neisseria cattharalis
COPD exaccerbations
Resistance to some antibiotics
Lipopolysaccharide - endotoxin
Sometimes exotoxin
common ones are major hospital pathogens
Non-fastidious
grows on simple lab media (blood)
Fastidious
Fussy, usually slow
need enriched agar plate e.g. chocolate
Enterobacteriaceae
coliforms ferment sugars
Non-fermentors
oxidase-positive
Curved bacilli
Vibrios, Campylobacter
Pseudomonas
Primary Pathogens
Opportunistics Pathogens
Yersinia
Escherichia coli
Proteus
Normal human gut flora
Many different strains: some cause diarrhoea
Most strains cause UTI
Common cause of blood-stream infection (bacteraemia)
Klebsiella pneumoniae
Second commonest coliform causing UTI and bacteraemia
often antibiotic-resistant, spread easily between patients
Salmonella & Shigella
Important cause of gastroenteritis
Shigella - human reservoir only
Salmonella - multiple species hosts
- spectrum of invasiveness
Pseudomonas aeruginosa
Reservoir: environment especially water
Human respiratory pathogen
Becteremia in immuncomproised
Burkholderia cepacia
Reservoir: soil, plants
Pathogen in CF
Vibrio cholerae
Cholera
Reservoir: (warm) salt water
Toxin-mediated disease. Increased cAMP within cells: decreased Na uptake and increased Cl secretion, leads to water loss
Death from dehydration and electrolyte imbalacne
Treat with oral re-hydration
Campylobacter
Commonest bacterial cause of bacterial gastroenteritis
natural host - birds
Haemophilus influenzae
Unencapsulated strains are common: respiratory tract - COPD, pneumonia
Capsulated serotype b (Hib) causes meningitis in young chilren
Legionella
Cause of severe pneumonia
lives in natural and engineered water systems, inside amoebae
Legionella
Cause of severe pneumonia
lives in natural and engineered water systems, inside amoebae
Helicobacter
Produces urease, breaks down urea to ammonia. Buffer stomach acid
Causes inflammation leading to ulceration
In human gut, mouth
involved in poly-microbial infections
Bacteroides
sensitive to penicillin, vancomycin
form spores
resistance to penicillin, vancomycin
Full transcript