Microbiology pathogenicity: bacteria Flashcards
why is microbiology important in medicine
microbial infections are associated with significant mortality and morbidity
infection is a global problem
antibiotic resistance is an increasing problem with some infections now untreatable with antibiotics
20% of prescriptions are for antibiotics
single-celled bacterial morphologies
each cell is separate, each has independent ability to survive and reproduce
large variety in cell shapes
2 most common are cocci and rod-shaped
cocci shape
round cells
rod-shaped cells
bacilli
monococcus
single cells
diplococcus
paired cells
staphylococcus
grouped cells
streptococcus
chained cells
name of a single rod-shaped bacteria
bacillus
they also form groups/clusters and chains
components of a bacterial cell
plasma membrane
cell wall
cytoplasm
nucleoid
plasmids
ribosomes
capsule
flagella
fimbriae
endospore
label the spore outside to inside
exosporium: adherence and biocide protection
coat: resistance
outermsmbrane: permeability barrier to biocides
cortex: resistance to biocides
germ cell wall
inner membrane: impermeability to biocides
core: resistance to heat, UV radiation, gamma radiation, hydrogen peroxide, formaldehyde and other biocides
which is the left picture and which is the right
left is gram-negative, double membrane so more difficult to transport
right is gram-positive
spaces are peroplasmic space
what is the spores coat resistant to
peroxynitrile
hydrogen peroxide
lysozyme
hydrochlorite
ozone
other biocides
mechanical resistance§
how do spores impact on infection control
important vehicles for transmission
have an impact on treatment
make control of spread more difficult
sequence of treatment of infectious disease diagnosis and control
observe patient, symptoms
sampling
laboratory observation and culture
identification tests
treatment e.g. antibiotic therapy
observation of population (epidemiology)
prevention of transmission
disease
disturbance in the state of heath wherein the body can’t carry out all normal functions
infectious disease
due to infection by pathogenic microorganisms
infections
invasion by and multiplication of a pathogenic microbe within or on a host
contamination
the presence of microbes in a location/environment
Koch’s postulates, proving a microbial cause
the specific causative agent must be observed in every case of the disease
agent must be isolated from a diseased host and grown in pure culture
when agent is inoculated into healthy but susceptible, hosts the agent must cause the same disease
agent must be re-isolated from the inoculated, diseased host and identified s identical to the original specific causative agent
infections in sinuses/nose
strep pneumoniae
h influenza
MRSA
rhinovirus
infections in outer ear
staphylococci
streplococci
pseudomonas
infections in inner ear
streptococci
haemophilius
infections in throat
candida
strep pyogenes
MRSA
viruses e.g. adenovirus
infections in lungs
strep pneumoniae
h influenza
staphylococcus aureus
gram-negative organisms
tuberculosis
infections in liver
viral hepatitis
infections in kidney/bladder
gram-negative organisms from gut
infections in cannula sites/moist skin
MRSA
streptococci
fungi e.g. yeasts or candida
infections in CNS
meningococcus
strep pneumoniae
h influenza
viruses: enterovirus and h simplex
infections in mouth
staphylococci
streptococci
anaerobic organisms: bacteroides
infections in heart valves
e.g. endocarditis
haemolytic streptococcus
staphylococcus
yeasts
infections in the blood
e.g. septicaemia
staphylococcus aureus
e coli
malaria
dengue
meningococcus
infections in the large and small intestine
gram negative: e coli, klebsiella,campylobacter,salmonella
C. difficile
bacteroides/anaerobes
infections in the joints
staphylococci
streptococci
n.gonorrhoea
haemophilius in children
infections in the bones
staphylococci
salmonella
streptococci
what is an infection
iceberg concept
severe symptoms
mild symptoms
infection but no symptoms
exposure but no symptoms
stages of disease progression
encounter
entry/establishment
spread
multiplication
damage
outcome
the disease process: stages 1 and 2
transmission and exposure
what does successful transmission and exposure depend on
more microbes the better
airborne: size.density,surface features
waterborne: density, surface features, hydrophobicity
contact: resistance to dessication, spore formation, adhesion tosurfaces
distribution on host: into cuts, digestive system, GI system, lungs
vectors
disease process stages 3 and 4
adherence and invasion
critical stages in disease success
adhesion depends on microbe and host features
invasion depends om break in surface layers or on active procedures from microbe
motility and chemotaxis
attachment often via pili or non-fimbrial adhesions
penetration of epithelial/ cells
capsules may allow survival inside phagocytes
virulent bacteria may inject epithelium cells with molecules to change surface features
stages 5 and 6 of the disease process
colonisation and tissue damage
consequences of disease
growth in tissues requires cells to resist host responses
may have to neutralise
growth also requires appropriate nutrients, some have limited or specific nutrients which slow or enhance microbial growth
tissue damage results from host cell death, accumulation of toxins and tissue degradation
normal flora
commensal flora
organisms living in benign symbiosis with the host
e.g. e.coli, lactic acid bacteria, staph aureus, candida yeast
some may be pathogenic but unable to enter disease process, lack attachment to suitable surface
host defence/disease resistance
surface defences
cellular defenses
inflammation
cytokines
complement system
immunity
pathgenicity
ability of a pathogen to produce an infectious disease in an organism
virulence
relative degree of damage done by a pathogen
or the degree of pathogenicity of a pathogen
virulence/pathogenicity factor
microbial product or strategy that contributes to virulence or pathogenicity
molecule determinants of pathogenicity
attachment to host tissues
production and delivery of various factor
replication and evasion of immunity
damage to host tissues
LD50
lethal dose of microbes toxin that will kill 50% of experimentally inoculated test animal
ID50
infectious dose required to cause disease in 50% of inoculated test animals
which proteins to bacteria employ
adhesins
attach to host tissues, usually located on the ends of fimbriae
can consist of glycocalyx
capsules
prevent phagocytosis
attachment
streptococcus pneumoniae
klebsiella pneumoniae
haemophilus influenzae
bacillus anthracis
streptococcus mutans
what is in the image
alpha hemolytic streptococci
secret hemolysins that cause the incomplete lysis of RBCs
what is in the image
beta hemolytic streptococci
secrete hemolysins that cause the complete lysis of RBCs
C. Coagulase
cause blood to coagulate
blood clots protect bacteria from phagocytosis from WBCs and other host defences
staphylococcus aureus are often coagulase positive
fibrinogen to fibrin (clot)
F. collagenase
breaks down collagen which is found in many connective tissues
clostridium perfringens- gas gangrene
uses this to spread through tissues
what is in the image
tissue damage caused by microbial enzymes of clostridium perfringens
toxins
poisonous substances produced by microorgansims
they’re a primary factor for pathogenicity
220 bacterial toxins that are known, 40% of which cause disease by damaging the eukaryotic cell membrane
toxemia
toxins in the blood stream
toxigenicity
capacity of micro-organisms to produce toxins
two types of toxins
exotoxins
endotoxins
exotoxins
produced inside mostly gram positive bacteria as part of their growth and metabolism
released into the surrounding medium
endotoxins
part of the outer portion of the cell wall of gram negative bacteria
liberated when the bacteria die and the cell wall breaks apart
