Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Microbiology Revision:
Taxonomy:
In a broad sense, the science of classification, but more strictly the classification of living and
extinct organisms
...

Nomenclature – systematic naming of organisms based on international rules
according to its characteristics
...
This disease is caused by Prions
...

Clostridium botulinium:
• Club rod shaped bacteria
• Causes improper muscle contraction as the bacteria bind to the muscle-nerve sites
...
tetanus causes a potent biological toxin, tetanospasmin, and is the causive agent
of tetanus, a disease that causes painful muscular spasms which lead to respiratory
failure
...

Taxonomy hierarchical structure:
1
...
Genus
3
...
Order
5
...
Kingdom
7
...
Spores are very resistant to heat
...


MRSA:
Methicillin-resistant staphylococcus aureus is known as a hospital superbug, as its resistant
to methicillin related antibiotics
...

MRSA is treated with Vancomycin antibiotics, treatment can take up to 3 months
...

Streptococcus pyogenes also causes flesh eating bacteria (Necrotising fasciitis)
...
pyogenes with cell surface
antigens similar to human surfaces)
• Acute glomenlonephritis (immune complex disease) formation of streptococcal
antigen-antibody in the blood stream which lodge in the glomenuli of the kidney
...

Mycobacteria:
• Rod shaped bacteria
• Acid fast – due to presence of mycolic acids
• Hard to gram stain due to waxy cell membrane
• May have branching or kilamentas growth
• 2 main groups (fast and slow growers)
o Mycobacterium tuberculosis is a slow grower
o Mycobacterium smegmatis is a fast grower
...

Mycobacterium leprae (Leprosy)
• can cause folded, bulblike lesions, especially on the face
• poor prognoses for multibacillary form
*IMPORTANT*
• Gram-positive organisms can cause a wide range of infections of varying
severity
• Infections include:
o Tuberculosis
o MRSA
o Leprosy
o Pneumonia
o Scarlet fever
Morphology:
This is the study of form
in bacteria
This includes:
• Shape
• Size
• Cell structure
• Motility
• Spore formation
• Capsule formation
• Toxin production
...

• The O (O157) in the name refers to the cell wall antigen number, and the H (H7)
refers to the flagella antigen
...

Legionella:
• Legionella is a pathogenic Gram-negative bacterium, including species that cause
legoinellosis (legionaries disease)
• Legoinellosis is a potentially fatal infectious disease caused by gram-negative ,
aerobic bacteria
...

Microbial growth:
This refers to the multiplication of cells, not the size
...
5-7
...
Attachment to a susceptible host cell
2
...
Synthesis of nucleic acid and protein
4
...
Release of mature virons from cell
...

HIV occurs with the transfer of blood, semen, vaginal fluid, pre-ejaculate or breast milk
...

Typically, parainfluenza virus is transmitted by an aerosol created by coughs and sneezes in
the air
...

SARS (severe acute respiratory syndrome):
• Respiratory disease in humans
• Caused by viral replication
• SARS has to be treated by antipyretics, supplemented by oxygen and ventilator
support
...

Swine flu:
The swine flu influenza virus
...

There was a large outbreak in 2008/09 from pigs in Mexico
...

Anti-biotic drugs:
• Penicillin is the most common form of antibiotic drug
...
Penicillin is a bactericidal
...

o A bacteriostatic stops bacteria from multiplying
...
Micro-organisms penetrate the matrix
...


Factors affecting microbial killing:
• Population size – a large population takes longer to kill than a smaller one
• Population composition – microbes can vary in susceptibility
• Concentration of anti-bacterial agent – the more concentrated, the more effective
• Duration of exposure – the longer the population is exposed to an agent, the more
effective
• Temperature – most chemicals kill more effectively at a raised temperature
• Environment – presence of organic matter can protect the effects of agents
Physical methods:
• Heat – dry/moist heat
• Autoclave – moist heat sterilisation 100oC+
• Dry heat – kills by oxidation
• Pasteurisation – doesn’t sterilise but kills most pathogens
• Filtration – depth filters (thick layers of granular or fibrous materials) or mem
...
Affects the kidneys reservoir in animals, herbivores are
more likely to be infected
...


Entry of pathogen into the host:
•
•

Pathogen invasion
o Starts at the site of adherence
o May spread throughout the host via the circulatory system
Colonisation and growth
o The availability of nutrients is most important in affecting pathogen growth
o Pathogens may grow locally at the site of invasion or may spread through the
body

Virulence:
Measuring virulence – virulence can be estimated from experimental studies of the
LD50 (lethal dose50)
The dose of an agent that kills 50% of the animals in a test group
•
•
•

Attenuation – the decrease or loss of virulence
Toxicity – ability of an organism to cause disease by means of a performed toxin that
inhibits host cell function or kills host cells
Invasiveness – ability of a pathogen to grow in host tissues at densities that inhibit
host function

Virulence factors:
• Pathogens produce enzymes that
o Enhance virulence by breaking down or altering host tissue to provide access
to nutrients
▪ E
...
hyaluronidase
o Protect the pathogen by interfering with normal host defence mechanisms
▪ E
...
coagulase
Exotoxins:
• Proteins released from the pathogen cell as it grows
• Three categories:

o

o

o

Cytolytic toxins
▪ Work by degrading cytoplasmic membrane integrity, causing cell lysis
and death
▪ These toxins are haemolysins
AB toxins
▪ Consist of 2 subunits, A and B
▪ Work by binding to host cell receptor (B subunit) and transfer ring
damaging agent (A subunit) across the cell membrane
▪ E
...
diphtheria toxin, tetanus toxin, botulinium toxin
Superantigen toxins
▪ Work by stimulating large numbers of immune cells
▪ Result in extensive inflammation and tissue damage

Enterotoxins:
• Exotoxins whose activity affects the small intestine
• Generally cause massive secretion of fluid into the intestinal lumen, resulting in
vomiting and diarrhoea
o E
...
cholera toxin
Enderotoxin:
• The lipopolysaccharide portion of the cell envelope of certain gram-negative bacteria,
which is a toxin when solubilised
...

• Age is an important factor for determining susceptibility to infectious diseases
o very young and very old individuals are most susceptible
• stress can predispose a healthy individual to disease
• diet plays a role in host susceptibility to infection
• certain genetic conditions can compromise a host
Hosts have innate resistance to most pathogens
• natural host resistance
• tissue specificity
• physical and chemical barriers
Malaria:
•
•
•
•
•
•

it’s a parasite
it’s a protozoa
Plasmodium falciparium is the most clinically serious one (resistant against almost all
anti-malariobials)
Plasmodium Vivax ovale malariae is another type
...
Egg is laid on water
2
...
The larve come to the surface to breath
4
...
Pupee come to the surface to breath
6
...

7
...
Seek a new mate and females can live up to a month
...
Males and females feed on sugar and nectar, and females feed off blood
How you get malaria:
1
...
7-9 days to pass

3
...
Once infected, symptoms appear 8-30 days later
Spread and multiplication of malaria:
• Complex life cycle
• Plasmodia inhibit salivary glands of infected mosquitos as sporeozoites
• Injected into human blood stream when mosquitos bite and feed
• Sporeozoites enter liver cells within 30 minutes
• They multiply and mature in the next 14 days (hepato cellular cycle) to very large
numbers
• Release into blood as meroizoites (that can invade red blood cells)

Malaria life cycle:
1
...
After 2-3 days red blood cells burst
3
...
Theres merazoites infect previously unparaditised red blood cells (the erythrocytic
cycle)
5
...
Some of the plasmodia in the blood may develop into forms capable of sexual
reproduction called gametocytes
7
...
In mosquitos gut, male and female gametocytes participate in the sexual portion of
the reproductive cycles
9
...
Migrating to the salivary glands and become infective sporeozoites

Diagnosis:
1
...
Clinical diagnosis (acute P
...
Antigen detection test (minimal training, but costs high per test)
4
...
Serology (indicates past infection, expensive)

Prevention and treatment:
• Natural immunity – imperfect, but immune response may play a significant role
• Chloroquinine – used vs
...
falciparum from resistant areas
(southeast Asia)
• Other agents include quinine, quinidine, mefloquine, fansidar (antifolate combination
drug), tetracycline, primaquine (used to eliminate exoerythocytic forms of P
...
ovale that cause relapses
...
falciparum and vivax
• P
...
5°C and 22
...
This newest
generation of the time-tested BacT/ALERT system offers advantages in every dimension of
testing
...
This configuration provides the capacity to incubate 480 culture bottles and can
be expanded to 1440 culture bottles
...

• This method uses colorimetric technology
VITEK:
The VITEK® 2 system has everything healthcare laboratories need for fast, accurate
microbial identification, and antibiotic susceptibility testing
...

The VITEK 2 system next-generation platform provides greater automation while increasing
safety and eliminating repetitive manual operations
...

Reduce time to microbial identification and antibiotic susceptibility testing results

Offer an extensive identification and susceptibility menu
Reduce waste with a miniaturized card-format that measures 10 cm x 6 cm x 0
...
Advanced Colorimetry provides:
• High discrimination between species
• Low rate of multiple choice and misidentified species
• Minimal number of off-line tests
Bacteria Cell Wall:
Gram positive bacteria have a cytoplasmic lipid membrane, a thick peptidoglycan layer
(teichoic acids and lipoids are present, forming lipoteichoic acids which serve to act as
chelating agents, and also for certain types of adherence
...

Both gram positive and negative bacteria may have a membrane called an S-layer
...

Gram negative bacteria feature a cytoplasmic membrane, a thin peptidoglycan layer (thinner
than gram positive), an outer membrane containing lipopolysaccharides
...
There is a
space between the layers of peptidoglycan and the secondary cell membrane called the
periplasmic space
...

If a flagella is present, it features 4 supporting rings not 2, also no techoic acids or
lipotechoic acids are present
...
It is based on the
chemical and physical properties of their cell walls
...
A Gram positive results in a purple/blue
color while a Gram negative results in a pink/red color
...




---