Microbiology Flashcards
1
Q
‘normal microflora Meaning
A
- The ‘normal microflora’ is the term most commonly used when
referring to the diverse species of microorganisms that consistently
inhabits the bodies of healthy animals.
2
Q
Microbiology importance
A
- They are the most successful forms of life as they have been in
the environment longest, are the most numerous and are
distributed in environments that have previously been thought
to be inhabitable (e.g. extreme pH, temperatures). - A single microbial cell is able to carry out its life processes –
growth, energy generation, independent reproduction.
3
Q
Whats a good thing bacteria and fungi help with
A
- Bacteria and fungi help to break down wastes and dead organisms and return the raw materials to the environment
- They inhabit all types of environments and
contribute to the life cycle
3
Q
History of Microbiology involved what?
A
- The Germ Theory of Disease vs Miasma
- Edward Jenner
- Louis Pasteur
- Joseph Lister
- Robert Koch
Koch’s postulate
4
Q
The Impact of Infectious Disease life expectancies
A
- Average life span:
– Bronze age 26 yrs
– Medieval Europe (400 – 1500 AD) 30 yrs
– Early 20th century 50 – 64 yrs
– Now world average 79.2(m), 82.9 (f) yrs
(USA, 78.7 yrs
5
Q
The Importance of Microbes
A
- You have more bacterial cells than human cells
- Most are beneficial
- Only a small minority of bacteria causes disease
- Pathogenic microbes globally are the most important cause
of human disease and death
6
Q
Introduction to Infectious Disease meaning of disease and infection
A
- Microorganisms that have the ability to cause diseases are
referred to as “pathogenic”. - A “disease” state is when the interaction between a
microorganism and the host (human) leads to a situation
where the interaction is detrimental to the host (human). - An infection - The invasion and multiplication of
microorganisms such as bacteria, viruses, and parasites this
often leads to a disease
7
Q
What is A bacterial pathogen and what is meant by pathogenicity
A
- A bacterial pathogen is usually defined as any bacterium that has the capacity to
cause disease. Its ability to cause disease is called pathogenicity
8
Q
What is meant by virulence
A
- Virulence provides a quantitative measure of the pathogenicity or the likelihood
of causing disease
9
Q
Whats meant by Virulence factors
A
- Virulence factors refer to the properties (gene products) that enable a
microorganism to establish itself on or within a host of a particular species and
enhance its potential to cause disease.
10
Q
What does virulence factors include
A
- Virulence factors include
- Bacterial toxins, cell surface proteins that mediate bacterial attachment,
- Cell surface carbohydrates and proteins that protect a bacterium
- Hydrolytic enzymes that may contribute to the pathogenicity of the bacterium
11
Q
Classifying micro organisms
A
- Bacteria (Bacteriology)
- Viruses (Virology)
- Fungi (Mycology)
- Parasites (Parasitology) a. Helminths (Helminthology) b. Protozoa
(Protozoology) - Algae (Phycology or algology ) Non microbial sources of infection:
- Toxins
- Prions (infectious proteinacious particles)
12
Q
Bacteria features
A
- Simplest single celled organism (0.5 – 4µm)
- Capable of independent replication.
- Multiply by cell division
- Many different species.
- 3 basic shapes
- Cocci
- Bacilli
- Spiral.
- Some live singly, some cluster into pairs or groups
- Live independently or as parasites
- Most common cause of disease in humans.
- Only 1% of bacteria cause human disease
13
Q
Viruses features
A
- Smallest infectious agent (20 - 300 nm).
Simplest microbe - Not capable of independent replication.
Hijack host cell machinery - Many different species.
- 4 basic shapes
- Polyhedral
- Spherical
- Helical
- Complex
- Obligate parasites
- Vaccines are available for many but not all
14
Q
Algae features
A
- 1 µm to several cms
- Unicellular or multicellular
- Reproduce asexually
- Only a few unicellular species cause human
disease - Some produce toxic substances
15
Q
Parasites - a. Protozoa features
A
- Are unicellular.
- Smallest animals 2 – 200 µm
- Reproduce asexually and sexually
- 4 groups: ciliates, amoeba, flagellates and sporozoans
- Live independently or as parasites
- A few cause human disease
- Are a leading cause of death in developing countries
(In 2019, 229 million cases of malaria occurred worldwide with 409, 000 deaths
down from 219 million cases of malaria 435 000 deaths in 2017 (WHO, 2020)
16
Q
Parasites - b. Helminths
A
- Range in size from microscopic to 20 metres long
- Multicellular. Each worm has both male and female organs
- 2 parasitic types: flatworms and roundworms
- Need host to complete life cycle.
- Causes human disease
- Adult lives inside hosts intestine and shed eggs or segments
- Improved sanitation is key
17
Q
Fungi features
A
- Large complex organism
- Reproduction mainly asexual, some sexual
- Two types
- Unicellular - yeasts
- Multicellular - moulds and mushrooms
- A few infect humans (mycosis)
- Source of antibiotics and toxins
18
Q
What are Prions
A
- Proteinaceous infectious particles
- No nucleic acid
- nv-CJD (when abnormal prions infect humans, the
resulting disease is known as (new) variant CJD (nvCJD)) - Cannot be cultured and no immune response elicited
- Difficult to diagnose early stages of disease using
conventional means - No vaccine currently available
- Experimental treatment options and vaccine underway
19
Q
- When considering any organism in relation to infectious disease a
number of distinctive biological characteristics must be taken into
account:
A
- Physiology (the functions and activities of the organism
including all physical & chemical processes) - Genetic make up
20
Q
Identification of Bacteria-Bacteriology?
A
- Shape of bacteria
- Bacteria may be conveniently divided into 2
groups, depending upon their ability to retain a
crystal violet-iodine dye complex when cells are
treated with acetone or alcohol (Gram stain)
21
Q
Gram positive cocci
A
Gram positive Cocci
Staphylococcus aureus
* Coagulase positive
* VS
Staphylococcus epidermidis
* Coagulase negative
22
Q
Gram positive rods
A
Gram positive rods
* Clostridium botulinum
* Bacillus cereus
* Listeria monocytogenes
23
Q
Gram Negative Cocci
A
Gram Negative Cocci
Enteric Bacteria (bacteria of the intestines)
* E. coli
* Salmonella
* Pseudomonas
* Vibrio cholerae
24
What is pili?
* Pili can attach two bacterial cells
together: sex pili are necessary for the
transfer of certain plasmids between
bacteria
25
What is flagella
* Flagella are responsible for the motility
of pathogenic bacteria and can play a
role in the production of disease
26
What is fimbriae
* Gram-negative pathogenic bacteria
may be covered in fine hairs called
fimbriae (singular: fimbria) these help
to stick to body surfaces
27
What are capsules
Capsules
* Some bacteria are enclosed
within a capsule
* This protects the bacterium,
even within phagocytes,
helping to prevent the cell
from being killed
28
What are spores
* A few species of bacteria have the ability to
produce highly resistant structures known as
endospores (or simply spores)
* These resist a range of hazardous environments,
and protect against heat, radiation, and
desiccation
29
Examples of spores
* Clostridium tetani (lockjaw) - Characterised by
muscle spasms and convulsions
* Bacillus anthracis - Infects the skin, lungs or
digestive tract and causes anthrax
30
What is slime ( in bacteria)
Slime
* Some bacteria produce slime to help
them to stick to surfaces
* Slime is produced by several types of
pathogenic microbes, and is usually
made up from polysaccharides
* The slime produced by Streptococcus
mutans enables it to stick to the
surface of teeth, where it helps to
form plaque, leading eventually to
dental caries
31
Non Gram Stainable Bacteria
Unusual Gram positive
Unusual Gram Positives
Mycoplasmas
* No cell wall
* Mycobacteria
* Acid-fast bacilli, stained by Ziehl-Neelsen stain
* M. pneumoniae; M. leprae
32
Non Gram Stainable Bacteria
Unusual Gram negatives
Unusual Gram negatives
Spirochaetes - Treponema pallidum
(syphillis)
* Viewable by phase contrast microscopy
or silver stain
33
Identifying Viruses
* Smallest infectious agent (20 - 300 nm). Simplest microbe
- No natural taxonomy
- Classified according to:
- Genome type: DNA or RNA
- Polymerase: some use reverse
transcriptase to make DNA from RNA
- Whether they have envelope or not
I-Helical Nucleocapsids
II - The icosahedron
III Enveloped
34
Genetic Factors Affecting Viral Virulence
* Viral virulence is influenced by viral genes in four categories:
* Viral virulence is influenced by viral genes in four categories:
* those that affect the ability of the virus to replicate,
* those that affect host defense mechanisms,
* those that affect tropism, (spread throughout the body and transmissibility)
* those that encode or produce products that are directly toxic to the host.
35
Bacterial Toxins
Generally, there are Two major types of bacterial
toxins
1. Endotoxins are the Lipopolysaccharideprotein complexes (LPS), responsible for
making an integral part of the cell wall of
Gram-Negative Bacteria
Endotoxins are released at the time of cell death
or lysis of bacteria.
2. Exotoxins are the proteins which are secreted
by few species of bacteria and get diffuse into
the nearby or surrounding medium.
Note -endotoxins are heat stable, weakly
immunogenic
while exotoxins are heat labile, highly
antigenic.
36
Impact of infectious diseases - Case study bacteria
Plague - a.k.a. Black Plague & Black Death
* Caused by bacteria Yersenia pestis
* Several pandemics of plagues have occurred throughout history
* 50 million deaths between years 1346 –1350
* Nearly half of Europe perished in this plague
“Plague” is caused by Yersinia pestis bacteria.
It can be a life-threatening infection if not treated promptly.
Plague has caused several major epidemics in Europe and Asia over the last 2,000 years.
Plague has most famously been called "the Black Death" because it can cause skin sores
that form black scabs.
A plague epidemic in the 14th century killed more than one-third of the population of
Europe within a few years.
In some cities, up to 75% of the population died within days, with fever and swollen skin
sores.
37
Impact of infectious diseases case study - salmonella outbreak 2012
* A Salmonella outbreak linked to watermelons has affected 35 people in
the UK
* One person has died (had serious underlying health issues)
* The Health Protection Agency (HPA, PHE) said three times the usual
number of cases of Salmonella Newport infection for this time of year had
been seen
* Cases of illness caused by the same strain have been seen in Ireland and
Germany
* 250 cases were reported in England, including 3 deaths
* Several hundreds of cases were reported other parts of Europe
* All cases were linked to consumption of Eggs from a single source
* Symptoms include diarrhoea, stomach cramps, vomiting and fever
although most people recover without treatment
38
Impact of Infectious Disease
Case study -Virus
Smallpox
* Cause - 2 airborne virus variants, Variola major and Variola minor
* Deadly disease that, in survivors, can cause disfigurement and blindness
* Approx 500 million deaths worldwide in the 20th century
* Eradicated in 1979 though widespread vaccination
* Now still possible weapon of bioterrorism
Influenza
* Infectious disease caused by RNA viruses in the family Orthomyxoviridae
* Spanish flu pandemic 1918; more than 50 million deaths
* In the U.K. seasonal flu kills thousands of people every year (mainly very
young and old)
AIDS - Acquired Immune Deficiency Syndrome
* Caused by HIV (human immunodeficiency) virus, a retrovirus that infects T-cells
* More than 25 million people have died from since it was recognised in 1981
* Around 100,000 people are living with HIV infection (diagnosed and undiagnosed)
in the UK
* With anti-retroviral drug therapy, more, and more people are living with aids
* New breakthroughs in anti-retroviral drugs can reduce contagiousness and
transmission of HIV
39
Toxins in bacteria – E. coli
* Some kinds of E. coli bacteria cause disease when they make a toxin
called Shiga toxin. The bacteria that make these toxins are called
“Shiga toxin-producing E. coli,” or STEC for short.
* Shiga toxin-producing E. coli (STEC) can cause severe foodborne
disease. Primary sources of STEC outbreaks are raw or undercooked
ground meat products, raw milk, and faecal contamination of
vegetables.
* In most cases, the illness is self-limiting, but it may lead to a lifethreatening disease including haemolytic uraemic syndrome (HUS),
especially in young children and the elderly.
* There are many kinds (called serogroups) of STEC that cause disease.
* The most commonly identified STEC in the United States
is E.coli O157:H7.
40
E. coli (STEC)
* Shiga toxin-producing STEC may also be referred to as Verocytotoxinproducing E. coli (VTEC) or enterohemorrhagic E. coli (EHEC).
* This pathotype is the one most commonly heard about in the news in
association with foodborne outbreaks.
* Enterotoxigenic E. coli (ETEC) - ETEC, is an important cause of bacterial diarrheal
illness.
* Enteroaggregative E. coli (EAEC) - Thus, EAEC are now defined as E. coli that do
not secrete heat-labile or heat-stable enterotoxins and adhere to HEp-2 cells in an
aggregative (AA) pattern
41
E. coli (STEC)
* Enteroinvasive E. coli (EIEC) - Enteroinvasive Escherichia coli (EIEC) is an intestinal
pathogen causing enteritis, with a similar pathogenic mechanism to that of Shigella,
which causes an epithelial invasion of the large bowel leading to inflammation and
ulceration of the mucosa.
* Enteropathogenic E. coli (EPEC) - Infection with enterohemorrhagic E. coli (EHEC) results
in the formation of similar lesions at the point of bacterial contact; however, these
lesions are different in composition and are localized to the terminal ileum or colon
