4. Bacteria
Size: variable depending on the species.
Nucleus: no. Mass of DNA without nuclear
membrane, formed by a single chromosome.
Cell wall: yes, formed of liposaccharides and
lipoproteins
DEFINITIONS
5. Bacteria
Bacteria are small single celled organisms that are
not visible to the naked eye and have a very
primitive structure.
8. Fungi
Kingdom: vegetable,
Size : a few microns,
Nucleus : true.
2 types : yeasts and
dermatophytes
Example of yeasts : Candida albicans
Mycosis
9. FUNGI
Fungi resemble primitive plants and live on dead
organic matter they can exist as single cells (yeast) or as
many cells (called mycelium)
10. Virus
Size: between 20 and 200 millimicrons
(visible under the electron microscope),
Nucleus : no. Nucleic acid core
(DNA or RNA) contained in an
envelope (capsid).
They invade the human, bacterial, plant or animal
cells to survive Example : Myxovirus = Flu virus
11. VIRUSES
Viruses are the smallest and simplest of all organisms
and can only be seen with powerful electron
microscopes. Viruses cannot multiply by themselves and
so have to invade host cells to allow multiplication.
12. Bacterial structure
Constant Elements :
Bacterial "nucleus"
= chromosomic DNA
Cell wall
Cytoplasmic
membrane
Cytoplasm
Ribosomes
(synthesis of proteins and nutritive reserves of the bacterium)
13. Optional elements :
Bacterial structure
Pili
(tissue binding,
transmission of plasmids)
Plasmid (DNA fragments carrying genes of resistance)
Flagella
(motility)
Capsule
(resistance to phagocytosis)
14. Characteristics of all bacteria:
All bacteria possess 5 basic components:
- Cell wall
- Cytoplasmic membrane
- Cytoplasm
- Ribosomes
- Nuclear material
Some bacteria possess:
- Flagella
- Pili
- Capsules
19. Bacterial classification
Difficulty in classification: Unlike higher
organisms, bacteria lack sufficient variations
in structure upon which normal classifications
can be made. Basic criteria Most of the
systems developed to classify bacteria utilise
these diagnostic criteria
- Shape (morphology) and culture
characteristics
- Staining – Gram Stain
- Culturing and biochemical tests
- Growth requirement for oxygen; i.e. aerobic or
anaerobic
31. Genus :
Haemophilus Streptococcus
Species :
influenzae para influenzae pneumo- b hemolytic group B
coccus group A group C
group D etc.
Serotypes :
a, b, c, d, etc etc. 23F,9, 6,14 etc.
(+ of 80 different serotypes) (+ of 80 different serotypes)
The bacterial strain is a colony resulting from a sample and a
particular serotype, obtained from sucessive subcultures ("clones").
BACTERIOLOGY:
Concept of bacterial strain
32. Aerobic Pathogens
COCCI +
• Staphylococcus:
– aureus
– epidermidis
• Streptococcus:
– S. pneumoniae
– S. group A b hemolytic
– S. group B
– S. viridans
– S. group D = S. foecalis
COCCI -
• Neisseriae:
– meningitidis
– gonorrhae
• Moraxella catarrhalis
36. DEFINITIONS
INFECTION =
A sequence of repercussions which result in an attack on
a living organism by a ± virulent pathogen.
Endogen or exogen
Infection involves 3 actors :
PATHOGEN
HOST THERAPY
37. DEFINITIONS
INFECTION
2 types of clinical sign:
Typical symptoms Local symptoms
The symptoms indicate
the illness and
the pathogen responsible.
An organ is suffering.
Experience points
to a pathogen.
38. Streptococcus pneumoniae
Gram + Cocci
HABITAT: Commensal (organism that derives
food or other benefits from another organism
without hurting or helping it (50 % of individual
carriers, and more in winter).
PATHOGENIC POWER: Very virulent
(capsule),
– leader as regards mortality of bacterial origin,
– responsible for the majority of cases of acute
lobar pneumonia, otitis, adult meningitis,
sinusitis
39. Gr A b hemolytic streptococcus
Gram + Cocci
HABITAT: Strictly human bacterium.
Commensal
PATHOGENIC POWER: Very virulent (capsule, toxin etc.),
responsible for ENT (tonsillitis, otitis etc.) and cutaneous
infections (impetigo, erysipelas etc.)
COMPLICATIONS: rheumatic fever, glomerulonephritis, endocarditis
40. Staphylococcus aureus
Gram + Cocci
HABITAT: Human, soil, air, water.
PATHOGENIC POWER: Very virulent (capsule, toxins,
enzymes, etc.), responsible for cutaneous, osseous, pulmonary
and cerebral infections, and for superinfection after
severe burns. Responsible for septicemia and endocarditis.
41. Haemophilus Influenzae
Gram - Bacillus
HABITAT: Flora of upper respiratory tract. 75% of children under
5 are healthy carriers.
PATHOGENIC POWER: 35 to 50% of otitis, sinusitis,
rhinopharyngitis, superinfection of chronic bronchitis or of viral
illnesses. Meningitis and septicemia are due to encapsulated forms
(H.i.b.). A vaccine against encapsulated Haemophilus exists.
The vaccination must be performed at the age of 3 to 4 months
with a booster at 14 or 16 months to be effective.
42. Moraxella catarrhalis
Gram - Cocci
HABITAT: Commensal of the respiratory mucus.
PATHOGENIC POWER: Superinfection of chronic bronchitis,
otitis, sinusitis
44. Salmonella
Gram - Bacillus (enterobacteria)
HABITAT: Parasite of the human and animal digestive tract.
Contamination by oral route.
PATHOGENIC POWER:
Digestive forms : Toxi-infections (gastro-enteritis)
Septicemic forms : Typhoid (S.typhi) or paratyphoid
(S.paratyphi) fever
The septicemic forms can become complicated (pulmonary, meningeal,
osseous, digestive infections etc
45. Shigella
Gram - Bacillus (enterobacteria)
HABITAT: Human digestive tract. Contamination through food, or
water contaminated with fecal matter.
PATHOGENIC POWER: Infectious colitis, gastro-enteritis
(children). Bacillary dysentery (army on march).
46. Escherichia Coli
Gram - Bacillus (enterobacteria)
HABITAT: Normally found in human digestive tract.
PATHOGENIC POWER:
Intestinal infections: Infectious diarrhea
Urinary infections: Responsible in up to 90%
Abdominal infections: Peritonitis, salpingitis,
cholecystitis
Meningeal infections: Meningitis in infants or elderly
patients
47. Mycoplasma pneumoniae
HABITAT: Micro-organisms without cell wall, intracellular or
associated to cells; vegetable, animal, and human parasite.
PATHOGENIC POWER:
Atypical pneumonia : Young adults, particularly in fall
and winter.
48. Intracellular
Chlamydia
HABITAT: Strict intracellular parasite of small size.
3 SPECIES: Chlamydia pneumoniae
Chlamydia psittaci
Chlamydia trachomatis
TREATMENT: Macrolides, fluoroquinolones
Non specific urethritis (50% of cases)
Post-gonococcal urethritis (20 to 60% of cases)
Cervicitis, salpingitis, rectitis
Pneumonias in newborn babies
Conjunctivitis in newborn babies and adults
49. Intracellular
Legionella pneumophila
HABITAT: Bacterium of the environment (lake water, air
conditioning). The entry port for the infection is pulmonary.
PATHOGENIC POWER:
Acute pneumonia: pseudo-flu state, dry cough, gastro-
intestinal disorders etc.
Especially in debilitated subjects of + 50 ans (tabacco, alcohol,
immunodepression)
Pathology fatal without treatment: 20% of cases
51. What are the opportunities for a
bacterium to become pathogenic ?
Migration
Immunodepression
Antibiotic
Physiological
change
..
52. 1/ Endogenous infectious illness =
rupture of the bacterial ecosystem (saprophyte flora) and
proliferation of a bacterial species.
2/ Exogenous infectious illness =
penetration of pathogens within
proliferation the organ
How do they proliferate?
How are they pathogenic?
How do they penetrate?
How is bacterial infection or
pathogenesis triggered?
53. 1/ How do they proliferate?
In favorable environments :
• in presence or in absence of oxygen,
• in presence of nutrients and space,
• humidity,
• optimal temperature
By mitosis
54. 2/ How are they pathogenic ?
Pathogenic power or "Virulence"
2 principal factors of virulence
1. Invasion
+ or - rapid
2. Toxicity
Secretion of
sometimes fatal
toxins S
S
S
S
S
S
S S
S
S
S
SS
S
S
S
S
S
Exotoxins Endotoxins
55. Other factors of bacterial
virulence
Bacterium Host
Pili Capsule
Enzymes - extreme age
- weakened
general state,
- iatrogenic factors ,
- entry port: wound or
surgery.
56. 3/ How do they penetrate ?
The entry ports
Skin
Mucus
Respiratory
tract
Digestive
tract
57. Program of bacterial
"excursions"
Surface infection: the pathogens multiply on the surface of
mucus,
Infectious site: the pathogens multiply in the tissues close to the
entry port,
Targeting of organ: tropism relative to certain organs,
Bacteriemia: passage of pathogens into the blood or the lymph
system with no morbid effect,
Septicemia: massive passage of pathogens into the blood
Infestation of the whole organism, multiple sites of infection.
58. How does the human
organism defend itself ?
1st line:
• Physical resources,
• Chemical resources,
• Bacteriological resources,
After introduction:
• Non specific reaction: inflammatory reaction,
• Specific reaction: immune system
immune reaction
..
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..
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..
59. 1/ A hermetic barrier = the skin
Sebaceous gland
Sweat
Sebum
Sweat gland
Keratinous
cells
64. 1/ The non specific
inflammatory reaction
1/ VASODILATATION
2/ PLASMA LEAK
.
. .
. .
.
3/ FORMATION OF
FIBRINE MESH
4/ PHAGOCYTOSIS
65. 1/ The non specific inflammatory
reaction : PHAGOCYTOSIS
Two types of phagocytary cells:
Polynuclear
Macrophages
1/ Chemotaxis
2/ Adhesion
3/ Invagination 4/ Digestion
66. 2/ The specific immune reaction
LYMPHOCYTES =
immunocompetent cells
B
T Action on contact
Circulating antibodies
Humoral immunity
Cellular
immunity
67. 2/ The specific immune reaction
Marrow and Thymus
lymph vessels
and glands
blood
vessels
Production
of lymphocytes
Transport by
During infection the glands swell and become painful
(adenopathy).
68. A- The humoral immune
reaction
. . . . B
B
Specific
antigen-antibody reaction
.
.
.
.
.
T4
PP
PP
PP
PP
Plasmocytes
antibodies
69. A- The humoral immune
reaction
. . . . B
B
.
.
.
.
T4
Bm
Memorization
= Immunity acquired
The lymphocytes which are not transformed into plasmocytes producing
antibodies keep the antigen and the antibody fabrication mode in memory.
70. B- The cellular immune
reaction
. . . . T
.
.
.
T4
T
Te
Te
Te
Tm
Memory
T4 lymphocytes
T lymphocyte "effectors"
71. The immune reaction: the T4
T4
T
B
Humoral immunity
Cellular immunity
B lymphocyte secreting
remote antibody
Cytotoxic
T lymphocyte
Preponderant role
of T4
73. If the infection is triggered despite
the defenses...
What is its origin ? What type of treatment?
viral ? antiviral
parasite ? antiparasite
bacterial ? antibiotics
mycotic ? antifungal
Infections can be mixed: bacteria + fungi.
The infections can be successive: bacterial superinfection of an
infection of viral origin
74. What is
bacterial superinfection?
"The virus prepares the bacterium's nest."
Alteration of healthy cells by the virus
Tissue lesions Inflammatory Inflammatory
tissue response pathology
Disturbance of functions (e.g. cold)
+ Alteration of defense mechanisms
Invasion by bacteria
Bacterial superinfection Aggravation of tissue lesions
75.
76. Definition:
An antibiotic is a substance produced by micro-
organisms, or which can be reproduced
synthetically, which possesses the property of
destroying bacteria or of inhibiting the growth
of bacteria.
Study of an
ANTIBIOTIC
77. Mechanism of action
Process inhibition by antibiotics.
Antibacterial agents act by effecting one or
more of the following processes taking place
inside bacterial cells:
The synthesis of the cell wall.
The functioning of the cell membrane
The synthesis of proteins
The synthesis of nuclear material (DNA)
Metabolic transformations
80. Spectrum of activity
This is the range of bacteria that are
sensitive to the antibiotic (inhibited or
killed)
Study of an
antibiotic
Cocci +
Cocci -
Bacillus +
Bacillus -
Cocci + Narrow spectrum
Broad spectrum
81. Activity : determined in laboratory
in a number of ways:
Antibiogram Dilution method
by diffusion
with disks
on agar
Study of an
antibiotic
Several antibiotics can
be studied at the same
time
One antibiotic can be
studied at a time
82. Activity : determined by identifying the MIC and MBC for
each common pathogen
MIC = Minimum Inhibiting Concentration
the minimum concentration of antibiotic capable of stopping the
culture of a given strain in a medium
Study of an
antibiotic
X quantity of germs
in the inoculum
X quantity of germs
after culture
83. MBC = Minimum Bactericidal Concentration
the minimum antibiotic concentration destroying 99.99 %
of a bacteria population
after 18 hours of contact at 37°
Study of an antibiotic
X quantity of germs
in the inoculum
< 1 pathogen alive
out of 10 000
84. Dilution method:
determining the MIC
MIC = Minimum Inhibiting Concentration
the minimum concentration of antibiotic capable of stopping
all culture of a given strain in a medium (37° for 24 hours)
MIC
Control 0,25 0,50 1 2 4 8 16 32 mg/ml
86. MBC
1/10 000 = 10
102
105
104
103
106
107
108
109
2 4 6 8 10 12 14 18
8 mg
4 mg
2 mg
1 mg
0,5 mg
Control
0,25 mg
Number of
bacteria / ml
Time
(hours)
Inoculum
MBC
MIC
C
o
n
c.
of
A
B
T
92. Study of an antibiotic
Pharmacokinetics :
study of the behavior and fate of an antibiotic in the organ from
administration to elimination
AbsorptionMetabolization
Diffusion
Elimination
95. Pharmacokinetics: definitions
• absorption: % of the dose of active principle administered
passing through the intestinal mucus into the blood.
• metabolization: the transformation of the active principle
into active or inactive metabolite, principally in the liver.
• effect of first hepatic passage: presence of hepatic
metabolism.
• bioavailability: the result of the previous 2 criteria; the %
of the quantity of active principle administered arriving in
the blood stream.
96. Pharmacokinetics : example
administration via oral route of 100 mg of active principle,
absorption = 80 % 80 mg,
metabolization (hepatic first pass) = 20 % into inactive
metabolite 16 mg,
64 mg will reach the target
Bioavailability will therefore be 64 %
97. Pharmacokinetics : definitions
distribution or diffusion: passage of the active compound from
the blood stream into the tissues (site of the infection ?).
binding to plasma proteins:
% of the active compound circulating binding to proteins.
Plasma protein
TRANSPORTER
101. Pharmacokinetics :
The plasma elimination 1/2 life
Plasma
concentration
Time
Plasma peak
C max
T max T /
2
C / 2
1/2 life
elimination phase =
distribution, metabolization
and elimination
absorption
phase
102. Pharmacokinetics :
Notion of area under the curve
Plasma
concentratio
n
Time
Plasma peak
C max
T max
MIC
The larger the area below the serum concentration curve,
the better the impregnation of the organ by the antibiotic
103. Pharmacokinetics =
criteria of choice of an antibiotic
maximum absorption,
tissue diffusion at the site of the infection +++,
intra-cellular diffusion +++,
elimination in non-toxic active form via the
kidney or the bile depending on the infection,
long half-life.
104. Criteria of choice of an antibiotic
Bacteriology
Pharmacokinetics
Type of patient
Side effects
Compliance
Ecology
Economy
Major
criteria
Secondary
criteria
108. Mechanism of action
Beta lactam antibiotics inhibit cell wall
synthesis by binding to the Penicillin
Binding Proteins (PBP’s) on the outer
surface of the cytoplasmic membrane.
Once they bind to these PBP’s /
enzymes, they stop the process of cell
wall formation / division or replication
(depending on the PBP affected).
109. Mechanism of bacterial resistance
Bacteria can resist the action of beta lactam antibiotics in 3
main ways:
Potential production of beta lactamase enzymes that will
hydrolyse (destroy) the beta lactam ring of the antibiotic
(mainly a problem with 1st generation penicillins and
cephalosporins against gram negative bacteria – the beta
lactamase enzymes can be concentrated in the periplasmic
space)
Potential for porin channels in gram-negative bacteria to
resist entry to some types of beta lactam antibiotics by
altering their electrochemical charge
Potential for alteration of the target binding sites (Penicillin
binding proteins may change so the antibiotics cannot
attach themselves to the site. Alternatively the bacteria
may produce alternate PBP's’ that the antibiotic will bind to
– the new PBP’s serve as decoys and have no function in
cell wall synthesis – this is a significant problem with many
gram positive bacteria and some gram negative bacteria)
110. Examples :
Staphylococcus aureus
Haemophilus influenzae
Moraxella catarrhalis
Escherichia coli
Bacterial resistance:
a / Production of enzymes : b Lactamases
Resistance can
be transmitted
with plasmids
115. Mode of action
Interfere with protein synthesis and may
form transient holes in a cell wall to
disrupt the permeability function.
116. Mechanism of bacterial resistance
Bacteria may defend themselves against aminoglycosides by some
combination of three mechanisms:
Enzymatic modification: The bacteria has the potential to modify the
chemical structure of the aminoglycoside prior to it reaching the
ribosomes. The alteration renders the antibiotic useless by a process
of ATP-dependent phosphorylation of a hydroxy group or acetylation
of an amino group (enzymes break down the structure of the
antibiotic)
Alteration in uptake: Potential alterations in the electrochemical charge
in the outer membrane will not allow the aminoglycoside to gain entry
Altered ribosomal binding sites: This is the least common method that
bacteria may develop resistance. A mutation will alter the binding site
so that an aminoglycoside will not recognise the appropriate target
area on the ribosome.
Examples: Gentamicin, Neomycin, Streptomycin, and Amikacin.
119. Mechanism of resistance
There are 3 main resistance mechanisms:
Decreasing the influx into the bacterial cell: The gram-negative
bacteria may alter the outer membrane charge to prevent entry
to some tetracyclines
Increasing the efflux of the antibiotic out of the cell: Once inside
the cell some bacteria have developed mechanisms that act as
pumps to export the antibiotic from the cytoplasm before it can
exert its mechanism of action
Alteration of the ribosomal binding site: Some bacteria may
alter the ribosomal binding site so that the antibiotic will have no
target to affect.
Examples: Tetracyclines: Doxycycline (Doryx, Vibramycin),
Minocycline
123. Mode of action
Interfere with the synthesis of DNA
(gyrase and topoisomerase IV)
124. QUINOLONES :
Mode of action
On the
DNA
INHIBITION
of DNA synthesis
bactericidal
the bacterium
can no longer
multiply,
or live.
125. Mechanism of resistance
Bacteria acquire resistance to quinolones by
2 methods:
Spontaneously occurring mutations in
chromosomal genes that either alter the
target enzymes or DNA
Alteration of the drugs permeation across
bacterial cell membranes
Examples: Ciprofloxacin (Ciproxin),
Moxifloxacin (Avalox), Ofloxacin (Oflocet),
Grepafloxacin (new molecule)
127. FLUOROQUINOLONES:
Spectrum
Ciprofloxacin, gatifloxacin, gemifloxacin, levofloxacin,
moxifloxacin, ofloxacin
Cocci + Cocci -
Staphylococcus Gonococcus
Meningococcus
Bacillus -
E.coli, Proteus vulgaris
Klebsielle (IS), Salmonella
Citrobacter (IS), P.mirabilis
Campylobacter, Pseudomonas aeruginosa(IS), Serratia (IS).
Intracellular,
Mycoplasma () Legionella Chlamydia,Rickettsia
Haemophilus,
S
P
E
C
T
R
U
M
W
I
D
E
130. Mode of action
Binds to the 50S ribosomal subunit
resulting in blockage of transpeptidation.
(Binds to ribosome to stop amino acid
chains – proteins being produced inside
the bacteria).
131. MACROLIDES :
Site of action
On the
ribosomes:
fraction 50 S
Inhibition of
protein synthesis
Dependent on
concentration in situ
bactericidal bacteriostatic
Inhibition of
translocase
132. Mechanism of resistance
Bacteria can develop resistance to macrolides in
two ways:
Promotion of efflux pumps within the cell to expel
the antibiotic prior to exerting the mechanism of
action. Some of these bacteria will remain
susceptible if higher doses are given.
Alteration in the ribosomal target binding site.
Changing the target for the antibiotic so that it has
no binding potential.
Examples: Erythromycin, Roxithromycin (Rulide) and
Clarithromycin
134. MACROLIDES :
Spectrum
erythromycin, azithromycin,
clarithromycin, dirithromycin
Cocci + Cocci -
Staphylococcus Meti S Gonococcus
Gr A b hemolytic streptococcus Meningococcus
Pneumococcus(IS) Moraxella
Intracellular Bacillus +
Mycoplasma Listeria, diphtheria B.
Chlamydia, Legionella Bacillus -
Helicobacter, Vibrio cholerae
Anaerobes: (+) Clostridium perfringens,
P. acnes, Peptostreptococcus., Actinomyces.
Protozoan
Toxoplasma
135. 6. KETOLIDES:
Site of action
On the
ribosomes:
fraction 50 S
• Stops protein synthesis, then
bacterial lysis
2 components act in synergy:
• the first binds to the bacterial ribosome,
• the 2nd then binds in turn
137. KETOLIDES
TOXICITY : 0 to + + occasional hepatic toxicity
SIDE EFFECTS : + to + + occasional hepatic toxicity
RESISTANCE : + to + + +
CONTRA-INDICATIONS : + +
PHARMACOKINETICS :
BIOAVAILABILITY : 40 to 80%
TISSUE DIFFUSION : very good
ELIMINATION : biliary in active or inactive form
144. Intrinsic and Acquired Resistance
Intrinsic resistance
- Intrinsic resistance means that the bacterium has always
been resistant to a particular antibiotic or that particular
antibiotic has no intrinsic activity against the bacterium. For
example, E.coli has intrinsic resistance to Rulide and
Chlamydia has intrinsic resistance to Amoxycillin.
Acquired resistance
- Acquired resistance means that the bacteria used to be
sensitive to a particular antibiotic but it has now developed a
mechanism to prevent the antibiotic from killing it. It’s a bit
like Charles Darwin’s theory of evolution, in that only those
organism that are able to evolve in order to survive will be
around in the future. MRSA has acquired resistance to
Methicillin, H.flu has acquired resistance to amoxycillin.