4-c The Bacteria
And various pages in additional chapters
Relationships Between Bacteria and Clinical
Features of Disease
1
Structure/Function Relationships
Differences exist between human
(eukaryotic) and bacterial (prokaryotic) cells
Many of the differences account for disease
pathogenesis
And, allow exploitation of the differences to
develop chemotherapy (antibiotics)
2
Differences Accounting for Pathogenesis
Structure
Pathogenesis
Capsule
• K-antigen
• All pathogens that cause pneumonia & meningitis
have capsules
• Haemophilus influenzae, Neisseria meningitidis,
Escherichia coli, Streptococcus pneumoniae,
Klebsiella pneumoniae, group B streptococci
Plasmids
• Antibiotic resistance (R-factor)
Outer membrane
(Gram negative)
• Endotoxin (Lipid A)
• O-antigens
Flagella
• H antigen, virulence factor
• Attachment to cells
Fimbriae
• Attachment to cells
Pili
• Spread of AB resistance genes
3
Toxins
Poisonous substances produced by
microbes
– Transported in blood
– Produce fever, cardiovascular disturbances,
diarrhea, shock
– Inhibit protein synthesis, destroy blood cells &
vessels, disrupt nervous system
4
Two Types
Exotoxin
Endotoxin
Gram positive
Product of cell
Protein
Affects cell functions
Gram negative
Part of LPS
Lipid portion (Lipid A)
Fever, weakness, aches, shock
High toxicity
Lethal dose small
Gas gangrene, tetanus,
botulism, scarlet fever
Low toxicity
Lethal dose larger
Typhoid fever, UTI,
meningococcal meningitis
5
Alcaligenes faecalis
Enterobacter aerogenes
Proteus
Azotobacter
Enterobacter sakazaki
Proteus vulgaris
Bacillus
Enterobacteriaceae
Pseudomonas aeruginosa
Bacillus anthracis
Escherichia
Salmonella
Bacillus cereus
Escherichia coli
Salmonella typhimurium
Bacillus megaterium
Gram negative
Serratia marcescens
Bacillus subtilis
Gram positive
Shigella dysenteriae
Borrelia burgdorferi
Klebsiella
Spirillum
Clostridium
Klebsiella pneumonia
Staphylococcus
Clostridium botulinum
Lactobacillus plantarum
Staphylococcus aureus
Clostridium perfringens
Micrococcus luteus
Staphylococcus epidermidis
Clostridium sporogenes
Mycobacteria
Streptococcus
Clostridium tetani
Mycobacterium leprae
Streptococci mutans
Corynebacterium diphtheria
Mycobacterium smegmatis
Streptococci pneumoniae
Corynebacterium xerosis
Mycobacterium tuberculosis
Streptococcus viridans
Enterobacter
Neisseria gonorrhoea
Treponema pallidum
Nocardia
Vibrio cholera
6
Alcaligenes faecalis
Enterobacter aerogenes
Proteus
Azotobacter
Enterobacter sakazaki
Proteus vulgaris
Bacillus
Enterobacteriaceae
Pseudomonas aeruginosa
Bacillus anthracis
Escherichia
Salmonella
Bacillus cereus
Escherichia coli
Salmonella typhimurium
Bacillus megaterium
Gram negative
Serratia marcescens
Bacillus subtilis
Gram positive
Shigella dysenteriae
Borrelia burgdorferi
Klebsiella
Spirillum
Clostridium
Klebsiella pneumonia
Staphylococcus
Clostridium botulinum
Lactobacillus plantarum
Staphylococcus aureus
Clostridium perfringens
Micrococcus luteus
Staphylococcus epidermidis
Clostridium sporogenes
Mycobacteria
Streptococcus
Clostridium tetani
Mycobacterium leprae
Streptococci mutans
Corynebacterium diphtheria
Mycobacterium smegmatis
Streptococci pneumoniae
Corynebacterium xerosis
Mycobacterium tuberculosis
Streptococcus viridans
Enterobacter
Neisseria gonorrhoea
Treponema pallidum
Nocardia
Vibrio cholera
7
Bacilli, rods
Cocci
Bacillus anthracis
Neisseria gonorrhoea
Clostridium botulinum
Staphylococcus aureus
Clostridium perfringens
Streptococci mutans
Clostridium tetani
Streptococci pneumoniae
Corynebacterium diphtheria
Escherichia coli
Curved
Vibrio cholera
Klebsiella pneumonia
Mycobacterium leprae
Spirochete
Mycobacterium tuberculosis
Borrelia burgdorferi
Treponema pallidum
8
Clinically Significant Bacteria
Arrangement: rods, bacilli
– Bacillus
– Clostridium
– Corynebacterium
– Escherichia coli
– Mycobacterium
9
Bacillus anthracis
• Gram positive, rods
• Spore forming
• Aerobe or facultative
• Found in soil
Disease:
• Anthrax
– Pulmonary
– Cutaneous
– GI
• Biological warfare
– Ch 23, p 680-1
Fig. 11.17b Bacillus
germinating
1)
2)
3)
4)
5)
Ch / Pg
3 / 71
4 / 96-97
11 / 331
23 / 679-681, 702
LM / 18-9
10
Cutaneous Anthrax
• Contact with material
containing anthrax
endospores
• Results in skin lesion
covered by a black scab
Fig. 4.21 Endospore
• Diagnosis
– New blood test
detection
Fig. 23.7 Anthrax lesion
11
Clostridium
• Gram positive, rods
• Obligate anaerobe
• Endospores
• Widely found in soil, GI
tracts human, animals
• Toxins (neuro)
Diseases:
• Botulism
• Tetanus
• Gas gangrene
• Food borne diarrhea
Fig. 23.8 gangrene
Ch / Pg
1) 11 / 330
2) 23 / 681-2, 702
3) 15 / 459-464
4) LM / 18-20
12
Gas Gangrene
• C. perfringens
• If wound is brand
new
– Prompt cleaning of
serious wounds
– Antibiotic treatment
(penicillin)
• Wound is seriously
necrotic
Fig. 23.9 Hyperbaric chamber
– Surgery, amputation
13
Corynebacterium diphtheriae
• Gram positive
• Club-shaped, pleomorphic
• Aerobic or (facultative anaerobic)
• Non-spore forming
• Toxin (cyto)
• Metachromatic granules
– Volutin
Fig. 24.5 Corynebacterium
Disease:
• Diphtheria
Ch / Pg
1)
2)
3)
11 / 335
24 / 715-6, 718
LM / 24-25
14
Diphtheria
• Airborne transmission
• Forms a leathery,
grayish membrane in
the throat
– Sore throat, fever,
general malaise,
swelling of neck
• Diagnosis:
– Selective &
differential media
Part of the DPT immunizations for children
Fig. 24.6 Diphtheria membrane
15
Escherichia coli
• Gram negative, rods
• Facultative anaerobe
• Toxins
- Invasive
- Hemorrhagic
- Plasmid borne
Fig. 4.11 E. coli
Diseases:
• Foodborne epidemics
• Urinary tract infections (‘travelers diarrhea’)
Ch / Pg
• Gastroenteritis
1) 4 / 83
– E. coli O157:H7
2) 11 / 323
3) 25 / 758-9
16
Gastroenteritis
• E. coli (EHEC)
• Hemorrhagic colitis (very
bloody stools)
• Adhere to intestinal
mucosa, destroy microvilli
• Serotype: O157:H7
• Infective dose 100 bacteria
• Diagnosis: rapid
methods
Fig. 24.6 Enterohemorrhagic E. coli
17
Mycobacterium
• Acid fast, slender rod
• Obligate aerobe
• Non-spore forming
Disease:
• Tuberculosis
• Leprosy (Hanson’s Disease)
1) Mycobacterium tuberculosis
2) M. leprae
Fig. 24.9 Mycobacterium
Ch / Pg
1) 3 / 70-1
2) 11 / 334-5
3) 22 / 651-2, 665
4) 24 / 719-723
5) LM / 21-22
18
Tuberculosis
• Inhale the bacillus
– Lodge in the lung
alveoli
– Can progress to a lung
damaging
inflammation
Fig. 24.2 Lower
Respiratory System
• Diagnosis:
– TB skin test
– Sputum smears
– Chest X ray, CT
Fig. 24.11 TB skin test
19
Leprosy
• Invades myelin
sheath, peripheral
nervous system
– Cause nerve damage
– 12 day generation time
– Never grown in culture
• Necrosis of tissue
• Diagnosis:
– Detect acid-fast rods
in patient fluids
– Lepromin test
Fig. 22.9 Leprosy
Also called Hansen’s disease
20
Clinically Significant Bacteria
Arrangement: cocci
– Neisseria gonorrhoea
– Staphylococcus aureus
– Streptococci
21
Neisseria gonorrhoea
• Gram negative
• Diplococcus
• Obligate aerobe
• Non-spore forming
Disease:
• STD: Gonorrhea
• Meningitis
Fig. 22.4 Neisseria meningitis, pharynx
Ch / Pg
1) 22 / 645-6
2) 26 / 790-793
22
Gonorrhea
• Attaches via fimbriae
• Leads to inflammation
• Leucocytes move to
infected area
– Characteristic pus
forms
• In women, only the
cervix is infected
• Diagnosis:
Fig. 26.7 A smear of pus, patient
with gonorrhea
– Stained pus smears
23
Staphylococcus aureus
• Gram positive, cocci
• Grape-like clusters
• Facultative anaerobe
• Toxin
Diseases (many):
• Surgical wounds (nosocomial)
• TSS (toxic shock syndrome)
• Skin infections (impetigo,
scalded skin)
• Endocarditis
Fig. 11.18 Staphylococcus aureus
Ch / Pg
1) 11 / 332
2) 21 / 615-20, 633
3) 23 / 674-5
24
4) 25 / 751
Acute Bacterial Endocarditis
• Gain access to
bloodstream
• Leads to infection
– Forms fibrin-platelet
vegetations
• Rapid destruction of
heart valves within
the endocardium
• Diagnosis:
Fig. 23.4 Bacterial endocarditis
– Echocardiogram
25
Clinical Ramifications, 2 types
• S. aureus and S.
epidermidis can be
divided into 2 groups
• Slime layer allows S.
epidermidis to
colonize catheters
Fig. 21.3a, b. Coagulase negative
staphylococci
Staphylococcus aureus
Staphylococcus epidermidis
Coagulase positive
Coagulase negative
Produces enterotoxins
Produces slime layer
Damage tissue
Adhere to surfaces
26
Streptococcus
• Gram positive, cocci, chains
• Facultative anaerobe
• alpha, beta, gamma
hemolytic
• Secrete toxins
Diseases (many):
•
•
•
•
•
Pneumonia
Strep throat
Scarlet fever
Skin infections
Rheumatic fever
Fig. 11.19 Streptococcus
Ch / Pg
1) 11 / 333
2) 14 / 427
3) 21 / 620-1
4) 23 / 674-6
5) 25 / 751
27
Skin Infection - Erysipelas
• Most important bhemolytic species
– S. pyogenes
• Reddish patches on
skin - dermal layer
– Tissue destruction
– Pus generated
– Enter bloodstream
cause sepsis
Fig. 21.6 Lesion of erysipelas
28
Q’s
What is seen at the ends of the cells of
Clostridium tetani in this micrograph?
1.
2.
3.
4.
5.
Very thick flagella
Endospores
The cells are undergoing division
These cells are pleomorphic, accounting for this shaped cell
Budding cells
29
Q’s
1. Which of these is NOT correctly matched?
1.
2.
3.
4.
Escherichia coli – gastroenteritis
Staphylococcus aureus – TSS
Clostridia tetani – gangrene
Bacillus anthracis – anthrax
2. Which of following is not true about
fimbriae?
1.
2.
3.
4.
5.
They are composed of protein
They may be used for attachment
They are composed of pilin
They may be used for motility
They are found on Gram negative cells
30
Q’s
1. The formation of a tough grayish membrane
in the throat is characteristic of:
1.
2.
3.
4.
Tuberculosis
Scarlet fever
Diphtheria
Streptococcal pharyngitis
2. A positive tuberculin skin test indicates that
an individual:
1.
2.
3.
4.
Has an active case of tuberculosis
May have been vaccinated with BCG
Has immunity to TB due to an earlier infection
Any of the above is possible
31
Q’s
1. Which of these is an infection of the lower
respiratory tract:
1.
2.
3.
4.
Botulism
Diphtheria
Tuberculosis
Streptococcal pharyngitis
2. An acid-fast stain of a patient’s sputum
reveals acid-fast rods. This indicates
infection with:
1.
2.
3.
4.
Staphylococcus aureus
Mycobacterium tuberculosis
Corynebacterium diphtheria
Any of the above is possible
32
Q’s
1. Which of these diseases is also known as
Hanson’s disease:
1.
2.
3.
4.
5.
Botulism
Leprosy
Tuberculosis
Gangrene
Anthrax
2. Staphylococcus aureus is responsible for all
of the following except:
1.
2.
Acne
Impetigo
3.
4.
Toxic shock syndrome
Scalded skin syndrome
33
Q’s
The diagram shows the structure of a:
1. Gram-negative cell wall
2. Gram-positive cell wall
3. Eukaryotic cell wall
34
Q’s
The antibiotic Gentamicin binds the 30S
ribosome subunit. This will interfere with:
1.
2.
3.
4.
Protein synthesis in eukaryotic cells
Protein synthesis in prokaryotic cells
Cell division in eukaryotic cells
Cell division in prokaryotic cells
35
Q’s
Disease
Bacteria
1. Bacillus
2. Streptococcus
3. Klebsiella
4. Escherichia
5. Neisseria
6. Staphylococcus
7. Mycobacterium
8. Clostridium
9. Corynebacterium
a. Leprosy
b. Diphtheria
c. Anthrax
d. Strep throat
e. Botulism
f. Hemorrhagic colitis
g. Pneumonia
h. Scarlet fever
i. Skin infections
j. Tetanus
k. Meningitis
l. Tuberculosis
m.Acute endocarditis
n. Food borne diarrhea
o. Gas gangrene
p. UTI
36