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Relationships Between Bacteria and Clinical Features of Disease

4-c The Bacteria4-c The BacteriaAnd various pages in additional chapters

2

Differences exist between human (eukaryotic) and bacterial (prokaryotic) cells

Structure/Function RelationshipsStructure/Function Relationships

Many of the differences account for disease pathogenesis

And, allow exploitation of the differences to develop chemotherapy (antibiotics)

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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

Differences Accounting for Pathogenesis

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Toxins 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

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Exotoxin Endotoxin

Gram positive Gram negative

Product of cell Part of LPS

Protein Lipid portion (Lipid A)

Affects cell functions Fever, weakness, aches, shock

High toxicity Low toxicity

Lethal dose small Lethal dose larger

Gas gangrene, tetanus, botulism, scarlet fever

Typhoid fever, UTI, meningococcal meningitis

Two Types

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Alcaligenes faecalis

Azotobacter

Bacillus

Bacillus anthracis

Bacillus cereus

Bacillus megaterium

Bacillus subtilis

Borrelia burgdorferi

Clostridium

Clostridium botulinum

Clostridium perfringens

Clostridium sporogenes

Clostridium tetani

Corynebacterium diphtheria

Corynebacterium xerosis

Enterobacter

Enterobacter aerogenes

Enterobacter sakazaki

Enterobacteriaceae

Escherichia

Escherichia coli

Gram negative

Gram positive

Klebsiella

Klebsiella pneumonia

Lactobacillus plantarum

Micrococcus luteus

Mycobacteria

Mycobacterium leprae

Mycobacterium smegmatis

Mycobacterium tuberculosis

Neisseria gonorrhoea

Nocardia

Proteus

Proteus vulgaris

Pseudomonas aeruginosa

Salmonella

Salmonella typhimurium

Serratia marcescens

Shigella dysenteriae

Spirillum

Staphylococcus

Staphylococcus aureus

Staphylococcus epidermidis

Streptococcus

Streptococci mutans

Streptococci pneumoniae

Streptococcus viridans

Treponema pallidum

Vibrio cholera

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Alcaligenes faecalis

Azotobacter

Bacillus

Bacillus anthracis

Bacillus cereus

Bacillus megaterium

Bacillus subtilis

Borrelia burgdorferi

Clostridium

Clostridium botulinum

Clostridium perfringens

Clostridium sporogenes

Clostridium tetani

Corynebacterium diphtheria

Corynebacterium xerosis

Enterobacter

Enterobacter aerogenes

Enterobacter sakazaki

Enterobacteriaceae

Escherichia

Escherichia coli

Gram negative

Gram positive

Klebsiella

Klebsiella pneumonia

Lactobacillus plantarum

Micrococcus luteus

Mycobacteria

Mycobacterium leprae

Mycobacterium smegmatis

Mycobacterium tuberculosis

Neisseria gonorrhoea

Nocardia

Proteus

Proteus vulgaris

Pseudomonas aeruginosa

Salmonella

Salmonella typhimurium

Serratia marcescens

Shigella dysenteriae

Spirillum

Staphylococcus

Staphylococcus aureus

Staphylococcus epidermidis

Streptococcus

Streptococci mutans

Streptococci pneumoniae

Streptococcus viridans

Treponema pallidum

Vibrio cholera

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Bacillus anthracis

Borrelia burgdorferi

Escherichia coli

Klebsiella pneumonia

Mycobacterium leprae

Staphylococcus aureus

Neisseria gonorrhoea

Vibrio cholera

Bacilli, rods Cocci

Curved

Spirochete

Clostridium botulinum

Clostridium perfringens

Clostridium tetani

Corynebacterium diphtheria

Mycobacterium tuberculosis

Streptococci mutans

Streptococci pneumoniae

Treponema pallidum

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Clinically Significant BacteriaClinically Significant Bacteria

Arrangement: rods, bacilli

– Bacillus

– Clostridium

– Corynebacterium

– Escherichia coli

– Mycobacterium

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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

Ch / Pg

1) 3 / 712) 4 / 96-973) 11 / 3314) 23 / 679-681, 7025) LM / 18-9

Fig. 11.17b Bacillus germinating

• Contact with material containing anthrax endospores

• Results in skin lesion covered by a black scab

• Diagnosis– New blood test

detection

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Cutaneous Anthrax

Fig. 4.21 Endospore

Fig. 23.7 Anthrax lesion

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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

1) 11 / 3302) 23 / 681-2, 7023) 15 / 459-4644) LM / 18-20

Ch / Pg

Fig. 23.8 gangrene

• C. perfringens• If wound is brand

new– Prompt cleaning of

serious wounds– Antibiotic treatment

(penicillin)

• Wound is seriously necrotic– Surgery, amputation

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Gas Gangrene

Fig. 23.9 Hyperbaric chamber

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Corynebacterium diphtheriae

• Gram positive• Club-shaped, pleomorphic • Aerobic or (facultative anaerobic)

• Non-spore forming• Toxin (cyto)• Metachromatic granules

– VolutinDisease:

• Diphtheria 1) 11 / 335

2) 24 / 715-6, 718

3) LM / 24-25

Ch / Pg

Fig. 24.5 Corynebacterium

• Airborne transmission• Forms a leathery,

grayish membrane in the throat– Sore throat, fever,

general malaise, swelling of neck

• Diagnosis:– Selective &

differential media

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Diphtheria

Fig. 24.6 Diphtheria membrane

Part of the DPT immunizations for children

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Escherichia coli

Fig. 4.11 E. coli

• Gram negative, rods• Facultative anaerobe• Toxins

- Invasive- Hemorrhagic- Plasmid borne

Diseases: • Foodborne epidemics• Urinary tract infections (‘travelers diarrhea’)• Gastroenteritis

– E. coli O157:H71) 4 / 832) 11 / 3233) 25 / 758-9

Ch / Pg

• E. coli (EHEC)

• Hemorrhagic colitis (very bloody stools)

• Adhere to intestinal mucosa, destroy microvilli

• Serotype: O157:H7

• Infective dose 100 bacteria

• Diagnosis: rapid methods

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Gastroenteritis

Fig. 24.6 Enterohemorrhagic E. coli

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Mycobacterium

• Acid fast, slender rod• Obligate aerobe• Non-spore forming

Disease:

• Tuberculosis• Leprosy (Hanson’s Disease)

Fig. 24.9 Mycobacterium

1) Mycobacterium tuberculosis2) M. leprae

Ch / Pg

1) 3 / 70-12) 11 / 334-53) 22 / 651-2, 6654) 24 / 719-7235) LM / 21-22

• Inhale the bacillus– Lodge in the lung

alveoli – Can progress to a lung

damaging inflammation

• Diagnosis:– TB skin test– Sputum smears– Chest X ray, CT

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Tuberculosis

Fig. 24.2 Lower Respiratory System

Fig. 24.11 TB skin test

• 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 20

Leprosy

Fig. 22.9 Leprosy

Also called Hansen’s disease

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Arrangement: cocci

Clinically Significant BacteriaClinically Significant Bacteria

– Neisseria gonorrhoea

– Staphylococcus aureus

– Streptococci

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Neisseria gonorrhoea

• Gram negative • Diplococcus • Obligate aerobe• Non-spore forming

Disease:

• STD: Gonorrhea• Meningitis Ch / Pg

1) 22 / 645-62) 26 / 790-793

Fig. 22.4 Neisseria meningitis, pharynx

• Attaches via fimbriae• Leads to inflammation• Leucocytes move to

infected area– Characteristic pus

forms

• In women, only the cervix is infected

• Diagnosis:– Stained pus smears

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Gonorrhea

Fig. 26.7 A smear of pus, patient with gonorrhea

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Staphylococcus aureus

Diseases (many):

1) 11 / 332 2) 21 / 615-20, 6333) 23 / 674-54) 25 / 751

Ch / Pg

• Gram positive, cocci• Grape-like clusters• Facultative anaerobe• Toxin

Fig. 11.18 Staphylococcus aureus

• Surgical wounds (nosocomial)• TSS (toxic shock syndrome)• Skin infections (impetigo,

scalded skin)• Endocarditis

• Gain access to bloodstream

• Leads to infection– Forms fibrin-platelet

vegetations

• Rapid destruction of heart valves within the endocardium

• Diagnosis:– Echocardiogram

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Acute Bacterial Endocarditis

Fig. 23.4 Bacterial endocarditis

• S. aureus and S. epidermidis can be divided into 2 groups

• Slime layer allows S. epidermidis to colonize catheters

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Clinical Ramifications, 2 types

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

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Streptococcus

Diseases (many):

1) 11 / 333 2) 14 / 4273) 21 / 620-14) 23 / 674-65) 25 / 751

Ch / Pg

• Gram positive, cocci, chains• Facultative anaerobe• alpha, beta, gamma hemolytic• Secrete toxins

Fig. 11.19 Streptococcus• Pneumonia• Strep throat• Scarlet fever• Skin infections• Rheumatic fever

• Most important -hemolytic species– S. pyogenes

• Reddish patches on skin - dermal layer– Tissue destruction– Pus generated– Enter bloodstream

cause sepsis

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Skin Infection - Erysipelas

Fig. 21.6 Lesion of erysipelas

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What is seen at the ends of the cells of Clostridium tetani in this micrograph?

1. Very thick flagella2. Endospores3. The cells are undergoing division4. These cells are pleomorphic, accounting for this shaped cell5. Budding cells

Q’sQ’s

30

1. Which of these is NOT correctly matched?

1. Escherichia coli – gastroenteritis

2. Staphylococcus aureus – TSS

3. Clostridia tetani – gangrene

4. Bacillus anthracis – anthrax

2. Which of following is not true about fimbriae?

1. They are composed of protein

2. They may be used for attachment

3. They are composed of pilin4. They may be used for motility

5. They are found on Gram negative cells

Q’sQ’s

31

1. The formation of a tough grayish membrane in the throat is characteristic of:

1. Tuberculosis

2. Scarlet fever

3. Diphtheria

4. Streptococcal pharyngitis

2. A positive tuberculin skin test indicates that an individual:

1. Has an active case of tuberculosis

2. May have been vaccinated with BCG

3. Has immunity to TB due to an earlier infection

4. Any of the above is possible

Q’sQ’s

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2. An acid-fast stain of a patient’s sputum reveals acid-fast rods. This indicates infection with:

1. Which of these is an infection of the lower respiratory tract:

1. Botulism

2. Diphtheria

3. Tuberculosis

4. Streptococcal pharyngitis

1. Staphylococcus aureus

2. Mycobacterium tuberculosis

3. Corynebacterium diphtheria

4. Any of the above is possible

Q’sQ’s

33

1. Which of these diseases is also known as Hanson’s disease:

1. Botulism

2. Leprosy

3. Tuberculosis

4. Gangrene

5. Anthrax

2. Staphylococcus aureus is responsible for all of the following except:

1. Acne

2. Impetigo

Q’sQ’s

3. Toxic shock syndrome

4. Scalded skin syndrome

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The diagram shows the structure of a:

1. Gram-negative cell wall

2. Gram-positive cell wall

3. Eukaryotic cell wall

Q’sQ’s

35

The antibiotic Gentamicin binds the 30S ribosome subunit. This will interfere with:

1. Protein synthesis in eukaryotic cells

2. Protein synthesis in prokaryotic cells

3. Cell division in eukaryotic cells

4. Cell division in prokaryotic cells

Q’sQ’s

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a. Leprosyb. Diphtheriac. Anthraxd. Strep throate. Botulismf. Hemorrhagic colitisg. Pneumoniah. Scarlet fever i. Skin infectionsj. Tetanusk. Meningitisl. Tuberculosism.Acute endocarditisn. Food borne diarrheao. Gas gangrenep. UTI

Disease

1. Bacillus

2. Streptococcus

3. Klebsiella

4. Escherichia

5. Neisseria

6. Staphylococcus

7. Mycobacterium

8. Clostridium

9. Corynebacterium

BacteriaQ’sQ’s