Diseases caused by bacterial infections

Bacterial skin diseases

Introduction

Intact skin surface – prevents microbes from entering the body

Normal microflora – inhibit growth of pathogens

Oil gland – secret organic acid and lipids; reduce pH thus inhibit growth of pathogens

Sweat gland - Secret organic substances; reduce pH and inhibit pathogen growth

Staphylococci: Gram positive cocci ( from Greek staphyle,

means bunch of grapes ) that occur singly and in pairs, short chains and irregular grape-like

clusters.

Morphology of Staphylococcus Morphology of Staphylococcus

Enzymes1. Coagulase

– Triggers blood clotting– Used for detection of S. aureus

2. Hyaluronidase– Breaks down hyaluronic acid, enabling

the bacteria to spread between cells3. Staphylokinase

– Dissolves fibrin threads in blood clots, allowing Staphylococcus aureus to free itself from clots

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Enzymes (cont.)

4. Lipases– Digest lipids, allowing staphylococcus to grow on the

skin’s surface and in oil glands5. -lactamase

– Breaks down penicillin– Allows the bacteria to survive treatment with -lactam

antimicrobial drugs6. Catalase– able to convert hydrogen peroxide to water and oxygen

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1) Staphylococcal infections

1) Diseases : folliculitis,boilPathogens : Staphylococcus aureus, PseudomonasTransmission : touching, hospital personnel,

nasal droplets etcPathogenesis : invade the skin through hair follicle

How can hair follicle

damaged??

Superficial folliculitis:1)Clusters of small red or pus-filled bumps that develop around hair follicles2)Pus-filled blisters that break open and crust over3)Red and inflamed skin4)Itchiness or tenderness

Deep folliculitis 1)A large swollen bump or mass2)Pus-filled blisters that break open and crust over3)Pain4)Possible scars once the infection clears

1) Staphylococcal infections

2) Diseases : scalded skin syndrome (infant), toxic shock syndrome (adult)

Pathogen : Staphylococcus aureusTransmission : touching, fomite, breastfeeding Pathogenesis : the bacterial toxins travel through the

bloodstream, causing the upper skin layers to separate and peel off

Symptoms :

1)Blisters2)Fever3)Large areas of skin peel or fall away (exfoliation)4)Painful skin5)Redness of the skin, which spreads to cover most of the body6)Skin slips off with gentle pressure, leaving wet red areas

Diagnosis :

1)Physical examination2)Complete blood count (CBC)3)Cultures of the skin, throat, nose and blood

Treatments:

1)Antibiotics - through a vein (intravenously) to help fight the infection.2)Fluids - through a vein to prevent dehydration. Much of the body's fluid is lost through open skin.3)Moisturizing ointment to keep the skin moist. Healing begins about 10 days after treatment.

Streptococcus 1) Gram-positive spherical/ovoid

cocci arranged in long chains2) Non-spore-forming, nonmotile 3) Can form capsules and slime

layers 4) Facultative anaerobes5) Catalase Negative 6) Most parasitic forms are

fastidious and require enriched media

7) Sensitive to drying, heat, and disinfectants

2) Streptococcal infection

1) Diseases : scarlet fever (scarlatina)Pathogen : Streptococcus pyogenesPathogenesis : the bacteria produce erythrogenic toxinsSymptoms :

i) begin with rashes on the neck and face

ii) then the rashes spread to the chest and back before the rest of the body

iii) sore throativ) fever (T > 38.5°C)v) whitish or yellowish coating at tongue and throatvi) vomiting & loss appetite

Gram-negative pathogens

1) Pseudomonas2) Vibrios3) E.coli4) Campylobacters 5) Helicobacter 6) Haemophilus 7) Neisseriae

GRAM-NEGATIVE BACTERIA

Pseudomonas

obligate aerobic – rod shape motile – presence of flagellanormally found in water, soil and moist environment Culture morphology: round form, β-hemolysis, fluorescent greenish colorOxidase and catalase positiveBroad antibiotic resistance

P. aeruginosa1) Opportunistic microorganisms – cause disease

when host defense is low:Disruption of mucus membrane and skinUsage of intravenous or catheters.

2) Can cause nosocomial infection, UTI, meningitis, pulmonary infection, dermatitis, GTI.

P. Aeruginosa enzymesEnzymes FunctionsProtease Cause tissue damage and help

bacteria spreadPhospholipase C Lyses hemoglobinExotoxin A Cause tissue necrosis (disrupt protein

synthesis)Exoenzymes S & T Cytotoxic to host cells

Vibrio sp.

1) Coma shape

2) Non-spore forming

3) Highly motile – single flagella

4) Facultative anaerobes

5) Tolerate alkaline condition

Cholera

1) Acute diarrheal illness caused by infection of intestine with V. cholera

2) Transmitted via oral-focal route

3) Can multiply freely in water

Pathogenesis of V. Cholera

1) Cholera disease begins with ingestion of contaminated water or food with cholera bacteria.

2) The bacteria that survive the acidic conditions of the stomach colonize in the small intestine.

3) The cholera toxin (CT) is responsible for the severe diarrhea characteristic of the disease.

4) If untreated, the disease rapidly result in dehydration and death

a) CT is a proteinaceous enterotoxin

b) Bind to host cells - mediates the formation of cAMP

c) The increase in cAMP levels bring about the secretion of electrolytes (chloride and bicarbonate) from the mucosal cells into the intestinal lumen

d) The change in ion concentrations leads to the secretion of large amounts of water into the lumen, known as diarrhea

e) If not treated, the infection can cause tubular necrosis and renal failure – leads to death

Cholera Toxin (CT)

Cholera Toxin (CT)

Signs and symptoms

Diarrhea Stomach pain Mild fever

Vomiting Dry mucosal membrane

E. coli

1) Commonly present in intestine

2) Can cause infections in human and animals

3) Some strains are not pathogenic, but some of them are highly pathogenic

4) Detection of E. coli in water indicates pollution and contamination. Maybe it is caused by water treatment or other problems.

Characteristic of E. coli

1) Facultative anaerobes – non-spore forming

2) Motile – have flagella

3) Non-capsulated

4) Non-fastidious

5) Grow on bile-containing media (MacConkey)

Symptoms of Intestinal Infection Due to E. coli

abdominal cramping sudden, severe watery diarrhea that may

change to bloody stools gas loss of appetite/nausea vomiting (rare) fatigue fever

Campylobacter jejuni

Campylobacters jejuni

1) Gram-negative, very slender, curved rods. 2) Motile, no spore, no capsule. 3) Catalase-positive, but are micro-aerophilic and

optimum growth is achieved in an atmosphere containing 5% oxygen and 10% carbon dioxide.

4) Oxidase-positive. 5) The optimum temperature for growth for the

thermophilic campylobacters is 42°C, and they do not grow at temperatures below 30°C.

Campylobacteriosis

1) caused by bacteria of the genus Campylobacter

2) The illness typically lasts about one week

3) Outbreaks of Campylobacter have most often been associated with unpasteurized dairy products, contaminated water and poultry.

4) The organism is not usually spread from one person to another, but this can happen if has direct contact with the stool of infected person.

Campylobacter Virulence Factors

1) Flagellin - bacteria's motility

2) Produce toxins - LPS (endotoxin) and exotoxin

3) Superoxide dismutase - rid of the reactive oxygen species superoxide which could harm the cell's DNA or membrane factors

4) Siderophores – to take away iron from iron-transport protein

What can be done to prevent Campylobacter 

infection?

Helicobacter pylori

Characteristic of Helicobacter pylori

1) Gram-negative, rod curved

2) Very motile – flagella

3) Microaerophilic

4) Grow at body temperature – 37°C

How is helicobacter pylori transmitted??

1) Cause stomach and duodenal ulcers

Diseases caused by Helicobacter pylori

2) Stomach cancer

Helicobacter pylori pathogenicity

Diagram of H. Pylori Infection

Diagnostic of H. Pylori Infection

1) Blood antibody test. A blood test checks to see whether your body has made antibodies to H. pylori bacteria. If you have antibodies to H. pylori in your blood, it means you either are currently infected or have been infected in the past.

2) Urea breath test. A urea breath test checks to see if you have H. pylori bacteria in your stomach. This test can show if you have an H. pylori infection. It can also be used to see if treatment has worked to get rid of H. pylori.

Diagnostic of H. Pylori Infection

3) Stool antigen test. A stool antigen test checks to see if substances that trigger the immune system to fight an H. pylori infection (H. pylori antigens) are present in your feces (stool). Stool antigen testing may be done to help support a diagnosis of H. pylori infection or to find out whether treatment for an H. pylori infection has been successful.

Diagnostic of H. Pylori Infection

4) Stomach biopsy. A small sample (biopsy) is taken from the lining of your stomach and small intestine during an endoscopy.

Diagnostic of H. Pylori Infection

Mycobacteria

• Name from Myco and Bacteria, Fungus like bacteria

• Because it forms mould like growth on liquid cultures

• Types:1) M. Tuberculosis – TB2) M. Leprae – Leprosy

Mycobacteria

Mycobacterium tuberculosis

• Cannot be stained with gram-staining• Acid fast bacteria• They have mycolic acid in their cell wall

which makes them acid fast• Difficult to decolorise with organic acids

Acid Fast Bacteria

Obligate aerobes

Grow slowly – generation time 15 hours

Colonies appear in two weeks

Optimum temperature is 37 deg

Solid media most commonly used – LJ media

Mycobacterium tuberculosis

Pathogenicity and virulence

• Its pathogenicity is due to complex lipids like mycolic acid in cell wall. This makes it– Acid fast– Resistant to antibiotics– Resistant to disinfectants like acid and alkali– Resistant to immune system– Resistant to destruction by macrophages

Tuberculosis

Common symptoms include:1)coughing that lasts longer than 2 weeks with green, yellow, or bloody sputum2)weight loss3)fatigue4)fever5)night sweats6)chills7)chest pain8)shortness of breath9)loss of appetite

Lab diagnosis for M. tuberculosis

• Sample – sputum for pulmonary, biopsy for extrapulmonary sites

• Stain – Ziehl-Neelsen stain• Culture – Lowenstein-Jensen media• PCR – polymerase chain reaction

1) Causes leprosy - has a long incubation period

2) gram-positive - Slightly curved rods

3) Singly or in groups

4)  thick waxy coating

5) affects the skin, the peripheral nerves, mucosa of the upper respiratory tract and also the eyes

Mycobacterium leprae

What Are the Symptoms of Leprosy?

1) Infect the skin and the nerves outside the brain and spinal cord

2) It may also strike the eyes and the thin tissue lining the inside of the nose.

3) Symptoms: disfiguring skin sores, lumps, or bumps, loss of feeling in the arms and legs, Muscle weakness

Leprosy Complications

1) glaucoma.2) Disfiguration of the face (including permanent

swelling, bumps, and lumps).3) Kidney failure.4) Muscle weakness.5) Permanent damage to the inside of the nose, 6) Permanent damage to the nerves outside the brain

and spinal cord, including those in the arms, legs, and feet.

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