Ayham Omar Mohammad Malas - HUMSC · Ayham Omar 10 . SCIENTIFIC TEAM – يملعلا قيرفلا 1 الله الرحمن الرحيم

Mohammad Malas

Ayham Omar

10

SCIENTIFIC TEAM 1 –الفريق العلمي

بسم الله الرحمن الرحيم

Pseudomonas Aeruginosa

Very successful hospital pathogen (very important in hospital

environments), because:

It infects immunocompromized patient.

It shows resistance to most antibiotics.

Usually causes hard to treat nosocomial infections (hospital

infections).

Pseudomonas Aeruginosa

Lecture 10

Date : 15/Nov./2020

كلام الدكتور: الأسود

السلايد: الأزرق

شرح أو توضيح خارجي: الأخضر


People at risk include:

Hospitalized patients

Immuno-compromised persons can cause very severe life

threatening infection.

Healthy individuals mild infection.

CF patients can cause severe chronic infection in CF patients

like, pneumonia and chest infection.

- CF patients: cystic fibrosis patients (مرضى التليف الكيسي) .

Ecological factors (which make Pa so successful):

Pa is primary a nosocomial pathogen.

It is ubiquitous water and soil organism.

Survive well in domestic environments like contact lenses and

solutions, and in hospital (food, cut flowers, sinks, toilets, floor

mops, respiratory therapy (respirator) and dialysis equip, and

even in some disinfectant solutions)

Rarely it can be a part of normal flora in healthy individuals

Importance of prevention:

How the ecological factors are important in risk prevention?

- If we know where we can find Pa (by knowing the ecological

factors) we can prevent patients from infection.

لأنه في عليها كثير من هذه البكتيريا، مثلً يعني بنمنع وجود الورود والخضار في وحدة الحروق -

.واذا وصلت للمريض رح تسببله عدوى شديدة


Pa is found almost everywhere in hospital, it is even found in

disinfectant (الي بيستخدموه للتعقيم) .

Pa is able to survive and proliferate in water with minimal nutrient

like respirator, contact lenses

.(eye infectionوممكن يسبب السائل الي بنحفظ فيه العدسات اللصقة)

Bacteriology

Bacteria.

Gram negative and gram positive.

Gram negative: Cocci, rods, acid-fast.

Gram negative rod: facultative, anaerobes, aerobics.

Pa is obligate aerobic gram negative rod (oxidation).

- It drives its energy from sugars by oxidation (unlike other

enterobacter).

Pa in non-fermenter (has a lot of cytochrome oxidase C).

Pa classification: non fermenting, oxidase positive, gram

negative rods.

Pa has a polar flagella and pilli that make Pa mobile.

positive oxidase test


Production of colorful water-soluble pigments:

Pyocyanin Pyoverdin (fluorescence)

Fluorescence: this characteristic can be used in early detection of

skin infection in burn patient (blue, yellow, green or red pigments)

بلون pigmentationبنلقي burn infection in the skinل يعني لما نتطلع على ا -

Paأزرق أو أصفر وهذا بيدلني على احتمالية وجود ال

Pyocyanin (blue) + Pyoverdin (yellow) = bright green color of

fluorescence

Also we can identify it from other gram negative bacteria

(Characteristic metallic sheen).

Intense fruity odor like the smell of crapes


Pa lives in slime enclosed biofilm.

The biofilm protects Pa from antibiotics and phagocytes, this biofilm

allows Pa to survive in this biofilom and replicate in this biofilm and

cause chronic infection CF patients.

Pa lives inside respiratory system, especially in CF patients as slime

enclosed biofilm.

بتكون على شكلcommunity وبتحميها طبقة من ال مغلفة مع بعضها البعضslime or

mucous وبالتالي هذه التجمعات أو ال ،biofilm بيحميها من الantibiotics.

General characteristics:

1. Obligate aerobic, gram negative bacilli non-sporing,

non-capsulate

2. Non-lactose fermenter

3. Oxidase positive

4. Glucose oxidizer

5. Catalase positive

6. Citrate positive

7. Motile by a polar flagella

8. It produces pigments

a) pyocyanin = blue green pigment (only in PA)

b) pyoveridin = yellow-fluorescence (PA & other bacteria)

c) pyorubin= red


Pathogenesis:

Opportunistic pathogen because it has a weak invasive ability.

In healthy individual it doesn’t cause a severe infection.

It takes any reduce of immune system opportunity.

Requires break of first-line defenses (wound or contaminated

solution).

Burn patient: the skin defense is lost so Pa will take this

opportunity and cause infection in burn area.

CF patient is immunocompromized, this patient has an

impairment in the respiratory tract (thick mucous), Pa will take

this opportunity and cause infection, and it will produce a

biofilm and cause chronic infection.

Virulent factors:

Endotoxin, exotoxin, enzymes, flagella, billi, biofilm, biocyanin,

type 3 section system

Endotoxin (lipid A): sepsis and endotoxin shock


Exotoxin A

Causes tissue necrosis

Consists of 2 portions; A-B toxin, and

produced by Pa.

Portion B binds to a receptor on the

cell membrane, A & B units become

internalized into the cell by

endocytosis and surrounded by a

vesicle.

A & B portions are separated

because of the acidity, portion B exits the cell by exocytosis,

while portion A enters cytoplasm and stops translation (stops

protein synthesis)

Stopping translation:

mRNA passes through the ribosome

The addition of amino acids to the polypeptide chain is called

elongation.

Elongation is facilitated by a factor called elongating factor, one

of them is called elongating factor 2 (EF2).

Exotoxin A inactivates the EF2,

Once the elongation stops, protein synthesis stops cell dies.

This means that there is a necrosis.

Similar in structure to Diptheriatoxin

Causes Dermatonecrosisin burn wounds, corneal damage in ocular

infections, and tissue damage and nexcrosisin chronic pulmonary

infections


Portion B (binding portion): binds to the receptor

Portion A (active portion): activates the EF2 and stops protein

synthesis.

Exo S, T, Y and U

Cause epithelial cell damage, facilitating bacterial spread, tissue

invasion, and necrosis.

Enzymes

Elastase, phospholipase C and protease are produced by Pa.

Histotoxic

Cause destruction and disruption of the body tissue

Facilitate the organism to reach blood stream

Eleastase:

Destruction of elastin-containing tissues (blood vessels,

lung tissue, skin), collagen, immunoglobulins (IgA and

IgG), and complement factors

Can produce hemorrhagic lesions (ecthymagangrenosum)

associated with disseminated infection

Elastase facilitates the organism to reach blood stream

and when get to the blood stream cause bacteremia and

sepsis.

Phospholipase C

Breaks down lipids and lecithin causing tissue destruction


T3SS (Type 3 secretion system)

Some strains of pa have this system.

Strains that have T3SS more violent than other strains that

don’t have this system.

They transfer exotoxin from bacteria directly into the adjacent

human cell.

This allows to exotoxin to avoid the antibodies.


Flagella and Pilli

Makes the Pa mobile

Pulmonary infection

Pilli facilitate the adhesion of pa to epithelial cell

Pyocunin can damage cilia and mucosal cells and immune cell in

respiratory tract

1. Can mediate tissue damage

2. It also stimulates IL-8 release, leading to enhanced attraction

of neutrophils

Considered a virulent factor.

Mediates tissue damage through production of oxygen radicals.

Alginate–mucoid exopolysaccharide that forms a shiny biofilm

protecting from antibodies, complement, phagocytosis, and

antibiotics.

Also considered a virulent factor.


Gram stain and culture

Gram stain can't differentiate Pa from other gram negative

rods.

Specimen obtained as indicated of type of infection

Gram stain: gram negative, rod that is motile and encapsulated

Electron microscope: polar flagella it has pili

Gram negative Motile encapsulated rod with polar flagella

Ps. aeruginosa is indistinguishable from other gram negative

bacilli. Therefore there is a little significance for gram staining.

Culture: far the most important and specific test for diagnose pa

infection

Grow well on ordinary media such as Blood Agar, Nutrient

Agar and MacConkey Agar.

Pa does not ferment lactose

Pa grows in non lactose fermenting colony in macConkey

agar (very characteristic for Pa).


Blood agar: -Metallic sheen -Many are haemolytic

MacConkey agar: -Colourless,non lactose fermenters Pa colorless Ecoli pink

Cetrimide agar: -selective media

بنلحظ هون الpositive oxidase testبناخد ال ،oxidase reagent وبنضعه على ،

.oxidase positive، وهذا معناه انه purple، بتصير colonyال

Biochemical reactions

Oxidative/fermentation glucose test-oxidative

Catalase-positive

Oxidase-positive

Nitrate reduction-positive

Citrate test-positive


Sugar fermentation tests

Glucose-only acid

Lactose-negative

Sucrose-negative

Mannitol-negative

These tests differentiate Pa from other oxidase negative gram

negative rods.

Pa non lactose fermenting oxidase positive gram negative rod.

Ps produce diffusible greenish

pigment which is a combination of

pyoveridin and pyocyanin.

Mucoid appearance of pa due to over production of alginate,

Alginate is an exopolysaccharide that provide the matrix for pa to

live in this biofilm


Summery the culture feature of Pa

Non lactose ferment oxidase positive

Green, blue

Metallic sheen

Mucoid appearance

Fruit smell

These feature are sufficient to diagnosis pa and confirmation by

biochemical test

Clinical Presentation

Pulmonary infections, common in cystic fibrosis patients

Primary skin infections: Opportunistic infections of existing

wounds (e.g., burns) to localized infections of hair follicles

UTI infections: Opportunistic infections in patients with indwelling

urinary catheters

Ear infections: range from mild irritation of external ear

"swimmer's ear“ to invasive destruction of cranial bones

Eye infections: Opportunistic infections of exposed, mildly

damaged corneas e.g., contact lens wearer

Bacteremia: Dissemination of bacteria from primary infection to

other organs and tissues


Ecthyma gangrenosum is a well recognized cutaneous

manifestation of severe, invasive infection by Pseudomonas

aeruginosathat is usually seen in immunocompromised, burn

patients, and other critically ill patients

Black necrotic ulcer,

often no pus

Burn

Bluish greenish discoloration

Tissue necrosis

Grape like smell

Tt: debridement and anti-

psudomnase


Malignant Otitis Externa

Diabetic and HIV pts

No fever

No leukocytosis.

Otologiand headache

tt: oral cipro

In 24-48 hrs


Healthy individuals may be infected by Pa and cause mild infection.

Most common to cause folliculitis (hair follical) that happens happy

when path water is contaminated with Pa.

Prevention

Observe proper hand hygiene (specially hands with finger ring).

Proper education of hospital related personnel on hand hygiene

Good housekeeping limit the chance of transmission of pa

Do not bring fruit ad row vegetable in burn unit

Use sterile water for washing medical equipment and devices

and do not use tape water

Limit use of broad spectrum ab disturb normal Flore, give pa an

opportunity infect

Place all CF patent in private room that should not share

bathroom or shower

Avoid direct contact


Treatment

Inherently resistant to many antibiotics (penicillin, ampicillin,

tetracycline, earlier aminoglycosides and sulfonamides).

Can mutate to more resistant strains during therapy.

Production of B-lactamases.

Combination of active antibiotics generally required for successful

therapy (Anti-β-lactam and aminoglycoside).

There are some strains of Pa that are even resistant to anti-pa

antibiotics.

Anti-Pa antibiotics:

Extended spectrum penicillin (ticarcillin piperacillin)

- not used alone used, usually combined with aminoglycoside.

Cabapenem (imipenem)

- very broad spectrum is because it is stable and the molecular

structure for it is very small so it can cross the cell wall of Pa (very

effective in treating Pa).

Aminoglycoside gentmtimicin amikacin tobramycin

Cephalosporin3rd 4th the 3rd: ceftazidime, 4th cefipime

fluoroquinolone (ciprofloxacin) good choice as a oral anti-Pa.

Monobactam

Polymyxin B

inhaled topramcine (for respiratory infection).

Vaccine experimental (ما في لقاح لحد الآن)

..بالتوفيق

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Ayham Omar Mohammad Malas - HUMSC · Ayham Omar 10 . SCIENTIFIC TEAM – يملعلا قيرفلا 1 الله الرحمن الرحيم