pseudomonas basics

7/31/2019 Pseudomonas Basics

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DR.T.V.RAO MD 1

Dr.T.V.Rao MDPSEUDOMONAS


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PSEUDOMONAS

DR.T.V.RAO MD 2

A large group of aerobic, non sporing gram

negative bacteria motile by polar flagella

Found I nature water, soil, other moistenvironments

Some of them are pathogenic to plants

Creation of new genera such as

Burkholderia. Stenotrophomnonas


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- Widely distributed in

soil and water

- Gram negative rods

- Aerobic

- Motile

- Produce water-solublepigments

Opportunistic

pathogens

GENERAL CHARACTERISTICS

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MORPHOLOGY

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They are slender gram negative bacillus, 1.5 3 microbes x 0.5

microns

Monoflgellar ?

Non capsulated but many strains have mucoid slime layer

Isolates from Cystic fibrosis patients have abundance of

extracellular polysaccharides composed of alginate polymers

Escape the defence mechanisms by loose capsule in which

micro colonies of bacillus are enmeshed and protected from

host defences.


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P. aeruginosa

Forms round colonies with afluorescent greenish color, sweet

odor, and b-hemolysis.

Pyocyanin- nonfluorescentbluish pigment;

pyoverdin- fluorescentgreenish pigment;

pyorubin, andpyomelanin

Some strains have a prominentcapsule (alginate).

Identification of P. aeruginosais usually based on oxidase test

and its colonial morphology: b-hemolysis, the presence of

characteristic pigments and sweet odor, and growth at 42 oC.


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CULTURAL CHARACTERS

DR.T.V.RAO MD 6

Obligate aerobe, but grow anaerobically if nitrate is

available

Growth occurs at wide range of temperatures 6-42 c

the optimum being 37 c

Growth on ordinary media producing large opaque

irregular colonies with distinctive musty mawkish or

earthy smell. Iridescent patches with metallic sheen are seen in

cultures on nutrient agar.

In broth forms dense turbidity with surface pellicle.


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Motile (by single or multiple polar flagella)

gram-negative rodsObligate (strict) aerobes (most strains)Oxidase (usually) and catalase positive

Nonfermentative chemoheterotrophicrespiratory metabolismMinimal nutritional reqts.; Many organic

compounds used as C and N sources, but

only a few carbohydrates by oxidativemetabolism Glucose used oxidatively

Lactose negativeon MacConkeys agar

Characteristics of Pseudomonas aeruginosa

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PIGMENT PRODUCTION

DR.T.V.RAO MD 8

Some strains produce diffusible pigments:

Pyocyanin (blue); fluorescein (yellow);

pyorubin (red)

P. aeruginosa produces characteristic

grape-like odor and blue-green pus &

colonies

Broad antibiotic resistance


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BIOCHEMICAL REACTIONS

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Oxidative and Non fermentative

Glucose is utilized oxidatively

Indole, MR and VP and H2 S tests are

negative

Catalase, Oxidase, and Arginine testsare positive


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TYPING AND IMPORTANCE

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Important cause of Hospital Infections

Important for epidemiological purpose

Serotyping Bacteriocins typing

Pyocyanin

Aeruginosin typing

Restriction endonuclease typing with pulsed gel

electrophoresis


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RESISTANCE

DR.T.V.RAO MD 11

Killed at 55oc in on 1 hour

High resistance to chemical agents

Resistance to quaternary ammoniumcompounds.Chlorxylenol

Resistant to Hexchlorophenes

Grows also in antiseptic bottles Dettol as cetrimide as selective medium

Sensitive to acids silver salts, beta glutaraldehyde


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WHAT ANTIBIOTICS TO USE

DR.T.V.RAO MD 12

Aminoglycosides

Gentamycin, Amikacin, Cephalosporins

Cefotaxime. Ceftazidime. Ofloxacin,

Piperacillin, ticarcillin

Local application, colistin, polymyxin


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PATHOGENICITY

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Blue pus

Causing the nosocomial infection

Suppurative otitis Localised and generalised infections

Urinary tract infection after catheterization

Iatrogenic meningitis

Post tracheostomy pulmonary infections


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P. aeruginosaPathogenesis and Immunity

This organism is widely distributed in nature

and is commonly present in moist environments

in hospitals. It is pathogenic only when

introduced into areas devoid of normaldefenses, e.g.,

1. Disruption of mucous membrane and skin.

2. Usage of intravenous or urinary catheters.

3. Neutropenia (as in cancer therapy).


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P. aeruginosa

Antigenic structure,enzymes, and toxins

Pili and nonpilus adhesins.

Capsule (alginate, glycocalyx):

seen in cultures from patientswith cystic fibrosis.

LPS- endotoxin, multiple

immunotypes.

Pyocyanin: catalyzes

production of toxic forms ofoxygen that cause tissue

damage. It also induces IL-8

production. Pyoverdin: a

siderophore.

ProteasesSerine protease,

metalloprotease andalkaline

proteasecause tissue

damage and help bacteriaspread.

Phospholipase C: a hemolysin

Exotoxin A: causes tissue

necrosis and is lethal for animals(disrupts protein synthesis);

immunosuppressive.

Exoenzyme S and T: cytotoxic to

host cells.

Pathogenesis


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PATHOGENESIS AND IMMUNITY

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P. aeruginosacan infect almost anyexternal site or organ.

P. aeruginosais invasive and toxigenic. It

attaches to and colonizes the mucous membraneor skin, invade locally, and produces systemicdiseases and septicemia.

P. aeruginosais resistant to many antibiotics. It

becomes dominant when more susceptiblebacteria of the normal flora are suppressed.


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Septicaemia

Endocarditis

Ecthyma gangrenous

Infantile diarrhoea

Shanghai fever

Disabling eye infections

Survive with minimalnutrients

CLINICAL PRESENTATIONS

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WHO IS MORE SUSCEPTIBLE TO

INFECTION

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This bacterium is of particular concern to

individuals with cystic fibrosis who are highly

susceptible to pseudomonas lung infections.

Pseudomonas aeruginosa is also of graveconcern to cancer and burn patients as well as

those people who are immunocompromised. The

case fatality rate for individuals infected withPseudomonas aeruginosa approaches 50

percent.


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Pseudomonas aeruginosa

is the most frequently

encountered lung pathogen

in patients with cystic

fibrosis (CF). Followinginitial, often intermittent,

episodes of infection, it

becomes a permanently

established component ofthe chronically infected

lung in more than 80% of

patients and confers an

adverse prognosis

PSEUDOMONAS AND CYSTIC FIBROSIS

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Respirators

Endotracheal

tubes Can be Infected

All equipment'sto be sterilized

INFECTION OF EQUIPMENT'S

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PSEUDOMONAS AND URINARY TRACT

INFECTIONS

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Pseudomonal UTIs are usually hospital-acquired

and are associated with catheterization,

instrumentation, and surgery. These infections

can involve the urinary tract through anascending infection or through bacteriuic spread.

In addition, these infections are a frequent

source of bacteraemia. No specificcharacteristics distinguish this type of infection

from other forms of UTI.


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Toxic extracellular products

in culture filtrates

Exotoxin A and S

Exotoxin A acts as NADaseresembling Diphtheria toxin

Proteases,elastatese

hemolysins and enterotoxin

Slime layer and Biofilms

TOXINS AND ENZYMES IN

PSEUDOMONAS

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PSEUDOMONAS AERUGINOSA AN

IMPORTANT OPPORTUNISTIC PATHOGEN

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Pseudomonas aeruginosa is an opportunistic

pathogen, meaning that it exploits some break in

the host defences to initiate an infection. In fact,

Pseudomonas aeruginosa is the epitome of anopportunistic pathogen of humans. The

bacterium almost never infects uncompromised

tissues, yet there is hardly any tissue that itcannot infect if the tissue defences are

compromised in some manner


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P.AEROGINOSA IS AN OPPORTUNISTIC

PATHOGEN

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P,aeroginosa is an opportunistic pathogen. It

rarely causes disease in healthy persons. In

most cases of infection, the integrity of a

physical barrier to infection (eg, skin, mucousmembrane) is lost or an underlying immune

deficiency (eg, neutropenia,

immunosuppression) is present. Adding to itspathogenicity, this bacterium has minimal

nutritional requirements and can tolerate a wide

variety of physical conditions


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PSEUDOMONAS PROMINENT HOSPITAL

ACQUIRED INFECTIONS

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It causes urinary tract infections,

respiratory system infections, dermatitis,

soft tissue infections, bacteraemia, boneand joint infections, gastrointestinal

infections and a variety of systemic

infections, particularly in patients withsevere burns and in cancer and AIDS

patients who are immunosuppressed.


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DIAGNOSIS OF P.AEROGINOSA

INFECTION

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Diagnosis ofP,aeroginosa infection depends upon

isolation and laboratory identification of the bacterium.

It grows well on most laboratory media and commonly

is isolated on blood agar or eosin-methylthionine blueagar. It is identified on the basis of its Gram

morphology, inability to ferment lactose, a positive

oxidase reaction, its fruity odour, and its ability to grow

at 42C. Fluorescence under ultraviolet light is helpfulin early identification ofP.s aeruginosa colonies.

Fluorescence is also used to suggest the presence of

P. aeruginosa in wounds.


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Pseudomonas sp. develop as easilydistinguishable blue-green coloured

colonies, clearly visible under normal

lighting conditions. Other bacterial

species are inhibited or give

colourless colonies. Pseudomonasaeruginosa, Pseudomonas

fluorescens, Pseudomonas putida

and Pseudomonas fragilis all give

typical blue-green colony colouration

and can be studied directly byserotyping or biochemical methods.

IDENTIFICATION WITH CHROMAGAR

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LABORATORY IDENTIFICATION OF

DIAGNOSIS OF P.AEROGINOSA INFECTIONS

DR.T.V.RAO MD 28

Diagnosis of P. aeruginosa infection depends upon

isolation and laboratory identification of the bacterium.

It grows well on most laboratory media and commonly

is isolated on blood agar or eosin-methylthionine blueagar. It is identified on the basis of its Gram

morphology, inability to ferment lactose, a positive

oxidase reaction, its fruity odour, and its ability to grow

at 42 C. Fluorescence under ultraviolet light is helpfulin early identification of P. aeruginosa colonies and may

also help identify its presence in wounds.


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TREATING PSEUDOMONAS INFECTIONS

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Combined antibiotic therapy is generally

required to avoid resistance that develops

rapidly when single drugs are employed.Avoid using inappropriate broad-spectrum

antibiotics, which can suppress the normal

flora and permit overgrowth of resistantpseudomonads.


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PSEUDOMONAS AERUGINOSA A RESISTANT

PATHOGEN

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Pseudomonas aeruginosa is frequently resistant

to many commonly used antibiotics. Although

many strains are susceptible to gentamicin,

tobramycin, colistin, and amikacin, resistantforms have developed. The combination of

gentamicin and carbenicillin is frequently used

to treat severe Pseudomonas infections. Severaltypes of vaccines are being tested, but none is

currently available for general use.


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P. aeruginosa

Prevention and Control

Pseudomonasspp. normally inhabit soil, water, and vegetation

and can be isolated from the skin, throat, and stool of healthy

persons.

Spread is mainly via contaminated sterile equipment's andcross-contamination of patients by medical personnel.

High risk population: patients receiving broad-spectrum

antibiotics, with leukemia, burns, cystic fibrosis, andimmunosuppression.

Methods for control of infection are similar to those for other

nosocomial pathogens. Special attention should be paid to sinks,

water baths, showers, hot tubs, and other wet areas.


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DR.T.V.RAO MD 32

Programme created by Dr.T.V.Rao MD

for Medical and Paramedical Students

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pseudomonas basics

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