Family PseudomonaceaeGenus PseudomonasePseudomonads and Acinetobacters are widely distributed in soil and water

Objective

•To be familiar with Pseudomonas species •To describe the characteristic•To understand the pathogenesis•To explain the diseases , Clinical finding,

diagnosis , treatment and prevention

Pseudomonase

•Gram-negative• motile• aerobic rods •some of which produce water-soluble

pigments •The classification is based on rRNA/DNA

homology and common culture characteristics.

P aeruginosa

• Widely distributed in nature, commonly in moist environments in hospitals.

• Colonize normal humans• Causes disease in humans with abnormal

host defenses.

Pseudomonas aeruginosa

•Gram-negative bacteria•Small numbers in the normal intestinal

flora and on the skin of humans .•The major human pathogen of the group. • invasive • Toxigenic• Important nosocomial pathogen.

Pathogenesis

•Pathogenic only when introduced into areas devoid of normal defenses,

•Mucous membranes and skin are disrupted by direct tissue damage;

•Intravenous or urinary catheters are used;

• Neutropenia is present, as in cancer chemotherapy.

•The bacterium attaches to and colonizes the mucous membranes or skin, invades locally, and produces systemic disease.

Clinical Findings• Infection of wounds and burns, • Meningitis, • Urinary tract infection, catheters ,

instruments or in irrigating solutions. • Respiratory tract, contaminated respirators,

results in necrotizing pneumonia. • Mild otitis externa in swimmers. ,invasive

(malignant) otitis externa in diabetic patients. • Eye infection , lead to rapid destruction of the

eye, most commonly after injury or surgical procedures.

• In infants or debilitated persons, invade the bloodstream and result in fatal sepsis; in leukemia, lymphom, antineoplastic drugs, radiation therapy, patients with severe burns.

Symptoms & Signs• Related to the organ . • verdoglobin (a breakdown product of

hemoglobin) or fluorescent pigment can be detected in wounds, burns, or urine by ultraviolet fluorescence.

• Hemorrhagic necrosis of skin occurs often in sepsis due to P aeruginosa;

• the lesions, ecthyma gangrenosum, are surrounded by erythema and often do not contain pus. P aeruginosa can be seen on Gram-stained specimens from ecthyma lesions, and cultures are positive.

Sign and Symptoms

•Fever,•Shock, •Oliguria,•Leukocytosis and leukopenia,• Disseminated intravascular coagulation,•Adult respiratory distress syndrome.

Antigenic Structure & Toxins• Pili (fimbriae) attachment to host epithelial

cells. • Alginate exopolysaccharide mucoid colonies

seen in cultures from patients with cystic fibrosis.

• Endotoxin, ▫P. aeruginosa can be typed by lipopolysaccharide

immunotype and by pyocin (bacteriocin) susceptibility.

• extracellular enzymes : ▫Elastases, proteases, and two hemolysins: a heat-

labile phospholipase C and a heat-stable glycolipid.

Exotoxin•Exotoxin A,

tissue necrosis , lethal for animals when injected in purified form.

The toxin blocks protein synthesis mechanism of action identical to

diphtheria toxin, though the structures of the two toxins are not identical.

Antitoxins to exotoxin A are found in some human sera, including those of patients who have recovered from serious P aeruginosa infections

Morphology & Identification

•Motile •Rod-shaped• Gram-negative (single, pairs, and

occasionally in short chains)

Culture

• Obligate aerobe• Grows on many types of culture media,• Sweet or grape-like or corn taco-like odor. • Some strains hemolyze blood.• Smooth round colonies with a fluorescent

greenish color : • pyocyanin: Nonfluorescent bluish pigment• Pyoverdin: fluorescent pigment, greenish

color• Pyorubin: dark red pigment • pyomelanin : black pigment

Diagnostic Laboratory Tests

•Specimens•Specimens from skin lesions, pus, urine,

blood, spinal fluid, sputum, and other material should be obtained as indicated by the type of infection.

•Smears•Gram-negative rods•Biochemical tests ; Oxidase , growth at

42 °C, •Pigments , oxidize glucose

•P aeruginosa and other pseudomonads are resistant to many antimicrobial agents and therefore become dominant and important when more susceptible bacteria of the normal flora are suppressed

Treatment• Rapidly develop resistance when single drugs

are employed. So,Clinically significant infections with P aeruginosa should not be treated with single-drug therapy

• Ticarcillin or piperacillin—is used in combination with an aminoglycoside, usually tobramycin

• Aztreonam, imipenem, and the newer quinolones, including ciprofloxacin.

• Newer cephalosporins, ceftazidime and cefoperazone are active against P aeruginosa

Epidemiology and Control

• Nosocomial pathogen• Special attention should be paid to sinks,

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

• Epidemiologic purposes, strains can be typed by pyocins and by lipopolysaccharide immunotypes. Vaccine from appropriate types administered to high-risk patients provides some protection against pseudomonas sepsis.

• Such treatment has been used experimentally in patients with leukemia, burns, cystic fibrosis, and immunosuppression.

Burkholderia pseudomallei•small, motile, aerobic gram-negative

bacillus•a natural saprophyte ; soil, fresh water,

rice paddies, and vegetable .• Human infection ; contamination of skin

abrasions and possibly by ingestion or inhalation.

• Epizootic B pseudomallei infection occurs in sheep, goats, swine, horses, and other animals, though animals do not appear to be a primary reservoir for the organism.

Melioidosis of humans• Melioidosis may manifest itself as acute,

subacute, or chronic infection.• IP 2–3 days, but latent periods of months to

years also occur.• A localized suppurative infection can occur at

the inoculation site where there is a break in the skin.

• acute septicemic form of infection with involvement of many organs.

• The most common form of melioidosis is pulmonary infection, which may be a primary pneumonitis

• Melioidosis has a high mortality rate if untreated

•Burkholderia mallei :glanders, a disease of horses, mules, and donkeys transmissible to humans

•Burkholderia cepacia:is an environmental organism that is able to grow in water, soil, plants, animals, and decaying vegetable materials

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