Diagnostic microbiology
lecture: 5
Pseudomonas
Abed ElKader Elottol
MSc. Microbiology
2010
Pathogenic species
1. Pseudomonas aeruginosa
2. Ps. pseudomallei
3. Ps. mallei
Pseudomonas aeruginosa
May grow in :
• Disinfectants
• Contact lens solutions
• Medicinal solutions
• Humidifiers of respirators
GENERAL CHARACTERISTICS
1. Obligate aerobic, gram negative bacilli indistinguishable
from Enterobacteriaceae.
2. Non-lactose fermenter
3. Oxidase positive
4. Glucose oxidizer
5. Catalase positive
6. Citrate positive
7. Motile by a polar flagella
8. Produces exotoxin A = Inhibits protein synthesis and
produces tissue necrosis.
9. Produces collagenase which hydrolysis collagen
10. produces elastase which hydrolysis elastin and is used by
the organism for invasion.
11. It produces pigments
11.1 pyocyanin = blue green pigment
11.2 pyoveridin = Yellow- fluorescence.
PATHOGENICITY
•Ps. aeruginosa is an opportunistic pathogen that infect
immunocompromized patient.
•Usually causes hard to treat nosocomial infections.
• It show resistance to most antibiotics.
DISEASES caused by Ps. aeruginosa include:
1. Urinary tract infection (UTI)
6. Sepsis
2. Otitis media
7. Burn infection
3. Wound infection
8. Meningitis
4. Sinus infection
9. Endocarditis
5. Bronchopneumonia
IDENTIFICATION
1. Gram staining:
Ps. aeruginosa is indistinguishable from other
gram negative bacilli. Therefore there is a little
significance for gram staining.
2.Culture:
Ps. aeruginosa grow well on ordinary media such
as Blood Agar, Nutrient Agar and MacConkey
Agar.
= Colonies are 2-4 mm in diameter, slightly
convex, grayish the smell like grape and are often
hemolytic.
= On Nutrient Agar, Ps. aeruginosa is easily
recognized
by
the
diffused
blue-green
pigmentation.
Biochemical tests
Serological typing: This is performed through an
agglutination test based on the reactivity of somatic O
antigens of intact cell with specific antisera. Cross reactivity
may occur in 10-11% of cases.
Pyocin typing: Pyocin is an antibiotic produced by
Pseudomonas aeruginosa that can inhibit the growth of
other bacterial species. This test is less commonly used.
ANTIBIOTIC SUSCEPTIBILITY
Ps. aeruginosa is typically resistant to commonly used
antibiotics.
= Aminoglycosides (Amikacin, gentamicin), polymyxins and
colistin are used in the treatment of this organism. 3rd & 4th
generation cephalosporins.
= Mg++ and Ca++ must be added to the growth medium
used in the sensitivity testing.
Pseudomonas pseudomallei
Burkholderia pseudomallei
DISEASE: Melioidosis:
Uncommon tropical disease= Pulmonary manifestation
of the disease which is usually confused with
tuberculosis.
Characteristics:
1. Non pyocyanin producer.
2. Esculin hydrolysis = Positive
3. Lactose oxidation = Positive
NB: These characteristics are used to differentiate it
from Ps. aeruginosa.
Pseudomonas mallei
Burkholderia mallei
• DISEASE: Glander:
• Ulcerating, tubercle-like nodules forms in the lungs,
superficial lymph nodes and mucus membrane.
• This organism could be differentiated from other Psudomonas
species by carbohydrate oxidation test.
Acinetobacter
Pathogenic species
Acinetobacter calcoaceticus
DISEASE: It is an oppurtinistic pathogen.
In patients with burns or with immunologic
deficiency, they can produce sepsis or pneumonia.
Diagnostic tests
On gram stained smears it mimic the appearance
of Niesseria and thus sometimes called (mima),
but it is rapidly differentiated from Niesseria by
negative Oxidase test.
1. Non motile
2. Resistant to penicillin
3. Grow well on MacConkey Agar.
Achromobacter
Pathogenic species
Achromobacter xylosoxidans now known as
Alcaligenes denitrificans
DISEASES:
1. Septicemia
2. Otitis media
3. Meningitis
4. Wound infection
5. Urinary tract infection.
Oxidase positive, catalase positive
Motile
non lactose fermenter
CHARACTERISTICS:
1. It grow well on MacConkey Agar
2. Oxidase positive
3. Motile by peritrichous flagella
4. Acidification of Oxidation-Fermentation (OF) glucose and
xylose.
Alcaligenes
Pathogenic species:
1. A. faecalis = recovered from blood, sputum and
urine.
2. A. odorans = recovered from urine
3. A. denitrificans
CHARACTERISTICS:
1. Motile by peritrichous flagella
2. Oxidase positive
3. Hydrolysis urea
4. Citrate positive
5. Inability to utilize OF carbohydrates used
acetate
Discriminating Characteristics of Members of the Genus
Alcaligenes
Treatment
Susceptible to cephalosporins, such as carbenicillin.
Also to minocycline, doxycycline and polymyxin B.