Sharq Elneil CollegeSchool of Medical Laboratory Sciences Department of MicrobiologyMedical Bacteriology coursePseudomonas sppU.Mahadi Hassan Mahmoud firstname.lastname@example.org Bsc, Msc, MIBMS Microbiology
Pseudomonas1882 Carle Gessard, a chemist andbacteriologist from Paris, France,
General characters: Not member of enterobacteriaceae. It is similar to them in diseases, saprophytes and commensal in the intestine of human. Oxidase positive. Obligate aerobe. Does not ferment glucose. Large group of microorganisms, more than 200 spp, most of them are saprophytes. The most important species according to infection is P. aeruginosa.
Culture characters: Non-fastidious. Aerobic organism. Blood agar: Large irregular colonies surround by zone of β-haemolysis. MacConkey agar: Pale yellow colonies (NLF), Large irregular colonies. CLED: Green-blue colonies (NLF), large and irregular. Nutrient agar: Produced pigmented colonies.
Culture characters: Different type of pigment: Pyocynin: blue-green, water soluble and need peptone water as substrate. Pyoverdin: yellow-green, fluorescence (UV) and need phosphate as substrate. pyorubin (red) Pyomelanin: brown, need 1% tyrosine in media. Musty smell (grape like smell due to aminoacetophenone).
Viability: It can grow & life in water with small nutrient. Highly resistant to antimicrobial agents, but sensitive to the group of aminoglycosides (e.g.: Gentamicin, tobramycin).
Biochemical reaction: One of the inert microorganism. Cannot ferment glucose, but attack it by oxidation. Oxidase test: +ve. Citrate utilization test: +ve. Motility test: +ve. Indole test: -ve.
Oxidase test Principle: Certain organism produce oxidase enzyme that oxidize oxidase reagents to give purple colour. Methods: Filter paper method: Test requirements: Freshly prepared 1% Oxidase reagent (tetramethyl-p- phenylene diamine). Filter paper. Wood stick or glass rods. Take a colonies and put it in filter paper, add drop of oxidase reagents and examined for purple colour. Oxidase +ve like Neisseria and Pseudomonas.
Oxidation Fermentation Principle: The test depends on fermentation of carbohydrate on anaerobic condition of oxidation of it in aerobic condition. Media content: 2 media each contain nutrition, sugar and bromothymol blue. One of them closed from air by paraffin oil. Results: Oxidative ferment sugar on open tube (Yellow colour). Fermentative but anaerobically give yellow on closed tube. Facultative anaerobic ferment CHO on both tube (Yellow). Non oxidative- Non fermentative– give Blue colour on both tube.
Results There are three types of reactions possible Reaction 1 Reaction 2 Reaction 3 Non-Saccharolytic O-/F Oxidative O+/F- Fermentative O+/F+ Alcaligenes faecalis Pseudomonas EnterobacteriaceaeOpen & covered remain green Open turns yellow Both turn yellow
Biochemical reaction: Urease test: -ve. H2S production test: -ve. MR / VP test: -ve. KIA: Butt Slant H 2S Gas Alkaline Alkaline - - O F test: Open tube Sealed tube Y G
Pathogenicity: Pulmonary Infections Burn Wound Infections and other skin and soft tissue infections (life threatening) UTI’s (especially catheterized) External Otitis (malignant OE, swimmer’s ear) Eye Infections and corneal ulceration via contaminated contact lens cleaning fluids Pseudomonal Endocarditis
Pulmonary Infections Can range from asymptomatic colonization to severe necrotizing bronchopneumonia Colonization is seen in patients with cystic fibrosis, chronic lung disease, and neutropenia Mucoid strains are commonly isolated from chronic pulmonary patients and are more difficult to eradicate Predisposing conditions include previous therapy with broad spectrum abx
Ecthyma Gangrenosum Ecthyma gangrenosum is a well recognized cutaneous manifestation of severe, invasive infection by Pseudomonas aeruginosa that is usually seen in immunocompromised, burn patients, and other critically ill patients
LAB- Diagnosis: Specimen: according to the side of infection ( swabs, blood, urine, sputum……etc). Direct Gram stain (same specimen). Culture & incubation. Colonial morphology. Indirect Gram stain. Biochemical reaction.
Antimicrobial Susceptibility testing Sensetive to:aminoglycosides (e.g.: Gentamicin, tobramycin Inherently resistant to many abx Can mutate to more resistant strains during therapy Combination of active abx generally required for successful therapy
Mechanisms of Antibiotic Resistancein Pseudomonas aeruginosa