pseudomonas aeruginosa - medical bacteriology

Pseudomonas- medical bacteriology

1. PSEUDOMANS

2. VIVEKANANDHA ARTS AND SCIENCE COLLEGE FOR WOMEN VIVEKANANDHA ARTS AND SCIENCE COLLEGE FOR WOMEN VEERACHIPALAYAM, SANKAGIRI, SALEM, TAMILNADU. Affiliated to prayer university by Salem, Recognised under section 2(F),12(B) of the UGC act, 1956. SUBJECT MEDICAL BACTERIOLOGY DEPARTMENT OF MICROBIOLOGY DEPARTMENT OF MICROBIOLOGY Subject incharge: Dr. Mythili Ravichandran, Head of department, Department of microbiology, VIAAS, sankagiri. Summited by; Mr.s.V.Nandhini Vengadachalam, III- BSc., Microbiology, Department of microbiology, VIAAS, sankagiri. TOPIC : PSEUDOMONAS

3. Pseudomonas

4. CONTENTS Introduction Morphology Cultural characteristics Biochemical reaction Epidemiology Virulence factors Pathogenicity Laboratory diagnosis Control Treatment Conclusion

5. Introduction Pseudomonas is a large group of aerobic, non-sparing, Gram-negative bacilli, motile by polar flagella. They are uniquitous, mostly saprophytic, being found in water, soil or other moist environments. Some of them are pathogenic to plants, insects and reptiles. A few cause human infection typically opportunistic. Based on molecular analysis, pseudomonads hare been re- classified and many former pseudomonas species re allocated to new genera Such as Burkholderia, Stenotrophomonas and others.

6. Morphology It is a slender, gram negative bacillus, 1.53x 0.5 m in size, actively motile by a polar flagellum. Clinical isolates are often piliated. It is non-capsulated but many strains have a musoid slime layer. Musoid strains, particularly isolates from cystic fibrosis patients, have an abundance of extracellular polysaccharides composed of alginate polymers (case). This forms a loose capsule (glycocalyx) in which micro colonies of the bacillus are enmashed and Protected from host defences.

7. Cultural characteristics It is an obligate aerobe, growth occurs at a wide range of temperature, 6-42c , the optimum being 37 c. Ordinary media: It grows well producing large, opaque, irregular colonies , with a distinctive musty mawkish or earthy smell. Nutrient agar : Iridescent patches with a metallic sheen are seen in cultures with crystals beneath the patches. Macconkey Medium: It forms non- lactose fermenting colonies. Blood agar: Many strains are hemolytic on blood agar.

8. Broth It forms a dense turbidity with a surface pellicle. Pigment production: p. aeruginosa produces a number of pigments, the best known being pyocyanin and fluorescein. Pyocyanin is a bluish –green phenazine pigment soluble in water and chloroform. Fluorescein (pyoverdin) is a greenish – yellow pigment soluble in water but not in chloroform. Other pigment produced are pyorubin (red) and pyomelanin (brown) in various combinations. Some of the pigments, particularly pyocyanin, inhibit the growth of many other bacteria and may therefore contribute to p. aeruginosa emerging as the dominant bacterium in mixed infections.

9. P. Aeruginosa showing pigment production (pyocyanin)

10. Biochemical reactions The metabolism is oxidative and non fermentative, clinical isolates are oxidase and catalase and arginine dehydrolase tests positive. They do not ferment lactose but many strains oxidise glucose with acid production only. Since acid production by p. aeruginosa is weak and gets neutralised by alkali produced from peptone. An ammonium salt sugar medium (with sugar as only carbon sources) should be used instead of peptone water sugars. All strains utilise citrate indole, MR, VP and H2S tests are negative.

11. Resistance The bacillus is not particularly heat resistant, being killed at 55 c in one hour, but exhibits a high degree of resistance to chemical agents. Indeed p. aeruginosa can grow in dettol Or cetrimide selective medium. It is sensitive to acids, beta glutaraldehyde, silver salts and strong phenolic disinfectants. Its succeptibility to silver has been applied clinically in the use of silver sulphonamide compounds as topical cream in burns. It is resistant to the common antiseptics and disinfectants such as quaternary ammonium compounds, chloroxylenol and hexachlorophene and may even grow profusely in beetles of such antiseptic lotions kept for use in hospitals.

12. Epidemiology Ubiquitous soil, water and air. 3-4℅ non hospitalized patients have skin and GIT opportunistic pathogen. Hospitals-disinfectants, respiratory equipment, food, sinks, taps, toilets, showers and mops. Hospitals gets organisms by fruits, vegetables and visitors. Common cause of hot tup folliculitis. 3 rd most common cause of UTI. Common cause of bactrial keratitis. Predisposing factors: Immune compromised burns, hospital, cancer pts, cystic fibrosis.

13. Virulence factors Several proteases are produced, which can degrade host complement factors, mucins, and disrupt tight junction between epithelial leading to dissemination of the bacteria. Lipases and phospholipases can target lipids in the surfactant as well as host cell membranes. Pyocyanin, a blue- green pigment, can interfere with host cell electrons transport pathways and redox cycling. Pyoverdine captures fe3+ to allow for a competitive edge in an environment in which free iron in scarce.

14. Virulence factors - Table

15. Pathogenicity ‘ Blue pus’ was known as a surgical entitylong before gassard (1882) isolated p.aeruginosa from such cases. The term aeruginosa means verigris, which is bluish –green in colour and pyocyanea is a literal translation of blue pus. Exotoxin A has a mechanism of action similar to that of the diphtheria toxin. Other extracellular enzymes and toxins include protease, elastases, hemolysis and enterotoxin. The slime layer acts as a capsule in enhancing virulence. Factors promotting infections; Breach in primary body defences.

16. Bacterial pili (favour adhesion) Bacterial exoproducts (elastase, exotoxin A, exoenzyme s. Lipopolysaccharides (cell wall) and the alginate glycocalyx. The ability to form biofilms.

17. Pathogenicity - fig ; flow chart

18. Laboratory diagnosis Specimen: sputum, purulent discharge from lesion, aspirated pus, etc,... Direct microscopy: gram-negative bacilli, bio polar Or safety pin appearance . Culture: obligate aerobe. Colonies: rough and cerrugated ashdown‘s medium, where it produces wrinkled purple colonies. Identification: conventional biochemical tests (e.g. Resistance to polymyxin B) or by automated methods-VITEX. MALDI- TOF- not yet validated for identifying B. Pseudo mallei . Latex agglutination test with specific antisera- used to identify them from cultures. Repeated isolation and clinical correlation helps confirm the diagnosis .

19. Control Prevention of p. aeruginosa cross Infection in hospitals requires constant vigilance and strict attention to asepsis. Fig.of . Under microscope observed in p. Seudomans .

20. Treatment P.aeruginosa is commonly resistant to antibiotics. Many strains are susceptible to gentamicin, tobramycin, colistin and amikacin but some resistant forms have developed. Infections are usually treated with two antibiotics at once. The combination of gentamicin and carbeni is frequently used to treat severe –cillin pseudomonas infection. Most antibiotics are administered intravenously Or orally for 2-6 weeks. Eye infection requires local application of antibiotic drops.

21. Conclusion Pseudomonas Strains able to significantly control a number of fungal, bacterial and nematede diseases in cereals, horticultural crops oil seeds and others. However a better understanding of the factors involved, the signalling interaction among antagonist, pathogen, soil and plants are yet to be revealed to promote the biocontrol agents as wide applicable biopesticides in future.

22. Reference Text book of Microbiology Author –chakraborty .