Gram Negative Rods

1. Gram Negative Rods

3. Enterobacteriaceae Family General Characteristics of Enterobacteriaceae: • Morphology: large family of gram-negative bacilli, without special arrangement. • Habitat: they inhabit soil, water, and also a common occupant of large bowel of humans & animals. • Culture: they are facultative anaerobic • Biochemical reaction: • all are Oxidase negative. • They differentiated according to lactose fermentation into lactose fomenters (LF) and non lactose fomenters (NLF). • Non-spore forming • Some are primary pathogen while some are commensals. • Escherichia coli is the most common bacterium in gut, and It’s a very common cause of UTI.

4. Gram-negative rods

5. MacConkey agar with LF and non-LF colonies

7. What is Escherichia coli? • It belongs to the family Enterobacteriaceae. • These organisms inhabit the intestinal tract of most warm blooded animals. • Colonizes newborns GI tract within hours after birth • There are more than 700 different serotypes of E. coli, distinguished by different surface proteins and polysaccharides

8. General Characteristics of E. coli • Morphology:Gram negative, rods, appear in singles or in pairs. • Culture: • facultative anaerobe, grow between 10 – 40 °C (optimal at 37 °C). • On MacConkey medium produce bright pink colonies (Lactose fermenters). • Give a metallic green sheen colonies on EMB. • Biochemical Reactions:Oxidase-Negative, Indole test-Positive. • Motile by flagella- ( Very few strains non motile)

9. E. coli on Mac.

10. E. coli on EMB

11. The Beneficial E. coli • Protects the intestinal tract from bacterial infections • Aids in digestion • Produces our main source of vitamins B12 and K • Lives symbiotically with us (we help them to live, and they help us to live)

12. Bad E. coli • While most E. coli are good for you, there are a few strains of E. coli that are harmful to humans. • It is possible to get an individual strain of E. coli that is harmful to you. • E. coli O157:H7 Most notorious strain of bad E. coli: • Produces a powerful toxin and can cause severe illness • Most dangerous for little kids, the elderly, and the sick • Damages the intestines, causes bloody diarrhea, and other complications • Cause disease by making a toxin called Shiga toxin “Shiga toxin-producing” E. coli - STEC

13. Pseudomonas spp. • Ubiquitous bacteria, grow everywhere (in soil , water, plants, animal tissues, and other places that contain moisture). • Some strain can even grow in distilled water. • Can produce pigment. • Some strains are antibiotic-resistant bacteria. • It is an “Opportunistic Pathogen”.

14. Pseudomonas spp. • Pseudomonas aeruginosais the primary human pathogen in the genus Pseudomonas. • It’s found any wear in the environment. • Common cause of nosocomial infections. • In normal host it cause opportunistic infection. • Immunodeficiency, breaching of first line of defense, and the use of medical devices predispose the patients to P. aeruginosainfections

15. Characteristics of P. aeruginosa. • Morphology: Gram negative rods. • Culture: • Obligate aerobes (most strains). • Nutritional requirements are minimal, it can grow on a wide variety of organic substrates, like: laboratory water baths, hot tubs, wet IV tubing, other water containing vessels (that’s way the organism is responsible for many nosocomial infections).

16. Grow at wide range of temperatures 6-42°C • Produce yellow-green pigmentation • Produce large irregular colonies with distinctive smell (grape-like odor). • Biochemical Reactions: Oxidase positive. • Motile (by single or multiple polar flagella). • Non-spore forming • Non-capsulated but many strains have mucoid slime layer. • Resistant to a large range of antibiotics.

19. P. aeruginosa Virulence Factors • Pili: Most of the clinical isolates have pili. • LPS: Like other gram negative organisms have LPS on the outer cell wall, but it is less toxic than other GN. • Alginate:mucoidexopolysaccharide that forms a shiny biofilm protecting it from Ab’s, complement, phagocytosis and antibiotics.

20. 4. Exotoxin A: similar to Diphtheria toxin it inhibit protein synthesis (cause corneal damage). 5. Hemolysin: it break down lipids & contribute to tissue invasion & destruction. it is toxic to alveolar macrophages. 6. Proteases: play a major role during acute infection, It also have a rule in tissue invasion especially in corneal infections. 7. Elastase: destruction of elastin-containing tissues (eg. blood vessels, lung tissue, skin), collagen, immunoglobulins and complement.

21. Clinical Significance of P.auroginosa Some clinical diseases caused by P.auroginosa: • Pulmonary infections. • Burn wound infections and other skin and soft tissue infections (life threatening). • UTI’s (especially catheterized) • External Otitis (swimmer’s ear) • Eye infections and corneal ulceration via contaminated contact lens cleaning fluids. • Pseudomonal Endocarditis

22. Pulmonary Infections • Can range form asymptomatic colonization to severe necrotizing bronchopenumonia. • 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 abs , use of respiratory therapy equipment. • Mortality rate can be as high as 70% for invasive brnchopneumonia

23. Pseudomonas Corneal Ulcer • It is the most dreaded of all corneal infections. • There is rapid invasion and affection of deeper layers causing a central necrosis area within 48 hours and a ring abscess around corneal periphery. • Pus is mucus in consistency and greenish in color. • Hypopyon is unusually large. • Commonly associated with soft as well as extended contact lens wear.

24. Pseudomonas Corneal Ulcer

25. Treatment & Prevention • It is difficult to find antibiotics effective against P.aeruginosa because of its rapid development of resistance mutations and its own innate mechanisms of antibiotic resistance. • Generally a combination of two bactericidal antibiotics is essential for treatment

26. Haemophilus spp. General characteristics: • Morphology: Gram negative pleomorphic bacilli (ranging from coccobacilli to long filaments). • Obligate parasites, requiring special factors to grow like: hemin and NAD+ to grow. • Culture: • Facultative anaerobe, grows best in media enriched with CO2. • Temperature requirements 32°C - 37°C • Can grow on chocolate agar that contain hemin and NAD+.

27. The organism tend to cause widespread epidemics. • Non-motile. • Non-spore forming. • May produce capsule (6 capsular types have been distinguished a,b,c,d,e & f)

28. Haemophilus spp. • The commonest clinical isolate is Haemophilusinfluenzae(serotype b is most virulent type) • The other species of the genus include: • H. ducreyi • H. parainfleunziae. • H. aegyptius(eye infection)

29. Haemophilusinfluenzae

30. Pathogenecity of H.influenzae • Enters the body through respiratory tract. • Can produce IgA protease which helps in its attachment to respiratory mucosa. • It can cause respiratory infections such as otitis media, sinusitis and pneumonia (mostly non capsulated forms) • From this site, it can enter bloodstream and disseminate to distant sites (mostly capsulated forms (tybe b) is responsible for these diseases)

31. Treatment & Prevention Treatment: Third-generation cephalosporin such as ceftriaxone is drug of choice in meningitis and other serious infections. Prevention: By vaccination (Hib vaccine)