1. Microorganisms infecting the skin

2. WOUNDS AND ABSCESS
Infections of soft tissues are associated with production of pus and said pyogenic.
A wide variety aerobic and anaerobic species participate singly or in combination in infectious of wounds.

3. WOUNDS AND ABSCESS
The commonest pyogenic bacteria are S.aureus, S .pyogenes ,P. aeruginosa, coliforms bacilli., anaerobic organisem :particularly Clostridium perfringens , bacteroides spp ,anaerobic cocci..
In many cases there is a mixed infection with more than one bacterial spp.

4. Wound infection and abscesses occur as complication of surgery, trauma or disease that may interrupt a mucosal or skin surface.

5. wounds Wound infections may be endogenous or exogenous.
Endogenous infections are caused by organisms that are in commensal in the patient .
Exogenous infections the source is out of the body cross-infection is a particular example. the causal organism is spread from person to person. infection may occur after accidental or intentional trauma of the skin or tissue. (Surgical postoperative sepsis. )

6. Lab procedure
Firstly. In order to identify the different microorganism that cause wound infection, we should collect a proper specimen from the area of the wound.

7. 1- Aspiration Technique
This method considered to be the perfect and the most used method for specimen collection from an abscess or deep wound area.
Disinfect the area by using 70% alcohol.
Local anesthetic by using pethedin.
Insert sterile needle deeply inside the abscess of the wound and aspirate the largest amount of specimen.

8. 2- Swab procedure
Swabs are inefficient sampling and are strongly discouraged. It is not common as the aspiration because it holds less volume and more subjected to contamination.
Disinfect using 70 % alcohol.
Local anesthetic by using pethedin.
Open the abscess with a sterile knife and drain the puss and purulent material that gets out.

9. D. put the sterile cotton swab in the area of the draining and rotate it to get the largest volume possible and then place the swab in its special container.
E. clean the area of the wound and remove the pus.

10. Transportation
Transport the specimen to the lab as soon as possible. In case ……
Aspirated specimen: put it in to anaerobic containers, in which oxygen is excluded or filled with Co2. (Keep at Moist conditions & Room temperature).
Swab specimens: the cotton should be put in transport media called stiurts media. to preserve the specimen from drying and prevent the over growth of rapidly growing microorganism.

11. Laboratory examination
Special methods of examination should be applied to particular specimens.
the basic procedures usually include
Naked eye examination, (for macroscopy criteria ,such as color , odor consistency,..)
The microscopical examination,
Culture

12. Microscopy
Much useful information may be obtained from smear by Gram-staining. We should notice
presence and relative numbers of PMNs and bacteria.
morphology of Gram – positive or Gram – negative bacteria.
Examination of a wet film for fungi or motile bacteria.
A smear stained by the Ziehl- Neelsen method should be examined when the clinical circumstances suggest the tubercle bacillus., another mycobacterium or a nocardia may be present

13. Specimen processing

14. inoculation
Aspirated specimen: if it is thick we should emulsify in normal saline or thioglycolate media in order to make suspension. And we do the culture by streaking method.

15. Colonies of Streptococcus pyogenes on sheep blood agar.
Notice: * Presence of b hemolysis around colonies
* Enhanced hemolysis around stabbing sites
* Sensitivity to bacitracin (Disk A)

16. Streptococcus pyogenes
Pin point colony: (white or gray)
Gram stain: G+ve, cocci, single chain.
Catalase enzyme: differentiate between
Streptococcus –ve
Staphylococcus +ve

17. Staphylococcus aureus
Identification Process
Microscopic morphology
• Gram Positive Cocci in clusters

18. IDENTIFICATION PROCESS
Biochemical Tests
Catalase
• Coagulase
• Mannitol salt Agar growth

19. 1. Catalase Test Place a drop of 3% H2O2 on glass slide.
Select colonies to be tested
Mix colonies in drop of H2O2 (Hydrogen Peroxide)
H2O2 H2O + O2
catalase

20. Catalase Test Bubbles = positive catalase present
No bubbles = negative
no catalase present
All Staphylococcus species are catalase positive

21. Catalase +ve
Catalase -ve

22. COAGULASE TEST:
Coagulase converts fibrinogen to fibrin
Pathogenic strains coat themselves in fibrin to evade immune system

23. 3. Growth on Salt Mannitol agar
streak plate with organism
if mannitol is fermented - acid is produced
Phenol red (indicator) turns yellow in presence of acid
• incubate hrs at 37o C
Coagulase-negative Staphylococi
Growth seen, but no color change
Staphylococcus aureus
Growth AND color change

24. Pseudomonas aeruginosa
Greenish discoloration of media due to production of pyocyanin by Pseudomonas aeruginosa

25. Pseudomonas aeruginosa
Results of oxidase test

26. CLOSTRIDIUM SPECIES
Genus Clostridium consists of Gram positive, anaerobic, spore forming bacilli.
Common Species
Clostridium perfringens – Gas gangrene
Clostridium botulinum – Botulism
Clostridium tetani – Tetanus

27. Microscopic morphology
Clostridium perfringens Clostridium tetani
Gram Positive bacilli Gram positive bacilli with drum stick appearance

28. Anaerobic Jar & Gas Pack

29. Leishmaniasis Obligatory intracellular belong to genus Leishmania
It is transmitted by sandflies.

30. Morphological stages of the Leshmania spp. affecting humans
Leishmania species
Intracellular in macrophages in humans
Amastigote
In midgut, then proboscis of sandfly ( infective stage to human) and in culture
Promastigote

31. Amastigotes of Leishmania

32. Promastigotes of Leishmania

33. Mode of infection Bite of female sand flies
Phlebotomine (in Old World)
promastigotes (infective stage)

34. Life cycle
Depending on the species of parasite amastigotes may

35. cutaneous leishmaniasis
Diagnosis:
Smear: Giemsa stain – microscopy for LD bodies (amastigotes)
Biopsy: microscopy for LD bodies or culture in NNN medium for promastigotes

36. NNN medium
agar slant overlaid with defibrinated rabbit blood used to detect the presence of Leishmania.

38. Schistosomiasis
Females are slender and delicate, whereas males are much bigger and have a spiny trough or groove into which the female fits and locks in.
The male consumes blood and feeds the female most of it, which she turns into eggs, which pass out of the host and can begin the life cycle again.

39. Blood fluke is a special kind of flukes because of following characters:
(1) The adult worms look like nematodes, elongated cylindrical in shape. (2) Two sexes are separate. (3) egg without operculum, but with a terminal spine. (4) only one intermediate host required. (5) The infective stage is cercaria. (6) The infective route is by skin. (7) The eggs are main pathogenic stage.

41. Paired male and female adult worms
Paired male and female adult worms. The female is the darker, curled worm within the male's gynacophoric canal.

42. Mature egg is oval in shape, slight yellow in color, shell is thin without an operculum but with a terminal spine. The content is a miracidium. Cercaria is infective stage. It is composed of the body and forked tail (including tail stem and fork) and has 5 pairs of penetrating glands in the body.

43. oval in shape, slight yellow in color, shell is thin without an operculum but with a terminal spine.

44. A Comparison of Schistosome Eggs
S. mansoni
Lateral spine
S. haematobium
Terminal spine
S. japonicum
No spine

45. Cutaneous Fungal Infections
Dermatophytosis - "ringworm" disease of the nails, hair, and the skin caused by fungi called dermatophytes.
Dermatomycosis  - more general name for any skin disease caused by a fungus.

46. Diagnosis Note the symptoms.
Microscopic examination of slides of skin scrapings, nail scrapings, and hair.  Often tissue suspended in 10 % KOH solution to help clear tissue.