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1. D R . M A H A D I H A S S A N M A H M O U D
P H D , F I B M S , S C I
Skin & Wound infection

3. The wound infections are tow types:
 Minor wound infection:
 A small incision.
 Most self limiting.
 Mainly caused by S. aureus and
Some times S. pyogens.

4. Superficial skin infection
 Folliculitis is infection of the hair follicles
 A carbuncle is a cluster of infected
follicles commonly seen on the neck.
 Furuncles (boils) consist of walled-off
collections of organisms and associated
inflammatory cells in follicles and
sebaceous glands that may discharge pus.

5. Bacteria: many terms according to the
causative agents. e.g.: Boils (S. aureus)
impetigo (S. aureus & S. pyogens),
scalded skin syndrome (S. aureus),
cutaneous anthrax (B. anthracis) ... etc.

6.  Surgical (post operative) wound infection:
 Involve skin and subcutaneous tissue also
muscles, and deeper tissues.
 Start with reddening of wound edges with pus
formation.
 Pus gathers to form abscess.
 Fever may develop

7. Wound Infection
Complication
Complete breakdown
Spread of infection:
-local tissue
-blood

8. The causative agents of surgical wound:
 S. aureus , S. pyogens, Pseudomonas,
Enterobacteriacae (E. coli - Proteus –
klebsiella spp ) pseudomonas Enterococcus
faecalis).
 Anaerobic organisms (Bacteroids - C.
perfringens - anaerobic cocci).
 Mixed infection (coliform+enterococci)

9. Exogenous
(environment- equipment – personnel.
Endogenous
Organism carried in patients skin or
gut

10. Predisposing factors cause
wound infection in hospitals.
 Operation involving opening of the bowel.
 Presence of foreign bodies.
 Long operation.
 Large wound.
 Obesity.
 Anesthesia: stop the normal secretions of the
body which contains many bactericidal.
 Treatment by antimicrobial agents gives chance
for resistance (e.g.: Pseudomonas),

11. Burns
 Can be infected by the organisms that cause
wound infection (Pseudomonas - S.
pyogens - S. aureus). (Pseudomonas and S.
pyogens have many enzymes that prevent
healing of wound and cause destruction of
the skin).
 Compliction:speticeamia

12. Cellulitis
 Infection of subcutaneous tissues. Followed by
septicaemia,
 Acut pyogenic cellulitis
-the main causative agents are S. pyogenes.
 anaerobic cellulitis.
 Combination of areobe(coliform,peudomonas,
S,aureus and S. pyogens and anaerobic cocci
Bacteroids and rarely C. perfringens

13. catheters
 Wound and foreign body.
 Colonization with skin commensal then blood or
other tissues or fluid.
 Catheter may be arterial, venous, cannulae.
 Causes: S. epidermitis less often coliform,
S.aureus and yeast.
 Diagnosis: blood culture, other fludi, culture of
catheter tip.

14. Abscesses
 It is pus in subcutaneous tissues surrounded
by thick wall, (inflammation and fibrosis)
Usually the causative agent spread from
hair follicle.
 Antibiotic can not reach the organism
inside the fibrosis. (Surgery is a treatment).
The main causative agent is S. aureus.

15. necrotizing fasciitis
Streptococcal gangerne
Extensive necrosis, painful,Fever
,toximeia,shock
Synergistic gangrene
Due to mix infection with aerobic and
anaeroboc bacteria ,often following
surgery

16. Clostridial wound infection
Gasgangrene
C.perferingenes.
C.novyi.
C.speticum.
Toxieamia,oedema,blakining of the
tissues ,foul smelling.

17. LAB diagnosis :
 Specimen:
 Pus, wound swab, Blood for culture (post operative
wounds)
 Macroscopical examination:
 The color differs according to causative agents' e.g.
creamy & thick pus: Staph, straw & water: Strept, fishy
smell: Proteus, musty odor, Green-blue pigment:
Pseudomonas. Present of granules (Grains:
Actinomyces).

18. LAB diagnosis:
 Direct gram stains:
 Important and helpful.
 Culture:
 Two Blood Agar (O2 +an O2), CLED (better than
MacConkey) or MacConkey.
 KVBA for Bacteroids.
 Neomycin BA for Clostridia.
 Cooked meat media is helpful

19. LAB diagnosis:
 Identification:
 Colonial morphology - Gram stains -
Biochemical

20. LAB diagnosis :
 Specimen:
 Pus, wound swab, Blood for culture (post operative
wounds)
 Macroscopical examination:
 The color differs according to causative agents' e.g.
creamy & thick pus: Staph, straw & water: Strept, fishy
smell: Proteus, musty odor, Green-blue pigment:
Pseudomonas. Present of granules (Grains:
Actinomyces).

21. Wound infections

22.  Wounds:
1 - accidental
2 - surgical (post-operative)
wound infections:
- more serious
- involve the skin,
subcutaneous &
deeper tissues

23. Clinical features:
- redness of the wound edges
- pus formation
- fever
Complications:
• wound dehiscence: break down
• spread of infection:
- local
- blood: septicaemia & septic
shock

25. Source:
 Endogenous:
- the normal flora:
skin, GIT
- colonization by antibiotic
resistant strains in hospitals
 Exogenous:
from:
environment, the staff,
instruments

26. Surgical wound infections are:
Mixed infections
Causative agents:
Aerobic & Fano:
Staph.aureus
E.coli
Proteus sps
Klebsiella pneumoniae
Enterococci
Pseudomonas aeruginosa

27. Anaerobic:
Bacteroides fragilis
anaerobic cocci
Cl.perfringines

28. Diagnosis:
specimen:
- Pus or exudate:
collected in
- sterile container
- swab: duplicates
(o2 & ano2)
- Blood for culture:
septicaemia: fever, shock

29. Macroscopy of pus:
S.aureus: creamy, thick,
(intact pus cells)
St.pyogenes: straw-colored, thin
lysis of pus cells
Proteus: fishy smell
Pseudomonas: sweet, fruity
odour, blue pigment
Anaerobic: offensive smell

30. Microscopy:
Gram stained smears:
bacteria & pus cells
Culture:
- 2 plates of blood agar:
one is incubated aerobically
the other in anaerobic conditions
- MacConkey
- Cooked meat broth: anaerobes.

31. Sensitivity test:
- Benzylpenicillin
- Gentamicin disc
- Metronidazole disc:
for anaerobes . .

32. Special types
of
wounds infections

33. 1- Burns:
extensive burn:
have large, moist exposed area
Causative agents:
Strept. pyogenes
Pseudomonas aeruginosa
+ other organisms of wound
infection

34. Septicaemia & septic shock:
a serious complication in
burn

35. 2- Clostridia wound infection:
Gas gangrene:
Causative agents:
Cl. perfringenes (65%)
other gas gangrene group:
Cl.novyi
Cl.septicum
Cl.histolyticum
Cl.sordelli

36. Clinical features:
- a spreading gangrene of the
muscles
- toxaemia
- shock
- wound: edema, blackening of the
tissues, foul smelling exudate
crepitus ( gas under the tissues)

40. Culture of C.perfringensin Cooked Meat
medium showing (sacchrolyticolytic )

42. C. perfringenes : Gram +ve brick shaped

43. C.perfringens on Blood agar
double zone of haemolysis

44. Naglar reaction

47. Pathogenesis:
contamination of wounds by dirt
and soil containing spores
- The presence of necrotic tissues,
blood clot, foreign body, vascular
damage favour the infection.
- may follow abdominal surgical
operations.

48. - Virulence factors:
alpha toxin: A1
lecithinase C
(phospholipase)
- causes damage to cell
membrane of muscles
other tissues :RBCs
- haemolytic anaemia
- jaundice

49. laboratory diagnosis:
specimen:
exudate or tissues
Microscopy:
Gram stained smears:
Gram +ve brick shaped bacilli
Culture:
- Cooked meat broth:
sacchrolytic effect
- Neomycin blood agar

50. double zone of haemolysis
Biochemical tests:
toxin detection:
Naglar reaction

51. Bone infection
Acute osteomyelitis:
common in children<10 years
presents with bone pain, fever
Causative agents:
Staphylococcus aureus
Haemophilus influenzae
Streptococcus pyogenes
group B streptococci

52. rare:
- Pseudomonas aeruginosa
- Salmonella sps
Diagnosis:
- blood culture
- X-ray
Chronic osteomyelitis:
causative agents:
S.aureus
M.tuberculosis

53. G-ve enterobacteria:
Pseudomonas
Salmonella
Brucella
Treponema pallidum
Diagnosis:
- pus collected from discharging
sinuses (chronic)
- blood culture (acute)

54. Septic arthritis:
- occur as an extension of
osteomyelitis
- complication of septicaemia
- following operations or injection
inside joints
Causative agents:
+ N.gonorrhoea
N.meningitidis
Strept.pneumoniae

55. Laboratory diagnosis:
examination of fluid aspirated
from the joints:
microscopy
culture
serology

56. Skin infections

57. Staph.aureus:
1- boils
2- carbuncle
3- localized abscess
4- stye
5- impetigo
6- cellulitis
7- scalded skin syndrome

60. carbuncle

61. Impetigo

62. Impetigo

63. sycosis barbae

64. Staphylococcal abscess

67. Strept.pyogenes:
1- impetigo
2- cellulitis
3- necrotizing fasciitis
4- Erysipelas

74. Leprosy:
tuberculoid
lepromatous
border-line

75. Tuberculoid leprosy

77. Parasitic skin lesions:
1- itchy:
Scabies: Sarcoptes scabei
mite: arthropode
 female burrow into superficial
layers of loose thin wrinkled skin
 clinical feature:
a very itchy papular rash along
burrow

79. Sarcoptes scabiei

80. Scabiasis

81. Transmitted by close contact, sexual
 confirmed by scraping of skin over
a burrow, pick up female mite
examined by hand lens.
 treatment:
topical: Benzylbenzoate
lindane

82. Onchocerciasis:
Causative agent:
Onchocerca volvulus
Transmitted by: black fly
Simulium damnosum
Infective stage: microfiliaria
Adult worm: nodules over bony
prominence
Microfilaria: itchy papular rash

83. Simulium damnosum: (black fly)
vector of Onchocerca volvulus

84.  Prolonged heavy infection:
depigmentaion: leopard skin
loss of skin elasticity,
hanging groin
Diagnosis:
skin snip: in normal saline
to see microfilaria
Treatment: Ivermectin

85. Myiasis:
fly maggots (larva) invade
living tissues
- cutaneous myiasis:
maggots penetrate skin
form a small itchy papule
Lymphadenopathy, fever
diagnosis
- Body cavity Myiasis: nose, ear..

86. Skin ulcers:
Bacterial:
cutaneous anthrax:
Mycobacterium ulcerans
(Buruli ulcer)
Parasitic:
cutaneous leishmaniasis
Guinea worm

87. Cutaneous leishmaniasis

90. Promastigotes: in culture of leishmania

91. Bacillus
Bacillus anthracis

95. Cutaneous Anthrax: massive oedema

97. Cutaneous anthrax: typical ulcer with black escher

101. M.ulcerans:
Buruli ulcer

103. Guinea worm:
Dracunculus medinensis:
- tissue nematode Transmission:
ingestion of water flea:
Cyclops in drinking water
larva released in gut, migrate
to the s/c tissues
form a papule: ulcerate

104. Larva are released in water,
Ingested by Cyclops to form the
infective larva

105. Guinea worm: Dracunculus medinensis

107. Cyclops: water flea: intermediate host of
Dracunculus medinensis

108. Good luck