1. (Wounds, Abscesses, Burns, Sinuses)
Pyogenic Infections
(Wounds, Abscesses, Burns, Sinuses)
Possible Pathogens
@ Gram negative bacteria:
# Pseudomonas aeruginosa, Proteus spp.
Escherichia coli, Bacteroides spp,
Klebsiella spp., Pasteurella spp.

3. @ Gram positive bacteria:
# Staphylococcus aureus, Streptococcus
pyogenes, Enterococci, Anaerobic
streptococci, other streptococci,
Clostridium tetani, Cl. perfringens,
Actinomycetes, Myco. tuberculosis.
@ Fungi:
# Mycetoma spp, Histoplasma,
Blastomyces, C. albicans, Cryptococcus
neoformans.

5. Association with Pyogenic Infections:
@ S. aureus causes abscesses and skin
infection
@ P. aeruginosa is associated with
burns and hospital cross infections.
@ E. coli, Proteus spp, P. aeruginosa,
and Bacteroides spp. are pathogens
isolated from abdominal abscesses.

7. @ C. perfringens is found in deep wounds
and gas gangrene.
@ C. tetani causes umbilical neonatal
infection.
@ Bacteroides spp. cause infections
of respiratory tract and female genital
tract.
@ M. tuberculosis causes cold abscesses
without inflammation

9. Commensals
@ Commensal organisms found in pus is
due to specimen contamination while
collection.
@ Sources of contamination are:
the skin, clothes, soil, or air
@ Commensal skin organisms may cause
acne vulgaris

11. Lab. Diagnosis of Pyogenic Infections
Collection and Transport:
@ Collect 5 ml of pus in sterile container
@ If pus is absent, use a swab and put
in Amies transport medium.
@ If mycetoma is suspected, collect
from a sinus by a needle.
@ If tuberculosis is suspected, aspirate
pus and put in a container.

13. Macroscopy:
@ Look and report:
# Colour of pus
# Colour of granules: white, yellow,
brown, red, or black.
# Shape, size, and consistency of
granules.
# A magnifying lens is to identify
granules of mycetoma.
# Colour of amoebic abscess pus: red
brown, grey, yellow

15. Microscopy
Gram smear:
@ Examine a stained smear for:
# Gram positive cocci (S. aureus,
streptococci, enterococci).
# Gram negative rods (Proteus, E. coli
P. aeruginosa, Bacteroides) .
# Gram positive rods (C. perfringens).
Ziehl-Neelsen smear:
@ Examine for acid fast bacilli.

17. Potassium hydroxide preparation:
@ Specimen without granules:
# Look for: Budding of Candida and
C. neoformans. Look for branching
of Nocardia.
@ Crush granules on a slide, mix with
potassium hydroxide, and look for
mycetoma granules and Actinomyces
yellow granules.

19. Culture:
@ Inoculate one blood agar plate and
Mac Conkey agar plate and incubate
aerobically at 37°C overnight.
@ Inoculate a neomycin plate & a second
blood agar plate and incubate at 37°C
anaerobically for up to 48 hours.
@ Inoculate a cooked meat medium and
incubate at 37°C for up to 72 hours.

21. @ For TB, decontaminate the specimen by
immersing in 4% sodium hydroxide
solution for 10 minutes, and inoculate
an LJ slope and incubate for 8 weeks
@ For fungi, inoculate a Sabouraud agar
Examination of Cultures
@ In LJ slope: Look for M. tuberculosis
producing raised, dry, creamy colonies.

23. @ In blood, neomycin, Mac Conkey agar:
Look for colonies of S.aureus, E. coli,
ß-haemolytic Strep, Cl. perfringens,
Pseudomonas, Proteus, Enterococcus,
Bacteroides spp, and anaerobic cocci
@ In cooked meat medium: Look for
turbidity, reddening of the meat, gas
bubbles (Cl. Perfringens), decomposition
& blackening of meat (Bacteroides)
@ Subculture the cooked meat medium if
the anaerobic plates were sterile.