Pus, Ulcer Material, Skin Specimens: Culture and sensitivity test
Introduction of Pus, Ulcer Material, Skin Specimens
Pus, Ulcer Material, Skin Specimens are common samples for microbiological examination in a tertiary care center set up like gram stain, culture and sensitivity.
Container: Aerobic swab moistened with Stuart’s or Amie’s medium
Patient preparation: Wipe area with sterile saline or 70% alcohol. Swab along leading edge of wound.
Transport to the laboratory: Within 24 hours art room temperature.
Pus from an abscess is best collected at the time the abscess is incised and
drained, or after it has ruptured naturally. When collecting pus from abscesses, wounds, or other sites, special care should be taken to avoid contaminating the specimen with commensal organisms from the skin. As far as possible, a specimen from a wound should be collected before an antiseptic dressing is applied.
For additional investigations
Look for granules: When mycetoma or actinomycosis is
Culture Pus, Ulcer Material, Skin Specimens
Incubate aerobically MacConkey agar
Incubate aerobically Cooked meat medium
For anaerobic bacteria
Subculture at 24 hours , 48 hours, and 72 hours as indicated
Optional Neomycin blood agar when anaerobic infection is suspected
Incubate anaerobically up to 48 h Culture for M. tuberculosis or M. ulcerans
Requires facilities of a
Tuberculosis Reference Laboratory
Examine Microscopically of Pus, Ulcer Material, Skin Specimens
Optional steps Ziehl-Neelsen smear:When tuberculosis or M. ulcerans disease is suspected KOH preparation:
When a fungal or actinomycete infection is suspected Giemsa or Wayson’s smear:
When bubonic plague is suspected Polychrome methylene blue:
When cutaneous anthrax is
suspected Dark-field microscopy:
To detect treponemes when
yaws or pinta is suspected
Antimicrobial sensitivity pattern also depends on the nature of organism involvement
On 3rd day
Antimicrobial sensitivity pattern
Possible pathogens of pus
Bacteria Gram positive Staphylococcus aureus Streptococcus pyogenes Enterococcus species Anaerobic streptococci Other streptococci Clostridium perfringens
and other clostridia Actinomycetes Actinomyces israeli
Also Mycobacterium tuberculosis Gram negative Pseudonomas aeruginosa Proteus species Escherichia coli Bacteriodes species Klebsiella species Pasteurella species Fungi
mycetoma causing fumgi Parasites Entamoeba histolytica
(in pus aspirated from an amoebic liver abscess)
Any commensal organisms found in pus are usually those that have contaminated the specimen from skin, clothing, soil, or from the air if an open wound.
Ulcer Material and Skin Specimens
Possible pathogens Bacteria
Gram positive Staphylococcus aureus Streptococcus pyogenes Enterococcus species Anaerobic streptococci Erysipelothrix rhusiopathiae Bacillus anthracis Gram negative Escherichia coli Proteus Pseudomonas aeruginosa Yersinia pestis
Vincent’s organisms Mycobacterium leprae
Treponema pertenue. Viruses
herpes viruses Fungi
Dermatophytes (ringworm fungi)
Fungi that cause chromoblastomycosis
Parasites Leishmania species Onchocerca volvulus Dracunculus medinensis
Commensal organisms that may be found on the
Diphtheroids Propionibacterium acnes
Gram negative Escherichia coli
and other coliforms
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