Pus, Ulcer Material, Skin Specimens: Culture and sensitivity test

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.

Sample collection


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.

Describe Specimen

For additional investigations
Look for granules: When mycetoma or actinomycosis is

Culture Pus, Ulcer Material, Skin Specimens

Blood agar
Incubate aerobically
MacConkey agar
Incubate aerobically
Cooked meat medium

For anaerobic bacteria
Subculture at 24 hours , 48 hours, and 72 hours as indicated

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

Gram smear
For pus cells and bacteria

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
Dark-field microscopy:
To detect treponemes when
yaws or pinta is suspected

Day 2 and Onwards

Examine and Report Cultures of Pus, Ulcer Material, Skin Specimens
Blood agar and MacConkey agar cultures
Look particularly for:
S. aureus
S. pyogenes
P. aeruginosa
Proteus species
E. coli
Enterococcus species
Klebsiella species
C. perfringens
Bacteroides fragilis group
Peptostreptococcus species

Biochemical tests

Depending on the nature of organisms

Antimicrobial susceptibility test

Antimicrobial sensitivity pattern also depends on the nature of organism involvement

On 3rd day

Organism isolated

Antimicrobial sensitivity pattern

Sensitive (S)

Resistant (R)

Intermediate (I)

Possible pathogens of pus

Gram positive
Staphylococcus aureus
Streptococcus pyogenes
Enterococcus species
Anaerobic streptococci
Other streptococci
Clostridium perfringens
and other clostridia
Actinomyces israeli
Also Mycobacterium tuberculosis
Gram negative
Pseudonomas aeruginosa
Proteus species
Escherichia coli
Bacteriodes species
Klebsiella species
Pasteurella species
Candida albicans,
mycetoma causing fumgi
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
Gram positive
Staphylococcus aureus
Streptococcus pyogenes
Enterococcus species
Anaerobic streptococci
Erysipelothrix rhusiopathiae
Bacillus anthracis
Gram negative
Escherichia coli
Pseudomonas aeruginosa
Yersinia pestis
Vincent’s organisms
Mycobacterium leprae

Mycobacterium ulcerans,

Treponema carateum,

 Treponema pertenue.

herpes viruses
Dermatophytes (ringworm fungi)
Malassezia furfur
Fungi that cause chromoblastomycosis
Candida albicans

Leishmania species
Onchocerca volvulus
Dracunculus medinensis

Commensal organisms that may be found on the
skin include:
Gram positive
Anaerobic cocci
Viridans streptococci
Propionibacterium acnes
Gram negative
Escherichia coli
and other coliforms


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