ABOUT MEDIA

The formulation and the components can be divided into different roles or functions:

1. Nutrients: proteins/peptides/amino-acids.
2. Energy: carbohydrates.
3. Essential metals and minerals: calcium, magnesium, iron, trace metals: phosphates, sulphates etc.
4. Buffering agents: phosphates, acetates etc.
5. Indicators for pH change: phenol red, bromocresol purple etc.
6. Selective agents: chemicals, antimicrobial agents.
7. Gelling agent: usually agar.

There is often an overlap of functions of some media components, thus protein hydrolysates will supply
amino-nitrogen, energy, some metals/minerals and
act as buffering agents. Phosphate buffers are important suppliers of minerals and agar contributes metals


**EXAMINATION OF CLINICAL SAMPLES

In both clinical and veterinary microbiology the purpose of examining samples of tissue, fluids or excreta is
to isolate and identify pathogenic organisms.
Although both fields of investigation have common interests and common organisms, they are separate
specialist activities. Reference should be made to the appropriate specialist publications in either field to
obtain specific guidance.
It should be stressed that every specimen must be evaluated, many laboratories cannot cover the whole
microbiological field, the various infective agents should be taken into consideration and, if necessary,
material referred to the appropriate reference laboratory.
Poor specimen samples can only yield poor or misleading results. It is important that personnel collecting or
taking samples are instructed by the laboratory to prevent faulty collection procedures.
Satisfactory samples, collected without extraneous contamination and before antimicrobial therapy should
be transferred to the laboratory with minimal delay. If transportation is required then appropriate transport
media should be used to protect delicate organisms. Where quantitative results are important e.g. urine
cytology and bacteriology, or where commensal overgrowth should be prevented, refrigeration of samples at
2-8°C is essential.
All samples should be clearly labelled and sent in leak-proof, satisfactory containers. Sealed, transparent
plastic bags, containing the sample container and the request form attached to but not inside the plastic
bag, is the most acceptable method of sending pathological samples to the laboratory.


#BLOOD CULTURES

Associated pathogens:
Staphylococci (coagulase positive and negative)
Streptococci (alpha/beta/non-haemolytic strains)
Coliform organisms (including other enteric organisms)
Non-fermentative organisms (Pseudomonas and Acinetobacter species)

Anaerobes (Clostridia, Bacteroides, Fusobacterium species and anaerobic cocci)
Neisseria species
Haemophilus influenzae
Brucella species



Commensal organisms:
None.



#CEREBROSPINAL FLUID (CSF)

Associated pathogens:
Haemophilus influenzae
Neisseria meningitidis
Streptococcus pneumoniae
Mycobacterium tuberculosis
Listeria monocytogenes
Nocardia species and Bacillus Cryptococcus neoformans Coliform bacilli, Pseudomonas species and Group
B streptococci occur in neonates.
Patients involved in surgical manipulations e.g. shunts, valves etc., can become infected with
Staphylococcus epidermidis and micrococci.



Commensal organisms:
None.



#SPUTUM

Associated pathogens:
Staphylococcus aureus
Streptococcus pneumoniae
Haemophilus influenzae
Coliform bacilli
Klebsiella pneumoniae
Pasteurella species/Yersinia species
Mycobacterium tuberculosis
Branhamella catarrhalis
Mycoplasma species
Legionella species
Candida/Aspergillus/Histoplasma/Cryptococcus/Blastomyces species



Commensal organisms:
Staphylococcus epidermidis
micrococci
non-pathogenic neisseria
Streptococcus viridans
Candida
coliform bacilli.



#EAR SWABS

Associated pathogens:
Staphylococcus aureus
Streptococcus pyogenes
Haemophilus species
Corynebacterium diphtheriae
Pseudomonas aeruginosa
Coliform bacilli
Bacteroides/Fusobacterium species
Fungi



Commensal organisms:
Micrococci
diphtheroids
Staphylococcus epidermidis



#NOSE SWABS

Associated pathogens:
Staphylococcus aureus
Streptococcus pyogenes
Neisseria meningitidis
Bordetella pertussis
Haemophilus species
Corynebacterium diphtheriae



Commensal organisms:
Diphtheroids
Stapylococcus epidermidi
nonpathogenic neisseria
Bacillus species
coliform bacilli.



#THROAT SWABS

Associated pathogens:
Streptococcus pyogenes
Corynebacterium diphtheriae
Corynebacterium ulcerans

Staphylococcus aureus
Neisseria meningitidis
Candida albicans
Borrelia vincenti



Commensal organisms:
Streptococcus viridans
Staphylococcus epidermidis
diphtheroids
Streptococcus pneumoniae
Haemophilus influenzae non-type B
non-pathogenic neisseria



#URINE

Associated pathogens:
Escherichia coli
Enterobacter and Proteus species
Staphylococci (coagulase positive and negative)
Enterococcus
Mycobacterium tuberculosis



Commensal organisms:
When in doubt contact the physician or repeat the sample.



#PUS AND WOUND SWABS

Associated pathogens:
Staphylococcus aureus
Streptococcus pyogenes
Anaerobic cocci
Clostridia species
Bacteroides species
Pasteurella species
Yersinia species
Actinomyces species
Mycobacterium species
Bacillus anthracis
Listeria monocytogenes
Proteus and Pseudomonas species
Nocardia and other fungi



Commensal organisms:
Pus - none
Wound swabs - small numbers of skin commensal organisms



#EYE SWABS (purulent discharges)

Associated pathogens:
Staphylococcus aureus
Streptococcus pneumoniae
Neisseria gonorrhoeae
Haemophilus species
Chlamydia trachomatis
Moraxella species
Corynebacterium diphtheriae
Pseudomonas aeruginosa
Coliform organisms


Commensal organisms:
Staphylococcus epidermidis
Micrococcus species


#FAECES, FAECAL AND RECTAL SWABS

Associated pathogens:
Bacillus cereus
Plesiomonas shigelloides
Clostridium botulinum


Commensal organisms:
Coliform bacilli
Proteus species
Pseudomonas species
Bacteroides species
Clostridium species.