Finding the right tests…
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Finding the right tests…
Microbiology
Aerobic culture and sensitivity looks for bacteria that need oxygen to multiply, grown from a wound swab, pus, or tissue sample your doctor suspects is infected. Most bacteria behind everyday skin, wound, and soft-tissue infections, including Staphylococcus aureus, Streptococcus species, and E. coli, fall into this group, which is why an aerobic culture is usually the first test sent from a draining wound or a collection of pus. The lab spreads your sample onto growth media inside a standard, oxygen-rich incubator and checks it for colonies over the following days. Once something grows, the lab identifies the organism and tests it against a panel of antibiotics, so your doctor can pick one that actually works.
This test reports two things: whether bacteria grew from your sample, and if they did, which one. A positive result names the organism, such as Staphylococcus aureus or E. coli, and lists antibiotics as sensitive, resistant, or intermediate against it. A negative or no-growth result means no aerobic bacteria multiplied from your sample in the time the lab allowed, which is reassuring but does not rule out an anaerobic organism or a slower-growing one - that is why doctors often send a second sample for anaerobic culture from the same site.
Your sample is spread onto a blood agar plate and a second selective plate, then placed in a standard incubator with regular room air. Bacteria that need oxygen to build energy multiply and form visible colonies. A technician checks the plates daily and notes a colony's size, shape, and color before running identification tests.
Finding an organism is only half the job. The lab exposes it to antibiotic discs and reads which drugs stop it from growing, which do not touch it, and which sit in between. Your doctor uses this list to choose a working antibiotic instead of a broad-spectrum guess.
Deep or pus-forming infections are frequently caused by a mix of oxygen-dependent and oxygen-avoiding bacteria growing together. A study of abscess and wound specimens found aerobic bacteria alone in about a quarter of cases, anaerobes alone in over a third, and both together in the rest, so a lab that only runs an aerobic culture on a deep wound can miss part of the picture.
A negative result means nothing grew under aerobic conditions in the time given. That is a useful answer, but it does not test for anaerobic bacteria, viruses, or fungi.
Aerobic bacteria need oxygen to grow, so the lab incubates your sample in normal room air rather than sealing it away from oxygen. Most bacteria that cause common wound and skin infections fall into this category, which is why this is usually the first culture sent.
An anaerobic culture looks for bacteria that are damaged or killed by oxygen, so the lab handles that sample differently and incubates it in an oxygen-free chamber. The two tests are often ordered together from the same wound because many deep infections involve both types of bacteria.
No growth means no aerobic bacteria multiplied from your sample in the time the lab allowed. It does not automatically rule out infection, since an anaerobic organism, a fungus, or a very slow-growing bacterium could still be present.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
Yes, if bacteria grow. The lab runs a sensitivity panel that shows which antibiotics work against the specific organism found, which is more precise than starting treatment based on symptoms alone.
Deep wounds and abscesses are often infected by a mix of bacteria that need oxygen and bacteria that avoid it. Sending both cultures from the same sample gives a fuller picture than either test alone.
Antibiotics already in your system can suppress bacterial growth and produce a false negative. Ask your doctor or the centre about timing before you start or stop any medicine on your own.