Apply aseptic technique, sterilisation and infection-control principles.

Aseptic Technique, Sterilisation and Infection Control

Start from one sentence: organisms cause infection only when enough of them reach a site they should never have reached, in a host who cannot clear them. Every technique in this chapter is one of three moves against that sentence — lower the number of organisms (bioburden), keep them away from vulnerable tissue, or keep the host able to defend. Infection prevention is microbiology made operational, and everything that follows is built on this single idea.

That makes the logic concrete. To cause a surgical-site infection, organisms must (1) exist somewhere, (2) be carried to the wound, (3) cross into tissue, and (4) outpace local defence. Break the chain at any link and the infection does not happen. The reason "wear gloves" is not enough is that gloves attack only one link; real infection prevention is a bundle of barriers across all of them.

In O&G this applies to speculum clinics, IUCD insertion, miscarriage care, termination of pregnancy, labour ward, caesarean section, hysteroscopy, laparoscopy, urinary catheterisation, neonatal contact, wound care and outbreak care. A caesarean wound infection, septic miscarriage, catheter-associated urinary tract infection, puerperal sepsis case or neonatal cluster is never "a nursing problem" — it is microbiology plus workflow, and it is core O&G safety.

At this level, learn the chain of infection, what killing organisms actually means in numbers, the logic of clean/aseptic/sterile, standard precautions and source-control microbiology. Procedure-specific technique belongs in Intermediatesurgical instruments and safe use, Intermediatesafe caesarean technique and clinical infection chapters such as Finalpuerperal sepsis.

The exam mindset is:

reduce bioburden -> protect key parts and key sites -> prevent transmission -> remove infected source -> learn from clusters

Chain of Infection

Infection-control measures break the chain of infection.

The chain shows why "wear gloves" alone is inadequate. IPC is a bundle of barriers.

O&G Chain Examples

What "Killing Organisms" Actually Means

Before any technique makes sense, you have to know what "clean", "disinfected" and "sterile" mean in numbers, because they are not the same achievement. They sit on a ladder of how far the microbial population is reduced.

The starting population on a soiled instrument is its bioburden — the number and type of viable organisms present. Decontamination drives that number down in stages, and each stage is defined by how much of the population it removes, not by how clean the object looks.

The crucial gap is between disinfection and sterilisation, and it is best understood quantitatively.

Log Reduction and the Sterility Assurance Level

Microbial killing is exponential, so it is measured in log (ten-fold) reductions. A process that takes a population from one million organisms to ten has achieved a 5-log (10^5) reduction — that is roughly the scale a good disinfection step delivers. Disinfection is therefore a large but finite knock-down: enough organisms can survive that the object is not guaranteed organism-free.

Sterilisation is defined more strictly. A correctly validated sterilisation process is held to a sterility assurance level (SAL) of 10^-6: the probability that any single processed item still carries a viable organism is no greater than one in a million. Put concretely, if you sterilised a million surgical packs, at most one would be expected to contain a single surviving organism. This is why "sterile" is a probability target reached by a validated process, not a judgement made by looking at an instrument.

Two consequences follow directly, and both are common exam points:

• A clean-looking instrument is not a sterile instrument. Cleaning lowers bioburden but proves nothing about spores. Sterility is only ever as good as the validated cycle and the maintenance of the sterile barrier afterwards.
• Disinfection cannot be substituted for sterilisation on items entering sterile tissue. A 5-log reduction still leaves room for survivors, and spores may be untouched. For instruments crossing into sterile tissue or the bloodstream, only sterilisation reaches the required assurance.

Why Cleaning Always Comes First

Sterilisation fails if cleaning fails, and the reason is mechanical. Organic material — dried blood, tissue, mucus, pus — physically shields organisms from heat, steam and chemicals, and on a complex device it also feeds biofilm. A sterilant that cannot reach an organism cannot kill it. Sterilisation is therefore always preceded by cleaning (and often a disinfection step) to drop the bioburden and strip away protective soil before the lethal step is attempted. This is why a quick wipe of a soiled instrument is not reprocessing, and why point-of-use handling that stops blood drying matters.

What Resists, and Why It Matters

Not all microbial targets are equally hard to kill, and the order matters for choosing a process.

A separate, easily missed point: killing organisms does not remove everything dangerous they leave behind. Heat-killed Gram-negative bacteria still leave endotoxin (a heat-stable pyrogen), so water and equipment can be microbiologically "dead" yet still provoke a febrile reaction. Sterility and freedom from pyrogens are not the same property — which is why water quality in steam sterilisers and the use of properly prepared irrigation fluids both matter.

Standard Precautions

Standard precautions apply to every patient because infection status is often unknown.