6.15 - Hospital infections and antibiotic stewardship
Hospitals bring together people who are vulnerable to infection, frequent care contacts and intensive antibiotic use. In 6.15, we connect these contributory causes to antibiotic prescribing and hospital practices that prevent infection. Understanding the reason for each practice helps explain why several measures must work together.
Why hospital infections occur
A hospital infection can arise when an infectious agent reaches a susceptible patient and overcomes their defences.
Hospital-acquired infection
An infection acquired during hospital care, rather than one already present or incubating when the patient entered hospital. It may become apparent during the stay or after discharge.
Finding an infection in hospital does not, by itself, prove that it was acquired there. Staff need information about its onset, previous care and possible sources. Colonisation means carrying microorganisms at a body site without disease caused by them; a colonised person can still be a source of transmission.
There are two possible sources of an infecting organism. It may arrive from another person or the environment, or it may come from the patient's own resident microorganisms. For example, skin bacteria that cause no problem on intact skin can cause infection if introduced into a surgical wound. Preventing person-to-person spread therefore addresses only part of the risk.
| Hospital circumstance | Biological reason for increased risk |
|---|---|
| Some patients have impaired immune responses because of illness or treatment | Microorganisms that would otherwise be controlled may survive and multiply. Vulnerability varies between patients. |
| Surgery, wounds and invasive devices breach protective surfaces | Organisms can gain access to tissues or blood without crossing an intact skin barrier. A urinary catheter can provide a route into the urinary tract. |
| Many patients, staff and visitors have repeated contacts | Hands and shared items can link a source of microorganisms to several susceptible people. |
| A long stay involves repeated exposure and procedures | There are more opportunities for transmission or entry; a long stay does not make infection inevitable. |
MRSA is meticillin-resistant Staphylococcus aureus. It can be carried without disease, but can cause wound or bloodstream infections, especially when barriers or defences are compromised. Resistance concerns the bacterium's response to particular antibiotics; it does not mean that the patient's body has become resistant or that the organism resists every antibiotic. The NHS explanation of MRSA connects these risks to wounds, devices, impaired immunity and hospital stays.
Antibiotics change microbial communities
Antibiotics can benefit an infected patient while also changing which bacteria survive in their microbial communities.
Selection pressure
An environmental condition that changes the relative survival and reproductive success of organisms with different inherited characteristics.
Resistance can arise through genetic variation, including mutation or acquisition of resistance genes. An antibiotic does not deliberately teach bacteria to resist it. If a population contains bacteria resistant to that antibiotic, susceptible bacteria may be killed or have their growth inhibited more strongly. Resistant survivors then make a larger contribution to subsequent generations, increasing the proportion carrying resistance. This is selection acting on variation, as described in WHO's account of resistance selection.
Unnecessary antibiotic exposure creates selection pressure without a corresponding treatment benefit. Intensive use across a hospital can favour resistant populations, which can then spread through care contacts. Selection changes the composition of a bacterial population; transmission moves organisms between sources and people. One can happen without the other: a resistant organism can be transmitted to a person who has not taken that antibiotic.
There is a second effect. Broad-spectrum antibiotics act against a relatively wide range of bacteria and can disturb the normal gut microbiota, the community of microorganisms living there. Resident microorganisms normally compete with potential pathogens for resources and attachment sites. Reducing this protection can allow Clostridioides difficile already present or newly acquired to multiply. Toxin-producing strains can then damage the gut and cause diarrhoea. This is an ecological change as well as an infection risk; it is not explained simply by calling every C. difficile infection antibiotic-resistant.
C. difficile forms spores that can persist in the environment and be transferred to the mouth on contaminated hands or items. Thus appropriate prescribing reduces one source of susceptibility, while infection-control practices reduce exposure. The UKHSA technical report explains this link between antibiotic disturbance, spores and disease.
Prescribing with evidence and review
Appropriate prescribing balances effective care of the patient with avoiding unnecessary antimicrobial exposure.
Antimicrobial stewardship
Coordinated action to use antimicrobial medicines appropriately, preserving their effectiveness while providing effective and safe care.
Antibiotic stewardship is the part concerned with antibacterial medicines. Antibiotics do not treat viruses themselves; a bacterial infection alongside a viral infection is a separate clinical question. Prescribing decisions require professional assessment rather than an assumption that any fever needs an antibiotic.
In England, the Health and Social Care Act 2008 infection-control code of practice, updated in 2022, links infection prevention, cleanliness and appropriate antimicrobial use. Its guidance includes local stewardship policies informed by national guidance and local resistance patterns. The code provides a framework for meeting regulatory requirements; it is not a claim that every hospital follows one identical prescription rule throughout the UK.
UKHSA's Start smart then focus inpatient toolkit, updated in 2023 provides a current English example. Clinicians assess the likely infection, use relevant diagnostic evidence and local guidance, record the reason for prescribing and specify a duration or review date. Diagnostic sampling should not delay urgent treatment where delay would endanger the patient. The toolkit describes review usually at 48–72 hours, with earlier review when circumstances require it. New evidence can support stopping, changing, narrowing or continuing treatment with a documented plan.
The documentation and evidence-led review principles also appear in NICE's antimicrobial stewardship recommendations. The biological reasoning matters more here than memorising a clinical timetable:
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