In a busy emergency department at Manchester Royal Infirmary, a patient arrives with fever, confusion, and rapid breathing. The sepsis protocol kicks in: a lactate measurement, broad-spectrum antibiotics within the hour, a fluid bolus. The checklist is nearly complete. But one step is often skipped: drawing blood cultures before the antibiotics go in. Across the UK, this pattern repeats thousands of times a day, and the consequences are not trivial.

Blood cultures are the gold standard for identifying the bacteria causing sepsis and for guiding antibiotic de-escalation. Yet in many NHS emergency departments, culture collection rates hover below 50%, even as compliance with the Sepsis Six checklist—which includes taking blood cultures—approaches 90%. The result: patients receive broad-spectrum antibiotics that may be unnecessarily powerful, fueling antibiotic resistance, and clinicians lose the chance to tailor treatment to the specific pathogen.

This is a story about a clinical practice gap—one that exists not because of lack of evidence, but because of how that evidence collides with the realities of overcrowded emergency departments, constrained laboratory capacity, and human behaviour. It is also a story about what happens when a checklist becomes a box-ticking exercise rather than a diagnostic tool.

A Checklist for Sepsis, but No Blood Cultures

The Sepsis Six—a bundle of six interventions including oxygen, blood cultures, antibiotics, fluids, lactate measurement, and urine output monitoring—has been a cornerstone of NHS sepsis care since its introduction in the early 2010s. Studies have shown that completing the bundle within one hour reduces mortality by roughly 30% in patients with septic shock. But the devil is in the details: the checklist mandates hourly lactate checks and antibiotic administration, but the blood culture step is often treated as optional.

Data from the National Emergency Laparotomy Audit and other sources suggest that in some emergency departments, blood culture collection rates are as low as 30–40% of eligible sepsis patients. A 2022 audit of St Thomas' Hospital in London found that while 90% of patients received antibiotics within one hour, only 45% had blood cultures drawn before the first dose. This is not an isolated finding: several regional audits report similar figures.

Why does this matter? Blood cultures are the only way to confirm the causative organism and its antibiotic susceptibility. Without them, clinicians cannot de-escalate from broad-spectrum agents like piperacillin-tazobactam to narrower, more targeted drugs such as benzylpenicillin or cefuroxime. This overuse of broad-spectrum antibiotics is a well-documented driver of antimicrobial resistance, which already claims roughly 5,000 lives annually in the UK.

Checklist compliance is high, but diagnostic yield is low. The Sepsis Six was designed for speed, not for diagnostic stewardship. And in the rush to meet the one-hour antibiotic target, the blood culture step—which can take a few extra minutes—is often sacrificed.

Why Clinicians Skip the Bottles

Time pressure is the most frequently cited reason. Emergency departments across the UK are chronically overcrowded, with many reporting that patients wait hours in corridors before being seen. In such an environment, every minute counts, and drawing blood cultures—which requires sterile technique, a second venipuncture in many cases, and proper labelling—can feel like a luxury.

There is also a perception that blood cultures have low yield in patients who have already received antibiotics. Once antibiotics are started, the chance of isolating a pathogen drops significantly, sometimes to below 10%. Some clinicians reason, wrongly, that if they are going to give antibiotics anyway, the culture result will not change management. But that logic ignores the value of knowing the susceptibility profile for de-escalation later, especially if the patient does not improve.

Another barrier is the lack of feedback. In many trusts, culture results take 48 to 72 hours to become available, and by then the patient may have been discharged or transferred to a ward. Front-line staff rarely see the results, so they do not learn from the cases where a culture identified a resistant organism that required a change in therapy. This feedback loop is broken.

Training also plays a role. Aseptic technique for blood culture collection is not consistently taught in medical schools or nursing programmes. Contamination rates—where skin flora grow in the bottle, leading to false positives—can be as high as 30% in some departments. This creates a distrust of culture results, further discouraging collection.

The Evidence Gap: Cultures Reduce Mortality

A 2023 study in The Lancet Infectious Diseases examined the impact of blood culture-guided therapy on mortality in patients with sepsis across several European hospitals, including sites in the UK, Germany, France, and Sweden. The researchers found that patients who had blood cultures drawn before antibiotics had a 30-day mortality rate of roughly 16%, compared with 21% among those who did not—a relative reduction of about 25%. The effect was strongest in patients with resistant infections, where targeted therapy reduced mortality by nearly half.

Sepsis mortality in UK emergency departments remains stubbornly high, at around 15–20% in recent estimates. At the same time, resistance rates for common pathogens like Escherichia coli and Klebsiella pneumoniae are rising. Data from Public Health England (now the UK Health Security Agency) show that the proportion of E. coli bloodstream infections resistant to third-generation cephalosporins increased from roughly 8% in 2014 to 12% in 2023. For Klebsiella, resistance to carbapenems—last-resort antibiotics—has more than doubled over the same period.

Blood cultures enable targeted narrow-spectrum antibiotics, which are less likely to drive resistance. A 2021 systematic review in Clinical Microbiology and Infection found that de-escalation based on culture results was associated with a lower risk of subsequent resistant infections and no increase in mortality. Yet the practice remains underutilised.

The evidence is clear: cultures save lives and slow resistance. But the gap between evidence and practice persists.

System-Level Barriers to Culturing

Beyond individual clinician behaviour, system-level factors discourage culturing. Blood culture bottle shortages have been reported in several NHS trusts in 2025 and 2026, including University Hospitals of Leicester NHS Trust and Nottingham University Hospitals NHS Trust, particularly during winter pressure periods. In some cases, trusts have rationed bottles, asking clinicians to culture only patients with septic shock or other high-risk features. This creates a perverse incentive: when bottles are scarce, teams hoard them for the sickest patients, but those are precisely the patients who need cultures most.

Laboratory turnaround times also limit clinical utility. In many NHS hospitals, results take 48 to 72 hours, which is too slow to guide initial therapy and sometimes too slow to affect the patient's stay if they are discharged early. Rapid molecular tests, such as the BioFire FilmArray, can identify pathogens and resistance genes in about one hour, but they are expensive—roughly £100 per test—and not routinely available in most emergency departments.

Electronic health records (EHRs) are another missed opportunity. Many EHRs do not flag missing blood cultures in real time. A clinician can complete the sepsis order set without ever being prompted to order cultures. Some systems have optional culture order fields, but they are not mandatory. In contrast, some US hospitals have implemented "hard stops" that require a culture order before antibiotics can be administered, a strategy that has doubled culture collection rates in some settings.

Financial disincentives also play a role. Under the current NHS payment model, the cost of blood culture bottles and laboratory processing is borne by the trust, with no separate reimbursement per patient. A single blood culture set (two bottles) costs roughly £20–30, and when multiplied across thousands of patients, the expense is not trivial. In a system under financial pressure, cutting costs can mean cutting cultures.

Where Checklists Work and Where They Don't

The Sepsis Six checklist has undoubtedly improved door-to-antibiotic times. A 2019 study in the BMJ Quality & Safety found that its introduction reduced median time to antibiotics from 120 minutes to 60 minutes in participating UK emergency departments. That is a clear win. But the same study found no significant change in blood culture collection rates.

Checklists are designed for speed and reliability, not for nuanced diagnostic decision-making. The Sepsis Six bundles six actions into one protocol, but it does not differentiate between the actions that are time-critical (antibiotics, fluids) and those that are diagnostic (cultures). In practice, the time-critical actions get done, and the diagnostic ones slip.

Some emergency departments in Wales and Scotland have trialled separate "culture bundles" that require a phlebotomist to draw cultures before the sepsis nurse starts the antibiotic. For example, the University Hospital of Wales in Cardiff and the Royal Infirmary of Edinburgh have implemented such programmes, with culture rates rising above 70%. But they require additional staffing and training, which not all trusts can afford.

The tension between speed and stewardship is real. A 2022 commentary in Emergency Medicine Journal argued that the one-hour antibiotic target may inadvertently harm patients if it leads to indiscriminate antibiotic use without cultures. The authors called for a "diagnostic pause" of a few minutes to allow culture collection before antibiotics, even in septic shock. This remains controversial, as some clinicians, such as those interviewed in a 2023 survey by the UK Sepsis Trust, fear any delay in antibiotics could be fatal.

Lessons from High-Performing Sites

Not all UK emergency departments struggle with cultures. Some hospitals have achieved collection rates above 80% by implementing dedicated sepsis phlebotomy teams. At St George's Hospital in London, a quality improvement project introduced a "sepsis phlebotomist" role—a healthcare assistant trained specifically to draw blood cultures—who responds to sepsis alerts. Within six months, culture collection rates rose from 45% to 85%, and contamination rates fell.

Real-time audit feedback is another effective strategy. At the Royal Liverpool University Hospital, a dashboard that shows each clinician's culture collection rates, updated daily, led to a sustained increase from 50% to 75% over one year. The dashboard also highlighted cases where cultures grew resistant organisms, providing a learning opportunity.

Electronic order sets that require a culture order before antibiotics can be administered—a "hard stop"—have been piloted in a few trusts, including University College London Hospitals NHS Foundation Trust and Sheffield Teaching Hospitals NHS Foundation Trust. Early results suggest culture collection rates can exceed 90% with such systems, though there are concerns about delays in antibiotic administration if the order set is not well designed. A balanced approach might be a "soft stop" that alerts the clinician if no culture is ordered but allows them to proceed if they document a reason.

Multidisciplinary rounds that include microbiology input also help. At the Oxford University Hospitals NHS Foundation Trust, a weekly sepsis review meeting brings together emergency physicians, microbiologists, and pharmacists to discuss culture results and antibiotic choices for every sepsis patient admitted in the previous week. This feedback loop has improved culture collection rates and antibiotic stewardship over time.

Closing the Loop: From Bottle to Bedside

Rapid molecular diagnostics offer a way to close the time gap between culture collection and actionable results. The BioFire FilmArray Blood Culture Identification panel, approved for use in the UK, can identify roughly 90% of bloodstream pathogens and associated resistance genes in about an hour, directly from positive blood cultures. Some hospitals are now using it to guide therapy within the same shift. The cost remains a barrier, but as the technology matures, prices are expected to fall.

The UK National Institute for Health and Care Excellence (NICE) is expected to issue updated guidance on sepsis diagnostics in 2026, which may recommend broader use of rapid tests. In the meantime, some trusts are investing in their own solutions. At University Hospitals Birmingham NHS Foundation Trust, a pilot programme uses matrix-assisted laser desorption/ionisation–time of flight (MALDI-TOF) mass spectrometry to identify organisms from positive cultures within 30 minutes, at a cost of roughly £5 per sample.

Training programmes on the interpretation of culture results for nurses and junior doctors are also being developed. The UK Sepsis Trust has launched an online module on blood culture stewardship, covering when to culture, how to collect properly, and how to use results to de-escalate antibiotics. Early uptake has been modest, but the trust hopes to integrate the module into mandatory sepsis training.

Patient-facing summaries that explain culture-guided treatment are another innovation. At the Norfolk and Norwich University Hospital, patients discharged after sepsis receive a written summary that includes the organism identified (if any) and the antibiotics used, along with a plain-English explanation of why cultures matter. This helps patients understand their treatment and may encourage them to ask about cultures in future encounters.

The gap between checklist completion and culture collection is not inevitable. It is a product of system design, training, and culture. Closing it will require not just better checklists, but a rethinking of how we value diagnostic information in the rush to treat. For now, the bottles sit unused in too many departments, and the evidence sits unapplied.

This article is for informational purposes only and does not constitute medical advice. Individual patient care decisions should be made in consultation with a qualified healthcare professional.