Insights from 30 years of Salmonella proficiency testing
This whitepaper examines long-term trends across this dataset, presents a detailed atypical-strain case study, and compares AXIO PT findings with other major international PT programmes. We highlight recurring challenges such as atypical phenotypes, matrix-linked recovery issues and low-level contamination. We also show how analyst-level review over multiple PT rounds using AXIO’s PORTAL platform supports root-cause investigation, corrective actions and ongoing competency. Together, these insights demonstrate the central role of Salmonella PT in benchmarking capability, supporting accreditation and strengthening laboratory performance. Testing has distributed more than 200,000 Salmonella proficiency testing (PT) samples to laboratories in more than 160 countries, creating one of the world’s most extensive datasets on laboratory performance. With non-typhoidal Salmonella (NTS) causing nearly 100 million illnesses and more than 150,000 deaths each year worldwide , reliable detection across diverse food matrices remains essential for public health. Over three decades, LGC AXIO Proficiency
Introduction
The World Health Organisation estimates that unsafe food causes 600 million illnesses and 420,000 deaths each year , with surveillance data from the United States (US) and European Union (EU) consistently placing Salmonella among the leading causes of hospitalisation and economic loss. These figures underscore the need for robust detection across different foods and testing environments. Salmonella is taxonomically diverse, comprising two species, S. enterica and S. bongori. S. enterica contains six subspecies, with S. enterica subsp. enterica alone accounting for more than 1,500 serovars . NTS is acquired primarily from contaminated foods such as eggs, dairy, meat products and other fresh produce. Illness usually presents as gastroenteritis , although invasive disease occurs in around 5% of cases, particularly in young children, older adults and immunocompromised people . Outbreak investigations increasingly show that illness can follow ingestion of very low numbers of cells – sometimes as few as 10–100 cells – especially in high-fat, low-moisture foods that protect cells against gastric acid. These findings emphasise the need to assess laboratory detection capability across diverse matrices and physiological states, including low-level and stressed cells. Reliable detection depends not only on robust analytical methods but also on regular, objective assessment of laboratory performance. PT provides this independent check, evaluating end-to-end workflow capability under controlled but realistic challenge conditions. Because PT samples may include atypical phenotypes, low inoculum levels and matrix-linked recovery challenges, they can reveal vulnerabilities not captured by routine quality control. This whitepaper examines performance trends from three decades of AXIO PT data, and places them in context with findings from other major PT programmes. We highlight recurring drivers of poor detection and outline practical steps laboratories can take to strengthen Salmonella workflows.
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