A point prevalence study to determine the inpatient rate of carbapenemase-producing organisms at a large London NHS Trust

Background There has been an increase in the number of carbapenemase-producing organisms documented across the UK over the past 10 years. From these, the ‘big five’ carbapenemases (KPC, OXA-48, IMP, VIM, and NDM) are the most common types reported in the order Enterobacterales, identified from a variety of reactive screening, outbreak, inpatient surveillance, and diagnostic samples. Aim To perform a point prevalence study to determine the inpatient carriage rate of carbapenemase-producing organisms at Barts Health NHS Trust, which encompasses 2.5 million patients across four London boroughs: Tower Hamlets, Newham, Redbridge, and Waltham Forest. Methods Rectal swabs were collected from consenting inpatients, alongside details of the ward's medical specialty, patient's country of birth, history of foreign travel, length of hospitalization, and history of prior hospitalization. Swabs were enriched and subcultured on to mSuperCARBA selective medium. All Enterobacterales, Acinetobacter, and Pseudomonas species were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy and underwent antibiotic susceptibility testing by disc diffusion, according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. All isolates were screened for the ‘big five’ carbapenemases using a modified version of a published reverse transcriptase–polymerase chain reaction assay. Findings Of the 977 inpatients tested, 35 CPOs were isolated from 30 patients. NDM was the most frequently detected carbapenemase, followed by OXA-48, with an overall prevalence of 3.1%. Organisms isolated included Klebsiella pneumoniae, Enterobacter cloacae, Proteus mirabilis, and Escherichia coli. Renal and elderly care patients had the highest prevalences of CPOs, whereas the intensive care unit prevalence was low. Statistical analysis found that hospitalization abroad, any previous hospitalization, foreign travel and, specifically, travel to India, Pakistan, and Bangladesh were associated with increased risk of CPO carriage. Conclusion The overall prevalence of CPOs at Barts Health Trust was 3.1%, comprising NDM and OXA-48-type carbapenemases, which is in line with other London-based studies. Renal patients and the elderly had the highest burden of CPOs, whereas previous hospitalization and foreign travel were associated with an increased risk of CPO carriage.