Keeping antibiotic resistance at bay: Hospital-based surveillance of antibiotic-resistant Gram-negative bacteria

The human body is colonised with millions of bacteria, which are usually innocent. These bacteria can also become invasive and cause infections, prompting antibiotic treatment. Bacteria can become resistant to certain or multiple types of antibiotics and can exchange these resistance traits by horizontal transmission of plasmids. An important tool to monitor and control antibiotic resistance is surveillance. This consists of ongoing systematic collection, analysis and interpretation of health data. Surveillance can track temporal changes in bacterial populations, allows the early detection of relevant antibiotic-resistant strains and supports timely notification of outbreaks. Furthermore, these data can be used for the development, evaluation, and optimisation of infection prevention and control strategies. Surveillance from the hospital perspective is of particular importance because the hospital is an important reservoir for multidrug-resistant organisms (MDRO). In this thesis, a collection of projects was carried out that focused on hospital-based surveillance. With this research, we aim to contribute to keeping antibiotic resistance at bay in the Netherlands. The most important findings of this thesis are: (1) Selective digestive decontamination (SDD) is a cost-effective preventive regimen to improve the survival of Dutch intensive care unit (ICU) patients, (2) The addition of a selective medium in the laboratory could improve the detection of carriage with colistin-resistant Gram-negative bacteria in ICU-patients receiving SDD, although prevalence of colistin resistance in this population is low, (3) The current screening for carriage of MDRO upon hospital admission appears to be relatively resource intensive compared to the estimated gain in detection of carriage, and could therefore be reconsidered, (4) The molecular characteristics of bacteraemic E. coli bacteria that are positive for extended-spectrum beta-lactamase (ESBL) - an enzyme that can break down certain antibiotics - are different from bacteraemic E. coli bacteria that do not carry an ESBL, and (5) First results suggest a potential role for routine clinical samples in future molecular epidemiology surveillance of ESBL-positive E. coli carriage in the Netherlands.