Implications of ad-hoc molecular typing for infection control measures in a multi-cluster, multi-phenotypic Serratia marcescens outbreak in a neonatal intensive care unit.

BACKGROUND: Serratia marcescens is known to cause outbreaks in neonatal intensive care units (NICUs). Traditionally epidemiological data, antimicrobial resistance patterns and epidemiological typing have been used to guide infection prevention methods. Whole-genome sequencing (WGS) applications such as core-genome multi-locus sequence typing (cgMLST) applied during an outbreak would potentially yield more information. AIM: To use cgMLST to acquire detailed information on the source and spread of bacteria, enabling more efficient control measures during an S. marcescens outbreak at a NICU. METHODS: Neonates admitted to the NICU of the Leiden University Medical Center (LUMC) during an outbreak between September 2023 and January 2024, with S. marcescens being cultured, were included. Environmental samples were taken to search for a common source, antibiotic susceptibility testing was performed, and antimicrobial resistance genes were analysed. FINDINGS: S. marcescens strains from 17 of the 20 positive patients were available for molecular typing. The cgMLST scheme revealed five different complex types consisting of four separate clusters. Multiple clusters made an unidentified persistent environmental source as cause of the outbreak less likely, leading to a quick downscaling of infection prevention measures. Differences were shown in aminoglycoside resistance patterns of isolates within the same complex types and patients. CONCLUSION: The use of ad-hoc cgMLST provided timely data for rational decision-making during an S. marcescens outbreak at the NICU. Antibiotic phenotyping alone was found not to be suitable for studying clonal spread during this outbreak with S. marcescens.

Effects of a disinfection device on colonization of sink drains and patients during a prolonged outbreak of multidrug-resistant Pseudomonas aeruginosa in an intensive care unit.

BACKGROUND: Sink drains in intensive care units (ICUs) are frequently colonized with bacteria such as Pseudomonas aeruginosa. AIM: To study the influence of installing disinfecting devices on sink drains on colonization of sinks and patients in an ICU during a prolonged outbreak of multidrug-resistant P. aeruginosa. METHODS: From 2010, there was a clonal outbreak of multidrug-resistant P. aeruginosa (MDR-PA). In April 2013, in ICU subunit A, the siphons draining these sinks were replaced by devices applying heat and electromechanical vibration to disinfect the draining fluid. In the other units, siphons were replaced by new polyvinyl chloride plastic siphons (control). In February 2016 the disinfecting devices were also placed at ICU subunit B. FINDINGS: Baseline colonization rate of sinks was 51% in ICU A and 46% in ICU B. In ICU A colonization decreased to 5% (P < 0.001) after the intervention whereas it was 62% in ICU B (control). After installing the disinfection devices in ICU B, colonization rate was 8.0 and 2.4% in ICU A and B, respectively (both P < 0.001 compared with baseline). Colonization in ICU patients decreased from 8.3 to 0 per 1000 admitted patients (P < 0.001) and from 2.7 to 0.5 per 1000 admitted patients (P = 0.1) in ICU A and B respectively. CONCLUSION: Colonization with MDR-PA in sink drains in an ICU was effectively managed by installing disinfection devices to the siphons of sinks. Colonization of patients was also significantly reduced, suggesting that sink drains can be a source of clinical outbreaks with P. aeruginosa and that disinfecting devices may help to interrupt these outbreaks.

Lactoferrin Glu561Asp polymorphism is associated with susceptibility to herpes simplex keratitis.

Lactoferrin plays an important role in the defense against infections, including herpes simplex virus (HSV) keratitis. We studied the impact of three single nucleotide polymorphisms in the human lactoferrin gene on the susceptibility to HSV infections of the eye and the severity of such infections. Lactoferrin gene polymorphisms were determined by PCR combined with restriction fragment length analysis in 105 HSV keratitis patients and 145 control subjects. Bilateral tear samples were harvested from 50 patients and 40 healthy controls and tear lactoferrin concentrations were determined by ELISA. Patients' records were used to acquire information about the severity of the HSV keratitis. The frequencies of the Glu561Asp polymorphism, but not those of the Ala11Thr and Lys29Arg polymorphisms, differed significantly between patients and control subjects with an under-representation of the Asp561 allele in the patient group. Furthermore, the values for best corrected visual acuity, frequency of recurrences since onset, and average duration of clinical episodes did not differ among patients with various lactoferrin genotypes. In addition, tear lactoferrin concentrations were the same in patients with HSV keratitis and healthy controls and also did not differ among patients with various lactoferrin genotypes. Lactoferrin Glu561Asp polymorphism is associated with the susceptibility to HSV keratitis with a protective role for lactoferrin variants comprising Asp561. However, no beneficial effects of this lactoferrin variant on the clinical outcome of ocular HSV keratitis were noted.