To screen or not to screen medical students for carriage of multidrug-resistant pathogens?

BACKGROUND: The carriage of multidrug-resistant (MDR) pathogens in medical students has not been studied extensively, despite the fact that they are in contact with patients and exposed to a hospital environment. AIM: To investigate the intestinal and nasal carriage of MDR pathogens among medical students and its association with their lifestyle and demographic data. METHODS: In 2021, first- and final-year medical students were invited to the study. Two rectal swabs were used for detection of extended-spectrum ß-lactamase (ESBL)-producing, colistin-, tigecycline- or carbapenem-resistant Gram-negative bacteria and vancomycin-resistant enterococci. Nasal swab was used for Staphylococcus aureus culture. S. aureus isolates were characterized by spa typing; Gram-negative resistant isolates and meticillin-resistant S. aureus (MRSA) were subjected to whole-genome short and/or long sequencing. FINDINGS: From 178 students, 80 (44.9%) showed nasal carriage of S. aureus; two isolates were MRSA. In rectal swabs, seven ESBL-producing strains were detected. Sixteen students were colonized by colistin-resistant bacteria, three isolates carried the mcr-1 gene (1.7%). The mcr-9 (10.7%, 19/178) and mcr-10 (2.2%, 4/178) genes were detected by quantitative polymerase chain reaction, but only two colistin-susceptible mcr-10-positive isolates were cultured. The S. aureus nasal carriage was negatively associated with antibiotic and probiotic consumption. S. aureus and colistin-resistant bacteria were detected more frequently among students in contact with livestock. CONCLUSION: Medical students can be colonized by (multi)drug-resistant bacteria with no difference between first- and final-year students. The participation of students in self-screening increases their awareness of possible colonization by resistant strains and their potential transmission due to poor hand hygiene.

An emerging Panton-Valentine leukocidin-positive CC5-meticillin-resistant Staphylococcus aureus-IVc clone recovered from hospital and community settings over a 17-year period from 12 countries investigated by whole-genome sequencing.

BACKGROUND: A novel Panton-Valentine leukocidin (PVL)-positive meticillin-resistant Staphylococcus aureus (MRSA) clonal complex (CC)5-MRSA-IVc ('Sri Lankan' clone) was recently described from Sri Lanka. Similar isolates caused a recent Irish hospital outbreak. AIM: To investigate the international dissemination and diversity of PVL-positive CC5-MRSA-IVc isolates from hospital and community settings using whole-genome sequencing (WGS). METHODS: Core-genome single nucleotide polymorphism (cgSNP) analysis, core-genome multi-locus sequence typing (cgMLST) and microarray-based detection of antimicrobial-resistance and virulence genes were used to investigate PVL-positive CC5-MRSA-IVc (N = 214 including 46 'Sri Lankan' clone) from hospital and community settings in 12 countries over 17 years. Comparators included 29 PVL-positive and 23 PVL-negative CC5/ST5-MRSA-I/II/IVa/IVc/IVg/V. RESULTS: Maximum-likelihood cgSNP analysis grouped 209/214 (97.7%) CC5-MRSA-IVc into Clade I; average of 110 cgSNPs between isolates. Clade III contained the five remaining CC5-MRSA-IVc; average of 92 cgSNPs between isolates. Clade II contained seven PVL-positive CC5-MRSA-IVa comparators, whereas the remaining 45 comparators formed an outlier group. Minimum-spanning cgMLST analysis revealed a comparably low average of 57 allelic differences between all CC5/ST5-MRSA-IVc. All 214 CC5/ST5-MRSA-IVc were identified as 'Sri Lankan' clone, predominantly spa type t002 (186/214) with low population diversity and harboured a similar range of virulence genes and variable antimicrobial-resistance genes. All 214 Sri Lankan clone isolates and Clade II comparators harboured a 9616-bp chromosomal PVL-encoding phage remnant, suggesting both arose from a PVL-positive meticillin-susceptible ancestor. Over half of Sri Lankan clone isolates were from infections (142/214), and where detailed metadata were available (168/214), most were community associated (85/168). CONCLUSIONS: Stable chromosomal retention of pvl may facilitate Sri-Lankan clone dissemination.

The use of broad-range bacterial PCR in the diagnosis of infectious diseases: a prospective cohort study.

OBJECTIVES: Broad-range PCR has the potential to detect virtually any bacterial species via amplification and nucleotide sequencing of a DNA region common to all bacteria. We aimed to evaluate its usefulness and clinical relevance when applied to a wide variety of primary sterile materials. METHODS: A prospective study including 1370 samples (75 heart valves, 151 joint tissue samples, 230 joint aspirates, 848 whole blood samples and 66 culture-negative cerebrospinal fluid samples) were studied by using a commercial PCR system for detecting 16S rDNA (Molzym). The PCR results were compared with culture and were considered to provide added diagnostic value only if the PCR approach revealed new pathogens that were missed by culture. RESULTS: The added value of PCR was evident in 173 of 555 PCR-positive samples (0.126; 0.109-0.144 (proportion from all tested samples; 95% confidence interval)), most frequently in examinations of heart valves (0.56; 0.448-0.672) and joint tissue samples (0.219; 0.153-0.284). In contrast, the lowest rate of PCR with added value was noted for blood samples, regardless of the patient cohort they had been drawn from (nononcologic patients from intensive care: 0.065; 0.043-0.087, haematooncologic children: 0.048; 0.027-0.070). Moreover, PCR missed up to 7.1% of blood culture findings (0.071; 0.048-0.095) regarded as clinically relevant, which was the second highest failure rate after joint tissue samples (0.099; 0.052-0.147). CONCLUSIONS: Broad-range PCR substantially increases detection rate of pathogens, especially from heart valves and joint samples. However, a concurrent risk of false-negative PCR results justifies the need for parallel culture.

[Small colony variants Staphylococcus aureus]. / Trpaslicí kmeny--small colony variants Staphylococcus aureus.

The phenomenon of dwarf colonies of S. aureus, the so-called small colony variants (SCVs), is associated with chronic and recurrent staphylococcal infections. Most frequently, these phenotypic variants differ from normal strains of S. aureus in colony size, morphology, pigmentation and other characteristics as well as molecular genetic changes. SCVs frequently emerge as a result of mutations in metabolically important and regulatory genes. The mutations are a cause of SCVs auxotrophy. From a clinical point of view, an increased ability of SCVs to resist antibiotic therapy and also an ability to persist within eukaryotic host cells are of importance.