Screening for Gram-negative bacteria: Impact of preanalytical parameters

Multidrug-resistant organisms in paediatric palliative care patients - Prevalence, risk factors and the impact of a liberal hygiene concept

AIM

Multidrug-resistant organisms (MDRO) deserve special attention in health-care facilities for children with life-limiting conditions because these children have an increased risk for colonisation. To avoid nosocomial transmissions to other inpatients, single-room isolation is usually recommended. In the context of paediatric palliative care (PPC), such isolation counters the aim of participation in social activities for the patients. This study aimed to determine the prevalence of MDRO, the predictive value of risk factors and the incidence of nosocomial infections and nosocomial colonisations on a PPC inpatient unit applying a special hygiene concept that enables participation in social activities through risk-adaption and barrier nursing.

METHODS

Two-year surveillance with MDRO screening of all intakes (N = 386) of a PPC unit on the day of admission and discharge. To determine the predictive value of pre-defined risk factors, logistic regression analyses were calculated. Receiver operating characteristic analyses were performed to determine the predictive power of the number of risk factors on the presence of MDRO.

RESULTS

The rate of MDRO colonisation at admission was 12.7%; previous positive MDRO screening was the only significant individual risk factor. Over the 2-year period, no MDRO-related nosocomial infections occurred; nosocomial colonisation incidence density was 0.6.

CONCLUSION

Results demonstrate that patients with at least one risk factor have to be cared for by barrier nursing until MDRO screening results are negative. Following these guidelines prevents nosocomial MDRO transmission.

Detection of Multidrug-Resistant Enterobacterales-From ESBLs to Carbapenemases

Multidrug-resistant Enterobacterales (MDRE) are an emerging threat to global health, leading to rising health care costs, morbidity and mortality. Multidrug-resistance is commonly caused by different β-lactamases (e.g., ESBLs and carbapenemases), sometimes in combination with other resistance mechanisms (e.g., porin loss, efflux). The continuous spread of MDRE among patients in hospital settings and the healthy population require adjustments in healthcare management and routine diagnostics. Rapid and reliable detection of MDRE infections as well as gastrointestinal colonization is key to guide therapy and infection control measures. However, proper implementation of these strategies requires diagnostic methods with short time-to-result, high sensitivity and specificity. Therefore, research on new techniques and improvement of already established protocols is inevitable. In this review, current methods for detection of MDRE are summarized with focus on culture based and molecular techniques, which are useful for the clinical microbiology laboratory.

Comprehensive integrated NGS-based surveillance and contact-network modeling unravels transmission dynamics of vancomycin-resistant enterococci in a high-risk population within a tertiary care hospital

Vancomycin-resistant E. faecium (VRE) are an important cause of nosocomial infections, which are rapidly transmitted in hospitals. To identify possible transmission routes, we applied combined genomics and contact-network modeling to retrospectively evaluate routine VRE screening data generated by the infection control program of a hemato-oncology unit. Over 1 year, a total of 111 VRE isolates from 111 patients were collected by anal swabs in a tertiary care hospital in Southern Germany. All isolated VRE were whole-genome sequenced, followed by different in-depth bioinformatics analyses including genotyping and determination of phylogenetic relations, aiming to evaluate a standardized workflow. Patient movement data were used to overlay sequencing data to infer transmission events and strain dynamics over time. A predominant clone harboring vanB and exhibiting genotype ST117/CT469 (n = 67) was identified. Our comprehensive combined analyses suggested intra-hospital spread, especially of clone ST117/CT469, despite of extensive screening, single room placement, and contact isolation. A new interactive tool to visualize these complex data was designed. Furthermore, a patient-contact network-modeling approach was developed, which indicates both the periodic import of the clone into the hospital and its spread within the hospital due to patient movements. The analyzed spread of VRE was most likely due to placement of patients in the same room prior to positivity of screening. We successfully demonstrated the added value for this combined strategy to extract well-founded knowledge from interdisciplinary data sources. The combination of patient-contact modeling and high-resolution typing unraveled the transmission dynamics within the hospital department and, additionally, a constant VRE influx over time.

On detection thresholds-a review on diagnostic approaches in the infectious disease laboratory and the interpretation of their results

Diagnostic testing in the infectious disease laboratory facilitates decision-making by physicians at the bedside as well as epidemiological assessments and surveillance at study level. Problems may arise if test results are uncritically considered as being the same as the unknown true value. To allow a better understanding, the influence of external factors on the interpretation of test results is introduced with the example of prevalence, followed by the presentation of strengths and weaknesses of important techniques in the infectious disease laboratory like microscopy, cultural diagnostics, serology, mass spectrometry, nucleic acid amplification and hypothesis-free metagenomic sequencing with focus on basic, high-technology and potential future approaches. Special problems like multiplex testing as well as uncertainty of test evaluations, if no gold standard is available, are also stressed with a final glimpse on emerging future technologies for the infectious disease laboratory. In the conclusions, suitability for point-of-care-testing and field laboratory applications is summarized. The aim is to illustrate the limitations of diagnostic accuracy to both clinicians and study planners and to stress the importance of close cooperation with experts in laboratory disciplines so as to avoid potentially critical misunderstandings due to inappropriate interpretation of diagnostic test results.

Assessment of a semi-automated enrichment system (Uroquattro HB&L) for detection of faecal carriers of ESBL-/AmpC-producing Enterobacterales

INTRODUCTION

Early detection of patients carrying multiresistant bacteria is an effective implement in surveillance programs. Our objective was to compare the semi-automatic Uroquattro HB&L "ESBL/AmpC Screening" (Alifax®) system with the routine culture on selective media to detect ESBL/pAmpC-producing microorganisms (3CGRE).

METHODS

A total of 201 rectal swabs samples were processed by inoculating them into the Uroquattro HB&L system, performing growth curve measurements at 6.5 and 10h, and into direct culture medium.

RESULTS

Thirty-five samples yielded 3CGRE. Measurements at 10h incremented the positive 3GCRE detection 5.7% in comparison with routine culture medium. In negative rectal swabs, the overall percent agreement at 6.5h and 10h versus routine culture medium was 93% and 90%, respectively.

CONCLUSIONS

The Uroquattro HB&L system increased the detection of ESBL/pAmpC-producing bacteria compared to direct plating with an incubation time of 10h and shortens the time to report a negative sample.

Diagnostic performance of the Xpert Carba-R assay for active surveillance of rectal carbapenemase-producing organisms in intensive care unit patients

Background

There are growing concerns regarding the spread of carbapenemase-producing organisms (CPOs) among patients in long-term care facilities (LTCFs) and hospitals in South Korea. We have established a screening protocol for the detection of CPOs in high-risk patients upon admission to intensive care units (ICUs). The diagnostic performance of the Xpert Carba-R assay was compared to that of rectal culture for CPO detection in high-risk patients upon ICU admission.

Methods

A total of 408 consecutive rectal swabs were obtained from December 2016 to December 2017. CPO screening was performed using the Xpert Carba-R assay (Cepheid, Sunnyvale, CA, USA). When a carbapenemase gene was detected, additional rectal swabs were incubated overnight and inoculated on chromID CARBA medium (bioMérieux, Marcy l’Etoile, France). Bacterial carbapenemase genes, including bla_KPC, bla_NDM, bla_VIM, bla_IMP-1, and bla_OXA-48, were confirmed by conventional PCR. The diagnostic performance of the Carba-R assay was ascertained based on the culture results.

Results

The prevalence of CPO carriage was 7.4% according to the Carba-R assay and 3.7% according to rectal culture. The median Ct values of IMP-1 and KPC were significantly different (35.2 vs. 26.6, P = 0.0143). The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the Carba-R assay were 100.0% (95% confidence interval [CI], 78.2–100.0), 96.7% (94.4–98.2), 53.6% (40.4–66.4) and 100.0% (99.0–100.0), respectively.

Conclusions

We demonstrated the prevalence of CPO carriage in high-risk patients upon ICU admission and evaluated the diagnostic performance of the Carba-R assay. The combined use of the Xpert Carba-R assay and culture produces rapid and reliable results for the active surveillance of rectal CPO in ICU patients.

One-year molecular surveillance of carbapenem-susceptible A. baumannii on a German intensive care unit: diversity or clonality

Background

A. baumannii is a common nosocomial pathogen known for its high transmission potential. A high rate of carbapenem-susceptible Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB)-complex in clinical specimens led to the implementation of a pathogen-based surveillance on a 32-bed surgical intensive care unit (SICU) in a German tertiary care centre.

Methods

Between April 2017 and March 2018, ACB-complex isolates with an epidemiological link to the SICU were further assessed. Identification to the species level was carried out using a multiplex PCR targeting the gyrB gene, followed by RAPD, PFGE (ApaI) and whole genome sequencing (WGS, core genome MLST, SeqSphere+ software, Ridom). Additional infection prevention and control (IPC) measures were introduced as follows: epidemiological investigations, hand hygiene training, additional terminal cleaning and disinfection incl. UV-light, screening for carbapenem-susceptible A. baumannii and environmental sampling. Hospital-acquired infections were classified according to the CDC definitions.

Results

Fourty four patients were colonized/infected with one or two (different) carbapenem-susceptible ACB-complex isolates. Fourty three out of 48 isolates were classified as hospital-acquired (detection on or after 3rd day of admission). Nearly all isolates were identified as A. baumannii, only four as A. pittii. Twelve patients developed A. baumannii infections. Genotyping revealed two pulsotype clusters, which were confirmed to be cgMLST clonal cluster type 1770 (n = 8 patients) and type 1769 (n = 12 patients) by WGS. All other isolates were distinct from each other. Nearly all transmission events of the two clonal clusters were confirmed by conventional epidemiology. Transmissions stopped after a period of several months. Environmental sampling revealed a relevant dissemination of A. baumannii, but only a few isolates corresponded to clinical strains. Introduction of the additional screening revealed a significantly earlier detection of carbapenem-susceptible A. baumannii during hospitalization.

Conclusions

A molecular and infection surveillance of ACB-complex based on identification to the species level, classic epidemiology and genotyping revealed simultaneously occurring independent transmission events and clusters of hospital-acquired A. baumannii. This underlines the importance of such an extensive surveillance methodology in IPC programmes also for carbapenem-susceptible A. baumannii.

Resistant Gram-Negative Bacteria and Diagnostic Point-of-Care Options for the Field Setting during Military Operations

The spread of multidrug-resistant bacteria in resource-poor settings affects the military medical service in case of deployments of soldiers to war and crisis zones. Patients with war injuries are prone to colonization or infection with multidrug-resistant bacteria. Resistant Gram-negative bacteria play a dominant role in military wound infections. Problematic hygiene conditions on deployment facilitate exposition of soldiers with subsequent colonization. Although colonizing strains are frequently cleared from their hosts after returning from deployment, transmission to close contacts of the soldiers in the home country cannot be excluded and therapeutic options are reduced if colonization progresses to invasive infection. Since sophisticated culture-based diagnostic approaches are typically not available in the field setting on deployment, molecular rapid diagnostic test systems are an option for transmission control if the locally prevalent molecular resistance mechanisms are known. Efforts for global resistance surveillance can contribute to better understanding of resistance distribution and spread at deployment sites. This review summarizes experience of the military medical services with multidrug resistance on deployment and with the influx of resistant strains to the home country and discusses potential use of available molecular rapid test systems as an option for the field setting.

Validated measurements of microbial loads on environmental surfaces in intensive care units before and after disinfecting cleaning

AIMS

Preanalytic aspects can make results of hygiene studies difficult to compare. Efficacy of surface disinfection was assessed with an evaluated swabbing procedure.

METHODS AND RESULTS

A validated microbial screening of surfaces was performed in the patients' environment and from hands of healthcare workers on two intensive care units (ICUs) prior to and after a standardized disinfection procedure. From a pure culture, the recovery rate of the swabs for Staphylococcus aureus was 35%-64% and dropped to 0%-22% from a mixed culture with 10-times more Staphylococcus epidermidis than S. aureus. Microbial surface loads 30 min before and after the cleaning procedures were indistinguishable.

CONCLUSIONS

The quality-ensured screening procedure proved that adequate hygiene procedures are associated with a low overall colonization of surfaces and skin of healthcare workers. Unchanged microbial loads before and after surface disinfection demonstrated the low additional impact of this procedure in the endemic situation when the pathogen load prior to surface disinfection is already low.

SIGNIFICANCE AND IMPACT OF THE STUDY

Based on a validated screening system ensuring the interpretability and reliability of the results, the study confirms the efficiency of combined hand and surface hygiene procedures to guarantee low rates of bacterial colonization.

Antibiotic stewardship and horizontal infection control are more effective than screening, isolation and eradication

Purpose

The global rise of multidrug resistant organisms (MDROs) is of major concern since infections by these pathogens are difficult, and in some cases, even impossible to treat. This review will discuss the effectiveness of a pathogen-independent alternative approach consisting of the implementation of antibiotic stewardship (ABS) programs, improvement of hand hygiene compliance, and daily antiseptic body washings instead of “screening, isolation and eradication” as recommended by many infection control guidelines today.

Methods

A review of the literature.

Results

The classical approach composed of screening, isolation and eradication has many limitations, including lack of standardization of the screening methods, risk of medical errors for patients in isolation and failure to eradicate resistant bacteria. Notably, concrete evidence that this current infection control approach actually prevents transmission is still lacking. We found that a novel approach with the training of infectious diseases specialists can reduce the usage of antimicrobials, thereby significantly decreasing the emergence of new MDROs. Moreover, increased hand hygiene compliance not only reduces transmission of MDROs, but also that of sensitive organisms causing the majority of nosocomial infections. Further, instruments, such as continuing education, bed-side observation, and the use of new tools, e.g. electronic wearables and Wi-Fi-equipped dispensers, are all options that can also improve the current low hand hygiene compliance levels. In addition, daily antiseptic body washes were observed to reduce the transmission of MDROs, especially those deriving from the body surface-like MRSA and VRE in specific settings. Finally, antiseptic body washes were seen to have similar effects on reducing transmission rates as screening and isolation measures.

Conclusions

In summary, this review describes a novel evidence-based approach to counteract the growing medical challenge of increasing numbers of MDROs.

Efficacy and acceptability of rectal and perineal sampling for identifying gastrointestinal colonization with extended spectrum β-lactamase Enterobacteriaceae

OBJECTIVES

We evaluated 'pre-laboratory' factors associated with the detection of extended spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) colonization including anatomical site, and staff and patient factors.

METHODS

All admissions to a large London hospital over 3 months were approached to provide rectal and perineal swabs, which were cultured for ESBL-E using chromogenic media. ESBL-E detection rates for patient- or staff-collected rectal or perineal swabs were compared using McNemar tests. Binary logistic regression was used to explore factors associated with patients declining to provide a rectal swab. The impact of simplifying the verbal study description to patients to improve the participation rate was evaluated.

RESULTS

Carriage of ESBL-E was significantly higher in rectal swabs than perineal swabs (7.8% of 4006 versus 3.8% of 4006, p <0.001), whether collected by staff or patients; 31.9% of 869 patients did not provide a rectal swab before the change in study description compared with 7.6% of 3690 patients afterwards (p <0.001). In multivariable analysis, factors associated with patients declining to provide a rectal swab were younger age (OR 0.99, 95% CI 0.99-1.00), female gender (OR 1.26, 95% CI 1.04-1.52), transfers from other hospitals (OR 1.77, 95% CI 1.07-2.93) or an unknown admission route (OR 1.61, 95% CI 1.09-2.37), being admitted before the change in study description (OR 0.39, 95% CI 0.31-0.48), and the staff member who consented the patient (p <0.001); ethnicity was not a significant factor.

CONCLUSIONS

Rectal swabs are recommended for the detection of ESBL-E colonization. Staff and patient factors influence whether patients participate in prevalence studies, which may skew their findings.