Comparison of FecalSwab and ESwab devices for storage and transportation of Diarrheagenic bacteria

Effectiveness of using liquid transport media in bacteriological diagnostics of diphtheria infection

The results of evaluating the effectiveness of the use of liquid transport media at the preanalytical stage of bacteriological diagnosis of diphtheria infection are presented. A typical toxigenic strain of C. diphtheriae biovar gravis № 665 was used. The experiments were carried out using a laboratory-prepared medium based on GRM-broth (State research center for applied biotechnology and microbiology, Obolensk), a transport system with a fleecy probe swab (DELTALAB) and a transport system ∑-Transwab ® with a polyurethane Sigma-swab (Medical Wire & Equipment Co. (Bath) Ltd.). The tampons were pooled with a 24-hour bacterial culture of C. diphtheriae, then immediately seeded on Tellurite-containing blood agar. Storage conditions were simulated for 6-24 hours: at room conditions +(20-25)° C, in the refrigerator +(4-8)° C, in a thermostat +(37±1)° C. Storage of C. diphtheriae was most optimal on two liquid transport systems in a refrigerator +(4-8)° C for 6 and 24 hours; in room conditions +(20-25)° C - there was a decrease in seeding after 6 hours and loss of pathological material after 24 hours, more pronounced on a fleecy probe swab; under thermostat conditions +(37±1)° C on both transport systems, a decrease in seeding was noted after 6 hours and a complete loss of pathological material after 24 hours. The results obtained demonstrated the efficiency of using the Amies liquid transport medium and justify the need to develop a domestic analogue of the transport system based on the Amies liquid medium for the bacteriological diagnosis of diphtheria infection.

Occurrence of Salmonella enterica in grey-headed flying foxes from New South Wales

Salmonella enterica and Campylobacter jejuni are significant foodborne zoonotic pathogens causing gastroenteritis in humans. Domestic animals are commonly implicated as reservoirs of S. enterica and C. jejuni, but both are also detected in wild animals. Salmonella enterica serovar Typhimurium is the most common cause of human salmonellosis in Australia; however, Salmonella enterica serovar Wangata is associated with sporadic human outbreaks in New South Wales and wild animals may be a potential reservoir. To determine if wild grey-headed flying foxes (GHFF; Pteropus poliocephalus) are reservoirs of Salmonella and Campylobacter, faecal samples were collected from three GHFF colonies in New South Wales and cultured for the presence of Salmonella and Campylobacter. One Salmonella isolate was cultured from 254 GHFF faecal samples (0.39%). Whole genome sequencing was used to genetically characterise the Salmonella isolate and perform phylogenetic analysis. The GHFF isolate was determined to be Salmonella Typhimurium ST19. The GHFF isolate carried a virulence plasmid and other virulence factors, but did not exhibit antimicrobial resistance. Phylogenetic analysis determined that the GHFF isolate was most closely related to a cluster of six isolates: four from human salmonellosis cases in Queensland and two from Australian livestock. Neither Campylobacter nor Salmonella Wangata were cultured from the 254 GHFF faecal samples. This study concluded that wild GHFF in New South Wales are not major reservoirs for Salmonella, and the zoonotic risks associated with S. enterica carriage by urban GHFF are low for the general public.

Evaluation of the FecalSwab for Stool Specimen Storage and Molecular Detection of Enteropathogens on the BD Max System

The FecalSwab system (Copan Italia, Brescia, Italy) is a convenient alternative to bulk stool for the diagnosis of enteric pathogens. Although the U.S. Food and Drug Administration (FDA) approved for transport and culture of enteric bacterial pathogens, the FecalSwab has not been well assessed for its suitability with molecular platforms. In this study, we evaluated the FecalSwab as a specimen type for the BD Max system using the viral and bacterial enteric panels (BD Diagnostics, Baltimore, MD, USA). A total of 186 unpreserved stool specimens were collected and used to prepare matched bulk stool and FecalSwab samples. Performance was equivalent (P > 0.48) to bulk stool for all targets when 50 μl of FecalSwab specimen was loaded onto the BD Max assays. As stool specimens are often collected off-site from the clinical microbiology laboratory and require transport, we assessed the stability of stool specimens stored for up to 14 days at 4°C, 22°C, or 35°C to account for varying transportation conditions. Molecular detection for the majority of viral targets (excluding astrovirus) was unaffected (change in cycle threshold [ΔC_T ] ≤ 1) by sample storage temperature over the 2-week period; however, detection of enteric bacteria was variable if specimens were not refrigerated (22°C or 35°C). By demonstrating equivalent performance to matched bulk stool and maintaining molecular detection sensitivity when stored at 4°C, we suggest that the FecalSwab is a suitable specimen type for enteropathogen diagnostics on the BD Max system.

Recovery of aerobic gram-negative bacteria from the Copan Eswab transport system after long-term storage

We evaluated the Copan Eswab transport system for the quantitative recovery of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa after 1, 2, 3, 5, and 7 days of storage at room and refrigerator temperatures, and 7 and 30 days of storage at -80 °C and -20 °C using mono- and polymicrobial samples. The study was based on Clinical and Laboratory Standards Institute (CLSI) M40-A2 standard procedures on the quality control of microbiological transport systems. Eswab met the CLSI standards at room and refrigerator temperatures for all (combinations of) bacterial strains tested. At room temperature, after 24 h, bacterial growth was observed. At -80 °C, bacterial viability was maintained in monomicrobial samples; however, in polymicrobial samples, P. aeruginosa recovery was compromised. Storage at -20 °C was unsuitable. We conclude that specimens collected using Eswab should be transported to the laboratory as soon as possible. If transport or processing is delayed, specimens should preferably be stored at refrigerator temperatures.

Impact of freeze/thaw cycles and single freezing at -80 °C on the viability of aerobic bacteria from rectal swabs performed with the ESwabTM system

The testing of bacterial preservation should be included in preliminary studies to epidemiological studies. In the case of multidrug-resistant organism (MDRO) studies, quantifications of the bacteria make it possible to understand their emergence. The purpose of this preliminary study was to evaluate the performance of ESwab^TM on survival of Escherichia coli, Klebsiella pneumoniae, and Enterococcus faecalis, based on the number of freezing and thawing (F/T) cycles at -80 °C and freezing time. A first experiment with 9 samples showed that multiple F/T cycles drastically affected Enterobacteriaceae viabilities and less E. faecalis one. A single freezing maintained the three species viabilities during three weeks. A second experiment showed that E. coli survival was maintained with a 3-month single freezing. This study which used a limited number of bacterial isolates is however a proof of concept establishing the utility of ESwab^TM samples when frozen once in quantitative studies of bacteria.

Viability of bacterial enteropathogens in fecal samples in the presence or absence of different types of transport media

Transport media are recommended to improve the sensitivity of fecal culture, but there are limited published data comparing bacterial viability in feces stored with or without transport media. In this study, recovery of bacteria from culture-positive feces after 7 days of storage was assessed under the following conditions: without transport media (w/oTM); with FecalSwab™ Transport and Preservation Medium (FSTM); and with modified Cary-Blair (mCB). All Shiga toxin-producing E. coli (STEC) positive specimens (n = 23) and ≥97.5% of Salmonella-positive specimens (n = 40) remained positive under all conditions. Campylobacter (n = 41) was isolated from 82.9% of feces stored in mCB, 68.4% in FSTM, and 70.7% w/oTM; Shigella (n = 14) 85.7%, 78.6%, and 78.6%; and Yersinia (n = 16) 93.8%, 87.5%, and 81.3%, respectively (P = 0.076, Cochran's Q). Transport media were not required for STEC or Salmonella. mCB may be better than w/oTM or FSTM for other pathogens, but an evaluation with a larger number of specimens is required.

Evaluation of rectal swab use for the determination of enteric pathogens: a prospective study of diarrhoea in adults

OBJECTIVES

A stool sample is the sample of choice for microbiological testing of enteric pathogens causing diarrhoea, but a rectal swab can be a more practical alternative. A prospective observational study was performed to evaluate the diagnostic performance of flocked rectal swab specimens using the syndromic molecular approach to determine the aetiology of diarrhoea in adults.

METHODS

We compared the performance of rectal swabs with stool samples as the reference standard in determining viral, bacterial and protozoal pathogens using real-time multiplex PCR as well as standard stool culture. Paired samples of stool and rectal swab specimens were collected from 304 adult patients with diarrhoea, presented at the Department of Infectious Diseases, University Medical Centre Ljubljana, between June 2016 and August 2017.

RESULTS

Overall sensitivity of rectal swab samples in the syndromic molecular approach was 83.2% (95% CI 77.2%-88.1%). Pathogen group-specific analysis of rectal swabs showed sensitivity of 65.6% (95% CI 52.7%-77.1%) for viruses and 57.1% (95% CI 28.9%-82.3%) for parasites. For bacteria, sensitivity was 86.5% (95% CI 79.5%-91.8%) when PCR was performed and 61.4% (95% CI 52.4%-69.9%) when culture for bacteria was performed. Mean threshold cycle (Ct) values for most pathogens were higher in rectal swab specimens than in stool specimens.

CONCLUSIONS

Our results indicate that rectal swabs can be used in the diagnosis of diarrhoea in adults when stool specimens are not available or when rapid aetiological determination is needed. However, rectal swabs should be analysed using a molecular approach. The mean Ct value for most pathogens is higher in rectal swab specimens than in stool specimens.

Evaluation of the Use of Rectal Swabs for Laboratory Diagnosis of Clostridium difficile Infection

For the diagnosis of Clostridium difficile infection (CDI), microbiological testing is almost always accomplished through the analysis of stool specimens. We evaluated the performances of rectal swabs with liquid transport medium (FS) and nylon flocked dry swabs for the detection of C. difficile Additionally, the impact on the diagnostic yield of storing swabs at -80°C for up to 3 months was evaluated. Sixty clinical stool samples positive for C. difficile by PCR were used for simulating rectal swabbing. FS and dry swabs were dipped into the stool and tested by PCR directly after swabbing at 1 and 3 months after storage at -80°C. Stool and the liquid medium of FS were additionally tested by a combination of glutamate dehydrogenase antigen (GDH) testing and toxin A/B enzyme immunoassay (EIA), as well as by toxigenic culture (TC). Using dry swabs, the PCR-based detection rate of C. difficile was equal to the rate using stool samples (30/30 [100%]), whereas the detection rate in FS was significantly lower (25/30 [83.2%]; P = 0.019). The sensitivities of FS for detecting C. difficile by PCR, TC, GDH testing, and toxin A/B EIA were 83.3%, 85.7%, 88%, and 68.9%, respectively. Storage of swabs at -80°C had no impact on the detection rate. FS cannot replace stool samples in the two-step laboratory diagnosis of CDI, as the sensitivities were too low, probably due to diluting effects of the fecal sample in the liquid medium. For simple PCR-based detection of C. difficile, dry swabs proved to be a suitable alternative to the use of stool samples.

Enhanced culture recovery of Campylobacter with modified Cary-Blair medium: A practical field experience

Modified Cary-Blair medium derived devices have been implemented in many laboratories to optimize culture recovery of common bacterial enteric pathogens. Our analysis constitutes the first report of routine laboratory experience supporting the idea that the use of such devices enhances Campylobacter recovery from stools.

Evaluation of Copan FecalSwab as Specimen Type for Use in Xpert C. difficile Assay

Liquid-based microbiology (LBM) devices incorporating flocked swabs and preservation medium ease transport of specimens and improve specimen yield compared to traditional fiber wound swabs; however, the performance of LBM collection devices has not been evaluated in many molecular assays. It is unclear how the differences in matrix and specimen loading with an LBM device will affect test performance compared to traditional collection devices. The purpose of this study was to evaluate the performance of specimens collected in FecalSwab transport medium (Copan Diagnostics, Murrieta, CA) compared to unpreserved stool using the Cepheid Xpert C. difficile assay (Cepheid, Sunnyvale, CA). Results equivalent to unpreserved stool samples were obtained when 400 μl of FecalSwab-preserved stool was employed in the Xpert assay. The positive and negative percent agreement of specimens inoculated with FecalSwab medium (n = 281) was 97.0% (95% confidence interval [CI], 90.9 to 96.4%) and 99.4% (95% CI, 96.4 to 99.9%), respectively, compared to reference results obtained using unpreserved stool. Throughout this study, only four discrepant results occurred when comparing preserved specimens to unpreserved stool specimens in the Xpert C. difficile PCR assay. Post discrepant analysis, using the BD MAX Cdiff assay, the specificity and sensitivity both increased to 100%. The high positive and negative percent agreements observed in this study suggest that stool preserved in FecalSwab media yields equivalent results to using unpreserved stool when tested on the Xpert C. difficile assay, allowing laboratories to adopt this liquid-based microbiology collection device.

Liquid based microbiological transport systems: conformity assessment of two commercial devices

We compared two types of liquid-based microbiology devices for microorganism viability according to standardized quantitative elution method CLSI M40-A2. The eSwab® met CLSI acceptance criteria of viability maintenance for all microorganisms tested. The Σ-Transwab® failed to meet CLSI acceptance criteria for Peptostreptococcus anaerobius, Prevotella melaninogenica, Fusobacterium nucleatum and Haemophilus influenzae.