C. Verhulst

Methicillin- Resistant Staphylococcus aureus in Meat Products, the Netherlands

A new methicillin-resistant Staphylococcus aureus (MRSA) clone related to pig and cattle farming was detected in the Netherlands. We investigated the extent of S. aureus presence in meat and found 36 S. aureus strains in 79 samples. Two strains were MRSA; 1 was multilocus sequence type 398, the clone related to farming.

Rectal Carriage of Extended-Spectrum-Beta-Lactamase-Producing Enterobacteriaceae in Hospitalized Patients: Selective Preenrichment Increases Yield of Screening

ABSTRACT This study evaluated the added value of selective preenrichment for the detection of rectal carriage of extended-spectrum-beta-lactamase-producing Enterobacteriaceae (ESBL-E). ESBL-E rectal carriage was identified in 4.8% of hospitalized patients, and 25.9% of ESBL-E rectal carriers were identified with selective preenrichment only.

Laboratory Detection of Extended-Spectrum-Beta-Lactamase-Producing Enterobacteriaceae: Evaluation of Two Screening Agar Plates and Two Confirmation Techniques

ABSTRACT The worldwide prevalence of extended-spectrum-beta-lactamase-producing ESBL-producing Enterobacteriaceae (ESBL-E) is increasing, making the need for optimized detection techniques more urgent. In this study we investigated the performance of two ESBL-E screening and two ESBL-E confirmation techniques. In accordance with the Dutch national guidelines (www.wip.nl), a collection of 642 highly resistant Enterobacteriaceae strains, as identified by Vitek2, was used to test the performances of two screening techniques (EbSA ESBL agar plate and ChromID ESBL agar plate) and of two confirmation techniques (MIC-strip ESBL and Vitek2 ESBL test panel). The individual test results were compared by using Etest, followed by a combination disk test if Etest results were inconclusive. Among group 1 isolates (Escherichia coli, Klebsiella spp., Proteus spp., Salmonella spp., and Shigella spp.) 291 (57.6%) were ESBL-E, versus 65 (47.4%) in group 2 (Enterobacter spp., Citrobacter spp., Morganella morganii, Serratia spp., and Providencia spp.). The sensitivities of all four tests for group 1 were comparable (EbSA, 96.6%; ChromID, 97.3%; MIC-strip, 99.6%; and Vitek2, 95.1%). The specificities of the EbSA and ChromID were the same (93.9%). However, the confirmation techniques produced many inconclusive test results, which reduces the applicability in routine laboratories. Only the two screening agar plates were validated for ESBL testing of group 2 microorganisms. They showed comparable sensitivities; however, the EbSA screening agar plate had a significantly higher specificity (78.6% versus 44.3%). In conclusion the screening agar plates performed better than the two confirmation techniques. The EbSA agar plate had the best overall performance.

Trends in Extended Spectrum Beta-Lactamase (ESBL) Producing Enterobacteriaceae and ESBL Genes in a Dutch Teaching Hospital, Measured in 5 Yearly Point Prevalence Surveys (2010-2014)

This paper describes the trends in prevalence of ESBL producing Enterobacteriaceae (ESBL-E) and ESBL genes, measured in five consecutive yearly Point Prevalence Surveys (PPS). All patients present in the hospital and in a day-care clinic (including patients on dialysis) on the day of the survey, were screened for perianal ESBL-E carriage. Perianal swabs were taken and cultured using an enrichment broth and a selective agar plate. Both phenotypic and genotypic methods were used to detect the production of ESBL, presence of ESBL-genes and clonal relatedness. Out of 2,695 patients, 135 (5.0%) were tested ESBL-E positive. The overall ESBL-E prevalence was stable over the years. Overall 5.2% of all ESBL-E were acquired by nosocomial transmission. A relative decrease of CTX-M-1-1-like ESBL genes (from 44 to 25%, p = 0.026) was observed, possibly related to the strong (>60%) decrease in antibiotic use in livestock in our country during the same period.

Evaluation of Brilliance MRSA 2 Agar for Detection of Methicillin-Resistant Staphylococcus aureus in Clinical Samples

ABSTRACT We compared 2 chromogenic media (Oxoid Brilliance MRSA 2 agar [Thermo Fisher Scientific] and MRSA-ID [bioMérieux]) for the detection of methicillin-resistant Staphylococcus aureus (MRSA) in 1,368 hospital samples. For both media, broth enrichment was essential to obtain satisfactory diagnostic performance. Although with direct cultures only, the diagnostic performance (particularly sensitivity) of Brilliance MRSA 2 agar appears better than that of MRSA-ID, no difference in sensitivity or specificity between the media was detected after inclusion of an enrichment step.

Evaluation of the DiversiLab Typing Method in a Multicenter Study Assessing Horizontal Spread of Highly Resistant Gram-Negative Rods

ABSTRACT The worldwide prevalence of highly resistant Gram-negative rods (HR-GNR) is increasing rapidly. Reliable typing methods are needed to detect and control outbreaks and to monitor the effectiveness of infection control programs in endemic situations. In this study, we investigated the performance of the DiversiLab typing method in comparison with the amplified fragment length polymorphism (AFLP) typing method. Six hundred fifty-three HR-GNR isolates, which were obtained during a 6-month prospective survey in 18 Dutch hospitals, were typed by AFLP and DiversiLab. Subsequently, the sensitivity and specificity of DiversiLab were calculated, using AFLP as the reference method. In addition, results were compared by means of epidemiological linkage, and Cohens kappa for agreement was calculated. DiversiLab considered significantly more isolates (275) to belong to a cluster than AFLP (198) (P < 0.001). In direct comparison, the sensitivity was 83.8%, and the specificity was 78.6%. When epidemiological linkage was included in the analysis, DiversiLab considered eight isolates as secondary cases, which were considered unique in AFLP. Only two secondary cases, according to AFLP, were missed by DiversiLab. This results in a kappa for agreement of 0.985. In daily practice, a typing method has to be used in combination with epidemiological information. When this was done, DiversiLab was shown to be a reliable method for the typing of HR-GNR. This, in combination with the ease of use and the speed, makes DiversiLab an appropriate method for screening in routine clinical practice. When a cluster is suspected and the consequences of these findings are substantial, a confirmatory analysis should be performed.

Extensive dissemination of extended spectrum β-lactamase-producing Enterobacteriaceae in a Dutch nursing home

OBJECTIVE Risk factors for rectal carriage of ESBL-E and transmission were investigated in an outbreak of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E). DESIGN Rectal carriage of ESBL-E was determined in a cross-sectional survey by culture of perianal swabs or fecal samples. Both phenotypical and genotypical methods were used to detect the production of ESBL. Nosocomial transmission was defined as the presence of genotypically related strains in ≥2 residents within the NH. Patient characteristics and variables in infection control practices were registered to investigate risk factors for transmission. SETTING A nursing home (NH) in the southern Netherlands. PARTICIPANTS Of 189 residents, 160 residents (84.7%) were screened for ESBL-E carriage. Of these 160 residents, 33 (20.6%) were ESBL-E positive. ESBL carriage rates varied substantially between wards (range, 0-47%). Four different ESBL-E clusters were observed. A bla CTX-M1-15 positive E. coli ST131 constituted the largest cluster (n=21) and was found in multiple wards (n=7). RESULTS Our investigation revealed extensive clonal dissemination of bla CTX-M1-15-positive E. coli ST131 in a nursing home. Unexplained differences in ESBL prevalence were detected among the wards. CONCLUSIONS As NHs constitute potential sources of multidrug-resistant bacteria, it is important to gain a better understanding of the risks factors and routes of transmission of ESBL-E.

Extended-spectrum β-lactamase producing Klebsiella spp. in chicken meat and humans: a comparison of typing methods

Recently, chicken meat was identified as a plausible source of extended-spectrum β-lactamase (ESBL) -producing Escherichia coli in humans. We investigated the relatedness of ESBL-producing Klebsiella spp. in chicken meat and humans. Furthermore, we tested the performance of SpectraCell RA(®) (River Diagnostics), a new typing method based on Raman spectroscopy, in comparison with multilocus sequence typing (MLST) for Klebsiella pneumoniae. Twenty-seven phenotypically and genotypically confirmed ESBL-producing Klebsiella spp. isolates were typed with MLST and SpectraCell RA. The isolates derived from chicken meat, human rectal swabs and clinical blood cultures. In the 22 ESBL-producing K. pneumoniae isolates, CTX-M15 was the predominant genotype, found in five isolates of human origin and in one chicken meat isolate. With MLST, 16 different STs were found, including five new STs. Comparing the results of SpectraCell RA with MLST, we found a sensitivity of 70.0% and a specificity of 81.8% for the new SpectraCell RA typing method. Therefore, we conclude that SpectraCell RA is not a suitable typing method when evaluating relationships of ESBL-producing Klebsiella spp. at the population level. Although no clustering was found with isolates of chicken meat and human origin containing the same ESBL genes, MLST showed no clustering into distinctive clones of isolates from chicken meat and human origin. More studies are needed to elucidate the role of chicken meat in the rise of ESBL-producing Klebsiella spp. in humans.

Prolonged colonisation with Escherichia coli O25:ST131 versus other extended-spectrum beta-lactamase-producing E. coli in a long-term care facility with high endemic level of rectal colonisation, the Netherlands, 2013 to 2014.

The extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli clone ST131 (ESBL-ST131) has spread in healthcare settings worldwide. The reasons for its successful spread are unknown, but might include more effective transmission and/or longer persistence. We evaluated the colonisation dynamics of ESBL-producing E. coli (ESBL-EC), including ESBL-ST131, in a long-term care facility (LTCF) with an unusually high prevalence of rectal ESBL-EC colonisation. During a 14-month period, rectal or faecal samples were obtained from 296 residents during six repetitive prevalence surveys, using ESBL-selective culture. Transmission rates, reproduction numbers, and durations of colonisation were compared for ESBL-ST131 vs other ESBL-EC. Furthermore, the likely time required for ESBL-ST131 to disappear from the LTCF was estimated. Over time, the endemic level of ESBL-ST131 remained elevated whereas other ESBL-EC returned to low-level prevalence, despite comparable transmission rates. Survival analysis showed a half-life of 13 months for ESBL-ST131 carriage, vs two to three months for other ESBL-EC (p < 0.001). Per-admission reproduction numbers were 0.66 for ESBL-ST131 vs 0.56 for other ESBL-EC, predicting a mean time of three to four years for ESBL-ST131 to disappear from the LTCF under current conditions. Transmission rates were comparable for ESBL-ST131 vs other ESBL-EC. Prolonged rectal carriage explained the persistence of ESBL-ST131 in the LTCF.

Effect of Manganese in Test Media on In Vitro Susceptibility of Enterobacteriaceae and Acinetobacter baumannii to Tigecycline

ABSTRACT We assessed the effect of increasing manganese concentrations in test media (0.001 to 1,024 mg/liter) on MICs of tigecycline. For both broth microdilution (BMD) and Etests, this effect was negligible for physiological concentrations, but MICs increased when concentrations exceeded 8 mg/liter. Susceptibility testing should be performed on media with standardized low manganese content.