Preliminary reading of antibiogram by microdilution for clinical isolates in urine culture.

PURPOSE: We evaluated a modification of automated antibiograms in urine cultures designed to facilitate the early interpretation of minimum inhibitory concentrations (MICs) and accelerate the targeted treatment of urinary tract infections (UTIs), METHODS: A prospective study was conducted of 309 isolates (219 Enterobacteriaceae, 75 Enterococcus spp., and 15 non-fermenting Gram-negative bacilli (NFGNB), and a retrospective study of 9 carbapenemase-producing clinical isolates from urine cultures. Colonies grown on conventional isolation plates were inoculated in MicroScan Walkaway system panels and incubated for 7 h, using a MicroScan AutoScan-4 plate reader for preliminary MIC determination by turbidimetry. Resulting antibiograms were compared with definitive antibiograms obtained after incubation for 17 h. RESULTS: Preliminary and definitive readings were concordant for 86.7% of Gram-positive cocci isolates (65/75), 61.6% of Enterobacteriaceae (135/219), and 53.3% of NFGNB. The agreement rate was greater than 90% for most antimicrobials against Gram-positive cocci (94.7% or more) and Enterobacteriaceae, (97.2% or more for 10 of 17 antibiotics) except with nitrofurantoin (89%). The agreement rate was 86.7% or more for most antibiotics against NFGNB apart from piperacillin/tazobactam, aztreonam, amikacin, and ciprofloxacin. Gram-negative bacilli showed the highest differences in MIC values between preliminary and definitive readings. CONCLUSIONS: A preliminary antibiogram reading may be useful in urine cultures to reduce the delay before targeted antibiotherapy, especially against Enterobacteriaceae and Gram-positive cocci, but not in cases of carbapenemase-producing NFGNB. Further local studies are warranted to evaluate the usefulness of this approach in relation to resistance rates.

Evaluation of the Qvella FAST System and the FAST-PBC cartridge for rapid species identification and antimicrobial resistance testing directly from positive blood cultures.

Blood culture diagnostics require rapid and accurate identification (ID) of pathogens and antimicrobial susceptibility testing (AST). Standard procedures, involving conventional cultivation on agar plates, may take up to 48 hours or more until AST completion. Recent approaches aim to shorten the processing time of positive blood cultures (PBC). The FAST System is a new technology, capable of purifying and concentrating bacterial/fungal pathogens from positive blood culture media and producing a bacterial suspension called "liquid colony" (LC), which can be further used in downstream analyses (e.g., ID and AST). Here, we evaluated the performance of the FAST System LC generated from PBC in comparison to our routine workflow including ID by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using Sepsityper, AST by automatized MicroScan WalkAway plus and directly inoculated disk diffusion (DD), and MICRONAUT-AM for yeast/fungi. A total of 261 samples were analyzed, of which 86.6% (226/261) were eligible for the comparative ID and AST analyses. In comparison to the reference technique (culture-grown colonies), ID concordance of the FAST System LC and Sepsityper was 150/154 (97.4%) and 123/154 (79.9%), respectively, for Gram positive; 67/70 (95.7%) and 64/70 (91.4%), respectively, for Gram negative. For AST, categorical agreement (CA) of the FAST System LC in comparison to the routine workflow for Gram-positive bacteria was 96.1% and 98.7% for MicroScan and DD, respectively. Similar results were obtained for Gram-negative bacteria with 96.6% and 97.5% of CA for MicroScan and DD, respectively. Taken together, the FAST System LC allowed the laboratory to significantly reduce the time to obtain correct ID and AST (automated MicroScan) results 1 day earlier and represents a promising tool to expedite the processing of PBC.

Comparing antimicrobial resistant genes and phenotypes across multiple sequencing platforms and assays for Enterobacterales clinical isolates.

INTRODUCTION: Whole genome sequencing (WGS) of bacterial isolates can be used to identify antimicrobial resistance (AMR) genes. Previous studies have shown that genotype-based AMR has variable accuracy for predicting carbapenem resistance in carbapenem-resistant Enterobacterales (CRE); however, the majority of these studies used short-read platforms (e.g. Illumina) to generate sequence data. In this study, our objective was to determine whether Oxford Nanopore Technologies (ONT) long-read WGS would improve detection of carbapenem AMR genes with respect to short-read only WGS for nine clinical CRE samples. We measured the minimum inhibitory breakpoint (MIC) using two phenotype assays (MicroScan and ETEST) for six antibiotics, including two carbapenems (meropenem and ertapenem) and four non-carbapenems (gentamicin, ciprofloxacin, cefepime, and trimethoprim/sulfamethoxazole). We generated short-read data using the Illumina NextSeq and long-read data using the ONT MinION. Four assembly methods were compared: ONT-only assembly; ONT-only assembly plus short-read polish; ONT + short-read hybrid assembly plus short-read polish; short-read only assembly. RESULTS: Consistent with previous studies, our results suggest that the hybrid assembly produced the highest quality results as measured by gene completeness and contig circularization. However, ONT-only methods had minimal impact on the detection of AMR genes and plasmids compared to short-read methods, although, notably, differences in gene copy number differed between methods. All four assembly methods showed identical presence/absence of the blaKPC-2 carbapenemase gene for all samples. The two phenotype assays showed 100% concordant results for the non-carbapenems, but only 65% concordance for the two carbapenems. The presence/absence of AMR genes was 100% concordant with AMR phenotypes for all four non-carbapenem drugs, although only 22%-50% sensitivity for the carbapenems. CONCLUSIONS: Overall, these findings suggest that the lack of complete correspondence between CRE AMR genotype and phenotype for carbapenems, while concerning, is independent of sequencing platform/assembly method.

Role of Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry for Species Identification of Acinetobacter Strains.

Introduction Acinetobacter species has become a leading cause of nosocomial infections in recent years. Objectives The aim of the study was to establish the usefulness of matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS) for the identification of Acinetobacter species with respect to conventional biochemical methods and MicroScan WalkAway 96 Plus system and to compare the antibiotic susceptibility test results Kirby-Bauer disk diffusion method with MicroScan WalkAway 96 Plus automated identification and antimicrobial susceptibility testing system. Materials and Methods The study sample comprised 100 clinical isolates of Acinetobacter species. They were all identified using MALDI-TOF MS and compared with other two identification systems. Statistical Analysis Comparison of categorical variables by Fisher's exact test or Pearson's chi-square test was done. All statistical tools were two tailed, and a significant level p < 0.05 was used. All statistical tests were performed using SPSS v22.0 (Armonk IBM Corp., New York, United States). Cohen's kappa coefficients were also calculated and used as applicable. Results MALDI-TOF MS revealed 92 A. baumannii , 2 Acinetobacter nosocomialis , 3 Acinetobacter lwoffii , and 1 each was identified as Acinetobacter junii , Acinetobacter johnsonii , and Acinetobacter tandoii . There was moderate agreement between identification by MicroScan WalkAway and MALDI-TOF, and substantial agreement between conventional biochemical tests and MALDI-TOF. We found that there was a 100% categorical agreement with respect to susceptibility of aminoglycosides (amikacin, gentamicin, tobramycin) and cephalosporins (ceftazidime, cefepime, cefotaxime) between disk diffusion method and MicroScan WalkAway 96 Plus system. Total of 16 errors were observed. Conclusion Although MALDI-TOF MS could be useful to identify A. baumannii but not other species in the genus, it is a rapid, reliable method and can be routinely used in clinical laboratories.

Evaluation of Piperacillin-Tazobactam Testing against Enterobacterales by the Phoenix, MicroScan, and Vitek2 Tests Using Updated Clinical and Laboratory Standards Institute Breakpoints.

In 2022, the Clinical and Laboratory Standards Institute (CLSI) updated piperacillin-tazobactam (TZP) breakpoints for Enterobacterales, based on substantial data suggesting that historical breakpoints did not predict treatment outcomes for TZP. The U.S. Food and Drug Administration (FDA) has not yet adopted these breakpoints, meaning commercial manufacturers of antimicrobial susceptibility testing devices cannot obtain FDA clearance for the revised breakpoints. We evaluated the Phoenix (BD, Sparks, MD), MicroScan (Beckman Coulter, Sacramento, CA), and Vitek2 (bioMérieux, Durham, NC) TZP MICs compared to reference broth microdilution for a collection of 284 Enterobacterales isolates. Phoenix (n = 167 isolates) demonstrated 84.4% categorical agreement (CA), with 4.2% very major errors (VMEs) and 1.8% major errors (MEs) by CLSI breakpoints. In contrast, CA was 85.0% with 4.3% VMEs and 0.8% MEs for the Phoenix with FDA breakpoints. MicroScan (n = 55 isolates) demonstrated 80.0% CA, 36.4% VMEs, and 4.8% MEs by CLSI breakpoints and 81.8% CA, 44.4% VMEs, and 0.0% MEs by FDA breakpoints. Vitek2 (n = 62 isolates) demonstrated 95.2% CA, 6.3% VMEs, and 0.0% MEs by CLSI and 96.8% CA, 0.0% VMEs, and 2.2% MEs by FDA breakpoints. Overall, the performance of the test systems was not substantially different using CLSI breakpoints off-label than using on-label FDA breakpoints. However, limitations were noted with higher-than-desired VME rates (all three systems) and lower-than-desired CA (MicroScan and Phoenix). Laboratories should consider adoption of the revised CLSI breakpoints with automated test systems but be aware that some performance challenges exist for testing TZP on automated systems, regardless of breakpoints applied.

Validation of Three MicroScan® Antimicrobial Susceptibility Testing Plates Designed for Low-Resource Settings.

Easy and robust antimicrobial susceptibility testing (AST) methods are essential in clinical bacteriology laboratories (CBL) in low-resource settings (LRS). We evaluated the Beckman Coulter MicroScan lyophilized broth microdilution panel designed to support Médecins Sans Frontières (MSF) CBL activity in difficult settings, in particular with the Mini-Lab. We evaluated the custom-designed MSF MicroScan Gram-pos microplate (MICPOS1) for Staphylococcus and Enterococcus species, MSF MicroScan Gram-neg microplate (MICNEG1) for Gram-negative bacilli, and MSF MicroScan Fastidious microplate (MICFAST1) for Streptococci and Haemophilus species using 387 isolates from routine CBLs from LRS against the reference methods. Results showed that, for all selected antibiotics on the three panels, the proportion of the category agreement was above 90% and the proportion of major and very major errors was below 3%, as per ISO standards. The use of the Prompt inoculation system was found to increase the MIC and the major error rate for some antibiotics when testing Staphylococci. The readability of the manufacturer's user manual was considered challenging for low-skilled staff. The inoculations and readings of the panels were estimated as easy to use. In conclusion, the three MSF MicroScan MIC panels performed well against clinical isolates from LRS and provided a convenient, robust, and standardized AST method for use in CBL in LRS.

Comparative Evaluation of Two Automated ID/AST Systems and Mikrolatest Kit in Assessing the In Vitro Colistin Susceptibility of Carbapenem-Resistant Enterobacteriaceae Isolates: A Single-Center Exploratory Study from North India.

Aims: To generate preliminary data about comparative evaluation of two automated ID/AST systems and Mikrolatest kit in determining in vitro colistin susceptibility of carbapenem-resistant Enterobacteriaceae spp. Materials and methods: Twenty-three carbapenem-resistant Escherichia coli and Klebsiella pneumoniae and two carbapenem-sensitive multidrug-resistant E. coli isolates obtained from various clinical samples of inpatients were included in the study. Species-level identification and antibiotic susceptibility testing (AST) of test isolates was performed using BD phoenix and MicroScan WalkAway 96 Plus automated systems. Identity was reconfirmed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Additional colistin susceptibility testing was performed using Mikrolatest MIC colistin susceptibility testing kit (reference method). Results: Results showed that 16% isolates (27.3% [3/11] K. pneumoniae and 7.1% [1/14] E. coli) exhibited in vitro colistin resistance by the reference method. While the categorical agreement between BD Phoenix M50 ID/AST system and reference test w. r. t in vitro colistin susceptibility results was 100% and 92.9% for K. pneumoniae & E. coli, respectively, it was much lower between MicroScan WalkAway 96 plus ID/AST system and the latter. Almost perfect agreement (96%; kappa: 0.834) was observed between BD Phoenix M50 system and reference method. Conclusions: The results of this study are preliminary and cannot be generalized. Multicentric studies with large sample sizes should be conducted throughout the country to gain a deeper understanding of the subject under consideration.

Aeromonas dhakensis: Clinical Isolates with High Carbapenem Resistance.

Aeromonas dhakensis is ubiquitous in aquatic habitats and can cause life-threatening septicaemia in humans. However, limited data are available on their antimicrobial susceptibility testing (AST) profiles. Hence, we aimed to examine their AST patterns using clinical (n = 94) and non-clinical (n = 23) isolates with dehydrated MicroScan microdilution. Carbapenem resistant isolates were further screened for genes related to carbapenem resistance using molecular assay. The isolates exhibited resistance to imipenem (76.9%), doripenem (62.4%), meropenem (41.9%), trimethoprim/sulfamethoxazole (11.1%), cefotaxime (8.5%), ceftazidime (6%), cefepime (1.7%) and aztreonam (0.9%), whereas all isolates were susceptible to amikacin. Clinical isolates showed significant association with resistance to doripenem, imipenem and meropenem compared to non-clinical isolates. These blacphA were detected in clinical isolates with resistance phenotypes: doripenem (67.2%, 45/67), imipenem (65.9%, 54/82) and meropenem (65.2%, 30/46). Our findings showed that the MicroScan microdilution method is suitable for the detection of carbapenem resistance in both clinical (48.9-87.2%) and non-clinical (4.3-13.0%) isolates. This study revealed that A. dhakensis isolates had relatively high carbapenem resistance, which may lead to potential treatment failure. Continued monitoring of aquatic sources with a larger sample size should be carried out to provide further insights.

Comparison of carbapenem minimum inhibitory concentrations of Oxacillin-48-like Klebsiella pneumoniae by Sensititre, Vitek 2, MicroScan, and Etest.

OBJECTIVES: The aim of this laboratory-based study was to compare carbapenem MICs yielded by Sensititre, Vitek 2, MicroScan WalkAway plus and Etest for Oxacillin (OXA)-48-like Klebsiella pneumoniae isolates. METHODS: Analysis was performed for categorical agreement for ertapenem, meropenem, and imipenem, and the proportion of isolates with MICs ≤8µg/mL and the MIC50/MIC90 for meropenem and imipenem, from a convenience sample of 82 deduplicated blood culture OXA-48-like K. pneumoniae isolates. RESULTS: The proportion of isolates testing susceptible to ertapenem by Etest (19/82, 23.1%) differed from Sensititre/Vitek (0/82) and MicroScan (2/82, 2.4%) (p < 0.001 for all). For meropenem, the proportion of isolates susceptible by Etest (31/82, 37.8%) differed from Sensititre/Vitek (16/82, 19.5%) (p = 0.015). There was variation in the proportion of isolates that tested imipenem susceptible when comparing Sensititre (9/82, 11%) and Vitek (8/82, 9.8%) to MicroScan (27/82, 32.9%), p = 0.001 and p < 0.001, respectively, Sensititre and Vitek to Etest (45/82, 54.9%), p < 0.001 for both, and MicroScan to Etest, p = 0.007. The proportion of isolates with meropenem MICs ≤8µg/mL with Sensititre and Vitek differed significantly from Etest, 58.5% and 85.4%, respectively, p < 0.001. A 2-fold difference between the Sensititre and Vitek meropenem and imipenem MIC at which ≥50% of isolates were inhibited compared to the MicroScan, and a 4-fold difference compared to Etest, was present. CONCLUSIONS: Substantial variability in carbapenem MICs for OXA-48-like carbapenemase-producing Enterobacterales isolates by the four methods was demonstrated. Performance characteristics verification of MIC methods in use for the predominant carbapenemase-producing Enterobacterales type is required by laboratories to optimize the accuracy of carbapenem reporting.

Evaluation of MicroScan Bacterial Identification Panels for Low-Resource Settings.

Bacterial identification is challenging in low-resource settings (LRS). We evaluated the MicroScan identification panels (Beckman Coulter, Brea, CA, USA) as part of Médecins Sans Frontières' Mini-lab Project. The MicroScan Dried Overnight Positive ID Type 3 (PID3) panels for Gram-positive organisms and Dried Overnight Negative ID Type 2 (NID2) panels for Gram-negative organisms were assessed with 367 clinical isolates from LRS. Robustness was studied by inoculating Gram-negative species on the Gram-positive panel and vice versa. The ease of use of the panels and readability of the instructions for use (IFU) were evaluated. Of species represented in the MicroScan database, 94.6% (185/195) of Gram-negative and 85.9% (110/128) of Gram-positive isolates were correctly identified up to species level. Of species not represented in the database (e.g., Streptococcus suis and Bacillus spp.), 53.1% out of 49 isolates were incorrectly identified as non-related bacterial species. Testing of Gram-positive isolates on Gram-negative panels and vice versa (n = 144) resulted in incorrect identifications for 38.2% of tested isolates. The readability level of the IFU was considered too high for LRS. Inoculation of the panels was favorably evaluated, whereas the visual reading of the panels was considered error-prone. In conclusion, the accuracy of the MicroScan identification panels was excellent for Gram-negative species and good for Gram-positive species. Improvements in stability, robustness, and ease of use have been identified to assure adaptation to LRS constraints.

Multicenter study of automated systems for colistin susceptibility testing.

PURPOSE: Broth microdilution (BMD) stays as the reference testing method for determination of antimicrobial susceptibility testing (AST) to colistin and is considered essential for patient management and for monitoring of colistin resistance. This multicenter study aimed to evaluate the performance of automated systems for colistin AST among Enterobacterales as an alternative for BMD since the majority of laboratories use automated systems as first-line method. METHODS: Twenty colistin resistant (COL-R) including 10 MCR producers and 10 colistin-susceptible (COL-S) Enterobacterales isolates were blindly tested for colistin susceptibility with the routine automated AST systems used by 8 laboratories (3 with BD Phoenix, 3 with Vitek2 and 2 with MicroScan). Additionally, 3 reference strains (E. coli ATCC 25922, E. coli NCTC 13846, and one COL-R mcr-negative K. pneumoniae M/14750) were tested in triplicate by each laboratory. RESULTS AND CONCLUSION: Results were compared with BMD performed at the reference laboratory. BD Phoenix and MicroScan automated AST systems provide accurate and reproducible categorical results for the testing of colistin in Enterobacterales. However, Vitek2 system showed poor performance for the detection of COL-R isolates especially those with MICs close to the susceptibility breakpoint (categorical agreement of 88% and precision categorical agreement of 81%).

Comprehensive Statistical Evaluation of Etest®, UMIC®, MicroScan and Disc Diffusion versus Standard Broth Microdilution: Workflow for an Accurate Detection of Colistin-Resistant and Mcr-Positive E. coli.

Four colistin susceptibility testing methods were compared with the standard broth microdilution (BMD) in a collection of 75 colistin-susceptible and 75 mcr-positive E. coli, including ST131 isolates. Taking BMD as reference, all methods showed similar categorical agreement rates (CA) of circa 90%, and a low number of very major errors (VME) (0% for the MicroScan system and Etest®, 0.7% for UMIC®), except for the disc diffusion assay (breakpoint ≤ 11 mm), which yielded false-susceptible results for 8% of isolates. Of note is the number of mcr-positive isolates (17.3%) categorized as susceptible (≤2 mg/L) by the BMD method, but as resistant by the MicroScan system. ST131 mcr-positive E. coli were identified as colistin-resistant by all MIC-based methods. Our results show that applying the current clinical cut-off (>2 mg/L), many mcr-positive E. coli remain undetected, while applying a threshold of >1 mg/L the sensitivity of detection increases significantly without loss of specificity. We propose two possible workflows, both starting with the MicroScan system, since it is automated and, importantly, it categorized all mcr-positive isolates as colistin-resistant. MicroScan should be followed by either BMD or MIC-based commercial methods for colistin resistance detection; or, alternatively, MicroScan, followed by PCR for the mcr screening.

Identification of Candida Species from Clinical Samples in a Honduran Tertiary Hospital.

Candida species are one of the most important causes of human infections, especially in hospitals and among immunocompromised patients. The correct and rapid etiological identification of yeast infections is important to provide adequate therapy, reduce mortality, and control outbreaks. In this study, Candida species were identified in patients with suspected fungal infection, and phenotypic and genotypic identification methods were compared. A total of 167 axenic fungal cultures and 46 clinical samples were analyzed by HardyCHROM®, MicroScan®(Omron Microscan Systems Inc, Renton, WA, USA), and PCR-RFLP (Restriction Fragment Length Polymorphisms). The species of the C. albicans complex were the most frequent, followed by C. tropicalis and C. glabrata. Less common but clinically relevant species of Candida were also isolated. The comparison between the three methods was concordant, especially for the most common Candida species. Fungal DNA amplification was successful in all clinical samples.

Comparison between MALDI-TOF MS and MicroScan in the identification of emerging and multidrug resistant yeasts in a fourth-level hospital in Bogotá, Colombia.

BACKGROUND: The introduction of MALDI-TOF MS in the clinical microbiology laboratory has modified the approaches for the identification of fungi. Thanks to this tool, it is possible to identify cryptic species, which possess critical susceptibility patterns. Clinical strains were identified using the MicroScan and MALDI-TOF MS systems. Discrepant results from both methods were investigated using ITS rDNA barcoding. Finally, these isolates were also tested for in vitro susceptibility. RESULTS: The percentage of agreement between both methods to 498 yeast isolates was of 93.6% (32 discrepant isolates). The concordance of ITS sequencing with MALDI-TOF MS was higher (99%) than that of MicroScan (94%). Several of these discordant yeasts displayed high MICs for antifungal agents. CONCLUSIONS: Our study highlights the need of the MS and molecular approaches such as MALDI-TOF MS and ITS rDNA barcoding for the correct identification of emerging or cryptic yeast species; besides, some of these could be multidrug resistant. This work was the first experience in the implementation of the MALDI-TOF MS technology in Colombia. We found the first uncommon yeasts including Candida auris and we could identify Trichosporon faecalis. Our work highlights a clear necessity of an accurate yeast identification as a much more pertinent technique than the susceptibility profiles, because the most unusual yeasts exhibit resistance profiles to the few available antifungals.

Evaluation of the MicroScan Colistin Well and Gradient Diffusion Strips for Colistin Susceptibility Testing in Enterobacteriaceae.

Many laboratories are unable to perform colistin susceptibility testing. Diffusion-based antimicrobial susceptibility testing methods are not recommended, and not all laboratories have the capacity to perform broth microdilution (BMD). Using a multistep tiered approach, we investigated whether the adapted use of the MicroScan colistin well (4 µg/ml) could enhance laboratory capacity for the detection and subsequent molecular characterization of colistin-resistant Enterobacteriaceae For the MicroScan colistin well, categorical agreement with BMD was 92.7%, and the very major error rate was 10.7%. For gradient diffusion strips, the categorical agreement was 86.4%, and the very major error rate was 53.6%. The MicroScan colistin well detected all isolates carrying mcr-1 or mcr-2 genes (n = 16), but gradient diffusion strips identified an MIC of ≥4 for colistin for only 62.5% of these isolates. A 6-month prospective phenotypic and genotypic study performed at a single clinical microbiology laboratory assessed isolates growing in the MicroScan colistin well for concordance. While 37 of 39 isolates growing in the MicroScan colistin well displayed a colistin MIC of ≥4 by BMD, all were determined to be negative for the mcr-1 and mcr-2 genes by PCR. A retrospective review of all Escherichia coli, Klebsiella spp., and Enterobacter spp. tested by MicroScan at this laboratory in 2016 identified 260 of 7,894 (3.3%) isolates that grew in the MicroScan colistin well. Based on the data presented, clinical and public health laboratories could use the MicroScan colistin well as a first screen for the detection of isolates displaying elevated colistin MICs, which could then undergo further characterization.

Comparative evaluation of microscan walkaway 96 plus ID/AST system and mikrolatest broth microdilution kit in assessing In vitro colistin susceptibility of carbapenem-resistant clinical gram-negative bacterial isolates: Experience from a tertiary care teaching hospital in Rishikesh, Uttarakhand.

Context: As reports on colistin resistance are slowly emerging from different parts of the world, it is imperative that the clinical microbiology laboratories should generate accurate in vitro colistin susceptibility results. Aim: The aim is to generate preliminary data on the diagnostic utility of MicroScan WalkAway 96 Plus Identification ID/ Antimicrobial susceptibility testing AST system in determining in vitro colistin susceptibility of carbapenem-resistant clinical Gram-negative bacterial isolates. Settings and Design: A pilot study was conducted in a tertiary care teaching hospital located in Rishikesh, Uttarakhand, between May and June 2019. Materials and Methods: Thirty-four carbapenem-resistant Escherichia coli, Pseudomonas aeruginosa and Acinetobacter spp. isolated from various non-repetitive clinical samples during the study period, were subjected to antibiotic susceptibility testing using MicroScan ID/AST system. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry was used to confirm identity of these isolates. Additional colistin susceptibility testing of all test isolates was performed using Mikrolatest minimum inhibitory concentration antibiotic susceptibility testing kit (reference method), which is based on broth micro dilution (BMD) principle. Statistical Analysis Used: Fisher's exact test. Results: 11.8% (4/34) of the test isolates (100% [2/2] Acinetobacter junii, 10% [1/10] E. coli and 14.3% [1/7] P. aeruginosa respectively) exhibited in vitro colistin resistance by BMD method. Categorical agreement between MicroScan ID/AST system and Mikrolatest kit w. r. t in vitro colistin susceptibility test results was as follows: 71.4% (Acinetobacter baumannii), 85.7% (P. aeruginosa) and 100% (A. junii, A. johnsonii, E. coli and Klebsiella pneumoniae), respectively. Two major errors (MEs) for A. baumannii and one very ME for P. aeruginosa respectively were observed. Conclusions: Data generated by this study will be of help to the clinicians who are often faced with the dilemma of treating multi drug resistant infections with limited treatment options.

Performance Evaluation of Newly Developed Korean Antimicrobial Susceptibility Testing Panels for MicroScan System Using Clinical Isolates from Teaching Hospitals in Korea / 대한임상미생물학회지

BACKGROUND: Antimicrobial resistant continues to pose a threat to public health. Therefore, rapid and accurate antimicrobial susceptibility testing is very important. The objectives of this study were to evaluate the performance of the MicroScan system (Beckman Coulter, USA) with newly developed Korean Antimicrobial Susceptibility Testing Panels (KSCM panels) for antimicrobial susceptibility testing (AST) against clinical isolates in South Korea. METHODS: Three KSCM panels were designed in this study. For the performance evaluation, a total of 1,325 clinical isolates including 1,027 of Gram-negative bacilli and 298 Gram-positive cocci collected from eight general hospitals in South Korea were used. The results by KSCM panels were compared with those by conventional methods. RESULTS: By KSCM-1 panel for Gram-positive cocci, the rates of categorical agreement (CA) were >90% in all the antimicrobials tested in this study. The rates of major error (ME) were also 90%, ME rates <3%, and VME rates <1.5%. CONCLUSION: The newly developed three KSCM panels for MicroScan system (Beckman Coulter) showed excellent performance in AST against a large number of clinical isolates, and they are applicable to clinical microbiology laboratories.

Community Acquired Burkholderia cepacia Bacteraemia Presenting as MODS in an Immunocompetent Individual: An Unusual Case.

Burkholderia cepacia has been recognized as a group of highly virulent organisms known as Burkholderia cepacia complex (Bcc). Bcc are ubiquitous in nature and most commonly found in moist environment, on plant roots and soil. Because of its high intrinsic antibiotic resistance, Bcc is a major cause of morbidity and mortality in hospitalized patients. It is reported most commonly in immunocompromised patients especially in patients with cystic fibrosis. Here, we report a rare case report of bacteraemia by Burkholderia cepacia in an immunocompetent male, who presented with fever and Multiple Organ Dysfunction Syndrome (MODS). Burkholderia cepacia was isolated from his blood culture, which he acquired from his work place. He was treated successfully and discharged after negative blood culture.

Comparison of phenotypic and PCR methods for detection of carbapenemases production by Enterobacteriaceae.

Dissemination of carbapenem resistance via Enterobacteriaceae, particularly among Klebsiella pneumoniae and Escherichia coli, is a major public health concern. Rapid methods for determining antimicrobial susceptibility are important to ensure adequate and appropriate use of antimicrobial agents and to limit the spread of these bacteria. In the current study, we compared the rapidity, sensitivity and specificity of traditional methods and molecular-based Xpert Carba-R PCR assay to identify sixty isolates, (26 E. coli and 34 K. pneumoniae). The specificity of MicroScan was 100% while sensitivity to ertapenem (ERT), imipenem (IMI), and meropenem (MER) was 93%, 68.9%, and 55.17%, respectively. For the modified Hodge test, the specificity was 96.77% and sensitivity was 89.65%. Although some results of phenotypic assays matched with the definite PCR identification, some results were misleading. Out of the 29 positive PCR samples, three samples of K. pneumoniae were negative for the MHT and one E. coli sample was MHT positive but negative for the PCR. Nine samples were positive for the PCR but were determined as carbapenem sensitive by MicroScan. While MicroScan and MHT requires several hours and multi-steps to obtain results, Xpert Carba-R PCR assay takes less than an hour. Therefore, we recommend using Gene xpert Carba-R assay for the optimal carbapenemnase detection with reducing material, manpower and cost. Also it is important to know the type of carbapenemase is present.