MicroScan WalkAway Research Articles

Selection and Evaluation of Suitable Quality Control Strains for Meropenem Antimicrobial Susceptibility Testing through Preliminary External Quality Assessment

BackgroundQuality control (QC) of carbapenem susceptibility testing for Gram-negative bacteria faces challenges due to limited measuring ranges and the lack of suitable QC strains. This study aimed to select and evaluate QC strains for meropenem antimicrobial susceptibility testing (AST) through a pilot external quality assessment (EQA). MethodsCandidate QC strains for meropenem AST were selected based on primary AST data and genomic information from the Japan Antimicrobial Resistant Bacterial Bank. Phenotype stability was verified through serial passaging and MIC comparison with original strains. The validated broth microdilution method was used to determine the target MIC value in a pilot EQA involving 47 clinical laboratories in Japan using ten different AST methods. ResultsTwo strains, Citrobacter freundii JBBDAJB-19-0032 (Strain-A) and Enterobacter hormaechei subsp. steigerwaltii JBEBAAB-19-0102 (Strain-B), both carrying blaIMP-1, were selected as candidate QC strains. The meropenem MICs for Strain-A and Strain-B were 4 mg/L and 2 mg/L, respectively. In the pilot EQA, 43 laboratories reported appropriate results for Strain-A and 40 laboratories reported appropriate results for Strain-B. The MIC range was 2-8 mg/L for Strain-A and 1-4 mg/L for Strain-B. However, 19 and 12 laboratories, respectively, reported out-of-range MICs using AST plates on the MicroScan WalkAway (Beckman Coulter). Inappropriate results were reported by four and seven laboratories, respectively, using common methods for Strain-A and Strain-B, respectively. ConclusionsThe candidate QC strains selected for this study are suitable for meropenem AST EQA, except when the measuring range of certain methods does not match their QC range.

In Vitro Synergistic Activity of Ceftazidime-Avibactam and Aztreonam against New Delhi Metallo-β-Lactamase-Producing Clinical Enterobacterales Isolates

Background: Carbapenemase-producing-Enterobacterales (CPE) infections are on the rise and associated with increased morbidity and mortality, due to a limited number of therapeutic options. The goal of this study was to assess the synergistic activity of ceftazidime-avibactam (CZA) and aztreonam (ATM) combination against phenotypically and genetically characterized blaMBL-producing Enterobacterales.Methods: In this study, forty (n=40) non-repeat, CPE clinical isolates, including: n=35 Klebsiella pneumoniae, n=2 each of Escherichia coli and Klebsiella oxytoca, and n=1 Enterobacter cloacae isolates were identified and susceptibilities were assessed using the Vitek-II compact (bioMérieux, Inc., France) and Microscan Walkaway (Beckman Coulter) systems. Genotypic analysis of clinically relevant carbapenemases was performed by using Xpert-Carba-R assay on GeneXpert (Cepheid, USA). The minimum inhibitory concentrations (MICs) and synergy testing of CZA and ATM, were tested by the Etest fixed ratio method (bioMérieux, Inc., France). The fractional inhibitory concentration index (FICI) was calculated for each antibiotic.Results: Our results showed that 97.5% of blaMBL-producing Enterobacterales isolates were susceptible to an in-vitro CZA + ATM combination regimen. The fractional inhibitory concentration index (FICI) ranged from 0.001 to 1.001. Among the tested CPE isolates, Synergy was observed in 36/40 (90%), an additive effect was observed in 5% (n=2)’ while two (5%) isolates showed indifference. There was no antagonism observed in our study.Conclusion: Our study exhibited a potent activity of CZA and ATM combination synergy against clinical CPE metallo- β-lactamase producers. More extensive studies involving a variety of Gram-negative pathogens with different resistance mechanisms are required to determine the efficacy of this combination regimen.Keywords: Synergy; Aztreonam; Ceftazidime-Avibactam; Carbapenem-Resistant Enterobacterales; Etest

Detecting and Reporting Extended Spectrum Beta-Lactamases Producers: Evaluation of Three Approaches and the Clinical Impact

Abstract Introduction/Objective Since the COVID-19 pandemic, bacteria producing extended spectrum beta-lactamases (ESBLs) have increased >30%. Laboratories can perform phenotypic microbroth dilution or molecular approaches to identify ESBL producers. However, the gold standard is a laborious double disc synergy test. We evaluated the concordance among the three approaches, the clinical impact, and justification of reporting ESBL producers. Methods/Case Report Seventy-eight ESBL producers identified by microbroth dilution (MicroScan WalkAway, Beckman Coulter, Brea, California, USA) or detection of blaCTX-M gene from blood cultures (BCID2 Panel, BioFire, Biomerieux, Salt Lake City, Utah, USA) were tested using double disc synergy test retrospectively. Concordance among the methods evaluated. Discordant cases were reviewed with subsequent patient chart review. Results (if a Case Study enter NA) Tested isolates included E. coli (n=44, 57%), K. pneumoniae (n=19, 24%), K. oxytoca (n=7, 9%), and P. mirabilis (n=8, 10%). Concordance between microbroth dilution and disk diffusion was 86% (67/78). For isolates with genotypic testing (n=16), concordance with microbroth dilution and disk diffusion was 93% and 88%, respectively. Overall concordance was 88%. There were 12 isolates (E. coli:8, P. mirabilis: 2, and K. pneumoniae:2) with discordant results from one method. The susceptibility profile of discordant isolates revealed resistance to ceftriaxone or ceftazidime (11/12), penicillin (11/12), and aztreonam (6/12); 10/12 isolates were resistant to at least 2 groups of these antibiotics, a phenotype of ESBL producers. Clinical teams acknowledged presence of ESBLs in 83% (10/12) of cases and 58% (7/12) warranted treatment with meropenem or combinational therapy. Infection prevention implemented contact isolate procedures in all cases. Conclusion Our current in-house methods (e.g., microbroth dilution and genotypic testing) are still justified for ESBL testing to optimize patient care in a timely fashion. In the minor cases with discordant results, clinical care was unaffected. Laboratory workflow changes need to take laboratory efficiency, patient outcomes, and actionable clinical changes into consideration.

Vancomycin Resistant Enterococci and Trend of Antimicrobial Susceptibility in Urine Cultures

Background: Enterococci are emerging nosocomial pathogen showing resistance to broad spectrum antibiotics. As reported by the center for disease control and prevention, enterococci (13.9%) are the second leading cause of urinary tract infection, after Escherichia coli. After the first report of vancomycin-resistant enterococci in England (1988), India reported its first vancomycin resistant enterococci isolate from New Delhi (1999). The prevalence of vancomycin resistant enterococci ranges from 1-9%, in India. To evaluate the prevalence of vancomycin resistant enterococci among urinary isolates and to check their antimicrobial resistance pattern. Methods: A retrospective observational study conducted at a tertiary care hospital. Data were analysed from November, 2017 to October, 2018. A total of 12,129 urine samples were received and subjected to culture on HiCrome UTI agar (Hi-Media laboratories, Mumbai) and incubated at 37 °C for a period of 18-24 hours. Antimicrobial susceptibility was performed using Kirby–Bauer disc diffusion method. Identification was done on the basis of colony colour and species identification was done by using biochemical test as per standard laboratory protocol. In one case automated siemens microscan walkaway identification system was used for confirmation. Results: Enterococci were isolated in 4.06% from urine cultures out of which 7.52% were vancomycin resistant. Most of the vancomycin resistant enterococci isolate (86.49%) were multi drug resistant. Conclusion: In vancomycin resistant enterococci related urinary tract infection, nitrofurantoin can be used as an appropriate first choice in uncomplicated cases and linezolid should be reserved for serious and complicated urinary tract infections.

Bacterial and Genetic Features of Raw Retail Pork Meat: Integrative Analysis of Antibiotic Susceptibility, Whole-Genome Sequencing, and Metagenomics.

The global antibiotic resistance crisis, driven by overuse and misuse of antibiotics, is multifaceted. This study aimed to assess the microbiological and genetic characteristics of raw retail pork meat through various methods, including the isolation, antibiotic susceptibility testing (AST), whole-genome sequencing (WGS) of selected indicator bacteria, antibiotic residue testing, and metagenomic sequencing. Samples were purchased from 10 pre-selected retail stores in Gauteng, South Africa. The samples were aseptically separated, with portions sent to an external laboratory for isolating indicator bacteria and testing for antibiotic residues. Identification of the isolated bacteria was reconfirmed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). AST was performed using the Microscan Walkaway system (Beckman Coulter, Brea, CA, USA). WGS and metagenomic sequencing were performed using the Illumina NextSeq 550 instrument (San Diego, CA, USA). The isolated E. coli and E. faecalis exhibited minimal phenotypic resistance, with WGS revealing the presence of tetracycline resistance genes. Both the isolated bacteria and meat samples harboured tetracycline resistance genes and the antibiotic residue concentrations were within acceptable limits for human consumption. In the metagenomic context, most identified bacteria were of food/meat spoilage and environmental origin. The resistome analysis primarily indicated beta-lactam, tetracycline and multidrug resistance genes. Further research is needed to understand the broader implications of these findings on environmental health and antibiotic resistance.

Rapid Antimicrobial Susceptibility Testing Using the MicroScan System: Performance Evaluation of a 4-Hour Bacterial Cultivation From Positive Blood Cultures.

A reliable and above all, rapid antimicrobial susceptibility test (AST) is required for the diganostics of blood stream infections (BSI). In this study, resistance testing using DxM MicroScan WalkAway (MicroScan) from a 4-h subculture is compared with the standard overnight culture (18-24h). Randomly selected positive blood cultures (PBC, n = 102) with gram-negative bacteria were included in the study. PBC were sub-cultured onto appropriate agar plates and AST by MicroScan was performed after 4 h of incubation and repeated after incubation for 18-24 h as standard. In a total of 1909 drug-strain pairs, the 4-h subculture approach showed a very high essential agreement (EA) (98.6%) and categorical agreement (CA) (97.1%) compared with the standard. The incidence of minor error (mE), major error (ME), very major error (VME), and adjusted very major error (aVME) was 1.1%, 0.4%, 12.9%, and 5.3%, respectively. In summary, the use of 4-h subcultures for resistance testing with the MicroScan offers a very reliable and easy to realize time saving when testing positive blood cultures with gram-negative bacteria.

Carbapenem-Resistant Enterobacter cloacae Complex in Southwest China: Molecular Characteristics and Risk Factors Caused by NDM Producers.

The isolation rate of carbapenem-resistant Enterobacter cloacae complex (CREC) is continuously increasing. The aims of this study were to investigate the molecular characteristics and risk factors associated with CREC infections. Bacterial species were identified using the matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) (Bruker Daltonik GmbH, Bremen, Germany), and the hsp60 gene was utilized for further typing. Antimicrobial susceptibilities were assessed through the MicroScan WalkAway 96 Plus system (Siemens, Germany) and the microbroth dilution method. Antimicrobial resistance genes were screened through polymerase chain reaction (PCR), while the homologous relationship was assessed using multilocus sequence typing (MLST). Conjugation experiments were performed to verify whether the plasmid could be transferred. Additionally, logistic regression model was employed to analyze risk factors for CREC infections. 32 strains of CREC bacteria were isolated during the study, yet only 20 were retained for preservation. While the isolates demonstrated resistance to the majority of antibiotics, they exhibited high sensitivity to polymyxin B and tigecycline. All isolates carried the blaNDM resistance gene, including 13 blaNDM-1 isolates and 7 blaNDM-5 isolates. MLST homology analysis revealed the presence of seven known ST types and one new ST type. Conjugation experiments confirmed that 13 isolates were capable of transferring the blaNDM resistance gene to Escherichia coli strain EC600. Single-factor analysis identified multiple primary risk factors for CREC infection, but multivariate analysis did not reveal independent risk factors. This study investigates the molecular characteristics and risk factors associated with CREC infections. The detection rate of CREC strains in our hospital is continuously rising and homology analysis suggested that strains might spread in our hospital, emphasizing the importance of implementing effective preventive measures to control the horizontal transmission of plasmid-mediated antimicrobial resistance genes.

Molecular Detection of Carbapenemase-producing Uropathogens Isolated from Pregnant Women

Pregnant women are at high risk of urinary tract infections (UTIs). There is growing concern about the rise of Enterobacteriaceae that are resistant to drugs, including, more recently, those that produce carbapenemase. The study aimed to perform molecular detection and antibiograms of Enterobacteriaceae that produce carbapenemase in pregnant women with UTIs. Using clinical specimens taken from the general hospital in Qurrayat, Saudi Arabia, we identified 83 isolates of Enterobacteriaceae. Microscan WalkAway Plus and Phoenix automated analyzers were used to carry out bacterial isolation using standard microbiological procedures. DNA sequencing was employed to identify the carbapenemase bla genes, while phenotypic techniques and PCR were employed to characterize bacterial strains. The carbapenemase bla gene was detected among the 30 members of the Enterobacteriaceae. Of these 30, bla gene variants were found in 13 isolates (41%) blaOXA-23; 11 (35%) blaNDM-1; 10 (32%) blaNDM-5; 7 (22%) blaOXA-24; 4 (12%) blaVIM and 3 (9%) blaOXA-48. A statistically non-significant relationship between the blaNDM-1 and Klebsiella pneumoniae (p = 0.33) was seen, and the correlation between the blaNDM variants was not significantly associated with Pseudomonas aeruginosa (p = 0.5) and Escherichia coli (p = 0. 14). Antibiotic resistance was extremely common, as evidenced by the minimum inhibitory concentrations (MICs) in vitro of carbapenemase-producing Enterobacteriaceae against a number of antibiotic groups. These bacterial strains exhibited minimal resistance to amikacin (14; 46.6%) and were not resistant to two aminoglycosides, namely Ertapenem (30; 100%) and Meropenem (30; 100%). Our investigation shows that many Enterobacteriaceae that produce carbapenemases are a serious risk for pregnant women and others in the community. As a result, alternatives for therapy are limited to the aminoglycosides Ertapenem and Meropenem.

Sensitivity Profile of Fosfomycin, Nitrofurantoin, and Co-trimoxazole Against Uropathogens Isolated From UTI Cases in a Secondary Care Center, KSA.

Background Fosfomycin, nitrofurantoin, and co-trimoxazole are cheap and effective first-line oral antimicrobials in cases of uncomplicated cystitis in males and non-pregnant females. Fosfomycin and nitrofurantoin are called urinary antiseptics because these two drugs are primarily excreted in the kidney and concentrated in the urine without systemic effect. The present study was designed to evaluate the in vitro activities of fosfomycin, nitrofurantoin, and co-trimoxazoleagainst uropathogens isolated at King Khalid Hospital Al-Majmaah, KSA. Methods The study was conducted at the King Khalid Hospital Al Majmaah, KSA, from September 1, 2021, until February 28, 2022. The patients' urine samples were inoculated on the Cystein Lactose Electrolytes Deficient (CLED) medium, and uropathogens were isolated. The organisms' identification and sensitivity testing against cotrimoxazole, fosfomycin, and nitrofurantoin was conducted using a Microscan automated analyzer, the MicroScan WalkAway Beckman Coulter, Sacramento, CA, USA. Results The study comprised non-repeat 137 patients who were either admitted to the hospital or treated as outpatients, yielding a total of 147 isolates. Nitrofurantoin showed a lower resistance rate, around 20% (n = 29), followed by fosfomycin at 23% (n = 34). The resistance rate of cotrimoxazole was 43% (n = 63). Overall, nitrofurantoin and fosfomycin showed relatively lower resistance against all isolates. Conclusions Being cheap and effective, we propose that fosfomycin and nitrofurantoin be used as first-line treatments in patients presenting with uncomplicated UTIs.

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

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. 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 agreementrate 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. 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.

Assessment of in vitro colistin susceptibility of carbapenem-resistant clinical Gram-negative bacterial isolates using four commercially available systems & Whole-genome sequencing: A diagnostic accuracy study

AimTo analyze the diagnostic utility of commercially available platforms and Whole-genome sequencing (WGS) for accurate determination of colistin susceptibility test results. Material & methodsAn exploratory diagnostic accuracy study was conducted in which sixty carbapenem-resistant Gram-negative bacteria were subjected to identification and AST using MALDI-TOF MS & MicroScan walkaway 96 Plus. Additional AST was performed using the BD Phoenix system and Mikrolatest colistin kit. The test isolates were subjected to Vitek-2 and WGS at CRL, Bengaluru. ResultsThere was no statistically significant agreement between the colistin susceptibility results obtained by WGS, with those of commercial phenotypic platforms. The MicroScan 96 Plus had the highest sensitivity (31 %) & NPV (77 %), and the BD Phoenix system had the highest specificity (97 %) and PPV (50 %), respectively, for determining colistin resistance. ConclusionThe utility of WGS as a tool in AMR surveillance and validation of phenotypic AST methods should be explored further.

High Bacterial Contamination Load of Self-Service Facilities in Sakaka City, Aljouf, Saudi Arabia, with Reduced Sensitivity to Some Antimicrobials.

Although self-service facilities (SSFs) have been used on a large scale worldwide, they can be easily contaminated by microorganisms from the hands of their sequential users. This research aimed to study the prevalence and antimicrobial susceptibility/resistance of bacteria contaminating SSFs in Sakaka, Aljouf, Saudi Arabia. We randomly swabbed the surfaces of 200 SSFs, then used the suitable culture media, standard microbiological methods, and the MicroScan WalkAway Microbiology System, including the identification/antimicrobial susceptibility testing-combo panels. A high SSFs' bacterial contamination load was detected (78.00%). Ninety percent of the samples collected in the afternoon, during the maximum workload of the SSFs, yielded bacterial growth (p < 0.001 *). Most of the contaminated SSFs were supermarket payment machines, self-pumping equipment at gas stations (p = 0.004 *), online banking service machines (p = 0.026 *), and barcode scanners in supermarkets. In the antiseptic-deficient areas, 55.1% of the contaminated SSFs were detected (p = 0.008 *). Fifty percent of the contaminated SSFs were not decontaminated. The most common bacterial contaminants were Escherichia coli (70 isolates), Klebsiella pneumoniae (66 isolates), Staphylococcus epidermidis (34 isolates), methicillin-resistant Staphylococcus aureus (18 isolates), and methicillin-sensitive Staphylococcus aureus (14 isolates), representing 31.53%, 29.73%, 15.32%, 8.11%, and 6.31% of the isolates, respectively. Variable degrees of reduced sensitivity to some antimicrobials were detected among the bacterial isolates. The SSFs represent potential risks for the exchange of antimicrobial-resistant bacteria between the out-hospital environment and the hospitals through the hands of the public. As technology and science advance, there is an urgent need to deploy creative and automated techniques for decontaminating SSFs and make use of recent advancements in materials science for producing antibacterial surfaces.

Rapid AST: Possibility of inferring resistance mechanisms with complex phenotypes.

The new automated systems designed for rapid performance of AST have significantly reduced the response time for susceptibility testing of microorganisms causing bacteremia and sepsis. The Accelerate Pheno® system (AAC) is one such system. Our objective for this study was to determine whether the AAC system is capable of providing an accurate susceptibility profile to infer resistance mechanisms in different carbapenemase-producing isolates when compared to the MicroScan WalkAway System (MWS). Disk diffusion method was also performed on all isolates as a reference method. Additionally, we compared the results obtained with the routine AST production system. We selected 19 isolates from the cryobank of the Microbiology department, all of which were carbapenemase-producing gram-negative bacilli. AAC was able to identify and infer the resistance of a total of 10 isolates, with an EA and CA of 84.2% for meropenem and 88.2% and 64.7% for ertapenem EA and CA, respectively. If we consider the disk diffusion technique, the CA was 57.9% and 76.5% for meropenem and ertapenem. However, in the presence of carbapenemases, AAC was not able to provide adequate MICs or infer the resistance mechanisms of the isolates accurately. Further studies with a larger number of isolates, including the new antibiotics ceftolozane/tazobactam and ceftazidime/avibactam, are needed for a more comprehensive comparison.

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.

Performance Evaluation of BD Phoenix and MicroScan WalkAway Plus for Determination of Fosfomycin Susceptibility in Enterobacterales.

Fosfomycin is an old bactericidal drug that has gained increasing interest in the last decade for its potential use in multi-drug resistant gram-negative infections. However, evidence on fosfomycin susceptibility testing reports a poor correlation between commercial methods vs. reference agar dilution (AD) for Enterobacterales (EB). The study aimed at assessing the performance of two automated systems for the determination of fosfomycin susceptibility in EB clinical isolates. Fosfomycin susceptibility testing results of two collections of 100 non-duplicate clinical EB strains obtained using two different platforms (BD Phoenix and MicroScan WalkAway Plus) were compared with those obtained by AD. Categorical agreement (CA), major error (ME) and very major error (VME) rates were calculated. BD Phoenix exhibited a 6.9% rate of false-resistant results and achieved a CA of 69%, whereas MicroScan WalkAway Plus achieved 3.7% of false-resistant results and 72% of CA. Both automated systems showed poor detection of resistant isolates, with 49.1% and 56.2% of false-susceptible results for BD Phoenix and Microscan WalkAway Plus, respectively. Overall, agar dilution remains the most suitable method for routine laboratory antimicrobial susceptibility testing of fosfomycin on Enterobacterales strains, given the poor performance of automated systems. The application of both automated systems, in the clinical laboratories reporting of fosfomycin, should be reviewed in light of the accuracy results falling below the acceptable threshold.

In Vitro Antimicrobial Activity of Essential Oil Derived from Callistemon viminalis Aerial Part

Background: Essential oils extracted from plants have been widely used in antimicrobial activity, particularly the Callistemon viminalis, with a high number of essential oils extracted. Objectives: To identify the chemical composition of essential oil derived from Callistemon viminalis and evaluates its antimicrobial activity against selected bacterial and fungal strains. Subjects and methods: During the study, the antimicrobial activity of different selected essential oils on some bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella enteritidis, Staphylococcus aureus, and Streptococcus pneumonia) and fungus (Candida albicans) was evaluated. The MicroScan WalkAway automated device was used to confirm the identification of the bacteria microorganisms and the germ tube and microscopy detection confirmed the fungus identity of specific morphological features after growth on corn meal agar, used in this study. Results: the GC-MS analysis reveal that the chemical composition of the essential oil was contained Eucalyptol (41.17%) area, Viridiflorol (8.43%) area, Alpha-Pinene (4.53%) area, Alpha-Terpineol (4.53%) area and others. The essential oil shows activity against Staphylococcus aureus with inhibition zone diameter of 10 mm, and for Streptococcus pneumoniae, with ihibition zone of 22 mm. Conclusion: The highest antimicrobial activity was against S. aureus and S. pneumonia of Gram-positive bacteria. The study result show that resistance from Gram-negative bacteria and resistance from fungus C. albicans to the oil. These varying results of bacterial suseptabilty may be based on the construction of the bacterial cell wall between Gram-positive and Gram-negative bacteria. The essential oil components detected with higher percent area in GC-MS from C. viminalis are Eucalyptol, alpha-Pinene, Viridiflorol, beta-Eudesmol, and alpha-Tocopherol.

MALDI-TOF MS-based identification and antibiotics profiling of Salmonella species isolated from retail chilled chicken in Saudi Arabia

ObjectivesSalmonella is a well-known foodborne pathogen that is spread around the world. It causes diseases both in animals and humans. The development of antibiotic-resistant Salmonella strains results in the failure of formerly effective drugs in humans and animals and poses a serious threat to world health. In the Kingdom of Saudi Arabia, the rise in Salmonella prevalence in poultry is seen as a serious problem. Saudi Arabia has endured several epidemics of Salmonella infections with varied patterns of drug resistance in the last few decades. MethodsA total of 112 chilled chicken carcass of five different local poultry companies were procured from retail outlets in Jeddah. The ISO 6579:2002 standard was followed to isolate and identify Salmonella. The isolates were identified using cultural and biochemical features and were further confirmed using (MALDI-TOF MS). Antibiotic susceptibility for each Salmonella isolate was determined using the automated MicroScan WalkAway plus System. ResultsOut of the 112 samples, 35 (31.25%) samples harboured Salmonella spp. According to MALDI-TOF MS identification, 34 isolates were recognized as S. Typhimurium or S. Enteritidis with high confidence levels (log (score) values between 2.00 and 3.00), while one isolate was characterized as a Salmonella sp. with a low confidence level (log (score) < 2.00). The antibiotic sensitivity pattern demonstrated resistance to fluoroquinolones, cephalosporin, and penicillin, however, carbapenem was effective against all the isolated Salmonella spp. Out of the 35 isolates, 23 (65.71%) isolates resisted three or more than three different antibiotics and thus were regarded as multi-drug resistant (MDR) strains. ConclusionsThe findings of this study indicated the presence of MDR Salmonella species in chilled chicken marketed in Jeddah, Saudi Arabia which highlights potential public health risks. Accordingly, a thorough investigation of the veterinary service, safety and hygienic system of poultry industry, as well as vendors is needed to safeguard the consumer health.

Molecular Confirmation of an Indole-Negative Klebsiella oxytoca Isolated from a Patient with Cystitis.

Klebsiella oxytoca is an opportunistic pathogen that causes nosocomial infections. Here, we describe an unusual clinical strain of indole-negative K. oxytoca, GU175, isolated from the urine of a patient with cystitis. The GU175 strain was identified as K. pneumoniae with a probability of 99.40%, negative for indole production, and resistant to third-generation cephalosporins by using the MicroScan Walkaway 40 SI system with the Negative combo EN1 J panel. Biochemical characterization of this strain using lysine-indole motility medium was negative for indole production. However, identification tests using the MALDI Biotyper system and 16S rRNA gene sequence analysis revealed that GU175 is K. oxytoca. DNA sequence analysis of the tryptophanase operon comparing the GU175 strain with the revertant GU176 strain, which tested positive for indole, revealed a point mutation in the Shine-Dalgarno sequence upstream of tnaC in the GU175 strain. This is the first report of indole-negative K. oxytoca, which was attributed to a mutation in the DNA sequence of the tryptophanase operon isolated from a patient with a urinary tract infection. As indole-negative K. oxytoca can be misidentified as K. pneumoniae by biochemical characterization, clinical microbiologists should be aware of such misidentifications.

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.

Direct inoculation method for identification and antimicrobial susceptibility testing using matrix-assisted laser desorption ionization-time of flight mass spectrometry and both the Vitek 2 and MicroScan Walkaway 96 Plus systems

The aim of our study was to evaluate a protocol utilizing serum separator tubes (SST) to facilitate a faster, cost-effective, direct method for rapid sensitivity testing and identification of positive blood cultures. Spiked cultures were inoculated into either Becton Dickinson (BD) BACTECTM Aerobic Plus or Anaerobic/F bottles containing sterile human blood. Bottles were immediately processed when positive. A parallel study using patient isolates was used in which bacteria were pelleted by SST from positive blood cultures. For identification, a portion of the pellet was tested by matrix-assisted laser desorption/ionization as described by the manufacturer. MicroScan panels and Vitek 2 results were compared. Categorical agreement was used as comparison to standard subculture and/or polymerase chain reaction methods. No discordant identifications were observed, and 86% generated a successful identification when compared to subculture methods. For the Vitek 2, we observed a 99% essential agreement when compared to the subculture method. For the MicroScan Walkaway, we observed 94.9%, 97.4%, and 100% categorical agreement for MIC panels 53, 38, and MICroSTREP Plus 2, respectively. Turnaround times were reduced from 4 hours for identification and 11 hours for antimicrobial sensitivity testing. We conclude that the SST method results in timelier, actionable results for antimicrobial stewardship initiatives.