Evaluation of a DNA microarray (Check-MDR CT102) for rapid detection of TEM, SHV, and CTX-M extended-spectrum β-lactamases and of KPC, OXA-48, VIM, IMP, and NDM-1 carbapenemases

Application of Antimicrobial Peptides as Diagnostic Biosensors

The COVID-19 pandemic has shown how emerging infectious diseases could quickly affect the global health and economy. New pathogens with pandemic potential are also expected to appear soon. Moreover, the large use of antibiotics has led to the development of different so-called "superbugs" capable of escaping all of the current antibiotics. In this context, the early and cost-effective detection of pathogens is crucial to avoid the spreading of new pathogens. Here, we present molecular sensors for the recognition of a broad panel of different bacterial species. The detection is based on the use of bacteria-binding peptides (BBPs) in combination with horseradish peroxidase (HRP). We developed a reliable ELISA-like assay that permits us to study the affinity of different BBPs toward some of the most important bacterial pathogens.

Molecular Detection of Carbapenemases and Extended-Spectrum β-Lactamases-Encoding Genes in Clinical Isolates of Pseudomonas aeruginosa in Iran

Background: Pseudomonas aeruginosa is a unique Gram-negative opportunistic pathogen that is the leading cause of nosocomial infections. Objectives: This study aimed to investigate the prevalence of the main carbapenemase and extended-spectrum β-lactamases encoding genes in P. aeruginosa clinical isolates. Methods: In the present study, we collected 85 P. aeruginosa clinical isolates from different wards of three military hospitals in Tehran, Iran. We used disk diffusion and agar dilution methods to determine resistance to 12 different antibiotics in these isolates. Also, we assessed the blaIMP, blaVIM, blaSHV, blaTEM, and blaCTX genes by polymerase chain reaction methods among all isolates. Results: Our results revealed that all isolates were resistant to two antibiotics, and 76 (89.4%) of isolates were multidrug-resistant. We observed maximum and minimum resistance rates against ticarcillin (n = 77; 90.5%) and colistin (n = 7; 8.2%), respectively. The blaVIM, blaIPM, blaTEM, blaSHV, and blaCTX genes were harbored by 44 (51.8%), 20 (23.5%), 41 (48.2%), 24 (28.2%), and 16 (18.8%) isolates, respectively. Conclusions: The resistance rate among P. aeruginosa strains is significantly increasing that causes nosocomial infections due to different mechanisms, including the high frequency of metallo-β-lactamases and extended-spectrum β-lactamases genes.

Evaluation of the "AMR Direct Flow Chip Kit" DNA microarray for detecting antimicrobial resistance genes directly from rectal and nasopharyngeal clinical samples upon ICU admission

INTRODUCTION

Prompt detection of antibiotic resistance genes in healthcare institutions is of utmost importance in tackling the spread of multi-drug resistant micro-organisms. We evaluated the Antimicrobial Resistance (AMR) Direct Flow Chip Kit versus phenotypic screening assays for rectal and nasopharyngeal specimens upon ICU admission.

METHODS

A total of 184 dual specimens (92 rectal and 92 nasopharyngeal swabs) from 92 patients were collected from 11/2017 to 8/2018. All swabs were subjected to both AMR and phenotypic tests according to their origin. The degree of agreement of the two methods was assessed by the kappa coefficient.

RESULTS

The kappa coefficient showed perfect agreement for MRSA, ESBLs, oxacillinases and vancomycin resistance genes (1.000, p<0.01) and very good agreement for mecA-positive CoNS, KPC-carbapenemases and metallo-beta-lactamases (0.870, p<0.01; 0.864, p<0.01; and 0.912, p<0.01, respectively).

CONCLUSION

The AMR Direct Flow Chip Kit is a useful alternative to phenotypic testing for rapid detection of resistance markers.

Fast and automated detection of common carbapenemase genes using multiplex real-time PCR on the BD MAX™ system

Fast detection of carbapenemases in Gram-negative bacilli is necessary for accurate antibiotic treatment, prevention of further spreading and surveillance purposes. We analyzed the current occurrence of gene variants and designed two multiplex PCRs with hydrolysis probes. The assay was developed for the BD MAX™ system that combines DNA extraction and PCR in a fully automated procedure providing results within 3 h and was evaluated for detection of carbapenemases from bacterial isolates and directly from rectal swabs. The assay has a theoretic coverage of 97.1% for carbapenemases detected during the last years by the German National Reference Laboratory (NRL). A collection of 151 isolates from the NRL was used and all carbapenemase-positive bacteria (58/58) were identified correctly. The direct-PCR on rectal swabs revealed additional carbapenemase genes in 7 samples that were not identified by the culture-based method used as reference method. The assay allows detection of carbapenemases from clinical isolates and might also help in rapid detection directly from rectal samples.

Multiple antibiotic resistance and DNA methylation in Enterobacteriaceae isolates from different environments

Antibiotic resistant bacteria with diverse resistance phenotypes and genotypes are ubiquitous in the environments that have become a global health concern. The role of DNA methylation in the dissemination of antibiotic resistance among different environments is currently unclear. We recovered 646 Enterobacteriaceae (Eb) isolates from hospital, livestock manure, municipal wastewater-treatment plants, river sediment and soil for comprehensive analysis of resistance phenotypes, β-lactamase genes, integrons, integron-associated gene cassettes and the levels of DNA methylation. Antibiotic susceptibility testing revealed that approximately 87.31 % isolates were multidrug resistant Eb. The β-lactamase genes were positively detected in 473 isolates with greater diversity in human or animal sourced Eb, while its prevalence was found to be highest in the Eb isolates from the natural environments. Forty-three gene cassettes (28 different types mediated by intI1) were detected in 53 (19.63 %) isolates, with greater diversity in Eb isolates from hospital and livestock manure. The multiple antibiotic resistance index of single strain was positively correlated with the 5-methylcytosine and showed a negative correlation with 6-methylademine. We conclude that the development of antibiotic resistance could possibly be coupled with DNA methylation, which might enhance the antimicrobial resistance and survival capacity of Eb.

A Lateral Flow Immunoassay for the Rapid Identification of CTX-M-Producing Enterobacterales from Culture Plates and Positive Blood Cultures

We have developed a lateral flow immunoassay (LFIA), named NG-Test CTX-M MULTI (NG-Test), to detect group 1, 2, 8, 9, 25 CTX-M producers from agar plates and from positive blood cultures in less than 15 min. The NG-Test was validated retrospectively on 113 well-characterized enterobacterial isolates, prospectively on 102 consecutively isolated ESBL-producers from the Bicêtre hospital and on 100 consecutive blood cultures positive with a gram-negative bacilli (GNB). The NG-Test was able to detect all CTX-M producers grown on the different agar plates used in clinical microbiology laboratories. No false positive nor negative results were observed. Among the 102 consecutive ESBL isolates, three hyper mucous isolates showed an incorrect migration leading to invalid results (no control band). Using an adapted protocol, the results could be validated. The NG-Test detected 99/102 ESBLs as being CTX-Ms. Three SHV producers were not detected. Among the 100 positive blood cultures with GNB tested 10/11 ESBL-producers were detected (8 CTX-M-15, 2 CTX-M-27). One SHV-2-producing-E. cloacae was missed. The NG-Test CTX-M MULTI showed 100% sensitivity and specificity with isolates cultured on agar plates and was able to detect 98% of the ESBL-producers identified in our clinical setting either from colonies or from positive blood cultures.

Evaluation of the "AMR Direct Flow Chip Kit" DNA microarray for detecting antimicrobial resistance genes directly from rectal and nasopharyngeal clinical samples upon ICU admission

INTRODUCTION

Prompt detection of antibiotic resistance genes in healthcare institutions is of utmost importance in tackling the spread of multi-drug resistant micro-organisms. We evaluated the Antimicrobial Resistance (AMR) Direct Flow Chip Kit versus phenotypic screening assays for rectal and nasopharyngeal specimens upon ICU admission.

METHODS

A total of 184 dual specimens (92 rectal and 92 nasopharyngeal swabs) from 92 patients were collected from 11/2017 to 8/2018. All swabs were subjected to both AMR and phenotypic tests according to their origin. The degree of agreement of the two methods was assessed by the kappa coefficient.

RESULTS

The kappa coefficient showed perfect agreement for MRSA, ESBLs, oxacillinases and vancomycin resistance genes (1.000, p<0.01) and very good agreement for mecA-positive CoNS, KPC-carbapenemases and metallo-beta-lactamases (0.870, p<0.01; 0.864, p<0.01; and 0.912, p<0.01, respectively).

CONCLUSION

The AMR Direct Flow Chip Kit is a useful alternative to phenotypic testing for rapid detection of resistance markers.

Rapid determination of carbapenem resistance by low-cost colorimetric methods: Propidium Iodide and alamar blue staining

Carbapenems are a class of β-lactam antibiotics with a broad antimicrobial activity spectrum. Owing to their sturdy structures resistant to most β-lactamases, they have been regarded as one of the last-resort antibiotics for combating multidrugresistant bacterial infections. However, the emergence of carbapenem resistance increases predominantly in nosocomial pathogens. To prevent spread of carbapenem resistance in early stages, it is imperative to develop rapid diagnostic tests that will substantially reduce the time and cost in determining carbapenem resistance. Thus, we devised a staining-based diagnostic method applicable to three different Gram-negative pathogens of Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae, all with the high potential to develop carbapenem resistance. Regardless of the resistance mechanisms presented by bacterial species and strains, double staining with propidium iodide (PI) and alamar blue (AB) identified resistant bacteria with an average sensitivity of 95.35%, 7 h after imipenem treatments in 343 clinical isolates. Among the three species tested, A. baumannii showed the highest diagnostic sensitivity of 98.46%. The PI and ABmediated staining method could be a promising diagnostic method with high-throughput efficacy and low cost.

Characterization of blaNDM-1- and blaSHV-12-Positive IncX3 Plasmid in an Enterobacter Hormaechei New Sequence Type 1000 from China

Purpose

Carbapenem-resistant Enterobacter cloacae complex has been reported worldwide and becomes a new challenge for clinical management. The present study was to characterize the IncX3 plasmid encoding bla_NDM-1 and bla_SHV-12 gene in E. hormaechei sequence.

Materials and Methods

EcHK001 was recovered from the sputum sample of a patient. Species identification and antimicrobial susceptibility testing were performed using the VITEK 2 system, while further classification was carried out by hsp60 typing. The presence of NDM-1 was detected by PCR and sequencing. Conjugation experiments and southern blotting were carried out to determine the transferability of the NDM-1-carrying plasmid. Whole-genome sequencing and analysis were conducted to better understand the molecular characteristics of the multi-drug resistant isolate.

Results

Strain EcHK001 was classified as E. hormaechei of new sequence type 1000. Multiple drug-resistant genes were detected. The bla_NDM-1 and bla_SHV-12 genes were located on a self-transferable IncX3 plasmid. Synonymous mutations were identified in the genes encoding TEM-1 and ACT-17. Phylogenetic analysis indicated that EcHK001 clustered into a different clade from domestic strains.

Conclusion

The rapid spread of the recurrent IncX3 plasmid highlights the need for continuous surveillance of the NDM-1 dissemination. The presence of mutations in existing carbapenem-resistant genes may generate potential new variants and raise serious challenges for clinical treatment.

Antibiotic Resistance of LACTOBACILLUS Strains

The study provides phenotypic and molecular analyses of the antibiotic resistance in 20 Lactobacillus strains including 11 strains newly isolated from fermented plant material. According to the results of disc diffusion method, 90% of tested lactobacilli demonstrated sensitivity to clindamycin and 95% of strains were susceptible to tetracycline, erythromycin, and rifampicin. Ampicillin and chloramphenicol were found to inhibit all bacteria used in this study. The vast majority of tested strains revealed phenotypic resistance to vancomycin, ciprofloxacin, and aminoglycosides. Most of Lactobacillus strains showed high minimum inhibitory concentrations (MICs) of cefotaxime, ceftriaxone, and cefazolin and therefore were considered resistant to cephalosporins. All the strains exhibited multidrug resistance. The occurrence of resistance genes was associated with phenotypic resistance, with the exception of phenotypically susceptible strains that contained genes for tetracycline (tetK, tetL) and erythromycin (ermB, mefA) resistance. The vanX gene for vancomycin resistance was among the most frequently identified among the lactobacilli (75% of strains), but the occurrence of the parC gene for ciprofloxacin resistance was sporadic (20% of strains). Our results mainly evidence the intrinsic nature of the resistance to aminoglycosides in lactobacilli, though genes for enzymatic modification of streptomycin aadA and aadE were found in 20% of tested strains. The occurrence of extended spectrum beta-lactamases (ESBL) was unknown in Lactobacillus, but our results revealed the blaTEM gene in 80% of strains, whereas blaSHV and blaOXA-1 genes were less frequent (20% and 15% of strains, respectively).

Molecular Epidemiology of Ceftriaxone Non-Susceptible Enterobacterales Isolates in an Academic Medical Center in the United States

Background

Knowledge of whether Enterobacterales are not susceptible to ceftriaxone without understanding the underlying resistance mechanisms may not be sufficient to direct appropriate treatment decisions. As an example, extended-spectrum β-lactamase (ESBL)–producing organisms almost uniformly display nonsusceptibility to ceftriaxone. Regardless of susceptibility to piperacillin-tazobactam or cefepime, carbapenem antibiotics are the treatment of choice for invasive infections. No such guidance exists for ceftriaxone-nonsusceptible organisms with mechanisms other than ESBL production. We sought to investigate the molecular epidemiology of ceftriaxone-nonsusceptible Enterobacterales.

Methods

All consecutive Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, or Proteus mirabilis clinical isolates with ceftriaxone minimum inhibitory concentrations (MICs) of ≥2 mcg/mL from unique patients at a United States hospital over an 8-month period were evaluated for β-lactamase genes using a DNA microarray–based assay.

Results

Of 1929 isolates, 482 (25%) had ceftriaxone MICs of ≥2 mcg/mL and were not resistant to any carbapenem antibiotics. Of the 482 isolates, ESBL (bla_CTX-M, bla_SHV, bla_TEM) and/or plasmid-mediated ampC (p-ampC) genes were identified in 376 (78%). ESBL genes were identified in 310 (82.4%), p-ampC genes in 2 (0.5%), and both ESBL and p-ampC genes in 64 (17.0%) of the 376 organisms. There were 211 (56%), 120 (32%), 41 (11%), and 4 (1%) isolates with 1, 2, 3, or ≥4 ESBL or p-ampC genes. The most common ESBL genes were of the bla_CTX-M-1 group (includes bla_CTX-M-15), and the most common p-ampC gene was bla_CMY-2.

Conclusions

There is considerable diversity in the molecular epidemiology of ceftriaxone-nonsusceptible Enterobacterales. An understanding of this diversity can improve antibiotic decision-making.

Emerging strategies for the noninvasive diagnosis of nosocomial pneumonia

Introduction: Hospital-acquired pneumonia is a common and therapeutically challenging diagnosis that can lead to severe sepsis, critical illness, and respiratory failure. In this review, we focus on efforts to enhance microbiological diagnosis of hospital-acquired pneumonia, including ventilator-associated pneumonia.

Areas covered: A systematic literature review was conducted by searching Medline from inception to December 2018, including hand-searching of the reference lists for additional studies. The search strategy comprised the following common search terms: hospital pneumonia OR nosocomial pneumonia OR noninvasive OR molecular diagnostic tests (OR point-of-care systems OR VOC [i.e. volatile organic compounds]) OR rapid (or simple or quick test), including brand names for the most common commercial tests.

Expert opinion: In recent years, the microbiological diagnosis of respiratory pathogens has improved significantly by the development and implementation of molecular diagnostic tests for pneumonia. Real-time polymerase chain reaction, hybridization, and mass spectrometry-based platforms dominate the scene, with microarray-based assays, multiplex polymerase chain reaction, and MALDI-TOF mass spectrometry capable of detecting the determinants of antimicrobial resistance (mainly β-lactamase genes). Introducing these assays into routine clinical practice for rapid identification of the causative microbes and their resistance patterns could transform the care of pneumonia, improving antimicrobial selection, de-escalation, and stewardship.

Laboratory and Clinical Evaluation of DNA Microarray for the Detection of Carbapenemase Genes in Gram-Negative Bacteria from Hospitalized Patients

Background

The prevalence of a variety of carbapenemases in Gram-negative bacteria (GNB) has posed a global threat on clinical control and management. Monitoring and controlling the carbapenemase-producing GNB became imperative tasks for many healthcare centers. The aim of this study was to develop a high-throughput, specific, sensitive, and rapid DNA microarray-based method for the diagnosis, phenotypic confirmation, and molecular epidemiological study of carbapenemase genes.

Methods

We targeted a panel of eight carbapenemase genes, including bla_KPC, bla_NDM-1, bla_OXA-23, bla_OXA-48, bla_OXA-51, bla_IMP, bla_VIM, and bla_DIM for detection. Ultrasensitive chemiluminescence (CL) detection method was developed and used to simultaneously detect eight carbapenemase genes, and plasmids were established as positive or limit of detection (LOD) reference materials. Antibiotic susceptibility was determined by disk diffusion according to Clinical and Laboratory Standards Institute (CLSI) guidelines in order to screen clinical isolates resistant to carbapenem antibiotics as well as Sanger sequencing which was used to confirm the reliability of the results presented by DNA microarray.

Results

Eight carbapenemase genes could be detected with high sensitivity and specificity. The absolute LOD of this strategy to detect serially diluted plasmids of eight carbapenemase genes was 10²- 10³copies/μL. Then, 416 specimens collected from hospital were detected and the results showed 96.6% concordance between the phenotypic and microarray tests. Compared with Sanger sequencing, a specificity and sensitivity of 100% were recorded for bla_NDM-1, bla_IMP, bla_VIM, and bla_DIM genes. The specificity for bla_KPC, bla_OXA-23, bla_OXA-48, and bla_OXA-51 genes was 100% and the sensitivity was 98.5%, 97.6%, 95.7%, and 97.9%, respectively. The overall consistency rate between the sequencing and microarray is 97.8%.

Conclusions

The proposed ultrasensitive CL imaging DNA hybridization has high specificity, sensitivity, and reproducibility and could detect and differentiate clinical specimens that carried various carbapenemase genes, suggesting that the method can conveniently be customized for high-throughput detection of the carbapenemase-producing GNB and can be easily adapted for various clinical applications.

Evaluation of the DNA microarray "AMR Direct Flow Chip Kit" for detection of antimicrobial resistance genes from Gram-positive and Gram-negative bacterial isolated colonies

INTRODUCTION

The AMR Direct Flow Chip assay allows the simultaneous detection of a large variety of antibiotic resistance genetic markers. To assess this kit's performance, we use isolated colonies as starting material. The assay has been approved by the European Economic Area as a suitable device for in vitro diagnosis (CE IVD) using clinical specimens.

METHODS

A total of 210 bacterial isolates harbouring either one or more antimicrobial resistance genes including plasmid-encoded extended-spectrum β-lactamases (SHV, CTX-M) and carbapenemases (GES, SME, KPC, NMC/IMI, SIM, GIM, SPM, NDM, VIM, IMP, and OXA), mecA, vanA and vanB, and 30 controls were included.

RESULTS

The assay displayed a sensitivity and specificity of 100% for all target genes included in the array.

CONCLUSION

The AMR Direct Flow Chip Kit is an accurate assay for detecting genes which commonly confer resistance to β-lactams and vancomycin from isolated colonies in culture of Gram-positive and Gram-negative bacteria.

NDM Metallo-β-Lactamases and Their Bacterial Producers in Health Care Settings

New Delhi metallo-β-lactamase (NDM) is a metallo-β-lactamase able to hydrolyze almost all β-lactams. Twenty-four NDM variants have been identified in >60 species of 11 bacterial families, and several variants have enhanced carbapenemase activity. Klebsiella pneumoniae and Escherichia coli are the predominant carriers of bla _NDM, with certain sequence types (STs) (for K. pneumoniae, ST11, ST14, ST15, or ST147; for E. coli, ST167, ST410, or ST617) being the most prevalent. NDM-positive strains have been identified worldwide, with the highest prevalence in the Indian subcontinent, the Middle East, and the Balkans. Most bla _NDM-carrying plasmids belong to limited replicon types (IncX3, IncFII, or IncC). Commonly used phenotypic tests cannot specifically identify NDM. Lateral flow immunoassays specifically detect NDM, and molecular approaches remain the reference methods for detecting bla _NDM Polymyxins combined with other agents remain the mainstream options of antimicrobial treatment. Compounds able to inhibit NDM have been found, but none have been approved for clinical use. Outbreaks caused by NDM-positive strains have been reported worldwide, attributable to sources such as contaminated devices. Evidence-based guidelines on prevention and control of carbapenem-resistant Gram-negative bacteria are available, although none are specific for NDM-positive strains. NDM will remain a severe challenge in health care settings, and more studies on appropriate countermeasures are required.

Systematic review in South Africa reveals antibiotic resistance genes shared between clinical and environmental settings

A systematic review was conducted to determine the distribution and prevalence of antibiotic-resistant bacteria (ARB), antimicrobial-resistant genes (ARGs), and antimicrobial-resistant gene determinants (ARGDs) in clinical, environmental, and farm settings and to identify key knowledge gaps in a bid to contain their spread. Fifty-three articles were included. The prevalence of a wide range of antimicrobial-resistant bacteria and their genes was reviewed. Based on the studies reviewed in this systematic review, mutation was found to be the main genetic element investigated. All settings shared 39 ARGs and ARGDs. Despite the fact that ARGs found in clinical settings are present in the environment, in reviewed articles only 12 were found to be shared between environmental and clinical settings; the inclusion of farm settings with these two settings increased this figure to 32. Data extracted from this review revealed farm settings to be one of the main contributors of antibiotic resistance in healthcare settings. ARB, ARGs, and ARGDs were found to be ubiquitous in all settings examined.

Evaluation of the Amplidiag CarbaR+VRE Kit for Accurate Detection of Carbapenemase-Producing Bacteria

As carbapenemase-producing Gram-negative bacilli (CP-GNB) (Enterobacteriaceae, Pseudomonadaceae, and Acinetobacter spp.) are becoming a major public health issue, there is an urgent need for accurate and fast diagnostic tests. The Amplidiag CarbaR+VRE assay is a multiplex nucleic acid-based in vitro diagnostic test intended for the detection of CP-GNB and vancomycin-resistant enterococci (VRE) from cultured colonies. We have evaluated its ability to detect carbapenemase genes in 100 well-characterized GNB and in 200 consecutive enterobacterial isolates with reduced susceptibility to carbapenems that were referred to the French National Reference Center for carbapenem resistance. The assay has been validated on purified DNA but also directly on colonies. The Amplidiag CarbaR+VRE assay could detect all KPC, NDM, VIM, IMP, and OXA-48-like variants tested and all acquired carbapenem-hydrolyzing oxacillinases from Acinetobacter baumannii (OXA-23, OXA-24/-40, and OXA-58) as well as the overexpressed chromosomally encoded OXA-51-like β-lactamase associated with an upstream inserted ISAba1 However, as claimed by the manufacturer, other carbapenemases such as GES-like carbapenemases (GES-2, GES-5, and GES-14), GIM-1, AIM-1, SPM-1, DIM-1, OXA-198 in Pseudomonas aeruginosa, or OXA-143-like in A. baumannii were not detected. Amplidiag CarbaR+VRE's performance values were high (100% sensitivity and 99% specificity) as it could detect the five major carbapenemases-NDM, VIM, IMP, KPC, and OXA-48-as well as OXA-type carbapenemases from Acinetobacter spp. that are currently emerging also among Proteus mirabilis and other enterobacterial isolates. It can provide a result directly from colonies growing on Mueller-Hinton (MH) agar or on selective screening medium in less than 2 h. Further evaluations are now necessary to determine the performance values directly on rectal swabs.

Carbapenem Resistance: A Review

Carbapenem resistance is a major and an on-going public health problem globally. It occurs mainly among Gram-negative pathogens such as Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii, and may be intrinsic or mediated by transferable carbapenemase-encoding genes. This type of resistance genes are already widespread in certain parts of the world, particularly Europe, Asia and South America, while the situation in other places such as sub-Saharan Africa is not well documented. In this paper, we provide an in-depth review of carbapenem resistance providing up-to-date information on the subject.

Antibiotic resistance of pathogenic Acinetobacter species and emerging combination therapy

The increasing antibiotic resistance of Acinetobacter species in both natural and hospital environments has become a serious problem worldwide in recent decades. Because of both intrinsic and acquired antimicrobial resistance (AMR) against last-resort antibiotics such as carbapenems, novel therapeutics are urgently required to treat Acinetobacter-associated infectious diseases. Among the many pathogenic Acinetobacter species, A. baumannii has been reported to be resistant to all classes of antibiotics and contains many AMR genes, such as bla _ADC (Acinetobacter-derived cephalosporinase). The AMR of pathogenic Acinetobacter species is the result of several different mechanisms, including active efflux pumps, mutations in antibiotic targets, antibiotic modification, and low antibiotic membrane permeability. To overcome the limitations of existing drugs, combination theraphy that can increase the activity of antibiotics should be considered in the treatment of Acinetobacter infections. Understanding the molecular mechanisms behind Acinetobacter AMR resistance will provide vital information for drug development and therapeutic strategies using combination treatment. Here, we summarize the classic mechanisms of Acinetobacter AMR, along with newly-discovered genetic AMR factors and currently available antimicrobial adjuvants that can enhance drug efficacy in the treatment of A. baumannii infections.

The Changing Role of the Clinical Microbiology Laboratory in Defining Resistance in Gram-negatives

The evolution of resistance in Gram-negatives has challenged the clinical microbiology laboratory to implement new methods for their detection. Multidrug-resistant strains present major challenges to conventional and new detection methods. More rapid pathogen identification and antimicrobial susceptibility testing have been developed for use directly on specimens, including fluorescence in situ hybridization tests, automated polymerase chain reaction systems, microarrays, mass spectroscopy, next-generation sequencing, and microfluidics. Review of these methods shows the advances that have been made in rapid detection of resistance in cultures, but limited progress in direct detection from specimens.

Evaluation of Carbapenem Resistance Mechanisms and Its Association with Pseudomonas aeruginosa Infections in the Northwest of Iran

The aims of this study were to determine carbapenem resistance mechanisms, molecular epidemiological relationship, clinical impact, and patient outcome of carbapenem-resistant Pseudomonas aeruginosa (CRPA) infections. A total of 42 nonduplicated CRPA were recovered from Urmia, Iran. Antimicrobial susceptibility tests were carried out using phenotypic methods. The carbapenem resistance mechanisms such as carbapenemase genes, efflux pump hyperexpression, AmpC overproduction, and OprD gene downregulation were determined by phenotypic and molecular methods. Eighteen metallo-β-lactamase (MBL) producer isolates were found to be sensitive to amikacin. Among the CRPA, 52.3%, 26.1%, 26.1%, and 59.5% were identified as carbapenemase, efflux pump hyperexpression, AmpC overproduction, and reduced expression OprD gene, respectively. Random Amplified Polymorphic DNA analysis yielded 25 distinct profiles. Most MBL-positive isolates were recovered from patients hospitalized in urology and internal wards with urinary tract infections. Most of the strains showed downregulation of porin. The clonal distribution of the strains was related to carbapenem resistance mechanisms (most of MBL producers belong to the same clones) and the same hospital wards where the isolates were collected. The study demonstrates that the main risk factor of MBL-related infections was hospitalization in non-intensive wards. Amikacin was considered a very efficient antibiotic to treatment of MBL-producing CRPA isolates. Our results showed that OprD downregulation and IMP-type MBL are the main carbapenem resistance mechanisms in CRPA isolates from northwest of Iran.

Rapid detection of carbapenemase-producing Klebsiella pneumoniae strains derived from blood cultures by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS)

Background

Carbapenemase-producing Enterobacteriaceae (CPE), particularly carbapenemase-producing Klebsiella pneumoniae isolates, are important causative agents of nosocomial infections associated with significant mortality rates mostly in critical wards. The rapid detection and typing of these strains is critical either for surveillance purposes and to prevent outbreaks and optimize antibiotic therapy. In this study, the MALDI-TOF MS method was used to detect rapidly these isolates from blood cultures (BCs) and to obtain proteomic profiles enable to discriminate between carbapenemase-producing and non-carbapenemase-producing strains.

Results

Fifty-five K. pneumoniae strains were tested. Identification and carbapenemase-production detection assay using Ertapenem were performed both from bacterial pellets extracted directly from BCs flasks and from subcultures of these strains. For all isolates, a complete antimicrobial susceptibility testing and a genotypic characterization were performed.

We found 100% agreement between the carbapenemase-producing profile generated by MALDI TOF MS and that obtained using conventional methods. The assay detected and discriminated different carbapenemase-producing K. pneumoniae isolates within 30 min to 3 h after incubation with Ertapenem.

Conclusions

MALDI-TOF MS is a promising, rapid and economical method for the detection of carbapenemase-producing K. pneumoniae strains that could be successfully introduced into the routine diagnostic workflow of clinical microbiology laboratories.

Current methods for the identification of carbapenemases

Detection of carbapenemases in clinical microbiology labs is a challenging issue. Comparison of the results of susceptibility testing with the breakpoint values of carbapenems is the first step in the screening of carbapenemase producers. To date, screening of carbapenemase-producing (CP) bacteria has been mostly performed by a selective medium. Although these media are practical for the detection of most CP isolates, the inoculated plates have to be incubated overnight. Subsequently, we need the confirmation of the carbapenemase producers present in the culture medium by additional testing [e.g. inhibition studies with liquid or solid media, modified Hodge test (MHT), or gradient strips], which can take up to another 48 hours. Despite the lack of discrimination between the three different classes of carbapenemases (KPC, MBL and OXA) and difficulties in the interpretation of the results, the MHT is usually deemed as the phenotypic reference method for the confirmation of carbapenemase production. Molecular techniques, such as real-time polymerase chain reaction (PCR) assays, in contrast to phenotypic methods that are very time consuming, are faster and allow for the quick identification of carbapenemase genes. These techniques can detect and characterize carbapenemases, including NDM- and KPC-mediated resistance, which is critical for epidemiological investigations. The aim of this review is to gather a summary of the available methods for carbapenemase detection and describe the strengths and weaknesses of each method.

Antibiotic Susceptibilities and Genetic Characteristics of Extended-Spectrum Beta-Lactamase-Producing Escherichia coli Isolates from Stools of Pediatric Diarrhea Patients in Surabaya, Indonesia

The purpose of this study was to investigate extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli isolates from pediatric (aged 0 to 3 years) diarrhea patients in Surabaya, Indonesia, where this kind of survey is rare; our study included assessment of their antibiotic susceptibilities, as well as ESBL typing, multilocus sequence typing (MLST), and diarrheagenic E. coli (DEC)-typing. ESBL-producing E. coli were detected in 18.8% of all the samples. Many ESBL-producing E. coli had significantly lower susceptibility to gentamicin (p ＜ 0.0001) and the quinolones nalidixic acid (p＝0.004) and ciprofloxacin (p ＜ 0.0001) than non-producers. In ESBL-producing E. coli, 84.0% of strains expressed CTX-M-15 alone or in combination with other ESBL types. MLST revealed that 24.0% of ESBL-producers had sequence type 617, all of which expressed the CTX-M-15 gene; we also detected expression of 3 DEC-related genes: 2 enteroaggregative E. coli genes and 1 enteropathogenic E. coli gene. In conclusion, CTX-M-15-type ESBL-producing E. coli ST617 appear to have spread to Indonesia.

Cilastatin does not affect Carba NP test performance for detection of carbapenemase production in Enterobacteriaceae

The Carba NP test is a simple confirmation method for carbapenemase-producing Enterobacteriaceae (CPE) but reagents have to be freshly prepared as imipenem sodium salt is unstable. We evaluated the Carba NP test performance based on a commercially available 10-fold cheaper drug formulation containing cilastatin against 217 CPE and 78 non-CPE isolates with reduced meropenem susceptibility. Specificity and sensitivity were 100 % and 98.6 %, respectively and 3 false negative results of blaVIM-1-producing Proteus mirabilis were reproducible with the RAPIDEC® Carba NP test. Cilastatin does not disturb test performance provided that the imipenem drug quantity is doubled.

Multiplex characterization of human pathogens including species and antibiotic-resistance gene identification

The efficient medical treatment of infections requires detailed information about the pathogens involved and potential antibiotic-resistance mechanisms. The dramatically increasing incidence of multidrug-resistant bacteria especially highlights the importance of sophisticated diagnostic tests enabling a fast patient-customized therapy. However, the current molecular detection methods are limited to either the detection of species or only a few antibiotic-resistance genes.In this work, we present a human pathogen characterization assay using a rRNA gene microarray identifying 75 species comprising bacteria and fungi. A statistical classifier was developed to facilitate the automated species identification. Additionally, the clinically most important β-lactamases were identified simultaneously in a 100-plex reaction using padlock probes and the same microarray. The specificity and sensitivity of the combined assay was determined using clinical isolates. The detection limit was 10(5) c.f.u. ml(-1), recovering 89 % of the detectable β-lactamase-encoding genes specifically. The total assay time was less than 7 hand the modular character of the antibiotic-resistance detection allows the easy integration of further genetic targets. In summary, we present a fast, highly specific and sensitive multiplex pathogen characterization assay.

Environmental persistence of OXA-48-producing Klebsiella pneumoniae in a French intensive care unit

The spread of carbapenemase-producing Gram-negative rods is an emerging global problem. This study describes the epidemiologic features of an outbreak caused by an environmental reservoir of OXA-48-producing Klebsiella pneumoniae caused by persistence of the bacteria during 20 months in an intensive care unit in France. This report emphasizes the importance of early environmental screening to interrupt the transmission of carbapenemase-producingEnterobacteriaceae.

Evaluation of the Check-Points Check MDR CT103 and CT103 XL Microarray Kits by Use of Preparatory Rapid Cell Lysis

Using a rapid bacterial lysis method, the Check MDR CT103 and CT103 XL microarrays demonstrated accuracies of 98.1% and 94.2%, respectively, for detection of known resistance genes in 108 multidrug-resistant Gram-negative bacilli. In 45 isolates, 49 previously unrecognized extended-spectrum β-lactamase or plasmid AmpC targets were detected and confirmed by conventional PCR.

Laboratory Detection and Clinical Implication of Oxacillinase-48 like Carbapenemase: The Hidden Threat

Carbapenemase producing Gram-negative pathogen is of great concern for physician. The challenging aspects are treatment option and infection control. Monitoring of respective carbapenemase resistance mechanism is necessary to prevent the outbreaks. Currently, the rapid emergence of oxacillinase (OXA-48) like is alarming. Increasing frequency of OXA-48 is seen than the classical carbapenemase (KPC, NDM, IMP, and VIM) across the world. The bla OXA-48 gene is commonly identified in Escherichia coli and Klebsiella pneumoniae. The transferrable plasmid of OXA-48 is associated with rapid spread and inter-species dissemination. In general, OXA-48-like enzymes weakly hydrolyzes both carbapenem and broad spectrum cephalosporins. Except OXA-163, which effectively hydrolyze cephalosporin. This poor hydrolytic profile obscures the detection of OXA-48-like. It may go undetected in routine diagnosis and complicates the treatment option. Co-production of OXA-48-like with CTX-M-15 and other carbapenemase (NDM, VIM) leads to the emergence of multidrug resistant strains.

Carbapenem-Resistant Enterobacteriaceae Infections in Children

Carbapenem-resistant Enterobacteriaceae (CRE) are an emerging global public health threat. Infections due to CRE are associated with significant morbidity and mortality. Few therapeutic options are available for treatment of these infections, and optimal antibiotic treatment regimens are unclear. Along with the rapidly increasing prevalence of CRE in the USA and worldwide, several studies have described the epidemiology of CRE in the adult population. While CRE are now also reported sporadically in children, there is a significant lack of data on the epidemiology, risk factors, treatment, and outcomes in this population. This article provides a comprehensive review of what is known to date about CRE, including clinical and molecular epidemiology, microbiologic diagnosis, antibiotic treatment options, and outcomes. In particular, this review will focus on the available data on CRE in the pediatric population.

Evaluation of a Commercial Multiplex PCR for Rapid Detection of Multi Drug Resistant Gram Negative Infections

Introduction:

Community and healthcare associated infections caused by multi-drug resistant gram negative organisms (MDR GN) represent a worldwide threat. Nucleic Acid Detection tests are becoming more common for their detection; however they can be expensive requiring specialised equipment and local expertise. This study was done to evaluate the utility of a commercial multiplex tandem (MT) PCR for detection of MDR GN.

Methods:

The study was done on stored laboratory MDR GN isolates from sterile and non-sterile specimens (n=126, out of stored 567 organisms). Laboratory validation of the MT PCR was done to evaluate sensitivity, specificity and agreement with the current phenotypic methods used in the laboratory. Amplicon sequencing was also done on selected isolates for assessing performance characteristics. Workflow and cost implications of the MT PCR were evaluated.

Results:

The sensitivity and specificity of the MT PCR were calculated to be 95% and 96.7% respectively. Agreement with the phenotypic methods was 80%. Major lack of agreement was seen in detection of AmpC beta lactamase in enterobacteriaceae and carbapenemase in non-fermenters. Agreement of the MT PCR with another multiplex PCR was found to be 87%. Amplicon sequencing confirmed the genotype detected by MT PCR in 94.2 % of cases tested. Time to result was faster for the MT PCR but cost per test was higher.

Conclusion:

This study shows that with carefully chosen targets for detection of resistance genes in MDR GN, rapid and efficient identification is possible. MT PCR was sensitive and specific and likely more accurate than phenotypic methods.

Molecular characterization of extended-spectrum beta-lactamases (ESBLs) produced by clinical isolates of Acinetobacter baumannii in Saudi Arabia

Background

Acinetobacter baumannii is a common opportunistic pathogen that causes major nosocomial infections in hospitals. In this study, we hypothesized a high prevalence of A. baumanni ESBL (extended-spectrum beta-lactamase) among all collected isolates.

Methods

A. baumannii isolates (n = 107) from ICU (Intensive care unit) of local hospitals in Makkah were phenotypically and genotypically characterized. The identity and antibiotic susceptibility of A. baumannii strains were determined using the Vitek-2 system. The identified ESBL producers were further analyzed by PCR and sequencing followed by MLST typing. bla_TEM, bla_SHV, and the bla_CTX-M-group genes 1, 2, 8, 9, and 25 were investigated. Furthermore, bla_OXA51-like and bla_OXA23-like genes were also examined in the carbapenem-resistant A. baumannii isolates.

Results

Our data indicated a high prevalence of A. baumannii ESBL producers among the collected strains. Of the 107 A. baumannii isolates, 94 % were found to be resistant to cefepime and ceftazidime, and aztreonam using the Vitek 2 system. The genes detected encoded TEM, OXA-51-like and OXA-23-like enzymes, and CTX-M-group proteins 1, 2, 8, 9, and 25. MLST typing identified eight sequence type (ST) groups. The most dominant STs were ST195 and ST557 and all of them belong to worldwide clonal complex (CC) 2.

Conclusions

This study has shown that there is a high prevalence of antimicrobial resistance in A. baumannii. The diversity of STs may suggest that new ESBL strains are constantly emerging. The molecular diversity of the ESBL genes in A. baumannii may have contributed to the increased antimicrobial resistance among all isolates.

Rapid Electrochemical Detection of New Delhi Metallo-beta-lactamase Genes To Enable Point-of-Care Testing of Carbapenem-Resistant Enterobacteriaceae

The alarming rate at which antibiotic resistance is occurring in human pathogens causes a pressing need for improved diagnostic technologies aimed at rapid detection and point-of-care testing to support quick decision making regarding antibiotic therapy and patient management. Here, we report the successful development of an electrochemical biosensor to detect bla(NDM), the gene encoding the emerging New Delhi metallo-beta-lactamase, using label-free electrochemical impedance spectroscopy (EIS). The presence of this gene is of critical concern because organisms harboring bla(NDM) tend to be multiresistant, leaving very few treatment options. For the EIS assay, we used a bla(NDM)-specific PNA probe that was designed by applying a new approach that combines in silico probe design and fluorescence-based DNA microarray validation with electrochemical testing on gold screen-printed electrodes. The assay was successfully demonstrated for synthetic targets (LOD = 10 nM), PCR products (LOD = 100 pM), and direct, amplification-free detection from a bla(NDM)-harboring plasmid. The biosensor's specificity, preanalytical requirements, and performance under ambient conditions were demonstrated and successfully proved its suitability for further point-of-care test development.

Detection of expanded-spectrum β-lactamases in Gram-negative bacteria in the 21st century

Emerging β-lactamase-producing-bacteria (ESBL, AmpC and carbapenemases) have become a serious problem in our community due to their startling spread worldwide and their ability to cause infections which are difficult to treat. Diagnosis of these β-lactamases is of clinical and epidemiological interest. Over the past 10 years, several methods have been developed aiming to rapidly detect these emerging enzymes, thus preventing their rapid spread. In this review, we describe the range of screening and detection methods (phenotypic, molecular and other) for detecting these β-lactamases but also whole genome sequencing as a tool for detecting the genes encoding these enzymes.

Development of a novel real-time PCR assay with high-resolution melt analysis to detect and differentiate OXA-48-Like β-lactamases in carbapenem-resistant Enterobacteriaceae

The rapid global spread of carbapenem-resistant Enterobacteriaceae (CRE) poses an urgent threat to public health. More than 250 class D β-lactamases (OXAs) have been described in recent years, with variations in hydrolytic activity for β-lactams. The plasmid-borne OXA-48 β-lactamase and its variants are identified only sporadically in the United States but are common in Europe. Recognition of these OXA-48-like carbapenemases is vital in order to control their dissemination. We developed a real-time PCR assay based on high-resolution melt analysis, using bla OXA-48-like-specific primers coupled with an unlabeled 3'-phosphorylated oligonucleotide probe (LunaProbe) homologous to OXA-48-like carbapenemase genes. The assay was validated using genomic DNA from 48 clinical isolates carrying a variety of carbapenemase genes, including bla KPC, bla SME, bla IMP, bla NDM-1, bla VIM, bla OXA-48, bla OXA-162, bla OXA-181, bla OXA-204, bla OXA-244, bla OXA-245, and bla OXA-232. Our assay identified the presence of bla OXA-48-like β-lactamase genes and clearly distinguished between bla OXA-48 and its variants in control strains, including between bla OXA-181 and bla OXA-232, which differ by only a single base pair in the assay target region. This approach has potential for use in epidemiological investigations and continuous surveillance to help control the spread of CRE strains producing OXA-48-like enzymes.