Use of Cepheid Xpert Carba-R® for Rapid Detection of Carbapenemase-Producing Bacteria in Abdominal Septic Patients Admitted to Intensive Care Unit

Carbapenemase producing Gram negative bacteria: Review of resistance and detection methods

Gram negative bacilli that are carbapenem resistant have emerged and are spreading worldwide. Infections caused by carbapenem resistant isolates posses a significant threat due to their high morbidity and mortality rates. Carbapenemases production by multi-drug resistant pathogens severely restricts treatment choices for illnesses caused by bacteria that are resistant to both carbapenems and majority of β-lactam antibiotics. Various phenotypic and genotypic methods for identification can distinguish between different classes of carbapenemase and identify pathogens that are resistant to carbapenems. The establishment of a quick, accurate and reliable test for identifying the clinical strains that produce the carbapenemase enzyme is essential for optimum diagnosis of microbial pathogens and management of the global rise in the prevalence of carbapenemase producing bacterial strains. The aim of this review was to summarize the mechanisms of carbapenem resistance and to provide an overview of different carbapenemase detection methods for carbapenem resistant Gram negative bacilli.

Rapid Point-of-Care PCR Testing of Drug-Resistant Strains on Endotracheal Aspirate Samples: A Repurposed Effective Tool in the Stepwise Approach of Healthcare-Acquired Pneumonia-A Pilot Study

Healthcare-associated pneumonia (HCAP) is a common nosocomial infection with high morbidity and mortality. Culture-based detection of the etiologic agent and drug susceptibility is time-consuming, potentially leading to the inadequate use of broad-spectrum empirical antibiotic regimens. The aim was to evaluate the diagnostic capabilities of rapid point-of-care multiplex polymerase chain reaction (PCR) assays from the endotracheal aspirate of critically ill patients with HCAP. A consecutive series of 29 intensive care unit (ICU) patients with HCAP and a control group of 28 patients undergoing elective surgical procedures were enrolled in the study. The results of the PCR assays were compared to the culture-based gold standard. The overall accuracy of the PCR assays was 95.12%, with a sensitivity of 92.31% and a specificity of 97.67%. The median time was 90 min for the rapid PCR tests (p < 0.001), while for the first preliminary results of the cultures, it was 48 h (46-72). The overall accuracy for rapid PCR testing in suggesting an adequate antibiotic adjustment was 82.98% (95% CI 69.19-92.35%), with a specificity of 90% (95% CI 55.50-99.75%), a positive predictive value of 96.77% (95% CI 83.30-99.92%), and a negative predictive value of 56.25 (95% CII 29.88-80.25%). This method of rapid point-of-care PCR could effectively guide antimicrobial stewardship in patients with healthcare-acquired pneumonia.

Ceftazidime-Avibactam Treatment for Klebsiella pneumoniae Bacteremia in Preterm Infants in NICU: A Clinical Experience

Ceftazidime/avibactam (CAZ/AVI) is an antibiotic combination approved for the treatment of several infections caused by multi-drug resistant (MDR) Gram-negative bacteria. Neonates admitted to the Neonatal Intensive Care Unit (NICU) are at high risk of developing bacterial infections, and the choice of appropriate antibiotics is crucial. However, the use of antibiotics in neonates carries risks such as antibiotic resistance and disruption of gut microbiota. This study aimed to assess the safety and efficacy of CAZ/AVI in preterm infants admitted to the NICU. Retrospective data from preterm infants with Klebsiella pneumoniae bacteremia who received CAZ/AVI were analyzed. Clinical and microbiological responses, adverse events, and outcomes were evaluated. Eight patients were included in the study, all of whom showed clinical improvement and achieved microbiological cure with CAZ/AVI treatment. No adverse drug reactions were reported. Previous antibiotic therapies failed to improve the neonates' condition, and CAZ/AVI was initiated based on clinical deterioration and epidemiological considerations. The median duration of CAZ/AVI treatment was 14 days, and combination therapy with fosfomycin or amikacin was administered. Previous case reports have also shown positive outcomes with CAZ/AVI in neonates. However, larger trials are needed to further investigate the safety and efficacy of CAZ/AVI in this population.

Trends in Molecular Diagnosis of Nosocomial Pneumonia Classic PCR vs. Point-of-Care PCR: A Narrative Review

Nosocomial pneumonia is one of the most frequent hospital-acquired infections. One of the types of nosocomial pneumonia is ventilator-associated pneumonia, which occurs in endotracheally intubated patients in intensive care units (ICU). Ventilator-associated pneumonia may be caused by multidrug-resistant pathogens, which increase the risk of complications due to the difficulty in treating them. Pneumonia is a respiratory disease that requires targeted antimicrobial treatment initiated as early as possible to have a good outcome. For the therapy to be as specific and started sooner, diagnostic methods have evolved rapidly, becoming quicker and simpler to perform. Polymerase chain reaction (PCR) is a rapid diagnostic technique with numerous advantages compared to classic plate culture-based techniques. Researchers continue to improve diagnostic methods; thus, the newest types of PCR can be performed at the bedside, in the ICU, so-called point of care testing-PCR (POC-PCR). The purpose of this review is to highlight the benefits and drawbacks of PCR-based techniques in managing nosocomial pneumonia.

Empiric treatment of patients with sepsis and septic shock and place in therapy of cefiderocol: a systematic review and expert opinion statement

Carbapenem-resistant Gram-negative bacteria are frequent causes of sepsis and septic shock in intensive care unit (ICU) and thus considered a public health threat. Until now, the best available therapies consist of combinations of preexisting or new antibiotics with β-lactamase inhibitors (either new or preexisting). Several mechanisms of resistance, especially those mediated by metallo-β-lactamases (MBL), are responsible for the inefficacy of these treatments, leaving an unmet medical need. Intravenous cefiderocol has been recently approved by the American Food and Drug Administration (FDA) and European Medicines Agency (EMA) for the treatment of complicated urinary tract infections and nosocomial pneumonia due to Gram-negative, when limited therapeutical options are available. In addition, its ability to hijack bacterial iron uptake mechanisms makes cefiderocol stable against the whole Ambler β-lactamase inhibitors and increases the in vitro efficacy against Gram-negative pathogens (e.g., Enterobacterales spp., Pseudomonas aeruginosa, and Acinetobacter baumannii). Trials have already demonstrated their non-inferiority to comparators. In 2021, ESCMID guidelines released a conditional recommendation supporting the use of cefiderocol against metallo-β-lactamase-producing Enterobacterales and against Acinetobacter baumannii. This review provides the opinion of experts about the general management of empiric treatment of patients with sepsis and septic shock in the intensive care unit and detects the proper place in therapy of cefiderocol considering recent evidence sought through a systematic search.

Prevalence and Molecular Typing of Carbapenemase-Producing Enterobacterales among Newborn Patients in Italy

The spread of carbapenemase-producing Enterobacterales (CPE), especially Klebsiella pneumoniae (K. pneumoniae) and Escherichia coli (E. coli), is a serious public health threat in pediatric hospitals. The associated risk in newborns is due to their underdeveloped immune system and limited treatment options. The aim was to estimate the prevalence and circulation of CPE among the neonatal intensive units of a major pediatric hospital in Italy and to investigate their molecular features. A total of 124 CPE were isolated from rectal swabs of 99 newborn patients at Bambino Gesù Children’s Hospital between July 2016 and December 2019. All strains were characterized by antimicrobial susceptibility testing, detection of resistance genes, and PCR-based replicon typing (PBRT). One strain for each PBRT profile of K. pneumoniae or E. coli was characterized by multilocus-sequence typing (MLST). Interestingly, the majority of strains were multidrug-resistant and carried the blaNDM gene. A large part was characterized by a multireplicon status, and FII, A/C, FIA (15%) was the predominant. Despite the limited size of collection, MLST analysis revealed a high number of Sequence Types (STs): 14 STs among 28 K. pneumoniae and 8 STs among 11 E. coli, with the prevalence of the well-known clones ST307 and ST131, respectively. This issue indicated that some strains shared the same circulating clone. We identified a novel, so far never described, ST named ST10555, found in one E. coli strain. Our investigation showed a high heterogeneity of CPE circulating among neonatal units, confirming the need to monitor their dissemination in the hospital also through molecular methods.

Progressing Antimicrobial Resistance Sensing Technologies across Human, Animal, and Environmental Health Domains

The spread of antimicrobial resistance (AMR) is a rapidly growing threat to humankind on both regional and global scales. As countries worldwide prepare to embrace a One Health approach to AMR management, which is one that recognizes the interconnectivity between human, animal, and environmental health, increasing attention is being paid to identifying and monitoring key contributing factors and critical control points. Presently, AMR sensing technologies have significantly progressed phenotypic antimicrobial susceptibility testing (AST) and genotypic antimicrobial resistance gene (ARG) detection in human healthcare. For effective AMR management, an evolution of innovative sensing technologies is needed for tackling the unique challenges of interconnected AMR across various and different health domains. This review comprehensively discusses the modern state-of-play for innovative commercial and emerging AMR sensing technologies, including sequencing, microfluidic, and miniaturized point-of-need platforms. With a unique view toward the future of One Health, we also provide our perspectives and outlook on the constantly changing landscape of AMR sensing technologies beyond the human health domain.

Comparison of Carbapenem-Resistant Microbial Pathogens in Combat and Non-combat Wounds of Military and Civilian Patients Seen at a Tertiary Military Hospital, Philippines (2013-2017)

INTRODUCTION

Bacterial wound infections are a danger to both military and civilian populations. The nature of injury and infection associated with combat related wounds are important in guiding antibiotic prophylaxis and empiric treatment guidelines.

MATERIALS AND METHODS

The isolates were screened for drug-resistance by the MicroScan Walkaway Plus System using either the Negative Breakpoint Combo Panel (NBCP) 30 or 34 or Positive Breakpoint Combo Panel (PBPC) 20 or 23. Isolates with a minimum inhibitory concentration (MIC) of ≥8 μg/mL to imipenem and/or meropenem were tested for both carbapenemase production using the CarbaNP test and real-time PCR to determine molecular resistance mechanisms. Plasmid conjugation analysis was performed to define potential for horizontal gene transfer.

RESULTS

We characterized 634 bacterial wound isolates collected from September 2013 to December 2017 from patients seen at a Philippine military tertiary hospital presenting with combat or non-combat injuries [354 (military) and 280 (civilians)]. Staphylococcus aureus was the most predominant bacterial species isolated from wounds in both populations (104/634, 16%). A variety of Gram-negative bacterial species comprised 442/634 (70%) of the isolates identified, with the most prevalent shown to be Pseudomonas aeruginosa, Enterobacter cloacae, Klebsiella pneumoniae, Escherichia coli, and Acinetobacter sp. Carbapenemase production was detected in 34/442 (8%) Gram-negative isolates. Testing for molecular resistance mechanisms showed 32/34 (17 military, 15 civilian) wound isolates were blaNDM positive and 2 were blaVIM positive, with the two blaVIM isolates found in the civilian population. Plasmid conjugation of 14 blaNDM and 2 blaVIM positive wound isolates representatives showed 2/16 (13%) produced E. coli J53 transconjugants (E. coli from a civilian; E. cloacae from a military).

CONCLUSION

We describe in this study the wound bacterial and antibiotic resistance profile in the military (combat vs non-combat associated) and civilian population. We observed that, with the exception of Acinetobacter sp., resistance of prevalent Gram-negative bacterial species to imipenem or meropenem were not significantly different between the military and civilian populations. We also presented data on the prevalent bacterial species isolated from both combat and non-combat wounds in a military tertiary care hospital setting as well as the carbapenemase-encoding gene primarily responsible for carbapenem resistance as well as evidence of horizontal transfer via mobile genetic elements. Clinicians may use this information to guide empiric antibiotic coverage for the predominant organisms if wound culture results are not readily available.A prospective, longitudinal evaluation of the wound bacterial profile documenting the changing bacterial flora using higher resolution molecular strategies can provide a more comprehensive understanding of the diversity, composition, and abundance of bacterial composition of the wound microbial community from the time of injury, during the course of evacuation from the field to higher level of care facilities, and up to wound resolution.

Genotypes and prevalence of carbapenemase-producing Enterobacteriaceae and Pseudomonas aeruginosa in a hospital in Saudi Arabia

BACKGROUND

The molecular epidemiology of resistance of carbapenem-resistant Enterobacteriaceae (CRE) and Pseudomonas aeruginosa are important in the study of multidrug-resistant bacteria. We evaluate the prevalence of the different mechanisms of CRE in a hospital in Saudi Arabia.

METHODS

Carbapenem non-susceptible isolates of Enterobacteriaceae and Pseudomonas aeruginosa were tested by real-time PCR for the detection of genes responsible for beta-lactam resistance.

RESULTS

There were a total of 200 isolates with carbapenem non-susceptibility and these were Klebsiella pneumoniae (n=96, 48%), Escherichia coli (n=51, 25.5%) and Pseudomonas aeruginosa (n=45, 22.5%). The detected carbapenemases were oxacillinase-48 (OXA-48) (n=83, 41.5%), New Delhi metallo-β-lactamase (NDM) (n=19, 2.5%) and both NDM and OXA-48 (n=5, 2.5%). The other carbapenemases were imipenemase (n=1, 0.5%), Verona integrin encoded metallo-β-lactamase (n=6, 3%) and Klebsiella pneumoniae carbapenemase (n=1, 0.5%), but none were detected in 86 isolates (43%).

CONCLUSION

The most common carbapenemases were OXA-48 and a significant percentage had no detectable genes. These data will help in the selection of new antimicrobial therapies.

Nosocomial Pneumonia in the Era of Multidrug-Resistance: Updates in Diagnosis and Management

Nosocomial pneumonia (NP), including hospital-acquired pneumonia in non-intubated patients and ventilator-associated pneumonia, is one of the most frequent hospital-acquired infections, especially in the intensive care unit. NP has a significant impact on morbidity, mortality and health care costs, especially when the implicated pathogens are multidrug-resistant ones. This narrative review aims to critically review what is new in the field of NP, specifically, diagnosis and antibiotic treatment. Regarding novel imaging modalities, the current role of lung ultrasound and low radiation computed tomography are discussed, while regarding etiological diagnosis, recent developments in rapid microbiological confirmation, such as syndromic rapid multiplex Polymerase Chain Reaction panels are presented and compared with conventional cultures. Additionally, the volatile compounds/electronic nose, a promising diagnostic tool for the future is briefly presented. With respect to NP management, antibiotics approved for the indication of NP during the last decade are discussed, namely, ceftobiprole medocaril, telavancin, ceftolozane/tazobactam, ceftazidime/avibactam, and meropenem/vaborbactam.

Evaluation of Antibacterial Activity of Three Quaternary Ammonium Disinfectants on Different Germs Isolated from the Hospital Environment

BACKGROUND

The microbiological risk of the hospital environment, including inert surfaces, medical devices, and equipment, represents a real problem.

OBJECTIVE

This study is aimed at demonstrating and assessing the antibacterial activity of three synthetic disinfectants classified as quaternary ammoniums on different bacterial strains (Gram-negative and Gram-positive like Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus) isolated from the hospital environment. The reference strains included Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, and Pseudomonas aeruginosa ATCC 27853 used as negative control strains.

METHOD

Three quaternary ammonium disinfectants were tested: DDN9® (0.5%) which contains didecylmethylpolyoxyethylammonium propionate as an active substance, spray (0.4%) containing quaternary ammonium compounds, and Phagosurf ND® (0.4%) with didecyldimethylammonium chloride. Their effect was evaluated using the disk diffusion technique and the broth dilution methods, allowing the Minimum Inhibitory Concentration (MIC) and then the Minimum Bactericidal Concentration (MBC).

RESULT

Only the growth of Gram-positive bacteria and some strains of Gram-negative bacteria were inhibited by the three synthetic disinfectants. NDD9® demonstrated an antibacterial effect only against the Gram-positive strains (S. aureus and S. aureus ATCC 29213) with a MIC of 0.25 mg/ml. The disinfectant spray showed effect against all four strains including E. coli (9), S. aureus, E. coli ATCC 25922, and P. aeruginosa ATCC 27853 with an inhibitory concentration of 4 mg/ml, while the growth of S. aureus ATCC 29213 was inhibited at 2 mg/ml. The third disinfectant, Phagosurf ND®, inhibited only the growth of S. aureus ATCC 29213 at a MIC of 4 mg/ml.

CONCLUSION

This study is the first here in Morocco to evaluate the bacterial activity of products intended for the control of the healthcare environment. The results obtained on the three disinfectants tested reveal an ineffectiveness against some isolated strains from the hospital environment.

Differential DNA accessibility to polymerase enables 30-minute phenotypic β-lactam antibiotic susceptibility testing of carbapenem-resistant Enterobacteriaceae

The rise in carbapenem-resistant Enterobacteriaceae (CRE) infections has created a global health emergency, underlining the critical need to develop faster diagnostics to treat swiftly and correctly. Although rapid pathogen-identification (ID) tests are being developed, gold-standard antibiotic susceptibility testing (AST) remains unacceptably slow (1-2 d), and innovative approaches for rapid phenotypic ASTs for CREs are urgently needed. Motivated by this need, in this manuscript we tested the hypothesis that upon treatment with β-lactam antibiotics, susceptible Enterobacteriaceae isolates would become sufficiently permeabilized, making some of their DNA accessible to added polymerase and primers. Further, we hypothesized that this accessible DNA would be detectable directly by isothermal amplification methods that do not fully lyse bacterial cells. We build on these results to develop the polymerase-accessibility AST (pol-aAST), a new phenotypic approach for β-lactams, the major antibiotic class for gram-negative infections. We test isolates of the 3 causative pathogens of CRE infections using ceftriaxone (CRO), ertapenem (ETP), and meropenem (MEM) and demonstrate agreement with gold-standard AST. Importantly, pol-aAST correctly categorized resistant isolates that are undetectable by current genotypic methods (negative for β-lactamase genes or lacking predictive genotypes). We also test contrived and clinical urine samples. We show that the pol-aAST can be performed in 30 min sample-to-answer using contrived urine samples and has the potential to be performed directly on clinical urine specimens.

Innovative and rapid antimicrobial susceptibility testing systems

Antimicrobial resistance (AMR) is a major threat to human health worldwide, and the rapid detection and quantification of resistance, combined with antimicrobial stewardship, are key interventions to combat the spread and emergence of AMR. Antimicrobial susceptibility testing (AST) systems are the collective set of diagnostic processes that facilitate the phenotypic and genotypic assessment of AMR and antibiotic susceptibility. Over the past 30 years, only a few high-throughput AST methods have been developed and widely implemented. By contrast, several studies have established proof of principle for various innovative AST methods, including both molecular-based and genome-based methods, which await clinical trials and regulatory review. In this Review, we discuss the current state of AST systems in the broadest technical, translational and implementation-related scope.

Rapid Carbapenemase Detection With Xpert Carba-R V2 Directly On Positive Blood Vials

The rapid detection of carbapenemase allows implementation of infection control measures and adaptation of antibiotic therapy. We evaluated the performances of the Xpert Carba-R V2^® assay for the direct detection and identification of carbapenemase on positive blood cultures. We focused our evaluation on its detection capacity and on the risks of interference due to the patient’s blood. Isolates of several variants of OXA-48-like (n=10), KPC (n=10), NDM (n=11), VIM (n=7), IMP-1 (n=1) carbapenemases and 14 non carbapenemase-producing Enterobacteriaceae were tested. For each isolate (n=53), an aerobic vial was seeded, and incubated in Bactec Fx (Becton Dickinson^®) automate. When positive, the Xpert^® Carba-R-V2 assay was assessed for carbapenemase detection using 40 µl aliquot. Reproducibility tests were performed on a subset of 23 isolates using aerobic and anaerobic vials. Longer incubation time was also evaluated on 6 isolates. A complementary prospective study in real-time testing of patient-derived clinical samples on 20 additional positive blood vials with Gram negative bacilli on direct examination was performed. Perfect sensitivity and specificity (100%) were observed regardless of the carbapenemase type, the blood vials used and the time of incubation. Xpert^® Carba-R-V2 assay is suitable for the rapid detection of the main carbapenemase genes directly on positive blood vials. Its performances and rapid time analysis allow its use in routine to guide therapeutic choices and to implement infection control measures.

Multiplex polymerase chain reaction to diagnose bloodstream infections in patients after cardiothoracic surgery

Background

Sepsis and other infectious complications are major causes of mortality and morbidity in patients after cardiac surgery. Whereas conventional blood culture (BC) suffers from low sensitivity as well as a reporting delay of approximately 48–72 h, real-time multiplex polymerase chain reaction (PCR) based technologies like “SeptiFast” (SF) might offer a fast and reliable alternative for detection of bloodstream infections (BSI). The aim of this study was to compare the performance of SF with BC testing in patients suspected of having BSI after cardiac surgery.

Methods

Two hundred seventy-nine blood samples from 169 individuals with suspected BSI were analyzed by SF and BC. After excluding results attributable to contaminants, a comparison between the two groups were carried out. Receiver operating characteristic (ROC) curves were generated to determine the accuracy of clinical and laboratory values for the prediction of positive SF results.

Results

14.7% (n = 41) of blood samples were positive using SF and 17.2% (n = 49) using BC (n.s. [p > 0.05]). In six samples SF detected more than one pathogen. Among the 47 microorganisms identified by SF, only 11 (23.4%) could be confirmed by BC. SF identified a higher number of Gram-negative bacteria than BC did (28 vs. 12, χ² = 7.97, p = 0.005). The combination of BC and SF increased the number of detected microorganisms, including fungi, compared to BC alone (86 vs. 49, χ² = 13.51, p < 0.001). C-reactive protein (CRP) (21.7 ± 11.41 vs. 16.0 ± 16.9 mg/dl, p = 0.009), procalcitonin (28.7 ± 70.9 vs. 11.5 ± 30.4 ng/dl, p = 0.015), and interleukin 6 (IL 6) (932.3 ± 1306.7 vs. 313.3 ± 686.6 pg/ml, p = 0.010) plasma concentrations were higher in patients with a positive SF result. Using ROC analysis, IL-6 (AUC 0.836) and CRP (AUC 0.804) showed the best predictive values for positive SF results.

Conclusion

The SF test represent a valuable method for rapid etiologic diagnosis of BSI in patients after cardiothoracic surgery. In particular this method applies for individuals with suspected Gram-negative blood stream. Due to the low performance in detecting Gram-positive pathogens and the inability to determine antibiotic susceptibility, it should be used in addition to BC only (Pilarczyk K, et al., Intensive Care Med Exp ,3(Suppl. 1):A884, 2015).

Preliminary readings of antimicrobial susceptibility panels: A simple, fast and inexpensive way to detect bacterial resistance and enhance antibiotic treatment of bloodstream infections

Increasing incidence of resistant bacteria needs faster identification (ID) and antibiotic susceptibility testing (AST) in order to improve antimicrobial treatment of severe infections. We propose a preliminary reading of the AST MicroScan® panels coupled with mass spectrometry ID. A total of 157 bacterial clinical isolates were processed for routine ID and AST (in 22 cases, ID and AST were performed directly from positive blood culture bottles). For gram-negatives, data from the initial and final readings were recorded and compared [89.9% category agreement (CA), 6.9% very major errors (VME)]. In adition all the 32 ESBL producers were detected at 5.3-8.6 hours. For Staphylococcus aureus, all the 16 MRSA isolates were detected at 4.5 to 7.5 hours. Thus, we find our preliminary readings approach as a simple, inexpensive and reliable way to detect and identify the most prevalent resistant bacteria in our institution on the same day that ID/AST is performed.

Screening for Carbapenemases in Ertapenem-Resistant Enterobacteriaceae Collected at a Tunisian Hospital Between 2014 and 2018

Background

Carbapenem-resistance is frequently detected in Enterobacteriaceae isolated from patients in Tunisia. The study was performed to identify frequent carbapenemases in Tunisian isolates.

Methods

Between May 2014 and January 2018, 197 ertapenem-resistant Enterobacteriaceae were isolated at the microbiological department of the Military Hospital of Tunis. The strains were phenotypically characterized and then subjected to in-house polymerase chain reaction (PCR) targeting the carbapenemase genes bla_IMP, bla_VIM, bla_NDM, bla_SPM, bla_AIM, bla_DIM,bla_GIM, bla_SIM, bla_KPC, bla_BIC, and bla_OXA-48.

Results

The assessed 197 ertapenem-resistant Enterobacteriaceae from Tunis comprised 170 Klebsiella pneumoniae, 19 Enterobacter cloacae, 6 Escherichia coli, 1 Citrobacter sedlakii, and 1 Enterobacter asburiae. Thereby, 55 out of 197 isolates (27.9%) were from blood cultures, suggesting a systemic disease. The carbapenemase gene bla_OXA-48 quantitatively dominated by far with 153 detections, followed by bla_NDM with 14 detections, which were distributed about the whole study interval. In contrast, bla_BIC and bla_VIM were only infrequently identified in 5 and 3 cases, respectively, while the other carbapenamases were not observed.

Conclusions

The carbapenemase gene bla_OXA-48 was identified in the vast majority of ertapenem-resistant Tunisian Enterobacteriaceae while all other assessed carbapenemases were much less abundant. In a quantitatively relevant minority of isolates, the applied PCR-based screening approach did not identify any carbapenemases.

Current antimicrobial susceptibility testing for beta-lactamase-producing Enterobacteriaceae in clinical settings

The worldwide prevalence of beta-lactamase-producing Enterobacteriaceae (BL-E) is increasing. Bacterial infections involving ESBLs can be more difficult to treat because of antibiotic resistance, as there are fewer effective antibiotics left to be used. Moreover, treatment failure is often observed. Thus, quick and accurate identification of β-lactamases is imperative to minimize it. This review article describes most commonly used phenotypic techniques and molecular methods for the detection of ESBLs, acquired AmpC β-lactamases, and carbapenemases produced by Enterobacteriaceae. Phenotypic detection tests remain useful and relevant in clinical laboratories while molecular diagnostic methods are less affordable, more technically demanding, and not standardized. Molecular methods could be used to speed up results of bacterial antibiotic resistance or to clarify the results of phenotypic β-lactamases confirmation tests.

Prevalence of carbapenemase-producing organisms at the Kidney Center of Rawalpindi (Pakistan) and evaluation of an advanced molecular microarray-based carbapenemase assay

AIM

A DNA microarray-based assay for the detection of antimicrobial resistance (AMR) genes was used to study carbapenemase-producing organisms at the Kidney Center of Rawalpindi, Pakistan.

METHODS

The evaluation of this assay was performed using 97 reference strains with confirmed AMR genes. Testing of 7857 clinical samples identified 425 Gram-negative bacteria out of which 82 appeared carbapenem resistant. These isolates were analyzed using VITEK-2 for phenotyping and the described AMR assay for genotyping.

RESULTS

The most prevalent carbapenemase gene was blaNDM and in 12 isolates we detected two carbapenemase genes (e.g., blaNDM/blaOXA-48).

CONCLUSION

Our prevalence data from Pakistan show that - as in other parts of the world - carbapenemase-producing organisms with different underlying resistance mechanisms are emerging, and this warrants intensified and constant surveillance.

Resistant Gram-Negative Bacteria and Diagnostic Point-of-Care Options for the Field Setting during Military Operations

The spread of multidrug-resistant bacteria in resource-poor settings affects the military medical service in case of deployments of soldiers to war and crisis zones. Patients with war injuries are prone to colonization or infection with multidrug-resistant bacteria. Resistant Gram-negative bacteria play a dominant role in military wound infections. Problematic hygiene conditions on deployment facilitate exposition of soldiers with subsequent colonization. Although colonizing strains are frequently cleared from their hosts after returning from deployment, transmission to close contacts of the soldiers in the home country cannot be excluded and therapeutic options are reduced if colonization progresses to invasive infection. Since sophisticated culture-based diagnostic approaches are typically not available in the field setting on deployment, molecular rapid diagnostic test systems are an option for transmission control if the locally prevalent molecular resistance mechanisms are known. Efforts for global resistance surveillance can contribute to better understanding of resistance distribution and spread at deployment sites. This review summarizes experience of the military medical services with multidrug resistance on deployment and with the influx of resistant strains to the home country and discusses potential use of available molecular rapid test systems as an option for the field setting.

What Healthcare Workers Should Know about Environmental Bacterial Contamination in the Intensive Care Unit

Intensive care unit- (ICU-) acquired infections are a major health problem worldwide. Inanimate surfaces and equipment contamination may play a role in cross-transmission of pathogens and subsequent patient colonization or infection. Bacteria contaminate inanimate surfaces and equipment of the patient zone and healthcare area, generating a reservoir of potential pathogens, including multidrug resistant species. Traditional terminal cleaning methods have limitations. Indeed patients who receive a bed from prior patient carrying bacteria are exposed to an increased risk (odds ratio 2.13, 95% confidence intervals 1.62-2.81) of being colonized and potentially infected by the same bacterial species of the previous patient. Biofilm formation, even on dry surfaces, may play a role in reducing the efficacy of terminal cleaning procedures since it enables bacteria to survive in the environment for a long period and provides increased resistance to commonly used disinfectants. No-touch methods (e.g., UV-light, hydrogen peroxide vapour) are under investigation and further studies with patient-centred outcomes are needed, before considering them the standard of terminal cleaning in ICUs. Healthcare workers should be aware of the role of environmental contamination in the ICU and consider it in the broader perspective of infection control measures and stewardship initiatives.

Comparison of clinical methods for detecting carbapenem-resistant Enterobacteriaceae

We evaluated detection of carbapenem-resistant Enterobacteriaceae (CRE) by routine minimal inhibitory concentration (MIC) testing, polymerase chain reaction (PCR) using Xpert® Carba-R assay, hydrolysis of ertapenem and imipenem detected by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS), and hydrolysis by colorimetry using the EPI-CRE assay. Ninety-six Enterobacteriaceae isolates possessing carbapenemase genes and 29 carbapenem-susceptible Enterobacteriaceae were available for testing. The sensitivity and specificity of each assay was determined. For sensitivity, discrepant results from each assay compared to reference genotype were arbitrated with MIC and/ or PCR testing to assess loss of plasmid-mediated resistance. Xpert Carba-R was evaluated for resistance genes in their FDA claim (i.e., the genes encoding KPC; NDM; VIM; IMP; and OXA-48). The sensitivity for the assays was: MIC (N=96), 96.8%, (discrepant analysis to 98.9% [2 cured plasmids]); Xpert Carba-R (N=85), 97.6% (discrepant analysis to 100% % [2 cured plasmids]); EPI-CRE (N=96), 91.7% (discrepant analysis to 91.7%); MALDI-TOF MS (N=96) ertapenem hydrolysis using Compass software for interpretation (2 h incubation), 92.7% (discrepant analysis to 94.7% % [2 cured plasmids]); MALDI-TOF MS (N=96) imipenem hydrolysis (1 h incubation), 97.9% (discrepant analysis to 98.9% % [1 cured plasmid]). The specificity for each assay was: MIC (N=29), 100%; EPI-CRE (N=29), 96.6%; MALDI-TOF MS ertapenem hydrolysis (N=29), 100%; MALDI-TOF MS imipenem hydrolysis (N=29), 96.6%. All isolates tested to ensure specificity demonstrated susceptible MIC results for carbapenems and did not qualify for testing with Xpert Carba-R. No single assay detected all of the known genetic markers of carbapenem hydrolysis.

Evaluation of Genotypic and Phenotypic Methods to Detect Carbapenemase Production in Gram-Negative Bacilli

BACKGROUND

Carbapenemase-producing gram-negative bacteria (CP-GNB) are an urgent and expanding public health threat. Rapid and accurate identification of these organisms facilitates infection prevention efforts in healthcare facilities. The objective of our study was to evaluate methods to detect and identify CP-GNB.

METHODS

We examined 189 carbapenem-resistant GNB(CR-GNB), including Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii complex, using 3 different methods: 2 methods to screen isolates of GNB for carbapenemase production [the carbapenem inactivation method (CIM) and 2 chromogenic agars] and a molecular method (Cepheid GeneXpert Carba-R) to identify the mechanism of carbapenem resistance and the associated resistance genes (bla_KPC, bla_NDM, bla_IMP, bla_OXA-48-like, and bla_VIM).

RESULTS

The CIM was a simple and inexpensive phenotypic screen to differentiate between CR-GNB and CP-GNB, with improved analytical performance characteristics and inter-reader correlation compared to the modified Hodge test. Both chromogenic agars evaluated (HardyCHROM CRE and chromID CARBA) were able to support growth of most of the organisms tested, including isolates possessing the bla_OXA-48-like gene. However, these media had a low analytical specificity for carbapenemase production, with breakthrough of CR-GNB that did not produce a carbapenemase. The Xpert Carba-R assay was rapid and easy to perform, and demonstrated 100% positive and negative agreement for characterization of genetic determinants of carbapenem resistance.

CONCLUSIONS

Screening by CIM followed by the Xpert Carba-R PCR is an accurate method for detecting and characterizing CP-GNB, including Enterobacteriaceae, P. aeruginosa, and A. baumannii complex.