Susceptibility rates of clinically important bacteria collected from intensive care units against colistin, carbapenems, and other comparative agents: results from Surveillance of Multicenter Antimicrobial Resistance in Taiwan (SMART)

Clinical outcomes of carbapenem-resistant gram-negative bacterial bloodstream infection in patients with end-stage renal disease in intensive care units: a multicenter retrospective observational study

BACKGROUND

Carbapenem-resistant gram-negative bacteria (CRGNB) present a considerable global threat due to their challenging treatment and increased mortality rates, with bloodstream infection (BSI) having the highest mortality rate. Patients with end-stage renal disease (ESRD) undergoing renal replacement therapy (RRT) face an increased risk of BSI. Limited data are available regarding the prognosis and treatment outcomes of CRGNB-BSI in patients with ESRD in intensive care units (ICUs).

METHODS

This multi-center retrospective observational study included a total of 149 ICU patients with ESRD and CRGNB-BSI in Taiwan from January 2015 to December 2019. Clinical and microbiological outcomes were assessed, and multivariable regression analysis was used to evaluate the independent risk factors for day-28 mortality and the impact of antimicrobial therapy regimen on treatment outcomes.

RESULTS

Among the 149 patients, a total of 127 patients (85.2%) acquired BSI in the ICU, with catheter-related infections (47.7%) and pneumonia (32.2%) being the most common etiologies. Acinetobacter baumannii (49.0%) and Klebsiella pneumoniae (31.5%) were the most frequently isolated pathogens. The day-28 mortality rate from BSI onset was 52.3%, and in-hospital mortality was 73.2%, with survivors experiencing prolonged hospital stays. A higher Sequential Organ Failure Assessment (SOFA) score (adjusted hazards ratio [aHR], 1.25; 95% confidence interval [CI] 1.17-1.35) and shock status (aHR, 2.12; 95% CI 1.14-3.94) independently predicted day-28 mortality. Colistin-based therapy reduced day-28 mortality in patients with shock, a SOFA score of ≥ 13, and Acinetobacter baumannii-related BSI.

CONCLUSIONS

CRGNB-BSI led to high mortality in critically ill patients with ESRD. Day-28 mortality was independently predicted by a higher SOFA score and shock status. In patients with higher disease severity and Acinetobacter baumannii-related BSI, colistin-based therapy improved treatment outcomes.

Application of a multiplex molecular pneumonia panel and real-world impact on antimicrobial stewardship among patients with hospital-acquired and ventilator-associated pneumonia in intensive care units

BACKGROUND

The optimal timing for applying the BioFire FilmArray Pneumonia Panel (FAPP) in intensive care unit (ICU) patients with hospital-acquired pneumonia (HAP) or ventilator-associated pneumonia (VAP) remains undefined, and there are limited data on its impact on antimicrobial stewardship.

METHODS

This retrospective study was conducted at a referral hospital in Taiwan from November 2019 to October 2022. Adult ICU patients with HAP/VAP who underwent FAPP testing were enrolled. Patient data, FAPP results, conventional microbiological testing results, and the real-world impact of FAPP results on antimicrobial therapy adjustments were assessed. Logistic regression was used to determine the predictive factors for bacterial detection by FAPP.

RESULTS

Among 592 respiratory specimens, including 564 (95.3%) endotracheal aspirate specimens, 19 (3.2%) expectorated sputum specimens and 9 (1.5%) bronchoalveolar lavage specimens, from 467 patients with HAP/VAP, FAPP testing yielded 368 (62.2%) positive results. Independent predictors for positive bacterial detection by FAPP included prolonged hospital stay (odds ratio [OR], 3.14), recent admissions (OR, 1.59), elevated C-reactive protein levels (OR, 1.85), Acute Physiology and Chronic Health Evaluation II scores (OR, 1.58), and septic shock (OR, 1.79). Approximately 50% of antimicrobial therapy for infections caused by Gram-negative bacteria and 58.4% for Gram-positive bacteria were adjusted or confirmed after obtaining FAPP results.

CONCLUSIONS

This study identified several factors predicting bacterial detection by FAPP in critically ill patients with HAP/VAP. More than 50% real-world clinical practices were adjusted or confirmed based on the FAPP results. Clinical algorithms for the use of FAPP and antimicrobial stewardship guidelines may further enhance its benefits.

Therapeutic Potential of a Novel Lytic Phage, vB_EclM_ECLFM1, against Carbapenem-Resistant Enterobacter cloacae

The global rise of multidrug-resistant Enterobacter cloacae strains, especially those that are resistant to carbapenems and produce metallo-β-lactamases, poses a critical challenge in clinical settings owing to limited treatment options. While bacteriophages show promise in treating these infections, their use is hindered by scarce resources and insufficient genomic data. In this study, we isolated ECLFM1, a novel E. cloacae phage, from sewage water using a carbapenem-resistant clinical strain as the host. ECLFM1 exhibited rapid adsorption and a 15-min latent period, with a burst size of approximately 75 PFU/infected cell. Its genome, spanning 172,036 bp, was characterized and identified as a member of Karamvirus. In therapeutic applications, owing to a high multiplicity of infection, ECLFM1 showed increased survival in zebrafish infected with E. cloacae. This study highlights ECLFM1's potential as a candidate for controlling clinical E. cloacae infections, which would help address challenges in treating multidrug-resistant strains and contribute to the development of alternative treatments.

Recommendations and guidelines for the treatment of infections due to multidrug resistant organisms

Antimicrobial drug resistance is one of the major threats to global health. It has made common infections increasingly difficult or impossible to treat, and leads to higher medical costs, prolonged hospital stays and increased mortality. Infection rates due to multidrug-resistant organisms (MDRO) are increasing globally. Active agents against MDRO are limited despite an increased in the availability of novel antibiotics in recent years. This guideline aims to assist clinicians in the management of infections due to MDRO. The 2019 Guidelines Recommendations for Evidence-based Antimicrobial agents use in Taiwan (GREAT) working group, comprising of infectious disease specialists from 14 medical centers in Taiwan, reviewed current evidences and drafted recommendations for the treatment of infections due to MDRO. A nationwide expert panel reviewed the recommendations during a consensus meeting in Aug 2020, and the guideline was endorsed by the Infectious Diseases Society of Taiwan (IDST). This guideline includes recommendations for selecting antimicrobial therapy for infections caused by carbapenem-resistant Acinetobacter baumannii, carbapenem-resistant Pseudomonas aeruginosa, carbapenem-resistant Enterobacterales, and vancomycin-resistant Enterococcus. The guideline takes into consideration the local epidemiology, and includes antimicrobial agents that may not yet be available in Taiwan. It is intended to serve as a clinical guide and not to supersede the clinical judgment of physicians in the management of individual patients.

Impact of pretransplant bloodstream infection on clinical outcomes after heart transplantation

BACKGROUND

Active bloodstream infection (BSI) is a contraindication for heart transplantation (HT). However, some critical patients with BSI may undergo HT as a life-saving procedure. We aimed to investigate the impact of pretransplant BSI on the clinical outcomes after HT.

METHODS

We enrolled 511 consecutive patients who underwent HT between 1999 and 2019. Patients were divided into two groups based on the presence of BSI within 30 days preoperatively. Forty-three patients (8.4%) with BSI who were clinically stable and had no metastatic infection were considered for HT on an individual basis. In-hospital mortality, incidence of early postoperative BSI, length of postoperative hospital stays, and long-term survival were compared between the groups. Logistic and Cox regression analyses were performed to identify risk factors for in-hospital and 1-year mortality.

RESULTS

Patients with pretransplant BSI had a high incidence of previous cardiopulmonary resuscitation, pretransplant ventilator use, mechanical circulatory support use, renal replacement therapy, United Network for Organ Sharing status 1A, and a prolonged preoperative hospital waiting period. The in-hospital mortality rate was higher in patients with pretransplant BSI (21% versus 12%, p = 0.081), and the mortality rate was very high (33.3%) for those with BSI 0-15 days before HT. In addition, patients with pretransplant BSI had a significantly longer postoperative hospital stay than patients in the control group. However, long-term survival was similar in both groups.

CONCLUSIONS

Although pretransplant BSI was associated with higher in-hospital mortality and prolonged postoperative hospital stay, patients who survived the early period had a similar long-term prognosis. This article is protected by copyright. All rights reserved.

Postvitrectomy endophthalmitis caused by Morganella morganii: a case report and literature review

Background

Postvitrectomy endophthalmitis is a rare and serious complication following vitreoretinal surgeries. Morganella morganii, an emerging gram-negative, facultative anaerobic rod, is related to severe nosocomial infections in various organs and thus has gained importance in recent decades. Morganella morganii infection following intraocular surgery is rarely reported.

Case presentation

We report an immunocompetent patient with Morganella morganii-related endophthalmitis after vitrectomy for retinal detachment who presented with hand motion visual acuity, hypopyon and a unique retrolental exudative membrane. Initially, the patient was unresponsive to empirical intravitreal ceftazidime and vancomycin but recovered with vision preservation (20/63) after surgical removal of the membrane and silicone oil tamponade.

Conclusions

Morganella morganii intraocular infection is often devastating, likely due to its high multidrug-resistance rate via intrinsic ß-lactamase production, multiple acquired traits related to additional genetic mechanisms, and fimbrial adhesion, urease production, and type III secretion system-associated biofilm formation. The above characteristics of M. morganii may lead to an inadequate response to empirical intravitreal antibiotics, and early surgical intervention should be considered.

Molecular Epidemiology, Risk Factors and Clinical Outcomes of Carbapenem-Nonsusceptible Enterobacter cloacae Complex Infections in a Taiwan University Hospital

The genus Enterobacter is a member of the ESKAPE group, which contains the major resistant bacterial pathogens. Enterobacter cloacae complex (ECC) has emerged as a clinically significant cause of a wide variety of nosocomial infections. Carbapenem-nonsusceptible Enterobacter cloacae complex (CnsECC) has become an emerging threat to public health but there is still a lack of comprehensive molecular and clinical epidemiological analysis. A total of 157 CnsECC isolates were recovered during October 2011 to August 2017. hsp60 gene sequencing and pulsed-field gel electrophoresis (PFGE) were applied to discriminate the species, genetic clusters and clonal relatedness. All the isolates were subjected to polymerase chain reaction (PCR) analysis for carbapenemase, AmpC-type β-lactamase, and extended spectrum β-lactamase (ESBL) genes. Clinical data were collected on all patients for comparing clinical risks and outcomes between patients with carbapenemase-producing (CP)-CnsECC compared with non-CP-CnsECC infection. The most commonly identified species was E. hormaechei subsp. hoffmannii (47.1%), followed by E. hormaechei subsp. steigerwaltii (24.8%). Different species of CnsECC isolates showed heterogeneity in resistance patterns to piperacillin/tazobactam, cefepime and levofloxacin. In the present study, we observed that E. hormaechei subsp. hoffmannii was characterized with higher cefepime and levofloxacin resistance rate but lower piperacillin/tazobactam resistance rate relative to other species of CnsECC. CP-CnsECC comprised 41.1% (65 isolates) and all of these isolates carried IMP-8. In this study, 98% of patients had antimicrobial therapy prior to culture, with a total of 57/150 (38%) patients being exposed to carbapenems. Chronic pulmonary disease (OR: 2.51, 95% CI: 1.25–5.06), received ventilator support (OR: 5.54, 95% CI: 2.25–12.03), steroid exposure (OR: 3.88, 95% CI: 1.91–7.88) and carbapenems exposure (OR: 2.17, 95% CI: 1.10–4.25) were considered risk factors associated with CP-CnsECC infection. The results suggest that CP-CnsECC are associated with poorer outcomes including in-hospital mortality, 30-day mortality and 100-day mortality. Our study provides insights into the epidemic potential of IMP-8-producing E. cloacae for healthcare-associated infections and underscores the importance of understanding underlying resistance mechanisms of CnsECC to direct antibiotic treatment decisions.

Multicenter surveillance of antimicrobial susceptibilities and resistance mechanisms among Enterobacterales species and non-fermenting Gram-negative bacteria from different infection sources in Taiwan from 2016 to 2018

OBJECTIVES

To explore the in vitro antimicrobial susceptibility among clinically important Gram-negative bacteria (GNB) in Taiwan.

METHODS

From 2016 through 2018, a total of 5458 GNB isolates, including Escherichia coli (n = 1545), Klebsiella pneumoniae (n = 1255), Enterobacter species (n = 259), Pseudomonas aeruginosa (n = 1127), Acinetobacter baumannii complex (n = 368), and Stenotrophomonas maltophilia (n = 179), were collected. The susceptibility results were summarized by the breakpoints of minimum inhibitory concentration (MIC) of CLSI 2020, EUCAST 2020 (for colistin), or published articles (for ceftolozane/tazobactam). The resistance genes among multidrug-resistant (MDR) or extensively drug-resistant (XDR)-GNB were investigated by multiplex PCR.

RESULTS

Significantly higher rates of non-susceptibility (NS) to ertapenem and carbapenemase production, predominantly KPC and OXA-48-like beta-lactamase, were observed in Enterobacterales isolates causing respiratory tract infection than those causing complicated urinary tract or intra-abdominal infection (12.7%/3.44% vs. 5.7%/0.76% or 7.7%/0.97%, respectively). Isolates of Enterobacter species showed higher rates of phenotypic extended-spectrum β-lactamase and NS to ertapenem than E. coli or K. pneumoniae isolates. Although moderate activity (54-83%) was observed against most potential AmpC-producing Enterobacterales isolates, ceftolozane/tazobactam exhibited poor in vitro (44.7-47.4%) activity against phenotypic AmpC Enterobacter cloacae isolates. Additionally, 251 (22.3%) P. aeruginosa isolates exhibited the carbapenem-NS phenotype, and their MDR and XDR rate was 63.3% and 33.5%, respectively. Fifteen (75%) of twenty Burkholderia cenocepacia complex isolates were inhibited by ceftolozane/tazobactam at MICs of ≤4 μg/mL.

CONCLUSIONS

With the increase in antibiotic resistance in Taiwan, it is imperative to periodically monitor the susceptibility profiles of clinically important GNB.

Treatment of patients with serious infections due to carbapenem-resistant Acinetobacter baumannii: How viable are the current options?

This review critically appraises the published microbiologic and clinical data on the treatment of patients with carbapenem-resistant Acinetobacter baumannii infections. Despite being recognized as an urgent threat pathogen by the CDC and WHO, optimal treatment of patients with serious CRAB infections remains ill-defined. Few commercially available agents exhibit reliable in vitro activity against CRAB. Historically, polymyxins have been the most active agents in vitro, though interpretations of susceptibility data are difficult given issues surrounding MIC testing methodologies and lack of correlation between MICs and clinical outcomes. Most available preclinical and clinical data involve use of polymyxins, tetracyclines, and sulbactam, alone and in combination. As the number of viable treatment options is limited, combination therapy with a polymyxin is often used for patients with CRAB infections, despite the significant risk of nephrotoxicity. However, no treatment regimen has been found to reduce mortality, which exceeds 40% across most studies, or substantially improve clinical response. While some newer agents, such as eravacycline and cefiderocol, have demonstrated in vitro activity, clinical efficacy has not been fully established. New agents with clinically relevant activity against CRAB isolates and favorable toxicity profiles are sorely needed.

Antimicrobial Resistance Mechanisms and Virulence of Colistin- and Carbapenem-Resistant Acinetobacter baumannii Isolated from a Teaching Hospital in Taiwan

Acinetobacter baumannii, a Gram-negative bacterium, is an important nosocomial pathogen. Colistin-resistant A. baumannii is becoming a new concern, since colistin is one of the last-line antibiotics for infections by carbapenem-resistant A. baumannii. From 452 carbapenem-resistant isolates collected in a teaching hospital in Taipei, Taiwan, we identified seven that were resistant to colistin. Carbapenem resistance in these isolates is attributed to the presence of carbapenemase gene bla_OXA-23 in their genomes. Colistin resistance is presumably conferred by mutations in the sensor kinase domain of PmrB found in these isolates, which are known to result in modification of colistin target lipid A via the PmrB-PmrA-PmrC signal transduction pathway. Overexpression of pmrC, eptA, and naxD was observed in all seven isolates. Colistin resistance mediated by pmrB mutations has never been reported in Taiwan. One of the seven isolates contained three mutations in lpxD and exhibited an altered lipopolysaccharide profile, which may contribute to its colistin resistance. No significant difference in growth rates was observed between the isolates and the reference strain, suggesting no fitness cost of colistin resistance. Biofilm formation abilities of the isolates were lower than that of the reference. Interestingly, one of the isolates was heteroresistant to colistin. Four of the isolates were significantly more virulent to wax moth larvae than the reference.

Emergence of concurrent levofloxacin- and trimethoprim/sulfamethoxazole-resistant Stenotrophomonas maltophilia: Risk factors and antimicrobial sensitivity pattern analysis from a single medical center in Taiwan

BACKGROUND

The emergence of concurrent levofloxacin- and trimethoprim/sulfamethoxazole (TMP/SMX)-resistant Stenotrophomonas maltophilia (LTSRSM) in Taiwan is becoming a serious problem, but clinical data analysis on this has not been reported.

METHODS

A matched case-control-control study was conducted to investigate risk factors for LTSRSM occurrence in hospitalized patients. For patients with LTSRSM infection/colonization (the case group), two matched control groups were used: control group A with levofloxacin- and TMP/SMX-susceptible S. maltophilia (LTSSSM) and control group B without S. maltophilia. Besides, tigecycline, ceftazidime, cefepime, ciprofloxacin, gentamicin, amikacin, and colistin susceptibilities in collected LTSRSM and levofloxacin- and TMP/SMX-susceptible S. maltophilia (LTSSSM) isolates were compared.

RESULTS

From January 2014 to June 2016, 129 LTSRSM from cultured 1213 S. maltophilia isolates (10.6%) were identified. A total of 107 LTSRSM infected patients paired with 107 LTSSSM-, and 107 non-S. maltophilia-infected ones were included. When compared with control group A, previous fluoroquinolone and TMP/SMX use was found to be independently associated with LTSRSM occurrence. When compared with control group B, mechanical ventilation, cerebrovascular disease, and previous fluoroquinolone use were risk factors for LTSRSM occurrence. Eighty-five LTSRSM and 85 LTSSSM isolates were compared for antibiotic susceptibilities; the resistance rates and minimum inhibitory concentrations of tigecycline and ceftazidime were significantly higher for LTSRSM than for LTSSSM isolates.

CONCLUSION

The emergence of LTSRSM showing cross resistance to tigecycline and ceftazidime would further limit current therapeutic options. Cautious fluoroquinolone and TMP/SMX use may be helpful to limit such high-level resistant strains of S. maltophilia occurrence.

Molecular Characterization of Carbapenem/Colistin-Resistant Acinetobacter baumannii Clinical Isolates from Egypt by Whole-Genome Sequencing

PURPOSE

The rise of carbapenem-resistant A. baumannii (CRAB) is considered a public health problem limiting the treatment options. Our current work studied the emergence and mechanisms of colistin-resistance among CRAB isolates in Egypt.

MATERIALS AND METHODS

Seventeen clinically recovered A. baumannii were identified and screened for their antimicrobial susceptibilities using VITEK-2 system. Colistin susceptibility was evaluated using broth microdilution, and characterization of carbapenem/colistin resistance determinants was performed using whole-genome sequencing (Illumina MiSeq).

RESULTS

About 52.9% (9/17) were colistin-resistant. PCR results revealed that all isolates carried bla OXA-51-like genes, bla OXA-23-like was detected in 82.3% (14/17) and bla NDM in 23.5% (4/17). Two isolates harboured bla GES-35 and bla OXA-23. Furthermore, genome analysis of seven isolates revealed six belonged to international clone 2 (IC2) while the remaining isolate was a singleton (ST158), representing a clone circulating in Mediterranean/Middle Eastern countries.

CONCLUSION

The emergence and high incidence of colistin-resistance among CRAB clinical isolates in Egypt are alarming because it further limits therapy options and requires prudent antimicrobial stewardship and stringent infection control measures. Whole-genome sequence analyses suggest that the resistance to colistin was associated with multiple mutations in the pmrCAB genes. The high incidence of the high-risk lineage IC2 harbouring bla OXA-23-like as well as bla NDM is also of concern.

Evaluation of Vitek®2 performance for colistin susceptibility testing for Gram-negative isolates

Background

The emerging resistance to the last-resort antimicrobial colistin is being reported globally. Underestimation of the burden of colistin resistance and misinterpretation of colistin susceptibility test results, using suboptimal testing methods, may be causing unexplained treatment failures and even mortality among critically ill patients. Thus, this study was conducted at an apex trauma centre to assess the performance of Vitek®2 for colistin susceptibility testing.

Methods

A total of 910 clinical isolates of Gram-negative bacteria (GNB), including Enterobacterales, Acinetobacter baumannii and Pseudomonas aeruginosa, were tested and analysed for colistin resistance using Vitek®2. Broth microdilution (BMD) was taken as the reference method. The essential (EA) and categorical (CA) agreements and very major error (VME) and major error (ME) rates were calculated. An MIC correlation was taken to be positive with EA ≥ 90%, CA ≥ 90%, VME ≤ 1.5% and ME ≤ 3.0% rates. Spearman's coefficient was calculated and P < 0.05 was considered statistically significant.

Results

A total of 64% of isolates were MDR. Overall, 196 (21.5%) and 110 (12%) of isolates were resistant to colistin by BMD and Vitek®2, respectively. The automated Vitek®2 method failed to detect the resistance in up to 48.5% of GNB tested. When comparing Vitek®2 colistin interpretive results with reference BMD for all 910 isolates, the CA was 88% (798/910) with 10% (95/910) VMEs and 1% (9/910) MEs.

Conclusions

The Vitek®2 method for colistin susceptibility testing, still in use in some settings; is a suboptimal and unreliable method.

National Surveillance of Antimicrobial Susceptibility of Bacteremic Gram-Negative Bacteria with Emphasis on Community-Acquired Resistant Isolates: Report from the 2019 Surveillance of Multicenter Antimicrobial Resistance in Taiwan (SMART)

A multicenter collection of bacteremic isolates of Escherichia coli (n = 423), Klebsiella pneumoniae (n = 372), Pseudomonas aeruginosa (n = 300), and Acinetobacter baumannii complex (n = 199) was analyzed for susceptibility. Xpert Carba-R assay and sequencing for mcr genes were performed for carbapenem- or colistin-resistant isolates. Nineteen (67.8%) carbapenem-resistant K. pneumoniae (n = 28) and one (20%) carbapenem-resistant E. coli (n = 5) isolate harbored bla _KPC (n = 17), bla _OXA-48 (n = 2), and bla _VIM (n = 1) genes.

Molecular Evidence for Intra- and Inter-Farm Spread of Porcine mcr-1-Carrying Escherichia coli in Taiwan

From January 2013 to December 2018, 90 Escherichia coli isolates were collected from 90 sick pigs on 58 farms in seven cities in Taiwan. The minimum inhibitory concentrations (MICs) of the isolates to 14 antimicrobial agents were determined on the VITEK 2 system (bioMérieux, Marcy-l’Etoile, France), and the resistance to colistin was assessed via the reference broth microdilution (BMD) method. The mobilized colistin resistance genes (mcr) were determined for the colistin-resistant isolates, which displayed BMD MICs ≥ 4 mg/L. Genotypes of the mcr-positive E. coli isolates were determined by multilocus sequence typing, arbitrarily primed polymerase chain reaction (PCR), and pulsed-field gel electrophoresis. All of the isolates were tested for susceptibility to carbapenems. Fifty isolates (55.6%) were resistant to colistin, 39 of which (78%) were positive for the mcr-1 gene. E. coli isolates harboring mcr-1 were most frequent in 2017 (15/18, 83.3%), followed by 2018 (13/23, 56.5%), 2015 (7/21, 33.3%), and 2016 (3/24, 12.5%). A total of 18 sequence types (STs) were identified among the 39 porcine mcr-1-carrying E. coli isolates; 13 were ST2521 (33.3%) isolated in 2017 and 2018. Five genotypes (clones) were identified, and the same genotypes were in sick pigs on the same farm and different farms. This suggests intra- and inter-farm spread of porcine mcr-1-carrying E. coli. The results presented here indicate high colistin resistance and wide mcr-1 E. coli prevalence among the sick pigs sampled in 2015–2018 in different regions of Taiwan.

Resistance and heteroresistance to colistin among clinical isolates of Acinetobacter baumannii

Colistin is one of the most effective alternatives for treating Acinetobacter baumannii infections. The aim of this study was to determine colistin resistance and heteroresistance rates in A. baumannii from clinical samples in Hacettepe University clinical microbiology laboratory between June 2016 and January 2017. A total of 200 isolates were included in the study. In vitro susceptibility to amikacin, gentamicin, ceftazidime, piperacillin/tazobactam, meropenem, ciprofloxacin, and tigecycline were determined by disk diffusion test. Most isolates were multiresistant as they exhibited resistance to aminoglycosides, β-lactams, and fluoroquinolones. Colistin susceptibility was determined by broth microdilution (BMD) test (EUCAST standards) and was compared with E-test (bioMérieux, France) in 120 isolates. In 14 blood isolates that were susceptible to colistin (MIC ≤ 2 mg/L), heteroresistance was investigated with the population analysis profile (PAP) method. Overall resistance (n = 200) to colistin was 28% by BMD. Among the 120 isolates where the two tests were compared, resistance to colistin was 25.8% versus 4.2% with BMD and E-test, respectively. Three blood isolates (21.4%) were heteroresistant to colistin. With E-test, a majority of the resistant isolates are overlooked and in vitro susceptibility to colistin should be determined with broth dilution method. This is the first study in Turkey reporting heteroresistance in A. baumannii isolates by the PAP method and emphasizes the need to test for heteroresistance in relation to clinical outcome in serious infections due to A. baumannii.

Ringing bells: Morganella morganii fights for recognition

OBJECTIVES

The global increase in rare opportunistic microbial infections is alarming. The current review was undertaken to study the diversified disease spectrum, pathogenicity, and resistance patterns of Morganella morganii.

STUDY DESIGN

This study is a review of the diversified disease spectrum of M. morganii.

METHODS

The articles used in this review were all extracted from PubMed and Google Scholar, using the terms 'M. morganii', 'prevalence', 'virulence factors', 'infections', 'resistance pattern', and 'genomics'. This review includes original articles, reviews, and case reports focusing on M. morganii, hospital-based prevalence studies, and studies on resistance in M. morganii published between 1906 and April 2019. Articles published in English, French, Spanish, and Chinese were reviewed.

RESULTS

M. morganii has had a significant impact as a clinical pathogen and the pace of its occurrence and the increase in its resistance rates puts this bacterium on the path to becoming the next 'superbug'. These developments not only impact M. morganii, but as a result of gene and plasmid transfer evolution, other clinical pathogens have been able to acquire their diverse intrinsic and acquired virulence genes. Its vast host range raises concerns around its capacity to generate new infections through novel symbiotic relationships.

CONCLUSIONS

M. morganii opportunism is being increasingly reported across the globe. This bacterium is accumulating intrinsic and acquired multidrug resistance genes, resulting in increased morbidity and mortality rates for M. morganii infections and complicating its treatment. M. morganii should be recognized as a clinically significant pathogen, and clinicians should place this microorganism in the list of causative possibilities during patient care. It is important for both the infection control activities in hospitals and in public health sector.

Novel Tetracyclines Versus Alternative Antibiotics for Treating Acute Bacterial Infection: A Meta-Analysis of Randomized Controlled Trials

This meta-analysis assessed the efficacy and safety of novel tetracyclines for treating acute bacterial infections. Data from PubMed, Web of Science, EBSCO, Cochrane databases, Ovid Medline, and Embase databases were accessed until 11 July 2019. Only randomized controlled trials (RCTs) comparing the efficacy of novel tetracyclines with that of other antibiotics for treating acute bacterial infections were included. Primary outcomes included the clinical response, microbiological response, and risk of adverse events (AEs). A total of eight RCTs were included, involving 2283 and 2197 patients who received novel tetracyclines and comparators, respectively. Overall, no significant difference was observed in the clinical response rate at test of cure between the experimental and control groups (for modified intent-to-treat [MITT] population, risk ratio [RR]: 1.02, 95% confidence interval [CI]: 0.99–1.05; for clinically evaluable [CE] population, RR: 1.02, 95% CI: 1.00–1.04; and for microbiological evaluable [ME] population, RR: 1.01, 95% CI: 0.99–1.04). No significant difference in the microbiological response at the end of treatment was observed between the experimental and control groups (for ME population, RR: 1.01, 95% CI: 0.99–1.03; for microbiological MITT population, RR: 1.01, 95% CI: 0.96–1.07). No difference was observed concerning the risk of treatment-emergent adverse events (TEAEs), serious adverse events, and discontinuation of treatment due to TEAEs and all-cause mortality between the two groups. In conclusion, clinical efficacy and safety profile for novel tetracyclines in the treatment of acute bacterial infections were found to be similar to those for other available antibiotics.

Meropenem-Vaborbactam in the Treatment of Acute Bacterial Infections

This study reports the integrated analysis of two phase III studies of meropenem-vaborbactam in the treatment of acute bacterial infections. Targeting Antibiotic Non-Susceptible Gram-Negative Organisms (TANGO) I compared the clinical efficacy and tolerability of meropenem-vaborbactam and piperacillin-tazobactam in the treatment of complicated urinary tract infection (cUTI)/acute pyelonephritis (APN). TANGO II compared the effect and safety of meropenem-vaborbactam and best-available therapy in the treatment confirmed/suspect carbapenem-resistant Enterobacteriaceae infections. The clinical cure rates at end of treatment (EOT) and test of cure (TOC) among the meropenem-vaborbactam group were non-inferior to those of the control group (at EOT, 92.5% versus 89.3%, risk ratio (RR) 1.27, 95% CI 0.64–2.50; at TOC, 86.2% versus 81.7%, RR 1.37, 95% CI 0.62–3.01). Meropenem-vaborbactam was non-inferior to comparators for microbiological eradication at EOT and TOC (at EOT, 93.3% versus 88.3%, RR 1.21, 95% CI 0.74–1.97; at TOC, 66.5% versus 59.9%, RR 1.12, 95% CI 0.97–1.30). In the subgroup of patients with cUTI/APN, meropenem-vaborbactam had similar overall success rate to the control group at EOT (RR 1.05, 95% CI 1.01–1.09) and at TOC (RR 1.05, 95% CI 0.93–1.19). Meropenem-vaborbactam had a similar risk of treatment-emergent adverse events, events leading to discontinuation of the study drug, any serious adverse events, life-threatening adverse events, drug-related adverse events, and risk of death to comparators. In conclusion, meropenem-vaborbactam was noninferior to comparators for clinical cure and microbiological eradication in the treatment of acute bacterial infection, particularly cUTI/APN, and meropenem-vaborbactam was as tolerable as comparators.

Performance of three commercial assays for colistin susceptibility in clinical isolates and Mcr-1 carrying reference strain

Objective

Commercially available antibiotic susceptibility tests (cAST) for colistin are reported to shows variable performance. The current controversy on the colistin susceptibility testing and scarce data from India has left the clinical laboratories in a dilemma on the appropriate and practical approach to tackle the colistin antimicrobial susceptibility testing (AST) issue. This study was aimed to evaluate the performance of commonly used cAST for colistin against broth microdilution (BMD) as the reference method in the clinical isolates.

Materials and Methods

Colistin AST was performed on 225 nonduplicate isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii by BMD as the reference method and compared with Vitek-2, Micronaut-S and E-test. The accuracy of the various cASTs was analysed by assessing categorical and essential agreement (EA).

Results

We observed an overall categorical agreement of 98.2%, 99.6% and 96.4% and EA of 92%, 92.4% and 72% for Vitek-2, Micronaut-S and E-test, respectively. Unacceptable rates of major error (10.5%) and very major error (21%) were observed for P. aeruginosa with Vitek-2 and E-test, respectively. All the categorical errors (CEs) (7.7%) with Vitek-2 were seen for minimum inhibitory concentrations ranging within two-fold dilution breakpoint of 2 mg/L.

Conclusion

Micronaut-S was found to be an acceptable method for colistin AST. In contrast, E-test was unreliable in terms of EA. Vitek-2 was found to be reliable for colistin AST, although it was more prone to CE near the colistin breakpoints.