Treatment and clinical outcomes of urinary tract infections caused by KPC-producing Enterobacteriaceae in a retrospective cohort

Neonatal Bloodstream Infection with Ceftazidime-Avibactam-Resistant blaKPC-2-Producing Klebsiella pneumoniae Carrying blaVEB-25

BACKGROUND

Although ceftazidime/avibactam (CAZ/AVI) has become an important option for treating adults and children, no data or recommendations exist for neonates. We report a neonatal sepsis case due to CAZ/AVI-resistant blaKPC-2-harboring Klebsiella pneumoniae carrying blaVEB-25 and the use of a customized active surveillance program in conjunction with enhanced infection control measures.

METHODS

The index case was an extremely premature neonate hospitalized for 110 days that had been previously treated with multiple antibiotics. Customized molecular surveillance was implemented at hospital level and enhanced infection control measures were taken for early recognition and prevention of outbreak. Detection and identification of blaVEB-25 was performed using next-generation sequencing.

RESULTS

This was the first case of a bloodstream infection caused by KPC-producing K. pneumoniae that was resistant to CAZ/AVI without the presence of a metalo-β-lactamase in the multiplex PCR platform in a neonate. All 36 additional patients tested (12 in the same NICU and 24 from other hospital departments) carried wild-type blaVEB-1 but they did not harbor blaVEB-25.

CONCLUSION

The emergence of blaVEB-25 is signal for the horizontal transfer of plasmids at hospital facilities and it is of greatest concern for maintaining a sharp vigilance for the surveillance of novel resistance mechanisms. Molecular diagnostics can guide appropriate antimicrobial therapy and the early implementation of infection control measures against antimicrobial resistance.

Doxycycline for Multidrug-Resistant Gram-Negative Bacterial Infection Treatment: A Scoping Review

Introduction

Multidrug-resistant bacterial infections limit available therapeutic options. Doxycycline is an old antibiotic from the tetracycline class that exhibits a wide antibacterial action, including Gram-negative bacteria (GNB), and could be an alternative for the treatment of multidrug-resistant (MDR) Enterobacteriaceae. The study aimed to systematically identify, evaluate, and summarize the results of studies related to outcomes of treatments for MDR-GNB infections in patients treated with doxycycline.

Methods

This review was conducted in four databases during weeks 41-52 of 2022: PubMed, Medline, Scopus, and Web of Science, from the earliest year available on each database to December 2022. Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines were followed in conducting this study, and PICO was used for the research question of this review.

Results

This scoping review found 8 retrospective studies that included 59 patients. Of these, 69% were treated for ventilator-associated pneumonia (VAP), 27% for urinary tract infections, 2% for bloodstream infections, and 2% for wound infections, both of which were associated with VAP. The usual dosage of doxycycline was 100 mg intravenously or orally. Clinical and microbiologic improvements were achieved in 81.3% and 87% of all patients, respectively. The mortality rate was 17.3% and was exclusively due to VAP.

Conclusions

Doxycycline showed promising results in this review; however, randomized clinical trials or prospective cohorts are recommended to demonstrate the efficacy of doxycycline in the treatment of MDR infections with GNB.

Carbapenem-Resistant enterobacterales in individuals with and without health care risk factors -Emerging infections program, United States, 2012-2015

BACKGROUND

Carbapenem-resistant Enterobacterales (CRE) are usually healthcare-associated but are also emerging in the community.

METHODS

Active, population-based surveillance was conducted to identify case-patients with cultures positive for Enterobacterales not susceptible to a carbapenem (excluding ertapenem) and resistant to all third-generation cephalosporins tested at 8 US sites from January 2012 to December 2015. Medical records were used to classify cases as health care-associated, or as community-associated (CA) if a patient had no known health care risk factors and a culture was collected <3 days after hospital admission. Enterobacterales isolates from selected cases were submitted to CDC for whole genome sequencing.

RESULTS

We identified 1499 CRE cases in 1194 case-patients; 149 cases (10%) in 139 case-patients were CA. The incidence of CRE cases per 100,000 population was 2.96 (95% CI: 2.81, 3.11) overall and 0.29 (95% CI: 0.25, 0.35) for CA-CRE. Most CA-CRE cases were in White persons (73%), females (84%) and identified from urine cultures (98%). Among the 12 sequenced CA-CRE isolates, 5 (42%) harbored a carbapenemase gene.

CONCLUSIONS

Ten percent of CRE cases were CA; some isolates from CA-CRE cases harbored carbapenemase genes. Continued CRE surveillance in the community is critical to monitor emergence outside of traditional health care settings.

Role of tigecycline in the treatment of urinary tract infections: a systematic review of published case reports

INTRODUCTION

The emergence of multi-drug resistance has forced clinicians to occasionally use drugs that are not approved to treat urinary tract infections (UTIs). This systematic review aimed to evaluate the utility of tigecycline in patients with UTIs.

METHODOLOGY

A systematic review of case studies was used to retrieve articles between 1.1.1999 to 1.1.2021 from two databases, PubMed and Embase. The title-abstract screening was done for 198 articles, out of which 69 articles were included for full-text screening. A total of 18 articles with 27 cases were included for final analysis.

RESULTS

Of the 27 cases, there were 13 cases with complicated UTI and five had catheter-associated UTI. The most common organisms were Klebsiella pneumoniae (n=11), Acinetobacter baumannii (n=9), and Escherichia coli (n=6). Tigecycline was used as monotherapy in 19 patients and as a combination therapy in 8 patients. The median duration of tigecycline was 13 (10-15) days. A favourable clinical or microbiological response at varying intervals was seen in 24/27 (88.9%). Within three months of a favourable response, recurrence of symptoms was seen in four patients.

CONCLUSION

In a small analysis of published case reports, tigecycline appeared to be a relatively effective treatment in patients with UTIs, caused by multidrug-resistant organisms. Where tigecycline is the only susceptible drug, it can be used for treatment. Further research, such as randomized controlled trials, is needed to fully assess the drug's efficacy in this context.

Effect of Colistin, Fosfomycin and Meropenem/Vaborbactam on Carbapenem-Resistant Enterobacterales in Egypt: A Cross-Sectional Study

Purpose

The increasing multi-drug carbapenem resistance among Enterobacterales are a severe health problem limiting therapeutic options and worsen the prognosis. This study characterizes carbapenemase genes and integrons among uropathogenic carbapenem resistant Enterobacterales (CRE) isolates recovered from Mansoura University Hospitals and evaluates the effect of colistin, fosfomycin and meropenem-vaborbactam on these isolates.

Patients and Methods

A total of 200 Enterobacterales isolates were collected from patients with urinary tract infections. Antimicrobial susceptibility testing was performed by the disc diffusion method. Colistin susceptibility was tested using the broth microdilution method and fosfomycin and meropenem/vaborbactam susceptibility were tested by MIC Test Strips. Carbapenem resistant isolates were screened for carbapenemase activity phenotypically using the modified carbapenem inactivation method and EDTA-modified carbapenem inactivation method and genotypically by multiplex PCR. Integrons class 1 and 2 and fosA gene were assayed by PCR. Data were statistically analyzed using the Statistical Package for Social Sciences (SPSS) version 16. The Chi-square or Fisher's exact test was used to compare groups, as appropriate.

Results

Ninety-two Enterobacterales isolates were resistant to meropenem (46%); 52 E. coli and 40 K. pneumoniae strains. All CRE isolates were multi-drug resistant (MDR). Sensitivity of CRE isolates to colistin, fosfomycin and meropenem/vaborbactam were 67.4%, 82.6% and 58.7%, respectively. Carbapenemase genes were detected by multiplex PCR in 69.6% of CRE isolates (Carbapenemase producing Enterobacterales (CPE) mainly blaNDM (37%). CPE isolates were significantly more resistant to meropenem/vaborbactam than non-CPE isolates; 51.6% vs 17.8%, respectively (P = 0.003) especially blaNDM carrying isolates (70.6%). Class 1 integrons and fosA gene were detected in 91.3% and 11.9% of CRE isolates, respectively.

Conclusion

This study revealed that about half of the uropathogenic Enterobacterales isolates were MDR CRE. Carbapenemase gene blaNDM was the main gene among CRE isolates. Meropenem/vaborbactam sensitivity was significantly higher on non-CPE than CPE isolates and limited by the predominance of blaNDM .

Treatment of UTIs Due to Klebsiella pneumoniae Carbapenemase-Producers: How to Use New Antibiotic Drugs? A Narrative Review

Background: K. pneumoniae is one of the bacteria most frequently causing health care-associated urinary tract infections, and increasingly incriminating Klebsiella pneumoniae carbapenemase producers (KPCp). Most infections caused by KPCp are nosocomial and might cause serious issues, even leading to death in half of the reported cases. Our aim was to identify the best strategy, based on available scientific data, for the use of new antibiotic treatments to manage KPCp UTIs. Methods: this narrative review of the literature was performed according to the criteria of preferred reporting items for systematic review and meta-analyses statement (PRISMA) (2020). Results and Conclusions: KPCp-UTIs are a real challenge for physicians. While cefiderocol, meropenem-vaborbactam, ceftazidim-avibactam, and imipenem-relebactam represent a major step forward in the treatment of these UTIs, no guidelines are currently available, in view of choosing the most appropriate treatment, in each specific case.

Present and Future Perspectives on Therapeutic Options for Carbapenemase-Producing Enterobacterales Infections

Carbapenem-resistant Enterobacterales (CRE) are included in the list of the most threatening antibiotic resistance microorganisms, being responsible for often insurmountable therapeutic issues, especially in hospitalized patients and immunocompromised individuals and patients in intensive care units. The enzymatic resistance to carbapenems is encoded by different β-lactamases belonging to A, B or D Ambler class. Besides compromising the activity of last-resort antibiotics, CRE have spread from the clinical to the environmental sectors, in all geographic regions. The purpose of this review is to present present and future perspectives on CRE-associated infections treatment.

Antimicrobial susceptibility pattern of carbapenemase-producing Gram-negative nosocomial bacteria at Al Zahra hospital, Isfahan, Iran

BACKGROUND AND OBJECTIVES

Bacterial antibiotic resistance is one of the most important threats for public health around the world. Carbapenemase-producing Gram-negative bacteria have resistance to most antibiotics including carbapenems complicating the treatment of infections. The aim of this study was to determine the antimicrobial susceptibility pattern of carbapenemase-producing nosocomial Gram-negative pathogens at a referral teaching hospital to reveal the best options for treatment of related infections.

MATERIALS AND METHODS

Gram-negative bacteria, isolated from hospitalized patients with nosocomial infections, underwent meropenem susceptibility test by disk diffusion method. Meropenem-resistant strains were evaluated for the presence of carbapenemase using Modified Hodge test (MHT). Finally, the antibiotic susceptibility test was performed to determine the sensitivity of each carbapenemase-positive strain against various antimicrobial agents according to the guidelines of Clinical and Laboratory Standards Institute (CLSI).

RESULTS

Over the study period, 155 carbapenemase-positive isolates were detected. Pneumonia was the most frequent related nosocomial infection (67.1%) followed by UTI (23.2%). Acinetobacter baumannii (53.5%) and Klebsiella pneumoniae (40%) were the most frequently isolated pathogens. The pathogens had high rate of resistance to all antibiotics. Colistin had the most in vitro effect against all pathogens. Also, K. pneumoniae had a co-trimoxazole sensitivity rate equal to colistin (30.6%).

CONCLUSION

Carbapenemase-positive Gram-negative bacteria causing nosocomial infections are common in our hospital and have high rate of resistance to most antibiotics. Improvement in the pattern of antibiotic use and infection control measures are necessary to overcome this resistance.

Efficacy and safety of tigecycline for complicated urinary tract infection: a systematic review

Background

Facing the global threat of emerging resistance to antibiotics, tigecycline, a novel glycylcycline antibiotic, is developed to against multidrug-resistant pathogens, but not recommended for the treatment of complicated urinary tract infection (cUTI). We performed a summary of the literatures to characterize and evaluate the efficacy and safety of tigecycline in patients with cUTI.

Methods

We searched PubMed, EMBASE, Cochrane and Clinical Trials using appropriate syntax to retrieve potential articles up to Jan 2020. General information, pathogen, medication regimen, comorbidities of patients from eligible literatures were recorded. Univariate logistic regression analysis was used to detect the potential factors associated with clinical cure.

Results

Nineteen articles comprising 31 cases were included. The subpopulation with transplantation (25.8% of the patients) was the most common comorbidity, and cUTIs were mainly caused by Klebsiella pneumoniae (K. pneumoniae) (48.28%) in our research. Tigecycline 100 mg per day as monotherapy was most common. Clinical cure was reported as majority (77.4%), and microbiological eradication cases accounted for the most (65.2%) among the clinical cure cases. Univariate analysis showed that K. pneumoniae caused cUTI and tigecycline as a single treatment have significant meaning to clinical outcomes (P=0.044 and P=0.034, respectively).

Conclusions

Clinical and microbiological outcomes of tigecycline treatment revealed high rate of successful response. Tigecycline monotherapy may have a role in the treatment of cUTI except that caused by the pathogen K. pneumoniae. Further randomized controlled trials was still needed to evaluate tigecycline monotherapy for cUTI.

Treatment outcome and predictors of poor clinical response in extensively drug-resistant gram-negative urinary tract infection among children: A single-institution experience

INTRODUCTION

Extensively drug-resistant (XDR) is defined as isolates sensitive only to two or fewer antimicrobial categories. This paper aims to present the treatment outcome and identify factors associated with poor clinical response among children with XDR gram-negative urinary tract infection (UTI).

METHODS

This is a retrospective cohort conducted at a tertiary pediatric hospital from January 2014 to June 2017. All patients diagnosed with culture-proven XDR gram-negative UTI were identified and analyzed. Descriptive statistics were used to summarize demographic and clinical characteristics. Patients were categorized according to treatment outcomes: success vs. failure. Univariate analysis and multivariate logistic regression were used to assess statistical differences between the groups and determined patient variables that are predictive of poor response. Odds ratio (OR) and corresponding 95% confidence interval (CI) were generated.

RESULTS

A total of 29 (19.2%) XDR gram-negative pediatric UTIs were identified within the 42-month study period. No significant differences were noted in demographic characteristics between the groups. Treatment outcome of XDR gram-negative UTI patients showed that combination therapy with colistin had the highest success rate (40.9%), followed by non-colistin (36.4%) and combination therapy without colistin (22.7%). However, univariate analysis showed no significant difference among the different treatment groups (p=0.65). On multivariate logistic regression, receiving immunosuppressant and the presence of indwelling urinary catheters were independent predictors of poor clinical response among pediatric patients with XDR gram-negative UTI (OR 19.44, 95% CI 1.50-251.4, p=0.023 and OR 20.78, 95% CI 1.16-371.28, p=0.039; respectively).

CONCLUSIONS

The treatment success rate of XDR gram-negative pediatric UTI ranged from 22.7-36.4%. This finding emphasizes the need to advocate antibiotic stewardship to prevent further increase in XDR UTIs. Indwelling urinary catheters and receipt of immunosuppressants are associated with poor clinical outcome.

Mortality, clinical and microbiological response following antibiotic therapy among patients with carbapenem-resistant Klebsiella pneumoniae infections (a meta-analysis dataset)

This meta-analysis was conducted to assess mortality, clinical and microbiological response following antibiotic therapy among patients with carbapenem-resistant Klebsiella pneumoniae (CRKP) infections. Fifty-four observational studies involving 3195 CRKP-infected patients who received antibiotic treatment were included. We found combination therapy to be associated with lower mortality than monotherapy, but no differences in clinical and microbiological response. Among the various combination therapies, no significant differences in mortality, clinical and microbiological response were found. Moreover, clinical outcomes did not differ significantly among various monotherapies. This report describes the data related to the article entitled: "A systematic review and meta-analysis of treatment outcomes following antibiotic therapy among patients with carbapenem-resistant Klebsiella pneumoniae infections".

Optimizing therapy in carbapenem-resistant Enterobacteriaceae infections

PURPOSE OF REVIEW

In the absence of randomized clinical trial data, questions remain regarding the optimal treatment of carbapenem-resistant Enterobacteriaceae (CRE) infections. CRE have historically been susceptible to polymyxins, tigecycline or aminoglycosides (mostly gentamicin), and these antibiotics have long been considered the drugs of choice for CRE infections, although varying rates of resistance to all have been reported. This review looks at data from clinical studies assessing the outcomes of CRE infections treated with different antibiotic regimens.

RECENT FINDINGS

The recently approved fixed-dose combination agent, ceftazidime-avibactam (CAZ-AVI), is active against KPC and OXA-48-producing Enterobacteriaceae. The limited clinical data available on CAZ-AVI indicate that it is associated with survival benefits relative to other commonly used regimens, although development of resistance is a concern. New drugs active against CRE isolates (including the recently approved meropenem-vaborbactam) are in different stages of development.

SUMMARY

CAZ-AVI and meropenem-vaborbactam seem destined to become the backbone of target therapy for high-risk patients with severe infections caused by susceptible CRE strains. However, empirical therapy should be based on risk factors to be defined in the near future, whereas the necessity of combinations with CAZ-AVI requires further studies. Polymyxins are still important options for low-risk patients with susceptible CRE infections, but also for high-risk patients in regions where metallo-β-lactamase-producing CRE predominate because CAZ-AVI and meropenem-vaborbactam are both ineffective against these strains.

Activity of fosfomycin alone or combined with temocillin in vitro and in a murine model of peritonitis due to KPC-3- or OXA-48-producing Escherichia coli

Background

Alternative therapeutic regimens are urgently needed against carbapenemase-producing Enterobacteriaceae. Fosfomycin often remains active against KPC and OXA-48 producers, but emergence of resistance is a major limitation. Our aim was to determine whether the association of temocillin with fosfomycin might be useful to treat KPC- or OXA-48-producing Escherichia coli infections.

Methods

Isogenic derivatives of E. coli CFT073 with blaKPC-3- or blaOXA-48-harbouring plasmids (named CFT073-KPC-3 and CFT073-OXA-48, respectively) were used. The addition of temocillin to fosfomycin was tested using the chequerboard method and time-kill curves as well as in a fatal peritonitis murine model. Mice were treated for 24 h with fosfomycin alone or in combination with temocillin. Bacterial loads, before and after treatment, were determined in the peritoneal fluid and fosfomycin-resistant mutants were detected.

Results

Temocillin MICs were 8, 32 and 256 mg/L for CFT073 (WT), CFT073-KPC-3 and CFT073-OXA-48, respectively. Fosfomycin MIC was 0.5 mg/L for all strains. The chequerboard experiments demonstrated synergy for all three strains. In time-kill curves, combining temocillin with fosfomycin was synergistic, bactericidal and prevented emergence of resistance for CFT073-pTOPO and CFT073-KPC-3, but not CFT073-OXA-48. In vivo, for the three strains, bacterial counts were lower in peritoneal fluid with the combination compared with fosfomycin alone (P < 0.001) and inhibited growth of resistant mutants in all cases.

Conclusions

The combination of fosfomycin and temocillin demonstrated a benefit in vitro and in vivo against E. coli strains producing KPC-3 or OXA-48-type carbapenemases. This combination prevented the emergence of fosfomycin resistance and proved to be more bactericidal than fosfomycin alone.

Comparative Epidemiology and Resistance Trends of Common Urinary Pathogens in a Tertiary-Care Hospital: A 10-Year Surveillance Study

Background and Objective: Urinary tract infections (UTIs) are common in human medicine, affecting large patient populations worldwide. The principal cause of UTIs is uropathogenic Escherichia coli (UPEC) and Klebsiella, both in community and nosocomial settings. The assessment of local data on prevalence and resistance is essential to evaluate trends over time and to reflect on the national situation, compared to international data, using the methods of analytical epidemiology. Materials and Methods: The aim of this study was to assess resistance trends and epidemiology of UTIs caused by E. coli and Klebsiella species in inpatients and outpatients at a tertiary-care hospital in Hungary, using microbiological data. To evaluate resistance trends, several antibiotics were chosen as indicator drugs, based on local utilization data. Results: E. coli was the most prevalent isolate, representing 56.75 ± 4.86% for outpatients and 42.29 ± 2.94% for inpatients. For E. coli, the ratio of resistant strains for several antibiotics was significantly higher in the inpatient group, while in Klebsiella, similar trends were only observed for gentamicin. Extended-spectrum β-lactamase (ESBL)-producing isolates were detected in 4.33-9.15% and 23.22-34.22% from outpatient, 8.85-38.97% and 10.89-36.06% from inpatient samples for E. coli and Klebsiella, respectively. Conclusions: Resistance developments in common UTI pathogens (especially to fosfomycin, sulfamethoxazole-trimethoprim, fluoroquinolones, and 3rd generation cephalosporins), seriously curb therapeutic options, especially in outpatient settings.

The "Old" and the "New" Antibiotics for MDR Gram-Negative Pathogens: For Whom, When, and How

The recent expansion of multidrug resistant and pan-drug-resistant pathogens poses significant challenges in the treatment of healthcare associated infections. An important advancement, is a handful of recently launched new antibiotics targeting some of the current most problematic Gram-negative pathogens, namely carbapenem-producing Enterobacteriaceae (CRE) and carbapenem-resistant P. aeruginosa (CRPA). Less options are available against carbapenem-resistant Acinetobacter baumannii (CRAB) and strains producing metallo-beta lactamases (MBL). Ceftazidime-avibactam signaled a turning point in the treatment of KPC and partly OXA- type carbapenemases, whereas meropenem-vaborbactam was added as a potent combination against KPC-producers. Ceftolozane-tazobactam could be seen as an ideal beta-lactam backbone for the treatment of CRPA. Plazomicin, an aminoglycoside with better pharmacokinetics and less toxicity compared to other class members, will cover important proportions of multi-drug resistant pathogens. Eravacycline holds promise in the treatment of infections by CRAB, with a broad spectrum of activity similar to tigecycline, and improved pharmacokinetics. Novel drugs and combinations are not to be considered "panacea" for the ongoing crisis in the therapy of XDR Gram-negative bacteria and colistin will continue to be considered as a fundamental companion drug for the treatment of carbapenem-resistant Enterobacteriaceae (particularly in areas where MBL predominate), for the treatment of CRPA (in many cases being the only in vitro active drug) as well as CRAB. Aminoglycosides are still important companion antibiotics. Finally, fosfomycin as part of combination treatment for CRE infections and P. aeruginosa, deserves a greater attention. Optimal conditions for monotherapy and the "when and how" of combination treatments integrating the novel agents will be discussed.

The antibiotic arms race: current and emerging therapy for Klebsiella pneumoniae carbapenemase (KPC) - producing bacteria

Introduction: The rapid spread of Klebsiella pneumoniae Carbapenemase (KPC)-producing bacteria comprises one of the greatest challenges to global health. Historically, clinicians were limited to therapies with suboptimal efficacy and intolerable toxicity until the FDA approved ceftazidime-avibactam and meropenem-vaborbactam, adding two essential pharmacotherapies to our antibiotic armamentarium. These agents display superior efficacy and safety compared to historical treatment options; however, resistance has already been reported. Several antimicrobials currently in the drug pipeline exhibit early promise and may fill needed gaps in therapy. Areas covered: This article encompasses both the past and present treatment options for the management of KPC-producing bacterial infections via an extensive review and critical appraisal of the current literature. Expert opinion: Traditional treatment options can no longer be recommended as first-line options for the management of KPC-producing bloodstream infections. Ceftazidime-avibactam or meropenem-vaborbactam plus or minus an aminoglycoside or polymyxin should be utilized as backbone therapies given their superior efficacy and safety profiles when compared to traditional treatment options. For susceptible KPC-producing urinary tract infections, it is reasonable to consider treatment with an aminoglycoside or with fosfomycin as a monotherapy. All of these decisions should be based on patient-specific characteristics, severity of infection and source control, susceptibility patterns, and input from infectious diseases experts.

Meropenem-vaborbactam for adults with complicated urinary tract and other invasive infections

INTRODUCTION

Complicated urinary tract infections are increasingly caused by multidrug-resistant organisms. Carbapenem-resistant Enterobacteriaceae (CRE) constitute a rising threat among uropathogens with significant morbidity and mortality. Meropenem-vaborbactam is a novel carbapenem and cyclic boronic acid-based beta-lactamase inhibitor combination with potent activity against subtypes of CRE. Areas covered: This article reviews mechanisms of carbapenem resistance, existing treatment options for CRE, and the current evidence to support the use of meropenem-vaborbactam for the treatment of infections caused by subtypes of CRE including complicated urinary tract infections. Expert commentary: Meropenem-vaborbactam is a superior treatment option for infections secondary to Klebsiella pneumoniae carbapenemase (KPC)-producing CRE. It is associated with higher rates of treatment success and lower rates of toxicity than traditional agents and demonstrates a potentially higher barrier to acquired antimicrobial resistance than ceftazidime-avibactam. At present, meropenem-vaborbactam should be regarded as a preferred treatment option for invasive infections secondary to KPC-producing CRE.

In Vivo Efficacy of Meropenem with a Novel Non-β-Lactam-β-Lactamase Inhibitor, Nacubactam, against Gram-Negative Organisms Exhibiting Various Resistance Mechanisms in a Murine Complicated Urinary Tract Infection Model

Urinary tract infections (UTIs) are a tremendous burden on the health care system due to the vast number of infections resulting in antibiotic therapy and/or hospitalization. Additionally, these infections are frequently caused by multidrug-resistant (MDR) organisms, limiting the availability of effective antimicrobials. Nacubactam is a novel non-β-lactam-β-lactamase inhibitor with in vitro activity against class A and class C β-lactamases. Nacubactam is being developed in combination with meropenem, providing broad-spectrum activity in addition to improved stability against common β-lactamases. Here, we utilized a neutropenic murine complicated UTI (cUTI) model to determine the potential clinical utility of meropenem-nacubactam compared with meropenem or nacubactam alone against 10 Klebsiella pneumoniae, Escherichia coli, and Enterobacter cloacae isolates with diverse genotypic and phenotypic profiles, including NDM, KPC, OXA, CTX-M, SHV, and TEM enzyme-producing isolates. Selected isolates had meropenem-nacubactam MICs between 1 and 8 μg/ml. Meropenem-nacubactam demonstrated the greatest in vivo efficacy against 9 of 10 isolates, achieving a ≥3 log reduction from the 48-h control in all isolates tested, including isolates prepared as high inoculums. Nacubactam alone confirmed antibacterial properties, achieving a >1 log reduction against the majority of isolates. The combination of meropenem-nacubactam further enhanced the activity of either agent alone, notably against meropenem-resistant isolates. Against ceftazidime-avibactam-resistant isolates, meropenem-nacubactam demonstrated increased antibacterial kill upwards of 6 log₁₀ CFU in comparison to the 48-h control. Our data support the potential clinical utility of meropenem-nacubactam for cUTI in humans against MDR Enterobacteriaceae, although further clinical data supporting meropenem-nacubactam efficacy are needed.

Molecular Epidemiology of Plasmid-Mediated Fosfomycin Resistance Gene Determinants in Klebsiella pneumoniae Carbapenemase-Producing Klebsiella pneumoniae Isolates in China

The Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae has become a serious problem because the species is wide ranging and there are few treatment options. Fosfomycin has attracted renewed interest in combination therapy for infections caused by KPC-producing K. pneumoniae isolates. Because of the increasing use of fosfomycin, resistant isolates have been continually reported in carbapenem-resistant K. pneumoniae (CRKP). At present, multiple mechanisms can result in fosfomycin resistance. However, there is limited knowledge with respect to plasmid-mediated fosfomycin resistance gene (fosA3) determinants in KPC-producing K. pneumoniae isolates. In this study, a total of 101 CRKP strains were collected from four hospitals in Zhejiang province from January 2013 to August 2014; 28.7% (29/101) of CRKP isolates were resistant to fosfomycin. Gene fosA3 was detected in 29 fosfomycin-resistant KPC-producing K. pneumoniae isolates, whereas genes fosA, fosB, fosB2, fosC, fosC2, and fosX were all negative among the resistant isolates. In addition, among 29 fosfomycin-resistant KPC-producing K. pneumoniae isolates, pulsed-field gel electrophoresis (PFGE) analysis revealed five pulsotypes. S1-PFGE and Southern blot showed that the fosA3 gene was located on an approximately 140-kb plasmid in all isolates. Eight of the 29 isolates (27.6%) tested could successfully transfer their fosfomycin-resistant phenotype to Escherichia coli strain J53. All fosA3-positive isolates were determined to have an identical genetic background, IS26-tetR-cadC-orf1-fosA3-IS26, which is the same as that of the fosA3-positive plasmid pFOS18 in China. The primary resistance mechanism to fosfomycin was caused by a plasmid-mediated fosA3. Furthermore, it is noteworthy that the plasmid genetically carrying a combination of the fosA3 and bla_KPC-2 genes could accelerate the spread of antibiotic resistance. Effective and persistent monitoring and surveillance will be vital to prevent further dissemination of these resistance genes.

The Epidemiology, Evolution, and Treatment of KPC-Producing Organisms

PURPOSE OF REVIEW

The purpose of this review is to investigate the evolution and epidemiology of Klebsiella pneumoniae carbapenemase (KPC)-producing organisms and the current and future treatment options for infections caused by KPC-producing isolates.

RECENT FINDINGS

The emergence of resistance in Enterobacteriaceae producing carbapenemases globally has increased the challenges in treating infections caused by these organisms. One of the prominent mechanisms of resistance is the production of KPC enzymes. Infections caused by organisms producing KPCs have limited treatment options and are associated with poor clinical outcomes. The rapid rise of KPC-producing organisms necessitated the use of drugs with pharmacokinetic and toxicity limitations, including polymyxins, tigecycline, fosfomycin, and aminoglycosides. The availability of new beta-lactamase inhibitor combinations that are effective against KPC-producing organisms represent an advance in safety and efficacy. Several agents are currently being studied that have activity against KPC-producing organisms and appear to represent promising additions to our armamentarium. KPC-producing organisms cause infections with high morbidity and mortality. Limited treatment options are available, though new therapies have been developed. Pipeline agents are likely to have a place in therapy for the treatment of infections caused by KPC-producing isolates.

Mechanisms of fosfomycin resistance in carbapenem-resistant Enterobacter sp

We report on fosfomycin susceptibility and mechanisms of resistance in clinical strains of bla_KPC-positive Enterobacter sp. (n = 19). A total of 14 strains (74%) were susceptible to fosfomycin; 8 strains (42%) were positive for fosA and no strains were positive for FosA3 or FosC2. FosA presence does not appear to correlate with susceptibility.

Activity of minocycline against Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae clinical isolates, with comparison to doxycycline and tigecycline

We examined the in vitro activity of minocycline against 103 Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae isolates and found approximately half had susceptible (26%) or intermediate (26%) MICs. For a subset of 35 isolates, susceptibility was highest to tigecycline (71% FDA vs. 20% EUCAST) followed by minocycline (14%) and then doxycycline (6%).

Aminoglycosides against carbapenem-resistant Enterobacteriaceae in the critically ill: the pitfalls of aminoglycoside susceptibility

INTRODUCTION

The emergence of carbapenem-resistant Enterobacteriaceae (CRE) has brought aminoglycosides to the frontline since an aminoglycoside may be the only antimicrobial to which CRE isolates show in vitro susceptibility. The appropriateness of aminoglycoside-based therapies for severe infections by CRE is discussed considering the current breakpoints and recent pharmacokinetic (PK) studies in critically ill patients. Areas covered: Many aminoglycoside-susceptible CRE isolates present minimal inhibitory concentrations (MICs) at or slightly below the breakpoint of amikacin or gentamicin. However, recent PK studies with these aminoglycosides in critically ill have invariably shown that the PK/pharmacodynamic (PD) target is very unlikely attained even when high doses are administered, if the MICs are near the breakpoint. Expert commentary: While new antimicrobials are not widely available, the authors forecast an increasing use of aminoglycosides as backbone antibiotics against CRE isolates. However, the altered PK of aminoglycosides in critically ill patients severely impairs their predicted efficacy in these patients. Aminoglycoside breakpoints may hide 'aminoglycoside-susceptible' CRE isolates for that aminoglycosides will unlikely be effective if used in monotherapy. Therefore, these breakpoints may need to be revised due to the increasing use of aminoglycosides as backbone antibiotics to treat severe infections by CRE isolates in critically ill patients.

Fosfomycin: Resurgence of an old companion

Fosfomycin was discovered over four decades ago, yet has drawn renewed interest as an agent active against a range of multidrug-resistant (MDR) and extensively drug-resistant (XDR) pathogens. Its unique mechanism of action and broad spectrum of activity makes it a promising candidate in the treatment of various MDR/XDR infections. There has been a surge of in vitro data on its activity against MDR/XDR organisms, both when used as a single agent and in combination with other agents. In the United States, fosfomycin is only approved in an oral formulation for the treatment of acute uncomplicated urinary tract infections (UTIs), whereas in some countries both oral and intravenous formulations are available for various indications. Fosfomycin has minimal interactions with other medications and has a relatively favorable safety profile, with diarrhea being the most common adverse reaction. Fosfomycin has low protein binding and is excreted primarily unchanged in the urine. The clinical outcomes of patients treated with fosfomycin are favorable for uncomplicated UTIs, but data are limited for use in other conditions. Fosfomycin maintains activity against most Enterobacteriaceae including Escherichia coli, but plasmid-mediated resistance due to inactivation have appeared in recent years, which has the potential to compromise its use in the future. In this review, we summarize the current knowledge of this resurgent agent and its role in our antimicrobial armamentarium.

fosI Is a New Integron-Associated Gene Cassette Encoding Reduced Susceptibility to Fosfomycin

In this work, we demonstrate that the fosI gene encodes a predicted small protein with 134 amino acids and determines reduced susceptibility to fosfomycin. It raised the MIC from 0.125 to 6 μg/ml when the pBRA100 plasmid was introduced into Escherichia coli TOP10 and to 16 μg/ml when the gene was cloned into the pBC_SK(-) vector and expressed in E. coli TOP10.

Antibiotic regimens for treatment of infections due to multidrug-resistant Gram-negative pathogens: An evidence-based literature review

Evidences regarding the efficacy of different antibiotic regimens proposed for treatment of multidrug-resistant (MDR) Gram-negative pathogens have been reviewed. Available data in Scopus, Medline, EMBASE, the Cochrane central register of controlled trials, and Cochrane database of systematic reviews have been collected. Several antibiotic regimens are proposed for treatment of MDR Gram-negative infections (defined as nonsusceptibility to at least one agent in three or more antimicrobial categories). The most challenging issue is the treatment of carbapenem-resistant (CR) Gram-negative pathogens. A carbapenem plus either colistin or tigecycline was the most effective regimen for treatment of CR Gram-negative pathogens with low-level resistance (minimal inhibitory concentration [MIC] ≤ 8 mg/L). However, in high-level resistance (MIC > 8 mg/L), combination of colistin and tigecycline showed promising effect.

Current and future antimicrobial treatment of gonorrhoea - the rapidly evolving Neisseria gonorrhoeae continues to challenge

Neisseria gonorrhoeae has developed antimicrobial resistance (AMR) to all drugs previously and currently recommended for empirical monotherapy of gonorrhoea. In vitro resistance, including high-level, to the last option ceftriaxone and sporadic failures to treat pharyngeal gonorrhoea with ceftriaxone have emerged. In response, empirical dual antimicrobial therapy (ceftriaxone 250–1000 mg plus azithromycin 1–2 g) has been introduced in several particularly high-income regions or countries. These treatment regimens appear currently effective and should be considered in all settings where local quality assured AMR data do not support other therapeutic options. However, the dual antimicrobial regimens, implemented in limited geographic regions, will not entirely prevent resistance emergence and, unfortunately, most likely it is only a matter of when, and not if, treatment failures with also these dual antimicrobial regimens will emerge. Accordingly, novel affordable antimicrobials for monotherapy or at least inclusion in new dual treatment regimens, which might need to be considered for all newly developed antimicrobials, are essential. Several of the recently developed antimicrobials deserve increased attention for potential future treatment of gonorrhoea. In vitro activity studies examining collections of geographically, temporally and genetically diverse gonococcal isolates, including multidrug-resistant strains particularly with resistance to ceftriaxone and azithromycin, are important. Furthermore, understanding of effects and biological fitness of current and emerging (in vitro induced/selected and in vivo emerged) genetic resistance mechanisms for these antimicrobials, prediction of resistance emergence, time-kill curve analysis to evaluate antibacterial activity, appropriate mice experiments, and correlates between genetic and phenotypic laboratory parameters, and clinical treatment outcomes, would also be valuable. Subsequently, appropriately designed, randomized controlled clinical trials evaluating efficacy, ideal dose, toxicity, adverse effects, cost, and pharmacokinetic/pharmacodynamics data for anogenital and, importantly, also pharyngeal gonorrhoea, i.e. because treatment failures initially emerge at this anatomical site. Finally, in the future treatment at first health care visit will ideally be individually-tailored, i.e. by novel rapid phenotypic AMR tests and/or genetic point of care AMR tests, including detection of gonococci, which will improve the management and public health control of gonorrhoea and AMR. Nevertheless, now is certainly the right time to readdress the challenges of developing a gonococcal vaccine.

Antimicrobial resistance in Neisseria gonorrhoeae in the 21st century: past, evolution, and future

Neisseria gonorrhoeae is evolving into a superbug with resistance to previously and currently recommended antimicrobials for treatment of gonorrhea, which is a major public health concern globally. Given the global nature of gonorrhea, the high rate of usage of antimicrobials, suboptimal control and monitoring of antimicrobial resistance (AMR) and treatment failures, slow update of treatment guidelines in most geographical settings, and the extraordinary capacity of the gonococci to develop and retain AMR, it is likely that the global problem of gonococcal AMR will worsen in the foreseeable future and that the severe complications of gonorrhea will emerge as a silent epidemic. By understanding the evolution, emergence, and spread of AMR in N. gonorrhoeae, including its molecular and phenotypic mechanisms, resistance to antimicrobials used clinically can be anticipated, future methods for genetic testing for AMR might permit region-specific and tailor-made antimicrobial therapy, and the design of novel antimicrobials to circumvent the resistance problems can be undertaken more rationally. This review focuses on the history and evolution of gonorrhea treatment regimens and emerging resistance to them, on genetic and phenotypic determinants of gonococcal resistance to previously and currently recommended antimicrobials, including biological costs or benefits; and on crucial actions and future advances necessary to detect and treat resistant gonococcal strains and, ultimately, retain gonorrhea as a treatable infection.

Carbapenemase-producing Enterobacteriaceae

Carbapenemase-producing Enterobacteriaceae (CPE) were almost nonexistent up to the 1990s, but are today encountered routinely in hospitals and other healthcare facilities in many countries including the United States. KPC-producing Klebsiella pneumoniae was the first to emerge and spread globally and is endemic in the United States, Israel, Greece, and Italy. Recently, NDM-producing Enterobacteriaceae and OXA-48-producing K. pneumoniae appear to be disseminating from South Asia and Northern Africa, respectively. They are almost always resistant to all β-lactams including carbapenems and many other classes. Mortality from invasive CPE infections reaches up to 40%. To obtain the maximal benefit from the limited options available, dosing of antimicrobial agents should be optimized based on pharmacokinetic data, especially for colistin and carbapenems. In addition, multiple observational studies have associated combination antimicrobial therapy with lower mortality compared with monotherapy for these infections. The outcomes appear to be especially favorable when patients are treated with a carbapenem and a second agent such as colistin, tigecycline, and gentamicin, but the best approach is yet to be defined.

Efficacy of polymyxins in the treatment of carbapenem-resistant Enterobacteriaceae infections: a systematic review and meta-analysis

In recent years, carbapenem-resistant Enterobacteriaceae has become endemic in many countries. Because of limited treatment options, the abandoned "old antibiotics", polymyxins, have been reintroduced to the clinic. To evaluate the clinical efficacy of polymyxins in the treatment of infections caused by carbapenem-resistant Enterobacteriaceae, we systemically searched the PubMed, Embase, and Cochrane Library databases and analyzed the available evidence. The Preferred Reporting Items for Systematic reviews and Meta-Analysis statement were followed, and the I(2) method was used for heterogeneity. Nineteen controlled and six single-arm cohort studies comprising 1086 patients met the inclusion criteria. For controlled studies, no significant difference was noted for overall mortality (OR, 0.79; 95% CI, 0.58-1.08; p=0.15), clinical response rate (OR, 1.24; 95% CI, 0.61-2.54; p=0.55), or microbiological response rate (OR, 0.59; 95% CI, 0.26-1.36; p=0.22) between polymyxin-treated groups and the control groups. Subgroup analyses showed that 28-day or 30-day mortality was lower in patients who received polymyxin combination therapy than in those who received monotherapy (OR, 0.36; 95% CI, 0.19-0.68; p<0.01) and the control groups (OR, 0.49; 95% CI, 0.31-0.75; p<0.01). The results of the six single-arm studies were in accordance with the findings of controlled studies. One controlled and two single-arm studies that evaluated the occurrence of nephrotoxicity reported a pooled incidence rate of 19.2%. Our results suggest that polymyxins may be as efficacious as other antimicrobial therapies for the treatment of carbapenem-resistant Enterobacteriaceae infection. Compared to polymyxin monotherapy, combination regimens may achieve lower 28-day or 30-day mortality. Future large-volume, well-designed randomized control trials are required to determine the role of polymyxins in treating carbapenem-resistant Enterobacteriaceae infections.

Impact of therapy and strain type on outcomes in urinary tract infections caused by carbapenem-resistant Klebsiella pneumoniae

OBJECTIVES

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is an important healthcare-associated pathogen. We evaluated the impact of CRKP strain type and treatment on outcomes of patients with CRKP bacteriuria.

PATIENTS AND METHODS

Physician-diagnosed CRKP urinary tract infection (UTI)-defined as those patients who received directed treatment for CRKP bacteriuria-was studied in the multicentre, prospective Consortium on Resistance against Carbapenems in Klebsiella pneumoniae (CRaCKle) cohort. Strain typing by repetitive extragenic palindromic PCR (rep-PCR) was performed. Outcomes were classified as failure, indeterminate or success. Univariate and multivariate ordinal analyses to evaluate the associations between outcome, treatment and strain type were followed by binomial analyses.

RESULTS

One-hundred-and-fifty-seven patients with physician-diagnosed CRKP UTI were included. After adjustment for CDC/National Healthcare Safety Network (NHSN)-defined UTI, critical illness and receipt of more than one active antibiotic, patients treated with aminoglycosides were less likely to fail therapy [adjusted OR (aOR) for failure 0.34, 95% CI 0.15-0.73, P=0.0049]. In contrast, patients treated with tigecycline were more likely to fail therapy (aOR for failure 2.29, 95% CI 1.03-5.13, P=0.0425). Strain type data were analysed for 55 patients. The predominant clades were ST258A (n=18, 33%) and ST258B (n=26, 47%). After adjustment for CDC/NHSN-defined UTI and use of tigecycline and aminoglycosides, infection with strain type ST258A was associated with clinical outcome in ordinal analysis (P=0.0343). In multivariate binomial models, strain type ST258A was associated with clinical failure (aOR for failure 5.82, 95% CI 1.47-28.50, P=0.0113).

CONCLUSIONS

In this nested cohort study of physician-diagnosed CRKP UTI, both choice of treatment and CRKP strain type appeared to impact on clinical outcomes.

Carbapenem-resistant Klebsiella pneumoniae urinary tract infection following solid organ transplantation

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is an emerging pathogen with a devastating impact on organ transplant recipients (OTRs). Data describing urinary tract infections (UTIs) due to CRKP, compared to extended-spectrum β-lactamase (ESBL)-producing and susceptible K. pneumoniae, are lacking. We conducted a retrospective cohort study comparing OTRs with a first episode of UTI due to CRKP, ESBL-producing K. pneumoniae, or susceptible K. pneumoniae. We identified 108 individuals; 22 (20%) had UTIs due to CRKP, 22 (20%) due to ESBL-producing K. pneumoniae, and 64 (60%) due to susceptible K. pneumoniae. Compared to susceptible K. pneumoniae (27%), patients with UTIs due to CRKP or ESBL-producing K. pneumoniae were more likely to have a ≥ 24-hour stay in the intensive care unit (ICU) before or after development of the UTI (64% and 77%, respectively; P < 0.001). Among 105/108 hospitalized patients (97%), the median lengths of stay prior to UTI with CRKP or ESBL-producing K. pneumoniae (7 and 8 days, respectively) were significantly longer than that for susceptible K. pneumoniae (1 day; P < 0.001). Clinical failure was observed for 8 patients (36%) with CRKP, 4 (18%) with ESBL-producing K. pneumoniae, and 9 (14%) with susceptible K. pneumoniae (P = 0.073). Microbiological failure was seen for 10 patients (45%) with CRKP, compared with 2 (9%) with ESBL-producing K. pneumoniae and 2 (3%) with susceptible K. pneumoniae (P < 0.001). In multivariable logistic regression analyses, CRKP was associated with greater odds of microbiological failure (versus ESBL-producing K. pneumoniae: odds ratio [OR], 9.36, 95% confidence interval [CI], 1.94 to 72.1; versus susceptible K. pneumoniae: OR, 31.4, 95% CI, 5.91 to 264). In conclusion, CRKP is associated with ICU admission, long length of stay, and microbiological failure among OTRs with UTIs. Greater numbers are needed to determine risk factors for infection and differences in meaningful endpoints associated with carbapenem resistance.

Treatment for infections with carbapenem-resistant Enterobacteriaceae: what options do we still have?

The global spread of carbapenem-resistant Enterobacteriaceae (CRE) is increasingly becoming a major challenge in clinical and public health settings. To date, the treatment for serious CRE infections remains difficult. The intelligent use of antimicrobials and effective infection control strategies is crucial to prevent further CRE spread. Early consultation with experts in the treatment of infections with multidrug-resistant organisms is valuable in patient management. This brief review will focus on the current, yet limited, treatment options for CRE infections.

Infections with blaKPC-2-producing Klebsiella pneumoniae in renal transplant patients: a retrospective study

In renal transplant recipients, the urinary tract is the most common site of infections that might be caused by pathogens while on immunosuppressive therapy. The spread of enterobacteria resistant to carbapenem is worrying, as it is generally used as this agent is the first-line therapy for infections caused by Enterobacteriaceae producing extended spectrum β-lactamases. The most frequently encountered class A carbapenemases are the Klebsiella pneumoniae carbapenemase (KPC) enzymes. We describe the treatment and outcomes of 6 renal transplant patients who had urinary tract infections (UTIs) with blaKPC-2-producing K pneumoniae, confirmed by polymerase chain reaction amplification, namely 13.33% of renal transplant patients in the study period. Four patients survived, including 1 with reinfections and relapse, and 2 patients died. The antibiotics used for treatment, alone or combined, were colistin (n = 6, 42.8%), tigecycline (n = 5, 35.7%), doxycycline (n = 3, 21.4%), meropenem (n = 3, 21.4%), and fosfomycyn (n = 1, 7%). UTIs caused by carbapenemase-producing K pneumoniae are life-threatening. In the cases presented, favorable results were achieved with monotherapies using colistin, doxycycline, or meropenem.

Fosfomycin susceptibility in carbapenem-resistant Enterobacteriaceae from Germany

Due to the increase in multidrug-resistant Enterobacteriaceae, the interest in older antimicrobial agents, like fosfomycin, has increased. In this study, we used agar dilution for testing susceptibilities to fosfomycin in a collection of 107 carbapenem-nonsusceptible Enterobacteriaceae isolates, of which 80 produced various types of carbapenemases, including KPC, VIM, NDM, and OXA-48. Overall, 78% of the strains had fosfomycin MICs of ≤ 32 mg/liter and were thus considered to be susceptible according to the current EUCAST breakpoint. The MIC50 and MIC90 were 8 mg/liter and 512 mg/liter, respectively. Escherichia coli strains had significantly lower fosfomycin MICs than the Klebsiella pneumoniae and Enterobacter cloacae strains. Furthermore, comparisons of the susceptibility testing methods, like Etest and disk diffusion, were performed against agar dilution as the reference method. Essential agreement between Etest and agar dilution was 78.9%, and categorical agreement between the two methods was 92.5%, with 20% very major errors and 2.6% major errors. Disk diffusion was studied with 50-μg and 200-μg fosfomycin disks, but no inhibition zone breakpoint that reduced very major and major errors to an acceptable level was found. Etest and disk diffusion showed poor agreement with fosfomycin agar dilution.

Epidemiology and clinical outcomes of patients with carbapenem-resistant Klebsiella pneumoniae bacteriuria

Carbapenem-resistant Klebsiella pneumoniae (CRKP) bacteriuria is a frequently encountered clinical condition, but its clinical impact is unknown. We conducted a retrospective cohort study to define the epidemiology and outcomes for patients with CRKP bacteriuria. Patients with positive urine cultures for CRKP were classified as having asymptomatic bacteriuria (ASB) or symptomatic urinary tract infection (UTI). Among 105 patients with CRKP bacteriuria, 80% (84/105 patients) and 20% (21/105 patients) had ASB and UTI, respectively. Older age (P = 0.002) and higher Charlson's comorbidity index scores (P = 0.001) were associated with ASB. The median duration of hospitalization prior to CRKP bacteriuria was significantly longer for patients with ASB versus UTI (8.5 versus 2 days; P = 0.05). In multivariate analysis, male sex (odds ratio [OR], 4.69 [95% confidence interval (CI), 1.44 to 15.26]; P = 0.01), solid-organ transplantation (OR, 4.50 [95% CI, 1.39 to 14.52]; P = 0.01), and neurogenic bladder (OR, 18.62 [95% CI, 1.75 to 197.52]; P = 0.01) were independently associated with UTI. Ten percent (8/84) of the patients with ASB received antimicrobial therapy. The treatment success rate for patients with UTIs was 90% (19/21 patients), including all patients who received doxycycline (n = 9). The overall 30-day mortality rate was 6% (6/105 patients); the deaths were unrelated to CRKP infections. Secondary CRKP infections, including UTIs, were notably absent among patients with ASB who were followed for 90 days. In conclusion, identification of CRKP in the urine was most commonly associated with ASB and did not lead to subsequent infections or death among asymptomatic patients. Factors associated with UTIs included male sex, solid-organ transplantation, and neurogenic bladder. Doxycycline may be an effective therapy for CRKP UTIs.

Antibiotic treatment of infections due to carbapenem-resistant Enterobacteriaceae: systematic evaluation of the available evidence

We sought to evaluate the effectiveness of the antibiotic treatment administered for infections caused by carbapenemase-producing Enterobacteriaceae. The PubMed and Scopus databases were systematically searched. Articles reporting the clinical outcomes of patients infected with carbapenemase-producing Enterobacteriaceae according to the antibiotic treatment administered were eligible. Twenty nonrandomized studies comprising 692 patients who received definitive treatment were included. Almost all studies reported on Klebsiella spp. In 8 studies, the majority of infections were bacteremia, while pneumonia and urinary tract infections were the most common infections in 12 studies. In 10 studies, the majority of patients were critically ill. There are methodological issues, including clinical heterogeneity, that preclude the synthesis of the available evidence using statistical analyses, including meta-analysis. From the descriptive point of view, among patients who received combination treatment, mortality was up to 50% for the tigecycline-gentamicin combination, up to 64% for tigecycline-colistin, and up to 67% for carbapenem-colistin. Among the monotherapy-treated patients, mortality was up to 57% for colistin and up to 80% for tigecycline. Certain regimens were administered to a small number of patients in certain studies. Three studies reporting on 194 critically ill patients with bacteremia showed individually significantly lower mortality in the combination arm than in the monotherapy arm. In the other studies, no significant difference in mortality was recorded between the compared groups. Combination antibiotic treatment may be considered the optimal option for severely ill patients with severe infections. However, well-designed randomized studies of specific patient populations are needed to further clarify this issue.

Emerging resistance problems and future perspectives in pharmacotherapy for complicated urinary tract infections

INTRODUCTION

Urinary tract infections (UTIs) are among the most common infectious diseases and contribute to high financial burden worldwide. Administration of appropriate antibiotic therapy is the key to achieving good therapeutic outcomes. The authors review the current status of global or regional epidemiology, especially on the antimicrobial resistance and several potential agents against complicated UTIs by multidrug-resistant (MDR) pathogens.

AREAS COVERED

The authors summarized the susceptibility status on several major surveillance programs on uropathogens, focusing on Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant enterococci. Besides, the current perspectives of several potential antimicrobials against MDR uropathogens available for UTIs were also reviewed.

EXPERT OPINION

High resistance to broad-spectrum antibiotics, especially to extended-spectrum β-lactams, carbapenems, and fluoroquinolones among uropathogens emerges as a critical problem in many countries. Appropriate antimicrobial stewardship and continuous surveillance are necessary to monitor the trends of susceptibility for main pathogens. For these MDR uropathogens, polymyxin, fosfomycin, tigecycline, nitrofurantoin, linezolid, and daptomycin might be potential treatments for patients with uncomplicated and complicated UTIs in some countries, although they might not be approved by their regulation. However, more clinical evidence and more extensive meta-analyses are needed to evaluate and confirm the effectiveness of their usage in countries with a high prevalence of multidrug resistance.

Carbapenem-resistant Enterobacteriaceae: a review of treatment and outcomes

The emergence of carbapenem resistance in Enterobacteriaceae is an important threat to global health. Reported outcomes of infections with carbapenem-resistant Enterobacteriaceae (CRE) are poor. Very few options remain for the treatment of these virulent organisms. Antibiotics which are currently in use to treat CRE infections include aminoglycosides, polymyxins, tigecycline, fosfomycin, and temocillin. In addition, the role of combination therapy, including carbapenem containing regimens, remains to be defined. There are several important concerns regarding all of these treatment options such as limited efficacy, increasing reports of resistance, and specific toxicities. Data from retrospective studies favor combination therapy over single-agent therapy for the treatment of CRE bloodstream infections. In summary, new antibiotics are greatly needed, as is additional prospective research.

Treatment of Klebsiella pneumoniae carbapenemase (KPC) infections: a review of published case series and case reports

The emergence of Klebsiella pneumoniae carbapenemases (KPCs) producing bacteria has become a significant global public health challenge while the optimal treatment remains undefined. We performed a systematic review of published studies and reports of treatment outcomes of KPC infections using MEDLINE (2001–2011). Articles or cases were excluded if one of the following was fulfilled: no individual patient data provided, no treatment regimen specified, no treatment outcome specified, report of colonization, or greater than three antibiotics were used to treat the KPC infection. Data extracted included patient demographics, site of infection, organism, KPC subtype, antimicrobial therapy directed at KPC-infection, and treatment outcome. Statistical analysis was performed in an exploratory manner. A total of 38 articles comprising 105 cases were included in the analysis. The majority of infections were due to K. pneumoniae (89%). The most common site of infection was blood (52%), followed by respiratory (30%), and urine (10%). Forty-nine (47%) cases received monotherapy and 56 (53%) cases received combination therapy directed at the KPC-infection. Significantly more treatment failures were seen in cases that received monotherapy compared to cases who received combination therapy (49% vs 25%; p= 0.01). Respiratory infections were associated with higher rates of treatment failure with monotherapy compared to combination therapy (67% vs 29% p= 0.03). Polymyxin monotherapy was associated with higher treatment failure rates compared to polymyxin-based combination therapy (73% vs 29%; p= 0.02); similarly, higher treatment failure rates were seen with carbapenem monotherapy compared to carbapenem-based combination therapy (60% vs 26%; p= 0.03). Overall treatment failure rates were not significantly different in the three most common antibiotic-class combinations: polymyxin plus carbapenem, polymyxin plus tigecycline, polymyxin plus aminoglycoside (30%, 29%, and 25% respectively; p=0.6). In conclusion, combination therapy is recommended for the treatment of KPC infections; however, which combination of antimicrobial agents needs to be established in future prospective clinical trials.

Emergence of multidrug-resistant, extensively drug-resistant and untreatable gonorrhea

The new superbug Neisseria gonorrhoeae has retained resistance to antimicrobials previously recommended for first-line treatment and has now demonstrated its capacity to develop resistance to the extended-spectrum cephalosporin, ceftriaxone, the last remaining option for first-line empiric treatment of gonorrhea. An era of untreatable gonorrhea may be approaching, which represents an exceedingly serious public health problem. Herein, we review the evolution, origin and spread of antimicrobial resistance and resistance determinants (with a focus on extended-spectrum cephalosporins) in N. gonorrhoeae, detail the current situation regarding verified treatment failures with extended-spectrum cephalosporins and future treatment options, and highlight essential actions to meet the large public health challenge that arises with the possible emergence of untreatable gonorrhea. Essential actions include: implementing action/response plans globally and nationally; enhancing surveillance of gonococcal antimicrobial resistance, treatment failures and antimicrobial use/misuse; and improving prevention, early diagnosis and treatment of gonorrhea. Novel treatment strategies, antimicrobials (or other compounds) and, ideally, a vaccine must be developed.