Carbapenem-resistant and cephalosporin-susceptible Pseudomonas aeruginosa: a notable phenotype in patients with bacteremia

Treatment Outcomes for Carbapenem-Resistant and Cephalosporin-Susceptible Pseudomonas aeruginosa Pneumonia

BACKGROUND

Carbapenem-resistant (Car-R) Pseudomonas aeruginosa is an urgent threat. These isolates may remain susceptible to traditional noncarbapenem antipseudomonal β-lactams, but it is unclear if carbapenem resistance impacts the effectiveness of these agents.

OBJECTIVE

The purpose of this study was to compare clinical outcomes in Car-R and cephalosporin-susceptible (Ceph-S) P. aeruginosa pneumonia treated with cefepime versus other susceptible agents.

METHODS

This retrospective cohort study evaluated patients diagnosed with hospital-acquired or ventilator-associated pneumonia who had a respiratory isolate of Car-R Ceph-S P. aeruginosa. Patients were excluded if they had polymicrobial respiratory cultures, other concomitant infections, empyema, death within 3 days of index culture, or received less than 3 days of susceptible therapy. Patients treated with cefepime were compared to other susceptible therapies. The primary endpoint was 30-day in-hospital mortality.

RESULTS

Eighty-seven patients were included: cefepime, n = 61; other susceptible therapies, n = 26. There were no differences in 30-day in-hospital mortality between cefepime and other susceptible therapies (19.6% vs. 19.2%, p value = 0.719). In addition, there were no differences between clinical cure rates (cefepime 65.6% vs. other therapies 72 %, p value = 0.47). In multivariate logistic regression, treatment with cefepime (odds ratio [OR], 0.57; 95% confidence interval [CI], 0.11-2.52) was not independently associated with 30-day in-hospital mortality.

CONCLUSION AND RELEVANCE

For the treatment of Car-R Ceph-S P. aeruginosa pneumonia, cefepime showed similar rates of 30-day in-hospital mortality and clinical outcomes when compared to other susceptible therapies. Cefepime may be utilized to conserve novel β-lactam and β-lactamase inhibitors.

Prevalence of Extended-Spectrum β-Lactamases (ESBLs) Producing Aeromonas spp. Isolated from Lamellidens marginalis (Lamark, 1819) of Sewage-Fed Wetland: A Phenotypic and Genotypic Approach

The global rise of zoonotic bacteria resistant to multiple antimicrobial classes and the growing occurrence of infections caused by Aeromonas spp. resistant to β-lactam antibiotics pose a severe threat to animal and human health. However, the contribution of natural environments, particularly aquatic ecosystems, as ideal settings for the development and spread of antimicrobial resistance (AMR) is a key concern. Investigating the phenotypic antibiotic resistance and detection of β-lactamase producing Aeromonas spp. in Lamellidens marginalis, which inhabit all freshwater ecosystems of the Indian subcontinent, is essential for implications in monitoring food safety and drug resistance. In the present investigation, 92 isolates of Aeromonas spp. were recovered from 105 bivalves and screened for their antimicrobial resistance patterns. In vitro antibiotic resistance profiling showed a higher Multiple Antibiotic Resistance (MAR) index of 0.8 with the highest resistance against ampicillin/sulbactam (82%), while 58, 44, 39 and 38% of the isolates were resistant to cephalothin, erythromycin, cefoxitin and imipenem, respectively. PCR results revealed that these isolates carried the blaTEM gene (94%), which was followed by the blaCTX-M gene (51%) and the blaSHV gene (45%). A combination of blaSHV, blaCTX-M, and blaTEM genes was found in 17% of the isolates, indicating the presence of all three resistance genes. This is the first investigation which highlights the importance of multidrug-resistant Aeromonas spp. in L. marginalis. The identification of extended-spectrum-β-lactamases (ESBLs) genes demand the necessity of continuous surveillance and systematic monitoring, considering its potential health risks for both animals and human beings.

Clinically Isolated β-Lactam-Resistant Gram-Negative Bacilli in a Philippine Tertiary Care Hospital Harbor Multi-Class β-Lactamase Genes

In the Philippines, data are scarce on the co-occurrence of multiple β-lactamases (BLs) in clinically isolated Gram-negative bacilli. To investigate this phenomenon, we characterized BLs from various β-lactam-resistant Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa isolated from a Philippine tertiary care hospital. The selected Gram-negative bacilli (n = 29) were resistant to either third-generation cephalosporins (resistance category 1 (RC1)), cephalosporins and penicillin-β-lactamase inhibitors (RC2), or carbapenems (RC3). Isolates resistant to other classes of antibiotics but susceptible to early-generation β-lactams were also selected (RC4). All isolates underwent antibiotic susceptibility testing, disk-diffusion-based BL detection assays, and PCR with sequence analysis of extended-spectrum BLs (ESBLs), metallo-BLs, AmpC BLs, and oxacillinases. Among the study isolates, 26/29 harbored multi-class BLs. All RC1 isolates produced ESBLs, with blaCTX-M as the dominant (19/29) gene. RC2 isolates produced ESBLs, four of which harbored blaTEM plus blaOXA-1 or other ESBL genes. RC3 isolates carried blaNDM and blaIMP, particularly in three of the metallo-BL producers. RC4 Enterobacteriaceae carried blaCTX-M, blaTEM, and blaOXA-24-like, while A. baumannii and P. aeruginosa in this category carried either blaIMP or blaOXA-24. Genotypic profiling, in complement with phenotypic characterization, revealed multi-class BLs and cryptic metallo-BLs among β-lactam-resistant Gram-negative bacilli.

Risk factors and outcomes of inpatients with carbapenem-resistant Pseudomonas aeruginosa bloodstream infections in China: a 9-year trend and multicenter cohort study

Objective

Bacteremia caused by carbapenem-resistant Pseudomonas aeruginosa (CRPA) has high mortality, threatening the healthcare quality worldwide. Analysis is required to update the epidemiological data of CRPA bloodstream infections (BSI) and evaluate the prevalent strains in China. Moreover, it is necessary to clarify the risk factors associated with the development and mortality of CRPA bacteremia.

Methods

This is a 9-year multicenter retrospective study, enrolling 137 patients with CRPA BSI and 137 carbapenem-susceptible P. aeruginosa (CSPA) BSI during January 2012 and December 2020. Antimicrobials susceptibility between the two groups were compared. Risk factors of CRPA BSI were identified by binary logistic regression for development and cox regression for mortality. The Kaplan-Meier method was used to compare time to mortality. CRPA and difficult-to-treat resistant P. aeruginosa (DTRPA) detection rate was analyzed year-by-year in ZYH.

Results

A total of 7,384 P. aeruginosa clinical samples were cultured in ZYH during 9  years, and notable increase of CRPA and DTRPA detection rate in P. aeruginosa BSI was identified (from 17 to 60%; from 2.1 to 25%). Multivariate analysis revealed that prior ICU hospitalization, immunosuppressive therapy and exposure to carbapenems were independent risk factors for development of CRPA BSI. The 30-day crude mortality of 137 CRPA BSI was 39%. A total of 46 DTRPA were identified, and the 30-day mortality for patients infected by DTRPA was 50%. The 30-day crude mortality of CRPA BSI was independently associated with multiple organ failure and higher Pitt bacteremia score, whereas receipt appropriate therapy improved prognosis.

Conclusion

A significant increase in the detection rate of CRPA and DTRPA in P. aeruginosa BSI was identified. Strict policies for carbapenems usage, cautious decisions regarding the usage of immunosuppressive agent and standard care for patients with prior ICU hospitalization are necessary for CRPA BSI management.

Criteria Restricting Inappropriate Meropenem Empiricism (CRIME): a quasi-experimental carbapenem restriction pilot at a large academic medical centre

The broad-spectrum activity of carbapenems makes them appealing for empirical use; however, they are associated with development of Clostridioides difficile infection (CDI) and multidrug resistance. Selective carbapenem use is vital in maintaining their effectiveness. We examined the impact of meropenem restriction criteria on utilisation and patient outcomes. This quasi-experimental study was conducted at a single academic medical centre after medication use evaluation found frequent inappropriate meropenem utilisation. Antimicrobial stewardship-led restriction criteria were developed and implemented in February 2022. Investigators aimed to determine how restriction criteria affected meropenem utilisation across 8 weeks in the pre- (February-April 2020) versus post-implementation period (February-April 2022). The primary outcome was inappropriateness of meropenem utilisation. Secondary outcomes included days of therapy per 1000 patient-days (DOT/1000 PD), hospital length of stay (LOS), CDI Standardized Infection Ratio (SIR), and acquisition cost. Across the 8-week timeframes, reductions in inappropriate meropenem use (64.5% vs. 12.8%; P < 0.001), duration of therapy [5.8 (3.2-7.3) vs. 2.4 (1.0-5.5) days; P < 0.001] and utilisation (30.5 vs. 8.3 DOT/1000 PD; P < 0.001) pre- versus post-implementation were observed. Total meropenem orders decreased by 65% (P < 0.001). Median hospital LOS also decreased between periods [11.9 (7.8-20.4) vs. 9.2 (5.4-15.2) days], although not statistically significant (P = 0.051). There was no difference in CDI SIR (0.1 vs. 0.1; P = 0.99). Projected annual cost savings were ∼US$57 300. Implementation of antimicrobial stewardship-initiated restriction criteria can reduce inappropriate meropenem utilisation, overall number of orders, and total duration of therapy.

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.

Infectious Diseases Society of America 2022 Guidance on the Treatment of Extended-Spectrum β-lactamase Producing Enterobacterales (ESBL-E), Carbapenem-Resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with Difficult-to-Treat Resistance (DTR-P. aeruginosa)

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. The initial guidance document on infections caused by extended-spectrum β-lactamase producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa) was published on 17 September 2020. Over the past year, there have been a number of important publications furthering our understanding of the management of ESBL-E, CRE, and DTR-P. aeruginosa infections, prompting a rereview of the literature and this updated guidance document.

METHODS

A panel of 6 infectious diseases specialists with expertise in managing antimicrobial-resistant infections reviewed, updated, and expanded previously developed questions and recommendations about the treatment of ESBL-E, CRE, and DTR-P. aeruginosa infections. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment recommendations are provided with accompanying rationales, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Recommendations apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of 24 October 2021. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance/.

Geographic Patterns of Carbapenem-resistant Pseudomonas aeruginosa in the Asia-Pacific Region: Results from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program, 2015-2019

Pseudomonas aeruginosa is a common pathogen that is associated with multidrug-resistant (MDR) and carbapenem-resistant (CR) phenotypes; therefore, we investigated its resistance patterns and mechanisms by using data from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program in the Asia-Pacific region during 2015-2019. MICs were determined using the broth microdilution method. Genes encoding major extended-spectrum β-lactamases and carbapenemases were investigated by multiplex PCR assays. Susceptibility was interpreted using the Clinical and Laboratory Standards Institute (CLSI) breakpoints. A total of 6,349 P. aeruginosa isolates were collected in the ATLAS program between 2015 and 2019 from 14 countries. According to the CLSI definitions, the numbers (and rates) of CR and MDR P. aeruginosa were 1,198 (18.9%) and 1,303 (20.5%), respectively. For 747 of the CR P. aeruginosa strains that were available for gene screening, 253 β-lactamases genes were detected in 245 (32.8%) isolates. The most common gene was bla_VIM (29.0, 71/245), followed by bla_NDM (24.9%, 61/245) and bla_VEB (20.8%, 51/245). The resistance patterns and associated genes varied significantly between the countries in the Asia-Pacific region. India had the highest rates of carbapenem resistance (29.3%, 154/525) and gene detection (17.7%, 93/525). Compared to those harboring either class A or B β-lactamase genes, the CR P. aeruginosa without detected β-lactamase genes had lower MICs for most of the antimicrobial agents, including ceftazidime/avibactam and ceftolozane/tazobactam. In conclusion, MDR and CR P. aeruginosa infections pose a major threat, particularly those with detected carbapenemase genes. Continuous surveillance is important for improving antimicrobial stewardship and antibiotic prescriptions.

Carbapenem-resistant Pseudomonas aeruginosa strains: a worrying health problem in intensive care units

Pseudomonas aeruginosa is one of the most common bacterium with a broad spectrum of human-associated infections. It is intrinsically resistant to many antimicrobial drugs, making carbapenems crucial in clinical management. The emergence and dissemination of carbapenemases among P. aeruginosa clinical isolates is a serious public health concern as it limits the options for the treatment of bacterial infections. Here, we described the molecular and epidemiological characteristics of 28 carbapenem-resistant P. aeruginosa strains isolated from patients hospitalized in an intensive care unit (ICU). The antimicrobial susceptibility of carbapenem-resistant P. aeruginosa strains was determined by broth microdilution. The presence of resistance genes was evaluated by PCR and DNA sequencing. Additionally, alterations in genes encoding P. aeruginosa outer membrane proteins were analyzed by PCR as well as SDS-PAGE. Clinical characteristics of the patients and the economic impact of hospitalization on the public health system were evaluated. PCR amplification showed that the blaKPC-2 and blaTEM genes were identified in three isolates (11%) and blaSHV gene in two isolates (7%). Outer membrane profiles obtained by SDS-PAGE indicated that the OprD porin was either absent or was produced at very low levels. A PCR assay using oprD-specific primers failed to show the presence of mutations in this gene. P. aeruginosa strains were isolated from 28 patients, among whom 43% (12/28) had sepsis, 31% (9/28) had respiratory failure, and 31% (9/28) had systemic arterial hypertension. A high mortality rate (39%) was observed in these patients, with an average duration of hospitalization of 34.6 days and a median cost of 3.275 dollars per patient. The production of carbapenemase was not the main mechanism of resistance in these strains. All carbapenem-resistant P. aeruginosa were isolated from patients hospitalized in the ICU. Besides the high mortality rate, many patients remained hospitalized for several days, resulting in a high cost of hospitalization for the public health system. Therefore, the evolution of this resistance and its dissemination should be actively monitored among critically ill patients to improve their health conditions.

Genomic analysis of carbapenem-resistant Pseudomonas aeruginosa ST143 clone showing susceptibility to broad-spectrum cephalosporins

OBJECTIVES

Using whole-genome sequencing (WGS), we aimed to characterise a Pseudomonas aeruginosa ST143 clinical strain (Pb9) that presented resistance to meropenem and imipenem and susceptibility to piperacillin/tazobactam and broad-spectrum cephalosporins.

METHODS

The antimicrobial susceptibility profile was confirmed by broth microdilution. WGS was performed using an Illumina MiSeq platform to identify possible genetic determinants of β-lactam resistance. Transcription levels of chromosomally encoded efflux systems and oprD were evaluated by RT-qPCR.

RESULTS

WGS analysis showed that no acquired carbapenemase-encoding gene was found in isolate Pb9, although mutations in the chromosomally encoded β-lactamase genes bla_OXA-488, bla_PIB-1 and bla_PDC-5 were observed. In addition, we detected a premature stop codon in the major porin-encoding gene oprD coupled with hyperexpression of MexAB-OprM and MexEF-OprN.

CONCLUSION

Our results suggest that the β-lactam resistance phenotype presented by strain Pb9 might be related to an association of OprD loss with hyperexpression of the efflux pump systems MexAB-OprM and MexEF-OprN. However, the contribution of OXA-488, PDC-5 and PIB-1 to this phenotype remains unclear and warrants further investigation.

Cross-Resistance and the Mechanisms of Cephalosporin-Resistant Bacteria in Urinary Tract Infections Isolated in Indonesia

Urinary tract infection (UTI) by antibiotic-resistant strains has become increasingly problematic, with trends that differ from country to country. This study examined cross-resistance and the mechanisms of cephalosporin resistance in UTI-causative bacteria isolated in Indonesia. Antibiotic susceptibility tests based on Clinical Laboratory Standards Institute (CLSI) standards were done for UTI-causative strains (n = 50) isolated from patients in Indonesia in 2015-2016 and showed resistance against the third-generation cephalosporin. Mechanistic studies were carried out to confirm the presence of extended-spectrum β-lactamase (ESBL) genes, carbapenemase-related genes, the fosA3 gene related to fosfomycin resistance, and mutations of quinolone-resistance-related genes. Isolated UTI-causative bacteria included Escherichia coli (64.0%), Pseudomonas aeruginosa (16.0%), Klebsiella pneumoniae (10.0%), and others (10.0%). These strains showed 96.0% susceptibility to amikacin, 76.0% to fosfomycin, 90.0% to imipenem, 28.0% to levofloxacin, 92.0% to meropenem, and 74.0% to tazobactam/piperacillin. ESBL was produced by 68.0% of these strains. Mechanistic studies found no strains with carbapenemase genes but 6.0% of strains had the fosA3 gene. Seventy-two % of the strains had mutations in the gyrA gene and 74.0% in the parC gene. Most E. coli strains (87.5%) had Ser-83 → Leu and Asp-87 → Asn in gyrA and 93.8% of E. coli had Ser-80 → Ile in parC. There were significant correlations among mutations in gyrA and parC, and fosA3 gene detection (P < 0.05), respectively. To our knowledge, this is the first mechanistic study of antibiotic-cross-resistant UTI-causative bacteria in Indonesia. Further studies with a longer period of observation are necessary, especially for changes in carbapenem resistance without carbapenemase-related genes.

Cefoperazone/sulbactam: New composites against multiresistant gram negative bacteria?

Sulbactam, a class A β-lactamase inhibitor, added to cefoperazone either at a fixed 8 mg/L level of sulbactam or at a level of fixed cefoperazone: sulbactam ratio (2:1) would constitute a combination form of cefoperazone/sulbactam, which has better activities against Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii than cefoperazone alone. Cefoperazone/sulbactam (1:1 or 1:2) has greater in-vitro activity against most multidrug-resistant organisms (ESBL- and AmpC-producing Enterobacteriaceae and carbapenem-resistant A. baumannii except for carbapenem-resistant P. aeruginosa) than a 2:1 ratio. However, increased sulbactam concentration may induce AmpC production. Besides, sulbactam concentration might not be readily achievable in serum if the susceptibility rates were defined by the breakpoints of higher sulbactam composites, such as ≤16/16 (1:1) or 16/32 (1:2) mg/L. Carbapenemases (KPC-, OXA-type enzymes and metallo-β-lactamases) can't be inhibited by sulbactam. Some in-vitro studies showed that increasing sulbactam composites of cefoperazone/sulbactam had no effect on carbapenem-resistant P. aeruginosa, suggesting the presence of carbapenemases or AmpC overproduction that could not be overcome by increasing sulbactam levels to recover cefoperazone activity. Sulbactam alone has good intrinsic activity against carbapenem-resistant Acinetobacter strains sometimes even in the presence of carbapenemase genes, suggesting unsteady levels of carbapenemases. In conclusion, appropriate composites of cefoperazone and β-lactamase inhibitor sulbactam may expand the clinical use if the pharmacokinetic optimization could be achieved in the human serum.

It's Not Easy Being Green: A Narrative Review on the Microbiology, Virulence and Therapeutic Prospects of Multidrug-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is the most frequent cause of infection among non-fermenting Gram-negative bacteria, predominantly affecting immunocompromised patients, but its pathogenic role should not be disregarded in immunocompetent patients. These pathogens present a concerning therapeutic challenge to clinicians, both in community and in hospital settings, due to their increasing prevalence of resistance, and this may lead to prolonged therapy, sequelae, and excess mortality in the affected patient population. The resistance mechanisms of P. aeruginosa may be classified into intrinsic and acquired resistance mechanisms. These mechanisms lead to occurrence of resistant strains against important antibiotics-relevant in the treatment of P. aeruginosa infections-such as β-lactams, quinolones, aminoglycosides, and colistin. The occurrence of a specific resistotype of P. aeruginosa, namely the emergence of carbapenem-resistant but cephalosporin-susceptible (Car-R/Ceph-S) strains, has received substantial attention from clinical microbiologists and infection control specialists; nevertheless, the available literature on this topic is still scarce. The aim of this present review paper is to provide a concise summary on the adaptability, virulence, and antibiotic resistance of P. aeruginosa to a readership of basic scientists and clinicians.

Epidemiology and risk factors of rectal colonization of carbapenemase-producing Enterobacteriaceae among high-risk patients from ICU and HSCT wards in a university hospital

Background

Nosocomial carbapenemase-producing Enterobacterieceae (CPE) infections constitute a major global health concern and are associated with increased morbidity and mortality. Rectal colonization with CPE is a risk factor for bacterial translocation leading to subsequent endogenous CPE infections. This prospective observational study was aimed to investigate the prevalence and epidemiology of rectal colonization of CPE, the carbapenemase genotypes, and to identify the independent risk factors for the acquisition of CPE colonization in high-risk patients from ICU and HSCT wards in a university hospital in China.

Methods

In a prospective cohort study, 150 fecal samples from rectal swabs were consecutively obtained for inpatients from the intensive care unit (ICU) and hematopoietic stem cell transplantation (HSCT) wards from November 2018 to May 2019, and screening test for CPE was conducted by using prepared in-house trypsin soybean broth (TSB) selective media and MacConkey agar. Antimicrobial susceptibility was determined by the broth microdilution method and carbapenemase genes were characterized by both the GeneXpert Carba-R and PCR for bla_KPC, bla_NDM, bla_IMP, bla_VIM and bla_OXA. Multi-locus sequence typing (MLST) was employed to characterize the genetic relationships among the carbapenemase-producing K. Pneumonia (CPKP) isolates. In order to further investigate the risk factors and clinical outcomes of CPE colonization, a prospective case-control study was also performed.

Results

Twenty-six suspected CPE strains, including 17 Klebsiella pneumoniae, 6 Escherichia coli, 1 Citrobacter freundii, 1 Enterobacter Kobe, and 1 Raoultella ornithinolytica, were identified in 25 non-duplicated rectal swab samples from 25 patients, with a carriage rate of 16.67% (25/150). Through GeneXpert Carba-R and subsequent PCR and sequencing, all the suspected CPE isolates were identified to be positive for the carbapenemase genes, of which 17 were bla_KPC-carriers, and another 9 were bla_NDM-producers. MLST designated all the CPKP isolates to be ST11 clone. Multivariate analysis indicated that urinary system diseases, operation of bronchoscopy, and combined use of antibiotics were independent risk factors for acquiring CPE colonization in high-risk patients from the ICU and HSCT wards.

Conclusions

This study revealed a high prevalence of rectal CPE colonization in high-risk patients from ICU and HSCT wards, and a predominant colonization of the KPC-producing K. pneumoniae clone ST11. Stricter infection control measures are urgently needed to limit the dissemination of CPE strains, especially in patients who were afflicted by urinary system diseases, have underwent bronchoscopy, and were previously exposed to combined antibiotic use.

Polymyxin B resistance rates in carbapenem-resistant Pseudomonas aeruginosa isolates and a comparison between Etest® and broth microdilution methods of antimicrobial susceptibility testing

Polymyxin B has been considered to be the last line of defense for life-threatening infections caused by multiple drug resistant gram-negative pathogens, including carbapenem-resistant Pseudomonas aeruginosa (CRPA). The present study analyzed CRPA resistance to polymyxin B in the Suzhou district of China. Additionally, polymyxin B resistance rates were compared in different parts of the world to determine global trends. The present study also assessed the reliability and effectiveness of the Etest^® in a clinical setting, as laboratories lack a reliable and efficient susceptibility test for polymyxin B. The susceptibility rate of polymyxin B reached 96.0%, which is in accordance with results obtained from the United States of America, Europe, Africa and the majority of Asian countries. However, the rate of polymyxin B non-susceptibility (resistant or intermediate) in Singapore is 0.53 (95% confidence interval, 0.12-0.93). In addition, the susceptibility rate of polymyxin B determined via Etest^® was not significantly increased compared with that determined via broth microdilution (98.0 vs. 96.0%; P=0.558). Essential and categorical agreement rates reached 98.0%. In conclusion, the polymyxin B resistance rate of CRPA isolates is relatively low in the majority of countries, with the exception of Singapore. Furthermore, Etest^® may be a reliable clinical method for the measurement of polymyxin B resistance in CRPA isolates.

Aeromonas spp. Isolated from Pacific Abalone (Haliotis discus hannai) Marketed in Korea: Antimicrobial and Heavy-Metal Resistance Properties

Antimicrobial and heavy-metal resistance of 29 Aeromonas spp. (Aeromonas hydrophila n = 9, Aeromonas enteropelogenes n = 14, Aeromonas veronii n = 3, Aeromonas salmonicida n = 2, and Aeromonas sobria n = 1) isolated from Pacific abalone marketed in Korea were analyzed. All isolates were found to be resistant against ampicillin. High level of resistant to cephalothin (86%), rifampicin (73%), imipenem (42%), and oxytetracycline (35%) were also detected. Thirteen (45%) of the isolates showed multiple antimicrobial resistance (MAR) index ≥ 0.2. The PCR assays implied the presence of qnrS, qnrB, qnrA, tetB, tetA, aac (3')- IIa, aac(6')-Ib, aphAI-IAB, bla_CTX, bla_TEM, and intI1 genes among 76%, 28%, 14%, 17%, 3%, 3%, 41%, 10%, 41%, 28%, and 66% of the isolates, respectively. Class 1 integron gene cassette profiles aadA1(3%) and aadA2 (3%) were also identified. Lead (Pb) resistance was the highest (69%) among 5 heavy metals tested, whereas 38%, 27%, and 20% of the isolates were resistant to Cadmium (Cd), Chromium (Cr), and Copper (Cu), respectively. Heavy-metal resistance genes, CopA, CzcA, and merA were positive in 83%, 75%, and 41% of the isolates, respectively. In conclusion, observed genotypic and phenotypic resistance profiles of Aeromonas spp. against antimicrobials and heavy metals reveal the ability of serving as a source of antimicrobials and heavy-metal-resistant traits.

Detection of carbapenemase-producing Pseudomonas aeruginosa by phenotypic and genotypic methods in a tertiary care hospital of East India

BACKGROUND:

Carbapenemase-producing Pseudomonas aeruginosa is a serious threat in hospital infection due to its multidrug resistance.

AIM:

The aim of the study was to determine the frequency of carbapenem resistance in clinical isolates of Pseudomonas aeruginosa and detect the presence of carbapenemase enzymes in carbapenem-resistant P. aeruginosa (CRPA) isolates by phenotypic and genotypic methods.

MATERIAL AND METHODS:

Double-disk synergy test [DDST] and combined disk synergy test [CDST]) was performed in CRPA isolates and the prevalence of ^blaKPC, ^blaNDM-1, ^blaIMP, ^blaVIM, ^blaSIM, ^blaSPM, ^blaGIM, and ^blaOXA-48 was determined.

RESULTS:

Of 559 isolates included in the study, a total of 102 isolates were resistant to carbapenem that accounted for overall 18.24% (102/559) prevalence. Of these 102 isolates, 89 (87.25%) isolates were positive by DDST and 95 (93.17%) isolates were positive by CDST. Of 102 CRPA isolates, ^blaVIM was detected in 30 isolates (30/102, 29.1%), followed by ^blaNDM-1 in 29 (29/102, 28.4%) isolates and ^blaSIM and ^blaGIM in 6 isolates each (6/102, 5.8%). A combination of two carbapenemase genes was detected in 12 isolates, with six (6/102, 5.88%) CRPA isolates harboring with both ^blaVIM and ^blaNDM-1 genes. Four isolates were found to harbor a combination of three carbapenem-resistant genes.

CONCLUSION:

A high rate of carbapenemase production was observed in P. aeruginosa. Coproducers of multiple carbapenemases are also a cause of concern. An in-depth understanding of molecular mechanisms of resistance will be helpful in optimizing patient management and hospital infection control.

Carbapenem-Resistant but Cephalosporin-Susceptible Pseudomonas aeruginosa in Urinary Tract Infections: Opportunity for Colistin Sparing

This paper briefly reports the occurrence and epidemiology of carbapenem-resistant but cephalosporin-susceptible (Car-R/Ceph-S) Pseudomonas aeruginosa isolates from urinary tract infections (UTIs) in a tertiary-care hospital in the Southern Region of Hungary, and the phenotypic characterization of the possible resistance mechanisms in these isolates. Isolates and data were collected regarding P. aeruginosa UTIs corresponding to the period between 2008 and 2017. Susceptibility testing was performed using the Kirby–Bauer disk diffusion method; minimum inhibitory concentrations (MICs) of the isolates were determined using E-tests. The phenotypic detection of ampicillin C-type (AmpC) β-lactamases, efflux pump overexpression and carbapenemase production was also performed. P. aeruginosa represented n = 575 (2.72% ± 0.64%) from outpatient, and n = 1045 (5.43% ± 0.81%) from inpatient urinary samples, respectively. Based on the disk diffusion test, n = 359 (22.16%) were carbapenem-resistant; in addition to carbapenems, n = (64.34%) were also resistant to ciprofloxacin; n = (60.17%) to gentamicin/tobramycin; n = (58.51%) to levofloxacin; and n = (27.57%) to amikacin. From among the carbapenem-resistant isolates, n = 56 (15.59%) isolates were multidrug-resistant, while n = 16 (4.46%) were extensively drug-resistant. From among the Car-R/Ceph-S isolates (n = 57), overexpression of AmpC was observed in n = 7 cases (12.28%); carbapenemase production in n = 4 (7.02%); while overexpression of efflux pumps was present in n = 31 (54.39%) isolates. To spare last-resort agents, e.g., colistin, the use of broad-spectrum cephalosporins or safe, alternative agents should be considered in these infections.

Carbapenem-Resistant Klebsiella aerogenes Clinical Isolates from a Teaching Hospital in Southwestern China: Detailed Molecular Epidemiology, Resistance Determinants, Risk Factors and Clinical Outcomes

Purpose

Little is known about the epidemiology and carbapenem-resistance determinants of carbapenem-resistant K. aerogenes (CRKA) isolated from a single medical center. The present study was initiated to characterize the molecular epidemiology and the carbapenem-resistance mechanisms of CRKA isolated during 2012–2018 from a teaching hospital in southwest China, and to investigate the risk factors and clinical outcomes of CRKA infections as well.

Methods

Pulsed-field gel electrophoresis (PFGE) was employed for epidemiological analysis. PCR amplification and DNA sequencing were used to examine the antibiotic-resistance determinants. Plasmids were extracted and characterized by PCR-based replicon typing and conjugation assays. In order to further investigate the risk factors and clinical outcomes of CRKA infections, a retrospective case–control study was also performed.

Results

PFGE analysis showed 32 different PFGE patterns among the 36 non-duplicated CRKA strains collected. Most of the isolates harbored multi-drug resistance (MDR) genes, including 2 (5.6%) carrying bla_NDM-1, 1 (2.8%) harboring bla_KPC-2, 13 (36.1%) carrying ESBL genes, 23 (63.9%) carrying ampC genes, 34 (94.4%) carrying quinolone resistance determinants (QRD) genes and 9 (25%) carrying aminoglycoside resistance determinants (ARD) genes. The outer membrane porins, OmpE35 and OmpE36, were, respectively, lost in 4 and 2 isolates. The efflux pump inhibition experiments were positive in 25 (69.4%) of the CRKA strains. Multivariate analysis indicated that hypo-albuminaemia, invasive procedures, and carbapenem exposure were independent risk factors for acquiring CRKA infections.

Conclusion

No clonality relationship was identified among most of the 36 CRKA isolates. The over-expression of ESBLs and AmpC coupled with the efflux pumps contributed to carbapenem resistance in K. aerogenes. Additionally, this is the first report of CRKA isolate co-harboring bla_NDM-1, bla_CTX-M-15, bla_EBC, bla_ACC, acc (6ʹ)-Ib, armA, qnrD and loss of OmpE36 in China. Hypo-albuminaemia, invasive procedures and carbapenem exposure were associated with acquisition of CRKA infections.

Risk factors for polymyxin-resistant carbapenemase-producing Enterobacteriaceae in critically ill patients: An epidemiological and clinical study

This study aimed to assess the clinical impact and potential risk factors associated with polymyxin-resistant Enterobacteriaceae strains isolated from patients hospitalized in adult and neonatal intensive care units. A case-control study was conducted from September 2015 to January 2017. Antimicrobial susceptibility of polymyxin-resistant Enterobacteriaceae strains was determined by broth microdilution. The presence of resistance genes was evaluated by polymerase chain reaction and DNA sequencing. Renal failure [P=0.02, odds ratio (OR) 11.37, 95% confidence interval (CI) 1.0-128.63], use of a urinary catheter (P<0.01, OR 4.16, 95% CI 38.82-366.07), transfer between hospital units (P=0.03, OR 9.98, 95% CI 1.01-98.42), carbapenem use (P<0.01, OR 45.49, 95% CI 6.93-298.62) and surgical procedure (P<0.01, OR 16.52, 95% CI 2.83-96.32) were found to be risk factors for the acquisition of polymyxin-resistant strains in adult patients. For neonatal patients, use of a central venous catheter (P<0.01, OR 69.59, 95% CI 7.33-660.30) was the only risk factor associated with the acquisition of polymyxin-resistant strains. Analysis of the outcomes revealed that the mortality rate was significantly higher in adult (66.6%) and neonatal (23.5%) patients with polymyxin-resistant strains than in those with polymyxin-susceptible strains. In addition, carbapenem exposure (P<0.01, OR 50.93, 95% CI 2.26->999.999) was strongly associated with mortality. On the other hand, aminoglycoside use (P<0.03, OR 0.06, 95% CI 0.004-0.97) was a protective factor against mortality from polymyxin-resistant strains. Several risk factors were associated with polymyxin-resistant strains. The high mortality rates showed that acquisition of these strains is a predictor for unfavourable outcomes. Combination treatment with an aminoglycoside and polymyxin might be a better combination to improve patient outcomes.

Characterization of carbapenem-resistant but cephalosporin-susceptible Pseudomonas aeruginosa

In this study, mechanisms of carbapenem resistance in carbapenem-resistant but cephalosporin-susceptible (Car-R/Ceph-S) Pseudomonas aeruginosa were investigated. A total of 243 P. aeruginosa isolates were studied. The disk diffusion and agar dilution methods were used for determination of antibiotic susceptibility patterns. AmpC and efflux pump overproductions were detected by phenotypic methods. The presence of carbapenemase-encoding genes was detected by polymerase chain reaction (PCR). The expression of OprD, MexAB-OprM, and MexXY-OprM efflux pumps was assessed by real-time PCR. According to disk diffusion method, altogether 116 P. aeruginosa isolates (47.7%) were carbapenem-resistant and among them, 23 isolates (19.8%) were cephalosporin-susceptible. Carbapenemase producer was not detected. Overexpression of AmpC was detected in one (4.3%) isolate that was ceftazidime-susceptible but cefepime-resistant. Overexpression of MexAB-OprM and MexXY-OprM efflux pumps was detected in 12 (60.9%) and 16 (68.8%) of isolates, respectively. A total of 16 (68.8%) isolates showed decreased expression of OprD. The Car-R/Ceph-S P. aeruginosa did not develop by carbapenemase production. The resistance to carbapenem was mediated in our clinical isolates by decreased expression of OprD and overexpression of MexAB-OprM and MexXY-OprM efflux systems or the combination of these mechanisms.