Abstract We investigated the antimicrobial resistance profile and the occurrence of Klebsiella pneumoniae carbapenemase (KPC)–producing Gram-negative rods in sewage samples obtained from a Brazilian ...teaching hospital and from the wastewater treatment plant (WWTP) that receives it for treatment. We identified multidrug-resistant bacteria as well as KPC-2–producing Aeromonas spp. and several Enterobacteriaceae species, including Kluyvera spp., in the hospital effluent and in different sites of the WWTP. Most isolates showed the blaKPC-2 gene harbored on a transposon that was carried by conjugative plasmids. The presence of KPC production among Aeromonas spp., Kluyvera spp., and other Enterobacteriaceae indicates the adaptability of such isolates to aquatic environments, not only in the hospital effluent but also throughout the WWTP. Although secondary treatment seems to decrease the amount of KPC producers in sewage, multidrug-resistant isolates are continually disposed in the urban river. Thus, sewage treatment regulations are urgently needed to decelerate the evolution of antimicrobial resistance beyond hospitals.
Highlights • Aminoglycoside combinations are treatment of choice for CRE infections if the strain is susceptible to aminoglycosides. • Treatment of MRSA infections has revived clinical use of ...TMP/SMX, available both as intravenous and oral formulations. • Minocycline is an antimicrobial of choice in treating CRAB infections, in particular when the maximum dose is administered. • Fosfomycin has resurged as an alternative therapeutic option for MDR infections, especially those caused by CRE. • Polymyxins combined with ≥1 in vitro-active agents are associated with reduced mortality in invasive CRE infections.
Abstract
Background
The SENTRY Antimicrobial Surveillance Program was established in 1997 and encompasses over 750 000 bacterial isolates from ≥400 medical centers worldwide. Among the pathogens ...tested, Pseudomonas aeruginosa remains a common cause of multidrug-resistant (MDR) bloodstream infections and pneumonia in hospitalized patients. In the present study, we reviewed geographic and temporal trends in resistant phenotypes of P. aeruginosa over 20 years of the SENTRY Program.
Methods
From 1997 to 2016, 52 022 clinically significant consecutive isolates were submitted from ≥200 medical centers representing the Asia-Pacific region, Europe, Latin America, and North America. Only 1 isolate per patient per infection episode was submitted. Isolates were identified by standard algorithms and/or matrix-assisted laser desorption ionization-time of flight mass spectrometry. Susceptibility testing was performed by Clinical and Laboratory Standards Institute (CLSI) methods and interpreted using CLSI and European Committee on Antimicrobial Susceptibility Testing 2018 criteria at JMI Laboratories.
Results
The most common infection from which P. aeruginosa was isolated was pneumonia in hospitalized patients (44.6%) followed by bloodstream infection (27.9%), with pneumonia having a slightly higher rate of MDR (27.7%) than bloodstream infections (23.7%). The region with the highest percentage of MDR phenotypes was Latin America (41.1%), followed by Europe (28.4%). The MDR rates were highest in 2005–2008 and have decreased in the most recent period. Colistin was the most active drug tested (99.4% susceptible), followed by amikacin (90.5% susceptible).
Conclusions
Over the 20 years of SENTRY Program surveillance, the rate of MDR P. aeruginosa infections has decreased, particularly in Latin America. Whether the trend of decreasing resistance in P. aeruginosa is maintained will be documented in future SENTRY Program and other surveillance reports.
•Silent spread of a major clone of BKC-1-producing Klebsiella pneumoniae ST442.•Acquisition of blaBKC-1 by a virulent clone, ST11-KL64.•High β-lactam minimum inhibitory concentrations were observed ...in isolates co-producing BKC-1 and KPC-2.•Clinical and demographic patient data of BKC-1 producers were described for the first time.
To describe the undetected circulation of an epidemic BKC-1-producing Klebsiella pneumoniae ST442 clone, occasioning the first reported outbreak of the infrequent carbapenemase BKC-1.
Six hundred and forty-seven K. pneumoniae isolates (2008–2017) with reduced susceptibility to carbapenems were screened for blaBKC-1. BKC-1-positive isolates were typed using pulsed-field gel electrophoresis and multi-locus sequence typing. Susceptibility profiles were determined by broth microdilution, and additional antimicrobial resistance genes (ARGs) were investigated by polymerase chain reaction. Some isolates were submitted to full genomic characterization by whole-genome sequencing (Illumina MiSeq and MinIon), and in-vivo virulence studies using the Galleria mellonella model.
Sixteen (2.5%) K. pneumoniae, from 15 patients, carrying blaBKC-1 were found between 2010 and 2012. Among these patients, the all-cause mortality rate was 54.5%. A major clone – A1-ST442 (13/16) – was isolated during the study period. The BKC-1-producing isolates had a multi-drug-resistant phenotype, remaining susceptible to gentamicin (87.5%) and ceftazidime-avibactam (100%) alone. The presence of two carbapenemases – blaBKC-1 and blaKPC-2 – was detected in six isolates, increasing the β-lactam minimum inhibitory concentration significantly. Additionally, other ARGs were identified on A1-ST442 and B1-ST11 clones. The B1-ST11 clone was more virulent than the A1-ST442 clone.
An undetected outbreak caused predominantly by a BKC-1-positive A1-ST442 clone between 2010 and 2012 was identified 10 years later in a Brazilian hospital. The misidentification of BKC-1 may have worsened the spread of resistant clones; this reinforces the need for correct and rapid identification of antimicrobial resistance mechanisms in hospitals.
The emergence and rapid dissemination of colistin-resistant
carrying the plasmid-mediated
gene have created an urgent need to develop specific screening methods. In this study, we evaluated four ...assays based on the inhibition of MCR-1 activity by EDTA: (i) a combined-disk test (CDT) comparing the inhibition zones of colistin and colistin (10 μg) plus EDTA (100 mM); (ii) reduction of colistin MIC (CMR) in the presence of EDTA (80 μg/ml); (iii) a modified rapid polymyxin Nordmann/Poirel test (MPNP); and (iv) alteration of zeta potential (R
= ZP
/ZP
). We obtained encouraging results for the detection of MCR-1 in
isolates recovered from human, food, and animal samples, using the following assay parameters: ≥3 mm difference in the inhibition zones between colistin disks without and with EDTA; ≥4-fold colistin MIC decrease in the presence of EDTA; R
of ≥2.5; and the absence of metabolic activity and proliferation, indicated by unchanged color of phenol red in the presence of colistin-EDTA, in the MPNP test. In this regard, the CDT, CMR, R
, and MPNP assays exhibited sensitivities of 96.7, 96.7, 95.1, and 96.7% and specificities of 89.6, 83.3, 100, and 100%, respectively, for detecting MCR-1-positive
Our results demonstrate that inhibition by EDTA and zeta potential assays may provide simple and inexpensive methods for the presumptive detection of MCR-1-producing
isolates in human and veterinary diagnostic laboratories.
Multi-drug efflux pumps have been increasingly recognized as a major component of resistance in P. aeruginosa. We have investigated the expression level of efflux systems among clinical isolates of ...P. aeruginosa, regardless of their antimicrobial susceptibility profile.
Aztreonam exhibited the highest in vitro activity against the P. aeruginosa isolates studied (64.4% susceptibility), whereas susceptibility rates of imipenem and meropenem were both 47.5%. The MexXY-OprM and MexAB-OprM efflux systems were overexpressed in 50.8% and 27.1% of isolates studied, respectively. Overexpression of the MexEF-OprN and MexCD-OprJ systems was not observed. AmpC beta-lactamase was overexpressed in 11.9% of P. aeruginosa isolates. In addition, decreased oprD expression was also observed in 69.5% of the whole collection, and in 87.1% of the imipenem non-susceptible P. aeruginosa clinical isolates. The MBL-encoding genes blaSPM-1 and blaIMP-1 were detected in 23.7% and 1.7% P. aeruginosa isolates, respectively. The blaGES-1 was detected in 5.1% of the isolates, while blaGES-5 and blaCTX-M-2 were observed in 1.7% of the isolates evaluated. In the present study, we have observed that efflux systems represent an adjuvant mechanism for antimicrobial resistance.
Efflux systems in association of distinct mechanisms such as the porin down-regulation, AmpC overproduction and secondary beta-lactamases play also an important role in the multi-drug resistance phenotype among P. aeruginosa clinical isolates.
Abstract
Objectives
Carbapenem-resistant Pseudomonas aeruginosa (CR-PSA) imposes great limitations on empirical therapeutic choices, which are further complicated by metallo-β-lactamase production. ...This study evaluated in vitro antimicrobial synergy of ceftolozane/tazobactam in combination with aztreonam and fosfomycin against MDR PSA.
Methods
MICs were determined by broth microdilution and gradient strips. The effect of ceftolozane/tazobactam+aztreonam and ceftolozane/tazobactam+fosfomycin combinations were tested against 27 MDR PSA isolates carrying blaSPM-1 (n = 13), blaIMP (n = 4), blaVIM (n = 3), blaGES-1 (n = 2) and blaCTX-M-like (n = 2), and 3 isolates with no acquired β-lactamase production detected by gradient diffusion strip crossing (GDSC). Six genetically unrelated SPM-1-producing isolates were also evaluated by time–kill analysis (TKA).
Results
All CR-PSA isolates harbouring blaSPM-1, blaGES-1 and blaIMP-1 were categorized as resistant to ceftolozane/tazobactam, meropenem and fosfomycin, with 70% being susceptible to aztreonam. Synergism for ceftolozane/tazobactam+fosfomycin and ceftolozane/tazobactam+aztreonam combinations was observed for 88.9% (24/27) and 18.5% (5/27) of the isolates by GDSC, respectively. A 3- to 9-fold reduction in ceftolozane/tazobactam MICs was observed, depending on the combination. Ceftolozane/tazobactam+fosfomycin was synergistic by TKA against one of six SPM-1-producing isolates, with additional non-synergistic bacterial density reduction for another isolate. Aztreonam peak concentrations alone demonstrated a ≥3 log10 cfu/mL reduction against all six isolates, but all strains were within the susceptible range for the drug. No antagonism was observed.
Conclusions
In the context of increasing CR-PSA and the genetic diversity of resistance mechanisms, new combinations and stewardship strategies may need to be explored in the face of increasingly difficult to treat pathogens.
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