Colonization by Extended-Spectrum β-Lactamase-Producing Enterobacterales and Bacteremia in Hematopoietic Stem Cell Transplant Recipients

BACKGROUND

Assessing the risk of multidrug-resistant colonization and infections is pivotal for optimizing empirical therapy in hematopoietic stem cell transplants (HSCTs). Limited data exist on extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E) colonization in this population. This study aimed to assess whether ESBL-E colonization constitutes a risk factor for ESBL-E bloodstream infection (BSI) and to evaluate ESBL-E colonization in HSCT recipients.

METHODS

A retrospective analysis of ESBL-E colonization and BSI in HSCT patients was conducted from August 2019 to June 2022. Weekly swabs were collected and cultured on chromogenic selective media, with PCR identifying the β-lactamase genes. Pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS) assessed the colonizing strains' similarities.

RESULTS

Of 222 evaluated HSCT patients, 59.45% were colonized by ESBL-E, with 48.4% at admission. The predominant β-lactamase genes were blaTEM (52%) and blaSHV (20%). PFGE analysis did not reveal predominant clusters in 26 E. coli and 15 K. pneumoniae strains. WGS identified ST16 and ST11 as the predominant sequence types among K. pneumoniae. Thirty-three patients developed thirty-five Enterobacterales-BSIs, with nine being third-generation cephalosporin-resistant. No association was found between ESBL-E colonization and ESBL-BSI (p = 0.087).

CONCLUSIONS

Although the patients presented a high colonization rate of ESBL-E upon admission, no association between colonization and infection were found. Thus, it seems that ESBL screening is not a useful strategy to assess risk factors and guide therapy for ESBL-BSI in HSCT-patients.

Multicenter Diagnostic Evaluation of OnSite COVID-19 Rapid Test (CTK Biotech) among Symptomatic Individuals in Brazil and the United Kingdom

The COVID-19 pandemic has given rise to numerous commercially available antigen rapid diagnostic tests (Ag-RDTs). To generate and to share accurate and independent data with the global community requires multisite prospective diagnostic evaluations of Ag-RDTs. This report describes the clinical evaluation of the OnSite COVID-19 rapid test (CTK Biotech, CA, USA) in Brazil and the United Kingdom. A total of 496 paired nasopharyngeal (NP) swabs were collected from symptomatic health care workers at Hospital das Clínicas in São Paulo, Brazil, and 211 NP swabs were collected from symptomatic participants at a COVID-19 drive-through testing site in Liverpool, United Kingdom. Swabs were analyzed by Ag-RDT, and results were compared to quantitative reverse transcriptase PCR (RT-qPCR). The clinical sensitivity of the OnSite COVID-19 rapid test in Brazil was 90.3% (95% confidence interval [CI], 75.1 to 96.7%) and in the United Kingdom was 75.3% (95% CI, 64.6 to 83.6%). The clinical specificity in Brazil was 99.4% (95% CI, 98.1 to 99.8%) and in the United Kingdom was 95.5% (95% CI, 90.6 to 97.9%). Concurrently, analytical evaluation of the Ag-RDT was assessed using direct culture supernatant of SARS-CoV-2 strains from wild-type (WT), Alpha, Delta, Gamma, and Omicron lineages. This study provides comparative performance of an Ag-RDT across two different settings, geographical areas, and populations. Overall, the OnSite Ag-RDT demonstrated a lower clinical sensitivity than claimed by the manufacturer. The sensitivity and specificity from the Brazil study fulfilled the performance criteria determined by the World Health Organization, but the performance obtained from the UK study failed to do. Further evaluation of Ag-RDTs should include harmonized protocols between laboratories to facilitate comparison between settings. IMPORTANCE Evaluating rapid diagnostic tests in diverse populations is essential to improving diagnostic responses as it gives an indication of the accuracy in real-world scenarios. In the case of rapid diagnostic testing within this pandemic, lateral flow tests that meet the minimum requirements for sensitivity and specificity can play a key role in increasing testing capacity, allowing timely clinical management of those infected, and protecting health care systems. This is particularly valuable in settings where access to the test gold standard is often restricted.

Chlorhexidine susceptibility and Eagle effect in planktonic cells and biofilm of nosocomial isolates

The aim of this study is to evaluate the chlorhexidine gluconate (CHG) susceptibility in both planktonic cells and biofilm of 32 Gram-negative (Gn) and 6 Gram-positive (Gp) isolates by minimal inhibitory concentration (2-256 μg/mL for Gn and 2-32 μg/mL for Gp), minimal bactericidal concentration (4-256 μg/mL for Gn and 2-32 μg/mL for Gp) in planktonic cells, and minimal biofilm elimination concentration (128 ≥ 16,384 μg/mL in Gn and 32 ≥ 16,384 μg/mL in Gp) in biofilm environment. Our study showed that Gn isolates have higher minimal concentrations than Gp and bacteria in biofilms are more tolerant than planktonic ones. No correlation between MBC or MBEC and biofilm formation was statistically confirmed. The Eagle effect, previously described for antimicrobials and antifungals, was evidenced in this work for CHG, an antiseptic. Besides that, the phenomenon was described in 23/38 isolates (60.5%), raising minimal concentration up to ≥ 16,384 μg/mL. Our study showed that clinical isolates have a high ability to form biofilm allowing them to tolerate CHG concentrations as high as the ones used in clinical practice. Therefore, attention should be given to the occurrence of this phenomenon to avoid false susceptibility results.

Neisseria gonorrhoeae arthritis in a patient with systemic lupus: resistance and virulence profiles

In this study, we describe a case report of gonococcal arthritis in a Systemic Lupus Erythematosus patient. Although several mechanisms favor disseminated gonococcal infection (DGI) in patients immunosuppressed by SLE, this association is rarely reported in literature. We performed whole genome sequencing (WGS) of the etiologic agent involved and molecular analysis using a global collection of Neisseria gonorrhoeae strains. Ours is the only sample derived from synovial fluid identified in this collection, the others being from the usual anatomical sites. Antimicrobial susceptibility was determined by disk diffusion and Etest, and WGS was conducted to determine multilocus sequence typing profiles, group isolates based on core genome single nucleotide polymorphisms (SNP), and identify virulence genes and antimicrobial resistance determinants. The N. gonorrhoeae samples in the global collection were highly heterogeneous. The SNP tree had a total 19,532 SNPs in 320 samples. Our sample displayed resistance to ciprofloxacin (MIC = 2 μg/mL) and tetracycline (zone diameter = 0 mm) belonged to ST 1588 and was not closely related to any isolate in the global collection of N. gonorrhoeae strains. The isolate had genetic features related to beta-lactam, tetracycline and quinolone resistance. Seventy-one virulence genes were identified in our sample, belonging to the following classes: adherence, efflux pump, immune modulator, invasion, iron uptake, protease and stress adaptation. Moreover, no virulence genes for immune evasion and toxin were identified.

Virulomic Analysis of Multidrug-Resistant Klebsiella pneumoniae Isolates and Experimental Virulence Model Using Danio rerio (Zebrafish)

This study evaluates a possible correlation between multidrug-resistant Klebsiella pneumoniae strains and virulence markers in a Danio rerio (zebrafish) model. Whole-genome sequencing (WGS) was performed on 46 strains from three Brazilian hospitals. All of the isolates were colistin-resistant and harbored bla_KPC-2. Ten different sequence types (STs) were found; 63% belonged to CC258, 22% to ST340, and 11% to ST16. The virulence factors most frequently found were type 3 fimbriae, siderophores, capsule regulators, and RND efflux-pumps. Six strains were selected for a time-kill experiment in zebrafish embryos: infection by ST16 was associated with a significantly higher mortality rate when compared to non-ST16 strains (52% vs. 29%, p = 0.002). Among the STs, the distribution of virulence factors did not differ significantly except for ST23, which harbored a greater variety of factors than other STs but was not related to a higher mortality rate in zebrafish. Although several virulence factors are described in K. pneumoniae, our study found ST16 to be the only significant predictor of a virulent phenotype in an animal model. Further research is needed to fully understand the correlation between virulence and sequence types.

MRSA outbreak in a Neonatal Intensive Care Unit in a developed country: importance of rapid detection of reservoirs and implementation of intervention measures

We described a MRSA bloodstream infection outbreak that was rapidly identified and controlled in a Neonatal Intensive Care Unit after implementation of a bundle of measures, including PCR-screening and HCW decolonization. We found 35% of healthcare workers(HCW) colonized with S. aureus by PCR, one of them that presented skin lesion positive for MSSA (same clone and spa type than two patients). Our findings raise the hypothesis that the outbreak could be related to HCW colonization.

Conjugative transfer of plasmid p_8N_qac(MN687830.1) carrying qacA gene from Staphylococcus aureus to Escherichia coli C600: potential mechanism for spreading chlorhexidine resistance

The methicillin resistant Staphylococcus aureus (MRSA) is recognized by its ability to acquire and transferring resistance genes through interspecies conjugative plasmids. However, transference of plasmids from Gram-positive cocci to Gram-negative bacilli is not well characterized. In this report, we describe the transfer of a conjugative plasmid carrying qacA from MRSA to Escherichia coli C600. We performed a conjugation experiment using a chlorhexidine resistant MRSA isolate (ST-105/SCCmec type III) carrying the gene qacA and qacC as the donor and a chlorhexidine susceptible E. coli C600 isolate as the receptor. Transconjugants were selected using MacConkey agar plates containing chlorhexidine in concentrations ranging from 0.25 to 16 g.L^-1. To genotypically confirm the transfer of the resistance gene, the transconjugants were screened by Polymerase Chain Reaction (PCR) and submitted to Sanger’s sequencing. MRSA isolates successfully transferred the chlorhexidine resistance gene (qacA) to the recipient E. coli strain C600. The E. coli transconjugant exhibited an important reduction of chlorhexidine susceptibility, with MICs increasing from ≤ 0.25 to ≥ 16 g.L^-1 after conjugation. The qacA gene was detected by PCR as well as in the Sanger’s sequencing analysis of DNA from transconjugant plasmids. To the best of our knowledge, this is the first report of the plasmid p_8N_qac(MN687830.1) carrying qacA and its transfer by conjugation from a MRSA to an E. coli. These findings increase concerns on the emergence of resistance dissemination across the genus and emphasizes the importance of continuous antiseptic stewardship.

Genetic description of VanD phenotype vanA genotype in vancomycin-resistant Enterococcus faecium isolates from a Bone Marrow Transplantation Unit

BACKGROUND

Vancomycin-resistant Enterococcus faecium (VREfm) is an important agent of hospital-acquired infection. VanA phenotype is characterized by resistance to high levels of vancomycin and teicoplanin and is encoded by the vanA gene, whereas VanD phenotype is characterized by resistance to vancomycin and susceptibility or intermediate resistance to teicoplanin; however, some isolates carry a VanD phenotype with a vanA genotype, but there are many gaps in the knowledge about the genetic mechanisms behind this pattern.

OBJECTIVE

To characterize the genetic structure, clonality, and mobile genetic elements of VRE isolates that display a VanD-vanA phenotype.

RESULTS

All vanA VRE-fm isolates displayed minimum inhibitory concentration (MIC) for vancomycin > 32µg/mL and intermediate or susceptible MIC range for teicoplanin (8-16µg/mL). The isolates were not clonal, and whole-genome sequencing analysis showed that they belonged to five different STs (ST478, ST412, ST792, ST896, and ST1393). The absence of some van complex genes were observed in three isolates: Ef5 lacked vanY and vanZ, Ef2 lacked vanY, and Ef9 lacked orf1 and orf2; moreover, another three isolates had inverted positions of orf1, orf2, vanR, and vanS genes. IS1542 was observed in all isolates, whereas IS1216 in only five. Moreover, presence of other hypothetical protein-encoding genes located downstream the vanZ gene were observed in six isolates.

CONCLUSION

VRE isolates can display some phenotypes associated to vanA genotype, including VanA and VanB, as well as VanD; however, further studies are needed to understand the exact role of genetic variability, rearrangement of the transposon Tn1546, and presence of insertion elements in isolates with this profile.

Phenotypic and genotypic characteristics of a Carbapenem-resistant Serratia marcescens cohort and outbreak: describing an opportunistic pathogen

Serratia marcescens is an emerging opportunistic pathogen with high genetic diversity. We described microbiological characteristics of isolates and also risk factors for infections caused by carbapenem-resistant S. marcescens(CrSm). A retrospective study of patients colonized(N=43) and infected(N=20) by CrSm over a three-year period was conducted. Polymerase chain reaction(PCR) for carbapenemases genes and molecular typing of all available strains was performed; Forty-two isolates were analyzed, including three environmental samples identified during an outbreak. Thirty-five CrSm carried bla_KPC-2; one isolate was bla_NDM-positive and four isolates carried bla_OXA-101. The genomes were grouped into three clusters with 100% bootstrap; three patterns of mutations on ompC and ompF were found. The strains carried virulence genes related to invasion and hemolysis and the environmental strains presented less mutations on the virulence genes than clinical strains. The multivariate analysis showed that previous use of polymyxin(p=0.008) was an independent risk factor for infection by CrSm. Our study highlighted that bla_KPC-2 in association with ompC, ompF mutation was the most frequent mechanism of resistance in our hospital, and that previous use of polymyxin was an independent risk factor for CrSm. There is a predominant clone, including the environmental isolates, suggesting that cross-transmission was involved in the dissemination of this pathogen.

Carbapenem-resistant Klebsiella pneumoniae colonization and infection is associated with lower overall survival in a cohort of haematopoietic stem-cell transplantation patients: mechanism of resistance and virulence by whole-genome sequencing

Carbapenem-resistant Klebsiella pneumoniae (CRK) infections are a growing concern in immunocompromised patients. The aim of the present study was to evaluate the impact of CRK colonization and infection in overall mortality for haematopoietic stem-cell transplant (HSCT) patients. We also aimed to investigate resistance and virulence profiles of CRK isolates and assess their epidemiological and genetic relatedness. Patients in the HSCT unit were screened for colonization with CRK with weekly rectal swab or stool cultures and placed under contact precautions. We defined CRK colonization as positive culture from a swab or stool sample grown in MacConkey agar with meropenem at 1 µg ml^-1. Demographic and clinical data were retrieved from the patients' charts and electronic records. According to resistance mechanisms and pulsed field gel electrophoresis profile, isolates were selected based on whole-genome sequencing (WGS) using MiSeq Illumina. Outcomes were defined as overall mortality (death up to D+100), and infection-related death (within 14 days of infection). We report a retrospective cohort of 569 haematopoietic stem-cell transplant patients with 105 (18.4 %) CRK colonizations and 30 (5.3 %) infections. blaKPC was the most frequent carbapenemase in our cohort with three isolates co-harbouring blaKPC and blaNDM. We found no difference in virulence profiles from the CRK isolates. There were also no significant differences in virulence profiles among colonization and infection isolates regarding genes encoding for type 1 and 3 fimbriae, siderophores, lipopolysaccharide and colibactin. In clonality analysis by PFGE and WGS, isolates were polyclonal and ST340 was the most prevalent. Overall survival at D+100 was 75.4 % in in CRK-colonized (P=0.02) and 35.7 % in infected patients and significantly lower than non-colonized patients (85.8 %; P<0.001). We found a higher overall mortality associated with colonization and infection; KPC was the main resistance mechanism for carbapenems. The polyclonal distribution of isolates and findings of CRK infection in patients not previously colonized suggest the need to reinforce antibiotic stewardship.

Bloodstream Infections caused by Klebsiella pneumoniae and Serratia marcescens isolates co-harboring NDM-1 and KPC-2

Carbapenem-resistant Enterobacteriaceae are a worldwide health problem and isolates carrying both bla_KPC-2 and bla_NDM-1 are unusual. Here we describe the microbiological and clinical characteristics of five cases of bloodstream infections (BSI) caused by carbapenem-resistant Klebsiella pneumoniae and Serratia marcescens having both bla_KPC-2 and bla_NDM-1. Of the five blood samples, three are from hematopoietic stem cell transplantation patients, one from a renal transplant patient, and one from a surgical patient. All patients lived in low-income neighbourhoods and had no travel history. Despite antibiotic treatment, four out of five patients died. The phenotypic susceptibility assays showed that meropenem with the addition of either EDTA, phenylboronic acid (PBA), or both, increased the zone of inhibition in comparison to meropenem alone. Molecular tests showed the presence of bla_KPC-2 and bla_NDM-1 genes. K. pneumoniae isolates were assigned to ST258 or ST340 by whole genome sequencing. This case-series showed a high mortality among patients with BSI caused by Enterobacteriae harbouring both carbapenemases. The detection of carbapenemase-producing isolates carrying both bla_KPC-2 and bla_NDM-1 remains a challenge when using only phenotypic assays. Microbiology laboratories must be alert for K. pneumoniae isolates producing both KPC-2 and NDM-1.

Colistin-resistant Escherichia coli belonging to different sequence types: genetic characterization of isolates responsible for colonization, community- and healthcare-acquired infections

The plasmid-mediated colistin-resistance gene named mcr-1 has been recently described in different countries and it became a public health challenge. Of note, few studies have addressed the spread of Escherichia coli harboring the mcr-1 gene in both, community and hospital settings. A total of seven colistin-resistant E. coli carrying mcr-1, collected from 2016 to 2018, from community (n=4), healthcare-acquired infections (n=2) and colonization (n=1) were identified in three high complexity hospitals in Sao Paulo, Brazil. These colistin-resistant isolates were screened for mcr genes by PCR and all strains were submitted to Whole Genome Sequencing and the conjugation experiment. The seven strains belonged to seven distinct sequence types (ST744, ST131, ST69, ST48, ST354, ST57, ST10), and they differ regarding the resistance profiles. Transference of mcr-1 by conjugation to E. coli strain C600 was possible in five of the seven isolates. The mcr-1 gene was found in plasmid types IncX4 or IncI2. Three of the isolates have ESBL-encoding genes (bla_CTX-M-2, n=2; bla_CTX-M-8, n=1). We hereby report genetically distinct E. coli isolates, belonging to seven STs, harboring the mcr-1 gene, associated to community and healthcare-acquired infections, and colonization in patients from three hospitals in Sao Paulo. These findings point out for the potential spread of plasmid-mediated colistin-resistance mechanism in E. coli strains in Brazil.

Susceptibility to chlorhexidine and mupirocin among methicillin-resistant Staphylococcus aureus clinical isolates from a teaching hospital

Despite the widespread use of chlorhexidine (CHX) to prevent infection, data regarding the in vitro action of CHX against methicillin-resistant Staphylococcus aureus(MRSA) are limited. Clinical isolates from Hospital das Clinicas, Sao Paulo, Brazil, identified during 2002/2003 and 2012/2013 were studied to describe the susceptibility to CHX and mupirocin, molecular characteristics, and virulence profile of MRSA. Susceptibility test to Mupirocin was performed by the disk diffusion method and to CHX by the agar dilution technique. PCR for virulence genes, mecA gene and Staphylococcal Cassette Chromosome mec (SCCmec) types were investigated as well. Mupirocin- and CHX-resistant isolates were sequenced using the Illumina^TM plataform. Two hundred and sixteen MRSA clinical isolates were evaluated: 154 from infected and 62 from colonized patients. Resistance to mupirocin was observed in four isolates assigned as SCCmec type III and STs (ST05; ST239 and ST105) carrying mupA and blaZ, two of them co-harboring the ileS gene. Only one isolate assigned as SCCmec type III was resistant to CHX (MIC of 8.0 μg.mL^-1) and harbored the qacA gene. Resistance to chlorhexidine and mupirocin were found in isolates carrying qacA and mupA in our hospital. Since these genes are plasmid-mediated, this finding draws attention to the potential spread of resistance to mupirocin in our hospital.

Clinical and microbiological characteristics of patients colonized or infected by Stenotrophomonas maltophilia : is resistance to sulfamethoxazole/trimethoprim a problem?

Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen in the last decade. Increased resistance to sulfamethoxazole/trimethoprim (SMX/TMP) has been reported in S. maltophilia strains in the past few years, leading to few therapeutic options. We conducted a prospective multicenter study at two Brazilian teaching hospitals that identified S. maltophilia isolates and evaluated their antimicrobial susceptibility profile, SMX/TMP resistance genes and their clonality profile. A total of 106 non-repeated clinical samples of S. maltophilia were evaluated. Resistance to SMX/TMP was identified in 21.6% of the samples, and previous use of SMX/TMP occurred in 19 (82.6%). PCR detected the sul1 gene in 14 of 106 strains (13.2%). Of these isolates, nine displayed resistance to SMX/TMP. The resistant strains presented a polyclonal profile. This opportunistic pathogen has emerged in immunocompromised hosts, with few therapeutic options, which is aggravated by the description of emerging resistance mechanisms, although with a polyclonal distribution profile.

Alternative drugs against multiresistant Gram-negative bacteria

OBJECTIVES

Enterobacterales and other non-fermenting Gram-negative bacteria have become a threat worldwide owing to the frequency of multidrug resistance in these pathogens. On the other hand, efficacious therapeutic options are quickly diminishing. The aims of this study were to describe the susceptibility of 50 multiresistant Gram-negative bacteria, mostly pan-resistant, against old and less-used antimicrobial drugs and to investigate the presence of antimicrobial resistance genes.

METHODS

A total of 50 genetically distinct isolates were included in this study, including 14 Acinetobacter baumannii (belonging to ST79, ST317, ST835 and ST836), 1 Pseudomonas aeruginosa (ST245), 8 Serratia marcescens and 27 Klebsiella pneumoniae (belonging to ST11, ST340, ST258, ST16, ST23, ST25, ST101, ST234, ST437 and ST442). The isolates were submitted to antimicrobial susceptibility testing and whole-genome sequencing to evaluate lineages and resistance genes.

RESULTS

Our results showed that some strains harboured carbapenemase genes, e.g. bla_KPC-2 (28/50; 56%) and bla_OXA-23 (11/50; 22%), and other resistance genes encoding aminoglycoside-modifying enzymes (49/50; 98%). Susceptibility rates to tigecycline (96%) in all species (except P. aeruginosa), to minocycline (100%) and doxycycline (93%) in A. baumannii, to ceftazidime/avibactam in S. marcescens (100%) and K. pneumoniae (96%), and to fosfomycin in S. marcescens (88%) were high. Chloramphenicol and quinolones (6% susceptibility each) did not perform well, making their use in an empirical scenario unlikely.

CONCLUSIONS

This study involving genetically distinct bacteria showed promising results for tigecycline for all Gram-negative bacteria (except P. aeruginosa), and there was good activity of minocycline against A. baumannii, ceftazidime/avibactam against Enterobacterales, and fosfomycin against S. marcescens.

Fosfomycin in severe infections due to genetically distinct pan-drug-resistant Gram-negative microorganisms: synergy with meropenem

Background

In vitro and clinical studies using parenteral fosfomycin have suggested the possibility of using this drug against infections caused by MDR microorganisms. The aim of this study was to describe a case series of patients treated with fosfomycin who had severe infections caused by pan-drug-resistant Gram-negative bacteria.

Methods

We describe a prospective series of cases of hospitalized patients with infections caused by Gram-negative bacteria resistant to β-lactams and colistin, treated with 16 g of fosfomycin daily for 10-14 days. Isolates were tested for antimicrobial susceptibility and synergism of fosfomycin with meropenem. We tested for resistance genes and performed typing using PCR and WGS.

Results

Thirteen patients received fosfomycin (seven immunosuppressed); they had bloodstream infections (n = 11; 85%), ventilator-associated pneumonia (n = 1; 8%) and surgical site infection (n = 1; 8%), caused by Klebsiella pneumoniae (n = 9), Serratia marcescens (n = 3) and Pseudomonas aeruginosa (n = 1). Overall, eight (62%) patients were cured. Using time-kill assays, synergism between fosfomycin and meropenem occurred in 9 (82%) of 11 isolates. Typing demonstrated that K. pneumoniae were polyclonal. Eight patients (62%) had possible adverse events, but therapy was not discontinued.

Conclusions

Fosfomycin may be safe and effective against infections caused by pan-drug-resistant Gram-negative microorganisms with different antimicrobial resistance mechanisms and there seems to be synergism with meropenem.

Clonality, outer-membrane proteins profile and efflux pump in KPC- producing Enterobacter sp. in Brazil

Background

Carbapenems resistance in Enterobacter spp. has increased in the last decade, few studies, however, described the mechanisms of resistance in this bacterium. This study evaluated clonality and mechanisms of carbapenems resistance in clinical isolates of Enterobacter spp. identified in three hospitals in Brazil (Hospital A, B and C) over 7-year.

Methods

Antibiotics sensitivity, pulsed-field gel electrophoresis (PFGE), PCR for carbapenemase and efflux pump genes were performed for all carbapenems-resistant isolates. Outer-membrane protein (OMP) was evaluated based on PFGE profile.

Results

A total of 130 isolates of Enterobacter spp were analyzed, 44/105 (41, 9%) E. aerogenes and 8/25 (32,0%) E. cloacae were resistant to carbapenems. All isolates were susceptible to fosfomycin, polymyxin B and tigecycline. KPC was present in 88.6% of E. aerogenes and in all E. cloacae resistant to carbapenems. The carbapenems-resistant E. aerogenes identified in hospital A belonged to six clones, however, a predominant clone was identified in this hospital over the study period. There is a predominant clone in Hospital B and Hospital C as well. The mechanisms of resistance to carbapenems differ among subtypes. Most of the isolates co-harbored blaKPC, blaTEM and /or blaCTX associated with decreased or lost of 35–36KDa and or 39 KDa OMP. The efflux pump AcrAB-TolC gene was only identified in carbapenems-resistant E. cloacae.

Conclusions

There was a predominant clone in each hospital suggesting that cross-transmission of carbapenems-resistant Enterobacter spp. was frequent. The isolates presented multiple mechanisms of resistance to carbapenems including OMP alteration.

Chlorhexidine bathing for the prevention of colonization and infection with multidrug-resistant microorganisms in a hematopoietic stem cell transplantation unit over a 9-year period: Impact on chlorhexidine susceptibility

Health care associated infections (HAIs) are currently among the major challenges to the care of hematopoietic stem cell transplantation (HSCT) patients. The objective of the present study was to evaluate the impact of 2% chlorhexidine (CHG) bathing on the incidence of colonization and infection with vancomycin-resistant Enterococcus (VRE), multidrug-resistant (MDR) gram-negative pathogens, and to evaluate their CHG minimum inhibitory concentration (MIC) after the intervention.A quasi-experimental study with duration of 9 years was conducted. VRE colonization and infection, HAI rates, and MDR gram-negative infection were evaluated by interrupted time series analysis. The antibacterial susceptibility profile and mechanism of resistance to CHG were analyzed in both periods by the agar dilution method in the presence or absence of the efflux pump inhibitor carbonyl cyanide-m-chlorophenyl hydrazone (CCCP) and presence of efflux pumps (qacA/E, qacA, qacE, cepA, AdeA, AdeB, and AdeC) by polymerase chain reaction (PCR).The VRE colonization and infection rates were significantly reduced in the postintervention period (P = 0.001). However, gram-negative MDR rates in the unit increased in the last years of the study. The CHG MICs for VRE increased during the period of exposure to the antiseptic. A higher MIC at baseline period was observed in MDR gram-negative strains. The emergence of a monoclonal Pseudomonas aeruginosa clone was observed in the second period.Concluding, CHG bathing was efficient regarding VRE colonization and infection, whereas no similar results were found with MDR gram-negative bacteria.

Virulence and resistance pattern of a novel sequence type of linezolid-resistant Enterococcus faecium identified by whole-genome sequencing

Empirical use of linezolid has been advocated in neutropenic febrile patients colonised by vancomycin-resistant enterococci (VRE) because of the risk of bloodstream infection (BSI). This study aimed to genetically describe a vancomycin-resistant Enterococcus faecium (VREfm) BSI isolate resistant to linezolid (VRLRE) in a patient previously colonised by VREfm and to determine the incidence of colonisation and infection by VREfm in a bone marrow transplant unit over a 10-year period. Data for VREfm colonisation and infection were evaluated. PCR for the vanA and vanB genes, pulsed-field gel electrophoresis (PFGE) and microdilution antimicrobial susceptibility testing (vancomycin, teicoplanin, linezolid and aminoglycosides) were performed. Three isolates, including the VRLRE, were selected for whole-genome sequencing by Ion Torrent™, with E. faecium CP006620-Aus0085 used as a reference. Eighty-seven VREfm were analysed; all were linezolid-susceptible and harboured vanA, except for one blood isolate from a febrile neutropenic patient colonised by VREfm who received linezolid for 12 days and developed a BSI by VRLRE (linezolid MIC≥8μg/mL). Linezolid resistance was associated with a G2576T mutation in the 23SrRNA gene. PFGE analysis demonstrated that the 87 isolates belonged to four major clusters; however, the VRLRE presented only 50% similarity. Three sequence types (STs) were identified: ST412 (the predominant clone, which was more virulent compared with the other isolates); ST478 (linezolid-susceptible VREfm); and a novel ST named ST987 (VRLRE). SNP analysis showed a higher similarity between linezolid-susceptible VREfm and the predominant clone compared with VRLRE. VRLRE presented a G2576T mutation and belonged to a novel ST (ST987).