Tigecycline antimicrobial activity tested against clinical bacteria from Latin American medical centres: results from SENTRY Antimicrobial Surveillance Program (2011-2014)

Genome-wide sRNA and mRNA transcriptomic profiling insights into carbapenem-resistant Acinetobacter baumannii

Introduction

Acinetobacter baumannii (AB) is rising as a human pathogen of critical priority worldwide as it is the leading cause of opportunistic infections in healthcare settings and carbapenem-resistant AB is listed as a "super bacterium" or "priority pathogen for drug resistance" by the World Health Organization.

Methods

Clinical isolates of A. baumannii were collected and tested for antimicrobial susceptibility. Among them, carbapenem-resistant and carbapenem-sensitive A. baumannii were subjected to prokaryotic transcriptome sequencing. The change of sRNA and mRNA expression was analyzed by bioinformatics and validated by quantitative reverse transcription-PCR.

Results

A total of 687 clinical isolates were collected, of which 336 strains of A. baumannii were resistant to carbapenem. Five hundred and six differentially expressed genes and nineteen differentially expressed sRNA candidates were discovered through transcriptomic profile analysis between carbapenem-resistant isolates and carbapenem-sensitive isolates. Possible binding sites were predicted through software for sRNA21 and adeK, sRNA27 and pgaC, sRNA29 and adeB, sRNA36 and katG, indicating a possible targeting relationship. A negative correlation was shown between sRNA21 and adeK (r = -0.581, P = 0.007), sRNA27 and pgaC (r = -0.612, P = 0.004), sRNA29 and adeB (r = -0.516, P = 0.020).

Discussion

This study preliminarily screened differentially expressed mRNA and sRNA in carbapenem-resistant A. baumannii, and explored possible targeting relationships, which will help further reveal the resistance mechanism and provide a theoretical basis for the development of drugs targeting sRNA for the prevention and treatment of carbapenem-resistant A. baumannii infection.

Activity of ceftolozane/tazobactam and imipenem/relebactam against Gram-negative clinical isolates collected in Mexico-SMART 2017-2021

Objectives

To investigate the activities of ceftolozane/tazobactam and imipenem/relebactam against Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa isolated from hospitalized patients in Mexico in 2017-2021.

Methods

MICs were determined by CLSI broth microdilution and interpreted using CLSI M100 breakpoints. β-Lactamase genes were identified in ceftolozane/tazobactam-, imipenem/relebactam-, and/or imipenem-non-susceptible isolates.

Results

Ceftolozane/tazobactam and imipenem/relebactam inhibited 89% and 99% of E. coli isolates (n = 2337), and 87% and 94% of K. pneumoniae isolates (n = 1127). Sixty-four percent of E. coli and 47% of K. pneumoniae had an ESBL non-carbapenem-resistant Enterobacterales (ESBL non-CRE) phenotype. Eighty-six percent and 91% of ESBL non-CRE E. coli and K. pneumoniae were ceftolozane/tazobactam susceptible, and 99.9% and 99.8% were imipenem/relebactam susceptible. Ceftolozane/tazobactam was the most active agent studied against P. aeruginosa (n = 1068; 83% susceptible), 9-28 percentage points higher than carbapenems and comparator β-lactams excluding imipenem/relebactam (78% susceptible). Ceftolozane/tazobactam remained active against 35%-58%, and imipenem/relebactam against 32%-42%, of P. aeruginosa in meropenem-, piperacillin/tazobactam-, and cefepime-non-susceptible subsets. The majority of isolates of ceftolozane/tazobactam-non-susceptible E. coli carried an ESBL, whereas among ceftolozane/tazobactam-non-susceptible K. pneumoniae and P. aeruginosa, the majority carried carbapenemases. The most prevalent carbapenemase observed among E. coli (estimated at 0.7% of all isolates), K. pneumoniae (4.8%) and P. aeruginosa (10.0%) was an MBL. Almost all imipenem/relebactam-non-susceptible E. coli and K. pneumoniae carried MBL or OXA-48-like carbapenemases, whereas among imipenem/relebactam-non-susceptible P. aeruginosa, 56% carried MBL or GES carbapenemases.

Conclusions

Ceftolozane/tazobactam and imipenem/relebactam may provide treatment options for patients infected with β-lactam-non-susceptible Gram-negative bacilli, excluding isolates carrying an MBL- or OXA-48-like carbapenemase.

Prevalence of tigecycline resistance in methicillin-resistant Staphylococcus aureus: a systematic review and meta-analysis

Tigecycline (TG) is one of the newest antimicrobial drugs used in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. The TG Resistance Evaluation and Monitoring Test (T.E.S.T.) is a global surveillance study aimed at monitoring bacterial resistance to TG in MRSA. This study will provide comprehensive data on the activity of TG against MRSA strains across the world by 2022. An electronic search was conducted for articles published during 1997 to 2022 in Pubmed/Medline (n = 361), Scopus (n = 1735) and Web of science (n = 439) for the following keywords: ((Tygacil [Title/Abstract]) OR (Tigecycline [Title/Abstract])) AND (((Staphylococcus aureus [Title/Abstract]) OR (Methicillin resistant Staphylococcus aureus [Title/Abstract])) OR (MRSA [Title/Abstract])). The titles and abstracts of 2535 articles were screened and 48 publications that fulfilled the inclusion criteria were included. From all studies, 35 studies had a cross-sectional design, 11 studies were cohort and 2 studies were case control. Blood and respiratory tract were the main specimen source in MRSA. Meta-analysis showed the proportion of TG resistance is more than 0.004. The region (countries, continent), study type and detection method were examined as the contributing factors of heterogeneity among the studies. Microbial resistance to this antibiotic has been reported to be low, but this does not mean that it can be used widely and without supervision, but the resistance caused by it in MRSA and other pathogens should be carefully and regularly evaluated.

The burden of antimicrobial resistance in the Americas in 2019: a cross-country systematic analysis

BACKGROUND

Antimicrobial resistance (AMR) is an urgent global health challenge and a critical threat to modern health care. Quantifying its burden in the WHO Region of the Americas has been elusive-despite the region's long history of resistance surveillance. This study provides comprehensive estimates of AMR burden in the Americas to assess this growing health threat.

METHODS

We estimated deaths and disability-adjusted life-years (DALYs) attributable to and associated with AMR for 23 bacterial pathogens and 88 pathogen-drug combinations for countries in the WHO Region of the Americas in 2019. We obtained data from mortality registries, surveillance systems, hospital systems, systematic literature reviews, and other sources, and applied predictive statistical modelling to produce estimates of AMR burden for all countries in the Americas. Five broad components were the backbone of our approach: the number of deaths where infection had a role, the proportion of infectious deaths attributable to a given infectious syndrome, the proportion of infectious syndrome deaths attributable to a given pathogen, the percentage of pathogens resistant to an antibiotic class, and the excess risk of mortality (or duration of an infection) associated with this resistance. We then used these components to estimate the disease burden by applying two counterfactual scenarios: deaths attributable to AMR (compared to an alternative scenario where resistant infections are replaced with susceptible ones), and deaths associated with AMR (compared to an alternative scenario where resistant infections would not occur at all). We generated 95% uncertainty intervals (UIs) for final estimates as the 25th and 975th ordered values across 1000 posterior draws, and models were cross-validated for out-of-sample predictive validity.

FINDINGS

We estimated 569,000 deaths (95% UI 406,000-771,000) associated with bacterial AMR and 141,000 deaths (99,900-196,000) attributable to bacterial AMR among the 35 countries in the WHO Region of the Americas in 2019. Lower respiratory and thorax infections, as a syndrome, were responsible for the largest fatal burden of AMR in the region, with 189,000 deaths (149,000-241,000) associated with resistance, followed by bloodstream infections (169,000 deaths [94,200-278,000]) and peritoneal/intra-abdominal infections (118,000 deaths [78,600-168,000]). The six leading pathogens (by order of number of deaths associated with resistance) were Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. Together, these pathogens were responsible for 452,000 deaths (326,000-608,000) associated with AMR. Methicillin-resistant S. aureus predominated as the leading pathogen-drug combination in 34 countries for deaths attributable to AMR, while aminopenicillin-resistant E. coli was the leading pathogen-drug combination in 15 countries for deaths associated with AMR.

INTERPRETATION

Given the burden across different countries, infectious syndromes, and pathogen-drug combinations, AMR represents a substantial health threat in the Americas. Countries with low access to antibiotics and basic health-care services often face the largest age-standardised mortality rates associated with and attributable to AMR in the region, implicating specific policy interventions. Evidence from this study can guide mitigation efforts that are tailored to the needs of each country in the region while informing decisions regarding funding and resource allocation. Multisectoral and joint cooperative efforts among countries will be a key to success in tackling AMR in the Americas.

FUNDING

Bill & Melinda Gates Foundation, Wellcome Trust, and Department of Health and Social Care using UK aid funding managed by the Fleming Fund.

Carbapenem-Resistant Gram-Negative Bacilli Characterization in a Tertiary Care Center from El Bajio, Mexico

Carbapenem-resistant Gram-negative bacilli (CR-GNB) are a major public health concern. We aimed to evaluate the prevalence of CR-GNB and the frequency of carbapenemase-encoding genes in a tertiary referral center from El Bajio, Mexico. A cross-sectional study was conducted between January and October 2022; Gram-negative bacilli (GNB) were screened for in vitro resistance to at least one carbapenem. CR-GNB were further analyzed for carbapenemase-production through phenotypical methods and by real-time PCR for the following genes: blaKPC, blaGES, blaNDM, blaVIM, blaIMP, and blaOXA-48. In total, 37 out of 508 GNB were carbapenem-resistant (7.3%, 95% CI 5.2-9.9). Non-fermenters had higher rates of carbapenem resistance than Enterobacterales (32.5% vs. 2.6%; OR 18.3, 95% CI 8.5-39, p < 0.0001), and Enterobacter cloacae showed higher carbapenem resistance than other Enterobacterales (27% vs. 1.4%; OR 25.9, 95% CI 6.9-95, p < 0.0001). Only 15 (40.5%) CR-GNB had a carbapenemase-encoding gene; Enterobacterales were more likely to have a carbapenemase-encoding gene than non-fermenters (63.6% vs. 30.8%, p = 0.08); blaNDM-1 and blaNDM-5 were the main genes found in Enterobacterales; and blaIMP-75 was the most common for Pseudomonas aeruginosa. The mcr-2 gene was harbored in one polymyxin-resistant E. cloacae. In our setting, NDM was the most common carbapenemase; however, less than half of the CR-GNB showed a carbapenemase-encoding gene.

Global prevalence and antibiotic resistance in clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

Introduction

Stenotrophomonas maltophilia is a little-known environmental opportunistic bacterium that can cause broad-spectrum infections. Despite the importance of this bacterium as an emerging drug-resistant opportunistic pathogen, a comprehensive analysis of its prevalence and resistance to antibiotics has not yet been conducted.

Methods

A systematic search was performed using four electronic databases (MEDLINE via PubMed, Embase, Scopus, and Web of Science) up to October 2019. Out of 6,770 records, 179 were documented in the current meta-analysis according to our inclusion and exclusion criteria, and 95 studies were enrolled in the meta-analysis.

Results

Present analysis revealed that the global pooled prevalence of S. maltophilia was 5.3 % [95% CI, 4.1-6.7%], with a higher prevalence in the Western Pacific Region [10.5%; 95% CI, 5.7-18.6%] and a lower prevalence in the American regions [4.3%; 95% CI, 3.2-5.7%]. Based on our meta-analysis, the highest antibiotic resistance rate was against cefuroxime [99.1%; 95% CI, 97.3-99.7%], while the lowest resistance was correlated with minocycline [4·8%; 95% CI, 2.6-8.8%].

Discussion

The results of this study indicated that the prevalence of S. maltophilia infections has been increasing over time. A comparison of the antibiotic resistance of S. maltophilia before and after 2010 suggested there was an increasing trend in the resistance to some antibiotics, such as tigecycline and ticarcillin-clavulanic acid. However, trimethoprim-sulfamethoxazole is still considered an effective antibiotic for treating S. maltophilia infections.

Molecular tracking of carbapenem-resistant Acinetobacter baumannii clinical isolates: a multicentre study over a 4-year period across eastern China

Introduction. Colonization by carbapenem-resistant Acinetobacter baumannii (CRAB) causes therapeutic and economic problems for critically ill patients.Gap Statement. The analysis of CRAB in China was limited to certain regions.Aims. To investigate the antibiotic susceptibility, molecular characterization and clonal relationship among CRAB isolates from multiple hospitals of eastern China.Methodology. Isolates from 29 tertiary hospitals from September 2015 to September 2018 were recovered. All strains were analysed using antimicrobial susceptibility testing to detect their tolerance. PCR was also used to detect multiple β-lactamase genes. After multilocus sequence typing (MLST) of seven house-keeping genes. eBURST was used to assess clonal complexes and explore evolutionary relationships.Results. All isolates showed resistance to carbapenems, while remaining susceptible to colistin and tigecycline. All isolates were detected with bla _OXA-51 gene by PCR, and 80.1 % harboured the bla _OXA-23 gene. The prevalence of bla_OXA-23 gene was remarkably increased from 50.7 % in 2015 to 90.5 % in 2018. Other genes such as bla _OXA-24, bla _OXA-58, bla _IMP-2/4, bla _VIM-2, bla _SHV, bla _AmpC and bla _TEM were also obtained. While bla _KPC, bla _NDM-1, bla _IMP-4 and bla _SIM-1 were not found in these strains. MLST showed all isolates could be divided into 26 known sequence types (STs) and ten novel STs and 47.2 % isolates belong to ST195 and ST208. eBURST revealed clonal complex 92 as the major clonal complex (98.4 %), which includes 88.5 % (23/26) of known STs and 80 % (8/10) of unknown STs. Phylogenetic analysis also found that almost all CRAB isolates could cluster into one lineage, suggesting an epidemic of this CRAB lineage. This indicated severe nosocomial infections of CRAB in multiple hospitals of eastern China.Conclusion. An outbreak of ST195 and ST208 CRAB-resistant clones with bla _OXA-23 gene might be happening in multiple hospitals in eastern China.

In vitro activity and adaptation strategies of eravacycline in clinical Enterococcus faecium isolates from China

Eravacycline (Erava) is a synthetic fluorocycline with potent antimicrobial activity against a wide range of Gram-positive bacteria. This study aimed to investigate the in vitro antimicrobial activity and resistance mechanism of Erava in clinical E. faecium isolates from China. Erava minimum inhibitory concentrations (MICs) against clinical E. faecium isolates-including those resistant to linezolid (LZD) or harboring the tetracycline (Tet) resistance genes was ≤0.25 mg l^-1. Moreover, our data indicated that clinical isolates of E. faecium with Erava MIC 0.25 mg l^-1 were predominantly shown to belong to Sequence-type 78 (ST78) and ST80. The prevalence of Erava heteroresistance in clinical E. faecium strain was 2.46% (3/122). The increased Erava MIC values of heteroresistance-derived E. faecium clones could be significantly reduced by efflux pump inhibitors (EPIs). Furthermore, comparative proteomics results showed that efflux pumps lmrA, mdlA, and mdlB contributed significantly to the acquisition of Erava resistance in E. faecium. In addition, a genetic mutation in 16 S rRNA (G190A) were detected in resistant E. faecium isolates induced by Erava. In summary, Erava exhibits potent in vitro antimicrobial activity against E. faecium, but mutation of Tet target sites and elevated expression of efflux pumps under Erava selection results in Erava resistance.

Clinical challenges treating Stenotrophomonas maltophilia infections: an update

Stenotrophomonas maltophilia is a non-fermenting, Gram-negative bacillus that has emerged as an opportunistic nosocomial pathogen. Its intrinsic multidrug resistance makes treating infections caused by S. maltophilia a great clinical challenge. Clinical management is further complicated by its molecular heterogeneity that is reflected in the uneven distribution of antibiotic resistance and virulence determinants among different strains, the shortcomings of available antimicrobial susceptibility tests and the lack of standardized breakpoints for the handful of antibiotics with in vitro activity against this microorganism. Herein, we provide an update on the most recent literature concerning these issues, emphasizing the impact they have on clinical management of S. maltophilia infections.

Prevalence and Molecular Typing of Carbapenemase-Producing Enterobacterales among Newborn Patients in Italy

The spread of carbapenemase-producing Enterobacterales (CPE), especially Klebsiella pneumoniae (K. pneumoniae) and Escherichia coli (E. coli), is a serious public health threat in pediatric hospitals. The associated risk in newborns is due to their underdeveloped immune system and limited treatment options. The aim was to estimate the prevalence and circulation of CPE among the neonatal intensive units of a major pediatric hospital in Italy and to investigate their molecular features. A total of 124 CPE were isolated from rectal swabs of 99 newborn patients at Bambino Gesù Children’s Hospital between July 2016 and December 2019. All strains were characterized by antimicrobial susceptibility testing, detection of resistance genes, and PCR-based replicon typing (PBRT). One strain for each PBRT profile of K. pneumoniae or E. coli was characterized by multilocus-sequence typing (MLST). Interestingly, the majority of strains were multidrug-resistant and carried the blaNDM gene. A large part was characterized by a multireplicon status, and FII, A/C, FIA (15%) was the predominant. Despite the limited size of collection, MLST analysis revealed a high number of Sequence Types (STs): 14 STs among 28 K. pneumoniae and 8 STs among 11 E. coli, with the prevalence of the well-known clones ST307 and ST131, respectively. This issue indicated that some strains shared the same circulating clone. We identified a novel, so far never described, ST named ST10555, found in one E. coli strain. Our investigation showed a high heterogeneity of CPE circulating among neonatal units, confirming the need to monitor their dissemination in the hospital also through molecular methods.

Epidemiology and mechanisms of tigecycline- and carbapenem- resistant Enterobacter cloacae in Southwest China: a five-year retrospective study

BACKGROUND

The prevalence and molecular epidemiology of tigecycline resistance in carbapenem-resistant Enterobacter cloacae (CREC) in mainland China is unknown. In this study, we aimed to investigate the molecular characteristics and resistance mechanism of tigecycline-resistant CREC (TCREC) in Southwest China.

METHODS

We conducted a five-year retrospective study. TCREC isolates were subjected to antimicrobial susceptibility testing, pulsed-field gel electrophoresis, and multilocus sequence typing. We determined the presence of genes, deficiency of outer membrane proteins, and expression of efflux pumps using polymerase chain reaction (PCR), reverse transcription-polymerase chain reaction (RT-PCR), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

RESULTS

We found that a high incidence rate of 21.7% (36/166) of isolates were positive for TCREC. All isolates were resistant to ertapenem whereas 67% remained susceptible to imipenem and meropenem. ST88 (10/36, 27.8%) was predominant and associated with moderate resistance to tigecycline and high resistance to carbapenems, followed by ST256 (3/36, 8.3%), ST78 (2/36, 5.6%), ST577 (2/36, 5.6%), and ST102 (2/36, 5.6%). bla_NDM-1 (6/36, 16.6%) carriers was the most common carbapenemase gene and ST88 (5/6, 83.3%) was the most common type, followed by bla_IMP-8 (n=3/36, 8.3%). Coexistence of extensive-spectrum β-lactamase (ESBL) genes and outer membrane protein OmpF and/or OmpC loss were found in 27 out of 36 isolates, in addition, increased co-expression of efflux pump genes acrB and oqxA was identified in 25 out of 36 isolates, which may together contribute to co-resistance to carbapenem and tigecycline.

CONCLUSION

Most ST88 strains carried carbapenemases, especially New Delhi metallo-β-lactamase 1 (NDM-1). Overexpression of efflux pumps contributed to tigecycline resistance. The presence of carbapenemase and/or ESBL genes and lack of outer membrane proteins, but not overexpression of efflux pumps, may confer carbapenem resistance. Reasonable supervision and management the epidemic of TCREC will help to stem the transmission of the isolates.

In vitro activity of ceftazidime-avibactam against Enterobacterales and Pseudomonas aeruginosa isolates collected in Latin America as part of the ATLAS global surveillance program, 2017-2019

The Antimicrobial Testing Leadership and Surveillance (ATLAS) global surveillance program collected clinical isolates of Enterobacterales (n = 8416) and Pseudomonas aeruginosa (n = 2521) from 41 medical centers in 10 Latin American countries from 2017 to 2019. In vitro activities of ceftazidime-avibactam and comparators were determined using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method. Overall, 98.1% of Enterobacterales and 86.9% of P. aeruginosa isolates were susceptible to ceftazidime-avibactam. When isolates were analyzed by country of origin, susceptibility to ceftazidime-avibactam for Enterobacterales ranged from 97.8% to 100% for nine of 10 countries (except Guatemala, 86.3% susceptible) and from 75.9% to 98.4% for P. aeruginosa in all 10 countries. For Enterobacterales, 100% of AmpC-positive, ESBL- and AmpC-positive, GES-type carbapenemase-positive, and OXA-48-like-positive isolates were ceftazidime-avibactam-susceptible as were 99.8%, 91.8%, and 74.7% of ESBL-positive, multidrug-resistant (MDR), and meropenem-nonsusceptible isolates. Among meropenem-nonsusceptible isolates of Enterobacterales, 24.4% (139/570) carried a metallo-β-lactamase (MBL); 83.3% of the remaining meropenem-nonsusceptible isolates carried another class of carbapenemase and 99.4% of those isolates were ceftazidime-avibactam-susceptible. Among meropenem-non-susceptible isolates of P. aeruginosa (n = 835), 25.6% carried MBLs; no acquired β-lactamase was identified in the majority of isolates (64.8%; 87.2% of those isolates were ceftazidime-avibactam-susceptible). Overall, clinical isolates of Enterobacterales collected in Latin America from 2017 to 2019 were highly susceptible to ceftazidime-avibactam, including isolates carrying ESBLs, AmpCs, and KPCs. Country-specific variation in susceptibility to ceftazidime-avibactam was more common among isolates of P. aeruginosa than Enterobacterales. The frequency of MBL-producers among Enterobacterales from Latin America was low (1.7% of all isolates; 146/8,416), but higher than reported in previous surveillance studies.

Advances in the Microbiology of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an opportunistic pathogen of significant concern to susceptible patient populations. This pathogen can cause nosocomial and community-acquired respiratory and bloodstream infections and various other infections in humans. Sources include water, plant rhizospheres, animals, and foods. Studies of the genetic heterogeneity of S. maltophilia strains have identified several new genogroups and suggested adaptation of this pathogen to its habitats. The mechanisms used by S. maltophilia during pathogenesis continue to be uncovered and explored. S. maltophilia virulence factors include use of motility, biofilm formation, iron acquisition mechanisms, outer membrane components, protein secretion systems, extracellular enzymes, and antimicrobial resistance mechanisms. S. maltophilia is intrinsically drug resistant to an array of different antibiotics and uses a broad arsenal to protect itself against antimicrobials. Surveillance studies have recorded increases in drug resistance for S. maltophilia, prompting new strategies to be developed against this opportunist. The interactions of this environmental bacterium with other microorganisms are being elucidated. S. maltophilia and its products have applications in biotechnology, including agriculture, biocontrol, and bioremediation.

Polymyxin Resistance Among XDR ST1 Carbapenem-Resistant Acinetobacter baumannii Clone Expanding in a Teaching Hospital

Acinetobacter baumannii is an opportunistic pathogen primarily associated with multidrug-resistant nosocomial infections, for which polymyxins are the last-resort antibiotics. This study investigated carbapenem-resistant A. baumannii strains exhibiting an extensively drug-resistant (XDR) phenotype, including four isolates considered locally pan drug-resistant (_LPDR), isolated from inpatients during an outbreak at a teaching hospital in Brazil. ApaI DNA macrorestriction followed by PFGE clustered the strains in three pulsotypes, named A to C, among carbapenem-resistant A. baumannii strains. Pulsotypes A and B clustered six polymyxin-resistant A. baumannii strains. MLST analysis of representative strains of pulsotypes A, B, and C showed that they belong, respectively, to sequence types ST1 (clonal complex, CC1), ST79 (CC79), and ST903. Genomic analysis of international clones ST1 and ST79 representative strains predicted a wide resistome for β-lactams, aminoglycosides, fluoroquinolones, and trimethoprim-sulfamethoxazole, with bla_OXA–23 and bla_OXA–72 genes encoding carbapenem resistance. Amino acid substitutions in PmrB (Thr232Ile or Pro170Leu) and PmrC (Arg125His) were responsible for polymyxin resistance. Although colistin MICs were all high (MIC ≥ 128 mg/L), polymyxin B MICs varied; strains with Pro170Leu substitution in PmrB had MICs > 128 mg/L, while those with Thr232Ile had lower MICs (16–64 mg/L), irrespective of the clone. Although the first identified polymyxin-resistant A. baumannii strain belonged to ST79, the ST1 strains were endemic and caused the outbreak most likely due to polymyxin B use. The genome comparison of two ST1 strains from the same patient, but one susceptible and the other resistant to polymyxin, revealed mutations in 28 ORFs in addition to pmrBC. The ORF codifying an acyl-CoA dehydrogenase has gained attention due to its fatty acid breakdown and membrane fluidity involvement. However, the role of these mutations in the polymyxin resistance mechanism remains unknown. To prevent the dissemination of XDR bacteria, the hospital infection control committee implemented the patient bathing practice with a 2% chlorhexidine solution, a higher concentration than all A. baumannii chlorhexidine MICs. In conclusion, we showed the emergence of polymyxin resistance due to mutations in the chromosome of the carbapenem-resistant A. baumannii ST1, a high-risk global clone spreading in this hospital.

Epidemiology and Diagnostics of Carbapenem Resistance in Gram-negative Bacteria

Carbapenem resistance in gram-negative bacteria has caused a global epidemic that continues to grow. Although carbapenemase-producing Enterobacteriaceae have received the most attention because resistance was first reported in these pathogens in the early 1990s, there is increased awareness of the impact of carbapenem-resistant nonfermenting gram-negative bacteria, such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. Moreover, evaluating the problem of carbapenem resistance requires the consideration of both carbapenemase-producing bacteria as well as bacteria with other carbapenem resistance mechanisms. Advances in rapid diagnostic tests to improve the detection of carbapenem resistance and the use of large, population-based datasets to capture a greater proportion of carbapenem-resistant organisms can help us gain a better understanding of this urgent threat and enable physicians to select the most appropriate antibiotics.

Coagulase-negative staphylococci in outpatient routines: the implications of switching from CLSI to BrCAST/EUCAST guidelines

Coagulase-negative staphylococci (CoNS) are frequently isolated in clinical specimens and are important reservoirs of resistance genes. In 2019, the Brazilian government set the BrCAST/EUCAST (Brazilian Committee on Antimicrobial Susceptibility Testing) guidelines as the national standard, resulting in changes in the interpretation of CoNS susceptibility tests. From outpatients, disk-diffusion susceptibility of 65 CoNS cultures were evaluated and compared using classification criteria from both CLSI and BrCAST/EUCAST. The isolates were identified using matrix assisted laser desorption ionization-time of flight (MALDI-TOF), and the presence of the mecA gene was determined. The most prevalent species were Staphylococcus saprophyticus (32.3%), S. haemolyticus (18.5%), and S. epidermidis (9.2%). Almost perfect agreement was seen between the guidelines, except concerning oxacillin and gentamicin, and the prevalence of multidrug resistant isolates increased with the use of BrCAST/EUCAST. Of all, 15 (23.1%) isolates, mainly S. epidermidis and S. haemolyticus, were positive for the mecA gene, and only three were detected when using CLSI or BrCAST/EUCAST disk-diffusion screening. This, using either guideline, could reveal the difficulty of determining oxacillin resistance. Using warning zones or molecular methods might well be indicated for CoNS. In conclusion, adoption of the BrCAST/EUCAST guidelines will result in certain artificial changes in epidemiological susceptibility profiles, and clinicians and institutions should be aware of the possible implications.

High Prevalence of CTX-M Type Extended-Spectrum Beta-Lactamase Genes and Detection of NDM-1 Carbapenemase Gene in Extraintestinal Pathogenic Escherichia coli in Cuba

Increase of extraintestinal pathogenic Escherichia coli (ExPEC) showing resistance to beta-lactams is a major public health concern. This study was conducted as a first molecular epidemiological study on ExPEC in Cuba, regarding prevalence of extended-spectrum beta-lactamases (ESBLs) and carbapenemase genes. A total of 306 ExPEC isolates collected in medical institutions in 16 regions in Cuba (2014–2018) were analyzed for their genotypes and presence of genes encoding ESBL, carbapenemase, plasmid-mediated quinolone resistance (PMQR) determinants by PCR and sequencing. The most common phylogenetic group of ExPEC was B2 (49%), followed by D (23%), A (21%), and B1 (7%). Among ESBL genes detected, bla_CTX-M was the most common and detected in 61% of ExPEC, with bla_CTX-M-15 being dominant and distributed to all the phylogenetic groups. NDM-1 type carbapenemase gene was identified in two isolates of phylogenetic group B1-ST448. Phylogenetic group B2 ExPEC belonged to mostly ST131 (or its single-locus variant) with O25b allele, harboring bla_CTX-M-27, and included an isolate of emerging type ST1193. aac (6’)-Ib-cr was the most prevalent PMQR gene (40.5%), being present in 54.5% of CTX-M-positive isolates. These results indicated high prevalence of CTX-M genes and the emergence of NDM-1 gene among recent ExPEC in Cuba, depicting an alarming situation.

In Vitro Activity Of Ceftaroline And Comparators Against Staphylococcus aureus Isolates: Results From 6 Years Of The ATLAS Program (2012 To 2017)

Background

Ceftaroline is effective against methicillin-resistant Staphylococcus aureus (MRSA), but the resistance patterns still need to be defined. This study aimed to investigate the susceptibility of S. aureus to ceftaroline and comparator antimicrobial agents in patients hospitalized due to infection and to observe the patterns among different regions and over the years.

Methods

The Antimicrobial Testing Leadership And Surveillance (ATLAS) program includes medical centers located in five geographical regions (Europe, Asia-Pacific, South America, Africa-West Asia, and the United States). The isolates were collected from different specimens from patients hospitalized between 2012 and 2017 due to documented complicated skin and soft tissue infection, complicated intra-abdominal infection, complicated urinary tract infection, lower respiratory tract infection, and bloodstream infection.

Results

During the study period, 61,045 isolates were tested, including 35,837 MRSA isolates (58.7%) and 25,208 methicillin-sensitive S. aureus (MSSA) isolates (41.3%). For MRSA, the minimal inhibitory concentration (MIC)₅₀, MIC₉₀, and MIC range of ceftaroline were 0.5, 2, and 0.015–64 μg/mL. The proportion of susceptible MRSA strains was 89.3%. The proportion of resistant MRSA strains was 0.7%. The susceptibility of all S. aureus, MRSA, and MSSA strains to ceftaroline remained relatively constant from 2012 to 2017. The susceptibility to ceftaroline of S. aureus, MRSA, and MSSA strains from the United States, Europe, South America, and Africa/West Asia was high, while the susceptibility of the strains from Asia-Pacific was lower, especially for MRSA.

Conclusion

This study reveals the patterns of ceftaroline susceptibility of MRSA and MSSA around the world and over 6 years.

Multidrug- and Extensively Drug-Resistant Acinetobacter baumannii in a Tertiary Hospital from Brazil: The Importance of Carbapenemase Encoding Genes and Epidemic Clonal Complexes in a 10-Year Study

This study aimed to characterize the main mechanisms of acquired antimicrobial resistance of 103 multidrug-resistant Acinetobacter baumannii isolated from bloodstream from 2006 to 2016 from a hospital in Londrina, Brazil. All 103 isolates were identified as A. baumannii by amplification of the bla_OXA-51-like and rpoB genes. Mortality was observed in the majority (81.6%) of the patients. High non-susceptibility rates (100.0-10.7%) were obtained for the evaluated antimicrobials, including colistin, polymyxin B, and tigecycline, and most isolates were classified as extensively drug-resistant (78.6%). Carbapenemase production was observed in 92.2% of the isolates. All carbapenem-resistant isolates showed a carbapenem-hydrolyzing class D β-lactamase being either bla_OXA-23-like (97.9%) or bla_OXA-143-like (2.1%). None of the isolates had the genes bla_OXA-24-like, bla_OXA-58-like, bla_OXA-48, bla_KPC, bla_NDM, bla_SPM-1, bla_SIM-1, bla_VIM, bla_IMP, bla_GIM, bla_GES, mcr-1, qnrA, qnrB, qnrC, qnrS, and qnrVc. As a genetic context of the bla_OXA-23-like gene, Tn2006 was predominated (86.0%), and Tn2008 was less frequent (12.9%). Isolates harboring the bla_OXA-143-like gene showed the bla_OXA-253-like variant. A polyclonal profile was observed among the A. baumannii isolates. The presence of the international clonal complexes CC113/79, CC109/1, CC110/25, and CC103/15 was detected, with prevalence of CC113/79 (38.8%). This study provides essential information to understand the antimicrobial resistance patterns of A. baumannii and can be used to strengthen infection control measures in our hospital. Also, the study reinforces the urgent need to develop stewardship programs to avoid the spread and potential outbreaks by this pathogen.

In vitro studies evaluating the activity of imipenem in combination with relebactam against Pseudomonas aeruginosa

BACKGROUND

The prevalence of antibiotic resistance is increasing, and multidrug-resistant Pseudomonas aeruginosa has been identified as a serious threat to human health. The production of β-lactamase is a key mechanism contributing to imipenem resistance in P. aeruginosa. Relebactam is a novel β-lactamase inhibitor, active against class A and C β-lactamases, that has been shown to restore imipenem susceptibility. In a series of studies, we assessed the interaction of relebactam with key mechanisms involved in carbapenem resistance in P. aeruginosa and to what extent relebactam might overcome imipenem non-susceptibility.

RESULTS

Relebactam demonstrated no intrinsic antibacterial activity against P. aeruginosa, had no inoculum effect, and was not subject to efflux. Enzymology studies showed relebactam is a potent (overall inhibition constant: 27 nM), practically irreversible inhibitor of P. aeruginosa AmpC. Among P. aeruginosa clinical isolates from the SMART global surveillance program (2009, n = 993; 2011, n = 1702; 2015, n = 5953; 2016, n = 6165), imipenem susceptibility rates were 68.4% in 2009, 67.4% in 2011, 70.4% in 2015, and 67.3% in 2016. With the addition of 4 μg/mL relebactam, imipenem susceptibility rates increased to 87.6, 86.0, 91.7, and 89.8%, respectively. When all imipenem-non-susceptible isolates were pooled, the addition of 4 μg/mL relebactam reduced the mode imipenem minimum inhibitory concentration (MIC) 8-fold (from 16 μg/mL to 2 μg/mL) among all imipenem-non-susceptible isolates. Of 3747 imipenem-non-susceptible isolates that underwent molecular profiling, 1200 (32%) remained non-susceptible to the combination imipenem/relebactam (IMI/REL); 42% of these encoded class B metallo-β-lactamases, 11% encoded a class A GES enzyme, and no class D enzymes were detected. No relationship was observed between alleles of the chromosomally-encoded P. aeruginosa AmpC and IMI/REL MIC.

CONCLUSIONS

IMI/REL exhibited potential in the treatment of carbapenem-resistant P. aeruginosa infections, with the exception of isolates encoding class B, some GES alleles, and class D carbapenemases.

Antimicrobial susceptibility among Streptococcus pneumoniae and Haemophilus influenzae collected globally between 2015 and 2017 as part of the Tigecycline Evaluation and Surveillance Trial (TEST)

Purpose: In order to understand the prevalence of Streptococcus pneumoniae and Haemophilus influenzae globally and provide the basis for rational use of antimicrobials in clinical settings, in vitro activity of tigecycline and comparative agents was evaluated against 3929 S. pneumoniae and 4043 H. influenzae isolates obtained from 150 centers globally between 2015 and 2017 as a part of the Tigecycline Evaluation and Surveillance Trial (TEST). Methods: Broth microdilution methods were performed to determine the minimum inhibitory concentration (MIC) of the isolates according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). The CLSI breakpoint was used to determine antimicrobial susceptibilities, except for that of tigecycline, for which the US Food and Drug Administration (FDA) breakpoints were used. Results: More than 99% of S. pneumoniae isolates were susceptible to vancomycin (100%), linezolid (100%), tigecycline (99.9%), and levofloxacin (99.1%). Macrolides (erythromycin, azithromycin, and clarithromycin, 67.1-69.4% susceptibility globally) and penicillin (61.7% in globally) were the drugs with more resisitance to S. pneumoniae. Penicillin-intermediate and -resistant isolates were found in 24.8% and 13.6% of S. pneumoniae isolates. H. influenzae was highly susceptible (>98.7%) to all antibiotics tested except for ampicillin, for which susceptibility was 76.1%. The number of drugs with the lowest susceptibility calculated in Asia were far more than other regions, with 61.5% (8 in 13 drugs) in S. pneumoniae and 70.0% (7 in 10 drugs) in H. influenzae, respectively. Conclusions: Vancomycin, linezolid, tigecycline, and levofloxacin can be used as the first choice in the empirical therapy of infection disease caused by S. pneumoniae. But macrolides and penicillin should be used prudently in treatment of the infection caused by S. pneumoniae, as well as ampicillin treat the infection caused by H. influenzae. Asia was the region with the most severe resistance in S. pneumoniae and H. influenzae.

High prevalence of CTX-M-1 group in ESBL-producing enterobacteriaceae infection in intensive care units in southern Chile

Enterobacteria-producing extended-spectrum β-lactamases (ESBL) play an important role in healthcare infections, increasing hospitalization time, morbidity and mortality rates. Among several ESBLs that emerge from these pathogens, CTX-M-type enzymes had the most successful global spread in different epidemiological settings. Latin America presents high prevalence of CTX-M-2 in ESBL-producing enterobacterial infections with local emergence of the CTX-M-1 group. However, this high prevalence of the CTX-M-1 group has not yet been reported in Chile. The aim of this study was to identify ESBLs among enterobacteria isolated from clinical samples of critically ill patients from southern Chile. One-hundred thirty seven ESBL-producing bacteria were isolated from outpatients from all critical patient units from Hernán Henríquez Aravena Hospital. Phenotype characterization was performed by antibiogram, screening of ESBL, and determination of minimum inhibitory concentration (MIC). PCR was used for genetic confirmation of resistance. Molecular typing was performed by ERIC-PCR. ESBL-producing isolates were identified as Klebsiella pneumoniae (n = 115), Escherichia coli (n = 18), Proteus mirabilis (n = 3), and Enterobacter cloacae (n = 1), presenting multidrug resistance profiles. PCR amplification showed that the strains were positive for blaSHV (n = 111/81%), blaCTX-M-1 (n = 116/84.7%), blaTEM (n = 100/73%), blaCTX-M-2 (n = 28/20.4%), blaCTX-M-9 (0.7%), blaPER-1 (0.7%), and blaGES-10 (0.7%). The multiple production of ESBL was observed in 93% of isolates, suggesting high genetic mobility independent of the clonal relationship. The high frequency of the CTX-M-1 group and a high rate of ESBL co-production are changing the epidemiology of the ESBL profile in Chilean intensive care units. This epidemiology is a constant and increasing challenge, not only in Chile, but worldwide.

In Vitro Activity of Ceftazidime-Avibactam against Clinical Isolates of Enterobacteriaceae and Pseudomonas aeruginosa Collected in Latin American Countries: Results from the INFORM Global Surveillance Program, 2012 to 2015

The International Network for Optimal Resistance Monitoring (INFORM) global surveillance program collected clinical isolates of Enterobacteriaceae (n = 7,665) and Pseudomonas aeruginosa (n = 1,794) from 26 medical centers in six Latin American countries from 2012 to 2015. The in vitro activity of ceftazidime-avibactam and comparators was determined for the isolates using the Clinical and Laboratory Standards Institute (CLSI) reference broth microdilution method. Enterobacteriaceae were highly susceptible (99.7%) to ceftazidime-avibactam, including 99.9% of metallo-β-lactamase (MBL)-negative isolates; 87.4% of all P. aeruginosa isolates and 92.8% of MBL-negative isolates were susceptible to ceftazidime-avibactam. Susceptibility to ceftazidime-avibactam ranged from 99.4% to 100% for Enterobacteriaceae and from 79.1% to 94.7% for P. aeruginosa when isolates were analyzed by country of origin. Ceftazidime-avibactam inhibited 99.6% to 100% of Enterobacteriaceae isolates that carried serine β-lactamases, including extended-spectrum β-lactamases (ESBLs), AmpC cephalosporinases, and carbapenemases (KPC and OXA-48-like) as well as 99.7%, 99.6%, 99.5%, and 99.2% of MBL-negative isolates demonstrating ceftazidime-nonsusceptible, multidrug-resistant (MDR), meropenem-nonsusceptible, and colistin-resistant phenotypes, respectively. Among carbapenem-nonsusceptible isolates of P. aeruginosa (n = 750), 14.7% carried MBLs with or without additional acquired serine β-lactamases, while in the majority of isolates (70.0%), no acquired β-lactamase was identified. Ceftazidime-avibactam inhibited 89.5% of carbapenem-nonsusceptible P. aeruginosa isolates in which no acquired β-lactamase was detected. Overall, clinical isolates of Enterobacteriaceae collected in Latin America from 2012 to 2015 were highly susceptible to ceftazidime-avibactam, including isolates that exhibited resistance to ceftazidime, meropenem, colistin, or an MDR phenotype. Country-specific variations were noted in the susceptibility of P. aeruginosa isolates to ceftazidime-avibactam.

Risk factors with the development of infection with tigecycline- and carbapenem-resistant Enterobacter cloacae

Background

Tigecycline is regarded as a last resort treatment for carbapenem-resistant Enterobacter cloacae (CREC) infections, and increasing numbers of tigecycline- and carbapenem-resistant E. cloacae (TCREC) isolates have been reported in recent years. However, risk factors and clinical impacts of these isolates are poorly characterized.

Patients and methods

We conducted a retrospective case-case-control study of hospitalized patients with TCREC infection during the period 2012-2016 in Chongqing, China. Case patients with TCREC and those with CREC were compared to a control group with no E. cloacae infection. Multivariate logistic regression models were used to identify independent risk factors for acquiring TCREC and CREC.

Results

A total of 36 TCREC cases, 36 CREC cases, and 100 controls were enrolled in our study. Multivariable analysis indicated that nasal catheter (OR: 8.9; 95% CI: 1.1-75.2), exposure to penicillin (OR: 95.9; 95% CI: 8.9-1038.3), aminoglycosides (OR: 42.1; 95% CI: 2.1-830.6), and fluoroquinolones (OR: 18.6; 95% CI: 1.9-185.6) were independent predictors for acquiring TCREC. In addition, venous catheterization (OR: 12.2; 95% CI: 2.5-58.5), penicillin (OR: 30.8; 95% CI: 7.9-120.0), and broad-spectrum cephalosporin (OR: 5.0; 95% CI: 1.5-17.3) were independently associated with CREC acquisition.

Conclusion

Reasonable antibiotic stewardship programs and surveillance are necessary to control the tigecycline resistance among high-risk patients.

Emergence of IncFIA Plasmid-Carrying blaNDM-1 Among Klebsiella pneumoniae and Enterobacter cloacae Isolates in a Tertiary Referral Hospital in Mexico

The emergence of New Delhi metallo-β-lactamase 1 on carbapenemase-producing bacteria has raised a major worldwide public health concern. This study reports the dissemination of bla_NDM-1 in carbapenem-resistant isolates that caused nosocomial infections in a tertiary hospital in Mexico City. Seven Enterobacter cloacae and three Klebsiella pneumoniae nosocomial isolates from the same time period harbored the bla_NDM-1 gene. The resistance phenotype and the bla_NDM-1 gene were transferred through conjugative plasmids belonging to the incompatibility group IncFIA of 85, 101, and 195 kb in E. cloacae and 95 and 101 kb in K. pneumoniae isolates. Restriction fragment length polymorphism analysis showed that bla_NDM-1 was carried in similar plasmids with molecular sizes of 101 and 85 kb, each one in three isolates of E. cloacae and one of 101 kb on two isolates of K. pneumoniae. During a 9-month period, six of the seven isolates of E. cloacae analyzed harbored bla_NDM-1 and belonged to clone E1. Similarly, over a 5-month period, two of the three K. pneumoniae isolates that harbored bla_NDM-1 belonged to clone K1. These results demonstrate the horizontal transfer of bla_NDM-1 between different bacterial species, dissemination of clones with high levels of resistance to carbapenems, and underscore the need for heightened measures to control their further spread.

Antimicrobial susceptibility among gram-positive and gram-negative blood-borne pathogens collected between 2012-2016 as part of the Tigecycline Evaluation and Surveillance Trial

Background

Antimicrobial activity of tigecycline and comparator agents was assessedin vitroagainst 27857 isolates source from blood samples collected between 2012 and 2016 as part of the Tigecycline Evaluation and Surveillance Trial (TEST).

Methods

The broth microdilution methods was used to determine  minimum inhibitory concentrations (MIC) of blood-borne isolates according to guildlines of the Clinical and Laboratory Standards Institute (CLSI). Antimicrobial susceptibility breakpoints from CLSI guidelines were used as standards to determine susceptibility against comparator agents, whereas tigecycline breakpoints were provided by the US Food and Drug Administration (FDA).

Results

More than 91% Enterobacteriaceae isolates, belonging to Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacaeandSerratia marcescens, were susceptible to amikacin, meropenem, and tigecycline. Meropenem resistance was observed in 8% ofK.pneumoniae isolates worldwide. Extended-spectrum β-lactamase (ESBL) was produced in 15.9 and 20.9%E.coli and K.pneumoniaeisolates, respectively. MIC₉₀ of tigecycline against Acinetobacter baumannii was 2 μg/ml.  The highest proportion of susceptible A.baumanniiisolates was 70.8% for minocycline. Among P.aeruginose  isolates worldwide, 71.1-94.9% were susceptible to six antibiotics. Almost all Staphylococcus aureusisolates were susceptible to linezolid(100%), vancomycin(100%), and tigecycline (99.9%). The proportion of methicillin-resistant S.aureus (MRSA) was 33.0% among S.aureusisolates worldwide; it was highest in Asia with 46.6%, followed by North America and Latin America with 37.7 and 34.2%, respectively. Vancomycin-resistant (VR) isolates represented 1.4% ofEnterococcus faecalis (VR.E.faecalis) and 27.6% of Enterococcus faecium(VR.E.faecium). Highest percentages of VR.E.faeciumwere found in North America and Latin America, with 61.6 and 58.1% of the isolates, respectively. Production of penicillin-resistant Streptococcus pneumoniae(PRSP) represented 9.0% of S. pneumoniae isolates worldwide; the PRSP proportion was 25.8% in Asia, 13.0% in Africa, and 11.8% in Latin America.

Conclusions

In our study, tigecycline was the only antibiotic that was active against over 90% of all major blood-borne pathogens. A global comparison revealed that antimicrobial resistance was higher in Africa, Asia and Latin America than in Europe and North America.

Molecular basis for the emergence of a new hospital endemic tigecycline-resistant Enterococcus faecalis ST103 lineage

Enterococcus faecalis are a major cause of nosocomial infection worldwide, and the spread of vancomycin resistant strains (VRE) limits treatment options. Tigecycline-resistant VRE began to be isolated from inpatients at a Brazilian hospital within months following the addition of tigecycline to the hospital formulary. This was found to be the result of a spread of an ST103 E. faecalis clone. Our objective was to identify the basis for tigecycline resistance in this lineage. The genomes of two closely related tigecycline-susceptible (MIC = 0.06 mg/L), and three representative tigecycline-resistant (MIC = 1 mg/L) ST103 isolates were sequenced and compared. Further, efforts were undertaken to recapitulate the emergence of resistant strains in vitro. The specific mutations identified in clinical isolates in several cases were within the same genes identified in laboratory-evolved strains. The contribution of various polymorphisms to the resistance phenotype was assessed by trans-complementation of the wild type or mutant alleles, by testing for differences in mRNA abundance, and/or by examining the phenotype of transposon insertion mutants. Among tigecycline-resistant clinical isolates, five genes contained non-synonymous mutations, including two genes known to be related to enterococcal tigecycline resistance (tetM and rpsJ). Finally, within the in vitro-selected resistant variants, mutation in the gene for a MarR-family response regulator was associated with tigecycline resistance. This study shows that E. faecalis mutates to attain tigecycline resistance through the complex interplay of multiple mechanisms, along multiple evolutionary trajectories.

Molecular Epidemiology and Drug Resistance Pattern of Carbapenem-Resistant Klebsiella pneumoniae Isolates from Iran

The emergence and dissemination of carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates and their involvement in several nosocomial outbreaks are of high concern. This study was conducted to investigate the genetic relatedness and molecular determinants of carbapenem resistance in 100 CRKP isolates. Susceptibility to carbapenems as well as other antibiotics was determined by using disk diffusion method. The Modified Hodge test was performed for detection of carbapenemase production. The minimum inhibitory concentrations of selected antibiotics were determined by broth microdilution method. The presence of bla_OXA-48, bla_KPC, bla_NDM, and bla_VIM carbapenemase genes was examined by PCR, and clonal relatedness of CRKP isolates was investigated by pulsed-field gel electrophoresis (PFGE) analysis. bla_OXA-48 was the most frequent carbapenemase gene (72%), followed by bla_NDM (31%). None of the isolates harbored bla_KPC and bla_VIM genes. PFGE separated the majority of isolates into 10 clusters, including the major clusters A and B, carrying bla_OXA-48, and clusters C and D, carrying bla_NDM, and 4 isolates had a unique PFGE pattern. An increased rate of colistin resistance (50%) was detected among the isolates. Tigecycline was found to be the most active agent against CRKP isolates. Our results revealed that high prevalence of bla_OXA-48 and bla_NDM carbapenamses and resistance to colistin are alarming threats, necessitating an immediate action to prevent the spread of carbapenem-colistin-resistant K. pneumoniae isolates in Iran.

In vitro activity of tigecycline and comparators (2014-2016) among key WHO 'priority pathogens' and longitudinal assessment (2004-2016) of antimicrobial resistance: a report from the T.E.S.T. study

We report contemporary (2014-2016) Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) global data on activity of tigecycline and comparators against WHO 'priority pathogens', and global trends (2004-2016) in antimicrobial resistance. MICs were determined using CLSI broth microdilution methodology. Antimicrobial resistance was determined using CLSI breakpoints (FDA breakpoints for tigecycline). Data are reported for Africa, Asia, Europe, North America and South America. From 2014-2016, Africa, Asia and South America reported highest resistance rates among Acinetobacter baumannii; North America lowest (all antimicrobials tested). The tigecycline MIC₉₀ against A. baumannii was 2 mg/L in all regions except South America (1 mg/L). Among Enterobacteriaceae, meropenem resistance was low and tigecycline resistance was ≤1.3% in all regions (Escherichia coli, 0.0-0.3%; Klebsiella pneumoniae 0.0-1.3%; Enterobacter spp. 0.5-1.1%; Serratia marcescens 0.0-1.3%). Ceftriaxone resistance among E. coli ranged from 14.5% (North America) to 54.7% (Asia), and among K. pneumoniae from 9.1% (North America) to 54.0% (South America). North America reported highest rates of vancomycin-resistant Enterococcus faecium (64.6%); Europe lowest (17.7%). The tigecycline MIC₉₀ against methicillin-resistant Staphylococcus aureus (MRSA) ranged from 0.12 mg/L (Africa and North America) to 0.5 mg/L (Asia). From 2004-2016, carbapenem resistance increased among A. baumannii (all regions), reaching 92.3% in Africa and 85.7% in South America (2016). Rates of ceftriaxone-resistant E. coli increased in all regions except Asia. Ceftriaxone resistance in K. pneumoniae increased in Europe. Rates of vancomycin-resistant E. faecium and MRSA were highest in North America and South America (and Asia for MRSA); lowest in Europe.

KPC-producing Klebsiella pneumoniae bloodstream isolates from Brazilian hospitals: What (still) remains active?

OBJECTIVES

This study assessed susceptibility to polymyxin B (PMB) and alternative antimicrobials, with focus on aminoglycosides and tigecycline, according to different breakpoints in KPC-producing Klebsiella pneumoniae (KPC-Kp) bloodstream isolates from Brazilian hospitals.

METHODS

Bloodstream K. pneumoniae isolates non-susceptible to any of the three carbapenems (meropenem, imipenem or ertapenem) from four Brazilian tertiary-care hospitals were selected. Antimicrobial susceptibility was determined and interpreted according to distinct breakpoints. Twenty-nine PMB-resistant KPC-Kp isolates were selected for molecular typing.

RESULTS

A total of 158 KPC-Kp were analysed. MIC_50/90 values for PMB were 0.25/16mg/L; 40 isolates (25.3%) were resistant to PMB. MIC_50/90 values for meropenem were 32/≥256mg/L; no isolates were susceptible to meropenem according to CLSI, but 10 isolates were intermediate using EUCAST breakpoints (1, MIC=4mg/L; 9, MIC=8mg/L). MIC_50/90 values for tigecycline were 2/8mg/L; 53 (33.5%) and 94 (59.5%) isolates were susceptible according to EUCAST and FDA breakpoints, respectively. MIC_50/90 values were 32/≥64mg/L for amikacin and ≥16/≥16mg/L for gentamicin; 48 (30.4%), 28 (17.7%) and 16 (10.1%) were susceptible to amikacin according to CLSI, EUCAST and USCAST, respectively, but susceptibility rates to gentamicin were <7.0%. Eighteen distinct clonal profiles were identified among 29 PMB-resistant isolates by DNA macrorestriction. Most clones belonged to CC11.

CONCLUSION

Elevated rates of PMB-resistant KPC-Kp bloodstream infections were found in four Brazilian hospitals, mostly of polyclonal origin. Alternative antimicrobials with the highest in vitro activity were tigecycline and amikacin, although susceptibility rates significantly decreased using criteria with stricter breakpoints (e.g. EUCAST, USCAST).

Real-Life Evidence for Tedizolid Phosphate in the Treatment of Cellulitis and Wound Infections: A Case Series

Introduction

Tedizolid phosphate 200 mg, once daily for 6 days, has recently been approved for the treatment of patients with acute bacterial skin and skin structure infections (ABSSSIs) in several countries; however, clinical experience in real-life settings is currently limited. Here, we report on the use of tedizolid with an extended treatment duration for complex and severe ABSSSIs in real-world clinical settings.

Methods

Two patients with cellulitis and two patients with surgical site infection (SSI), aged 26–60 years, were treated with tedizolid phosphate 200 mg, intravenous/oral (IV/PO) or IV only, once daily at four different institutions.

Results

Two morbidly obese patients had non-necrotizing, non-purulent severe cellulitis, which were complicated by sepsis or systemic inflammatory response syndrome plus myositis. One female patient failed on first-line empiric therapy with IV cefalotin, clindamycin and imipenem (3–4 days), and was switched to IV/PO tedizolid (7 + 5 days). One male patient received IV clindamycin plus IV/PO tedizolid (5 + 5 days), but clindamycin was discontinued on Day 3 due to an adverse event. For both patients, clinical signs and symptoms improved within 72 h, and laboratory results were normalized by Days 7 and 8, respectively. Two other patients (one obese, diabetic female with chronic hepatitis and chronic obstructive pulmonary disease) had complicated SSIs occurring 10 days after hernia repair with mesh or 3 months after spinal fusion surgery with metal implant. First patient with previous methicillin-resistant Staphylococcus aureus (MRSA) bacteremia received a 7-day tedizolid IV course empirically. The second patient with culture-confirmed MRSA infection received a 14-day IV course. Both patients responded within 72 h, and local and systemic signs normalized by end of treatment. There were no reports of thrombocytopenia.

Conclusion

Tedizolid phosphate 200 mg for 7–14 days was a favored treatment option for patients with severe/complex ABSSSIs, and was effective following previous treatment failure or in late-onset infections.

Funding

Editorial assistance and the article processing charges were funded by Bayer AG, Berlin, Germany.

Carbapenemase-producing Enterobacteriaceae in Mexico: report of seven non-clonal cases in a pediatric hospital

Background

Carbapenemases-producing Enterobacteriaceae (CPE) are a worldwide public health emergency. In Mexico, reports of CPE are limited, particularly in the pediatric population. Here, we describe the clinical, epidemiological, and molecular characteristics of seven consecutive cases in a third-level pediatric hospital in Mexico City over a four-month period during 2016.

Results

The Enterobacteriaceae identified were three Escherichia coli strains (producing OXA-232, NDM-1 and KPC-2), two Klebsiella pneumoniae strains (producing KPC-2 and NDM-1), one Klebsiella oxytoca strain producing OXA-48 and one Enterobacter cloacae strain producing NDM-1. The majority of patients had underlying disesases, three were immunocompromised, and three had infections involved the skin and soft tissues. Half patients died as a result of CPE infection.

Conclusions

This study represents the first report of E. coli ST131-O25b clone producing NDM-1 in Latin America. In addition, this study is the first finding of K. oxytoca producing OXA-48 and E. coli producing OXA-232 in Mexican pediatric patients.

Frequency and Genetic Determinants of Tigecycline Resistance in Clinically Isolated Stenotrophomonas maltophilia in Beijing, China

Stenotrophomonas maltophilia is an emerging nosocomial pathogen with high resistance to most clinically used antimicrobials. Tigecycline is a potential alternative antimicrobial for S. maltophilia infection treatment, but its resistance mechanism in clinical isolates is not fully elucidated. We investigated the antimicrobial susceptibility of 450 S. maltophilia isolated during 2012–2015 from three university hospitals in Beijing, China. These strains exhibited high susceptibility to minocycline (98.44%), sulfamethoxazole/trimethoprim (87.56%), tigecycline (77.78 %), doxycycline (81.33%), levofloxacin (67.56%), and ticarcillin/clavulanate (73.00%). The susceptibility of tigecycline-nonsusceptible strains (TNS) to doxycycline and levofloxacin was much lower than that of tigecycline-susceptible strains (TSS) (25.00% vs. 97.71% for doxycycline, P < 0.001; 17.00% vs. 82.00% for levofloxacin, P < 0.001). We further selected 48 TNS and TSS and compared the detection rate of eight tetracycline-specific genes by PCR and the expression level of six intrinsic multidrug resistance efflux pumps by real-time PCR. Only one tetB and two tetH genes in TNS and three tetH genes in TSS were detected, and the detection rate had no difference. The average expression level of smeD in TNS was higher than that in TSS [20.59 (11.53, 112.54) vs. 2.07 (0.80, 4.96), P < 0.001], while the average expression levels of smeA, smeI, smeO, smeV, and smrA were not significantly different, indicating that smeDEF was the predominant resistance genetic determinant in clinical S. maltophilia. Higher smeD expression was also observed in levofloxacin- and doxycycline-nonsusceptible isolates than in their corresponding susceptible isolates [16.46 (5.83, 102.24) vs. 2.72 (0.80, 6.25) for doxycycline, P < 0.001; 19.69 (8.07, 115.10) vs. 3.01(1.00, 6.03), P < 0.001], indicating that smeDEF was also the resistance genetic determinant to levofloxacin and doxycycline. The consistent resistance profile and common resistance genetic determinant highlight the importance of rational use of tigecycline for preventing the occurrence and spread of multidrug resistance.

Emergence of Stenotrophomonas maltophilia nosocomial isolates in a Saudi children's hospital. Risk factors and clinical characteristics

Objectives:

To describe the clinical characteristics of pediatric patients colonized or infected by Stenotrophomonas maltophilia (S. maltophilia) at a Saudi children’s hospital, to identify risk factors associated with infection, and to investigate the antimicrobial resistance patterns of this emerging pathogen.

Methods:

In this cross-sectional observational study, 64 non-duplicating S. maltophilia strains were isolated in Najran Maternity and Children’s Hospital, Najran, Saudi Arabia between January 2015 to February 2016. Antimicrobial susceptibility testing was performed using the reference broth microdilution method.

Results:

In this study, 48 (75%) isolates were identified in true infections and 16 (25%) isolates were considered colonization. The main types of S. maltophilia infection were pneumonia in 22 (45.8%) patients and bloodstream infection in 14 (29.2%) patients. The significant risk factors included exposure to invasive procedure (p=0.02), and presence of acute leukemia as an underlying disease (p=0.02). The most active antimicrobials were trimethoprim/sulfamethoxazole (100% sensitivity) and tigecycline (93.7% sensitivity).

Conclusions:

Stenotrophomonas maltophilia is an emerging nosocomial pathogen among pediatric patients. Accurate identification and susceptibility testing of this emerging pathogen are crucial for the management of infected patients and prevention of spread of this nosocomial pathogen.

Global antimicrobial resistance in Gram-negative pathogens and clinical need

Resistance in Gram-negative bacteria has become a serious problem in many regions of the world as it may reduce the treatment options substantially. Carbapenem-resistance is a good marker for such situations and is most prevalent in Acinetobacter, Pseudomonas but also increasingly in Enterobacteriaceae, especially Klebsiella. This review gives a rough global picture highlighting the epicentres of resistance. The medical need for novel treatment options globally is undeniable even if many countries with good stewardship and infection control conditions are not highly affected. Antibiotic pipelines are encouraging, as new drugs in development reduce the resistance rate to individual pathogens. Despite some progress, efforts to discover and develop novel drugs that are not prone to cross-resistance to existing antibiotic classes should be intensified.

Impact of reduced tigecycline susceptibility on clinical outcomes of Acinetobacter bacteremia

The higher 14-day mortality rate for patients with Acinetobacter bacteremia receiving tigecycline appropriately compared to other appropriate antibiotics (36.4% versus 14.2%, P = 0.028) was due to the poor effect of tigecycline for isolates with a minimum inhibitory concentration of 2 μg/mL (63.6% of 11 versus 14.2% of 127, P = 0.001).

Susceptibility testing and reporting of new antibiotics with a focus on tedizolid: an international working group report

Inappropriate use and overuse of antibiotics are among the most important factors in resistance development, and effective antibiotic stewardship measures are needed to optimize outcomes. Selection of appropriate antimicrobials relies on accurate and timely antimicrobial susceptibility testing. However, the availability of clinical breakpoints and in vitro susceptibility testing often lags behind regulatory approval by several years for new antimicrobials. A Working Group of clinical/medical microbiologists from Brazil, Canada, Mexico, Saudi Arabia, Russia and the UK recently examined issues surrounding antimicrobial susceptibility testing for novel antibiotics. While commercially available tests are being developed, potential surrogate antibiotics may be used as marker of susceptibility. Using tedizolid as an example of a new antibiotic, this special report makes recommendations to optimize routine susceptibility reporting.

Antimicrobial susceptibility among Gram-positive and Gram-negative organisms collected from the Latin American region between 2004 and 2015 as part of the Tigecycline Evaluation and Surveillance Trial

BACKGROUND

The in vitro activity of tigecycline and comparator agents was evaluated against Gram-positive and Gram-negative isolates collected in Latin American centers between 2004 and 2015 as part of the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) global surveillance study.

METHODS

Minimum inhibitory concentrations (MICs) were determined using the broth microdilution methodology according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Antimicrobial susceptibility was determined using CLSI breakpoints, except for tigecycline for which the US Food and Drugs Administration breakpoints were used.

RESULTS

A total of 48.3% (2202/4563) of Staphylococcus aureus isolates were methicillin-resistant S. aureus (MRSA). All MRSA isolates were susceptible to linezolid and vancomycin, and 99.9% (2199/2202) were susceptible to tigecycline. Among Streptococcus pneumoniae isolates, 13.8% (198/1436) were penicillin-resistant; all were susceptible to linezolid and vancomycin, and 98.0% (194/198) were susceptible to tigecycline. Susceptibility was >99.0% for linezolid and tigecycline against Enterococcus faecium and Enterococcus faecalis isolates. A total of 40.8% (235/576) E. faecium and 1.6% (33/2004) E. faecalis isolates were vancomycin-resistant. Among the Enterobacteriaceae, 36.3% (1465/4032) of Klebsiella pneumoniae isolates, 16.4% (67/409) of Klebsiella oxytoca isolates and 25.4% (1246/4912) of Escherichia coli isolates were extended-spectrum β-lactamase (ESBL) producers. Of the ESBL-producing K. pneumoniae and E. coli isolates, susceptibility was highest to tigecycline [93.4% (1369/1465) and 99.8% (1244/1246), respectively] and meropenem [86.9% (1103/1270) and 97.0% (1070/1103), respectively]. A total of 26.7% (966/3613) of Pseudomonas aeruginosa isolates were multidrug-resistant (MDR). Among all P. aeruginosa isolates, susceptibility was highest to amikacin [72.8% (2632/3613)]. A total of 70.3% (1654/2354) of Acinetobacter baumannii isolates were MDR, and susceptibility was highest to minocycline [88.3% (2079/2354) for all isolates, 86.2% (1426/1654) for MDR isolates]. Tigecycline had the lowest MIC₉₀ (2 mg/L) among A. baumannii isolates, including MDR isolates.

CONCLUSIONS

This study of isolates from Latin America shows that linezolid, vancomycin and tigecycline continue to be active in vitro against important Gram-positive organisms such as MRSA, and that susceptibility rates to meropenem and tigecycline against members of the Enterobacteriaceae, including ESBL-producers, were high. However, we report that Latin America has high rates of MRSA, MDR A. baumannii and ESBL-producing Enterobacteriaceae which require continued monitoring.

Molecular and microbiological report of a hospital outbreak of NDM-1-carrying Enterobacteriaceae in Mexico

OBJECTIVES

To characterize the microbiological, molecular and epidemiological data of an outbreak of carbapenem-resistant Enterobacteriaceae (CRE) in a tertiary-care hospital in Mexico.

METHODS

From September 2014 to July 2015, all CRE clinical isolates recovered during an outbreak in the Hospital Civil "Fray Antonio Alcalde" in Jalisco, Mexico were screened for antimicrobial susceptibility, carbapenemase production, carbapenemase-encoding genes, and plasmid profiles. Horizontal transfer of imipenem resistance; and clonal diversity by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST); as well as biofilm production and the presence of 14 virulence genes were analyzed in selected isolates.

RESULTS

Fifty-two carbapenem-resistant isolates corresponding to 5 species were detected, i.e., Klebsiella pneumoniae (n = 46), Enterobacter cloacae (n = 3), Escherichia coli (n = 1), Providencia rettgeri (n = 1) and Citrobacter freundii (n = 1) with carbapenemase encoding genes blaNDM-1 (n = 48), blaVIM (n = 3), blaIMP (n = 1) and blaKPC (n = 1) detected in these isolates. The blaNDM-1 gene was detected in plasmids from 130- to 170-kb in K. pneumoniae (n = 46); E. cloacae (n = 3), E. coli (n = 1) and P. rettgeri (n = 1). The transfer of plasmids harboring the blaNDM-1 gene was obtained in eight transconjugants. One plasmid restriction pattern was detected, with the blaNDM-1 identified in different restriction fragments. Predominant clone A of K. pneumoniae isolates archived 28/46 (60%) isolates and belongs to ST392. Besides, ST307, ST309, ST846, ST2399, and ST2400 were detected for K. pneumoniae; as well as E. cloacae ST182 and E. coli ST10. The fimA and uge genes were more likely to be identified in K. pneumoniae carbapenem-susceptible isolates (p = <0.001) and biofilm production was more liable to be observed in carbapenem-resistant isolates (p = <0.05).

CONCLUSIONS

Four Enterobacteriaceae species harboring the blaNDM-1 gene were detected in a nosocomial outbreak in Mexico; horizontal transfer and strain transmission were demonstrated for the blaNDM-1 gene. Given the variation in the size of the plasmid harboring blaNDM-1, complex rearrangements must also be occurring.

Changed epidemiology during intra and interhospital spread of high-risk clones of vanA-containing Enterococcus in Brazilian hospitals

We report changes in the molecular epidemiology of vanA-containing Enterococcus during the intra and interhospital spread of high-risk clones, in Southeastern Brazil. While VRE faecalis predominated during 1998 to 2006, a reversal has been observed in the last years, where VRE faecium belonging to ST114, ST203, ST412, ST478 and ST858 have become endemic.

First Report of Group CTX-M-9 Extended Spectrum Beta-Lactamases in Escherichia coli Isolates from Pediatric Patients in Mexico

The aim of this study was to identify the presence of group CTX-M-9 extended spectrum beta-lactamases (ESBL) in clinical Escherichia coli isolates from pediatric patients. A total of 404 non-repeated positive ESBL E. coli isolates were collected from documented clinical infections in pediatric patients over a 2-year period. The identification and susceptibility profiles were determined using an automated system. Isolates that suggested ESBL production based on their resistance profiles to third and fourth generation cephalosporin and monobactam were selected. ESBL production was phenotypically confirmed using a diffusion method with cefotaxime and ceftazidime discs alone and in combination with clavulanic acid. blaESBL gene identification was performed through PCR amplification and sequencing. Pulsed Field Gel Electrophoresis (PFGE) and Multilocus Sequence Typing (MLST) were performed to establish the clonal relationships of the E. coli isolates. CTX-M-9-type ESBLs were detected in 2.5% of the isolates. The subtypes corresponded to blaCTX-M-14 (n = 4) and blaCTX-M-27 (n = 6). Additionally, coexistence with other beta-lactamases was observed. A clonal relationship was established in three isolates; the rest were classified as non-related. We found seven different sequence type (ST) in CTX-M-9- producing E. coli isolates. ST38 was the most frequent. This study is the first report in Mexico to document the presence of group CTX-M-9 ESBLs in E. coli isolates from pediatric patients.

The Antibiotic Drug Tigecycline: A Focus on its Promising Anticancer Properties

Tigecycline (TIG), the first member of glycylcycline bacteriostatic agents, has been approved to treat complicated infections in the clinic because of its expanded-spectrum antibiotic potential. Recently, an increasing number of studies have emphasized the anti-tumor effects of TIG. The inhibitory effects of TIG on cancer depend on several activating signaling pathways and abnormal mitochondrial function in cancer cells. The aim of this review is to summarize the cumulative anti-tumor evidence supporting TIG activity against different cancer types, including acute myeloid leukemia (AML), glioma, non-small cell lung cancer (NSCLC), among others. In addition, the efficacy and side effects of TIG in cancer patients are summarized in detail. Future clinical trials are also to be discussed that will evaluate the security and validate the underlying the tumor-killing properties of TIG.

Emerging Issues and Treatment Strategies in Carbapenem-Resistant Enterobacteriaceae (CRE)

Carbapenems are the broadest spectrum antimicrobials utilized in the treatment of serious infections since the 1980s. Soon after their introduction, the discovery of carbapenem-resistant Enterobacteriaceae (CRE) was reported in the 1990s. Invasive CRE infections are associated with high mortality and limited treatment options making care for patients with these infections challenging for clinicians. Current practice has reverted back to the use of "older" antimicrobials, such as the polymyxins, tigecycline, and fosfomycin, to combat invasive CRE infections. However, recent approval of ceftazidime-avibactam has added another treatment option to the current antimicrobial armamentarium. Resistance among the "older" agents is still rare but has been reported. Currently, there are numerous agents that are under investigation as well as combination therapy that looks promising in the treatment of CRE infections.