Association of two resistance mechanisms in a clinical isolate of Enterobacter cloacae with high-level resistance to imipenem.

An outbreak of mupirocin-resistant (MuR) staphylococci was investigated in two wards of a large hospital in Warsaw, Poland. Fifty-three MuR isolates of Staphylococcus aureus, S. epidermidis, S. haemolyticus, S. xylosus, and S. capitis were identified over a 17-month survey which was carried out after introduction of the drug for the treatment of skin infections. The isolates were collected from patients with infections, environmental samples, and carriers; they constituted 19.5% of all staphylococcal isolates identified in the two wards during that time. Almost all the MuR isolates were also resistant to methicillin (methicillin-resistant S. aureus and methicillin-resistant coagulase-negative staphylococci). Seven of the outbreak isolates expressed a low-level-resistance phenotype (MuL), whereas the remaining majority of isolates were found to be highly resistant to mupirocin (MuH). The mupA gene, responsible for the MuH phenotype, has been assigned to three different polymorphic loci among the strains in the collection analyzed. The predominant polymorph, polymorph I (characterized by a mupA-containingEcoRI DNA fragment of about 16 kb), was located on a specific plasmid which was widely distributed among the entire staphylococcal population. All MuR S. aureus isolates were found to represent a single epidemic strain, which was clonally disseminated in both wards. The S. epidermidis population was much more diverse; however, at least four clusters of closely related isolates were identified, which suggested that some strains of this species were also clonally spread in the hospital environment. Six isolates of S. epidermidis were demonstrated to express the MuL and MuH resistance mechanisms simultaneously, and this is the first identification of such dual MuR phenotype-bearing strains. The outbreak was attributed to a high level and inappropriate use of mupirocin, and as a result the dermatological formulation of the drug has been removed from the hospital formulary.

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Cefazolin and Imipenem Enhance AmpC Expression and Resistance in NagZ-Dependent Manner in Enterobacter Cloacae

10.21203/rs.3.rs-919621/v1 ◽

2021 ◽

Author(s):

Xianggui Yang ◽

Zhenguo Wang ◽

Xuejing Yu ◽

Yuanxiu Zhong ◽

Fuying Wang ◽

...

Keyword(s):

Clinical Isolate ◽

Target Genes ◽

Ectopic Expression ◽

Enterobacter Cloacae ◽

Opportunistic Pathogen ◽

Resistance Mechanisms ◽

Induction Effect ◽

Dependent Manner ◽

Critical Determinant ◽

2Nd Generation

Abstract Background: Enterobacter cloacae (EC) is a commonly occurring opportunistic pathogen and is responsible for causing various infections in humans. Owing to its inducible chromosomal AmpC β-lactamase (AmpC), EC is inherently resistant to the 1st- and 2nd- generation cephalosporins. However, whether β-lactams antibiotics enhance EC resistance remains unclear.Results: In this study, we found that subinhibitory concentrations (SICs) of cefazolin (CFZ) and imipenem (IMP) are able to advance the expression of AmpC and improve its resistance towards β - lactams through NagZ in EC clinical isolate. Our work indicate that AmpC manifested a substantial upregulation in EC in response to SICs of CFZ and IMP. In nagZ knockout EC (ΔnagZ), we found that the resistance to β - lactam antibiotics was rather weakened and the effect of CFZ and IMP on induction of AmpC was completely abrogated. Ectopic expression of NagZ can rescue the induction effect of CFZ and IMP on AmpC and enhance resistance in ΔnagZ. More importantly, CFZ and IMP have the potential to bring about the target genes expressions of AmpR in a NagZ-dependent manner.Conclusions: Our findings show that NagZ is a critical determinant for CFZ and IMP to promote AmpC expression and improve resistance and that CFZ and IMP should be used with caution since they may aggravate EC resistance. At the same time, this study further improves our understanding of resistance mechanisms in EC.

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Extended-Spectrum Cephalosporinase in Acinetobacter baumannii

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00050-10 ◽

2010 ◽

Vol 54 (8) ◽

pp. 3484-3488 ◽

Cited By ~ 46

Author(s):

José-Manuel Rodríguez-Martínez ◽

Patrice Nordmann ◽

Esthel Ronco ◽

Laurent Poirel

Keyword(s):

Acinetobacter Baumannii ◽

Clinical Isolate ◽

Site Directed Mutagenesis ◽

Directed Mutagenesis ◽

Extended Spectrum ◽

Class C ◽

High Level ◽

Level Resistance

ABSTRACT An AmpC-type β-lactamase conferring high-level resistance to expanded-spectrum cephalosporins and monobactams was characterized from an Acinetobacter baumannii clinical isolate. This class C β-lactamase (named ADC-33) possessed a Pro210Arg substitution together with a duplication of an Ala residue at position 215 (inside the Ω-loop) compared to a reference AmpC cephalosporinase from A. baumannii. ADC-33 hydrolyzed ceftazidime, cefepime, and aztreonam at high levels, which allows the classification of this enzyme as an extended-spectrum AmpC (ESAC). Site-directed mutagenesis confirmed the role of both substitutions in its ESAC property.

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First clinical isolate of Streptococcus pneumoniae exhibiting high-level resistance to fluoroquinolones in Taiwan

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/48.2.316 ◽

2001 ◽

Vol 48 (2) ◽

pp. 316-317 ◽

Cited By ~ 4

Author(s):

P.-R. Hsueh

Keyword(s):

Streptococcus Pneumoniae ◽

Clinical Isolate ◽

High Level ◽

Level Resistance

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A pneumococcal clinical isolate with high-level resistance to cefotaxime and ceftriaxone.

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.36.4.886 ◽

1992 ◽

Vol 36 (4) ◽

pp. 886-889 ◽

Cited By ~ 59

Author(s):

A M Figueiredo ◽

J D Connor ◽

A Severin ◽

M V Vaz Pato ◽

A Tomasz

Keyword(s):

Clinical Isolate ◽

High Level ◽

Level Resistance

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Plasmid-Mediated 16S rRNA Methylases in Aminoglycoside-Resistant Enterobacteriaceae Isolates in Shanghai, China

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00748-08 ◽

2008 ◽

Vol 53 (1) ◽

pp. 271-272 ◽

Cited By ~ 47

Author(s):

Qiong Wu ◽

Yibo Zhang ◽

Lizhong Han ◽

Jingyong Sun ◽

Yuxing Ni

Keyword(s):

Escherichia Coli ◽

16S Rrna ◽

Klebsiella Pneumoniae ◽

Gel Electrophoresis ◽

Enterobacter Cloacae ◽

Pulsed Field Gel Electrophoresis ◽

Pulsed Field ◽

High Level ◽

Level Resistance

ABSTRACT High-level resistance to aminoglycosides produced by 16S rRNA methylases in Enterobacteriaceae isolates was investigated. The prevalences of armA in Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae were 0.6%, 3.0%, and 10%, respectively. rmtB was more prevalent than armA. Pulsed-field gel electrophoresis patterns indicated that armA and rmtB have spread horizontally and clonally.

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Characterization of an Enterococcus gallinarum Isolate Carrying a DualvanAandvanBCassette

Journal of Clinical Microbiology ◽

10.1128/jcm.03267-14 ◽

2015 ◽

Vol 53 (7) ◽

pp. 2225-2229 ◽

Cited By ~ 8

Author(s):

Alireza Eshaghi ◽

Dea Shahinas ◽

Aimin Li ◽

Ruwandi Kariyawasam ◽

Philip Banh ◽

...

Keyword(s):

Clinical Isolate ◽

Resistance Mechanism ◽

Vancomycin Resistance ◽

Content Type ◽

Enterococcal Species ◽

Enterococcus Gallinarum ◽

High Level ◽

Identification And Characterization ◽

Level Resistance

The ability of vancomycin resistance determinants to be horizontally transferred within enterococci species is a concern. Identification and characterization of vancomycin-resistant enterococci (VRE) in a clinical isolate have a significant impact on infection control practices. In this study, we describe a clinical isolate ofEnterococcus gallinarumexhibiting high-level resistance to vancomycin and teicoplanin. The genetic characterization of this isolate showed the presence ofvanAandvanBgenes in addition to the naturally carriedvanCgene.vanAwas identified on pA6981, a 35,608-bp circular plasmid with significant homology to plasmid pS177. ThevanBoperon was integrated into the bacterial chromosome and showed a high level of homology to previously reported Tn1549and Tn5382. To the best of our knowledge, this is the first report ofE. gallinarumcarrying bothvanAandvanBoperons, indicating the importance of identifying the vancomycin resistance mechanism in non-E. faeciumand non-E. faecalisenterococcal species.

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1192. Identification of a Novel Enterobacter cloacae Isolate Producing an IMP-13 Metallo-β-Lactamase

Open Forum Infectious Diseases ◽

10.1093/ofid/ofy210.1025 ◽

2018 ◽

Vol 5 (suppl_1) ◽

pp. S360-S361

Author(s):

Muhammad Bilal Abid ◽

Blake Buchan ◽

Nathan Ledeboer ◽

L Silvia Munoz-Price ◽

Mary Beth Graham

Keyword(s):

Clinical Success ◽

Multidrug Resistant ◽

Resistance Mechanisms ◽

Stage Iiic ◽

Travel History ◽

Healthcare Settings ◽

High Level ◽

Culture Positive ◽

Broth Dilution ◽

Level Resistance

Abstract Background Metallo-β-lactamases (MBLs) have been identified as emerging resistance determinants in Enterobacteriaceae, A. baumanii, and P. aeruginosa. Early identification of carbapenemase-producing organisms (CPOs) is essential to prevent dissemination within healthcare settings. We report a case of a patient who was blood culture positive for a multidrug-resistant E. cloacae which was subsequently found to be positive for the MBL blaIMP-13. Methods A 74-year-old female, with no significant past medical or travel history, developed sepsis 2 days after undergoing debulking surgery for stage IIIc ovarian carcinoma. Blood cultures were positive for Gram-negative bacilli and the organisms identified as Enterobacter spp. with blaIMP MBL (Verigene). Antimicrobial susceptibility testing demonstrated high-level resistance to all penicillins, ureidopenicillins, cephalosporins, and β-lactam/inhibitor antibiotics, and susceptibility to colistin, tigecycline, and monobactams. Results Further testing using micro-broth dilution, BD phoenix, and Etest, demonstrated susceptible MICs to meropenem and imipenem, with intermediate to resistant MICs to ertapenem. The patient was treated with a combination therapy of amikacin, aztreonam, and ceftazidime-avibactam and responded clinically. Per standard protocol, the organism was sent to WI Laboratory of Hygiene for further characterization. Phenotypic testing using the modified carbapenem inactivation test (mCIM) was positive, indicating the presence of a carbapenemase; however, results using Xpert CarbaR (Cepheid) were negative. Subsequent sequencing of the isolate confirmed the presence of blaIMP-13. Conclusion This was an important case for several reasons. First, blaIMP-13 is historically reported in Pseudomonas aeruginosa. Indeed, this was the first report of Enterobacteriaceae harboring blaIMP in WI. Second, it had unique susceptibility pattern to carbapenems and was not detected by the CarbaR. Third, these data demonstrate clinical success in treating an MBL CPO with a combination anti-microbial regimen, based on an understanding of resistance mechanisms involved. This report calls for more vigilant screening for CPO using both phenotypic and genotypic methods. Disclosures N. Ledeboer, Luminex: Consultant, Consulting fee.

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Genetic determinants facilitating the evolution of resistance to carbapenem antibiotics

10.1101/2021.02.11.430761 ◽

2021 ◽

Author(s):

Peijun Ma ◽

Lorrie L. He ◽

Alejandro Pironti ◽

Hannah H. Laibinis ◽

Christoph M. Ernst ◽

...

Keyword(s):

Clinical Isolate ◽

Insertional Mutagenesis ◽

Carbapenem Resistance ◽

Genetic Determinants ◽

Stepping Stones ◽

Resistant Species ◽

Carbapenem Resistant ◽

Evolution Of Resistance ◽

High Level ◽

Level Resistance

AbstractIn this era of rising antibiotic resistance, in contrast to our increasing understanding of mechanisms that cause resistance, our understanding of mechanisms that influence the propensity to evolve resistance remains limited. Here, we identified genetic factors that facilitate the evolution of resistance to carbapenems, the antibiotic of “last resort,” inKlebsiella pneumoniae, the major carbapenem resistant species. In clinical isolates, we found that high-level transposon insertional mutagenesis plays an important role in contributing to high-level resistance frequencies in several major and emerging carbapenem-resistant lineages. A broader spectrum of resistance-conferring mutations for select carbapenems such as ertapenem also enables higher resistance frequencies and importantly, creates stepping-stones to achieve high-level resistance to all carbapenems. These mutational mechanisms can contribute to the evolution of resistance, in conjunction with the loss of systems that restrict horizontal resistance gene uptake, such as the CRISPR-Cas system. Given the need for greater antibiotic stewardship, these findings argue that in addition to considering the current efficacy of an antibiotic for a clinical isolate in antibiotic selection, considerations of future efficacy are also important. The genetic background of a clinical isolate and the exact antibiotic identity can and should also be considered as it is a determinant of a strain’s propensity to become resistant. Together, these findings thus provide a molecular framework for understanding acquisition of carbapenem resistance inK. pneumoniaewith important implications for diagnosing and treating this important class of pathogens.

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Prevalence and molecular characterization of methicillin-resistant Staphylococcus aureus with mupirocin, fusidic acid and/or retapamulin resistance

10.21203/rs.2.21815/v1 ◽

2020 ◽

Author(s):

Wenjing Chen ◽

Chunyan He ◽

Han Yang ◽

Wen Shu ◽

Zelin Cui ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Fusidic Acid ◽

Resistance Mechanisms ◽

Antibiotics Resistance ◽

Genetic Characteristics ◽

Methicillin Resistant ◽

Low Level ◽

High Level ◽

Level Resistance

Abstract Data on the prevalence of resistance to mupirocin (MUP), fusidic acid (FA) and retapamulin (RET) in methicillin-resistant Staphylococcus aureus (MRSA) from China are still limited. In this study we examined these three antibiotics resistance pheno and geno-typically in 1206 MRSA clinical isolates. Phenotypic MUP, FA and RET resistance was determined by MICs, and genotypically by PCR and DNA sequencing examining genes mupA / B , fusB - D , cfr and vgaA / Av , and mutations in ileS , fusA / E , rplC , and 23S RNA V domain. The genetic characteristics of resistance isolates were conducted by PFGE and MLST. Overall MRSA MUP, FA and RET resistance was low (5.1%, 1.0% and 0.3%, respectively). The mupA was the mechanism of high-level MUP resistance. All low-level MUP resistance isolates possessed an equivocal mutation N213D in IleS, and 2 of them additionally had the reported V588F mutation impacting the Rossman fold. FusA mutations, such as L461K, H457Q, H457Y and V90I, were the primary FA resistance mechanisms among high-level resistance isolates, most of which contained fusC ; however, all low-level resistance strains carried fusB . No resistance mechanisms detected were found among RET resistance isolates. Genetic analysis demonstrated clone spread for MUP resistance isolates. In conclusion, MUP, FA and RET exhibited highly activity against MRSA isolates. Acquired genes and chromosome-borne genes mutations were responsible for MUP and FA resistance, and further investigation is needed to uncover the RET resistance mechanisms. Moreover, the surveillance to MUP in MRSA should be strengthened to prevent resistance increase due to the expansion of clones.

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