In Silico Typing and Comparative Genomic Analysis of IncFIIK Plasmids and Insights into the Evolution of Replicons, Plasmid Backbones, and Resistance Determinant Profiles.

IncFIIK plasmids are associated with the acquisition and dissemination of multiple-antimicrobial resistance in Klebsiella pneumoniae and often encountered in clinical isolates of this species. Since the phylogeny and evolution of IncFIIK plasmids remain unclear, here we performed large-scale in silico typing and comparative analysis of these plasmids in publicly available bacterial/plasmid genomes. IncFIIK plasmids are prevalent in K. pneumoniae, being found in 69% of sequenced genomes, covering 66% of sequenced STs (sequence types), but sparse in other Enterobacteriaceae IncFIIK replicons have three lineages. One IncFIIK allele could be found in distinct K. pneumoniae STs, highlighting the lateral genetic flow of IncFIIK plasmids. A set of 77 IncFIIK plasmids with full sequences were further analyzed. A pool of 327 antibiotic resistance genes or remnants were annotated in 75.3% of these plasmids. Plasmid genome comparison reiterated that they often contain other replicons belonging to IncFIA, IncFIB, IncFIIYp, IncFIIpCRY, IncR, IncL, and IncN groups and that they share a conserved backbone featuring an F-like conjugation module that has divergent components responsible for regulation and mating pair stabilization. Further epidemiological studies of IncFIIK plasmids are required due to the sample bias of K. pneumoniae genomes in public databases. This study provides insights into the evolution and structures of IncFIIK plasmids.

Complete Sequence of a Novel IncR-F33:A-:B- Plasmid, pKP1034, Harboring fosA3, blaKPC-2, blaCTX-M-65, blaSHV-12, and rmtB from an Epidemic Klebsiella pneumoniae Sequence Type 11 Strain in China.

A high fosfomycin resistance rate was observed in Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) in our previous study, but little is known about its mechanisms. In this study, we explored the prevalence of plasmid-mediated fosfomycin resistance determinants among fosfomycin-resistant KPC-KP strains from a Chinese university hospital and determined the complete sequence of a novel fosA3-carrying plasmid isolated from an epidemic K. pneumoniae sequence type (ST) 11 strain. A total of 97 KPC-KP strains were studied, of which 57 (58.8%) were resistant to fosfomycin, including 44 (45.4%) harboring fosA3 and 1 harboring fosA. All fosA3-positive strains belonged to the dominant ST11-pulse type (PT) A clone according to multilocus sequence typing and pulsed-field gel electrophoresis, suggesting clonal dissemination. The fosA-positive isolate belonged to ST11-PTE. The fosA3-carrying plasmid pKP1034 is 136,848 bp in length and is not self-transmissible. It is a multireplicon plasmid belonging to IncR-F33:A-: B-. Besides fosA3, a variety of other resistance determinants, including blaKPC-2, rmtB, blaCTX-M-65, and blaSHV-12, are identified in pKP1034, which would allow for coselection of fosA3 by most ß-lactams and/or aminoglycosides and facilitate its dissemination despite limited use of fosfomycin in China. Detailed comparisons with related plasmids revealed that pKP1034 is highly mosaic and might have evolved from alarming recombination of the blaKPC-2-carrying plasmid pKPC-LK30 from Taiwan and the epidemic fosA3-carrying plasmid pHN7A8 from mainland China.

Mapping the resistance-associated mobilome of a carbapenem-resistant Klebsiella pneumoniae strain reveals insights into factors shaping these regions and facilitates generation of a 'resistance-disarmed' model organism.

OBJECTIVES: This study aims to investigate the landscape of the mobile genome, with a focus on antibiotic resistance-associated factors in carbapenem-resistant Klebsiella pneumoniae. METHODS: The mobile genome of the completely sequenced K. pneumoniae HS11286 strain (an ST11, carbapenem-resistant, near-pan-resistant, clinical isolate) was annotated in fine detail. The identified mobile genetic elements were mapped to the genetic contexts of resistance genes. The blaKPC-2 gene and a 26 kb region containing 12 clustered antibiotic resistance genes and one biocide resistance gene were deleted, and the MICs were determined again to ensure that antibiotic resistance had been lost. RESULTS: HS11286 contains six plasmids, 49 ISs, nine transposons, two separate In2-related integron remnants, two integrative and conjugative elements (ICEs) and seven prophages. Sixteen plasmid-borne resistance genes were identified, 14 of which were found to be directly associated with Tn1721-, Tn3-, Tn5393-, In2-, ISCR2- and ISCR3-derived elements. IS26 appears to have actively moulded several of these genetic regions. The deletion of blaKPC-2, followed by the deletion of a 26 kb region containing 12 clustered antibiotic resistance genes, progressively decreased the spectrum and level of resistance exhibited by the resultant mutant strains. CONCLUSIONS: This study has reiterated the role of plasmids as bearers of the vast majority of resistance genes in this species and has provided valuable insights into the vital role played by ISs, transposons and integrons in shaping the resistance-coding regions in this important strain. The 'resistance-disarmed' K. pneumoniae ST11 strain generated in this study will offer a more benign and readily genetically modifiable model organism for future extensive functional studies.

Mechanisms of tigecycline resistance among Klebsiella pneumoniae clinical isolates.

Of 26 tigecycline-nonsusceptible Klebsiella pneumoniae (TNSKP) clinical isolates, 25 had nonsynonymous mutations in ramR and/or acrR (23 in ramR and 10 in acrR). Eight TNSKP isolates possessed overexpression of ramA, acrB, rarA, and oqxB simultaneously, while 8 and 1 TNSKP strains had upregulation of ramA and acrB and of rarA and oqxB, respectively. Thus, resistance mechanisms of 9 TNSKP isolates cannot be explained by the present pathways. This study underscores the role of RamA in TNSKP and suggests the presence of novel tigecycline resistance mechanisms.

Molecular epidemiology and mechanisms of tigecycline resistance in clinical isolates of Acinetobacter baumannii from a Chinese university hospital.

Because of its remarkable ability to acquire antibiotic resistance and to survive in nosocomial environments, Acinetobacter baumannii has become a significant nosocomial infectious agent worldwide. Tigecycline is one of the few therapeutic options for treating infections caused by A. baumannii isolates. However, tigecycline resistance has increasingly been reported. Our aim was to assess the prevalence and characteristics of efflux-based tigecycline resistance in clinical isolates of A. baumannii collected from a hospital in China. A total of 74 A. baumannii isolates, including 64 tigecycline-nonsusceptible A. baumannii (TNAB) and 10 tigecycline-susceptible A. baumannii (TSAB) isolates, were analyzed. The majority of them were determined to be positive for adeABC, adeRS, adeIJK, and abeM, while the adeE gene was found in only one TSAB isolate. Compared with the levels in TSAB isolates, the mean expression levels of adeB, adeJ, adeG, and abeM in TNAB isolates were observed to increase 29-, 3-, 0.7-, and 1-fold, respectively. The efflux pump inhibitors (EPIs) phenyl-arginine-ß-naphthylamide (PAßN) and carbonyl cyanide 3-chlorophenylhydrazone (CCCP) could partially reverse the resistance pattern of tigecycline. Moreover, the tetX1 gene was detected in 12 (18.8%) TNAB isolates. To our knowledge, this is the first report of the tetX1 gene being detected in A. baumannii isolates. ST208 and ST191, which both clustered into clonal complex 92 (CC92), were the predominant sequence types (STs). This study showed that the active efflux pump AdeABC appeared to play important roles in the tigecycline resistance of A. baumannii. The dissemination of TNAB isolates in our hospital is attributable mainly to the spread of CC92.

Utility of fluorodeoxyglucose positron emission tomography/computed tomography in patients with fever of unknown origin diagnosed as lymphoma.

OBJECTIVE: To assess the efficacy of fluorine-18 fluorodeoxyglucose positron emission tomography ((18)F-FDG PET)/computed tomography (CT) in the diagnosis of patients with fever of unknown origin (FUO), who were finally diagnosed as lymphoma. SUBJECTS AND METHODS: A retrospective study was performed in the First Affiliated Hospital, School of Medicine of Zhejiang University, China, from March 2009 to March 2012. The PET/CT images of consecutive patients with FUO were analyzed. Within 1 week of PET/CT scanning, additional histological tests were also performed if clinically needed. RESULTS: A total of 73 consecutive patients were included. Of these, 34 (47%) had a PET/CT finding suggestive of the presence of lymphoma and 29 (85%) had a diagnosis of confirmed lymphoma; 39 (53%) had a PET/CT result revealing the absence of lymphoma and 4 (10%) were diagnosed by biopsy as having lymphoma, . The most frequent lymphoma diagnosis was peripheral T cell lymphoma (n = 16; 55%), followed by diffuse large B cell lymphoma (n = 9; 31%). The accuracy of PET/CT was 88%. CONCLUSION: In this study, PET/CT had high diagnostic accuracy in patients with FUO resulting from lymphoma, which indicated that PET/CT scanning was a valuable diagnostic tool for these groups of patients with FUO.

Severe pentastomiasis in children: a report of 2 cases.

Pentastomiasis is a type of parasitic zoonosis. Most patients with pentastomiasis are asymptomatic. We report here two pediatric patients with severe pentastomiasis (porocephaliais taiwan and armilliferiasis), and the results of their 6-year and 3-year follow-ups, respectively. The manifestations and outcomes of the two cases are described. The diagnoses were established by histopathologic and/or parasitologic examinations. After diagnosis, traditional Chinese medicine (TCM), as well as praziquantel and/or albendazole, were used for treatment. This report highlights the seriousness of pentastomiasis in children. We suggest TCM be considered as supplementary or even primary treatment of children with severe pentastomiasis.

Epidemic of Klebsiella pneumoniae ST11 clone coproducing KPC-2 and 16S rRNA methylase RmtB in a Chinese University Hospital.

BACKGROUND: Emergence of rmtB-positive Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) poses a great threat to antimicrobial treatment options. METHODS: From January 2010 to December 2010, non-duplicate KPC-KP isolates from our hospital were screened for rmtB and multiple other resistance determinants with PCR. Subsequent studies included MIC determination, PFGE, and multilocus sequence typing. Records from patients with KPC-KP isolated were retrospectively reviewed. Comparisons of molecular and clinical characteristics between rmtB-positive and rmtB-negative isolates were systematically performed, as well as the environmental colonization study in ICU wards. RESULTS: A total of 84 KPC-KP strains were collected, including 48 rmtB-positive KPC-KP (RPKP) and 36 rmtB-negative KPC-KP (RNKP) isolates. All KPC-KP isolates were multidrug resistant, with colistin and tigecycline being the most active agents. Compared with RNKP, RPKP displayed a much severer resistance phenotype. Susceptibility rates for amikacin (0% for RPKP versus 88.9% for RNKP, p < 0.01), fosfomycin (8.5% for RPKP versus 88.9% for RNKP, p < 0.01), and minocycline (6.7% for RPKP versus 52.8% for RNKP, p < 0.01), were all significantly lower in RPKP strains. Isolates belonging to PFGE pulsetype A and sequence type 11 were predominant in both groups, including 39 (81.3%) RPKP and 22 (61.1%) RNKP isolates. Nevertheless, RNKP showed more complex genetic backgrounds compared with RPKP. Diverse clinical characteristics were found in both cohorts, however, no significant differences were observed between RPKP and RNKP patients. CONCLUSIONS: RPKP strains have spread widely and gradually replaced RNKP in our hospital. They seemed to show much severer resistance phenotypes compared with RNKP and had a bigger dissemination potential. Prudent use of available active agents combined with good control practices is therefore mandatory.

Acute brucellosis with myelodysplastic syndrome presenting as pancytopenia and Fever of unknown origin.

OBJECTIVE: To report a rare case of brucellosis with myelo-dysplastic syndrome (MDS). CLINICAL PRESENTATION AND INTERVENTION: A 70-year-old woman presented with pancytopenia and fever of unknown origin (FUO). The initial diagnosis was brucellosis; the woman was treated with doxycycline and rifampin against Brucella melitensis but was later diagnosed as suffering from MDS. She was immediately transferred to the Department of Hematology for further evaluation. CONCLUSION: This study highlights the rarity of brucellosis with MDS, and we recommend that brucellosis with MDS be considered in patients presenting with pancytopenia and FUO.

Novel action of 3,4-DAA ameliorating acute liver allograft injury.

The anti-allergic drug, N-(3,4-dimethoxycinnamonyl) anthranilic acid (3,4-DAA), is a synthetic anthranilic acid derivative that has been used therapeutically in Japan for many years. In this study, to investigate the effects of 3,4-DAA in allograft immunorejection model, liver orthotopic transplants were performed using inbred male Dark Agouti donors and Lewis rat recipients (allografts). The levels of indoleamine 2,3-dioxygenases (IDO) enzymic activities in five groups, allografts (control), dimethyl sulphoxide-treated group (vehicle control), 200 mg·kg(-1) ·day(-1) of 3,4-DAA-treated group and 200 mg·kg(-1) ·day(-1) of 3,4-DAA + 5 mg·ml(-1) of 1-methyl-D-tryptophan (1-MT)-treated group were confirmed by determination of L-kynurenine (L-Kyn) concentrations. The serum alanine aminotransferase levels in 3,4-DAA-treated rats significantly decreased compared with those in mock and control group, whereas treatment of 1-MT in allografts led to the opposite effect. Administration of 3,4-DAA reduced histological severity of allograft immunorejection, decreased serum levels of cytokines tumour necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ), and raised serum levels of interleukin-10 (IL-10), suggesting that 3,4-DAA has both anti-inflammatory and anti-immunorejection properties through IDO in immune regulation and may therefore be useful in filling an unmet need, in the treatment of allograft immunorejection.

Efflux pumps AcrAB and OqxAB contribute to nitrofurantoin resistance in an uropathogenic Klebsiella pneumoniae isolate.

Klebsiella pneumoniae is a common cause of urinary tract infections (UTIs). Nitrofurantoin (NIT), with high therapeutic concentrations in urine, is recommended as the first-line drug for both empiric treatment and chemoprophylaxis of UTIs. Although NIT resistance in K. pneumoniae is relatively high, the resistance mechanism is not well understood. This study collected a NIT-resistant K. pneumoniae [NRKP, minimum inhibitory concentration (MIC)=128 mg/L] and investigated the resistance mechanism. Addition of efflux pump inhibitors increased the susceptibility of NRKP to NIT (MIC decreased from 128 to 32 mg/L), implying the important role of efflux pumps in NIT resistance. Quantitative reverse transcriptase polymerase chain reaction analysis showed that NRKP had >100-fold increased expression of ramA, which was demonstrated to be caused by ramR mutation. Deletion of ramA led to a four-fold decrease in the MIC of NIT, and the expression levels of efflux pumps acrB and oqxB were downregulated by four- to seven-fold. Complementation of ramA restored both the MIC value and the expression level of acrB and oqxB in the ramA mutant strain. In order to confirm the role of acrB and oqxB in NIT resistance, gene knockout strains were constructed. Deletion of acrB or oqxB alone led to a four-fold decrease in the MIC of NIT, and deletion of acrB and oqxB simultaneously led to a 16-fold decrease in the MIC of NIT. These results demonstrate that AcrAB and OqxAB contribute to NIT resistance in K. pneumoniae.

Serotype Distribution, Antimicrobial Susceptibility, and Multilocus Sequencing Type (MLST) of Streptococcus pneumoniae From Adults of Three Hospitals in Shanghai, China.

Background:Streptococcus pneumoniae, a main causative agent associated with invasive and non-invasive infection in elderly population, is a major global health problem. After pneumococcal conjugate vaccines (PCV) and pneumococcal polysaccharide vaccines (PPV) were introduced, the distribution of S. pneumoniae serotypes has changed. There was currently limited data on epidemiology and status of antimicrobial resistance of S. pneumoniae in Shanghai. Objective: To determine the serotype distribution, antimicrobial susceptibility and molecular epidemiology of S. pneumoniae isolated from adults in Shanghai. Method: A total of 75 S. pneumoniae isolates consecutively collected from 2015 through 2017 were serotyped by conventional multiplex-PCR. The antimicrobial susceptibility was determined by broth microdilution method. The multilocus sequence type (MLST) was performed to estimate the molecular epidemiology. Results: The predominant serotypes among the isolates were 19F (20.00%), 3 (16.00%), 23F (9.33%), 14 (8.00%), and19A (5.33%). The prevalence of pneumococcal strains with serotypes targeted by vaccines PCV7, PCV10, PCV13, and PPV23 was 44, 45.33, 66.67, and 80%, respectively. Penicillin non-susceptible S. pneumoniae (PNSSP) accounted for 16% of the isolates examined and resistance to erythromycin, azithromycin, tetracycline, clindamycin, cefaclor and trimethoprim-sulfamethoxazole were found in 92.00, 90.67, 86.67, 81.33, 54.67, and 54.67% of isolates, with most isolates (78.67%) presenting multidrug-resistance. The top three sequence types (STs) were ST271 (17.33%), ST180 (9.33%), and ST81 (8.00%). The international resistance clone complexes Spain23F-1 (n = 4), Netherland3-31 (n = 8), and Taiwan19F-14 (n = 14) were identified. Conclusions: The S. pneumoniae isolates showed high genetic diversity in Shanghai and the prevalence of antimicrobial resistance was also high among S. pneumoniae isolates, most of which were multidrug-resistant. The spread of international resistance clones might contribute to the increase of resistant isolates. The PPV23 could protect against most pneumococcal capsular serotypes causing infection of adults in Shanghai.

Emergence of tigecycline- and carbapenem-nonsusceptible Klebsiella pneumoniae ST11 clone in patients without exposure to tigecycline.

BACKGROUND/PURPOSE: Currently, tigecycline-nonsusceptible Klebsiella pneumoniae (TNSKP) is mainly reported to emerge following clinical use of tigecycline and is usually polyclonal. This study aimed to characterize TNSKP isolated from patients without prior tigecycline use. METHODS: Twenty-six TNSKP clinical isolates were collected, and carbapenemase and 16S rRNA methylase genes were identified by polymerase chain reaction and sequencing. Molecular typing was conducted by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Clinical data of patients in the carbapenem-susceptible TNSKP group and the tigecycline- and carbapenem-nonsusceptible K. pneumoniae (TCNSKP) group were compared. RESULTS: Of the 26 TNSKP isolates, eight contained both blaKPC-2 and 16S rRNA methylase genes. In the remaining 18 TNSKP isolates, no carbapenemase gene was detected, and only three had the 16S rRNA methylase gene. Among the 26 isolates, 24 distinct pulsotypes and 19 sequence types (STs) were identified by PFGE and MLST, respectively. Six of the eight TCNSKP were ST11, whereas the remaining 18 TNSKP isolates were assigned to 17 different STs. No patient received tigecycline prior to the isolation of TNSKP. By comparison, intensive care unit exposure, mechanical ventilation, prior ß-lactam/ß-lactamase use, and longer hospitalization were more common for the TCNSKP group than for the carbapenem-susceptible TNSKP group. CONCLUSION: TNSKP can occur without tigecycline use, and TCNSKP ST11 is predominant among them. Further, this report proposes potential risk factors for the occurrence of carbapenem-nonsusceptibility in TNSKP.

High-level tetracycline resistance mediated by efflux pumps Tet(A) and Tet(A)-1 with two start codons.

Efflux is the most common mechanism of tetracycline resistance. Class A tetracycline efflux pumps, which often have high prevalence in Enterobacteriaceae, are encoded by tet(A) and tet(A)-1 genes. These genes have two potential start codons, GTG and ATG, located upstream of the genes. The purpose of this study was to determine the start codon(s) of the class A tetracycline resistance (tet) determinants tet(A) and tet(A)-1, and the tetracycline resistance level they mediated. Conjugation, transformation and cloning experiments were performed and the genetic environment of tet(A)-1 was analysed. The start codons in class A tet determinants were investigated by site-directed mutagenesis of ATG and GTG, the putative translation initiation codons. High-level tetracycline resistance was transferred from the clinical strain of Klebsiella pneumoniae 10-148 containing tet(A)-1 plasmid pHS27 to Escherichia coli J53 by conjugation. The transformants harbouring recombinant plasmids that carried tet(A) or tet(A)-1 exhibited tetracycline MICs of 256-512 µg ml(-1), with or without tetR(A). Once the ATG was mutated to a non-start codon, the tetracycline MICs were not changed, while the tetracycline MICs decreased from 512 to 64 µg ml(-1) following GTG mutation, and to ≤4 µg ml(-1) following mutation of both GTG and ATG. It was presumed that class A tet determinants had two start codons, which are the primary start codon GTG and secondary start codon ATG. Accordingly, two putative promoters were predicted. In conclusion, class A tet determinants can confer high-level tetracycline resistance and have two start codons.

Regional prevalence and transmission route of Kaposi's sarcoma-associated herpes virus in Zhejiang, China.

BACKGROUND: The infection of Kaposi's sarcoma-associated herpes virus (KSHV) is most likely the cause of clinical Kaposi's sarcoma, primary effusion lymphoma, and multi-center Castleman's disease. KSHV infection has very limited epidemiological survey data in China, and its definite mode of transmission remains controversial. This study aimed to determine the infection status and the main transmission route of KSHV in Chinese population. METHODS: An enzyme-linked immunosorbent assay (ELISA) utilizing KSHV ORF65 recombinant protein was employed to analyze the antibody response to KSHV ORF65 in sera from 122 healthy physical examination people, 107 intravenous drug users, 135 non-intravenous drug users, 211 hepatitis B (HBV) patients infected via blood transmission, 107 kidney transplant recipients, and 72 female sex workers in Zhejiang Province in Southeast China. RESULTS: KSHV infection occurred relatively common (13.1%) in healthy population in Zhejiang, China. Infection rate was 16.7% in female sex workers, but significantly elevated in intravenous drug addicts (58.9%), blood-transmitted HBV patients (28.0%) and kidney transplant patients (41.1%). CONCLUSION: Blood borne transmission of KSHV is probably the main route of infection in Zhejiang Province.

Elevated uptake of 18F-FDG in PET/CT imaging of a nocardial pleural nodule.

18-Fluoredeoxyglucose position emission tomography and computed tomography ((18)F-FDG PET/CT) scanning has been widely used in the assessment of malignancy. We report here an increased (18)F-FDG uptake in pleural nodules in the PET/CT scan images of a patient having recurrent fever and chest pain. Further studies with bacterial culture and histopathology of biopsy confirmed the lesions as nocardial infection. To our knowledge, it is the first report of PET /CT findings in pleural multiple irregular nodules with nocardial infection. Our study suggests that a combination of FDG-PET/CT scanning and pathological study may be considered in distinguishing uncommon benign lesions in the lung.

Diagnostic value of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography in patients with fever of unknown origin.

BACKGROUND: While fever of unknown origin (FUO) remains a challenging problem in clinical practice, fluorine-18 fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) has been considered helpful in diagnosing its cause. The present study is set to evaluate the diagnostic value of PET/CT for patients with FUO. METHODS: We analyzed the records of 48 patients with FUO (34 men and 14 women; mean age of 57-year-old with a range between 24- and 82-year-old). The patients were examined by (18)F-FDG PET/CT and the results were compared to a final diagnosis that was established by additional procedures. RESULTS: A final diagnosis was established for 36 patients (75%). Among them, 15 patients had infectious diseases, 12 patients had malignancies, and 9 patients had non-infectious inflammatory diseases. Thirty-two abnormal PET/CT results correctly revealed the source of fever (true-positives). Abnormal PET/CT results were considered false-positives for 8 patients without diagnoses. Normal PET/CT results in 4 patients with no diagnoses were classified as true-negatives. Four patients with normal PET/CT results with diagnosed cause for FUO were considered false-negatives. Therefore, PET/CT had a positive predictive value of 80%, a negative predictive value of 50%, a sensitivity of 89%, and a specificity of 33% in patients with FUO. CONCLUSIONS: Our study demonstrated that FDG-PET/CT is a valuable imaging tool for the identification of the etiology in patients with FUO. The results suggest that this procedure may be considered as a second-line test, especially when conventional structural imaging was normal or unable to distinguish lesions from benign and malignant.

Emergence of Klebsiella pneumoniae carbapenemase-producing Proteus mirabilis in Hangzhou, China.

BACKGROUND: Carbapenems are used to treat severe infections caused by multi-drug-resistant organisms, however, the emergence of carbapenem-resistant bacterial isolates is becoming an increasing therapeutic challenge. Since the first Klebsiella (K.) pneumoniae carbapenemase (KPC)-producing K. pneumoniae was reported in 2001, KPC-producing isolates have been found increasingly, specially in Enterobacteriaceae. The aim of this study was to characterize the mechanisms of a carbapenem-resistant Proteus (P.) mirabilis. METHODS: A carbapenem-resistant P. mirabilis isolate was recovered from pleural drainage fluid of a patient admitted to surgical intensive care unit. Antimicrobial susceptibility testing of the isolate was performed by disk diffusion according to Clinical and Laboratory Standards Institute guidelines, and subsequent minimal inhibitory concentrations were determined with the E-test. Amplification of the bla(KPC) gene generated a positive band and the PCR products were sequenced subsequently. The plasmid of the isolate was extracted and was successfully transformed into Escherichia (E.) coli DH5α. RESULTS: The P. mirabilis isolate was resistant to all detected antimicrobial agents except tigecycline. KPC-2 was confirmed by DNA sequence analysis. The transformant E. coli was resistant to carbapenems. Further study demonstrated that upstream and downstream regions of bla(KPC-2) were identical to that observed in K. pneumoniae submitted to GenBank from China in 2007. CONCLUSION: Carbapenem resistance in the P. mirabilis isolate in this study is mainly due to production of KPC-2.