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Objective:To explore the resistance of common clinical isolates to chlorhexidine gluconate (CHG) and the clinical characteristics of patients with the infections.Methods:A total of 1 000 isolates from the First Affiliated Hospital of Wenzhou Medical University in 2018 (from January to May) were collected, which included 200 strains each of Escherichia coli ( E. coli), Acinetobacter baumanii ( A. baumanii), Pseudomonas aeruginosa ( P. aeruginosa), Staphylococcus aureus ( S. aureus), and Enterococcus spp.. Minimum inhibitory concentration (MIC) of CHG against 1 000 isolates were determined by the agar dilution method. The correlation between the resistance of isolates and clinical characteristics of infected patients was analyzed. Chi-square test or Fisher exact probability test were used for statistical analysis. Results:A total of 57 CHG resistant strains were detected in 1 000 clinical isolates. These CHG-resistant strains were mainly isolated from sputum and intensive care unit ward, accounting for 49.1%(28/57)and 38.6%(22/57), respectively. The resistance rates of P. aeruginosa, A. baumanii, Enterococcus spp., S. aureus, and E. coli to CHG were 16.0%(32/200), 7.0%(14/200), 3.0%(6/200), 1.5%(3/200) and 1.0%(2/200), respectively. The CHG-resistant rates of P. aeruginosa to ceftazidime, ciprofloxacin, levofloxacin and gentamicin were 53.1%(17/32), 78.1%(25/32), 65.6%(21/32) and 50.0%(16/32), respectively, which were all higher than those of CHG-sensitive P. aeruginosa (25.0%(8/32), 25.0%(8/32), 21.9%(7/32) and 15.6%(5/32), respectively), with statistical significance ( χ2=5.317, 18.080, 12.444 and 8.576, respectively, all P<0.05). The hospital mortality was 22.8%(13/57) in patients infected with CHG-resistant bacteria, which was higher than that in patients infected with CHG-sensitive bacteria ((7.0%(4/57); Fisher exact probability test, P=0.018)). CHG-resistant group had a higher history of CHG exposure and antimicrobial treatment (61.4%(35/57) and 70.2%(40/57), respectively), which were both higher than those with CHG-susceptible isolates (17.5%(10/57) and 47.4%(27/57), respectively), the differences were both statistically significant ( χ2=22.947 and 6.118, respectively, both P<0.05). In addition, the multi-drug resistance rate of CHG-resistant strains was 54.4%(31/57), which was higher than that of CHG-susceptible strains (35.1%(20/57)), the difference was statistically significant ( χ2=4.293, P=0.039). Conclusions:CHG resistant strains have higher antimicrobial resistance. Hospital mortality in patients infected with CHG-resistant bacteria is higher than patients infected with CHG-sensitive bacteria. The important risk factors are CHG exposure and antimicrobial therapy.
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Objective:To investigate the prevalence and characteristics of mcr genes in clinical isolates of Aeromonas spp. in our hospital, and provide reference for clinical analysis of the prevalence and expression of colistin resistance genes. Methods:Polymerase chain reaction (PCR) was used to detect mcr genes in 183 Aeromonas spp. strains. The minimum inhibitory concentrations (MICs) of colistin and polymyxin against mcr-positive Aeromonas spp. were detected by micro broth dilution method. Broth conjugation and filter mating conjugation were performed. Whole genome sequencing was used to analyze the genetic environment of mcr-3 gene in Aeromonas spp.. A recombinant Escherichia coli ( E. coli) DH5α-pGEM-T: : p mcr-3 strain was constructed to verify the expression of mcr-3 gene. Results:The positive rate of mcr-3 gene in 183 strains of Aeromonas spp. was 2.19% (4/183). No mcr-1 or mcr-2 gene was detected among these isolates. Antimicrobial susceptibility test showed that four mcr-3-carrying Aeromonas hydrophilia ( A. hydrophilia) strains were sensitive to colistin and polymyxin (MIC<2 μg/ml). Conjugation experiments indicated that mcr-3 gene could not be transferred between strains. Whole-genome sequencing analysis suggested that the mcr-3 genes carried by the A. hydrophilia isolates belonged to mcr-3.2 and mcr-3-like variants, and no adjacent transfer element was detected upstream and downstream. The recombinant E. coli DH5α-pGEM-T: : p mcr-3 strain was sensitive to colistin (MIC=2 μg/ml). Conclusions:The clinical isolates of A. hydrophilia in our hospital carried mcr-3 gene, but does not exhibit colistin resistance, and no evidence supported the transfer of mcr-3 gene for the time being.
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Objective:To analyze the molecular epidemiology and virulence characteristics of polymyxin-resistant Klebsiella pneumoniae ( K. pneumoniae). Methods:From 2011 to 2016, 1 376 strains of K. pneumoniae were isolated from various clinical specimens of hospitalized patients in First Affiliated Hospital of Wenzhou Medical University. Agar dilution method was used to screen out the polymyxin-resistant strains.Polymerase chain reaction (PCR) was used to detect the genes related to polymyxin resistance, and real-time fluorescence quantitative PCR was used to detect the relative mRNA expression level of drug resistant genes. Pulsed-field gel electrophoresis, multilocus sequence typing and Galleria mellonella larvae infection model were performed to analyze the molecular epidemiological and virulent characteristics. Results:A total of 14 strains (1.02%) of polymyxin-resistant K. pneumoniae were detected among 1 376 K. pneumoniae isolates. Subsequent sequencing identified mutations leading to amino-acid changes (K2E, F28C) in MgrB of 10 isolates and D150G in PhoQ of nine isolates, and genes such as mcr and crrB were not detected in all drug-resistant strains. Compared with standard strains, the relative expression levels of pmrH and pmrD mRNA of these drug resistant strains were increased. Analysis of the molecular epidemiology indicated that the 14 drug-resistant strains were divided into nine clones. Galleria mellonella larvae infection model revealed polymyxin-resistant K. pneumoniae isolates had higher virulence. Conclusions:Polymyxin-resistant K. pneumoniae has mutations in mgrB and phoQ genes, and mgrB mutation may play a key role in the change of virulence profiles. The homology among the polymyxin-resistant K. pneumoniae stains in this study is low.
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Objective:To investigate the role of type Ⅵ secretion system (T6SS) in the pathogenicity and antibiotic resistance of Acinetobacter baumanii. Methods:From January 1 to December 31, 2016, a total of 45 Acinetobacter baumanii isolates were collected from patients with bloodstream infection in the First Affiliated Hospital of Wenzhou Medical University. The susceptibilities to commonly used antimicrobial agents were determined by VITEK 2 Compact automatic microbiology analyzer. Detection of T6SS characteristic gene hemolysin coregulated protein ( hcp) was achieved by polymerase chain reaction. Biofilm formations, serum resistances and competition tests of T6SS-positive/negative Acinetobacter baumanii were performed in vitro. The clinical data of patients with bloodstream infection were collected and analyzed. Chi-square test, t test and Kruskal-Wallis test were conducted for statistical analysis. Results:The positive rate of T6SS in 45 Acinetobacter baumanii isolates was 53.3% (24/45). The resistance rates of T6SS-positive Acinetobacter baumanii to ceftazidime, ciprofloxdcin, gentamicin, imipenem, levofloxacin, piperacillin/tazobactam, tobramycin and cefepime (95.8%, 95.8%, 66.7%, 95.8%, 79.2%, 95.8%, 79.2%, 91.7%)were all higher than that of T6SS-negative Acinetobacter baumanii (28.6%, 28.6%, 28.6%, 28.6%, 9.5%, 23.8%, 23.8%, 28.6%), and the differences were all statistically significant ( χ2=22.12, 22.12, 6.51, 22.12, 21.83, 24.72, 13.79, 18.97, respectively, all P<0.05). The biofilm formation ability, serum resistance and competitive ability of T6SS-positive Acinetobacter baumanii were stronger than those of T6SS-negative Acinetobacter baumanii, and the differences were all statistically significant ( t=4.99, Z=-2.61 and -2.27, respectively, all P<0.05). The positive rate of T6SS isolated from intensive care unit (ICU) ward (80.0%, 16/20) was significantly higher than that from non-ICU ward (32.0%, 8/25; χ2=10.29, P<0.05). But T6SS had no effect on the prognosis of patients ( χ2=1.74, P=0.188). Conclusions:T6SS of Acinetobacter baumanii is associated with high pathogenicity, and the high drug resistance rate makes treatment extremely difficult. Physicians need to pay much attention, especially to the patients from ICU wards.
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Objective To investigate the chlorhexidine acetate-resistance in Klebsiella pneumoniae ( K. pneumoniae) clinical isolates and to analyze the possible mechanisms and molecular epidemiology of re-sistant isolates. Methods A total of 332 K. pneumoniae clinical isolates were collected in the First Affilia-ted Hospital of Wenzhou Medical University in 2015. Standard agar dilution was used to screen chlorhexidine acetate-resistant isolates. The minimum inhibition concentrations ( MIC) of chlorhexidine acetate to resistant isolates with and without the presence of carbonyl cyanide m-chlorophenyl hydrazone ( CCCP) , which was an efflux pump inhibitor, were analyzed. Efflux pump genes of cepA, qacE and qacΔE1 that carried by and ex-pressed in those isolates were detected by polymerase chain reaction ( PCR) and quantitative real-time PCR ( RT-qPCR) , respectively. The biofilm formation ability was measured by crystal violet staining. The homol-ogy among the chlorhexidine acetate-resistant isolates was investigated with multilocus sequence typing ( MLST) and pulsed-field gel electrophoresis ( PFGE) . Results Twenty-five K. pneumoniae strains were re-sistant to chlorhexidine acetate. The MIC values of chlorhexidine acetate for them were reduced by at least four-fold in the presence of CCCP. Strains carrying the genes of cepA, qacE and qacΔE1 accounted for 100％, 40％ and 40％, respectively. The expression of the efflux pump genes in the chlorhexidine acetate-resistant isolates was higher than that in the susceptible isolates. The biofilm formation ability of the chlo-rhexidine acetate-resistant isolates was better than that of the susceptible isolates. Furthermore, negative, weak-positive and positive biofilm formation ability was observed in four ( 16％) , 20 ( 80％) and one (4％) strains, respectively. The results of MLST and PFGE showed that the 25 chlorhexidine acetate-resist-ant isolates belonged to 19 different sequence types ( ST) with diverse PFGE patterns. Conclusions This study suggested that active efflux was the main mechanism of chlorhexidine acetate resistance in K. pneumoni-ae. The 25 chlorhexidine acetate-resistant K. pneumoniae strains possessed different biofilm formation ability and shared low homology.
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Objective@#To investigate the distribution and expression of T3SS virulence genes in clinically isolated Pseudomonas aeruginosa (P. aeruginosa) strains and its correlation with drug resistance. @*Methods@#A total of 68 P. aeruginosa isolates were collected from the First Affiliated Hospital of Wenzhou Medical University in 2015. The antimicrobial susceptibility was detected by the agar dilution method. The distribution of virulence genes such as exoU, exoS, exoT and exoY from different isolates was detected by PCR. The expression levels of transcriptional regulator genes (ptrA and exsA) and effector-related genes (exoT and exoS) in some isolates were determined by real-time fluorescence quantitative PCR, and the Pearson correlation analysis was used to analyze the results. @*Results@#The detection rates of exoT and exoY in 68 P. aeruginosa isolates were higher, accounting for 79.4% and 75.0%, respectively. The detection rate of exoT in wound-sourced isolates was significantly higher than that in sputum (97.0% vs 61.8%, P＜0.01). In addition, the genotype of exoU - /exoS + was the most common, accounting for 51.5% (35/68). The resistance rates of sputum-sourced isolates to imipenem and meropenem were significantly higher than that of wound-sourced isolates (47.1% vs 8.8%, 47.1% vs 14.7%, P＜0.01). The resistance rates of isolates carrying exoU gene to carbapenems, aminoglycosides and fluoroquinolones were higher than those of isolates carrying exoS, exoT or exoY genes. Pearson correlation analysis showed that the expression level of ptrA gene was negatively correlated with those of exoT, exoS and exsA genes (P＜0.05). @*Conclusion@#The P. aeruginosa isolates from our hospital carrying T3SS virulence genes exoT and exoY are common, and the virulence genes are related to the drug resistance of P. aeruginosa. In addition, ptrA may be a potential negative regulatory gene for the expression of T3SS virulence genes.
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Objective@#To investigate the in vitro antibacterial activity of triclosan combined with different antibacterial agents against triclosan-resistant multidrug-resistant Acinetobacter baumannii (A.baumannii).@*Methods@#A total of 626 A. baumannii strains were collected from the First Affiliated Hospital of Wenzhou Medical University from 2016 to 2017. The sensitivity of these A. baumannii strains to common antibiotics was detected by VITEK 2-compact automatical microbiological analyzer and the minimum inhibitory concentrations (MIC) of triclosan were detected by agar dilution method. Checkerboard method was used to detect the changes in MIC values of triclosan against 16 triclosan-resistant multidrug-resistant A. baumannii strains after it was used in combination with four external ointments, including gentamicin, erythromycin, chloramphenicol and kanamycin, and three common antibiotics of imipenem, meropenem and ciprofloxacin, respectively. Fractional inhibitory concentration index (FICI) was used to evaluate the joint bacteriostatic effects.@*Results@#Among the 626 A. baumannii strains, 17 were resistant to triclosan with a drug resistance rate of 2.7% (17/626). These triclosan-resistant strains had high MIC values for ciprofloxacin, imipenem, ceftazidime and other commonly used clinical antibiotic and most of them were multidrug-resistant. After triclosan was used in combination with seven different antibacterial drugs, the MIC values of all drugs decreased to various degrees compared with those when they were used alone. Triclosan in combination with gentamicin, chloramphenicol and ciprofloxacin showed synergistic effects on 62.5%, 56.25% and 62.5% of the 16 strains and additive effects on 37.5%, 43.75% and 37.5%, respectively. When it was used in combination with erythromycin, kanamycin, imipenem and meropenem, synergistic effects on 37.5%, 25%, 12.5% and 12.5%, additive effects on 37.5%, 56.25%, 62.5% and 62.5%, and indifferent effects on 25%, 18.75%, 25% and 25% of the strains were detected, respectively. No antagonistic effect was found between triclosan and any of the above antibiotics.@*Conclusions@#Triclosan combined with gentamicin, chloramphenicol and ciprofloxacin had better in vitro antibacterial effects against the triclosan-resistant multidrug-resistant A. baumannii strains in this study with synergistic and additive effects. Some indifferent effects were found between triclosan and kanamycin, erythromycin, imipenem and meropenem, but no antagonistic effects were detected.
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Objective To investigate the in vitro antibacterial activity of triclosan combined with different antibacterial agents against triclosan-resistant multidrug-resistant Acinetobacter baumannii ( A. bau-mannii) . Methods A total of 626 A. baumannii strains were collected from the First Affiliated Hospital of Wenzhou Medical University from 2016 to 2017. The sensitivity of these A. baumannii strains to common an-tibiotics was detected by VITEK 2-compact automatical microbiological analyzer and the minimum inhibitory concentrations ( MIC) of triclosan were detected by agar dilution method. Checkerboard method was used to detect the changes in MIC values of triclosan against 16 triclosan-resistant multidrug-resistant A. baumannii strains after it was used in combination with four external ointments, including gentamicin, erythromycin, chloramphenicol and kanamycin, and three common antibiotics of imipenem, meropenem and ciprofloxacin, respectively. Fractional inhibitory concentration index ( FICI) was used to evaluate the joint bacteriostatic effects. Results Among the 626 A. baumannii strains, 17 were resistant to triclosan with a drug resistance rate of 2. 7％ (17/626). These triclosan-resistant strains had high MIC values for ciprofloxacin, imipenem,ceftazidime and other commonly used clinical antibiotic and most of them were multidrug-resistant. After tri-closan was used in combination with seven different antibacterial drugs, the MIC values of all drugs de-creased to various degrees compared with those when they were used alone. Triclosan in combination with gentamicin, chloramphenicol and ciprofloxacin showed synergistic effects on 62. 5％, 56. 25％ and 62. 5％of the 16 strains and additive effects on 37. 5％, 43. 75％ and 37. 5％, respectively. When it was used in combination with erythromycin, kanamycin, imipenem and meropenem, synergistic effects on 37. 5％, 25％, 12. 5％ and 12. 5％, additive effects on 37. 5％, 56. 25％, 62. 5％ and 62. 5％, and indifferent effects on 25％, 18. 75％, 25％ and 25％ of the strains were detected, respectively. No antagonistic effect was found between triclosan and any of the above antibiotics. Conclusions Triclosan combined with genta-micin, chloramphenicol and ciprofloxacin had better in vitro antibacterial effects against the triclosan-resist-ant multidrug-resistant A. baumannii strains in this study with synergistic and additive effects. Some indiffer-ent effects were found between triclosan and kanamycin, erythromycin, imipenem and meropenem, but no antagonistic effects were detected.
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Objective@#To investigate the molecular mechanism of colistin resistance in Klebsiella pneumoniae (K.pneumoniae).@*Methods@#Three clinical isolates of colistin-resistant K. pneumoniae (FK1149, FK1920 and FK1934) and three colistin-resistant mutants (FK660R, FK713R and FK729R) were investigated. Resistance genes of pmrAB, phoPQ, mgrB, crrAB, mcr-1 and mcr-2 were detected by PCR and then analyzed by sequencing. PROVEAN platform was used to predict changes in the biological functions of proteins related to drug resistance. Expression of pmrH, pmrC, mgrB and phoP genes was measured using quantitative real-time PCR. LPS silver staining and conjugation assay were performed to analyze the three clinical colistin-resistant isolates.@*Results@#Amino acid substitutions in PmrA (G53V), PmrB (T157P, R256G), MgrB (F44C) and CrrB (E189K) were detected. ISkpn14 and IS5-like insertion sequences were detected in FK713R and FK729R, respectively. FK1149, FK1920 and FK1934 were negative for mcr genes. Compared with the wild-type strain, expression of pmrH and pmrC genes at the transcriptional level was increased in all investigated isolates. Changes in the expression of phoP and mgrB genes were also observed. A partial deletion of LPS was identified in FK1149.@*Conclusion@#LPS modification induced by inactivation of PmrAB or MgrB is the main molecular mechanism of colistin resistance in K. pneumoniae isolates in this study. Mutations in PmrA (G53V), MgrB (F44C) and CrrB (E189K) that might be related to colistin resistance are detected for the first time in clinical isolates of K. pneumoniae.
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Objective@#To evaluate the in vitro antibiotic effects of colistin combined with meropenem, levofloxacin or fosfomycin against colistin-heteroresistant Acinetobacter baumannii (A.baumannii).@*Methods@#A total of 576 A. baumannii clinical isolates were collected from the First Affiliated Hospital of Wenzhou Medical University from 2014 to 2015. Minimal inhibitory concentrations (MICs) of colistin against A. baumannii were detected by broth dilution method. Colistin-heteroresistant A. baumannii isolates were screened using population analysis profiles (PAPs). MICs of colistin combined with meropenem, levofloxacin or fosfomycin, and the four drugs used alone against colistin-heteroresistant A. baumannii were detected by checkerboard method and broth dilution method. Fractional inhibitory concentration index (FICI) was calculated to evaluate antibiotic effects.@*Results@#None of the 576 A. baumannii isolates was resistant to colistin as indicated by the broth dilution method. Nine colistin-heteroresistant A. baumannii isolates were identified using PAPs. Compared with the MICs of colistin used alone, the MICs of colistin used in combination with meropenem, levofloxacin or fosfomycin against colistin-heteroresistant isolates were all decreased. Colistin-meropenem combination showed synergistic (55.6%), additive (33.3%) and indifferent effects (11.1%), but no antagonistic effect. Colistin-levofloxacin combination showed synergistic (55.6%), additive (22.2%) and indifferent effects (22.2%), but no antagonistic effect. Colistin-fosfomycin combination showed synergistic (77.8%) and additive (22.2%) effects, but no indifferent or antagonistic effect.@*Conclusion@#In vitro use of colistin in combination with meropenem, levofloxacin or fosfomycin has synergistic and additive antibacterial effects against colistin-heteroresistant A. baumannii. Combinations of colistin-meropenem and colistin-levofloxacin have fewer indifferent effects and no antagonistic effect.
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We investigated molecular identification of a group of 14 strains of Aeromonas sp .,and genetic background of re‐sistance to beta‐lactams ,aminoglycosides .From January to December 2012 ,14 strains of Aeromonas sp .were collected from stool from diarrheal patients in enteric clinics in Ningbo First Hospital in Zhejiang Province ,China .Then ,molecular identifica‐tion by 16SrDNA ,23 kinds of beta‐lactamase genes ,6 kinds of aminoglycoside modifying enzyme genes ,6 kinds of 16srRNA methylase genes ,and 6 kinds of mobile genetic elements were analyzed by PCR .In addition ,genotyping and sample cluster a‐nalysis were performed .Results showed that 10 strains of A .hydrophila ,1 strain of A .aquariorum ,A .sobria ,A .entero‐pelogenes ,A .punctata were confirmed by 16SrDNA sequencing and arithmetic .Five kinds of beta‐lactamase genes ,4 kinds of aminoglycoside modifying enzyme genes ,and 3 kinds of mobile genetic elements were positive .BlaAQU of strain No .4(AQU‐2) and strain No .11(AQU‐3) were new subtypes .It’s suggested that identification of Aeromonas sp .should be performed by molecular identification method .This group of 14 strains of Aeromonas sp .conferred multidrug resistance .
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Objective To investigate the mechanisms of tigecycline nonsusceptibility in carbapen-ems-resistant Acinetobacter baumannii ( CRAB) strains in order to provide a theoretical basis for a reasonable use of antibiotics and the control of nosocomial infection .Methods Susceptibility testing of 120 non-dupli-cate CRAB strains to tigecycline was performed by using the broth microdilution method .Minimal inhibitory concentrations ( MIC) of tigecycline against the A.baumannii strains were determined by using the broth mi-crodilution method before and after exposing the strains to Carbonylcyanide-m-chlorophenylhydrazone (CCCP), which was the efflux pump inhibitor .Polymerase chain reaction (PCR) was used to amply the ef-flux pumps genes including adeB, adeJ, adeG, abeM, adeE, adeRS, tetX and tetX1.The real-time PCR was performed to measure the expression of efflux pumps genes including adeB, adeJ, adeG, abeM and adeE.Results A total of 120 CRAB strains were collected including 13 (10.8%) tigecycline non-suscep-tible A.baumannii (TNAB) strains and 107 (89.2%) tigecycline susceptible A.baumannii (TSAB) strains.The MIC values of tigecline to the 120 CRAB strains were in a range of 0.25 μg/ml to 8 μg/ml. The adeR and adeJ genes were detected in 90.0%and 92.5%of the 120 CRAB strains, respectively.The positive rates of adeB, adeS, adeG and abeM genes among the 120 CRAB strains were all 94.2%.None of the three genes including adeE, tetX and tetX1 were detected .The mean expression levels of adeB and adeJ in TNAB strains were respectively increased by 18.69 folds and 5.46 folds as compared with those in sensi-tive strains.No significant increase in the expression of adeG and abeM genes was observed in TNAB strains . A 4-fold decrease in the MIC was observed in 8 out of 13 TNAB isolates treated with 10 μg/ml of CCCP .The CCCP could partially reverse the resistance pattern of tigecycline .Conclusion The efflux pump sys-tems of adeABC and adeIJK rather than the abeFGH and abeM systems might play an important role in reduc-ing the tigecycline susceptibility in carbapenems-resistant A.baumannii strains.
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Objective To investigate the drug resistant genes against carbapenems,aminoglycosides and quinolones and the molecular epidemiology of clinical isolates of Acinetobacter baumannii.Methods Forty non-duplicate strains of Acinetobacter baumannii were collected from clinical specimens in First Affiliated Hospital of Wenzhou Medical University.The identification of strains was conducted by Vitek 2 Compact system.The susceptibilities to antimicrobials commonly used were determined by agar plate dilution method and broth microdilution method.The presence of class B metalloenzyme-encoding genes (blaIMP,blaVIM,blaNDM,blaSIM,blaGIM),class D cabapenemase-encoding genes (blaOXA-23,blaOXA-48,blaOXA-58),16S rRNA methylase genes (armA,rmtB) and quinolone resistance-determining regions (QRDR) in gyrA and parC were detected by polymerase chain reaction (PCR) and sequenced.Chromosomal or plasmid location of blaOXA-23 and armA genes were assessed by Southern blot.Multiple loci sequence classification (MLST) was performed to analyze the molecular epidemiology of these strains.Results All of the 40 isolates were multi-drug resistant Acinetobacterbaumannii (MDR-AB) and showed high level resistance to all of the tested antimicrobial agents excluding colistin and tigecycline.The positive rates of blaOXA-23 and armA were 90％ and 95％,respectively.All of the 40 isolates carried QRDR mutations in gyrA and parC genes,leading to the Ser83→ Leu and the Ser80→ Leu amino-acid substitutions,respectively.Southern blot showed the chromosomal location of blaOXA-23 and armA genes.Six different ST (ST191,ST381,ST373,ST426,ST208 and ST207) were assigned for these isolates by MLST and the most dominant clones were ST191 (23/40) and ST381 (10/40).Conclusions The predominant cabapenemase-encoding gene and 16S rRNA methylase gene of Acinetobacter baumannii isolates in First Affiliated Hospital of Wenzhou Medical University are blaOXA-23 and armA,respectively,which may be located on the chromosome and vertically transmit the drug resistance.ST191 MDR-AB with blaOXa-23 and armA gene clonally spread in this hospital.
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Objective To investigate the prevalence and plasmid size of qnrD determinant in Morganella morganii (M.morganii) isolates.Methods A total of 100 non-duplicated M.morganii clinical isolates were collected from inpatients.Standard ager dilution method was used to determine the minimum inhibitory concentrations (MICs) of fluoroquinolones against M.morganii isolates.PCR were performed to detect plasmid-mediated quinolone resistance determinants (PMQRs) in M.morganii isolates and the prevalence of extended-spectrum β-lactamase (ESBL) genes and AmpC β-lactamase genes in PMQRs-positive M.morganii strains.The homology analysis among qnrD-positive M.morganii strains were conducted by using pulsed-field gel electrophoresis (PFGE).The location of qnrD gene and the size of plasmid carrying it were determined by southern hybridization.The transferability of qnrD gene was determined by conjugation experiment.Results Thirty out of 100 M.morganii isolates (30％) were found carrying PMQRs including 17 qnrD-positive strains,14 aac (6')-Ib-cr-positive strains and 5 qepA-positive strains.PCR and sequencing confirmed that thirty PMQRs-positive isolates carried blaDHA-1.Among them,six isolates were positive for ESBLs genes (four for blaCTX-M-14,one for blaCTX-M-3 and one for blaCTX-M-24) and four isolates were positive for blaTEM-1.Almost all PMQRs-positive M.morganii isolates showed reduced susceptibility to fluoroquinolones.Moreover,seventeen qnrD-positive M.morganii isolates harbored blaDHA-1 including five (29.4％) harboring aac(6')-Ib-cr gene,four (23.5％) harboring blaCTX-M-14,two (11.8％) harboring blaTEM-1 and one harboring aac(6')-Ib-cr gene,blaCTX-M-14 and blaDHA-1.PFGE analysis showed that the 17 qnrD-positive M.morganii isolates were divergent from each other and not clone-related.Southern hybridization analysis showed that qnrD genes of all M.morganiiis isolates were mainly located in a 2.7 kb plasmid,but only a few of them were located in a size of 5.1 kb plasmid.M.morganiiis isolates failed to transfer qnrD gene to E.coli EC600 through conjugation.Conclusion PMQRs were widely distributed in M.morganiiis isolates.qnrD gene was the predominant determinants with a high prevalence rate of 17.0％,followed by aac(6')-Ib-cr gene.qnrD gene was located on a non-conjugative plasmid of approximately 2.7 kb or 5.1 kb.One qnrD-positive M.morganii isolate carrying aac(6')-Ib-cr gene,blaCTX-M-14 and blaDHA-1 was detected.
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Objective To provide evidence for the prevention and control of nosocomial infection by knowing the infecting status of hospital.Methods The clinical data of 64 431 hospital patients from 2010 to 2012 were analyzed prospectively and retrospectively.Results A total of 2 636 patients of nosocomial infection were collected in 3 years,the infection rate was 4.09 ％ (2 636/64 431).Upper and lower respiratory tract was the main infection site.ICU,urology,neurology,endocrinology were the main infection outbreak departments.Gram negative bacilli was still the chief bacterium,accounted for 52.48％(689/1 313).Conclusion To strengthen the control of nosocomial infection and training of medical staff,strict insist on aseptic operation,reduce invasiveness operation,use antibacterial agent reasonable are the effective and preventative measures to decrease nosocomial infection.
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Objective To investigate the mechanism of carbapenems resistance in Serratia marces-cens strains isolated from Wenzhou and their epidemiological characteristics.Methods 147 non-duplicated Serratia marcescens isolates were collected from the First Affiliated Hospital of Wenzhou Medical University during 2006 to 2012.The antimicrobial susceptibility test for all isolates was performed by using Vitek2 Compact to screen carbapenems-resistant Serratia marcescens strains.The minimum inhibitory concentrations ( MICs) of 10 commonly used antibiotics against carbapenems-resistant Serratia marcescens strains were de-termined by agar dilution method.The phenotypes of carbapenemase were analyzed by using the modified Hodge test.PCR analysis was used to detect the genes encoding carbapenemase, AmpC enzyme, efflux pump and outer membrane proteins.The changes of MICs before and after using CCCP efflux pump inhibitor were measured by agar dilution method.Outer membrane proteins were detected by SDS-PAGE.Carbapene-ms resistance genes were transferred from carbapenems-resistant Serratia marcescens strains to recipient strains by conjugation.The transconjugants were amplified by PCR and measured for MICs.Pulsed-field gel electrophoresis ( PFGE) was used to analyze homology among strains.Results 11 isolates resistant to car-bapenems were screened out from 147 Serratia marcescens isolates and all of them were resistant to penicil-lins, cephalosporins and ertapenem.10 out of the 11 isolates were both resistant to imipenem and meropen-em, but remained susceptible to fluoroquinolones and aminoglycoside.Among the 11 isolates, 10 carried blaKPC-2 gene, 1 carried blaIMP-1 gene, 8 harbored both blaEBC and blaMOX genes, 1 harbored both blaEBC and blaDHA genes, and 1 carried blaEBC , blaMOX and blaDHA genes.No additional genes were identified by PCR.The MICs of imipenem to 7 isolates and the MICs of ertapenem to 3 isolates were respectively decreased by 4-64 folds and 8-256 folds after using CCCP.CCCP had no effects on the MICs of meropenem.Loss of outer membrane protein was not detected among the 11 isolates.The blaKPC-2 genes were successfully transferred from 7 isolates into recipient strains.The MICs against the transconjugants were higher than those against the recipient strains in varying degrees.PFGE analysis demonstrated that 8 out of 11 Serratia marcescens strains belonged to one clonotype.Conclusion KPC-2 carbapenemase played an essential role in carbapenems re-sistance in Serratia marcescens strains isolated from Wenzhou.Attention should be paid to the clonal spread of KPC-2 and its horizontal transmission in Wenzhou.
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Objective To study the vancomycin-resistant genes and the virulence factors genes in vancomycin-resistant Enterococci (VRE),and to analyze the drug-resistance character and epidemic characteristics of VRE strains and provide the basis for clincal selection of drugs and infection control.Methods VRE were screened by agar dilution sieving plate (ADSP) containing 6 μg/ml of vancomycin,drug resistance of VRE to other common antibiotics were detected by VITEK-60 automatic microbial analyzer.The gene types and virulence factor genes of VRE were determined by PCR.And the genetic relationships among VRE were determined by multilocus sequence typing.Results Seven vancomycin-resistant Enterococcus faecium strains were found in 360 enterococcus strains.All the VRE strains exhibited high-level vancomycin resistance ; some of them were medium or senstive to teicoplanin.They all carried vanA gene and esp gene and one of them carried 4 kinds of virulence factor genes.The ST type of the 7 VRE strains were diffused distribution.Conclusion We found vanB phenotype vanA genotype vancomycin-resistant Enterococcus faecium isolates in Wenzhou; these VRE strains were multidrug resistance and carried various virulence factor genes.Linezolid could be used as a recommend drug for treatment of VRE infection.The protection of antibiotics sensitivity should be strengthened.
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Objective To investigate the expressions of TF mRNA and TFPI mRNA of liver in rats with Vibrio vulnificus sepsis and to assess the interventional effects of cefoperazone sodium along with levofloxacin lac-tate. Method One hundred and ten male SD rats were divided (random number) into normal control group (NC group, n = 10), Vibrio vulnificus sepsis group (VV group, five subgroups n = 10 in each), drug intervention model (AA group, five subgroups n = 10 in each). The Vibrio vulnificus sepsis models and drug intervention models of rat were made. The reverse transcription polymerase chain reaction (RT-PCR) assay was employed for the measurement of TF mRNA and TFPI mRNA. ANOVA and t-test performed with SPSS version 12.0 software. Results Compared with NC, the expressions of TF mRNA in liver increased markedly 2 h,6 h, 12 h and 16 h af-termodeling in VV groups (P<0.05), and reached peak 6 hours after modeling. The expressions of TF mRNA in liver of rats in AA groups were much higher than those in NC group 9 h and 12 h after modeling (P<0.05). The expressions of TFPI mRNA in liver of rats in VV groups and AA groups were not significantly different to those in NC group (P>0.05). Compared with VV groups, the expressions of TF mRNA in liver of rats in AA groups were greatly lowered 9 hours after administration of bactericide (P<0.05), and the expressions of TFPI mRNA in liver of rats in AA groups were significantly higher 12h and 16 h after intervention (P<0.05). Conclusions There is a obvious imbalance between coagulation and anticoagulation functions of circulation system during Vibrio vulnificus sepsis, and the imbalance can be corrected gradually after treatment with antibacterial agents.
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Objective To research the distribution and the characteristics of the plasmid mediated quinolone resistant genes in Shewanella algae. Methods The qnr, qepA, aac(6')-Ib-cr genes were amplified by PCR, then the positive PCR products were sequenced to determine the gene type. The transferability of plasmid mediated quinolone resistance was ensured by conjugation experiment. MICs were measured by E-test. qnrA gene was mapped to plasmids to locate it. Results The qnrA gene were detected in the Shewanella algae, this is a newfound subgroup qnrA7, the GenBank accession no. was GQ463707, qnrB, qnrS,qnrC, qnrD, qepA and aac(6')-Ib-cr genes were not detected. qnrA7 reside in a plasmid about 33 kb, conjugation experiment was unsuccessful. The strain was susceptible to quinolones. Conclusion It deserves paying close attention to the report of an original qnrA subgroup in an isolate of water-borne species of Shewanella algae.
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Objective To study the structures of the plasmids of Klebsiella pneumoniae KF3 at the genome metagenome level througth with whole plasmid DNA sequencing, to analyze the functional genes carried by plasmid and to identify the correlation of resistance and pathogenicity between the plasmids and the host strains. Methods The alkaline lysis method was used to extract plasmids. We constructed the small insert pUC18 library and the large insert Forsmid library, sequenced and used the Phred / Phrap / Consed package to assemble these sequences and gained a complete sequence. The open reading frame(ORFs) were predicted by the Glimmer software and annotated, analyzed the functions of these genes. Results We successfully constructed the pUC18 library and the Fosmid libraries for the plasmid DNA and obtained three circular double-stranded DNA plasmids: pKF3-70 (69 477 bp), pKF3-90 (91 327 bp) and pKF3-147 ( 147 416 bp). There were drug resistant genes, conjugative transfer genes and mobile DNA elements identified on three plasmids. Conclusion The three plasmids of KF3 could be transferred among different strains. It would lead to the dissemination of the resistant genes.