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Antimicrobial susceptibility of the Mycoplasma pneumoniae strains isolated from pediatric patients

Hong ZHANG ; Xinyu YE ; Xiaogang XU ; Minggui WANG ; Yang LIU

Chinese Journal of Infection and Chemotherapy.2015;(1):63-66.

Objective To investigate the profile of antimicrobial susceptibility of the Mycoplasma pneumoniae (Mpn)strains isolated from pediatric patients with respiratory tract infection.Methods Antimicrobial susceptibility testing was conducted with a total of 112 Mpn clinical strains by broth microdilution method.Sequence analysis of full 23S rRNA genes was performed for all Mpn strains.Results One hundred and twelve Mpn strains were isolated from January 2009 to March 2011. Of these clinical isolates,98 (87.5%)were resistant to erythromycin and azithromycin.All macrolide-resistant Mpn strains harbored an A2063G or A2064G transition mutation in domain V of 23S rRNA genes.Mpn isolates were still very susceptible to the tetracyclines and fluoroquinolones tested.Conclusions The Mpn strains from pediatric patients are highly resistant to macrolides.The mechanism of macrolide resistance may be associated withthe transition mutation on 23S rRNA gene.

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Analysis of distribution and drug resistance ofAcinetobacter baumannii in neurology ward

Jianping ZHAO ; Fang WU ; Xiulan ZHOU

Chinese Journal of Infection and Chemotherapy.2015;(1):60-62.

Objective To examine the distribution and antibiotic resistance of the Acinetobacter baumannii strains isolated from Department of Neurology.Methods A retrospective review was conducted for the 269 strains of A.baumannii isolated during the period from January 2009 to March 2014.VITEK 2 Compact system was used for bacteria identification and antimicrobial susceptibility testing.The data were analyzed with WHONET 5.6 software and compared by Chi-square test.Results The prevalence of A.baumannii was higher in Department of Neurology than in Department of Neurosurgery or Neurology ICU. Majority (97.4%)of the A.baumannii strains were isolated from sputum.About 54.3% of the A.baumannii isolates were resistant to imipenem.Relatively lower percentage of the A.baumannii isolates were resistant to amikacin (20.7%),but as high as 54.3% and 55.0% of the strains were resistant to imipenem and piperacillin-tazobactam.More imipenem-non-resistant A.baumannii strains (89.4%)were resistant to trimethoprim-sulfamethoxazole than imipenem-resistant A.baumannii (72.6%)(P < 0.05). However,to the other antimicrobial agents tested,imipenem-resistant A.baumannii strains showed significantly higher resistance rate than imipenem-non-resistant A.baumannii strains (P< 0.05).Conclusions The prevalence of A.baumannii and imipenem-resistant A.baumannii is high in Department of Neurology.Further monitoring of antibiotic resistance and rational use of antimicrobial agents are helpful to effectively control the epidemic of multidrug-resistant A.baumannii.

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Risk factors of surgical site infection in patients with colorectal cancer

Guangzhao YI ; Suxin LUO ; Xihan WANG ; Ting YU ; Yingfu WANG

Chinese Journal of Infection and Chemotherapy.2015;(1):57-59.

Objective To evaluate the incidence of surgical site infection (SSI)in patients with colorectal cancer and identify the risk factors of SSI.Methods A total of 392 patients who underwent colorectal cancer resection at the First Affiliated Hospital of Chongqing Medical University between September 2012 and September 2013 were included and analyzed in terms of the presence of SSI.SSI risk factors were identified by both univariate and multivariate analysis.Results The overall incidence of SSI was 23.0%.Univariate analysis showed that duration of operation above 75 th percentile,colostomy,surgical procedure, type of surgical incision,and American Society of Anesthesiologists (ASA)score were significantly associated with higher risk of SSI (P <0.05).Binary logistic regression suggested that duration of operation above 75 th percentile (P = 0.000,OR =3.017),colostomy (P =0.008,OR=2.642),Contaminated incision (P =0.016,OR=3.311)and laparoscopic surgery (P =0.016,OR=0.523)were significantly different in terms of presence or absence of SSI.Conclusions Duration of operation above 75th percentile,colostomy and contaminated incision are independent risk factors,while laparoscopic surgery is a protective factor for SSI in patients with colorectal cancer.

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Establishment of a murine model of Acinetobacter baumannii pneumonia with a new intubation method

Shuxin XIAO ; Xu ZHAO ; Beining GUO

Chinese Journal of Infection and Chemotherapy.2015;(1):51-56.

Objective To construct a new intubation method with an otoscope and establish a murine model of Acinetobacter baumannii pneumonia with this method.Methods Part I:The Hallowell Intubation Pack for mice (Braintree Scientific Inc., USA)was used to construct a new intubation method with an otoscope.Part II:Twenty-four female ICR mice were randomized into 3 groups including control (group 1),immunosuppression (group 2)and infection after immunosuppression groups (group 3),with 8 mice in each group.The mice were treated with cyclophosphamide (CTX)by peritoneal injection to posterior orbital venous plexus.The total number of white blood cells,the number of neutrophils and the percentage of neutrophils were determined.Four mice were sacrificed at 0 h and 48 h after inoculation in each group.Then the lungs from each mouse were aseptically collected for quantitative culture and histopathology.Results Part I:Ten mice were successfully intubated using the new method and none of the mice was dead.Pulmonary bacterial culture at baseline (0 h)was (2.91×107-5.32×107 )CFU/g tissue,while the mean± standard deviation was (4.05 × 107 ± 0.82 × 107 )CFU/g tissue.The results showed that this new method had a perfect repeatability.Part II:Over 48 h,2 mice were dead in group 3,while no mouse was dead in other 2 groups.For group 3,the average pulmonary bacterial culture was 4.13×107 CFU/g tissue at 0 h and reached 3.62×1010 CFU/g tissue at 48 h (increased appropriate 1 000 times,P <0.01).The histopathologic changes in lung showed local granulomas and abscess in the alveolar space.Conclusions Intubation under the guidance of otoscope had the advantages of high repeatability and easy to operate.Additionally,the method provided stable and consistent bacterial inocula into lungs.The murine model of Acinetobacter baumannii pneumonia was successfully established with a new intubation method under the guidance of otoscope.

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Serotype distribution and antimicrobial resistance ofStreptococcus pneumoniae in children in Humen area

Ming LI ; Dingding TAN

Chinese Journal of Infection and Chemotherapy.2015;(1):43-46.

Objective To investigate the serotype distribution and antimicrobial resistance of the S.pneumoniae strains isolated from children in Humen,and evaluate coverage of the serotypes by several vaccines,especially PCV7.Methods A total of 229 S.pneumoniae strains were isolated from the children treated in our hospital during January 2011 and December 2012. Capsular typing was performed by Quellung reaction.Antimicrobial susceptibility was determined by ATB STREP 5.The data were analyzed by WHONET 5.5 software according to CLSI 2010 breakpoints.Results The main serotypes identified from the 229 S.pneumoniae strains were 19F (146,63.8%),23F (49,21.4%),6B (12,5.2%)and 14 (8,3.5%).The coverage of these serotypes was 95.2% by PCV7,95.2% by PCV11,and 97.4% by PCV13.Of all the S.pneumoniae strains,penicillin susceptible S.pneumoniae (PSSP)accounted for 92.6% (212/229),penicillin intermediate S.pneumoniae (PISP)accounted for 5.7% (13/229)and penicillin resistant S.pneumoniae (PRSP)accounted for 1.7% (4/229).About 95.6%,93.0%, 88.2%,86.5%, 7.0%, 2.2% and 0.9% of the isolates were resistant to erythromycin, clindamycin, tetracycline, trimethoprim-sulfamethoxazole,chloramphenicol,cefotaxime and amoxicillin,respectively.No strain was found resistant to vancomycin or levofloxacin.Conclusions The serotypes 19F, 23F, 6B and 14 are the main prevalent serotypes of S. pneumoniae in children in Humen.PCV7 could cover 95.2% of these S.pneumoniae,indicating its appropriateness for vaccination in Humen area.These S.pneumoniae strains were highly sensitive to vancomycin,levofloxacin and penicillin,but relatively more resistant to erythromycin, clindamycin, tetracycline and trimethoprim-sulfamethoxazole.

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Genotyping and detection of virulence genes for methicillin-resistant and-sensitive Staphylococcus aureus

Junrui WANG ; Xiaoli DU ; La TA ; Jinghua CUI ; Quan FU ; Yanqiu HAN

Chinese Journal of Infection and Chemotherapy.2015;(1):70-75.

Objective To elucidate the difference between methicillin-resistant Staphylococcus aureus (MRSA)and methicillin-sensitive S.aureus (MSSA)in terms of genotypes and distribution of virulence genes with the clinical strains isolated from Hohhot,and explore the relationship between the changing resistance of S.aureus and the virulence transition.Methods Pulsed field gel electrophoresis (PFGE)and multi locus sequence typing (MLST)methods were employed to do molecular typing for 30 MRSA strains and 30 MSSA strains isolated from inpatients in Hohhot,Inner Mongolia.PCR method was used to profile the distribution of virulence genes among these strains.Results PFGE typing results showed that 60 S.aureus strains were classified into 19 major types.MSSA strains belonged to 16 types,mainly types I and H.MRSA strains mainly belonged to types of K and M.Among the 20 strains with different PFGE types,MRSA strains were mainly identified as ST-239 type.but the prevalence of sec ,seg ,sei,sem,sen,seo,fnbB ,ebpS and cap 5 was higher in MSSA strains than in MRSA strains (P<0.05).Conclusions The clinical strains of S .aureus isolated from Hohhot showed diverse genotyping features.ST-239 was the major PFGE type of MRSA strains.The prevalence of virulence genes was higher in MSSA strains than in MRSA strains. Characteristic cluster is found for specific virulence genes.The results also suggest that acquisition of specific antibiotic resistance may be associated with change of specific virulence feature in S.aureus.

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Surveillance of antibiotic resistance in gram-negative bacilli strains collected from Chuzhou First Hospital during 2013

Qiang XIE ; Mingjie CAO ; Jinli WANG ; Tiantian XU

Chinese Journal of Infection and Chemotherapy.2015;(1):67-69.

Objective To investigate the distribution and antibiotic resistance of gram-negative bacilli for better antimicrobial therapy in our hospital.Methods A retrospective analysis was conducted for the 1 060 strains of gram-negative bacilli isolated from clinical specimens during 2013.Results Of the 1 060 gram-negative bacterial strains isolated during 2013,E.coli,K . pneumoniae,P .aeruginosa and A.baumannii were the leading pathogens,accounting for 29.3%,22.8%,11.5% and 9.9%,respectively.The prevalence of extended spectrum-lactamases (ESBLs)positive strains was 63.7%,32.2% and 28.0% in E.coli,K .pneumoniae and P .mirabilis,respectively.The Enterobacteriaceae strains were highly sensitive to carbapenems.The percentage of the P .aeruginosa isolates resistant to meropenem,imipenem or amikacin was lower than 30%.The percentage of the Acinetobacter spp.(A.baumannii accounted for 70.9%)strains resistant to meropenem and imipenem were 25.0% and 26.2%.Conclusions Most of the gram-negative bacilli are resistant to multiple antimicrobial agents. We should strengthen the monitoring of the antibiotic resistance of gram-negative bacilli and optimize antimicrobial therapy.

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Pathogens from 1 151 cases of urine culture and their antibiotic resistance profile

Hui CAI

Chinese Journal of Infection and Chemotherapy.2015;(1):38-42.

Objective To analyze the pathogens and antibiotic resistance profile in patients with urinary tract infections who were treated from 2011 to 2013 to provide evidence for rational use of antimicrobial agents.Methods SIEMENS MicroScan WalkAway 96 Plus system or API system was used for identification of bacteria and fungi.Antimicrobial susceptibility testing was conducted by disk diffusion method.WHONET 5.6 software was used for data analysis.Results A total of 344 (29.9%) strains of pathogens were detected from 1 151 midstream urine culture specimens,of which 76.5% (263/344)were gram negative bacteria,including E.coli (53.2%,183/344),K.pneumoniae (9.6%,33/344),Proteus (6.1%,21/344),and P . aeruginosa (3.5%,12/344).About 23.5% (81/344)of the isolates were gram-positive bacteria,including Enterococcus faecalis (4.9%,17/344)and coagulase-negative Staphylococcus (4.4%,15/344).ESBLs were produced in 51.9% of the E. coli isolates and 63.6% of the K.pneumoniae isolates.ESBLs-producing strains showed significantly higher resistance rates to cephalosporins,quinolones,tetracyclines,sulfonamides and other antimicrobial agents than non-ESBLs-producing strains (P <0.05).Enterobacteriaceae isolates were highly sensitive to carbapenems (90.5%-100% sensitive).P .aeruginosa strains were relatively sensitive to ciprofloxacin,amikacin and meropenem (83.3%).Gram-positive cocci remained highly sensitive to antimicrobial agents.Regular monitoring and timely analysis of the pathogens of urinary tract infections and their resistance profile are of great importance to rational use of antimicrobial agents.

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Analysis of the genetic homology and resistant genes in clinical isolates of extensively drug-resistant Acinetobacter baumannii

Qing SUN ; Zhengyin ZHANG

Chinese Journal of Infection and Chemotherapy.2015;(1):28-31.

Objective To investigate the genetic homology in clinical isolates of extensively drug-resistant Acinetobacter baumannii (XDRAB),so as to provide evidence for better controlling hospital infections.Methods The genotypes of 28 clinical XDRAB isolates were determined by Enterobacterial Repetitive Intergenic Consensus PCR (ERIC-PCR).PCR was conducted to analyze 9 types of β-lactamase genes (blaKPC,blaIMP,blaVIM,blaNDM-1,blaOXA-23,blaOXA-24,blaOXA-48, blaOXA-51 and blaOXA-58),the outer membrane porin gene (CarO)and insertion sequence (IS)ISAba1.We also carried out linkage analysis for ISAba1-OXA23 and ISAba1-OXA58.Results Most of the above 28 XDRAB strains were isolated from respiratory tract specimens from intensive care patients.The result of ERIC-PCR showed that there was high homology between all the strains,suggesting that they might derive from the same clone.The genes blaOXA-23,blaOXA-51,CarO and the IS ISAba1 except Class Bβ-lactamase genes,blaOXA-24,blaOXA-48,blaOXA-58,ISAba1-OXA23 and ISAba1-OXA58 were detected in all the clinical strains by PCR.Conclusions All the XDRAB isolates belong to the same clone and carry the same drug-resistant genes,indicating that there was clone spread among XDRAB isolates.

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Performance of colloidal gold immunochromatography assay in rapid detection of respiratory syncytial virus antigen

Jie YI

Chinese Journal of Infection and Chemotherapy.2015;(1):24-27.

Objective To investigate the sensitivity and specificity of colloidal gold immunochromatography assay in rapid detection of respiratory syncytial virus (RSV)antigen.Methods A total of 197 nasal-pharyngeal swabs (NPs)or nasal-pharyngeal aspirates (NPAs ) obtained from patients were tested by RSV assay kits, i. e., colloidal gold immunochromatography assay.The results determined by reverse-transcription polymerase chain reaction (RT-PCR)were taken as reference.Compared to the results of RT-PCR,the sensitivity of the kit was different when testing different types of specimens or specimensobtained from patients of different ages.Results A total of 95 (48.2%)samples were positive for RSV tested by RT-PCR.The sensitivity and specificity of colloidal gold immunochromatography assay were 34.7% and 100%, respectively compared with RT-PCR results.The positive rate of the assay was higher in testing NPAs than NPs (36.2% vs 8.6%,P < 0.01 ), which was the same in the sensitivity (22.1% vs 12.6%). The positive rate of colloidal gold year old,RT-PCR method should be used for RSV detection in clinical practice to avoid missed diagnosis.

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