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Objective To investigate the susceptibility profile of clinical isolates in the First Affiliated Hospital of Guangzhou Medical University during 2015-2017. Methods Susceptibility test was carried out using Kirby-Bauer method or automated systems. Results were analyzed according to CLSI 2017 breakpoints. Results A total of 17 645 clinical isolates were isolated from January 2015 to December 2017, including 3 091(17.5％)gram positive and 14 554(82.5％)gram negative bacteria. Methicillinresistant S. aureus(MRSA)and coagulase-negative Staphylococcus(MRCNS)accounted for 50.7％ and 77.9％, respectively. No staphylococcal isolates were found resistant to vancomycin, teicoplanin or linezolid. E. faecalis strains showed much lower resistance rate to most drugs tested than E. faecium. Nine(0.8％)E. faecalis isolates were found resistant to vancomycin. A total of 227 strains of the non-meningitis S. pneumoniae were tested, 44.1％ of which were isolated from adults and 55.9％ from children. Most of the S. pneumoniae isolated from adults and children were susceptible to penicillin(88.0％ and 81.1％, respectively). E. coli showed the highest proportion in three years. ESBLs were produced in 53.3％ of E. coli and 28.5％ of Klebsiella spp. A total of 255 strains of carbapenem-resistant Enterobacteriaceae(3.7％), 665 strains of carbapenem-resistant Pseudomonas aeruginosa(26.2％)and 900 strains of carbapenem-resistant Acinetobacter baumannii(57.5％)were identified. The annual change of prevalence was insignificant. A total of 141 strains of extensively-drug resistant Pseudomonas aeruginosa(5.6％)and 458 strains of extensively-drug resistant A. baumannii(29.3％)were identified, showing decreasing prevalence from 2015 to 2017. Conclusions The bacterial resistance in this hospital is relatively stable in the past three years, but it is still necessary to strengthen hospital infection control and management, and maintain good practice in surveillance of bacterial resistance.
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Objective To investigate the colonization of Gram-negative bacilli carrying mcr-1 gene in intestinal tracts of inpatients and people having physical examination for further elucidating the molecular and epidemiological features of mcr-1 gene. Methods A total of 1263 and 750 fecal specimens were col-lected from inpatients in the First Affiliated Hospital of Guangzhou Medical University and people having physical examination in the Kingmed Physical Examination Centre, respectively. Drug-resistant bacteria were isolated using Maconkey agar supplemented with colistin. PCR was performed to detect the bacteria carrying mcr-1 gene. Multilocus sequence typing ( MLST) and enterobacterial repetitive intergenic consensus-PCR ( ERIC-PCR) were used for homology analysis. The transferability of mcr-1 gene was verified by plasmid transfer assays. Plasmids of mcr-1-carrying strains were typed by PCR-based replicon typing techniques. Twelve virulence-related genes were also detected by PCR. Results Ninety-two colistin-resistant strains were isolated from the 1263 samples from inpatients(7. 3％, 92/1263) and two of them were positive for mcr-1 gene ( one strain also carried the blaNDM-5 gene) . Thirty-six colistin-resistant strains were isolated from the 750 samples of physical examination group (4. 8％, 36/750) and one of them carried the mcr-1 gene. MLST analysis showed that three mcr-1-carrying Escherichia coli strains ( minimum inhibitory concentration of colistin:8 μg/ml) belonged to three different sequence types. Moreover, they exhibited different banding patterns in ERIC-PCR analysis. All of the mcr-1-carrying isolates could transfer mcr-1 gene to the recipient strains successfully. Six types of incompatibility plasmids were detected in the mcr-1-carrying isolates ( IncFⅡ, IncX2, IncHI2, IncFIB, IncX4 and IncX1). Virulence-related genes fimH, iutA and fyuA were detec-ted in all mcr-1-carrying Escherichia coli strains. Conclusions Colistin-resistant strains and mcr-1 gene are prevalent in inpatients and people having physical examination, which brings potential risk for the control of clinical infections.
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Objective To establish the in vitro biofilm model of Laribacter hongkongensis(LH),to analyze the type Ⅰ integron related genes carried by LH and to investigate the mechanism of LH resistance to quinolones.Methods The biofilm forming abilities of LH clinical isolates were determined by Giemsa staining qualitative method and by crystal violet staining semi-quantitative method.The sensitivity of LH to norfloxacin,ofloxacin,levofloxacin,ciprofloxacin and lomefloxacin in both planktonic and biofilm conditions were dectermined by broth microdilution susceptibility tests.Type I integron related genes carried in 18 LH strains resistant to quinolone were detected by PCR amplification method.Results The detection results by Giemsa staining demonstrated that 36 strains in 55 LH clinical isolates formed visible biofilm,and the biofilm formation rate was 65.4%(36/55).In the biofilm forming ability detected by crystal violet staining semi-quantitative method,OD560≤0.15 was in 8 strains of LH,0.150.20 in 7 strains respectively.The levels of minimal biofilm inhibitory concentration in norfloxacin,ofloxacin,levofloxacin,ciprofloxacin and lomefloxacin to LH were respectively higher than the minimal inhibitory concentration(MIC) in the corresponding floating bacteria(P<0.05).Among 55 strains of LH,18 strains were resistant to quinolones,the resistance rate was 32.7%,and the type I integron in 18 strains of LH carried the drug resistant genes,these drug resistant genes played the drug resistance role in corresponding bacterial strains.Conclusion Drug resistance gene formation and widespread of LH may be associated with type I integron.
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Objective To investigate the resistance mechanism of Pseudomonas aeruginosa PA902 by high -throughput sequencing.Method PA902 was sequenced by the Illumina Miseq platform,and sequencing data were analyzed by bioinformatic techniques.Results PA902 was resistant to all common clinical antibiotics except amikacin.Analysis of data reveal resistance genes to β-1actams (blaOXA-10,blaPER-1 和 blaVIM-2),aminoglycosides (aph (3 ‘)-Ⅱd,aac (6')-Ⅰb-cr,aacA4 和 aadA2),sulfonamides (sul1),tetracyclines (tetG),chloramphenicol (floR).Several putative chromosome-located resistance genes were also identified.The results were fully in accordancc with thc susceptibility results.Sequence analysis of the contigs containing resistance genes revealed that they were always clustered on the same contig and correlated mobilization sequences.MLST identified PA902 as ST389,which was first reported in China.Conclusion High throughput sequencing demonstrated the molecular resistance mechanism of PA902,and the findings were in accordance with the susceptibility results.The technique will provide solid support for the traditional clinical microbiology methods.
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Objective To assess the value of T?SPOT.TB test in the diagnosis of active tuberculosis. Methods The clinical data of 975 hospitalized patients receiving T?SPOT.TB test were collected in our hospital. The clinical information and testing results were analyzed. The receiver operating curve (ROC) was used to determine the optimal threshold of T?SPOT.TB test for differentiating active tuberculosis. Results T?SPOT.TB test results showed that the positive rate was 29.26%for the non?active tuberculosis group(n=793),but was 91.21%for active tuberculosis patients group (n = 182),which indicated that the test had a significant value in active tuberculosis detection(P<0.001). The sensitivity of T?SPOT.TB test was 0.912 and the specificity was 0.707. The detection threshold of T?SPOT.TB was optimized. As the spot?forming count(sfc)of ESAT?6 antigen threshold was 11.5 and that of the CEP?10 threshold was 9.5,the efficiency of T?SPOT.TB test for detection of active pulmonary tuberculosis was the highest. Conclusions T?SPOT.TB test has a good diagnostic performance for active tuberculosis, and it can be further optimized to better serve the clinical practice.
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Objective To investigate the class I integrons and their gene cassettes of imipenem-resistant Pseudomonas aeruginosa (IRPA) , and to analyze the correlation between integrons and drug resistance. Methods PCR was used to determine the presence of integrase genes and class I integrons. The variable regions were detected by sequencing. Resistance genes of integron gene cassettes including metal-β-lactamases, aminoglycoside modifying enzymes (AMEs), 16SrRNA methylating enzyme and the OprD2 genes were detected by PCR. The VITEK-2 automated system was used to determine the antibiotic susceptibility of integron-positive IRPA strains. Results The positive rates of integrase genes and class I integrons were 23.3%(20/86)and 8.14%(7/86) , and five kinds of gene cassettes were detected in 86 IRPA strains. The class I integrons-positive bacterial strains exhibited different resistant patterns to 12 antibiotics with large number of resistance genes. Conclusion The class I integrons and their gene cassettes are associated with multiple drug resistance of IRPA.
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Objective To investigate the method of the separation gel vacuum tube combined with matrix‐assisted laser desorp‐tion/ionization time of flight mass spectrometry system (VITEK‐MS) for fasting identifying positive blood culture bacteria .Methods Fifty cases of positive blood culture by the BacT/ALERT3D blood culture system and Gram‐negative bacteria by direct staining in the First Affiliated Hospital of Guangzhou University from March to October 2015 were collected .The bacteria were directly ex‐tracted from the blood culture bottle by the separation gel tube and performed the fast identification by adopting the VITEK‐MS system .At the same time the bacteria were performed the subcultivation and identification .then the coincidence of this method was compared .Results Among 50 cases of Gram‐negative bacteria by positive blood culture ,21 cases of bacteria were not identified ,29 cases of bacteria were identified ,the positive rate was 58 .0% .the coincidence rate with the conventional identification results was 96 .6% ;the method of separation gel combined with VITEK‐MS was nearly 24 h in advance compared with the traditional method . Conclusion Adopting the separation gel vacuum tube combined with VITEK‐MS for identifying bacteria has the higher coincidence rate of positive blood culture Gram negative bacteria ,can greatly shorten the identification time ,this method is rapid and simple .
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Objective To investigate the relationship between the resistance of the Klebsiella pneumoni-ae and the Klebsiella pneumoniae plasmid pNDM-LJ carrying blaNDM-1 by high-throughput DNA sequencing. Methods High-throughput DNA sequencing was carried out by the Illumina Miseq platform , and sequencing data were assembled by Edena software. Contigs were annotated by the RAST server and analyzed by the BLAST server. Results The plasmid pNDM-LJ was 54-kb in size with a GC content of 49%. The plasmid encoded 52 putative functional genes and belonged to the IncX3 group in incompatible classifications. Analysis of the plasmid sequence revealed high similarity with other IncX3 plasmids. The blaNDM-1 gene was located in a complicated gene environment possibly constructed by several transposition events. The 5′ and 3′ ends of the blaNDM-1 gene were adjacent to the ISAba125 and IS 26 respectively , forming a 10.8-kb transposon-like structure. Conclusion The plasmid pNDM-LJ carried the blaNDM-1 gene being resistant to carbapenems and played a possibly impor-tant role in transmission of blaNDM-1 in China.
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Objectives To investigate the prevalance of quinolone resistance in Laribacter hongkongensis and to evaluate the influence of agar dilution and disc diffusion methods on susceptibility testing for the bacterium. Methods Susceptibility to quinolones of L.hongkongensis was tested by agar dilution and disc diffusion methods. The results for both methods were compared. Results L.hongkongensis isolates exhibited different susceptibility rate for quinolones (levofloxacin>ciprofloxacin>norfloxacin>nalidixic acid). All of the fish isolates were susceptible to levofloxacin and more than 90%were susceptible to ciprofloxacin and Norfloxacin. However,by agar dilution, only 62.50%, 37.50%,48.21%, 19.64%of the frogs isolates were susceptible to levofloxacin, norfloxacin, ciprofloxacin, nalidixic acid, respectively. For fish isolates, comparision of susceptibilities between agar dilution and disc diffusion showed a high (> 95%) percentage agreement for levofloxacin and ciprofloxacin and the highest crepancies were observed with norfloxacin (100%) .But it showed a high discrepancy when comparing the two methods for frogs isolates. Conclusions The resistance rate of L. hongkongens to quinolones was high , especially for frog isolates. The results suggested the use of agar dilution on susceptibility testing for quinolones in L. hongkongensis.