RESUMO
Objective To investigate the effects of different culture media and pretreatment methods on the results of matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF MS) for the identification of Vibrio parahaemolyticus,and then provide the optimal conditions.Methods Forty strains of Vibrio parahaemolyticus were collected,and subcultured with the blood agar plate,thiosulfate citrate bile salts sucrose(TCBS) agar plate and double wash agar plate,respectively.The pretreatment methods before mass spectrometry included the smear method,extension method and extraction method.The effects of different culture media and pretreatment methods on the results of MALDI-TOF MS for the identification of Vibrio parahaemolyticus were analyzed by the logistics regression model and Chi-square test of SAS software.Results The detection rate of Vibrio parahaemolyticus was the highest in the combination of blood agar plate with the extraction method(genus level:100％;species level:67.5％),followed by the combination of double wash agar plate with the extraction method(genus level:70％;species level:37.5％).For the genus identification level of Vibrio parahaemolyticus,when the pretreatment method was the same,different culture media produced significantly different detection rates(P ＜ 0.01).However,when the culture medium was the same,there was no significant difference in detection rates for different pretreatment methods (P ＞ 0.05).The odd ratios (OR) of the smear method and extention method relative to the extraction method were 0.66 and 0.95,respectively,and there was no significant difference in detection rates for them(P ＞ 0.05),while the ORs of the TCBS agar plate and double wash agar plate relative to blood agar plate were 0.06 and 0.10,respectively,and there was significant difference in detection rates for them(P ＜0.05).The logistic regression equation was Y=2.95-0.41a-0.05b-2.83c-2.83d(a:smear method;b:extension method;c:TCBS agar plate;d:double wash agar plate).For the species identification level of Vibrio parahaemolyticus,when the extension method or the extraction method was used,different culture media produced significantly different detection rates(P ＜ 0.05).When the blood agar plate was used,different pretreatment methods also produced significantly different detection rates(P ＜ 0.01).The ORs of the smear method and extention method relative to the extraction method were 0.32 and 0.55,respectively,and there was significant difference in detection rates for them (P ＜ 0.05),while the ORs of the TCBS agar plate and double wash agar plate relative to blood agar plate were 0.18 and 0.49,respectively,and there was significant difference in detection rates for them(P ＜0.05).The logistic regression equation was Y =0.20-1.15a-0.61b-1.72c-1.72d(a:smear method;b:extension method;c:TCBS agar plate;d:double wash agar plate).Conclusion For improving the detection rate of Vibrio parahaemolyticus by MALDI-TOF MS,the selection of appropriate culture medium is more important than that of the pretreatment method.It is recommended that the extraction method may be as a conventional pretreatment method,and that the optimal medium is the blood agar plate,followed by the double wash agar plate and TCBS agar plate.
RESUMO
Objective To analyze the antimicrobial resistance profile of clinical isolates in Shanghai Xinhua Hospital Chongming Branch affiliated to Shanghai Jiaotong University School of Medicine , a member of China Antimicrobial Resistance Surveillance System, during 2015, for the purpose to facilitate rational antimicrobial therapy. Methods Strain identification?and?susceptibility?testing?were?carried?out?for?the?clinical?isolates?using?MicroScan?WalkAway?96?Automated?Systems and Kirby-Bauer method. Results In 2015, a total of 1815 isolates were collected, including gram-negative bacteria (73.2 %) and gram-positive bacteria (26.8 %). The top three frequently isolated species were Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. ESBL-producing strains were found in 36.3 % of the Escherichia coli isolates, 12.6 % of the Klebsiella (K. pneumoniae and K. oxytoca) isolates, and 28.0 % of the Proteus mirabilis isolates. The prevalence of carbapenem-resistant strains was 0.69 % in Enterobacteriaceae isolates. The prevalence of methicillin-resistant strain was 29.1 % in S. aureus, and 61.4 % in coagulase-negative Staphylococcus isolates. No more than 15 % of the Enterobacteriaceae isolates and no more than 20 % of the P. aeruginosa and Acinetobacter isolates were resistant to carbapenems. No vancomycin-or linezolid-resistant strains were found in Enterococcus or Staphylococcus. Conclusions Antibiotic-resistant clinical isolates are a serious threat for clinical antimicrobial treatment. We should pay more attention to such urgent situation and rational use of antibiotics.