Effects of different culture media and pretreatment methods on the results of MALDI-TOF mass spectrometry for the identification of Vibrio parahaemolyticus / 临床检验杂志

ABSTRACT

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 level100％;species level67.5％),followed by the combination of double wash agar plate with the extraction method(genus level70％;species level37.5％).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(asmear method;bextension method;cTCBS agar plate;ddouble 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(asmear method;bextension method;cTCBS agar plate;ddouble 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.