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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.
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OBJECTIVE@#To investigate whether the level of homocysteine in patients with postpartum depression is associated with depression index.@*METHODS@#A total of 43 women with postpartum depression or with potential postpartum depression, who visited the psychological clinic of Maternal and Child Health Hospital of Hunan Province from June, 2012 to April, 2014, were enrolled in this study. They were evaluated by the Edinburgh Postnatal Depression Scale and Hamilton Depression Scale. Chinese Classification of Mental Disorder (the third edition) was used for their diagnosis. The depressive index was calculated by Edinburgh Postnatal Depression Scale, Hamilton Depression Scale, and clinical symptom scores, which was used to assess the level of depressive symptoms. The level of homocysteine in serum was detected by chemoluminescent method. Meanwhile, another 31 women, who visited the hospital without postpartum depression, were used as controls to compare with the 43 patients.@*RESULTS@#The homocysteine level in the women with postpartum depression was significantly higher than that in the control group [(10.09 ± 3.59) μmol/L vs (8.57 ± 1.59) μmol/L, t=12.392, P=0.001]. The depression index was positively correlated with the level of homocysteine (r=0.231, P<0.05).@*CONCLUSION@#The level of serum homocysteine is associated with postpartum depression, suggesting that the level of serum homocysteine might be a risk biomarker for postpartum depression.