46 VITRIFICATION AT THE GERMINAL VESICLE STAGE TRIGGERS PRECOCIOUS MEIOTIC RESUMPTION BUT DOES NOT AFFECT CYTOPLASMIC MATURATION IN CUMULUS-ENCLOSED PORCINE OOCYTES DURING IN VITRO MATURATION

Previously we have reported a vitrification protocol that allows preservation of immature porcine oocytes in large numbers (Somfai et al. 2014 PLoS One 9, e97731). However, despite high survival rates, embryo development rates have remained low. The aim of our current research is to reveal factors potentially responsible for reduced developmental competence of vitrified oocytes. As a first step, we investigated the effects of vitrification at the germinal vesicle stage on subsequent nuclear progression and the normality of cytoplasmic functions during in vitro maturation (IVM). Cumulus-enclosed porcine oocytes were vitrified in microdrops, stored, and then warmed by our method (Somfai et al. 2015 Reprod. Fertil. Dev. 27, 124). Then the oocytes were subjected to IVM for 46 h in a chemically defined porcine oocyte medium. During the first 22 h of IVM, the medium was supplemented with 1 mM dibutyryl cyclic adenosine monophosphate, 10 IU mL–1 of eCG, and 10 IU mL–1 of hCG. The following 24 h of IVM was performed in porcine oocyte medium without any supplementation. We compared vitrified/warmed oocytes (vitrified group) with freshly collected immature oocytes (control group) in terms of (1) nuclear progression, (2) intracellular glutathione (GSH), and (3) adenosine triphosphate levels throughout IVM. Each experiment was replicated at least 3 times. Results were analysed by one-way ANOVA and Tukey’s multiple comparison test. A total of 510 oocytes were vitrified of which 422 (82.3%) survived. Only live oocytes were subjected to subsequent assays. Orcein staining revealed that after 22 h of IVM, a significantly higher percentage (P < 0.05) of vitrified oocytes showed germinal vesicle breakdown compared with the control group (22.0 v. 0.9%, respectively). In a similar fashion, after 30 h IVM, a significantly higher (P < 0.05) percentage of oocytes reached the metaphase-II (MII) stage in the vitrified group than in the control group (21.8 v. 0%, respectively). After 46 h of IVM, there was no difference between the vitrified and control groups in terms of the percentage of MII stage oocytes (93.9 and 86.3%, respectively). Analysis of GSH levels in oocytes by the 5,5′-dithio-bis-2-nitrobenzoic acid-glutathione disulfide reductase recycling assay showed no significant difference between the vitrified and control groups at 0 h (6.7 and 7.0 pmol, respectively), 22 h (5.5 and 5.5 pmol, respectively), and 46 h (6.9 and 7.9 pmol, respectively) of IVM. Adenosine triphosphate assay (FL-ASC; Sigma-Aldrich Co., St. Louis, MO) revealed similar adenosine triphosphate contents in the oocytes of the vitrified and control groups at 0 h (1.53 and 1.61 pmol, respectively), 22 h (1.67 and 1.70 pmol, respectively), and 46 h (1.65 and 1.83 pmol, respectively) of IVM. In conclusion, vitrification triggered precocious nuclear maturation even in the presence of dibutyryl cyclic adenosine monophosphate; however, it did not affect GSH levels and overall metabolism. This work was supported by JSPS KAKENHI (Grant Number: 26870839) and JST/JICA SATREPS.

47 EFFECT OF L-CARNITINE TREATMENT DURING OOCYTE MATURATION ON THE POST-THAW DEVELOPMENT OF PORCINE EMBRYOS VITRIFIED AT THE PRONUCLEAR STAGE

The extreme cryo-sensitivity of porcine oocytes and embryos is attributed to their endemically high content of cytoplasmic lipid droplets. In attempts to improve the cryo-tolerance of porcine embryos, various strategies have been used to reduce the amount of lipid droplets present in the cytoplasm before vitrification. Recently, the cryo-tolerance of bovine oocytes vitrified at the metaphase II stage was improved by supplementing in vitro maturation (IVM) medium with l-carnitine (LC), a stimulator of lipid metabolism (Chakitisakul et al. 2013 Theriogenology 79, 590–598). The objective of this study was to determine the effect of supplementing IVM medium with LC on the post-thaw development of porcine embryos vitrified at the pronuclear stage. Oocytes recovered from the ovaries of prepubertal gilts were matured in modified porcine oocyte medium supplemented with 0 (control) or 12 mM LC during the final 22 h of IVM. Following IVF, presumptive zygotes were cultured in porcine zygote medium-3. At the pronuclear stage, cohorts of embryos from each group were either vitrified using a solid surface vitrification procedure (Somfai et al. 2009 Biol. Reprod. 80, 42–49) or cultured for 7 d without being vitrified. Vitrified zygotes were subsequently warmed and cultured for 7 d. The rates of cleavage, blastocyst formation, and hatching were recorded, and all blastocysts were stained to determine the total cell numbers. Three replicates were performed. Proportional data were arcsine transformed and subjected to ANOVA, and cell number data were analysed by t-test. The post-thaw survival rates of the embryos that were vitrified did not differ between the groups (control: 95.7%; LC: 97.1%; P > 0.05). There were no significant effects of LC treatment or vitrification on the rates of cleavage, blastocyst formation, and hatching (Table 1). Vitrified embryos derived from LC-treated oocytes produced blastocysts with fewer cells than vitrified embryos derived from untreated oocytes (Table 1; P < 0.05). In contrast to previous findings in other species, the results indicate that supplementing IVM medium with LC did not enhance the post-thaw development of porcine embryos vitrified at the pronuclear stage. Table 1.Effect of l-carnitine (LC) treatment and vitrification on porcine embryo development C. Grupen was supported by an OECD Fellowship.

MR Imaging-Based Analysis of Glioblastoma Multiforme: Estimation of IDH1 Mutation Status

BACKGROUND AND PURPOSE

Glioblastoma multiforme is highly aggressive and the most common type of primary malignant brain tumor in adults. Imaging biomarkers may provide prognostic information for patients with this condition. Patients with glioma with isocitrate dehydrogenase 1 (IDH1) mutations have a better clinical outcome than those without such mutations. Our purpose was to investigate whether the IDH1 mutation status in glioblastoma multiforme can be predicted by using MR imaging.

MATERIALS AND METHODS

We retrospectively studied 55 patients with glioblastoma multiforme with wild type IDH1 and 11 patients with mutant IDH1. Absolute tumor blood flow and relative tumor blood flow within the enhancing portion of each tumor were measured by using arterial spin-labeling data. In addition, the maximum necrosis area, the percentage of cross-sectional necrosis area inside the enhancing lesions, and the minimum and mean apparent diffusion coefficients were obtained from contrast-enhanced T1-weighted images and diffusion-weighted imaging data. Each of the 6 parameters was compared between patients with wild type IDH1 and mutant IDH1 by using the Mann-Whitney U test. The performance in discriminating between the 2 entities was evaluated by using receiver operating characteristic analysis.

RESULTS

Absolute tumor blood flow, relative tumor blood flow, necrosis area, and percentage of cross-sectional necrosis area inside the enhancing lesion were significantly higher in patients with wild type IDH1 than in those with mutant IDH1 (P < .05 each). In contrast, no significant difference was found in the ADC(minimum) and ADC(mean). The area under the curve for absolute tumor blood flow, relative tumor blood flow, percentage of cross-sectional necrosis area inside the enhancing lesion, and necrosis area were 0.850, 0.873, 0.739, and 0.772, respectively.

CONCLUSIONS

Tumor blood flow and necrosis area calculated from MR imaging are useful for predicting the IDH1 mutation status.

62 COMPARISON OF SUGARS, COMBINATIONS OF PERMEABLE CRYOPROTECTANTS, AND EQUILIBRATION REGIMENS FOR THE SOLID SURFACE VITRIFICATION OF IMMATURE PORCINE OOCYTES

Cryotop and solid surface vitrification are frequently used methods for the cryopreservation of porcine oocytes. These methods differ not only in the vitrification carrier but also in the cryoprotectant (CPA) treatment including the type of sugar, permeable CPA (pCPA) combinations, and the equilibration regimen. This study compared the distinct points of CPA treatment of these 2 methods to determine the optimum CPA treatment for the solid surface vitrification of immature porcine oocytes. We vitrified and warmed follicular cumulus-oocyte complexes by our method (Somfai et al. 2014 PLoS One 9, e97731). In each experiment, the vitrification solution consisted of 50 mg mL–1 polyvinyl pyrrolidone, 0.3 M of the actual sugar, and 35% [v/v] in total of the actual pCPA combination (depending on the experiment). After warming, the cumulus-oocyte complexes were subjected to in vitro maturation, IVF, and embryo culture (Kikuchi et al. 2002 Biol. Reprod. 66, 1033–1041). Oocyte survival was assessed after IVF by morphological evaluation, and live oocytes were subjected to in vitro embryo culture. Cleavage and blastocyst rates were calculated from cultured oocytes on Day 2 (Day 0 = IVF) and Day 6, respectively. Each experiment was replicated at least 3 times. Results were analysed by ANOVA. In Experiment 1, we compared trehalose (n = 416) and sucrose (n = 440) as supplementations during vitrification and warming (0.3 M and 0.4 M of each, respectively). There was no significant difference between oocytes vitrified with trehalose or sucrose in terms of survival, cleavage, and blastocyst development (83.2% v. 80.3%, 39.7% v. 42.4%, and 3.6% v. 5.9%, respectively). Thus, vitrification and warming media were supplemented with sucrose thereafter. In Experiment 2, we compared 1 : 1 combinations of ethylene glycol with propylene glycol (EG+PG group, n = 452) and ethylene glycol with dimethyl sulfoxide (EG+DMSO group, n = 465) used as pCPA for equilibration (4% [v/v] pCPA in total for 15 min) and vitrification (35% [v/v] pCPA in total for 30 s). Oocyte survival rate was higher (P < 0.05) in the EG+PG group compared with the EG+DMSO group (73.8% v. 51.1%, respectively); however, cleavage and blastocyst development rates of surviving oocytes were not significantly different between the 2 groups (30.5% v. 44.5% and 4.1% v. 6.3%, respectively). In Experiment 3, we compared an equilibration treatment in 4% [v/v] of EG+PG for 13 to 15 min (regimen A, n = 368) with an equilibration in 15% [v/v] of EG+PG for 5 to 7 min (regimen B, n = 363) for oocyte vitrification. Survival, cleavage, and blastocyst development rates were higher (P < 0.01) for oocytes vitrified using regimen A compared with those vitrified using regimen B (82.5% v. 22.7%, 24.0% v. 7.7%, and 3.2% v. 0%, respectively). In conclusion, trehalose and sucrose are equally effective during vitrification and warming, the combination of EG+PG as pCPA is superior to EG+DMSO, and equilibration in 4% pCPA for 13 to 15 min is superior to that in 15% pCPA for 5 to 7 min for the vitrification of immature porcine oocytes.This work was partly supported by JSPS KAKENHI Grant Number 26870839.

296 IMPACT OF CO-CULTURING CUMULUS-ENCLOSED PORCINE OOCYTES WITH DENUDED OOCYTES DURING IN VITRO MATURATION IN A DEFINED MEDIUM ON CUMULUS EXPANSION AND OOCYTE MATURATION

Recent research has revealed that oocyte-secreted factors (OSF) affect cumulus expansion and play important roles during maturation and embryo development of mammalian oocytes. The use of denuded oocytes (DO) as supplements during in vitro maturation (IVM) in a nondefined medium improved developmental competence of cumulus-enclosed porcine oocytes (COC; Gomez et al. 2012 Zygote 20, 135–145). We investigated the effect of DO on cumulus expansion and nuclear maturation of COC in pigs during IVM using a defined medium. If the DO exert a positive influence on IVM, the defined medium can then be analysed for the presence of OSF. Immature COC were collected in the slaughterhouse from prepubertal gilts. To obtain DO, some COC were completely denuded by pipetting through a narrow-bore glass pipette. The COC used as a source for DO fulfilled the same morphological criteria as the COC used for IVM. The IVM medium was porcine oocyte medium (POM; Yoshioka et al. 2008 J. Reprod. Dev. 54, 208–213) with hormone supplementations applied only during the first 20 h of the IVM period. The COC were fixed to the bottom of 35-mm plastic Petri dishes in 3 × 3 grids by Cell-Tak (BD Bioscience, Bedford, MA, USA) in 100-µL droplets POM covered by paraffin oil. Culture droplets (each including 1 COC grid) were supplemented with (DO+ group, n = 179) or without 16 DO (DO– group, n = 143). After 20 h of IVM, the medium was replaced with a preincubated hormone-free POM and oocytes were cultured for an additional 28 h. At 0, 20, and 48 h of IVM, images of each grid were taken at the same magnification. The size of each COC was measured as a 2-dimensional area in pixels by analysing images with ImageJ software. Relative cumulus expansion was calculated at 20 and 48 h of IVM on the basis of the initial COC size at 0 h, which was assigned as 1. At 48 h of IVM, the COC were denuded and examined for oocyte maturation by orcein staining. The experiment was replicated 5 times. Cumulus expansion ratios at 20 and 48 h of IVM were compared between the DO+ and DO– groups by ANOVA. Maturation rates were compared between the DO+ and DO– groups by binary logistic regression. No difference in cumulus expansion between DO– and DO+ could be observed at 20 h (1.83 ± 0.04 and 1.75 ± 0.03, respectively) and 48 h (1.41 ± 0.03 and 1.47 ± 0.02, respectively) of IVM. Nuclear maturation rates of COC in DO– and DO+ groups did not differ significantly (39.0 ± 5.4 and 32.9 ± 8.8%, respectively). In conclusion, addition of DO to the defined IVM medium did not affect the cumulus expansion and oocyte maturation of follicular porcine COC. Further research is needed to assess the effects of DO during IVM on subsequent fertilization. If DO prove to be beneficial for fertilization, the nature of the OSF will be investigated.This study was supported by FCWO of UGent and by FWO-Flanders (grant number FWO11/ASP/276).

61 THE EFFECTS OF COLLECTION SEASON AND STORAGE DURATION IN LIQUID NITROGEN ON POST-WARMING SURVIVAL AND NUCLEAR MATURATION OF IMMATURE PORCINE OOCYTES PRESERVED BY SOLID SURFACE VITRIFICATION

We investigated the effects of collection season and storage duration of vitrified porcine oocytes in liquid nitrogen (LN2) on their survival and maturation ability after warming. A total of 3338 cumulus-enclosed oocytes were vitrified using solid surface vitrification, preserved, and warmed according to previous report (Somfai et al. 2014 PLoS One 9, e97731) in 26 occasions between October 2012 and March 2014. Vitrified oocytes were stored in LN2 for various durations from 0 (vitrified but without storage) to 243 days. The date of preservation and length of storage (days) of vitrified oocytes in LN2 were recorded. Warming of vitrified oocytes was conducted on a hotplate set at 42°C. After warming, oocytes were subjected to in vitro maturation according to Kikuchi et al. (2002 Biol. Reprod. 66, 1033–1041). Then oocytes were denuded and their live/dead status and nuclear maturation were assessed under stereo microscope based on their morphology and the presence of the first polar body. After linear regression analysis, it was found that there was no correlation between the duration of storage of vitrified oocytes in LN2 for up to 243 days and their survival rate after warming (R = 0.254; P = 0.210) or the maturation rate of surviving oocytes (R = 0.147; P = 0.471). Vitrification during spring (March 1–May 31) resulted in significantly higher rates of survived oocytes compared with vitrification during winter (December 1–February 28; 86.9 and 73.1%, respectively; P < 0.05), whereas the mean survival rates of oocytes vitrified during summer (June 1–August 31; 79.0%) and autumn (September 1–November 31; 81.9%) did not differ significantly from those of other seasons (ANOVA). After in vitro maturation, nuclear maturation of surviving oocytes did not differ significantly among oocytes vitrified at different seasons (ranging between 59.1 and 67.8%). The results indicate that the oocyte collection season affects survival of vitrified oocytes, whereas storage duration in LN2 does not affect this parameter. Furthermore, nuclear maturation of oocytes that survive after vitrification and warming is not affected by their collection season and storage length.This work was supported by JSPS KAKENHI Grant Number 26870839.

Lymphaticovenular anastomosis to prevent cellulitis associated with lymphoedema

BACKGROUND

One of the complications of lymphoedema is recurrent cellulitis. The aim was to determine whether lymphaticovenous anastomosis (LVA) was effective at reducing cellulitis in patients with lymphoedema.

METHODS

This was a retrospective review of patients with arm/leg lymphoedema who underwent LVA. The frequency of cellulitis was compared before and after surgery. The diagnostic criteria for cellulitis were a fever of 38·5°C or higher, and warmth/redness in the affected limb(s).

RESULTS

A total of 95 patients were included. The mean number of episodes of cellulitis in the year preceding surgery was 1·46, compared with 0·18 in the year after surgery (P < 0·001).

CONCLUSION

LVA reduced the rate of cellulitis in these patients with lymphoedema.

Evaluation of diffusivity in the anterior lobe of the pituitary gland: 3D turbo field echo with diffusion-sensitized driven-equilibrium preparation

BACKGROUND AND PURPOSE

3D turbo field echo with diffusion-sensitized driven-equilibrium preparation is a non-echo-planar technique for DWI, which enables high-resolution DWI without field inhomogeneity-related image distortion. The purpose of this study was to evaluate the feasibility of diffusion-sensitized driven-equilibrium turbo field echo in evaluating diffusivity in the normal pituitary gland.

MATERIALS AND METHODS

First, validation of diffusion-sensitized driven-equilibrium turbo field echo was attempted by comparing it with echo-planar DWI. Five healthy volunteers were imaged by using diffusion-sensitized driven-equilibrium turbo field echo and echo-planar DWI. The imaging voxel size was 1.5 × 1.5 × 1.5 mm(3) for diffusion-sensitized driven-equilibrium turbo field echo and 1.5 × 1.9 × 3.0 mm(3) for echo-planar DWI. ADCs measured by the 2 methods in 15 regions of interests (6 in gray matter and 9 in white matter) were compared by using the Pearson correlation coefficient. The ADC in the pituitary anterior lobe was then measured in 10 volunteers by using diffusion-sensitized driven-equilibrium turbo field echo, and the results were compared with those in the pons and vermis by using a paired t test.

RESULTS

The ADCs from the 2 methods showed a strong correlation (r = 0.79; P < .0001), confirming the accuracy of the ADC measurement with the diffusion-sensitized driven-equilibrium sequence. The ADCs in the normal pituitary gland were 1.37 ± 0.13 × 10(-3) mm(2)/s, which were significantly higher than those in the pons (1.01 ± 0.24 × 10(-3) mm(2)/s) and the vermis (0.89 ± 0.25 × 10(-3) mm(2)/s, P < .01).

CONCLUSIONS

We demonstrated that diffusion-sensitized driven-equilibrium turbo field echo is feasible in assessing ADC in the pituitary gland.

157 LEUKEMIA INHIBITORY FACTOR IMPROVES OOCYTE MATURATION AND DEVELOPMENTAL COMPETENCE IN PIGS

A variety of growth factors and cytokines that are present in follicular fluid provide oocytes with a suitable environment for their maturation. One such cytokine is leukemia inhibitory factor (LIF). Although LIF-supplemented medium enhances embryo development in human, mouse, and bovine, studies investigating the effects of LIF on in vitro maturation (IVM) and subsequent embryo development are inconclusive. Additionally, the underlying mechanisms of LIF in oocyte maturation and embryo development after IVF have not been studied yet. In the present study, we examined the effect of recombinant porcine LIF (pLIF), produced in our laboratory, on porcine oocyte maturation and the mechanism of how LIF involves in oocyte maturation process at molecular level. The biological activity of pLIF was evaluated by sustenance of mouse embryonic stem (ES) cells with an undifferentiating state in ES medium supplemented with pLIF, and the final concentration (1 : 200, equivalent to 1000 U mL–1 of mouse LIF) was determined by serial dilution. Porcine cumulus–oocyte complexes (COC) were cultured in modified NCSU-37 medium supplemented with pLIF during the first 22 h [pLIF (+, –)], the latter 22 h [pLIF (–, +)], or whole 44 h [pLIF (+, +)] of IVM and the proportion of metaphase II (M-II) stage oocytes was observed. Oocyte maturation was enhanced in each group by supplementation with pLIF [pLIF (+, –): 76.1%, n = 138; pLIF (–, +): 82.1%, n = 140; pLIF (+, +): 86.6%, n = 127], when compared with control [pLIF (–, –): 69.6%, n = 112], in which a significant increase of M-II rate (P < 0.05 by ANOVA) and cumulus expansion were observed in the pLIF (+, +) group. The effect of pLIF was only seen for COC but not for denuded oocytes. When oocytes were subjected to IVF (Kikuchi et al. 2002), those matured in pLIF (+, +)-supplemented medium demonstrated higher blastocyst developmental rates (21.1% v. 16.2%; P = 0.07) with increased cell numbers (50.2 cells v. 45.0 cells; P = 0.12) compared with pLIF (–, –) on Day 6 of embryo culture (IVF = 0). Examination of transcripts and proteins of the LIF signalling pathway revealed that mRNA and protein levels of LIF, LIF receptors, and signal transducer and activator of transcription 3 (STAT3) were similar in both pLIF (–, –) and pLIF (+, +) samples. However, notable phosphorylation of STAT3 was observed in the pLIF (+, +) sample. These results suggest that the LIF/STAT3-pathway is functional during oocyte maturation in pigs. Therefore, supplementation of maturation medium with pLIF could improve the developmental competence of oocytes by activation of this pathway. This project was supported by JSPS and HAS under the Japan-Hungary Research Cooperative Program.

44 PRODUCTION OF LIVE PIGLETS AFTER CRYOPRESERVATION OF IMMATURE PORCINE OOCYTES

Development to term of vitrified porcine follicular oocytes is reported in the present study. Immature cumulus-oocyte complexes (COC) were collected from slaughtered prepubertal gilts and were vitrified according to our method published recently (Somfai et al. 2013 J. Reprod. Dev., in press). Briefly, after pretreatment with 7.5 μg mL–1 of cytochalasin B (CB) for 30 min in modified NCSU-37 (a basic medium, BM) at 38.5°C, groups of 88 to 121 COC were equilibrated in a mixture of 2% ethylene glycol (EG), 2% propylene glycol (PG), and 7.5 μg mL–1 CB for 13 to 15 min. Then, COC were washed in vitrification solution (17.5% EG, 17.5% PG, 5% polyvinyl pyrrolidone, and 0.3 M trehalose in BM) and then dropped with 2 μL of vitrification solution onto the surface of aluminum foil floating on liquid nitrogen (LN2). Microdroplets (each containing 10–25 COC) were transferred into cryotubes. After storage in LN2 for 2 to 4 weeks, the oocytes were warmed by dropping the microdroplets directly into 2.5 mL of warming solution (0.4 M trehalose in BM) kept in a 35-mm Petri dish on a 42°C hotplate for less than 1 min. Then, the warming dish was placed on a 38°C hotplate and COC were consecutively transferred for 1-min periods into BM containing 0.2, 0.1, or 0.05 M trehalose at 38°C. The COC were matured in vitro for 44 h using porcine oocyte medium (POM) supplemented with 10% follicular fluid (Yoshioka et al. 2008 J. Reprod. Dev. 54, 208–213). Then, oocytes were denuded, and their live/dead status and nuclear maturation were determined by their morphology and the presence of the first polar body, respectively. To assess their developmental competence, vitrified and non-vitrified (control) oocytes were in vitro fertilized (IVF; Kikuchi et al. 2002 Biol. Reprod. 66, 1033–1041) and then in vitro cultured in porcine zygote medium-5 (PZM-5; Yoshioka et al. 2008 J. Reprod. Dev. 54, 208–213). Blastocyst rates were recorded on Days 5, 6, and 7 of culture (Day 0 = the day of IVF). The experiment was replicated 4 times. Data were analysed with 1-way ANOVA and the Tukey test. The results revealed that 86.4% (364/424) of oocytes survived after vitrification, which was significantly lower (P < 0.05) than that of controls [100% (326/326)]. Live oocytes in vitrified and control groups did not differ statistically in terms of nuclear maturation (63.9 v. 65.3%). Blastocyst rates of surviving vitrified oocytes were significantly lower compared with controls on Days 5 (2.4 v. 12.7%), 6 (4.8 v. 17.6%), and 7 (5.6 v. 18.4%). To test their ability to develop to term, 16 and 27 blastocysts on Day 5 developing from vitrified COC were transferred into 2 recipients. Both recipients became pregnant and farrowed a total of 10 live piglets (4 and 6 piglets, respectively). These data demonstrate that large groups of immature porcine oocytes could be cryopreserved by this method showing high survival and maturation rates. Furthermore, despite a low rate of blastocyst development, transfer of Day-5 blastocysts generated from vitrified oocytes resulted in piglet production for the first time in the world. Partially supported by JSPS and HAS under the Japan-Hungary Research Cooperative Program.

Evaluation of matrix-assisted laser desorption ionization-time of flight mass spectrometry for species identification of Acinetobacter strains isolated from blood cultures

The clinical relevance of Acinetobacter species, other than A. baumannii, as human pathogens has not been sufficiently assessed owing to the insufficiency of simple phenotypic clinical diagnostic laboratory tests. Infections caused by these organisms have different impacts on clinical outcome and require different treatment and management approaches. It is therefore important to correctly identify Acinetobacter species. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been introduced to identify a wide range of microorganisms in clinical laboratories, but only a few studies have examined its utility for identifying Acinetobacter species, particularly those of the non-Acinetobacter baumannii complex. We therefore evaluated MALDI-TOF MS for identification of Acinetobacter species by comparing it with sequence analysis of rpoB using 123 isolates of Acinetobacter species from blood. Of the isolates examined, we identified 106/123 (86.2%) to species, and 16/123 (13.0%) could only be identified as acinetobacters. The identity of one isolate could not be established. Of the 106 species identified, 89/106 (84.0%) were confirmed by rpoB sequence analysis, and 17/106 (16.0%) were discordant. These data indicate correct identification of 89/123 (72.4%) isolates. Surprisingly, all blood culture isolates were identified as 13 species of Acinetobacter, and the incidence of Acinetobacter pittii was unexpectedly high (42/123; 34.1%) and exceeded that of A. baumannii (22/123; 17.9%). Although the present identification rate using MALDI-TOF MS is not acceptable for species-level identification of Acinetobacter, further expansion of the database should remedy this situation.