Makiko Kiyosuke

Clonal spread in Eastern Asia of ciprofloxacin-resistant Escherichia coli serogroup O25 strains, and associated virulence factors

A significant problem in the field of infectious diseases is the increase in fluoroquinolone (FQ)-resistant Escherichia coli. Although mutation of strains and clonal dissemination are supposed to be the cause of this increase, little is known about the prevalence of this organism. We investigated 219 FQ-resistant E. coli strains in Japan and nine Asian countries by serotyping and genotyping. Seventy-one strains (32.4%) were serogroup O25, which was prevalent in South Korea, China and Japan, especially in the southwest part of Japan. Aerobactin, a virulence factor in uropathogenic and avian pathogenic E. coli, was associated with the presence of FQ-resistant O25 strains of E. coli. Seven of the seventy-one FQ-resistant E. coli O25 had extended-spectrum beta-lactamase genes (six CTX-M-14 and one SHV-12), however, we were unable to find any E. coli O25-ST131 clone that produced CTX-M-15, which was previously reported to have emerged across continents. These data demonstrate that a clonal group of FQ-resistant and virulent E. coli recently became prevalent at least in East Asia and suggest that this might become a public health problem because the strains may acquire resistance to other antimicrobial agents.

Geographic distribution of fluoroquinolone-resistant Escherichia coli strains in Asia.

Fluoroquinolone (FQ) resistance is usually caused by point mutations within the quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC and/or parE. However, little is known about the worldwide increase in FQ-resistant Escherichia coli or, more specifically, about the geographical distribution of QRDR mutations and the clonal spread of isolates. In this study, we analysed 68 FQ-resistant E. coli isolates from eight Asian countries using QRDR amino acid mutation patterns and examined their susceptibility to FQs. Of the isolates, 38% had mutations at S83 and D87 of GyrA and S80 of ParC (MM/-/M-/-) and 34% had mutations at S83 and D87 of GyrA, S80 of ParC and S458 of ParE (MM/-/M-/M). MIC(50) values (minimum inhibitory concentrations for 50% of the isolates) for isolates with at least mutation at S458 of ParE for ciprofloxacin and prulifloxacin were relatively higher than MIC(50) values of isolates without this mutation. Based on their geographic distribution and the QRDR mutation patterns, the isolates were divided into a common type in which the organisms were isolated from three or more countries, and a local type in which the isolates were from one or two countries. Mutation types at S83L and D87N in GyrA and S80I in ParC with no or another site in the QRDR were the most frequent among the FQ-resistant isolates, especially among the common type. Gene typing indicated that isolates in the common type were not similar between countries. These data suggest that the increase in FQ-resistant E. coli strains is mainly generated by mutations in the QRDR in each geographical area rather than through intercontinental spread.

A dramatic increase in the positive blood culture rates of Helicobacter cinaedi: the evidence of differential detection abilities between the Bactec and BacT/Alert systems

In our hospital, positive blood culture rates of Helicobacter cinaedi dramatically increased after introducing the Bactec system. A simulated culture model of H. cinaedi bacteremia demonstrated no positive signals using the BacT/Alert system, despite efficient growth in bottles. Clinically suspected H. cinaedi bacteremia should be monitored more closely when using the BacT/Alert system, preferably with subcultivation after 7days of incubation.

Comparison of two types of matrix-assisted laser desorption/ionization time-of-flight mass spectrometer for the identification and typing of Clostridium difficile.

Microflex LT (Bruker Daltonics) and VITEK MS (bioMérieux) are bacterial identification systems that are based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). For VITEK MS, two identification softwares, VITEK MS IVD (IVD) and SARAMIS (SARAMIS), are available. Microflex LT is equipped with MALDI Biotyper RTC software (Biotyper). Although the identification accuracy of each instrument has been compared for various bacteria, no detailed examination has been conducted for the identification accuracy of Clostridium difficile. In this report, we compared the three identification softwares for identification reproducibility in three ATCC C. difficile strains and identification accuracy in 50 clinical C. difficile isolates. The results showed 100, 91.7 and 100 % identification reproducibility accuracy of ATCC strains when examined by IVD, SARAMIS and Biotyper software, respectively. For the identification of the clinical isolates, all three softwares exhibited satisfactory identification accuracy of C. difficile. Among the 50 clinical isolates, seven showed identical toxin genotype corresponding to the exact ribotype. However, MALDI-TOF MS failed to identify them as the identical type. Based on the above results, we concluded that both types of MALDI-TOF MS reproducibly identified C. difficile; however, they are currently not suitable for typing of C. difficile clones.

Preserved in vivo reconstitution ability of PBSCs cryopreserved for a decade at -80 °C.

PBSC products for auto- and allografting can be cryopreserved in liquid nitrogen with controlled-rate freezing until their use. Alternatively, they can be stored at −80 °C in a mechanical chest freezer, but it remains to be clarified whether PBSCs can be stored for the long term. We evaluated viability and functions of PBSCs cryopreserved for more than 10 years with this simplified method. Although recovery rate and viability of CD34+ cells were significantly decreased, myeloid differentiation potential and in vivo reconstitution and self-renewal potential of CD34+ cells in a xenogeneic engraftment assay were maintained for more than 10 years. These results indicate that PBSCs can be stored at −80 °C for years. Although accumulation of clinical engraftment data is required to confirm our results, this simplified cryopreservation will thus meet the increasing worldwide demand for PBSC transplantation in a region with limited resources.

P051: Factors responsible for methicillin-resistant Staphylococcus aureus outbreak in the neonatal intensive care unit

We observed a high incidence of methicillin-resistant Staphylococcus aureus (MRSA) outbreaks in the neonatal intensive care unit (NICU) of Kyushu University Hospital in Japan from 2010 to 2012.

Molecular epidemiologic analysis of nosocomocal infection due to TEIC resistant MRSA strains

We performed epidemiologic study of 109 strains of methicillin resistant Staphylococcus aureus (MRSA) which were detected in our hospital. Of these strains, 6 strains showed resistant to Teicoplanin (TEIC) which MIC level were between 4 to 8microg/mL. All of them showed some phenotype, such as type II of coagulase, type A of enterotoxin, and were producing TSST-1. Genotype analysis by PFGE also showed that those strains ware identical. From analyzing the spreading rout of these TEIC resistant MRSA, we speculate that they first were in ICU ward, then spread all over the hospital carried by the stuff cross-working ICU and other units of hospital.