CosR (Campylobacter oxidative stress regulator; Cj0355c) is an OmpR-type response regulator essential for the viability of Campylobacter jejuni, a leading foodborne pathogen causing human gastroenteritis worldwide. Despite importance, the function of CosR remains completely unknown mainly because of cell death caused by its knockout mutation. To overcome this technical limitation, in this study, antisense technology was used to investigate the regulatory function of CosR by modulating the level of CosR expression. Two-dimensional gel electrophoresis (2DGE) was performed to identify the CosR regulon either by suppressing CosR expression with antisense peptide nucleic acid (PNA) or by overexpressing CosR in C. jejuni. According to the results of 2DGE, CosR regulated 32 proteins involved in various cellular processes. Notably, CosR negatively regulated a few key proteins of the oxidative stress response of C. jejuni, such as SodB, Dps, Rrc and LuxS, whereas CosR positively controlled AhpC. Electrophoretic mobility shift assay showed that CosR directly bound to the promoter region of the oxidative stress genes. DNase I footprinting assays identified 21-bp CosR binding sequences in the sodB and ahpC promoters, suggesting CosR specifically recognizes and binds to the regulated genes. Interestingly, the level of CosR protein was significantly reduced by paraquat (a superoxide generator) but not by hydrogen peroxide. Consistent with the overall negative regulation of oxidative stress defense proteins by CosR, the CosR knockdown by antisense rendered C. jejuni more resistant to oxidative stress compared to the wild type. Overall, this study reveals the important role played by the essential response regulator CosR in the oxidative stress defense of C. jejuni.

Cronobacter sakazakii is an opportunistic pathogen that actively invades host eukaryotic cells. To identify invasion factors responsible for the intestinal translocation of C. sakazakii, we constructed for the first time outer membrane protein X (OmpX) and A (OmpA) deletion mutants using the lambda Red recombination system. The ompX and ompA deletion mutants showed significantly reduced invasion of human enterocyte-like epithelial Caco-2 and human intestinal epithelial INT-407 cells, and significantly fewer mutant cells were recovered from the livers and spleens of rat pups. Furthermore, compared with intact target cells, the invasion and initial association potentials of the mutants increased at a rate similar to that of the wild type in tight-junction-disrupted target cells, suggesting that OmpX and OmpA are involved in basolateral invasion by C. sakazakii. This is the first report of C. sakazakii virulence determinants that are essential for basolateral invasion and that may be critical for the virulence of C. sakazakii.

CosR is an essential response regulator in

Campylobacter jejuni is a leading food-borne pathogen causing gastroenteritis in humans. Although OxyR is a widespread oxidative stress regulator in many Gram-negative bacteria, C. jejuni lacks OxyR and instead possesses the metalloregulator PerR. Despite the important role played by PerR in oxidative stress defense, little is known about the factors influencing perR expression in C. jejuni. In this study, a perR promoter-lacZ fusion assay demonstrated that iron significantly reduced the level of perR transcription, whereas other metal ions, such as copper, cobalt, manganese, and zinc, did not affect perR transcription. Notably, a perR mutation substantially increased the level of perR transcription and in trans complementation restored the transcriptional changes, suggesting perR is transcriptionally autoregulated in C. jejuni. In the perR mutant, iron did not repress perR transcription, indicating the iron dependence of perR expression results from perR autoregulation. Electrophoretic mobility shift assays showed that PerR binds to the perR promoter, and DNase I footprinting assays identified a PerR binding site overlapping the ؊35 region of the two perR promoters, further supporting perR autoregulation at the transcriptional level. Alignment of the PerR binding sequence in the perR promoter with the regulatory region of other PerR regulon genes of C. jejuni revealed a 16-bp consensus PerR binding sequence, which shares high similarities to the Bacillus subtilis PerR box. The results of this study demonstrated that PerR directly interacts with the perR promoter and regulates perR transcription and that perR autoregulation is responsible for the repression of perR transcription by iron in C. jejuni.

ObjectiveFew studies have focused on the characteristic features of drug overdose in children and adolescents who have attempted suicide in Korea. The present study examined the characteristics of drug overdose in children and adolescents who visited the emergency room following drug ingestion for a suicide attempt.MethodsThe medical records of 28 patients who were treated in the emergency room following a drug overdose from January 2008 to March 2011 were analyzed. Demographic and clinical variables related to the suicide attempts were examined.ResultsThe mean age of the patients was 16.6±1.7 years (range 11-19 years), and 20 of the patients (71.4%) were female. Most of the patients (n=23, 82.1%) overdosed on a single drug; acetaminophen-containing analgesics were the most common (n=12, 42.9%). Depression was the most common psychiatric disorder (n=22, 78.6%), and interpersonal conflict was the most common precipitating factor of the suicide attempts (n=11, 39.3%). This was the first suicide attempt for approximately 80% of the patients. About one fourth of the patients (n=7, 25%) had follow-up visits at the psychiatric outpatient clinic.ConclusionEarly screening and psychiatric intervention for depression may be an important factor in preventing childhood and adolescent suicide attempts. Developing coping strategies to manage interpersonal conflicts may also be helpful. Moreover, policies restricting the amount and kind of drugs purchased by teenagers may be necessary to prevent drug overdose in this age group.