Giant nonlinear self-phase modulation of large-amplitude spin waves in microscopic YIG waveguides.

Nonlinear self-phase modulation is a universal phenomenon responsible, for example, for the formation of propagating dynamic solitons. It has been reported for waves of different physical nature. However its direct experimental observation for spin waves has been challenging. Here we show that exceptionally strong phase modulation can be achieved for spin waves in microscopic waveguides fabricated from nanometer-thick films of magnetic insulator, which support propagation of spin waves with large amplitudes corresponding to angles of magnetization precession exceeding 10°. At these amplitudes, the nonstationary nonlinear dynamic response of the spin system causes an extreme broadening of the spectrum of spin-wave pulses resulting in a strong spatial variation of the spin-wave wavelength and a temporal variation of the spin-wave phase across the pulse. Our findings demonstrate great complexity of nonlinear wave processes in microscopic magnetic structures and importance of their understanding for technical applications of spin waves in integrated devices.

The rise of intelligent matter.

Artificial intelligence (AI) is accelerating the development of unconventional computing paradigms inspired by the abilities and energy efficiency of the brain. The human brain excels especially in computationally intensive cognitive tasks, such as pattern recognition and classification. A long-term goal is de-centralized neuromorphic computing, relying on a network of distributed cores to mimic the massive parallelism of the brain, thus rigorously following a nature-inspired approach for information processing. Through the gradual transformation of interconnected computing blocks into continuous computing tissue, the development of advanced forms of matter exhibiting basic features of intelligence can be envisioned, able to learn and process information in a delocalized manner. Such intelligent matter would interact with the environment by receiving and responding to external stimuli, while internally adapting its structure to enable the distribution and storage (as memory) of information. We review progress towards implementations of intelligent matter using molecular systems, soft materials or solid-state materials, with respect to applications in soft robotics, the development of adaptive artificial skins and distributed neuromorphic computing.

Efficient Steady-State Solver for the Hierarchical Equations of Motion Approach: Formulation and Application to Charge Transport through Nanosystems.

An iterative approach is introduced, which allows the efficient solution of the hierarchical equations of motion (HEOM) for the steady-state of open quantum systems. The approach combines the method of matrix equations with an efficient preconditioning technique to reduce the numerical effort of solving the HEOM. Illustrative applications to simulate nonequilibrium charge transport in single-molecule junctions demonstrate the performance of the method.

Transrectal Ultrasound Guided Hydrodistension - A New Surgical Way in Transgender Surgery.

BACKGROUND: Creating the neovaginal canal in transwomen is one of the most delicate steps of Genital Gender Affirming Surgery (GGAS). Injury to the rectum is a rare but serious complication that can lead to further surgery and even creation of a colostomy. AIM: Implementation of a novel hydrospacing technique (HST) based on transrectal ultrasound (TRUS)-guided hydrodistension. METHODS: Between June 2018 and June 2020 54 transwomen received GGAS with HST. Immediately before GGAS transperineal hydrodistension was performed using a TSK-Supra-Needle (20 Gauge, 120 mm length), that was placed under direct TRUS-guided visual control between Denonvilliers' fascia and the anterior rectal wall. 40 - 60 ml normal saline were administered perineally to separate Denonvilliers' fascia from the anterior rectal wall to create a dissection of at least 20 mm. For better intraoperative visualization the hydrodissected space was also dyed using 2ml of methylenblue while retracting the needle. A retrospectively analysed, clinically and demographically comparable series of 84 transwomen who underwent GGAS between June 2016 and June 2018 served as control group. All 138 surgeries were performed by the same experienced surgeon. OUTCOMES: The effect of the novel hydrospacing technique on neovaginal dimensions and operating time. RESULTS: Patients in both groups did not differ in baseline patient characteristics such as age and body mass index (HST 35 vs 38 years in control group, P = .44 and body mass index 26 vs 25 kg/m2, P = .73). Vaginal depth and width were significantly larger in the HST subgroup as compared to controls (14.4 cm vs 13.5 cm, P = .01 and 4.2 cm vs 3.8 cm, P < .001). No statistically significant difference occurred in intraoperative rectal injury (n = 0 in HST group, n = 2 in control group, P = .26). Median total OR-time was comparable for GGAS including HST before vaginoplasty to standard technique (211 minutes for HST vs 218 minutes; P = 0.19). CLINICAL IMPLICATIONS: The proposed additional surgical step during GGAS is minimally invasive and safe, simplifies GGAS and potentially helps to avoid complications such as rectal injury. STRENGTH & LIMITATIONS: Single-surgeon series, limited follow-up time and no prospective randomization. CONCLUSION: HST is a safe and feasible procedure, which facilitates a safe preparation of the neovaginal canal during male to female GGAS. Panic A, Rahmani N, Kaspar C, et al. Transrectal Ultrasound Guided Hydrodistension - A New Surgical Way in Transgender Surgery. J Sex Med 2021;18:1135-1141.

[Penile prosthesis]. / Schwellkörperimplantate.

The insertion of a penile prosthesis (PP) is a definitive treatment option for erectile dysfunction (ED), induratio penis plastica, after phalloplasty or priapism. The aim is a "normal" erection with the possibility of a satisfactory sexual life. The costs of the operation are covered by the health insurance. In addition, manual dexterity, concomitant diseases and possible contraindications should be considered preoperatively. While semirigid PPs are simply aligned in the desired position when used, inflatable PPs must be activated and deactivated via a pump. In addition to injury to local structures and postoperative infections, long-term complications such as mechanical implant failure or an undesirable cosmetic result may also occur. Careful patient selection and a detailed counselling and information session are therefore of decisive importance. Implantation is performed in the supine or lithotomy position via an infrapubic or penoscrotal approach. PPs should not be implanted if cutaneous, systemic or urinary tract infections are present. Inflatable PPs are preferred by most patients as they come closest to a "natural" erection. A PP offers one of the highest satisfaction rates among treatment options, regardless of indication, and is highly rated by patients and their partners across models due to product reliability. Differences between the models of the various manufacturers could not be demonstrated. The choice of prosthesis should therefore be adapted to the patient's individual requirements and health conditions.

[Unemployment and Addiction: The SUNRISE Project]. / Arbeitslosigkeit und Sucht ­ Das SUNRISE-Projekt.

OBJECTIVES: In the SUNRISE-project, the unemployment benefit office refers long-term unemployed clients (25-49 years old) to medical and psychological specialists of an addiction clinic, if substance-related problems are suspected as an obstacle for job placement. The present study aims at characterizing these clients with respect to educational qualifications, vocational training, diagnosed addictive disorders, and other mental disorders. Of special interest is the temporal sequence of unemployment and addictive disorders. METHOD: Officials referred clients to medical examination if substance abuse was suspected. The examination was based on Europ-ASI, diagnosis of mental disorders based on SCID-I and SCID-II. RESULTS: In 87 out of the first 100 examined persons, an addictive disorder was diagnosed, most frequently alcohol-related disorders, and often multiple addictive disorders. These 87 clients were on average 40 years old (SD 8.5), and mostly male (73 out of 87 clients). About one-third had very low school qualification, and 55.2% had not completed vocational training. An additional psychiatric diagnosis was made in 51.7%. Addictive disorders had commenced during adolescence or early adulthood in most cases. The longest duration of continuous employment was 3 years (median). In only a few cases (7.4%), the current period of unemployment had started before regular substance use. CONCLUSION: Many long-term unemployed clients examined here showed deficits in schooling and vocational training, early onset of regular substance use, and additional mental disorders. In most cases, the addictive disorder did not emerge as a consequence of unemployment, but had existed before. Programs combining the efforts of unemployment benefit offices and the healthcare system are needed for these clients to help them gain access to the regular job market.

The antenatal urinary tract dilation classification system accurately predicts severity of kidney and urinary tract abnormalities.

BACKGROUND: Urinary tract dilation (UTD) is a commonly diagnosed prenatal condition; however, it is currently unknown which features lead to benign and resolving or pathologic abnormalities. A consensus UTD classification system (antenatal UTD classification, UTD-A) was created by Nguyen et al. in 2014 [1], but has not yet been validated. OBJECTIVE: To evaluate the ability of the UTD-A system to identify kidney and urinary tract (KUT) abnormalities, assess whether UTD-A can predict severity of KUT conditions, and perform a cost analysis of screening ultrasound (US). METHODS: A retrospective single-center study was conducted at an academic medical center. Inclusion criteria were: neonates in the well or sick nursery who had a complete abdominal or limited renal US performed in the first 30 days of life between January 01, 2011 and December 31, 2013. Data were collected on prenatal US characteristics from which UTD-A classification was retrospectively applied, and postnatal data were collected up to 2 years following birth. RESULTS: A total of 203 patients were identified. Of the 36 abnormal postnatal KUT diagnoses, 90% were identified prenatally as UTD A1 or UTD A2-3. The remaining 10% developed postnatal KUT abnormalities due to myelomeningocele, such as VUR or UTD, which were not evident prenatally. Overall sensitivity and specificity of the UTD-A system was 0.767 (95% CI 0.577, 0.901) and 0.836 (95% CI 0.758, 0.897), respectively, when resolved UTD was counted as a normal diagnosis. Postnatal diagnoses differed by UTD-A classification as shown in the Summary fig. Of all the obstructive uropathies, 90.9% occurred in the UTD A2-3 class and none occurred in UTD-A Normal. Rate of postnatally resolved UTD was significantly higher in the UTD A1 group (78%) compared with UTD A2-3 (31%) or UTD-A Normal (12%, all P < 0.001). There was a notable trend towards more UT surgeries, UTI, and positive VUR among UTD A2-3 patients, but statistical significance was limited by a small number of patients. CONCLUSIONS: This study found that the UTD-A classification system revealed important differences in the severity of UTD abnormalities. With repeated validation in larger cohorts, the UTD-A classification may be used to offer a prognosis for parents regarding prenatally diagnosed KUT conditions. Larger prospective studies should be designed to validate whether the UTD-A system can predict postnatal events related to UTD morbidity such as need for UT-related surgery or UTI.

A Review of Pediatric Chronic Kidney Disease.

Chronic kidney disease is complex in both adults and children, but the disease is far from the same between these populations. Here we review the marked differences in etiology, comorbidities, impact of disease on growth and quality of life, issues unique to adolescents and transitions to adult care, and special considerations of congenital kidney and urinary tract anomalies for transplantation.

Relative frequency of norovirus infection in children with acute gastroenteritis.

AIM: The aim of this study was to determine the prevalence of norovirus among children with acute gastroenteritis in 2009 and 2010. We also aimed that, to detecting the possible clinical and laboratory differences among cases in 2009 and 2010. METHODS: Fecal samples were collected from children under 16 years of age who were admitted for acute gastroenteritis. Norovirus was detected using immunochromatography. For the comparison of seasonal distribution, clinical manifestations, and laboratory results between cases, we divided subjects into two groups by year. RESULTS: Norovirus infection was detected in 112 of the 1027 collected samples (10.9%). In three cases with norovirus, other enteric viruses like rotavirus and adenovirus are detected concurrently, and these were excluded. After the exclusion of three cases with co-infections, statistical analysis was made in 109 cases. Most of the positive cases were between 1-24 months of age (N.=75, 67%). The rate of norovirus infection peaked in winter in 2010 (P<0.05). However, the rates were not significantly different between seasons in 2009 (P>0.05). We did not detect any positive cases in late summer and autumn in 2010. Diarrhea (97.2%), vomiting (95.4%), and abdominal pain (65.1%) were most frequently encountered symptoms of patients with norovirus. Leukocytosis and neutrophilia were significantly higher in 2010 than 2009 (P<0.05). CONCLUSION: The prevalence and clinical characteristics of norovirus in our study group is similar but seasonal distribution is different between two years. Most of the cases were <24 months of age. Like rotavirus, norovirus vaccine can be developed to prevent infection.

Transmission of Escherichia coli O157:H7 in cattle is influenced by the level of environmental contamination.

A pen infection-transmission experiment was conducted to elucidate the role of pathogen strain and environmental contamination in transmission of Escherichia coli O157:H7 (ECO157) in cattle. Five steers were inoculated with a three-strain mixture of ECO157 and joined with five susceptible steers in each of two experimental replicates. Faecal and environmental samples were monitored for ECO157 presence over 30 days. One ECO157 strain did not spread. Transmission rates for the other two strains were estimated using a generalized linear model developed based on a modified 'Susceptible-Infectious-Susceptible' mathematical model. Transmission rates estimated for the two strains (0·11 and 0·14) were similar. However, the rates significantly (P = 0·0006) increased 1·5 times for every 1-unit increase in the level of environmental contamination measured as log10 c.f.u. Depending on the level of environmental contamination, the estimated basic reproduction numbers varied from <1 to 8. The findings indicate the importance of on-farm measures to reduce environmental contamination for ECO157 control in cattle that should be validated under field conditions.

Growth and survival parameter estimates and relation to RpoS levels in serotype O157:H7 and non-O157 Shiga toxin-producing Escherichia coli.

AIMS: This study analysed the growth and survival of 18 strains of the six serotypes of non-O157 Shiga toxin-producing Escherichia coli (STEC) (O26, O45, O103, O111, O121 and O145) most frequently implicated in human illness and compared them with Escherichia coli O157:H7 strain ATCC43895. METHODS AND RESULTS: The data from growth in Luria-Bertani broth (LB)-HCl (pH 4.0, 4.5, 4.8), LB-lactate (pH 4.5 and 4.8) and LB-NaCl (5%, 7%) were fitted to modified Gompertz equations to enable quantitative comparisons across strains and media conditions. Serogroup O45 strains had growth rates that were equal to or significantly greater than the O157:H7 control strain in all growth conditions tested. The growth rate was independent from the maximum growth achieved, but three strains (103A, 121A and 45B) had significantly faster growth and greater maximum cell densities in LB-NaCl 5% (strain 103A), LB-HCl pH 4·0 (strain 121A) and LB-NaCl 7% (strain 45B). Survival in LB-HCl pH 3.0 of four strains (103C, 111B, 26B and 26C) was significantly greater and five strains (26A, 45A, 111A, 121A and 145A) were significantly reduced in comparison with the O157:H7 control strain. None of the STEC strains had greater survival in LB-NaCl 12% than the O157:H7 control strain. A significant association was found between the exponential phase, but not stationary phase, RpoS level and survival of STEC. CONCLUSIONS: Some STEC strains had growth or survival properties that exceeded those of the O157:H7 control strain, but none of the non-O157 STEC had both significantly greater growth and survival properties. STEC survival was associated with the exponential-phase RpoS level. SIGNIFICANCE AND IMPACT OF THE STUDY: Results from this study define the variability in growth and survival of STEC strains that will be useful defining food product formulations and process interventions to control STEC. The presence of exponential phase σ(s) expands the significance of this alternative sigma factor.

Effects of ACE polymorphisms and other risk factors on the severity of coronary artery disease.

Coronary artery disease (CAD) is a multifactorial disease influenced by genetic and environmental factors. Major risk factors of CAD are hypertension, hyperlipidemia, smoking, family history and obesity. Also polymorphisms in the angiotensin-I converting enzyme (ACE) gene can associate with CAD. The relationship between ACE polymorphisms and other risk factors is not well understood in CAD, likely due to the complex interrelation of genetic and environmental risk factors. The aim of this study was to investigate the associations of CAD risk factors and ACE polymorphisms in patients with CAD. We enrolled 203 consecutive patients and 140 healthy subjects in the study. The severity of CAD was evaluated according to the number of vessels with significant stenosis. ACE insertion (I)/deletion (D) genotype was determined by PCR. The frequency of the DD genotype was significantly higher in patients. D allele frequency was higher among CAD subjects when compared to the control group. The number of stenotic vessels were found to be statistically associated with a high frequency of DD polymorphism and D allele and a low frequency of I allele in patients, especially in male patients. The control group displayed II and ID genotypes more frequently than did the patients. The ACE I/D genotype was associated with hyperlipidemia and smoking history. We consider that the DD polymorphism and D allele may affect the severity of CAD, while I allele may have a protective effect. In conclusion, the ACE I/D genotype may interact with conventional risk criteria in determining the risk of CAD.

The strain-specific dynamics of Escherichia coli O157:H7 faecal shedding in cattle post inoculation.

This study reports analysis of faecal shedding dynamics in cattle for three Escherichia coli O157:H7 (ECO157) strains (S1, S2 and S3) of different genotype and ecological history, using experimental inoculation data. The three strains were compared for their shedding frequency and level of ECO157 in faeces. A multistate Markov chain model was used to compare shedding patterns of S1 and S2. Strains S1 and S2 were detected seven to eight times more often and at 10(4) larger levels than strain S3. Strains S1 and S2 had similar frequencies and levels of shedding. However, the total time spent in the shedding state during colonization was on average four times longer for S1 (15 days) compared to S2 (4 days). These results indicate that an ECO157 strain effect on the frequency, level, pattern and the duration of faecal shedding may need to be considered in control of ECO157 in the cattle reservoir.

Effectiveness of environmental decontamination as an infection control measure.

The effectiveness of environmental decontamination (ED) as a measure in the control of infectious diseases is controversial. This work quantifies the effectiveness of ED by analysing the transmission of pathogens from the environment to susceptible hosts in a Susceptible-Infected-Susceptible model. Analysis of the model shows that ED can render a population disease-free only when the duration of infection (D) is within a certain range. As host-to-host transmission rate is increased, D falls outside this range and the higher levels of ED have a diminishing return in reducing the number of infected hosts at endemic equilibrium. To avoid this, ED can be combined with other control measures, such as treating infected individuals to push the duration of infection into the specified range. We propose decision criteria and minimum ED efforts required for control policies to be effective.

Isolation of Escherichia coli O157:H7 from the gall bladder of inoculated and naturally-infected cattle.

To determine if Escherichia coli O157:H7 is capable of residing in the gall bladder of cattle, inoculation studies were conducted with O157:H7 strain 86-24 in weaned Holstein calves. Strain 86-24 was isolated from the gall bladders of five calves 36 days after inoculation. Two other calves contained the inoculation strain in the distal colon but the organism was absent in their gall bladders. A second trial in which the calves were euthanized 15 days after inoculation found strain 86-24 in six of seven inoculated calves but only in colon and/or rumen samples. In a third trial that inoculated eight calves with a four-strain cocktail of O157:H7 strains, the gall bladders from all eight animals were positive 9 days after inoculation. The colon and rumen samples from these calves were also positive. E. coli O157:H7 isolates recovered from bile samples and subtyped by pulsed field gel electrophoresis found that three of the four inoculation strains were present in one or more of the calves. Thus, residence in the gall bladder is not restricted to a single strain. Additional evidence of the ability to localize in the gall bladder of cattle was provided by testing the bile from 150 gall bladders (five collection dates, 30 samples each) obtained at an abbatoir and the isolation of E. coli O157:H7 from four samples (2.7%). This study establishes that E. coli O157:H7 can reside transiently or permanently at a low level in the gall bladder of cattle.

Characterization of Escherichia coli O157:H7 from downer and healthy dairy cattle in the upper Midwest region of the United States.

While cattle in general have been identified as a reservoir of Escherichia coli O157:H7, there are limited data regarding the prevalence and clonality of this pathogen in downer dairy cattle and the potential impact to human health that may occur following consumption of meat derived from downer dairy cattle. In the present study, conducted at two slaughter facilities in Wisconsin between May and October of 2001, we established a higher prevalence of E. coli O157:H7 in fecal and/or tissue samples obtained aseptically from intact colons of downer dairy cattle (10 of 203, 4.9%) than in those from healthy dairy cattle (3 of 201, 1.5%). Analyses of 57 isolates, representing these 13 positive samples (one to five isolates per sample), by pulsed-field gel electrophoresis, revealed 13 distinct XbaI restriction endonuclease digestion profiles (REDP). Typically, isolates from different animals displayed distinct REDP and isolates from the same fecal or colon sample displayed indistinguishable REDP. However, in one sample, two different, but highly related, REDP were displayed by the isolates recovered. Antimicrobial susceptibility testing indicated that 10 of the 57 isolates, recovered from 2 (1 downer and 1 healthy animal) of the 13 positive samples, were resistant to at least 1 of 18 antimicrobials tested. However, there was no appreciable difference in the frequency of resistance of isolates recovered from downer and healthy dairy cattle, and not all isolates with the same REDP displayed the same antimicrobial susceptibility profile. Lastly, it was not possible to distinguish between isolates recovered from downer and healthy cattle based on their XbaI REDP or antimicrobial susceptibility. These results indicate that downer cattle had a 3.3-fold-higher prevalence of E. coli O157:H7 than healthy cattle within the time frame and geographic scope of this study.

Shedding of Escherichia coli O157:H7 in dairy cattle housed in a confined environment following waterborne inoculation.

A study of Escherichia coli O157:H7 transmission and shedding was conducted with bull calves housed in individual pens within a confined environment. For comparative purposes, the numbers and duration of E. coli O157:H7 shedding in naturally infected calves were monitored after a single purchased calf (calf 156) tested positive prior to inoculation. During the next 8 days, the calves in adjacent pens and a pen directly across a walkway from calf 156 began to shed this serotype O157:H7 strain. Five of the eight calves in this room shed this O157:H7 strain at some time during the following 8 weeks. The numbers of E. coli O157:H7 isolates shed in these calves varied from 60 to 10(5) CFU/g of feces, and the duration of shedding ranged from 17 to >31 days. The genomic DNAs from isolates recovered from these calves were indistinguishable when compared by using XbaI digestion and pulsed-field gel electrophoresis. Inoculation of calves with 1 liter of water containing ca. 10(3) to 10(4) CFU of E. coli O157:H7/ml resulted in shedding in 10 of 12 calves (trial 1, 4 of 4 calves; trial 2, 6 of 8 calves). The inoculated calves shed the inoculation strain (FRIK 1275) as early as 24 h after administration. The duration of shedding varied from 18 to >43 days at levels from 10(2) to 10(6) CFU/g of feces. The numbers of doses necessary to initiate shedding varied among calves, and two calves in trial 2 never shed FRIK 1275 after four doses (ca. 10(6) CFU per dose). Results from this study confirm previous reports of animal-to-animal and waterborne dissemination of E. coli O157:H7 and highlight the need for an effective water treatment to reduce the spread of this pathogen in cattle.

Poor prognosis acute myelogenous leukemia: 3--biological and molecular biological changes during remission induction therapy.

This is the third paper in a series which describes a new remission induction regimen for patients with 'poor prognosis' acute myelogenous leukemia (AML). Twenty-four patients were treated with two one day pulses of chemotherapy separated by 96 h. Each pulse consisted of two doses of cytarabine and a single dose of mitoxantrone. Amifostine was administered three times a week after the second pulse of chemotherapy until treatment outcome became known. The first paper described the outcome of treatment while the second described the relationship of treatment outcome to the pretherapy characteristics of the leukemia. This paper describes the changes in the leukemia cells which occur during remission induction therapy. While only a limited number of specimens were available for each post treatment study, the studies demonstrated a profound fall in blood counts, BM cellularity, and telomerase activity in leukemia cells after pulse #1 of treatment. This fall was usually accompanied by a coordinate rise in IL6, TNFalpha, and IL1beta transcripts within the AML cells which survived chemotherapy. High levels of telomerase activity in the day 5 marrow was correlated with high levels of IL1beta transcripts which in turn were associated with treatment failure ascribable to resistant disease.

Thalidomide produces transfusion independence in long-standing refractory anemias of patients with myelodysplastic syndromes.

Thalidomide was administered to 83 patients with myelodysplastic syndrome (MDS), starting at 100 mg by mouth daily and increasing to 400 mg as tolerated. Thirty-two patients stopped therapy before 12 weeks (minimum period for response evaluation), and 51 completed 12 weeks of therapy. International Working Group response criteria for MDS were used to evaluate responses. Intent-to-treat (ITT) analysis classified all off-study patients as nonresponders. Off-study patients belonged to a higher risk category (P =.002) and had a higher percentage of blasts in their pretherapy bone marrow than patients who completed 12 weeks of therapy (P =.003). No cytogenetic or complete responses were seen, but 16 patients showed hematologic improvement, with 10 previously transfusion-dependent patients becoming transfusion independent. Responders had lower pretherapy blasts (P =.016), a lower duration of pretherapy platelet transfusions (P =.013), and higher pretherapy platelets (P =.003). Among responders, 9 had refractory anemia (RA); 5 had RA with ringed sideroblasts; and 2 had RA with excess blasts. By ITT analysis, 19% of patients (16 of 83) responded, and when only evaluable patients were analyzed, 31% (16 of 51) responded. It was concluded that thalidomide, as a single agent, is effective in improving cytopenias of some MDS patients, especially those who present without excess blasts. (Blood. 2001;98:958-965)

Contribution of dps to acid stress tolerance and oxidative stress tolerance in Escherichia coli O157:H7.

An Escherichia coli O157:H7 dps::nptI mutant (FRIK 47991) was generated, and its survival was compared to that of the parent in HCl (synthetic gastric fluid, pH 1.8) and hydrogen peroxide (15 mM) challenges. The survival of the mutant in log phase (5-h culture) was significantly impaired (4-log(10)-CFU/ml reduction) compared to that of the parent strain (ca. 1.0-log(10)-CFU/ml reduction) after a standard 3-h acid challenge. Early-stationary-phase cells (12-h culture) of the mutant decreased by ca. 4 log(10) CFU/ml while the parent strain decreased by approximately 2 log(10) CFU/ml. No significant differences in the survival of late-stationary-phase cells (24-h culture) between the parent strain and the mutant were observed, although numbers of the parent strain declined less in the initial 1 h of acid challenge. FRIK 47991 was more sensitive to hydrogen peroxide challenge than was the parent strain, although survival improved in stationary phase. Complementation of the mutant with a functional dps gene restored acid and hydrogen peroxide tolerance to levels equal to or greater than those exhibited by the parent strain. These results demonstrate that decreases in survival were from the absence of Dps or a protein regulated by Dps. The results from this study establish that Dps contributes to acid tolerance in E. coli O157:H7 and confirm the importance of Dps in oxidative stress protection.