Effect of potassium lactate and a potassium lactate-sodium diacetate blend on Listeria monocytogenes growth in modified atmosphere packaged sliced ham

Two commercially available organic acid salts, potassium lactate (PURASAL HiPure P) and a potassium lactate-sodium diacetate blend (PURASAL Opti. Form PD 4), were assessed as potential inhibitors of Listeria monocytogenes growth in modified atmosphere packaged (MAP) sliced ham in challenge studies. The influence of the initial inoculation level of L. monocytogenes (10(1) or 10(3) CFU g(-1)) and storage temperature (4 or 8 degrees C) was also examined. The addition of either organic acid salt to MAP sliced ham strongly inhibited the growth of L. monocytogenes during the normal shelf life of the product under ideal refrigeration conditions (4 degrees C) and even under abusive temperature conditions (i.e., 8 degrees C). During the challenge studies and in the absence of either organic acid salt, L. monocytogenes numbers increased by 1000-fold after 20 days at 8 degrees C and 10-fold after 42 days at 4 degrees C. Both organic acid salt treatments were found to be listeriostatic rather than listericidal. The addition of either organic acid salt to the MAP ham also reduced the growth of indigenous microflora, i.e., aerobic microflora and lactic acid bacteria. The influence of these compounds on the risk of listeriosis in relation to product shelf life is discussed.

Population-based laboratory surveillance for tribe Proteeae isolates in a large Canadian health region

The tribe Proteeae comprises the genera Proteus, Morganella and Providencia. Few studies have specifically investigated the epidemiology of infections caused by the Proteeae, and none has been conducted in a large non-selected population. The present study was a population-based laboratory surveillance in the Calgary Health Region (population 1.2 million), Canada during 2000-2005 that aimed to define the incidence, demographical risk-factors for acquisition and antimicrobial susceptibilities of Proteeae isolates. In total, 5047 patients were identified from whom Proteeae isolates were obtained (an annual incidence of 75.9/100 000), with females and the elderly being at highest risk. Incidence rates were 64.8, 7.7 and 3.4/100,000/year for the genera Proteus, Morganella and Providencia, respectively. Overall, 85% of infections were community-onset, and the overall rate of bacteraemic disease was 2.0/100,000. Compared with other species, Proteus mirabilis occurred at a much higher frequency, especially among females, and was less likely to be isolated from hospital-onset infections or to be part of a polymicrobial infection. Among isolates from community-onset infections, Providencia spp. were less likely to be from outpatients and more likely to be from nursing home residents. There were low overall rates of resistance to ciprofloxacin (4%) and gentamicin (5%), with Prot. mirabilis generally being the most susceptible. Members of the Proteeae were isolated frequently in both the community and hospital settings, but were infrequent causes of invasive disease. The occurrence, demographical risk-factors and microbiology of Proteeae isolates varied according to the individual species.

Cholera-like diarrhea and shock associated with community-acquired methicillin-resistant Staphylococcus aureus (USA400 clone) pneumonia

A 14-year-old girl presented with florid watery diarrhea, vomiting and hypotension without respiratory prodrome. Shock, multiorgan system failure and death rapidly ensued. Influenza A was detected from her nasopharynx and CA-MRSA (USA400), positive for pvl, mecA, sea, sec and seh genes was cultured from a deep tracheal aspirate.

Interactions between metabolic status, pre-breeding protein supplementation, uterine pH, and embrionic mortality in ewes: preliminary observations

The effect of prebreeding short-term protein supplementation level (PL) and body condition (BC) on fertility rate (FERT,%), uterine pH and embryonic mortality (EMORT,%) in sheep, was evaluated. Multiparous Rambouillet ewes at low BC (LC; n = 6, 62.7+/-1.7 kg) or high BC (HC; n = 6, 71.9 +/-1.7 kg), received, within BC, one of two levels of ruminally undegradable protein: low (LP, 14 g/ewe per day) and high (HP, 30 g/ewe per day). Once the animals were euthanized, corpus luteum number (CLN), as an indicator of ovulation rate, was registered and uterine horns were irrigated to recover embryonic tissue plus associated membranes as well as to measure uterine pH (UpH). While EMORT- 1 considered a nonadjusted relationship between the number of embryos and CLN, EMORT-2 considered an analysis of covariance using CLN as the covariate. The HP-supplemented ewes had the lowest FERT (p = 0.06; 100% vs 50%) and the highest EMORT (EMORT-1, 16.6% vs 53.8%, p = 0.08; EMORT-2, 52.0% vs 14.5%, p = 0.07) when compared to the LP-supplemented ewes. Neither BC nor PL affected CLN, CL weight or P4 release (p > 0.10). While the lowest UpH (p = 0.04) was observed in the HP-supplemented ewes, this group also showed the lowest fertility and the highest embryonic mortality.

Begutachtung und Behandlung von Sexualstraftätern

Sexual offences are a heterogeneous group of offences that entail very different diagnostic categories relevant for key issues of expert assessment. Sexual offender trials usually deal with issues related to (diminished) responsibility and the necessity of a referral to a forensic psychiatric hospital ( section sign 63 StGB, German penal code). Furthermore, risk assessment is seen as a necessary precondition for relapse prevention and consequently, it forms part of any expert assessment in sex offender trials. In terms of treatment, manualized treatment programs prevail. Usually they lend themselves to psycho-educative, cognitive-behavioral and psychodynamic concepts. Notwithstanding the focus of any individual program, core elements of all programs pertain to offence related (e.g., victim empathy, attitudes and individual values, minimizations, etc.) and more general psychotherapy modules (anger management, substance abuse, social skills training, etc.). Advantages and disadvantages of these programs are named and discussed.

Burden of community-onset bloodstream infection: a population-based assessment

Although community-onset bloodstream infection (BSI) is recognized to be a major cause of morbidity and mortality, there is a paucity of population-based studies defining its overall burden. We conducted population-based laboratory surveillance for all community-onset BSI in the Calgary Health Region during 2000-2004. A total of 4467 episodes of community-onset BSI were identified for an overall annual incidence of 81.6/100,000. The three species, Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae were responsible for the majority of community-onset BSI; they occurred at annual rates of 25.8, 13.5, and 10.1/100,000, respectively. Overall 3445/4467 (77%) episodes resulted in hospital admission representing 0.7% of all admissions to major acute care hospitals. The subsequent hospital length of stay was a median of 9 (interquartile range, 5-15) days; the total days of acute hospitalization attributable to community-onset BSI was 51,146 days or 934 days/100,000 annually. Four hundred and sixty patients died in hospital for a case-fatality rate of 13%. Community-onset BSI is common and has a major patient and societal impact. These data support further efforts to reduce the burden of community-onset BSI.

Effect of suspension media on nonthermal inactivation ofEscherichia coli

AIMS

To investigate the influence of suspension media on the survival of Escherichia coli M23 exposed to nonthermal, lethal stresses.

METHODS AND RESULTS

Populations of E. coli M23 suspended in minimal medium (MM) or in different nutrient-rich broths were exposed to water activity 0.90 and/or pH 3.5 and inactivation was determined by culture-based enumeration. In response to the osmotic or acid challenges, E. coli M23 displayed enhanced survival in MM rather than in complex broth. That trend was reversed when populations were exposed to low water activity in combination with low pH. Comparison of microbial survival in three complex media indicated that even relatively small differences in composition influenced inactivation. In most media the combination of lethal stresses resulted in a synergism, which enhanced bacterial inactivation; however, an exception (tryptone soya broth) was observed.

CONCLUSIONS

The suspension medium strongly influences the inactivation of E. coli M23 by osmotic and/or acid stresses. This should be considered when comparing studies of microbial survival that use different media and when broth-derived data are intended to represent specific environments (e.g. food matrices).

SIGNIFICANCE AND IMPACT OF THE STUDY

The specific effects of synthetic media need to be appreciated when studying bacterial inactivation in conditions relevant to food-manufacturing regimes.

Effects of the CB1R agonist WIN-55,212-2 and the CB1R antagonists SR-141716 and AM-1387: Open-field examination in rats

This study examined the open-field (O-F) effects in rats of the cannabinoid 1 receptor (CB1R) agonist WIN-55,212-2 (WIN; 1 to 5.6 mg/kg) and its interaction with the CB1R antagonist/inverse agonist SR-141716 (1 to 5.6 mg/kg). Additionally, separate studies examined the O-F effects of SR-141716 (1 to 10 mg/kg) and a newly synthesized CB1R selective antagonist/inverse agonist AM-1387 (3 and 10 mg/kg) when these ligands were administered alone. Both antagonists are characterized in vitro by decreased of GTPgammaS binding and increased cAMP accumulation (inverse agonism). WIN dose dependently reduced ambulation (horizontal activity) and rearing (vertical activity); SR-141716 completely (WIN 3 mg/kg) or partially (WIN 5.6 mg/kg) normalized these behaviors. WIN alone resulted in circling and in an increased latency to leave the start area of the O-F, effects blocked by all doses of SR-141716. Both the increased scratching and grooming, associated with SR-141716 administration, were attenuated but not abolished by WIN. SR-141716 alone tended to reduce ambulation (significant at 10 mg/kg) and rearing (non-significant), had no effect on latency, and increased scratching and grooming (both frequency and duration), at doses of 3 mg/kg and up. At the doses examined, AM-1387 had no effect on ambulation, rearing, latency but significantly increased scratching (10 mg/kg); there was also a trend for increased grooming (both frequency and duration). The O-F profile of WIN suggests more similarity with the effects of THC rather than methanandamide (and presumably also anandamide). Intrinsic activity (scratching and grooming) by SR-141716 was re-affirmed and seemed to be associated with administration of AM-1387 as well. AM-1387 was less potent than SR-141716.

Information systems in food safety management

Information systems are concerned with data capture, storage, analysis and retrieval. In the context of food safety management they are vital to assist decision making in a short time frame, potentially allowing decisions to be made and practices to be actioned in real time. Databases with information on microorganisms pertinent to the identification of foodborne pathogens, response of microbial populations to the environment and characteristics of foods and processing conditions are the cornerstone of food safety management systems. Such databases find application in: Identifying pathogens in food at the genus or species level using applied systematics in automated ways. Identifying pathogens below the species level by molecular subtyping, an approach successfully applied in epidemiological investigations of foodborne disease and the basis for national surveillance programs. Predictive modelling software, such as the Pathogen Modeling Program and Growth Predictor (that took over the main functions of Food Micromodel) the raw data of which were combined as the genesis of an international web based searchable database (ComBase). Expert systems combining databases on microbial characteristics, food composition and processing information with the resulting "pattern match" indicating problems that may arise from changes in product formulation or processing conditions. Computer software packages to aid the practical application of HACCP and risk assessment and decision trees to bring logical sequences to establishing and modifying food safety management practices. In addition there are many other uses of information systems that benefit food safety more globally, including: Rapid dissemination of information on foodborne disease outbreaks via websites or list servers carrying commentary from many sources, including the press and interest groups, on the reasons for and consequences of foodborne disease incidents. Active surveillance networks allowing rapid dissemination of molecular subtyping information between public health agencies to detect foodborne outbreaks and limit the spread of human disease. Traceability of individual animals or crops from (or before) conception or germination to the consumer as an integral part of food supply chain management. Provision of high quality, online educational packages to food industry personnel otherwise precluded from access to such courses.

Salt, alone or in combination with sucrose, can improve the survival of Escherichia coli O157 (SERL 2) in model acidic sauces

The commercial production of microbiologically safe and stable sauces containing acetic acid is guided by the Comité des Industries des Mayonnaises et Sauces Condimentaires de la Communauté Economique Européenne's (CIMSCEE) code. The CIMSCEE safety value is calculated using a linear regression equation combining weighted contributions of pH and aqueous-phase concentrations of undissociated acetic acid, NaCl, and sugars. By implication, the CIMSCEE safety equation predicts that increasing concentrations of hurdles will always increase inactivation of the target pathogen. In this study, the time to achieve a 3-log10 reduction of an acid-resistant, acid-adapted, Shiga toxin-producing Escherichia coli (STEC) O157 isolate was determined experimentally for 81 formulations at various pHs and acetic acid, NaCl, and sucrose concentrations in a broth model. The combinations were intended to simulate the aqueous phase of acidic sauces and dressings. Experimental data were fitted to the log logistic model to estimate the time to 3-log10 reduction (t3D). Comparison of fitted t3D estimates with CIMSCEE values showed agreement in predicting safety (as defined by CIMSCEE) for the majority of formulations. However, CIMSCEE safety predictions were "fail dangerous" for 13 of 81 formulations. Among these formulations and others, the observed E. coli t3D initially increased and then decreased with increasing osmolalities (NaCl and sucrose). Relative protection increased with exposure time where the protective effect of NaCl predominated. While commercial acidic sauces are not considered high-risk vehicles for STEC, interactions among hurdles that decrease their combined effectiveness are deserving of further investigation because they may reveal mechanisms of broader relevance in the inactivation of pathogens in foods.

Forensische Psychotherapieforschung - Status Quo, Aufgaben und Perspektiven

In the last two decades, forensic psychotherapy has become a specialised area of scholarship, predominantly in the UK and Germany. However, scientific research with respect to set goals, methods and the application of treatments has been heterogeneous and not very extensive. Focussing on offender treatment, the status quo of research schemes based on clinical experience is discussed, and a strategy is suggested as how to develop a research framework for forensic psychotherapy which makes use of the specific methods and treatment interventions applied in this field. It is concluded that forensic psychotherapy research will greatly benefit from the methodological framework of general psychotherapy research, especially when competing for scarce financial resources.

Population-based surveillance of invasive pyogenic streptococcal infection in a large Canadian region

Pyogenic streptococci are a major cause of invasive infection. This study presents the results of a population-based laboratory surveillance for invasive pyogenic streptococcal infections among residents of the Calgary Health Region (population 1 million) between 1 July 1999 and 30 June 2004. The overall annual incidence rate was 18.65/100,000 population, with isolates belonging to the Streptococcus milleri group forming the most important aetiology (incidence of 8.65/100,000 population). Invasive infection with groups A, B, G and C streptococci occurred at annual rates of 4.27, 3.13, 1.83 and 0.41/100,000 population, respectively. There was a close relationship between increasing age and development of an invasive pyogenic streptococcal infection, and the incidence of infection was higher among males than among females. Differences in the seasonal occurrence and focus of infection occurred between the different groups.

Presence and quality of navigational landmarks: effect on driver performance and implications for design

OBJECTIVE

The objective of this study was to investigate the impact of landmark information of varying quality within drivers' navigation instructions on driving and navigation performance when navigating an unfamiliar route.

BACKGROUND

Current vehicle navigation systems predominantly use distance-to-turn information to enable a driver to locate a forthcoming maneuver. Although it has been proposed that the design of driver navigation aids can be improved through the incorporation of landmarks as key navigation cues, little research has investigated how the quality of the landmark affects driver behavior.

METHOD

An empirical field trial in a real traffic environment was undertaken with 48 participants in order to assess the effect of landmark quality on driver behavior when navigating an unfamiliar, complex, urban route.

RESULTS

The use of good landmarks (as opposed to poor landmarks or distance information) as key verbal navigation cues resulted in significant improvements in navigation performance, driving performance, and driver confidence immediately preceding a turn. The use of distance information to locate a turn resulted in significantly more glances to the in-vehicle display.

CONCLUSIONS

Good landmarks offer significant safety and performance benefits to a driver navigating an unfamiliar route. Poor landmarks can result in driver performance worse than that obtained using distance to turn to locate forthcoming maneuvers.

APPLICATION

The design of future vehicle navigation systems should not rely on distance-to turn information alone to enable a driver to locate forthcoming maneuvers but, rather, should incorporate good landmarks within the navigation instructions they present to drivers.

Genotypic diversity of Escherichia coli isolated from cecal content and mucosa of one- to six-week-old broilers

Escherichia coli is a component of the microbiota of the avian digestive tract and is also part of some of the defined cultures used for competitive exclusion of Salmonella. Of particular interest are E. coli that are able to associate with the cecal wall because they might be part of a barrier that block pathogens from attaching and possibly from gaining entrance to intestinal tissues. In this study, repetitive element (rep)-PCR using the BOXA1R primer was used to differentiate between E. coli isolates obtained from cecal content and mucus of 1- to 6-wk-old broiler chickens. Computer-assisted analysis of the fingerprint patterns obtained from the isolates indicated the presence of 2 major groups of patterns. Collectively these 2 groups consisted of 28 clusters of patterns that differed from each other by 30% or more (dissimilarity index of > or = 0.3) and were therefore designated as operational taxonomic units. The patterns obtained from isolates from birds aged 1 to 5 wk were distributed almost equally between the 2 major groups, but approximately 90% of the patterns from isolates obtained from 6-wk-old birds belonged to only 1 of the 2 groups. The diversity of the fingerprints indicates that cecal mucus is inhabited by several types of E. coli in individual birds and in the birds housed together. Evidence for the preferential localization of specific E. coli within the cecal mucosa was not found, and therefore a range of E. coli must be able to associate tightly with the cecal mucosa.

Viable count estimates of lag time responses for Salmonella typhimurium M48 subjected to abrupt osmotic shifts

Generally, relative lag times (RLT; lag time divided by generation time) become extended as conditions become less favourable for growth. Mellefont et al. (2003, 2004) [Mellefont, L.A., McMeekin, T.A., Ross, T., 2003. The effect of abrupt osmotic shifts on the lag phase duration of foodborne bacteria. Int. J. Food Microbiol. 83(3), 281-293; Mellefont, L.A., McMeekin, T.A., Ross, T., 2004. The effect of abrupt osmotic shifts on the lag phase duration of physiologically distinct populations of Salmonella typhimurium. Int. J. Food Microbiol. 92, 111-120] reported that abrupt osmotic shifts of Salmonella typhimurium M48 from optimal to low aw led to unexpectedly small RLTs at low aw. In this study, RLTs resulting from similar osmotic shifts were estimated by viable count (VC) and compared to turbidimetric estimates to test the hypothesis that the 'downturn' in RLT is an artefact of the turbidimetric technique used. No 'downturn' in RLT was observed with VC data and RLTs increased with increasing magnitude of osmotic shift. Anomalous turbidimetric estimates of lag time at low aw were confirmed as the likely source of the 'downturn' in RLT. The abrupt osmotic shifts resulted in a complex pattern of microbial population behaviour. Immediately after transfer from optimal aw to low aw, inactivation of a portion of the population occurred for all the conditions tested. The degree of inactivation became progressively larger with larger shifts in aw. The initial decline in population was followed by a period during which no change in numbers occurred, followed by growth that appeared, in most cases, to be exponential. At the lowest aws tested (< or =0.954), the growth response after the initial decline was at a rate slower than that of exponential phase growth. Due to the use of non-selective media containing pyruvate (to eliminate oxygen radicals), the observed patterns of inactivation, lag and regrowth at most aw conditions are unlikely to result from a temporary loss of culturability, but may represent inactivation of a portion of the population.

Severe Community-Onset Pneumonia in Healthy Adults Caused by Methicillin-Resistant Staphylococcus aureus Carrying the Panton-Valentine Leukocidin Genes

BACKGROUND

Recent worldwide reports of community-onset skin abscesses, outbreaks of furunculosis, and severe pneumonia associated with methicillin-resistant Staphylococcus aureus (MRSA) carrying Panton-Valentine leukocidin (PVL) genes and the staphylococcal cassette chromosome mec (SCCmec) type IV indicate that MRSA infections are evolving into a community-related problem. The majority of cases reported to date involve skin and soft-tissue infections, with severe pneumonia representing a relatively rare phenomenon. During a 2-month period in the winter of 2003-2004, four healthy adults presented to 1 of 2 Baltimore hospitals with severe necrotizing MRSA pneumonia in the absence of typical risk factors for MRSA infection.

METHODS

Patients' MRSA isolates were characterized by strain typing with use of pulsed-field gel electrophoresis and SCCmec typing with use of a multiplex polymerase chain reaction (PCR) assay and detection of PVL genes by PCR.

RESULTS

All 4 patients' MRSA isolates carried the PVL genes and the SCCmec type IV element and belonged to the USA300 pulsed-field type. These 3 findings are among the typical characteristics of community-onset MRSA strains. In addition, 2 of our patients had concomitant influenza A diagnosed, which likely contributed to the severity of their presentation.

CONCLUSIONS

To our knowledge, these patients represent the first reported North American adults with severe community-onset MRSA pneumonia caused by strains carrying the PVL genes.

An outbreak of multidrug-resistant Acinetobacter baumannii associated with pulsatile lavage wound treatment

CONTEXT

Pulsatile lavage is a high-pressure irrigation treatment used increasingly in a variety of health care settings to debride wounds. Infection control precautions are not routinely used during the procedure and are not included in pulsatile lavage equipment package labeling.

OBJECTIVES

To investigate an outbreak of multidrug-resistant Acinetobacter baumannii and to test the hypothesis that pulsatile lavage wound treatment was the mode of transmission for the organism.

DESIGN

Outbreak case-control investigation including case identification, review of medical records, environmental cultures, and pulsed-field gel electrophoresis.

SETTING

A 1000-bed tertiary care hospital in Baltimore, Md, during September and October 2003.

PATIENTS

The investigation included 11 patients infected or colonized with multidrug-resistant A baumannii. Seven of these patients met the case definition for the case-control study and were compared with 28 controls randomly selected from a list of inpatients without multidrug-resistant A baumannii who had a wound care consultation.

MAIN OUTCOME MEASURE

Infection or colonization with multidrug-resistant A baumannii.

RESULTS

Eleven patients had cultures that grew multidrug-resistant A baumannii during the outbreak period. Of the 10 health care-associated cases, 8 had received pulsatile lavage treatment. One strain of multidrug-resistant A baumannii was recovered from all 6 pulsatile lavage patients who had isolates available for pulsed-field gel electrophoresis analysis and from multiple surfaces in the wound care area. Six of 7 cases (86%) were treated with pulsatile lavage vs 4 of 28 controls (14%) (odds ratio, 36; 95% confidence interval, 2.8-1721; P<.001). These results confirm that pulsatile lavage was a significant risk factor for acquisition of multidrug-resistant A baumannii.

CONCLUSIONS

Transmission was apparently caused by dissemination of multidrug-resistant A baumannii during the pulsatile lavage procedure, resulting in environmental contamination. Appropriate infection control precautions should be used during pulsatile lavage therapy and should be included in pulsatile lavage equipment labeling.

Intensive-care-unit-acquired bloodstream infections in a regional critically ill population

Bloodstream infection (BSI) is a serious complication of critical illness but it is uncertain whether acquisition of BSI in the intensive care unit (ICU) increases the risk of death. A study was conducted among all Calgary health region (population approximately 1 million) adults admitted to ICUs for 48 h or more during a three-year period to investigate the occurrence, microbiology and risk factors for developing an ICU-acquired BSI and to determine whether these infections independently predict mortality. One hundred and ninety-nine ICU-acquired BSI episodes occurred during 4933 ICU admissions for a cumulative incidence of 4% and an incidence density of 5.4 per 1000 ICU days. The most common isolates were Staphylococcus aureus (18%), coagulase-negative staphylococci (11%), and Enterococcus faecalis (8%); 12% of infections were due to antimicrobial-resistant bacteria. Admission to the regional neurosurgery/trauma ICU [odds ratio (OR) 2.86; 95% confidence interval (CI) 2.10-3.90] and increasing Acute Physiology and Chronic Health Evaluation II (APACHE II) score (OR 1.05 per point, 95% CI 1.03-1.07) were associated with higher risk, whereas a surgical diagnosis (OR 0.69; 95% CI 0.52-0.93) was associated with lower risk of developing ICU-acquired BSI in logistic regression analysis. The crude in-hospital death rate was 45% for patients with ICU-acquired BSI compared with 21% for those without (P < 0.0001) Development of an ICU-acquired BSI was an independent risk factor for death (OR 1.79; 95% CI 1.3-2.5) and increases the risk of dying from critical illness.

The effect of abrupt osmotic shifts on the lag phase duration of physiologically distinct populations of Salmonella typhimurium

Relative lag time (RLT), i.e. lag time divided by generation time, was used to characterise the lag phase response of exponential and stationary phase Salmonella typhimurium subjected to NaCl-mediated hyperosmotic shifts. Abrupt hyperosmotic shifts induced lag phases. The RLT, however, varied with the physiological history of the inoculum and the magnitude of the shift. Turbidimetric data showed that exponential phase cells had larger RLTs (up to approximately 8 units) than stationary phase cells (up to 2-4 units). Inocula containing exponential and stationary phase cells mixed in known proportions gave intermediate results. For viable count data, there was little difference in RLT between exponential and stationary phase cells. The RLT response determined turbidimetrically was reproducible for exponential phase cells, but less so for stationary phase cells. It is suggested that there may be a lower limit for resolution of RLT, in the range 0-2 units, and that this may account for the lack of reproducibility in RLTs of stationary phase cells. It is hypothesised that stationary phase cells have enhanced resistance to osmotic stress and are able to exploit new growth environments at low a(w) more rapidly than exponential phase cells, resulting in shorter lag phases. However, the data indicate that turbidimetry may not accurately describe the lag phase response of exponential phase cells subjected to large osmotic shifts. Viable count data is required to investigate this hypothesis further.

A 17-month evaluation of a chlorine dioxide water treatment system to control Legionella species in a hospital water supply

OBJECTIVE

To assess the safety and efficacy of a chlorine dioxide water treatment system in controlling Legionella in a hospital water supply.

DESIGN

For 17 months following installation of the system, we performed regular water cultures throughout the building, assessed chlorine dioxide and chlorite levels, and monitored metal corrosion.

RESULTS

Sites that grew Legionella species decreased from 41% at baseline to 4% (P = .001). L. anisa was the only species recovered and it was found in samples of both hot and cold water. Levels of chlorine dioxide and chlorite were below Environmental Protection Agency (EPA) limits for these chemicals in potable water. Further, enhanced carbon filtration effectively removed the chemicals, even at chlorine dioxide levels of more than twice what was used to treat the water. After 9 months, corrosion of copper test strips exposed to the chlorine dioxide was not higher than that of control strips. During the evaluation period, there were no cases of nosocomial Legionella in the building with the system, whereas there was one case in another building.

CONCLUSIONS

Our results indicate that operation of a chlorine dioxide system effectively removed Legionella species from a hospital water supply. Furthermore, we found that the system was safe, as levels of chlorine dioxide and chlorite were below EPA limits. The system did not appear to cause increased corrosion of copper pipes. Our results indicate that chlorine dioxide may hold promise as a solution to the problem of Legionella contamination of hospital water supplies.

The effect of abrupt shifts in temperature on the lag phase duration of Escherichia coli and Klebsiella oxytoca

The effect of temperature of incubation on lag times of two gram-negative foodborne bacteria was investigated. Bacteria were instantaneously transferred between temperatures within and beyond the normal physiological temperature range (NPTR). Abrupt temperature shifts induced lag phases, but the degree of the response was dependent on the direction and magnitude of the shift. Temperature downshifts induced larger relative lag times (RLT; the ratio of lag time to generation time), than equivalent upshifts. The hypothesis of Robinson et al. [Int. J. Food Microbiol. 44 (1998) 83] that lag time can be understood in terms of the amount of work to be done to adjust to new environmental conditions and the rate at which that work is done was supported. Deviation of the reported proportionality between lag time and generation time was observed when late-exponential phase cells were subjected to abrupt temperature shifts from beyond the normal physiological range.