Discrepancy between inferior vena cava and right atrial oxygen saturations as a sign of ischemia in the mesenteric circulation.

We describe the case of a 72-year-old patient admitted to intensive care following abdominal surgery. Venous oxygen saturations from the right atrium and superior vena cava (SVC) showed large variation due to ongoing ischemia in the mesentric circulation. If trends in venous oxygen saturation are to be followed, serial samples must be taken from the same central venous catheter (CVC) port.

Canadian Perspectives on Verocytotoxin-Producing Escherichia coli Infection †.

Infection with verocytotoxin-producing Escherichia coli (VTEC) became nationally reportable in 1990. Between 1990 and 1994, the national incidence of reported infections ranged from 3 to 5.3 per 100,000 inhabitants. Most cases are sporadic and are caused by E. coli O157:H7. Recent investigations have identified that, in addition to exposure to undercooked ground beef, contact with cattle, consumption of well water, and exposure to rural environments are important risk factors for VTEC infection. Also, results of case control studies and detection of asymptomatic fecal carriage of E. coli O157:H7 and other VTEC in farm family members and abattoir workers have led to an increasing emphasis on person-to-person spread in the epidemiology of VTEC infection. Controlling E. coli O157:H7 and other VTEC at the farm level may therefore have a broader impact than simply reducing the risk of foodborne VTEC infection. Longitudinal studies on dairy farms have demonstrated that E. coli O157:H7 carriage by cattle at the farm and animal level is often transient, and that cattle, rather than the farm environment, are the major reservoir for this organism on dairy farms. Small herds that are controlled by traditional management practices have the highest risk for VTEC infection. Further studies are likely to result in development of effective strategies to control VTEC at the farm level.

Use of Luminescent Strains of Salmonella enteritidis To Monitor Contamination and Survival in Eggs.

Fresh and retail eggs were exposed to luminescent S. enteritidis cultures containing from 104 to 109 CFU/ml at either room temperature (approximately 21°C) for 3 days or 40°C for 16 h. The entry of S. enteritidis through egg shell was evidenced by luminescence in the eggs which was visualized using an Image Quantifier. The rate of contamination of the eggs increased with increasing inoculum size. Scanning electron microscopy was used to confirm the position of S. enteritidis cells in the eggs. The survival rate of the Salmonella cells in liquid eggs and whole shell eggs during storage at 4°C was investigated. Although S. enteritidis did not grow in eggs during storage at 4°C for up to 8 weeks, cells were able to survive. Under these storage conditions, the count was reduced by 1.7 to 2.5 log cycles per g in liquid egg and 0.8 to 1.4 log cycle per g in whole shell eggs. Similar trends were observed using both plate count and luminescence to monitor survival.

Growing Concerns and Recent Outbreaks Involving Non-O157:H7 Serotypes of Verotoxigenic Escherichia coli.

Verocytotoxin-producing E. coli (VTEC) of serotype O157:H7 have been shown to be important agents of foodborne disease in humans worldwide. While the majority of research effort has been targeted on this serotype it is becoming more evident that other serotypes of VTEC can also be associated with human disease. An increasing number of these non-O157:H7 VTEC have been isolated from humans suffering from HUS and diarrhea. Recently a number of foodborne outbreaks in the USA, Australia, and other countries have been attributed to non-O157:H7 VTEC serotypes. Surveys of animal populations in a variety of countries have shown that the cattle reservoir contains more than 100 serotypes of VTEC, many of which are similar to those isolated from humans. The diversity and complexity of the VTEC family requires that laboratories and public health surveillance systems have the ability to detect and monitor all serotypes of VTEC.

Variability and Determinants of Carcass Bacterial Load at a Poultry Abattoir.

Roaster chicken carcasses (2,928) were collected from the evisceration line of a poultry abattoir over a 5-month period and identified as to the lot (truck load) and supplier. Bacterial load was determined by mechanically rinsing each eviscerated carcass in sterile water and then using an automated hydrophobic grid membrane interpreter system to obtain the log10 most probable number of aerobic bacteria per gram of carcass. Analysis of variance demonstrated that the between-carcass, between-lots-within-supplier, and between-supplier components of variability in bacterial load represented 73.2, 14.2, and 12.6% of the total variability, respectively. There was a significant (p < 0.001) supplier and lots-within-supplier effect on bacterial load of carcasses. A regression model demonstrated that bacterial load of lots significantly (p ≤ 0.05) decreased with increasing hours of operation of the evisceration line. Factors in the model which were significantly (p ≤ 0.05) associated with increased bacterial load included longer crating and holding times, higher visible contamination scores, slaughter during winter months, higher outdoor temperatures, and slaughter of lots composed of only pullets. The model explained about 23% of the variability in bacterial load.

Variability in Broiler Carcass Bacterial Load at Three Abattoirs, as Measured by a Hydrophobic Grid Membrane Filter Interpreter.

In this observational study, the variability of broiler carcass bacterial load was investigated at three federally inspected abattoirs, using an automated hydrophobic grid membrane filter interpreter system. The measurement protocol involved: whole carcass rinses aided by a mechanical carcass shaker; filtration of rinse solutions through hydrophobic grid membrane filters (HGMF) (ISO-GRID®, QA Laboratories, Ltd., Toronto, Ont.); and use of an automated HGMF interpreter (MI-100 HGMF Interpreter System, Richard Brancker Research, Ltd., Ottawa, Ont.). Carcass and lot mean bacterial loads were measured, respectively, in units of log10 most probable number (MPN) of mesophylic aerobic colony forming units per gram of carcass (LgMPN/g), and slaughter lot mean LgMPN/g (LMLgMPN/g). Whole carcass rinses were conducted on a total of 1,917 carcasses, among 96 slaughter lots from three abattoirs. Overall, the LgMPN/g ranged from 1.054 to 4.180 with a mean of 2.585 and a variance of 0.263. These corresponded to MPN/g counts from 11 to 15,135 and a geometric mean of 385 MPN/g. Statistically significant differences were observed between abattoirs and between lots within abattoirs. The intra-abattoir correlation coefficient of LgMPN/g was r = 0.180 (p < 0.001). The within abattoir intralot correlation coefficient was r = 0.259 (p < 0.001). In this data set, approximately 56, 26, and 18% of the variability in LgMPN/g were attributed to factors operating at the individual bird, lot, and abattoir levels of organization, respectively. Factors significantly associated with LMLgMPN/g included: abattoir (p < 0.001), transportation time from farm to abattoir (p < 0.001), and waiting time from arrival at the abattoir yard to actual slaughter (p = 0.002). Analysis of a series of five repeat rinses, conducted on one bird from each of the 96 study lots, demonstrated that bacterial counts in the second to fifth sequential rinses were positively associated with the bacterial count of the first rinse. Also, after adjusting for the initial count, a pattern of decreasing counts was observed in subsequent rinses.

Application of an Automated Hydrophobic Grid Membrane Filter Interpreter System at a Poultry Abattoir.

The performance of a system to measure broiler carcass hygiene was investigated in the abattoir environment. The system involved: whole carcass rinses aided by a mechanical carcass shaker; filtration of rinse solutions though hydrophobic grid membrane filters (HGMF) (ISO-GRIDR, QA Laboratories Ltd.); and use of an automated HGMF interpreter. The interpreter recorded culture results in units of most probable number (MPN) of aerobic bacteria, in electronic data files (MI-100 HGMF Interpreter System, Richard Brancker Research Ltd.). Set-up and operation of the system by government inspection staff at an abattoir ran relatively smoothly with minimal interference to normal plant operation. The system demonstrated good repeatability in measuring log10 most probable number per gram of carcass (LgMPN/g), between repeat readings of the same filters (r=0.993 p<0.001), and good repeatability between repeat filters within the same carcass rinses (r=0.970 p<0.001). Overall, the LgMPN/g ranged from 0.258 to 3.955 with a mean of 2.276 and a variance of 0.324. These corresponded to MPN/g counts in the range of 2 to 9000 and a geometric mean of 188.8 MPN/g. A regression model was developed to investigate poultry supplier and abattoir effects on the variability of counts. A significant supplier effect was observed. The addition of two more carcass showers located just after the venting machine along the evisceration line was not associated with a change in carcass hygiene.

A Prevalence Survey of Salmonella in Raw Milk in Ontario, 1986-87.

In a survey to determine the incidence and prevalence of Salmonella in the bulk milk supply of dairy farms in southwestern Ontario 1986-87, milk filters from 813 farms were cultured over four sampling periods in six months. Prevalence rates during the four sampling periods were as follows: September 1986: 1.23%; October-November: 0.40%; December-January: 0.19%; and February 1987: 0%. Incidence rates increased from 0.15% per month in the first sampling period to 0.20% in the second and third period, then dropped to 0% in the fourth sampling period. Eight isolates of S. muenster and two of S. mbandaka were recovered from nine different farms. All of the isolates were sensitive to the commonly used antimicrobials tested. Owing to the steady decline in the prevalence over the study period, no seasonal patterns were apparent. The results of this survey indicate that the presence of Salmonella in bulk milk supplies is dynamic.