The ASOS Surgical Risk Calculator: development and validation of a tool for identifying African surgical patients at risk of severe postoperative complications

BACKGROUND

The African Surgical Outcomes Study (ASOS) showed that surgical patients in Africa have a mortality twice the global average. Existing risk assessment tools are not valid for use in this population because the pattern of risk for poor outcomes differs from high-income countries. The objective of this study was to derive and validate a simple, preoperative risk stratification tool to identify African surgical patients at risk for in-hospital postoperative mortality and severe complications.

METHODS

ASOS was a 7-day prospective cohort study of adult patients undergoing surgery in Africa. The ASOS Surgical Risk Calculator was constructed with a multivariable logistic regression model for the outcome of in-hospital mortality and severe postoperative complications. The following preoperative risk factors were entered into the model; age, sex, smoking status, ASA physical status, preoperative chronic comorbid conditions, indication for surgery, urgency, severity, and type of surgery.

RESULTS

The model was derived from 8799 patients from 168 African hospitals. The composite outcome of severe postoperative complications and death occurred in 423/8799 (4.8%) patients. The ASOS Surgical Risk Calculator includes the following risk factors: age, ASA physical status, indication for surgery, urgency, severity, and type of surgery. The model showed good discrimination with an area under the receiver operating characteristic curve of 0.805 and good calibration with c-statistic corrected for optimism of 0.784.

CONCLUSIONS

This simple preoperative risk calculator could be used to identify high-risk surgical patients in African hospitals and facilitate increased postoperative surveillance.

CLINICAL TRIAL REGISTRATION

NCT03044899.

Bacterial populations associated with meat from the deboning room of a high throughput red meat abattoir

Developing countries are faced with high incidences of food poisoning outbreaks, with obvious economic consequences. In highly perishable foodstuffs such as fresh red meat the threat of food poisoning is particularly intense. In this study, red meat samples were collected from a deboning room of a high throughput abattoir. The samples were analysed for the presence of Bacillus cereus., Staphylococcus aureus., Pseudomonas spp., Listeria monocytogenes., Escherichia coli and Salmonella spp. The aerobic plate counts as well as Enterobacteriaceae were also enumerated. Almost without exception the counts exceeded the microbiological guidelines for raw meat as proposed by the South African Department of Health. The average B. cereus count over the sampling period was 8.32 × 10(3) cfu, g (-1), for S. aureus and Pseudomonas spp. 1.72 × 10(5) and 1.7 × 10(5) cfu g(-1) respectively and for E. coli 3.4 × 10(5) cfu g(-1). Sixty percent of the samples were positive for presumptive Salmonella spp. while 52% of the samples tested positive for the presence of L. monocytogenes. The aerobic plate and Enterobacteriaceae counts were 1.7 × 10(7) and 4.6 × 10(6) cfu g(-1), respectively. The data highlighted the need for a more systematic approach to ensuring safe food through implementing quality control methods to prevent the entry and proliferation of pathogens in meat and meat products, especially during processes with a high degree of handling, such as deboning.

Microbial Composition in Bioaerosols of a High-Throughput Chicken-Slaughtering Facility

The microbial composition of the air in various areas of a high-throughput chicken-slaughtering facility was investigated. Over a 4-mo period, 6 processing areas were sampled, and the influence of environmental factors was monitored. The highest counts of microorganisms were recorded in the initial stages of processing, comprising the receiving-killing and defeathering areas, whereas counts decreased toward the evisceration, air-chilling, packaging, and dispatch areas. Maximum microbial counts were as follows: coliforms, 4.9 x 10(3) cfu/m(3); Escherichia coli 3.4 x 10(3) cfu/m(3); Bacillus cereus, 5.0 x 10(4) cfu/m(3); Staphylococcus aureus, 1.6 x 10(4) cfu/m(3); Pseudomonas aeruginosa, 7.0 x 10(4) cfu/m(3); presumptive Salmonella spp., 1.5 x 10(4) cfu/m(3); Listeria monocytogenes, 1.6 x 10(4) cfu/m(3); and fungi, 1.4 x 10(4) cfu/m(3). Higher counts of airborne microorganisms found in the receiving-killing and defeathering areas indicate the importance of controlling microbial levels before processing to prevent the spread of organisms downstream. This should limit the risk of carrying over contaminants from areas known to generate high counts to areas where the final food product is exposed to air and surface contamination.

Influence of commercial sanitizers on lipopolysaccharide production by Salmonella Enteritidis ATCC 13076

The effect of typical sanitizers on the composition and toxicity of lipopolysaccharides (LPSs) produced by Salmonella Enteritidis ATCC 13076 was analyzed. Salmonella Enteritidis was propagated up to the late exponential phase in the presence of commercial sanitizing solutions. LPS was extracted and derivatized with trifluoroacetylation, and gas chromatography-mass spectrometry analysis and the chromogenic Limulus amoebocyte lysate assay were used to assess the ultrastructure and toxicity of the LPS. The viability and debris formation during growth were evaluated to verify the bactericidal and bacteriostatic effects of the sanitizers and to assess sanitizer effects on LPS formation. The LPSs produced were quantified at 1.7 x 10(4), 1.2 x 10(4), 3.6 x 10(3), and 9.6 x 10(4) [KDO] x OD(620nm)(-1) for the controls and the organisms grown in the presence of a chlorinated sanitizer, a heavy-duty alkaline cleaner, and a phenolic hand wash solution, respectively. In response to these treatments, the short-chain polysaccharide fractions of the LPSs in the Salmonella Enteritidis cells increased. This finding suggests that this organism increases the low-molecular-weight fraction of the LPS in relation to the high-molecular-weight fraction to survive these unfavorable conditions. The cumulative change in the LPS in response to the sanitizers influenced the toxicity of the LPS; however, this change could not be related to an individual compound within any of the assessed fractions.

The distribution of Staphylococci in bioaerosols from red-meat abattoirs

The quality and shelf-life of perishable foodstuffs can be reduced by high concentrations in the processing environment of bioaerosols consisting of spoilage microbiota. A lack of documented literature on the distribution of such bioaerosols has, however, led to the underestimation of their impact. In the study reported here, the deboning rooms of selected South African red-meat abattoirs were investigated for airborne concentrations of staphylococci; the authors studied the distribution of Staphylococcus species in general, as well as the coagulase types of Staphylococcus aureus in particular. Average staphylococci bioaerosol concentrations varied considerably among the abattoirs investigated, with Abattoir B having the highest counts (3 x 10(2) CFUs/m3) and Abattoir A having the lowest (7.6 CFUs/m3). There was a significant link between bioaerosols and microbial loads from red meat in the same environment. The recorded levels were, however, well below the recommended maximum limits for bioaerosols suggested by various international and governmental authorities. Staphylococcus xylosus and S. saprophyticus were found to be the most abundant species in the air of the deboning rooms, while among S. aureus coagulase types, Type III and Type VIII were predominant. On the basis of the ecology of the bacterial groups, the authors suggest probable sources of staphylococcal bioaerosols and propose strategies that could be developed for red-meat abattoirs to reduce the levels of airborne pathogens.

The influence of sanitizers on the lipopolysaccharide composition of Escherichia coli O111

This study focused on the influence of typical sanitizers on the composition of the lipopolysaccharides (LPS) produced by the verocytotoxin-producing (VTEC) Escherichia coli O111. We also aimed to cast light on the applicability of O-antigen-based serotyping and endotoxin based Limulus Amebocyte Lysate (LAL) assays applied in the food industry for the identification and quantification of Gram-negative bacteria. E. coli O111 was propagated in the presence of three typical commercially applied sanitizing solutions that included a Clean in Place (CIP) chlorinated sanitizer (bacteriocidal), heavy-duty alkaline sanitizer (bacteriocidal) and a phenolic hand wash solution (bacteriostatic). After the required growth phase was reached the LPS from both the intact cells and debris was extracted and methanolysed followed by trifluoroacetylation. Subsequently GC-MS analysis and the chromogenic LAL assay were applied to assess both the ultra-structure and the toxicity of the extracted LPS. The viability and debris formation during growth was also evaluated to verify the bacteriocidial and static effect of the applied sanitizers as well as to assess its relationship with LPS formation. The total LPS produced was quantified at 1.3 x 10(6) [KDO] x OD(620 nm)(-1) for the control samples, 6.5 x 10(3) [KDO] x OD(620 nm)(-1) for E. coli grown in the presence of CIP chlorinated sanitizer and 2.1 x 10(5) and 2.85 x 10(6) [KDO] x OD(620 nm)(-1) for the organisms grown in the presence of heavy-duty alkaline sanitizer and phenolic hand wash solution respectively (KDO = 2-keto-3-deoxy-octulosonic acid). A negative correlation (gamma(2)= -0.880) between the [KDO] and Delta viability was evident and indicated that E. coli O111 responds to factors that hinder viability by producing more LPS in its outer membrane. Subsequent assessment of the LPS ultra-structure revealed a definite change in both the total assessed saccharide and lipid fractions. The cumulative change of the LPS in response to the sanitizers further appeared to influence the toxicity of the LPS as the latter change could not be related to an individual compound within any of the assessed fractions. This emphasised the fact that the quantity of LPS obtained from E. coli O111 in this study, did not seem to determine the toxicity of the organism. From the results we further propose a coefficient that could be applied to describe the response of E. coli O111 LPS to sanitizers and caution against the application of serotyping (based on the O-antigen) and the LAL assay to quantify and identify E. coli O111 obtained from food strata where the possibility of sanitizer contamination exists.

Quantification of Bioaerosols in Automated Chicken Egg Production Plants

The quantity and composition of bioaerosols in a typical automated chicken egg layer management system (LMS) with a controlled internal climate (B) and without (A) were compared. The LMS-A used a fecal matter disposal system featuring a central opening in the floor through which the matter automatically dropped to an open-air lower level; the LMS-B used a conveyer belt below each hen battery set, which removed the fecal matter frequently. Bioaerosols were collected by impaction on agar. Humidity, wind velocity, temperature, and dust particle concentration were also analyzed at several locations in the LMS. The average bioaerosol concentrations (total viable aerobic bacteria) associated with the inside of LMS-A reached X = 1.1 x 10(5) cfu/m3 with counts in LMS-B being X = 9.2 x 10(4) cfu/m3. In both systems, the bacterial counts were significantly higher on the inside of the LMS than the outside. The LMS-A showed yeast counts of X = 6.7 x 10(1) cfu/m3 with none detectable in LMS-B. Total culturable mold counts were X = 7.0 x 10(2) cfu/m3, with significantly higher presumptive Salmonella spp. counts (X = 6.6 x 10(1) cfu/m3) inside both LMS when compared with the outside. Escherichia coli and total culturable gram-negative counts were significantly higher in LMS-B at concentrations of X = 3.6 x 10(1) cfu/m3. These counts were significantly higher compared with the outside environment. We concluded that the live birds were the major source of bioaerosols in both LMS, with the fecal matter disposal systems attributing to the difference in bioaerosol composition. Modifications to the operation protocols of both LMS to limit the contamination of eggs by bioaerosols are suggested.

Extraction methods for lipopolysaccharides from Escherichia coli ATCC 25922 for quantitative analysis by capillary electrophoresis

Lipopolysaccharides (LPS) are major constituents of the cell wall of Gram-negative bacteria. Capillary zone electrophoresis (CZE) was applied to distinguish between lipopolysaccharides extracted from Escherichia coli ATCC 25922 with various techniques. Extraction methods proposed by Westphal and Jann [Methods Carbohydr. Chem. 5 (1965) 83], Galanos et al. [Eur. J. Biochem. 9 (1969) 245], Ni Eidhin and Mouton [FEMS Microbiol. Lett. 110 (1993) 133] and Nichols [Infect. Immun. 62 (1994) 3753] for LPS preparation were evaluated. Electrophoresis buffers with varying pHs were applied to assess the structure stability of the extracted LPS samples. Variations in structural breakdown were apparent demonstrating that different extraction methods removed different LPS molecules. Furthermore, the results obtained proved the CZE useful as an analytical technique for LPS evaluation. The LPS removed with the Nichols extraction procedure presented a unique electrophorogram that could in future be applied in the rapid identification of Gram-negative foodborne pathogens.

Ascospore aggregation and oxylipin distribution in the yeast Dipodascopsis tothii

Upon cultivation of the yeast Dipodascopsis tothii in its sexual stage, small ascospores are released individually from the ascus tip, which then assemble in sheathed cluster balls. In contrast to Dipodascopsis uninucleata, this yeast produced smooth bean shaped ascospores with sheath-like appendages that assemble in a disordered sheathed ball of ascospores outside the ascus. Strikingly, upon release, the ascus tip contained 3-hydroxy oxylipins, while the released ascospore clusters contained little or no 3-hydroxy oxylipins as indicated by immunofluorescence microscopy. In D. uninucleata, these oxylipins are concentrated on the spore surface and interspore matrix, but not on the ascus tip.

A novel oxylipin-associated 'ghosting' phenomenon in yeast flocculation

Research on the distribution of oxylipins (3-hydroxy fatty acids) in flocculant strains of the yeast Saccharomyces cerevisiae led to the uncovering of a novel 'ghosting' phenomenon observed during assumed lectin-mediated aggregation. We found that intracellular oxylipin-containing osmiophilic layers migrate through yeast cell walls in a 'ghostlike' fashion without visually affecting the cell wall structure or the layers. This migration resulted in the binding of these layers to cell walls of adjacent cells. Consequently, 'ghosting' seems a prerequisite for flocculation to occur. However, 'ghosting' alone may not be sufficient to ensure flocculation.

An acetylsalicylic acid-sensitive aggregation phenomenon in Dipodascopsis uninucleata

Aggregation of ascospores has been discovered in the yeast Dipodascopsis uninucleata. When this yeast is cultivated to reach the sexual reproductive stage, small ascospores are individually released from the tip of a sac-like ascus which then aggregate in orderly clusters. Acetylsalicylic acid (ASA) inhibited ascospore release and subsequent ordered aggregation process. We suggest that novel ASA-sensitive oxidised fatty acids (3R-hydroxy-oxylipins) and small hooks located on the surface of these ascospores, are involved.

Biological dynamics and distribution of 3-hydroxy fatty acids in the yeast Dipodascopsis uninucleata as investigated by immunofluorescence microscopy. Evidence for a putative regulatory role in the sexual reproductive cycle

Dipodascopsis uninucleata has been recently shown to produce 3-hydroxy polyenoic fatty acids from several exogenous polyenoic fatty acids. In order to examine whether endogenous 3-hydroxy fatty acids (3-OH-FA) may be implicated in the developmental biology of this yeast, we mapped by immunofluorescence microscopy their occurrence in fixed cells with or without cell walls using an antibody raised against 3R-hydroxy-5Z,8Z,11Z,14Z-eicosatetraenoic acid (3R-HETE), the biotransformation product from arachidonic acid (AA). This antibody turned out to cross-react with other 3-OH-FA. 3-OH-FA were detected in situ in gametangia, asci, as well as between released ascospores, and proved to be associated with the sexual reproductive stage of the life cycle of the yeast. Acetylsalicylic acid (1 mM), which is known to suppress the formation of 3-OH-FA from exogenous polyenoic fatty acids, inhibited the occurrence of immunoreactive material as well as the sexual phase of the life cycle suggesting a prominent regulatory role of 3-OH-FA for the latter.

Production of 3R-hydroxy-polyenoic fatty acids by the yeast Dipodascopsis uninucleata

Various fatty acids were fed to the yeast Dipodascopsis uninucleata UOFS Y 128, and the extracted samples were analyzed for the accumulation of 3-hydroxy metabolites with the help of electron impact gas chromatography-mass spectrometry. Fatty acids containing of 5Z,8Z-diene system (5Z,8Z,11Z-eicosatrienoic, 5Z,8Z,11Z,14Z-eicosatetraenoic, and 5Z,8Z,11Z,14Z,17Z-eicosapentaenoic acids) yielded the corresponding 3-hydroxy-all-Z-eicosapolyenoic acids. Moreover, linoleic acid (9Z,12Z-octadecadienoic acid) and 11Z,14Z,17Z-eicosatrienoic acid were converted to the 3-hydorxylated metabolites of shorter chain length, e,g., 3-hydroxy-5Z,8Z-tetradecadienoic acid and 3-hydroxy-5Z,8Z,11Z-tetradecatrienoic acid, respectively. In contrast, no accumulation of a 3-hydroxy metabolite was observed with oleic acid (9Z-octadecenoic acid), linolelaidic acid (9E,12E-octadecadienoic acid), gamma-linolenic acid (6Z,9Z,12Z-octadecatrienoic acid), and eicosanoic acid as substrate. These findings pinpoint that the 3-hydroxylation of a fatty acid in Dipodascopsis uninucleata requires a 5Z,8Z-diene system either directly or following initial incomplete beta-oxidation. Following analysis of the enantiomer composition, the arachidonic acid metabolite was identified as 3R-hydroxy-5Z,8Z,11Z,14Z-eicosatetraenoic acid, which rules out a normal beta-oxidation as biosynthetic route to this new class of oxylipins.