Attachment of Salmonella spp. to chicken muscle surfaces

Aerobic plate count, Salmonella and Campylobacter loads of whole bird carcass rinses from pre-chillers with different water management strategies in a commercial poultry processing plant

Salmonella and Campylobacter are significant issues for poultry processors because of increasing regulatory standards as well as public health concerns. The goal of this study is to report the effects of two different pre-chiller systems that utilize different temperatures and water recirculation systems on whole bird carcass rinsates. Both pre-chiller tanks were contained within a single poultry processing facility and operated at different temperatures and water systems. The incidence of Campylobacter spp. and Salmonella spp., as well as the aerobic plate counts on whole bird carcass rinses are reported in this study from each pre-chiller system. The results from this study reveal that there are significant differences in how microbial populations and pathogens change over time in each pre-chiller system. Furthermore, we identify that these patterns are different per system. Such data are impactful as it indicates that measuring carcasses within a plant must consider both temperature and water recirculation as it may prevent comparability of different lines within a single processing facility.

Efficacy of Lactic Acid, Lactic Acid-Acetic Acid Blends, and Peracetic Acid To Reduce Salmonella on Chicken Parts under Simulated Commercial Processing Conditions

The poultry processing industry has been undergoing a series of changes as it modifies processing practices to comply with new performance standards for chicken parts and comminuted poultry products. The regulatory approach encourages the use of intervention strategies to prevent and control foodborne pathogens in poultry products and thus improve food safety and protect human health. The present studies were conducted to evaluate the efficacy of antimicrobial interventions for reducing Salmonella on inoculated chicken parts under simulated commercial processing conditions. Chicken pieces were inoculated by immersion in a five-strain Salmonella cocktail at 6 log CFU/mL and then treated with organic acids and oxidizing agents on a commercial rinsing conveyor belt. The efficacy of spraying with six different treatments (sterile water, lactic acid, acetic acid, buffered lactic acid, acetic acid in combination with lactic acid, and peracetic acid) at two concentrations was evaluated on skin-on and skin-off chicken thighs at three application temperatures. Skinless chicken breasts were used to evaluate the antimicrobial efficacy of lactic acid and peracetic acid. The color stability of treated and untreated chicken parts was assessed after the acid interventions. The lactic acid and buffered lactic acid treatments produced the greatest reductions in Salmonella counts. Significant differences between the control and water treatments were identified for 5.11% lactic acid and 5.85% buffered lactic acid in both skin-on and skin-off chicken thighs. No significant effect of treatment temperature for skin-on chicken thighs was found. Lactic acid and peracetic acid were effective agents for eluting Salmonella cells attached to chicken breasts.

Neural Network Model for Thermal Inactivation of Salmonella Typhimurium to Elimination in Ground Chicken: Acquisition of Data by Whole Sample Enrichment, Miniature Most-Probable-Number Method

Predictive models are valuable tools for assessing food safety. Existing thermal inactivation models for Salmonella and ground chicken do not provide predictions above 71°C, which is below the recommended final cooked temperature of 73.9°C for chicken. They also do not predict when all Salmonella are eliminated without extrapolating beyond the data used to develop them. Thus, a study was undertaken to develop a model for thermal inactivation of Salmonella to elimination in ground chicken at temperatures above those of existing models. Ground chicken thigh portions (0.76 cm³) in microcentrifuge tubes were inoculated with 4.45 ± 0.25 log most probable number (MPN) of a single strain of Salmonella Typhimurium (chicken isolate). They were cooked at 50 to 100°C in 2 or 2.5°C increments in a heating block that simulated two-sided pan frying. A whole sample enrichment, miniature MPN (WSE-mMPN) method was used for enumeration. The lower limit of detection was one Salmonella cell per portion. MPN data were used to develop a multiple-layer feedforward neural network model. Model performance was evaluated using the acceptable prediction zone (APZ) method. The proportion of residuals in an APZ (pAPZ) from -1 log (fail-safe) to 0.5 log (fail-dangerous) was 0.911 (379 of 416) for dependent data and 0.910 (162 of 178) for independent data for interpolation. A pAPZ ≥0.7 indicated that model predictions had acceptable bias and accuracy. There were no local prediction problems because pAPZ for individual thermal inactivation curves ranged from 0.813 to 1.000. Independent data for interpolation satisfied the test data criteria of the APZ method. Thus, the model was successfully validated. Predicted times for a 1-log reduction ranged from 9.6 min at 56°C to 0.71 min at 100°C. Predicted times for elimination ranged from 8.6 min at 60°C to 1.4 min at 100°C. The model will be a valuable new tool for predicting and managing this important risk to public health.

Salmonella enterica Serovar Kentucky Flagella Are Required for Broiler Skin Adhesion and Caco-2 Cell Invasion

Nontyphoidal Salmonella strains are the main source of pathogenic bacterial contamination in the poultry industry. Recently, Salmonella enterica serovar Kentucky has been recognized as the most prominent serovar on carcasses in poultry-processing plants. Previous studies showed that flagella are one of the main factors that contribute to bacterial attachment to broiler skin. However, the precise role of flagella and the mechanism of attachment are unknown. There are two different flagellar subunits (fliC and fljB) expressed alternatively in Salmonella enterica serovars using phase variation. Here, by making deletions in genes encoding flagellar structural subunits (flgK, fliC, and fljB), and flagellar motor (motA), we were able to differentiate the role of flagella and their rotary motion in the colonization of broiler skin and cellular attachment. Utilizing a broiler skin assay, we demonstrated that the presence of FliC is necessary for attachment to broiler skin. Expression of the alternative flagellar subunit FljB enables Salmonella motility, but this subunit is unable to mediate tight attachment. Deletion of the flgK gene prevents proper flagellar assembly, making Salmonella significantly less adherent to broiler skin than the wild type. S Kentucky with deletions in all three structural genes, fliC, fljB, and flgK, as well as a flagellar motor mutant (motA), exhibited less adhesion and invasion of Caco-2 cells, while an fljB mutant was as adherent and invasive as the wild-type strain.

IMPORTANCE

In this work, we answered clearly the role of flagella in S Kentucky attachment to the chicken skin and Caco-2 cells. We demonstrated that the presence of FliC is necessary for attachment to broiler skin. Expression of the alternative flagellar subunit FljB enables Salmonella motility, but this subunit is unable to mediate strong attachment. Deletion of the flgK gene prevents proper flagellar assembly, making Salmonella significantly less adherent to broiler skin than the wild type. S Kentucky with deletions in all three structural genes, fliC, fljB, and flgK, as well as a flagellar motor mutant (motA), exhibited less adhesion and invasion of Caco-2 cells, while an fljB mutant was as adherent and invasive as the wild-type strain. We expect these results will contribute to the understanding of the mechanisms of Salmonella attachment to food products.

Identification of Salmonella enterica serovar Kentucky genes involved in attachment to chicken skin

BACKGROUND

Regardless of sanitation practices implemented to reduce Salmonella prevalence in poultry processing plants, the problem continues to be an issue. To gain an understanding of the attachment mechanism of Salmonella to broiler skin, a bioluminescent-based mutant screening assay was used. A random mutant library of a field-isolated bioluminescent strain of Salmonella enterica serovar Kentucky was constructed. Mutants' attachment to chicken skin was assessed in 96-well plates containing uniform 6 mm diameter pieces of circular chicken skin. After washing steps, mutants with reduced attachment were selected based on reduced bioluminescence, and transposon insertion sites were identified.

RESULTS

Attachment attenuation was detected in transposon mutants with insertion in genes encoding flagella biosynthesis, lipopolysaccharide core biosynthesis protein, tryptophan biosynthesis, amino acid catabolism pathway, shikimate pathway, tricarboxylic acid (TCA) cycle, conjugative transfer system, multidrug resistant protein, and ATP-binding cassette (ABC) transporter system. In particular, mutations in S. Kentucky flagellar biosynthesis genes (flgA, flgC, flgK, flhB, and flgJ) led to the poorest attachment of the bacterium to skin.

CONCLUSIONS

The current study indicates that attachment of Salmonella to broiler skin is a multifactorial process, in which flagella play an important role.

Infiltration of Matrix-Non-producers Weakens the Salmonella Biofilm and Impairs Its Antimicrobial Tolerance and Pathogenicity

Bacterial biofilms display a collective lifestyle, wherein the cells secrete extracellular polymeric substances (EPS) that helps in adhesion, aggregation, stability, and to protect the bacteria from antimicrobials. We asked whether the EPS could act as a public good for the biofilm and observed that infiltration of cells that do not produce matrix components weakened the biofilm of Salmonella enterica serovar Typhimurium. EPS production was costly for the producing cells, as indicated by a significant reduction in the fitness of wild type (WT) cells during competitive planktonic growth relative to the non-producers. Infiltration frequency of non-producers in the biofilm showed a concomitant decrease in overall productivity. It was apparent in the confocal images that the non-producing cells benefit from the EPS produced by the Wild Type (WT) to stay in the biofilm. The biofilm containing non-producing cells were more significantly susceptible to sodium hypochlorite and ciprofloxacin treatment than the WT biofilm. Biofilm infiltrated with non-producers delayed the pathogenesis, as tested in a murine model. The cell types were spatially assorted, with non-producers being edged out in the biofilm. However, cellulose was found to act as a barrier to keep the non-producers away from the WT microcolony. Our results show that the infiltration of non-cooperating cell types can substantially weaken the biofilm making it vulnerable to antibacterials and delay their pathogenesis. Cellulose, a component of EPS, was shown to play a pivotal role of acting as the main public good, and to edge-out the non-producers away from the cooperating microcolony.

Application of Molecular Approaches for Understanding Foodborne Salmonella Establishment in Poultry Production

Salmonellosis in the United States is one of the most costly foodborne diseases. Given that Salmonella can originate from a wide variety of environments, reduction of this organism at all stages of poultry production is critical. Salmonella species can encounter various environmental stress conditions which can dramatically influence their survival and colonization. Current knowledge of Salmonella species metabolism and physiology in relation to colonization is traditionally based on studies conducted primarily with tissue culture and animal infection models. Consequently, while there is some information about environmental signals that control Salmonella growth and colonization, much still remains unknown. Genetic tools for comprehensive functional genomic analysis of Salmonella offer new opportunities for not only achieving a better understanding of Salmonella pathogens but also designing more effective intervention strategies. Now the function(s) of each single gene in the Salmonella genome can be directly assessed and previously unknown genetic factors that are required for Salmonella growth and survival in the poultry production cycle can be elucidated. In particular, delineating the host-pathogen relationships involving Salmonella is becoming very helpful for identifying optimal targeted gene mutagenesis strategies to generate improved vaccine strains. This represents an opportunity for development of novel vaccine approaches for limiting Salmonella establishment in early phases of poultry production. In this review, an overview of Salmonella issues in poultry, a general description of functional genomic technologies, and their specific application to poultry vaccine developments are discussed.

Biofilm formation by enteric pathogens and its role in plant colonization and persistence

The significant increase in foodborne outbreaks caused by contaminated fresh produce, such as alfalfa sprouts, lettuce, melons, tomatoes and spinach, during the last 30 years stimulated investigation of the mechanisms of persistence of human pathogens on plants. Emerging evidence suggests that Salmonella enterica and Escherichia coli, which cause the vast majority of fresh produce outbreaks, are able to adhere to and to form biofilms on plants leading to persistence and resistance to disinfection treatments, which subsequently can cause human infections and major outbreaks. In this review, we present the current knowledge about host, bacterial and environmental factors that affect the attachment to plant tissue and the process of biofilm formation by S. enterica and E. coli, and discuss how biofilm formation assists in persistence of pathogens on the plants. Mechanisms used by S. enterica and E. coli to adhere and persist on abiotic surfaces and mammalian cells are partially similar and also used by plant pathogens and symbionts. For example, amyloid curli fimbriae, part of the extracellular matrix of biofilms, frequently contribute to adherence and are upregulated upon adherence and colonization of plant material. Also the major exopolysaccharide of the biofilm matrix, cellulose, is an adherence factor not only of S. enterica and E. coli, but also of plant symbionts and pathogens. Plants, on the other hand, respond to colonization by enteric pathogens with a variety of defence mechanisms, some of which can effectively inhibit biofilm formation. Consequently, plant compounds might be investigated for promising novel antibiofilm strategies.

Effects of hot water and lactic acid treatment of beef trimmings prior to grinding on microbial, instrumental color and sensory properties of ground beef during display

The impact of 82°C hot water (HW) or 5% lactic acid (LA) applied aerobically or by vacuum to beef trimmings prior to grinding on Salmonella Typhimurium (ATCC 1769NR; ST), Escherichia coli (ATCC 11775; EC), coliform (CO), aerobic plate count (APC), instrumental color and sensory characteristics of ground beef through simulated retail display was investigated. For this, beef trimmings were inoculated with a mixture (7 log CFU/ml each) of ST and EC, and treated either aerobically or under vacuum in a tumbler with HW or LA antimicrobials. Trimmings were ground, packaged and sampled on days 0, 1, 2, 3 and 7 of display for ST, EC, CO, APC, sensory and instrumental color characteristics. Vacuum HW or LA application had no additive effect (P>0.05) when compared with aerobic application for reducing EC, ST, CO or APC. However, lactic acid was effective for reducing (P<0.05) EC, CO and APC, but reduced ground beef redness.

Qualitative map of Salmonella contamination on young chicken carcasses

Salmonella contamination of poultry is a global public health problem. The objective of this study was to map the distribution of Salmonella on the young chicken carcass, to improve poultry inspection and food safety. Young chickens (n = 70) in the Cornish game hen class were obtained at retail over a 3-year period. Carcasses were aseptically sectioned into 12 parts, and then Salmonella was isolated from whole-part incubations by conventional culture methods. Isolates were characterized for serotype and antibiotic resistance, and by pulsed-field gel electrophoresis (PFGE). Salmonella incidence was 21.5% (181 of 840) for parts and 57.1% (40 of 70) for carcasses. The number of contaminated parts per carcass ranged from 0 to 12, with a mean of 4.5 among contaminated carcasses. Chi-square analysis indicated that Salmonella incidence differed (P < 0.05) among parts, with rib back (38.6%) and sacral back (34.3%) being the most contaminated. Among the 40 contaminated carcasses, there were 37 different patterns of contamination among parts. Of the 33 carcasses with more than one contaminated part, 12.1% contained two serotypes, 33.3% contained two or more antibiotic resistance profiles, and 100% contained two or more PFGE patterns. The most common serotype was Typhimurium (94.5%), and most (97.2%) isolates were resistant to multiple antibiotics. These results indicated a diverse pattern of Salmonella contamination among carcasses and that multiple subtypes of Salmonella were often present on contaminated carcasses. Thus, whole-carcass incubation succeeded by characterization of multiple isolates per carcass is needed to properly assess and manage this risk to public health.

Relationship between the physicochemical properties of nonchitinolytic Listeria and Salmonella and their attachment to shrimp carapace

Listeria and Salmonella are important foodborne pathogens normally associated with the shrimp production chain. This study investigated the potential of Salmonella Typhimurium, Salmonella Senftenberg, and Listeria monocytogenes (Scott A and V7) to attach to and colonize shrimp carapace. Attachment and colonization of Listeria and Salmonella were demonstrated. Shrimp abdominal carapaces showed higher levels of bacterial attachment (P < 0.05) than did head carapaces. Listeria consistently exhibited greater attachment (P < 0.05) than did Salmonella on all surfaces. Chitinase activity of all strains was tested and found not to occur at the three temperatures (10, 25, and 37 degrees C) tested. The surface physicochemical properties of bacterial cells and shrimp carapace were studied to determine their role in attachment and colonization. Salmonella had significantly (P < 0.05) more positive (-3.9 and -6.0 mV) cell surface charge than Listeria (-18 and -22.8 mV) had. Both bacterial species were found to be hydrophilic (<35%) when measured by the bacterial adherence to hydrocarbon method and by contact angle (theta) measurements (Listeria, 21.3 and 24.8 degrees, and Salmonella, 14.5 and 18.9 degrees). The percentage of cells retained by Phenyl-Sepharose was lower for Salmonella (12.8 to 14.8%) than it was for Listeria (26.5 to 31.4%). The shrimp carapace was found to be hydrophobic (theta = 74.5 degrees), and a significant (P < 0.05) difference in surface roughness between carapace types was noted. There was a linear correlation between bacterial cell surface charge (r2 = 0.95) and hydrophobicity (r2 = 0.85) and initial attachment (P < 0.05) of Listeria and Salmonella to carapaces. However, the same properties could not be related to subsequent colonization.

A survey of microbial contamination of food contact surfaces at broiler slaughter plants in Taiwan

Microbial contamination levels at broiler slaughter plants were investigated at three major slaughter plants in Taiwan during the summer and winter. The microbial contamination levels in chicken carcasses and on food contact surfaces were examined using the swab method. The results indicated that the bacterial counts were affected by the slaughter processing plant, processes, and season (P < 0.05). The bacterial counts on food contact surfaces of the equipment before operation were not significantly lower than those after processing. Regardless of the bacterial type, bacterial counts of chicken carcasses generally decreased from the scalding step to the washing step before evisceration and then increased. The cleaning procedures for food contact surfaces should be evaluated, and special attention should be given to utensils used during processing, such as gloves, baskets, and hand tools.

Binding interaction studies of the immobilized Salmonella typhimurium with extracellular matrix and muscle proteins, and polysaccharides

Our research attempts to understand the real-time interactions of immobilized Salmonella typhimurium with extracellular membrane proteins (collagen I, fibronectin and laminin) and muscle proteins (actin and myosin). Salmonella cells were immobilized on the sensor chip of a surface plasmon resonance (SPR) biosensor. Typical results showed that collagen I and myosin had higher binding responses to the S. typhimurium surface but laminin, actin and fibronectin had lower binding responses. The binding kinetics of collagen I and Salmonella cell surface showed an apparent dissociation and association rate constants of 3.90 E-4 s(-1) and 1.07 E+4 mol(-1) s(-1). Using the model system developed in our laboratory, the interactions of carrageenans and other polysaccharides with collagen and the Salmonella sensor surface were evaluated. The kappa-carrageenans blocked 92-100% binding of collagen to the Salmonella surface, while sodium alginate and low methoxy pectin blocked 50% and 18% binding, respectively. These biosensor studies allowed the rapid evaluation of compounds that may prevent bacterial attachment to poultry skin and carcasses, thus reducing pathogen contamination of poultry foods.

Real-time monitoring of Escherichia coli O157:H7 adherence to beef carcass surface tissues with a bioluminescent reporter

A method for studying bacteria that are attached to carcass surfaces would eliminate the need for exogenous sampling and would facilitate understanding the interaction of potential human food-borne pathogens with food animal tissue surfaces. We describe such a method in which we used a bioluminescent reporter strain of Escherichia coli O157:H7 that was constructed by transformation with plasmid pCGLS1, an expression vector that contains a complete bacterial luciferase (lux) operon. Beef carcass surface tissues were inoculated with the bioluminescent strain, and adherent bacteria were visualized in real time by using a sensitive photon-counting camera to obtain in situ images. The reporter strain was found to luminesce from the tissue surfaces whether it was inoculated as a suspension in buffer or as a suspension in a bovine fecal slurry. With this method, areas of tissues inoculated with the reporter strain could be studied without obtaining, excising, homogenizing, and culturing multiple samples from the tissue surface. Use of the complete lux operon as the bioluminescent reporter eliminated the need to add exogenous substrate. This allowed detection and quantitation of bacterial inocula and rapid evaluation of adherence of a potential human pathogen to tissue surfaces. Following simple water rinses of inoculated carcass tissues, the attachment duration varied with different carcass surface types. On average, the percent retention of bioluminescent signal from the reporter strain was higher on lean fascia-covered tissue (54%) than on adipose fascia-covered tissue (18%) following water washing of the tissues. Bioluminescence and culture-derived viable bacterial counts were highly correlated (r2 = 0.98). Real-time assessment of microbial attachment to this complex menstruum should facilitate evaluation of carcass decontamination procedures and mechanistic studies of microbial contamination of beef carcass tissues.

Rapid physicochemical detachment, separation and concentration of bacteria from beef surfaces

A simple, rapid, physicochemical treatment for the removal of viable bacteria from the surface of raw and cooked beef is described. The detachment method was linked to a differential centrifugation step which removed large amounts of particulate food matter and concentrated the detached bacteria. The method increased the numbers of bacteria released from beef surfaces and increased the numbers detected by at least one and a half orders of magnitude, when compared to the traditional 'stomaching' technique. This 1-h separation and concentration method produced cleaner suspensions of bacteria and improved the sensitivity of detection by DEFT and direct plate count.

A model study of factors involved in adhesion of Pseudomonas fluorescens to meat

A study was undertaken to investigate the factors involved in the adhesion of Pseudomonas fluorescens to model meat surfaces (tendon slices). Adhesion was fast (less than 2.5 min) and was not suppressed by killing the cells with UV, gamma rays, or heat, indicating that physiological activity was not required. In various salt solutions (NaCl, KCl, CaCl2, MgCl2), adhesion increased with increasing ionic strength up to 10 to 100 mM, suggesting that, at low ionic strengths, electrostatic interactions were involved in the adhesion process. At higher ionic strengths (greater than 10 to 100 mM) or in the presence of Al3+ ions, adhesion was sharply reduced. Selectively blocking of carboxyl or amino groups at the cell surface by chemical means did not affect adhesion. These groups are therefore not directly involved in an adhesive bond with tendon. Given a sufficient cell concentration (10(10) CFU.ml-1) in the adhesion medium, the surface of tendon was almost entirely covered with adherent bacteria. This suggests that if the adhesion is specific, the attachment sites on the tendon surface must be located within collagen or proteoglycan molecules.

Role of flagella in adhesion of Pseudomonas fluorescens to tendon slices

Tendon slices were used as model surfaces to investigate the role of flagella in the adhesion of Pseudomonas fluorescens to meat. The slices were introduced into a specially designed flow chamber, which was then filled with a suspension of the organism, and the tendon surface was observed at a x640 magnification. The same events that occur during the colonization of glass surfaces (apical adhesion of cells with rotation around the contact point, longitudinal adhesion, detachment of apically and longitudinally adherent cells) were also observed on tendon. Mechanical removal of the flagella resulted in no change in the contact angles with 0.1 M saline or alpha-bromonaphthalene, in the electrophoretic mobility, or in the adhesion of the organism to hydrophobic and ion-exchange resins. In addition, cells from which flagella had been mechanically removed still adhered extensively to tendon. Nevertheless, under comparable conditions (bacterial concentration, contact time), flagellated cells adhered to tendon in larger numbers than did deflagellated cells. This was entirely due to the ability of the motile flagellated cells to reach tendon in greater numbers than deflagellated cells.

New method to study bacterial adhesion to meat

A new method was developed for the study of bacterial adhesion to meat surfaces. Thin slices of meat (40 microns thick) were inserted into a specially designed observation chamber. The meat slices were then exposed to a bacterial suspension (ca. 10(6) CFU.ml-1) to initiate adhesion (20 min of contact time) and subsequently rinsed to eliminate nonadherent bacteria. Because of the special chamber design, the disruptive force exerted on the bacteria during rinsing (shear stress) was uniform over the whole surface of the meat slices, was constant, and could be varied from 0 to 0.08 N.m-2. After being rinsed, the meat slices were stained with basic fuschin and observed under light microscopy to determine the number and distribution of adherent bacteria. This new method was used to study the adhesion of Acinetobacter strain LD2, a Lactobacillus sp., and Pseudomonas fluorescens to slices of beef fat and tendon. At 25 degrees C, most (greater than or equal to 99.9%) of the cells of the Lactobacillus sp. deposited on the meat were washed off the surface during rinsing (0.05 N.m-2), whereas a large number (ca. 10(5) CFU.cm-2) of Acinetobacter strain LD2 and P. fluorescens cells remained adherent. The extent of adhesion was similar on fat and tendon, and adherent bacteria were distributed evenly over the whole surface of the slices. This preliminary study indicates that the combined use of thin slices of meat and of the observation chamber provides us with the means to more accurately study bacterial adhesion to meat surfaces.

Cell surface charge characteristics and their relationship to bacterial attachment to meat surfaces

Cell surface charge and hydrophobicity of Bacillus subtilis, Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, Serratia marcescens, Staphylococcus aureus, and Staphylococcus epidermidis were determined by hydrocarbon adherence, hydrophobic interaction, and electrostatic interaction chromatography. Surface charge and hydrophobicity were compared with the initial attachment values and rates of attachment of the bacteria to meat surfaces. There was a linear correlation between the relative negative charge on the bacterial cell surface and initial attachment to lean beef muscle (r2 = 0.885) and fat tissue (r2 = 0.777). Hydrophobicity correlated well with attachment to fat tissue only. The relative hydrophobicity of each bacterium was dependent on the specific method of determination, with wide variations noted between methods.

Adhesion of Staphylococcus aureus to fibrinogen, collagen and lectin in relation to cell surface structure

The adherence of an encapsulated strain of Staphylococcus aureus, S-P, and its variants to fibrinogen-, collagen-, and lectin-coated hydroxyapatite were compared. The parent strain, S-P, possesses a large capsule while its variants S-A and S-B possess a small capsule and microcapsule, respectively. The third variant, S-C, has no capsule. Adherence to proteinaceous substances varied according to the strains. While all four strains showed a similar degree of adhesion to collagen, the adhesion of strains S-A, S-B and S-C to fibrinogen and lectin differed from those of strain S-P. The effect of physical and enzymatic pretreatment of the strains on adhesion characteristics was measured. Generally, these results suggest that both carbohydrate and protein moieties on cell surface may be involved in adherence. In addition, the inhibition of adhesion by cell-surface polymers and monosaccharides was measured. The inhibition of adhesion of large capsulated (S-P) and unencapsulated (S-C) strains by proteinaceous substances differed. The large capsulated strain (S-P) of S. aureus had different adherence capacities in early-, mid-, or late log phases of growth, whereas the adherence capacities of the unencapsulated strain S-C remained nearly constant.

A note on adhesion of bacteria to chicken muscle connective tissue

Laboratory cultures of bacteria were tested for the ability to attach to collagen fibres of intact chicken muscle connective tissue. All salmonellas, fimbriate strains of Escherichia coli and a strain of Campylobacter coli were able to attach to tissue only when suspended in distilled water. Prior immersion of tissue in sterile water for 20 min or extended immersion in these bacterial suspensions was a prerequisite for adhesion. Attachment could be prevented by the addition of physiological levels of sodium chloride to the attachment medium. Furthermore, attached bacteria could be removed by rinsing tissues in saline media.

Contamination and bacterial retention capacity of beef carcasses at the abattoir

The contamination of beef carcasses was studied together with the capacity of meat surfaces to retain bacteria along the processing line in the slaughter hall. The results showed that the contamination varied along the processing line, but that this pattern was essentially dependent on the contamination at the dressing station. It decreased or remained unchanged during the first 12 min and then increased, even without additional contamination. The contamination varied according to carcasses and micro-organisms studied and was not greatly affected by spray cleaning. The number of bacteria retained changed at a rate similar to that of the contaminants. The attachment was instantaneous. The results are discussed and compared with the various hypotheses about contamination and bacterial attachment processes.