Baird-Parker Research Articles

Streptavidin-exposed magnetic nanoparticles for lectin magnetic separation (LMS) of Staphylococcus aureus prior to three quantification strategies.

A lectin magnetic separation (LMS) method for Staphylococcus aureus (S. aureus) was developed with the aim to improve the efficiency of magnetic nanoparticles and to expand the scope of bacterial recognition. Poly(ethylene glycol) (PEG)-mediated magnetic nanoparticles modified with streptavidin (MNP-PEG-SA) were synthesized and then applied to a two-step LMS based on the use of wheat germ agglutinin (WGA). Three specific methods for S. aureus detection (suitable for different requirements including detection time and sensitivity) were designed. The new LMS has improved anchoring efficiency (compared to two-step LMS methods) and requires a reduced number of magnetic particles. The Baird-Parker (B-P) method can detect S. aureus with a detection limit of 3 × 100CFU·mL-1 within 15h; the polymerase chain reaction (PCR) method can be finished within 4h, with the lowest detection limit (LOD) of 3 × 102CFU·mL-1. The LOD of HRP-pig IgG-based colorimetric method is 3 × 105CFU·mL-1, and the method only lasts for 2h. If combined with specific detection methods, it meets different needs for rapid detection of S. aureus. Graphical abstractSchematic representation of lectin magnetic separation (LMS) based on biotin-wheat germ agglutinin (WGA) and poly (ethylene glycol) (PEG)-mediated streptavidin-modified magnetic nanoparticles (MNP-PEG-SA) and three different quantification strategies (including B-P culture assay, PCR assay, and colorimetric assay) for S. aureus.

Investigation of Antibacterial Properties of Ag Doped TiO2 Nanofibers Prepared by Electrospinning Process

Abstract In this study, undoped and 1, 2,3, 4, and 5 wt % Ag-doped TiO2 nanofibers have been fabricated by the electrospinning method applying 20 kV voltages at 8 cm height with a flow rate 0.1 mL/h. The antibacterial properties of undoped and doped Ag/TiO2 nanofibers were tested on Staphylococcus aureus bacteria. The antibacterial effect of these fabricated nanofibers has been determined by disc diffusion and Baird parker methods. The results have shown that Ag/TiO2 nanofibers have an excellent antibacterial effect on this bacterium compared to pure TiO2 nanofibers. As a result, developed nanofibers can easily be applied in various fields such as biomedical sector and tissue engineering. In addition, the chemical components, morphology, and crystal structure of the nanofibers have been performed by scanning electron microscopy energy dispersive analysis (SEM-EDX), differential thermal analysis/thermal gravimetric analysis (DTA/TG), and X-ray diffraction (XRD) methods.

Prevalence of antibiotic resistant Staphylococcus aureus from raw milk samples collected from the local vendors in the region of Tirupathi, India.

Aim:The study was carried out with the aim to identify the suitability of the milk for consumer use with special reference to Staphylococcus aureus from milk samples collected from various local vendors and determine the antibiotic susceptibility pattern of those positive isolates.Materials and Methods:A total of 110 milk samples were collected from the local milk vendors in and around Tirupathi region of India. All the samples were enriched with buffered peptone water in 9:1 ratio and the then inoculated on baird parker agar medium with added 2% egg yolk tellurite emulsion as selective medium for S. aureus and confirmed with mannitol salt agar, Gram’s staining and biochemical tests. The typical cultural characters with coagulase-positive samples were taken as positive samples the positive samples were tested for antibiotic susceptibility with 10 different antibiotics by employing disc diffusion method.Results:Prevalence of coagulase-positive S. aureus was 39.09% (43/110) from the milk samples. The antibiotic susceptibility test of positive isolates showed high resistant toward penicillin G 37/43 (86.04%) and ampicillin 32/43 (74.42%), and also showed resistant to methicillin 6/43 (13.95%), cephalothin 6/43 (13.95%), tetracycline 6/43 (13.95%), ciprofloxacin 4/43 (9.30%), enrofloxacin 3/43 (6.97%), cefoxitin 2/43 (4.65%), gentamicin 2/43 (4.65%), and co-trimoxazole 2/43 (4.65%). Many individual isolates showed resistant against two or more antibiotics in our study.Conclusion:The above study results show that the milk samples collected from local vendor having S. aureus, which can induce disease condition as well as antibiotic resistant to the humans particularly young children and old age peoples by means of consumption of raw milk and its products. This is the public health issue, which needs to be solved by educating the local vendors regarding health problems related to unhygienic milk supply and make the awareness among the consumers about this hazards and preventive measures.

Enumeration Methods and Production of Enterotoxins in Food-Derived Staphylococcus aureus

Staphylococcal food poisoning is one of the most common foodborne diseases worldwide; it results from the ingestion of staphylococcal enterotoxins (SEs) in food, mainly Staphylococcus aureus. This study investigated the statistical relationships among morphological enumerations of food-derived S. aureus and production of SEs using different methodologies. Food samples naturally contaminated with coagulase-positive S. aureus were submitted for enumeration on Baird-Parker (BP) agar, Rabbit Plasma Fibrinogen agar (RPFA), and Petrifilm Staph Express count system (STX), and the morphologically typical colonies were isolated for VIDAS and real-time (RT) PCR tests. RPFA and STX displayed better performance for the enumeration of SE-positive S. aureus when compared with BP, including higher frequencies of SE-positive isolates and better correlation indices between typical and SE-positive counts. Among all the evaluated culture media, no significant difference (P > 0.05) was shown on the frequencies of typical colonies that carried 11 individual se genes. In addition, results for SE identification between VIDAS and RT-PCR assay were unparalleled. These data will be valuable for the selection of methods for inspection of food-derived S. aureus.

Performance comparison of 5 selective media used to detect Staphylococcus aureus in foods

Performance comparison tests were carried out on Staphylococcus aureus selective media recommended by food safety agencies or approved by international standardization bodies. The performance of mannitol salt agar (MSA), Baird parker agar, Vogel johnson agar, RAPID’ Staph, and CHROMagar staph aureus are compared. Four out of the 5 media showed 100% sensitivity, with MSA showing 96.5%. MSA also showed only 66.6% specificity, while 4 out of 5 media showed 100% specificity. In recovery tests S. aureus was more easily recovered from instant cooked rice than fish fillet. The tested media did not have a significant difference on recovery activity.

Notes on the almost unknown genusJeotgalicoccus

To facilitate isolation and differentiation of the almost entirely unknown Jeotgalicoccus spp. Jeotgalicoccus spp. have been found in dust samples using SSCP-PCR analysis. As the cultivation of strains is necessary for further studies on virulence, pathogenicity or metabolism, we developed a method for cultural isolation and further differentiation of Jeotgalicoccus spp. We found that J. halotolerans, J. psychrophilus, J. marinus, as well as the related species Salinicoccus roseus grow on Baird Parker (BP) agar as black colonies without clear zones. J. pinnipedialis and S. jeotgali grow only weakly on BP agar without forming clearly delineated colonies. On BP agar, the colony-forming Jeotgalicoccus and Salinicoccus spp. are not distinguishable from coagulase-negative Staphylococcus spp. (CNS). However, unlike CNS, all of the above mentioned species are unreactive in the OF test. SSCP-PCR was able to differentiate between all investigated Jeotgalicoccus and Salinicoccus spp., as all species had different band positions. Jeotgalicoccus spp. and Salinicoccus spp. may be widely distributed in the environment, but, until now, overlooked or confused with staphylococci. Further epidemiological studies, which are required to prove this hypothesis, are facilitated by the observations of our study. This not yet published information enables researchers to carry out epidemiological studies on Jeotgalicoccus spp. in a very cheap and easy way.

Temperature-assisted high hydrostatic pressure inactivation of Staphylococcus aureus in a ham model system: evaluation in selective and nonselective medium

The purpose of this study was to investigate the inactivation kinetics of Staphylococcus aureus in a ham model system by high hydrostatic pressure at ambient (25 degrees C) and selected temperatures (45, 55 degrees C). Selective [Baird Parker (BP) agar] and nonselective [brain heart infusion (BHI) agar] growth media were used for enumeration in order to count viable and sublethally injured cells. The micro-organism was exposed to a range of pressures (450, 500, 550, 600 MPa) at ambient temperature (25 degrees C) for up to 45 min. Additionally, the behaviour of the micro-organism was evaluated at mild temperatures in combination with high pressure treatment, namely: (i) 350, 400 and 450 MPa at 45 degrees C; and (ii) 350 and 400 MPa at 55 degrees C, for up to 12 min. Inactivation kinetics were calculated in terms of D(p) and z(p) values. Survival curves of S. aureus at ambient temperature were mostly linear, whereas when temperature was applied, tailing was observed in most survival curves. The estimated D(p) values and therefore the number of surviving cells, were substantially higher on the selective BP agar in the whole range of pressures applied, indicating that S. aureus showed greater recovery in the selective BP agar than the nonselective BHI agar. Samples pressurized at ambient temperature needed higher pressures (over 500 MPa) to achieve a reduction of the population of the pathogen more than 5 log CFU ml(-1). The same level of inactivation was achieved at lower pressure levels when mild heating was simultaneously applied. Indeed, more than 6 log CFU ml(-1) reductions were obtained at 400 MPa and 55 degrees C within the first 7 min of the process in BHI medium. Elevated temperatures allowed lower pressure levels and shorter processing times of pathogen inactivation than at room temperature. Greater recovery of the pathogen was observed in the selective (BP agar) medium, regardless of pressure and temperature applied. The obtained kinetics could be employed by the industry in selecting optimum pressure/temperature processing conditions. Attention must be given to the selection of the enumeration medium, as the use of an inappropriate medium would lead to underestimation of the surviving cells, thus imposing a risk in the microbiological safety of the product.

Validation of EN ISO standard methods 6888 Part 1 and Part 2: 1999—Enumeration of coagulase-positive staphylococci in foods

The methods of European and International Organisations for Standardization for the enumeration of coagulase-positive staphylococci (CPS, Staphylococcus aureus and other species) described in EN ISO 6888 Part 1 and Part 2: 1999 were validated by order of the European Commission (Standards, Measurement and Testing Fourth Framework Programme Project SMT4-CT96-2098). EN ISO 6888-1 prescribes the use of Baird–Parker (BP) agar whereas EN ISO 6888-2 prescribes the use of Rabbit Plasma Fibrinogen Agar (RPFA). The objective was to determine the precision of each method in terms of repeatability ( r) and reproducibility ( R) using three different food types inoculated with various levels of S. aureus and a typical background flora. The results are intended for publication in the associated standards. Cheese, meat and dried egg powder were examined by 24 laboratories from 16 countries in Europe. Each participant received eight test materials per food type: blind duplicates at four inoculum levels (0, 10 3, 10 4 to 10 5, 10 5 to 10 6 cfu/g). In addition, two reference materials (RM) (capsules containing milk powder inoculated with S. aureus) were included in the study. All test materials were subjected to stringent homogeneity and stability testing before being used in the collaborative trial. Two statistical methods were used to calculate the precision parameters. Draft EN ISO 16140: 2000 method appeared more appropriate to the case of microbiological data than ISO 5725-2: 1994 method and was retained to calculate the precision data. Concerning EN ISO 6888-1, overall values for repeatability ( r) when used with food test materials was r=log 10 0.28 (expressed as an absolute difference between log 10-transformed test results). For the reference materials, r=log 10 0.19. Overall values for reproducibility ( R) when used with food test materials were R=log 10 0.43. For the reference materials, R=log 10 0.39. Concerning EN ISO 6888-2, overall values for repeatability ( r) when used with food test materials were r=log 10 0.22. For the reference materials, r=log 10 0.17. Overall values for reproducibility ( R) when used with food test materials were R=log 10 0.33. For the reference materials, R=log 10 0.31. These results were presented to the ISO technical committee and to the Comité Européen de Normalisation (CEN). Both committees agreed to incorporate the precision data obtained with food materials as two amendments to EN ISO 6888-1 and -2, and to give an equal status to each part of the standard.

Comparison of Recovery of Airborne Microorganisms in a Dairy Cattle Facility Using Selective Agar and Thin Agar Layer Resuscitation Media

Thin agar layer (TAL) medium was developed at Kansas State University to improve the resuscitation of injured cells and has been shown to result in higher recovery than is obtained with selective media alone for cold-, heat-, salt-, and acid-injured cells. The experiment presented here was designed to determine the effectiveness of the TAL method for the recovery of possibly injured organisms from air. Eleven agar media were used for the experiment: tryptic soy agar (TSA), MacConkey sorbitol agar (MSA), TAL-MSA, Baird-Parker (BP) agar, TAL-BP agar, modified Oxford (MOX) agar, TAL-MOX agar, xylose lysine sodium desoxycholate (XLD) agar, TAL-XLD agar, Yersinia-selective (CIN) agar, and TAL-CIN agar. The TAL plates were prepared by pipetting 6 ml of selective agar into a BBL Rodac plate (65 by 15 mm). Selective agar was allowed to solidify, and then each plate was overlaid with 6 ml of TSA. Selective agar plates were prepared by pipetting 12 ml of agar into BBL Rodac plates and allowing the agar to solidify. Samples were taken at an indoor cattle facility at five separate locations with a BioScience SAS air-sampling instrument. For each plate, 60 liters of air was sampled. Three replications of the experiment were performed. The TAL method resulted in higher counts of microorganisms on all media tested. In addition, 175 isolates were selected randomly and identified in order to test the selectivity of TAL and the selective media for target organisms. The data obtained in this study show that the TAL resuscitation method is effective and necessary for the recovery of airborne organisms that may be injured.

Comparison of selective culture media to enumerate coagulase-positive staphylococci in cheeses made from raw milk

Baird-Parker (BP) medium is the selective medium most commonly used to enumerate coagulase-positive staphylococci in food. However, it seems often not sufficiently selective for the analysis of raw foodstuffs which present a high level of concomitant flora. An alternative medium, rabbit plasma fibrinogen agar (RPFA) medium, is now available but has not yet been tested extensively with cheeses made from raw milk. Therefore, a comparison of both media was carried out with 77 samples from four types of raw-milk cheeses. Two brands of RPFA medium were compared with one brand of BP medium. This last medium was tested after two different shelf lives at +4°C, 1 day and 4 months, to evaluate the possible influence of the storage delay on its stability. Enumeration results from 20 (26%) of the 77 samples could not be used for statistical analysis because of reading problems observed on one or several of the media. These problems, due to a high level of concomitant flora, were more frequently observed using BP medium (18 samples) than using RPFA media (two to three samples). Enumeration means obtained for the 57 (74%) samples retained for statistical purposes were not significantly different between the two types of medium. This study shows that BP medium can be used after a storage delay at +4°C of 4 months as ready-to-use commercialized medium. However, as RPFA media are much easier and faster to read than BP medium, and as they give similar or even more precise enumeration results than BP medium, the use of RPFA media is recommended to enumerate coagulase-positive staphylococci in cheeses made from raw milk.

Contaminação microbiana em carne moída de açougues da cidade de Santa Maria, RS, Brasil

Foram coletadas aleatoriamente, 10 amostras de carne moída bovina em açougues da cidade de Santa Maria, RS, para determinar a presença de microorganismos totais, coliformes e Staphylococcus aureus. Respectivamente, usou-se os meios ágar para contagem total (PCA), ágar cristal violeta vermelho neutro bile e ágar bairdparker. Na contagem de microorganismos totais, 60% das amostras apresentaram entre 1,7 a 8,8 x 10(4) uFC/g de carne moída. Para Coliformes, 20% das amostras apresentaram um número menor que 1,0 x 10² uFc/g, 40% entre 1,0 a 3,2 x 10³ uFC/g, 30% entre 3,7 a 9,6 x 10(4) uFC/g e em 10% houve acidente laboratorial. Para Staphylococcus aureus, 100% das amostras resultaram positivas, sendo 50% entre 1,0 a 4,0 x 10³ uFC/g, 40% entre 1,3 a 2,8 x 10(4) e 10% entre 1,5 a 4,0 x 10(5) uFC/g de carne moída.

Performance of Four Selective Media for Enumerating Staphylococcus aureus in Corned Beef and in Cheese

The performance of four selective media for enumerating Staphylococcus aureus in artificially contaminated samples of corned beef was strain-dependent. Baird-Parker (BP), Kranep (KR), Mannitol Salt (MS) and Staphylococcus medium 110 (S110) performed equally well in enumerating an enterotoxin A producing strain, but KR and BP were significantly better than S110 in enumerating an enterotoxin D producing strain of S. aureus. In naturally contaminated cheese samples which abound with competing microorganisms, BP performed significantly better than the other three media.

Status of membrane-filter procedure in the examination of water and milk for Staphylococcus aureus

A comparative study was carried out to assess the performance of four selective media, namely Baird-Parker (B-P), Mannitol-Salt Agar (M.S.A.), Staphylococcus-110 (S-110), and Chapman-Stone (C.S) in solid and liquid forms for recovery of Staphylococcus aureus from water and milk, using membrane filter technique. The descending order of efficiency for demonstrating the presence of inoculated S. aureus from unsterilized Nile water was (B-P)--(M.S.A) + (S-110) and (C.S) medium in solid form and changed to (S-110)--(M.S.A)--(C.S) when used in the liquid form. With sterile Nile water, the descending order of efficiency of the tested media was (B-P) + (M.S.A)--(S-110) and (C.S) medium in the solid form and (M.S.A) + (S-110) and (C.S) in the liquid form. In testing the inoculated milk using solid media, (S-110) and (M.S.A) tend to show similar results and took intermediate position between (B-P) and (C.S). When liquid media were used, the descending order of productivity was (S-110)--(M.S.A) and (C.S).

Status of membrane-filter procedure for examination of water and milk forStaphylococcus aureus

Baird-Parker (BP) agar was found to be more efficient forStaphylococcus aureus recovery from water and milk. The other media efficacy could be represented in that descending order: Mannitol Salt (MS)-Staphylococcus 110 (S 110) and Chapman Stone (CS) agars. (BP) was not recommended to be use in liquid form with absorbent pads, while (S-110) and (MS) tend to be superior to (CS).

Use of Baird-Parker's Medium to Enumerate Staphylococcus aureus in Meats

The Staphylococcus aureus count was determined, using Baird-Parker (BP) medium and coagulase reaction, on 100 samples of ground beef, 23 frozen pork sausage samples and 140 retail meat cuts (beef and pork). S. aureus counts on ground beef ranged from < 100 to 4,500 per g, and 16% had counts of 1,000 per g or greater. Frozen pork sausage samples had similar S. aureus counts to ground beef. Retail meat cuts generally had counts less than 100 per cm2. Typical S. aureus colonies in this study on BP medium were dark grey to grey-black, and not shiny black as generally described. Type II colonies (without egg yolk clearing) did not contribute markedly to the total S. aureus count and egg yolk clearing type I colony count is suggested for routine estimation of the S. aureus count. The S. aureus isolates in this study generally had 3+ coagulase reactions. The coagulase-positive isolates were generally phosphatase-positive (96.8%), Voges-Proskauer test-positive (97.4%), DNase-positive (98.7%) and used glucose and mannitol oxidatively and fermentatively (93.5%). Most non-S. aureus colonies were “other” staphylococci or micrococci. These isolates had variable phosphatase, Voges-Proskauer and DNase reactions, generally with at least one of these three tests negative.

Comparative Efficiency of Two Methods and Two Plating Media for Isolation of Staphylococcus aureus from Foods

Abstract Modifications of 2 methods were compared for determination of staphylococci in foods as recommended by the International Committee on Microbiological Specifications for Foods. One method was a direct plating procedure using Baird-Parker (BP) medium. The second method was the current AOAC official first action method for isolation of Staphylococcus aureus from foods (41.018). The efficiency of Vogel and Johnson (VJ) agar and BP as plating media for the AOAC method was also compared. The presence of S. aureus (positive samples) was detected more often by the AOAC method than by the direct plating method. The use of BP as a plating medium in the AOAC method resulted in detection of 25% more positive samples than were detected with VJ agar.