Modeling the Aerobic Growth and Decline of Staphylococcus aureus as Affected by pH and Potassium Sorbate Concentration

1999 ◽  
Vol 62 (4) ◽  
pp. 356-362 ◽  
Author(s):  
LEDA GIANNUZZI ◽  
EDGARDO CONTRERAS ◽  
NOEMI ZARITZKY
Keyword(s):  
Staphylococcus Aureus ◽  
Incubation Temperature ◽  
Growth Parameters ◽  
Brain Heart Infusion ◽  
Gompertz Model ◽  
Potassium Sorbate ◽  
Aerobic Growth ◽  
Treatment Conditions ◽  
Effects Of Ph ◽  
Sorbate Concentration

The effects of pH (5.0, 5.2, 5.4, 5.6, and 5,8) and concentration of potassium sorbate (10.0 and 16.6 mM) at two water activity values (0.90 and 0.92) on the aerobic growth and decline of Staphylococcus aureus ATCC 6538P, 196-E, and FDA-C243 were studied using brain-heart infusion broth. The inoculum was approximately 4 to 5 log CFU/ml, and the incubation temperature was 30°C. Samples were periodically enumerated on tryptic soy agar. The Gompertz model was used to obtain microbial growth parameters, specific growth rate was obtained as a derived parameter, and the inhibition index was calculated. A linear model was fitted in cases of bacteriostatic or bactericidal action of the treatment. The ATCC 6538P strain showed the highest resistance in the range of tested conditions. Microbial behavior was modeled considering the main controlling factors, and a response surface methodology was used to determine the effects of undissociated acid concentration and pH. These results can be used to establish treatment conditions for microorganism growth or inhibition.

Modeling the Growth Boundary of Staphylococcus aureus for Risk Assessment Purposes

2001 ◽  
Vol 64 (1) ◽  
pp. 51-57 ◽  
Author(s):  
CYNTHIA M. STEWART ◽  
MARTIN B. COLE ◽  
J. DAVID LEGAN ◽  
LOUISE SLADE ◽  
MARK H. VANDEVEN ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Staphylococcus Aureus ◽  
Brain Heart Infusion ◽  
Toxin Production ◽  
Potassium Sorbate ◽  
Growth Responses ◽  
Microtiter Plates ◽  
Initial Ph ◽  
Data Points ◽  
Boundary Model

Knowing the precise boundary for growth of Staphylococcus aureus is critical for food safety risk assessment, especially in the formulation of safe, shelf-stable foods with intermediate relative humidity (RH) values. To date, most studies and resulting models have led to the presumption that S. aureus is osmotolerant. However, most studies and resulting models have focused on growth kinetics using NaCl as the humectant. In this study, glycerol was used to investigate the effects of a glass-forming nonionic humectant to avoid specific metabolic aspects of membrane ion transport. The experiments were designed to produce a growth boundary model as a tool for risk assessment. The statistical effects and interactions of RH (84 to 95% adjusted by glycerol), initial pH (4.5 to 7.0 adjusted by HCl), and potassium sorbate (0, 500, or 1,000 ppm) or calcium propionate (0, 500, or 1,000 ppm) on the aerobic growth of a five-strain S. aureus cocktail in brain heart infusion broth were explored. Inoculated broths were distributed into microtiter plates and incubated at 37°C over appropriate saturated salt slurries to maintain RH. Growth was monitored by turbidity during a 24-week period. Toxin production was explored by enterotoxin assay. The 1,280 generated data points were analyzed by SAS LIFEREG procedures, which showed all studied parameters significantly affected the growth responses of S. aureus with interactions between RH and pH. The resulting growth/no growth boundary is presented.

scholarly journals The effect of temperature and water activity on the growth of Staphylococcus aureus

2010 ◽  
Vol 27 (Special Issue 2) ◽  
pp. 28-35 ◽  
Author(s):  
A. Medveďová ◽  
Ľ. Valík ◽  
A. Studeničová
Keyword(s):  
Staphylococcus Aureus ◽  
Growth Rate ◽  
Sodium Chloride ◽  
Water Activity ◽  
Specific Growth ◽  
Incubation Temperature ◽  
Growth Parameters ◽  
Effect Of Temperature ◽  
Extended Model ◽  
Growth Responses

The growth responses of Staphylococcus aureus 2064 as affected by water activity and incubation temperature were studied in two different laboratory media. Growth parameters at temperatures from 7 to 51&deg;C and a<sub>w</sub> in the range from 1.0 to 0.86 were fitted using Ratkowsky models. The effect of temperature within its whole range on the specific growth rate was modelled by the extended model under the following equation: &radic;&micro; = 0.0456 (T &ndash; T<sub>min</sub>) [1 &ndash; e<sup>0.447(T &ndash; T<sub>max</sub>)</sup>]. The water activity values of tested media were adjusted by sodium chloride in the range from a<sub>w</sub> = 1.0 to 0.86 and experiments were conducted at 15 and 18&deg;C. The growth responses of S. aureus on water activity at 15&deg;C and 18&deg;C in PCA broth and BHI broth was described by simplified Ratkowsky model in the form: &radic;&micro; = b &times; a<sub>w</sub>. Validation of the found relationships confirmed sound fitting of the data and thus the referred results of the isolate originated from ewes&rsquo; cheese can be used in the growth prediction of S. aureus, reliably.

Staphylococcus aureus Growth and Enterotoxin A Production in an Anaerobic Environment

2002 ◽  
Vol 65 (1) ◽  
pp. 199-204 ◽  
Author(s):  
NEGASH BELAY ◽  
AVRAHAM RASOOLY
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Density ◽  
Incubation Temperature ◽  
Food Poisoning ◽  
Brain Heart Infusion ◽  
Toxin Production ◽  
Anaerobic Growth ◽  
Anaerobic Conditions ◽  
Effects Of Temperature ◽  
Anaerobic Environment

The effects of strict anaerobic conditions on the growth of Staphylococcus aureus and the production of staphylococcal enterotoxin A (SEA) were studied. The growth of S. aureus, a facultative anaerobic bacterium, is slower anaerobically than aerobically. When grown on brain heart infusion broth at 37°C, the anaerobic generation time at mid-log phase was 80 min, compared with 35 min for the aerobic control. In contrast to previous studies demonstrating that staphylococcal cell density was 9- to 17-fold greater in aerobic than in anaerobic cultures, data for a staphylococcal strain implicated in food poisoning showed that the cell density was only two to three times as great in aerobic cultures. Production of SEA was monitored by Western immunoblotting and shown to be growth dependent. With slower anaerobic growth, relatively less toxin was produced than under aerobic conditions, but in both cases SEA was detected after 120 min of incubation. The combined effects of temperature and aeration on S. aureus were also studied. Growth and toxin production of aerobic and anaerobic cultures at temperatures ranging from 14 to 37°C were analyzed. Growth was still observed at low temperatures in both environments. A linear model for S. aureus aerobic or anaerobic growth as a function of incubation temperature was developed from these studies. The model was tested from 17 to 35.5°C, and the results suggest that the model can accurately predict the S. aureus growth rate in this temperature range. The data suggest that anaerobic conditions are not an effective barrier against S. aureus growth.

scholarly journals Screening for Intermediately Vancomycin-Susceptible and Vancomycin-Heteroresistant Staphylococcus aureus by Use of Vancomycin-Supplemented Brain Heart Infusion Agar Biplates: Defining Growth Interpretation Criteria Based on Gold Standard Confirmation

2015 ◽  
Vol 53 (11) ◽  
pp. 3543-3546 ◽  
Author(s):  
Riad Khatib ◽  
Kathleen Riederer ◽  
Mamta Sharma ◽  
Stephen Shemes ◽  
Sugantha P. Iyer ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Gold Standard ◽  
Population Analysis ◽  
Area Under The Curve ◽  
Brain Heart Infusion ◽  
Roc Curves ◽  
Clinical Samples ◽  
Content Type ◽  
Interpretation Criteria ◽  
Profile Area

BHI agars supplemented with vancomycin 4 (BHI-V4) and 3 (BHI-V3) mg/liter have been proposed for screening vancomycin intermediately susceptibleStaphylococcus aureus(VISA) and heteroresistant (hVISA) phenotypes, respectively, but growth interpretation criteria have not been established. We reviewed the growth results (CFU) during population analysis profile-area under the curve (PAP-AUC) of consecutive methicillin-resistantStaphylococcus aureus(MRSA) blood isolates, which were saved intermittently between 1996 and 2012. CFU counts on BHI-V4 and BHI-V3 plates were stratified according to PAP-AUC interpretive criteria: <0.90 (susceptible [S-MRSA]), 0.90 to 1.3 (hVISA), and >1.3 (VISA). CFU cutoffs that best predict VISA and hVISA were determined with the use of receiver operating characteristic (ROC) curves. Mu3, Mu50, and methicillin-susceptibleS. aureus(MSSA) controls were included. We also prospectively evaluated manufacturer-made BHI-V3/BHI-V4 biplates for screening of 2010-2012 isolates. The PAP-AUC of 616 clinical samples was consistent with S-MRSA, hVISA, and VISA in 550 (89.3%), 48 (7.8%), and 18 (2.9%) instances, respectively. For VISA screening on BHI-V4, a cutoff of 2 CFU/droplet provided 100% sensitivity and 97.7% specificity. To distinguish VISA from hVISA, a cutoff of 16 CFU provided 83.3% sensitivity and 94.7% specificity; the specificity was lowered to 89.5% with a 12-CFU cutoff. For detecting hVISA/VISA on BHI-V3, a 2-CFU/droplet cutoff provided 98.5% sensitivity and 93.8% specificity. These results suggest that 2-CFU/droplet cutoffs on BHI-V4 and BHI-V3 best approximate VISA and hVISA gold standard confirmation, respectively, with minimal overlap in samples with borderline PAP-AUC. Simultaneous screening for VISA/hVISA on manufacturer-made BHI-V4/BHI-V3 biplates is easy to standardize and may reduce the requirement for PAP-AUC confirmation.

scholarly journals Antimicrobial Effect of Plasma-Activated Tap Water on Staphylococcus aureus, Escherichia coli, and Candida albicans

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1480
Author(s):  
William Chiappim ◽  
Aline da Graça Sampaio ◽  
Felipe Miranda ◽  
Mariana Fraga ◽  
Gilberto Petraconi ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Antimicrobial Activity ◽  
Candida Albicans ◽  
Tap Water ◽  
Antimicrobial Effect ◽  
Gliding Arc ◽  
Oxidation Reduction ◽  
Treatment Conditions ◽  
Oxidation Reduction Potential

In this study, the potential antimicrobial activity of plasma-activated tap water (PAW) was evaluated against Staphylococcus aureus, Escherichia coli, and Candida albicans. For this, PAW was prepared in a gliding arc plasma system using two treatment conditions: stagnant water and water stirring by a magnetic stirrer, called moving water. Subsequently, their oxidation-reduction potential (ORP), pH, electrical conductivity (σ), and total dissolved solids (TDS) were monitored in different areas of the sample divided according to the depth of the beaker. It was observed that PAW obtained in dynamic conditions showed a more uniform acidity among the evaluated areas with pH 3.53 and ORP of 215 mV. Finally, standardized suspensions of Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 10799), and Candida albicans (SC 5314) were treated with PAW, and the reduction of viable cells determined the antimicrobial effect. Our results indicate that the tap water, activated by plasma treatment using gliding arc, is an excellent inactivation agent in the case of Staphylococcus aureus and Escherichia coli. On the other hand, no significant antimicrobial activity was achieved for Candida albicans.

scholarly journals Prevalence of Methicillin-Resistant Staphylococcus aureus on Paper Currency Notes

2021 ◽  
pp. 25-32
Author(s):  
Rikhi Ram Marasini ◽  
Pratikshya Shrestha ◽  
Prabhat Dhakal ◽  
Sukra Raj Shrestha ◽  
Sirjana Adhikari ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Brain Heart Infusion ◽  
Biochemical Tests ◽  
Mannitol Salt Agar ◽  
Methicillin Resistant ◽  
Total Prevalence ◽  
Paper Currency ◽  
Antibiotic Susceptibility Test ◽  
Hygiene Measures

The main objective of this study was to determine the prevalence of Methicillin Resistant Staphylococcus aureus (MRSA) in paper currency. The paper currencies in circulation in Pokhara Metropolitan City were inspected. Bills of various denominations (Rs 5, 10, 20, 50, 100, 500 and 1000) were collected from five different locations; namely Food and Vegetable Shop, Bus conductor, Hospital Pharmacy, Butcher Shop and Grocery Shop. Collected sample were cultured and incubated for 24 hours at 37 oC in Brain Heart Infusion (BHI) Broth. The inoculums were further cultured on Mannitol Salt Agar (MSA) and Blood Agar (BA) media to obtain colonies, which were examined and evaluated for various parameters like gram staining and biochemical tests for identification. Then, antibiotic susceptibility test of the isolates was performed using standard procedures. A total of 35 sample of paper currency were processed, all of which showed positive growth. Out of 86 total isolates, 21 (24.42%) were Staphylococcus aureus followed by Coagulase Negative Staphylococci 19 (22.09%), Diptheroids 14 (16.3%), Bacillus spp 13 (15.11%), Micrococci 9 (10.46%), Streptococcus pneumonia 4 (4.65%), Viridans Streptococcus 4 (4.65%) and Streptococcus pyogenes 2 (2.32%). The total prevalence of MRSA in this study was 7 (33.33%). Paper currency contaminated with MRSA poses a high threat to those handling the bills as well as the community. Thus, this study suggests proper hygiene measures to be adopted after handling of paper currency to minimize the risk of contamination and emergence of diseases.

scholarly journals Hidden reservoirs of pathogens in dental settings

2021 ◽  
Vol 17 (1) ◽  
pp. 73-79
Author(s):  
Silpi Chatterjee ◽  
Keyword(s):  
Staphylococcus Aureus ◽  
Mobile Phones ◽  
Nosocomial Infections ◽  
Bacterial Species ◽  
Brain Heart Infusion ◽  
Bacillus Species ◽  
Coagulase Negative Staphylococcus ◽  
Cross Contamination ◽  
Sterile Saline ◽  
Predominant Species

Nosocomial infections are a major concern to both clinicians and health care seekers. Investigations have suggested that laptops & mobile phones may contribute to cross-contamination and can serve as vehicles for infection transmission. Therefore, it is of interest to document the data on hidden reservoirs such as mobile phones and laptops of pathogens in dental settings at the Hazaribag college of dental sciences and Hospital, Jharkhand. The samples were collected from 25 laptops and 25 mobile phones from dentists working in a dental college in Hazaribag city. The samples were collected aseptically using sterile cotton swabs dipped in sterile saline by rotating the swabs on the keyboard surfaces of laptops and mobile phones, inoculated into Brain Heart Infusion broth, vortexed for 1 minute in Fischer Vortex Genie 2 on highest setting & streaked immediately on 5% sheep blood agar plates and were incubated at 370C for 24 hours aerobically. The isolates were identified based on the colony morphology, colony characteristics and biochemical reactions. The bacterial species isolated were Staphylococcus aureus, Coagulase negative Staphylococcus, Bacillus species, Enterococci, Micrococci, and Pseudomonas etc. Predominant species isolated was Staphylococcus aureus and least was Micrococci. Higher percentage of organisms was found at the Department of Periodontics, Endodontics and least was found in Department of Public Health Dentistry. The percentage and type of organism isolated from keyboards of laptops and mobile phones were similar. Thus, laptops and mobile phones act as vehicles for transfer of potential pathogens associated with dental hospitals. Disinfecting the hands prior to examination of patients and disinfection of laptops and mobiles with alcohol wipes should be done to prevent nosocomial infections.

scholarly journals Prevalence and Characterization of Heterogeneous Vancomycin-Intermediate Staphylococcus aureus Isolates from 14 Cities in China

2009 ◽  
Vol 53 (9) ◽  
pp. 3642-3649 ◽  
Author(s):  
Wenjia Sun ◽  
Hongbin Chen ◽  
Yudong Liu ◽  
Chunjiang Zhao ◽  
Wright W. Nichols ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Population Analysis ◽  
Screening Method ◽  
Estimation Method ◽  
Area Under The Curve ◽  
Brain Heart Infusion ◽  
Screening Tests ◽  
Screening Methods ◽  
Large Numbers ◽  
Screening Cascade

ABSTRACT The prevalence of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) among 1,012 vancomycin-susceptible methicillin (meticillin)-resistant S. aureus isolates collected from 14 cities in China from 2005 to 2007 was 13 to 16%, as determined by a combination of (i) measurement by the modified population analysis profile-area under the curve method (PAP-AUC) and (ii) estimation from the measured sensitivity and specificity of a screening method. Two hundred isolates from blood were chosen as a subset for measurement of the sensitivities and the specificities of several previously described screening methods by using the results of PAP-AUC as the reference. During this testing, one isolate was found to be a vancomycin-intermediate S. aureus (VISA) strain so was not used in the evaluation of the screening tests. Of the other 199 isolates, 26 (13.1%) were hVISA, as assessed by PAP-AUC. A screening cascade of culturing the isolates on brain heart infusion agar containing teicoplanin (5 mg/liter) and then subjecting the positive isolates to a macro-Etest method was applied to the 812 non-blood isolates, yielding 149 positive results. From these results and by adjusting for sensitivity (0.423) and specificity (0.861), the prevalence was estimated to be 15.7%. The precision of that estimate was assessed by reapplying the screening cascade to 120 randomly selected isolates from the 812 non-blood isolates and simultaneously determining their heterogeneous vancomycin-intermediate susceptibility status by PAP-AUC. Because PAP-AUC is impractical for use with large numbers of isolates, the screening-based estimation method is useful as a first approximation of the prevalence of hVISA. Of the 27 VISA or hVISA isolates from blood, 22.2% and 74.1% were staphylococcal chromosome cassette mec types II and III, respectively, while 77.8% and 22.2% were agr type 1 and agr type 2, respectively; the MIC ranges were 0.5 to 4 mg/liter for vancomycin and 0.25 to 1 mg/liter for daptomycin.

Inactivation of Salmonella enterica serovar Typhimurium and Staphylococcus aureus in rice by radio-frequency heating

2021 ◽  
Author(s):  
Ki-Ok Jeong ◽  
Sang-Soon Kim ◽  
Sang-Hyun Park ◽  
Dong-Hyun Kang
Keyword(s):  
Staphylococcus Aureus ◽  
Radio Frequency ◽  
Heating Rate ◽  
Foodborne Pathogens ◽  
Color Change ◽  
Oryza Sativa L ◽  
Rf Heating ◽  
Pathogen Inactivation ◽  
Treatment Conditions ◽  
And Staphylococcus Aureus

The objectives of this study were to determine the effect of the milling degree (MD) of Oryza sativa L. (Korean rice) on the heating rate, pathogen inactivation (Salmonella Typhimurium and Staphylococcus aureus), and color change resulting from radio-frequency (RF) heating. Rice samples inoculated with pathogens were placed in a polypropylene jar and subjected to RF heating for 0-75 s. The heating rate of rice with a 2% MD was the highest during RF heating, followed by those with a 0, 8, and 10% MD, and the reduction of pathogens showed the same trend. The reduction of the levels of pathogens in rice with a MD 0 and 2% was significantly higher than that observed for rice with a MD of 8 and 10% under the same treatment conditions. For example, log reductions of S. Typhimurium in rice by 55 s RF heating were 3.64, 5.19, 2.18, and 1.80 for milling degree of 0, 2, 8, and 10%, respectively. At the same treatment conditions, log reduction of S. aureus were 2.77, 5.08, 1.15, and 0.90 for milling degree of 0, 2, 8, and 10%, respectively. The color of rice measured according to L*, a*, and b* was not significantly altered after RF heating, regardless of the MD. Therefore, the MD of rice should be considered before RF heating is applied to inactivate foodborne pathogens.

Effects of Potassium Sorbate on Normal Flora and on Staphylococcus aureus Added to Minced Cod

1982 ◽  
Vol 45 (9) ◽  
pp. 824-828 ◽  
Author(s):  
DONALD J. LYNCH ◽  
NORMAN N. POTTER
Keyword(s):  
Staphylococcus Aureus ◽  
Storage Period ◽  
Inhibitory Effect ◽  
Potassium Sorbate ◽  
Normal Flora ◽  
Ph Changes ◽  
Normal Microflora ◽  
Enterotoxin Production ◽  
Plate Counts ◽  
Storage Temperatures

Minced cod and pasteurized minced cod, with and without 0.5% potassium sorbate, were subjected to abusive storage temperatures of 7 and 15°C. Staphylococcus aureus FRI 100 was inoculated into the cod before storage. Total aerobic plate counts (20 and 35°C), pH changes, S. aureus counts and the presence of thermonuclease were monitored throughout the studies. With the unpasteurized minced cod, potassium sorbate caused slightly lower aerobic plate counts (at 20 and 35°C) in the 7°C study over an 11-day storage period. Psychrotrophic organisms were inhibited to a slightly greater extent than were mesophilic organisms. Inoculated S. aureus was quickly outgrown by the normal microflora without or with sorbate. Similar results were obtained at the still more abusive temperature of 15°C over a storage period of 5 d, but the inhibitory effect of sorbate was less evident. Pasteurized minced cod, inoculated with S. aureus and stored at 15°C, showed a considerable difference in growth of S. aureus with and without sorbate. Potassium sorbate resulted in a markedly slower rate of growth of the pathogen and a substantial delay of several days in production of detectable levels of thermonuclease. This delay in nuclease production is indicative of a similar delay in enterotoxin production.

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