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- A cross-sectional study was conducted to determine the prevalence of and factors associated with Shiga toxin–producing Escherichia coli (STEC) in raw beef and ready-to-eat (RTE) beef products sold in 31 retail outlets in Pretoria, South Africa, and nearby areas. A total of 463 beef and RTE samples were screened for four STEC virulence genes (stx1, stx2, eaeA, and hlyA) and seven O-serogroups (O113, O157, O26, O91, O145, O111, and O103) with a multiplex PCR assay. The total aerobic plate count (TAPC) per gram was also determined. A total of 38 STEC isolates were recovered and characterized by conventional PCR assay and serotyping. The overall prevalence of STEC in the beef and RTE samples tested was 16.4% (76 of 463 samples; 95% confidence interval, 13 to 20%). The prevalence of STEC differed significantly by product type (P , 0.0001), with the highest prevalence (35%) detected in boerewors (spicy sausage). The STEC prevalences in minced beef, brisket, RTE cold beef, and biltong were 18, 13, 9, and 5%, respectively. The most frequently detected stx gene was stx2 (13%), and STEC serogroups from recovered isolates were detected at the following prevalences: O2, 15%; O8, 12%; O13, 15%; O20, 8%; O24, 3%; O39, 3%; O41, 8%; O71, 3%; O76, 3%; O150, 12%; and O174, 3%. A high proportion (77%) of the samples had TAPCs that exceeded the South African microbiological standards for meat export (5.0 log CFU/g). The prevalence of O157 STEC (16%) and the diversity of non-O157 STEC serogroups found in five common beef-based products from retail outlets in South Africa suggest exposure of raw beef and beef products to multiple contamination sources during carcass processing and/or cutting and handling at retail outlets. These data provide direct estimates of the potential health risk to consumers from undercooked contaminated products and indicate the need to improve sanitary practices during slaughter and processing of beef and beef-based RTE products. A risk-based surveillance system for STEC may be needed
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- The aim of this investigation was to isolate an antimicrobial compound from a microorganism and to determine the structure of the compound. In this investigation a hundred and twenty-one isolates were found and isolated with antimicrobial activity against Pseudomonas aeruginosa and Escherichia coli. These isolates were mostly encountered in soil in the Potchefstroom region in the R. S. A. With the double-layer agar method, spread plates were prepared from different samples and after an incubation period the colonies are covered with a thin layer of nutrient agar inoculated with an indicator-organism. After a second incubation the colonies with a clear zone were isolated and tested with the cross-streak method f or antimicrobial activity against other indicator bacteria. The presumptive antimicrobial producers were reduced to five isolates resulting from their activity against the pathogen bacteria. These isolates were purified and identified while checking f or already known ant5microbial producers. Two of these isolates were Gram-positive spore forming bacilli and three were gram-negative bacilli. The Gram positive bacilli are Bacillus coagulants and the Gram negative bacilli are Enterobacter agglomerants’. Although both types of organisms showed great potential f or further research it was decided to confine research on B. coagulans because most of the antibiotic producers are Gram-positive and the Gram-negative bacteria are better known f or bacteriocine production. B. coagulans was cultivated in large volumes in the presence of air at 37° C and the broth was vacuum distillated at 37° C. The concentrate was extracted in different ways using organic solvents. During these e extraction procedures the extracts were continuously tested f or antimicrobial activity specifically against Bacillus pumilus . The reason f or using the last-named organism as an indicator organism during the extractions is that this organism is very sensitive to this specific antimicrobial compound. The extracts were purified and separated in different components by using silica gel columns, re-extractions and high pressure liquid chromatography (HPLC) . During this re-extractions, three different antimicrobial compounds were identified, namely an organic acid, an amine compound and a neutral compound. These components were tested f or antimici-obial activity after which gas chromatograph-mass spectrometer analyses were done on the organic acid and the amine compound. acid was identified as benzoic acid. The organic acid was identified as benzoic acid. Die doel van hierdie ondersoek was om 'n antimikrobiese komponent uit n organisme te isoleer en te karak teriseer. In hierdie ondersoek is honderd een en twintig isolate geisoleer wat antimikrobiese aktiwiteit teen Pseudomonas aeruginosa en Escherichia coli getoon het. Hierdie isolate is veral in grand in die Potchefstroom-omgewing in die R. S.A. gevind. Met die dubbellaagagarmetode is spreiplate van die verskillende monsters berei en die kolonies is na inkubasie met n lagie voedingsagar bedek wat met n indikator-organisme geinokuleer is. Die organismes wat na die eerste inkubasie 'n helder sone daaromheen vertoon het, is geisoleer en verder met die kruisstrykmetode getoets vir antimikrobiese aktiwiteit teenoor ander indikator-bakteriee. Die potensiele antibiotikum-produseerders is op grand van hul antimikrobiese a tiwiteit na vyf isolate gereduseer. Hierdie isolate is gesuiwer en geidentifiseer met die doel om vas te stel of dit nie alreeds bekende antibiotikum-produseerders is nie. Hierdie isolate was nie bekend vir die produksie van antibiotika nie. Van hierdie vyf was twee Grampositiewe spoorvormende basille en drie Gramnegatiewe basilie. Albei die Grampositiewe organismes was Bacillus coagulans en al drie die x iv Gramnegatiewe organismes was Enterobacter agglomerans. Alhoewel albei organismes groat potensiaal besit het vir verdere ondersoek is daar veral op B. coagulans gekonsentreer omdat die meeste antibiotika van die Grampositiewe bakteriee afkomstig is en die Gramnegatiewe bakteriee oor die algemeen meer bekend is vir die produksie van bakteriosiene. B. coagulans is daarna op groat skaal met belugting by 37 ° C gekweek en die voedingsoppe is onder vakuum by 37 ° C afgedamp. Hierdie konsentrate is op verskillende wyses met verskillende organiese verbindings geekstraheer. Gedurende die verskillende ekstraksiemetodes is daar deurentyd vir antimikrobiese aktiwiteit getoets teen veral Bacillus pumilus. Laasgenoemde organisme is as deurlopende toetsorganisme gebruik omdat dit baie gevoelig was vir antimikrobiese verbindings vanaf B. coagulans. Die ekstrakte wat verkry is, is daarna met silikagel kolomme, herekstraksies en hoedruk-vloeistof chromatografiE (HPLC) in verskillende komponente opgebreek. Tydens die herekstraksies is drie verskillende antimikrobiese verbindings geidentifiseer, naamlik n orgdniese suur, n amienverbinding en n neutrale verbinding. Hierdie Komponente is vir antimikrobiese aktiwiteit getoets waarna gaschromatograaf-massaspektrometer-analises op die organiese suur en die amienverbinding gedoen is. Die organiese suur is as bensoesuur geidentifiseer.
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- Antimicrobials (AM) are used for growth promotion and therapy in pig production. Its misuse has led to the development of resistant organisms. We evaluated Escherichia coli virulence genes, and compared phenotypic–genotypic antimicrobial resistance (AMR) patterns of faecal E. coli from pigs receiving routine farm treatment without antimicrobial agents against pigs treated routinely with AM over 70 days. Recovered E. coli were tested for AMR using disk diffusion and polymerase chain reaction. Virulence genes were detected in 24.8% of isolates from antimicrobial group and 43.5% from non-antimicrobial group (p = 0.002). The proportion of virulence genes heat-stable enterotoxins a & b (STa, STb), enteroaggregative heat stable enterotoxin 1 [EAST1] and Shiga toxin type 2e [Stx2e]) were 18.1%, 0.0%, 78.7% and 3.0% for antimicrobial group and 14.8%, 8.5%, 85.1% and 12.7% for non-antimicrobial groups, respectively. Resistance to oxytetracycline was most common (p = 0.03) in samples collected between days 10 and 21. Resistance shifted to amoxicillin on days 56–70, and trimethoprim resistance was observed throughout. Seventeen phenotypic AMR combinations were observed and eight were multidrug resistant. At least one tetracycline resistance gene was found in 63.9% of the isolates. tet (A) (23.3%) was most common in the antimicrobial group, whereas tet (B) (43.5%) was prevalent in the non antimicrobial group. Usage or non-usage of antimicrobial agents in growing pigs does not preclude virulence genes development and other complex factors may be involved as previously described. Heavily used AM correspond to the degree of resistance and tetracycline resistance genes were detected during the growth phase.
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