Antimicrobial substances produced by Staphylococcus aureus strains isolated from cattle in Brazil

Among 46 isolates of Staphylococcus aureus obtained from cattle in the State of Paraíba, Brazil, four were shown to produce antimicrobial substances (AMS). The two best AMS producers carried single plasmids of about 8·0 kbp and 50 kbp, respectively, which were designated pRJ34 and pRJ35. Curing experiments and molecular analysis associated the AMS production with the presence of these plasmids in the cells. The biochemical properties exhibited by the AMS suggested that they might be bacteriocins (Bac). The bacteriocin encoded by pRJ34 showed properties identical to those of the bacteriocins encoded by other small staphylococcal Bac plasmids. However, the bacteriocin encoded by the large plasmid pRJ35 has shown some properties which distinguish it from the other bacteriocins of Staph. aureus described so far, suggesting it may be a new member of the staphylococcal bacteriocin family.     

Evaluation of six commercial identification kits for the identification of Staphylococcus aureus isolated from bovine mastitis

AIMS: Comparison of six commercially available in human medicine well-established slide agglutination systems for the identification of Staphylococcus aureus. METHODS AND RESULTS: Slide agglutination tests were compared with the conventional tube coagulase test, biochemical identification and with the molecular identification by polymerase chain reaction (PCR) amplification of species-specific parts of the gene encoding the 23S RNA. Systems evaluated included Masta-Staph (Mast Diagnostics), Staphylase-Test (Oxoid), Staphytect-Plus (Oxoid), Staphyloslide Latex (Becton Dickinson), Slidex Staph Plus (bioMerieux) and Dry Spot Staphytect Plus (Oxoid). A total of 141 staphylococcal strains isolated from cases of bovine mastitis including 90 S. aureus, 14 Staphylococcus epidermidis, 10 Staphylococcus warneri, 13 Staphylococcus xylosus, 11 Staphylococcus haemolyticus and three other coagulase-negative staphylococci were tested with each method. Staphylococcus aureus strains were selected by macrorestriction analysis with pulsed field gel electrophoresis (PFGE). Only genetically unrelated strains were included in the study. The sensitivities and specificities of the test were as follows: Masta-Staph 86.7 and 90.1%, Staphylase-Test 78.4 and 85.1%, Staphytect-Plus 81.1 and 86.5%, Staphyloslide Latex 77.8 and 84.4%, Slidex Staph Plus 77.8 and 84.4%, Dry Spot Staphytect Plus 75.6 and 83.0%. CONCLUSIONS: The results of this evaluation suggest that the six slide agglutination methods tested can provide rapid identification of S. aureus also from bovine mastitis. The sensitivity and specificity seems to be less than those reported from human S. aureus isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: This is one of the first comparative reported investigations about the applicability of different commercially available slide agglutination tests for the detection of S. aureus from bovine mastitis using PFGE selected clinical isolates.     

Detection of enterotoxins and TSST-1 secreted by Staphylococcus aureus isolated from ruminant mastitis. Comparison of ELISA and immunoblot

J.A. ORDEN, J. GOYACHE, J. HERNÁNDEZ, A. DOMÉNECH, G. SUÁREZ AND E. GÓMEZ-LUCÍA. 1992. The production of staphylococcal enterotoxins (SE) and toxic shock syndrome toxin-1 (TSST-1) was studied in 81 strains of Staphylococcus aureus isolated from cases of mastitis in cattle, goats and sheep. SE and TSST-1 were detected by two techniques: ELISA double antibody sandwich, and an immunoblot technique combined with a semiautomated electrophoresis system. More Staph. aureus strains isolated from sheep produced enterotoxins than those from goats and cattle. SEC was the predominant type in all isolates from these animal species. The highest proportion of strains producing TSST-1 were obtained from sheep, twice as many as those from goats or cows. The two techniques gave similar results. as all the strains positive by immunoblot were also positive by ELISA, and only three were positive by ELISA but negative by immunoblot.     

Comparison of commercially available kits with standard methods for detection of Salmonella strains in foods.

Six commercial kits were compared with the U.S. Food and Drug Administration (USFDA) method and the Japanese standard method for Salmonella isolation in foods. When only Salmonella serovars were tested, many of the methods performed well; however, when foods were artificially inoculated, only the USFDA method and immunomagnetic separation coupled with the xylose-lysine-brilliant green agar method (MS-XLBG) could positively detect Salmonella serovars. All seven wild-type Salmonella serovars were detected by the USFDA method, and the MS-XLBG method detected salmonellae from six samples.     

Detection of enterotoxins and TSST-1 secreted by Staphylococcus aureus isolated from ruminant mastitis. Comparison of ELISA and immunoblot.

The production of staphylococcal enterotoxins (SE) and toxic shock syndrome toxin-1 (TSST-1) was studied in 81 strains of Staphylococcus aureus isolated from cases of mastitis in cattle, goats and sheep. SE and TSST-1 were detected by two techniques: ELISA double antibody sandwich, and an immunoblot technique combined with a semiautomated electrophoresis system. More Staph. aureus strains isolated from sheep produced enterotoxins than those from goats and cattle. SEC was the predominant type in all isolates from these animal species. The highest proportion of strains producing TSST-1 were obtained from sheep, twice as many as those from goats or cows. The two techniques gave similar results, as all the strains positive by immunoblot were also positive by ELISA, and only three were positive by ELISA but negative by immunoblot.     

Genotyping of Staphylococcus aureus strains isolated from healthy persistent carriers

The paper presents results on the relatedness of Staphylococcus aureus strains colonizing the upper respiratory tract isolated from healthy persistent carriers. Genotyping was carried out using two methods—multiple-locus variable-number tandem-repeat fingerprinting (MLVF) and pulsed-field gel electrophoresis (PFGE). By comparison of the results obtained by both methods, good correlations between MLVF and PFGE genotyping of strains isolated from the asymptomatic carriers were observed. Further studies are needed to evaluate methods useful for genotyping of S. aureus strains circulating in the community.     

The characteristic of Staphylococcus aureus strains isolated from food's samples

The study was carried out of 22 isolates of S. aureus isolated from 7 different incriminated food's samples from foodborne-disease outbreaks. The possibility of these isolates to producing of enterotoxins by commercial test SET-RPLA (Oxoid) was tested. The genotyping of these isolates was done by pulse-filed gel electrophoresis, acc. to Pfaller in own modification. On the basis of the DNA restriction patterns of the 22 isolates--5 strains were singled out, one of these strains--strain V (isolat nr 7) was not relationship to others. It was found that this strain V was one enterotoxin produced. Additionaly, all tested strains, in spite of the strain nr V, were isolated from the 2 or 3 samples of different kinds of foods. In the present study it has been shown too, that several similar colonies should be isolated for farther studies to assess microbiological contamination of the food products properly.     

Immunochemical analysis of a Smith-like antigen isolated from two human strains of Staphylococcus aureus.

A surface antigen consisting of aminoglucuronic acid and N-acetyl-L-alanine was isolated from the culture filtrates of two human strains of Staphylococcus aureus. Double diffusion analysis in agar suggested that the antigen is immunologically similar to the alanyl-aminoglucuronic acid capsule of the Smith strain of S. aureus. Quantitative precipitin inhibition studies indicated that N-acetyl-L-alanine is the immunodominant determinant of the acidic antigen. In addition, conjugates consisting of N-acetyl-L-alanine coupled to bovine serum albumin gave a significant precipitin reaction with anti-staphylococcal serum which is rich in alanyl-aminoglucuronic acid polymer antibodies. Antibodies with N-acetyl-L-alanine specificity were isolated from N-acetyl-L-alanine-Sepharose immunoabsorbent columns. Double diffusion analysis in agar indicated that the eluted antibodies were serologically reactive and belonged to the IgG class of immunoglobulins.     

Production of enterotoxins and toxic shock syndrome toxin by Staphylococcus aureus isolated from bovine mastitis in Brazil

The production of toxic shock syndrome toxin 1 (TSST-1) and enterotoxins (SE) A, B, C and D by bovine mastitis isolates of Staphylococcus aureus was evaluated by immunodiffusion using the Optimum-Sensitivity Plate method. S. aureus strains were isolated from bovine mastitis in 23 dairy herds in the state of Minas Gerais, Brazil, during 1994-9. Of 127 isolates, 83 (65.04%) produced one or several toxins, and among them production of SE was found in 54 (43.0%) isolates, of which 1138 (29.09%) secreted enterotoxin identified as type D. TSST-1 was found in 5829 (45.723.0%) isolates.     

Antibiotic resistance of Staphylococcus aureus strains isolated in two different Warsaw hospitals]

S. aureus strains isolated in the same period from different specimens obtained from patients of two different hospitals were compared. The significant differences were observed in the frequency of resistance determinants between strains of these hospitals. The most important was the difference in the prevalence of MRSA. In the first hospital the percentage of MRSA was 40% whereas in the second one only 20%. The resistance to the other antibiotics was also compared, and independently from the compared group: MRSA, MSSA or all, the prevalence of resistance determinants was higher in the first hospital than in the second. Although the frequencies of MRSA in both investigated hospitals were relatively high comparing to the other European countries and in the first hospital even alarming, isolated MRSA strains are less resistant to other antibiotics than MRSA in other countries.     

The molecular characteristic of Staphylococcus aureus and Staphylococcus epidermidis strains isolated from clinical sources

The aim of study was the molecular characteristic of S. aureus and S. epidermidis isolates obtained from skin surface, wounds, deep tissues of hospitalized patients and from skin surface of non-hospitalized patients. Genes encoding virulence factors were examined using PCR reaction and specific primers. Genes encoding adhesinsfnbA and cna and gene eta for epidermolytic toxin were mostly present in S. aureus isolates coming from wounds and deep tissues compared to these from skin surface. Gene atlE encoding autolysin of S. epidermidis was detected in all studied isolates, whereas gene icaAB was present in almost all isolates. Comparison of results obtained by PCR and conventional method of the resistance to methicillin estimation showed discrepances suggesting the need for using of both methods in some clinically difficult cases of S. aureus infection.     

VISA and hetero-VISA among Staphylococcus aureus strains isolated from clinical cases

The VISA (vancomycin intermediate Staphylococcus aureus) and hetero-VISA strains were found among all isolates of S. aureus obtained in the years 1997-2000. The frequency of VISA was 0.3% and h-VISA was about 3%. Most but not all of the h-VISA and all VISA strains were methicillin resistant. Moreover the usefulness of different methods enabling recognition of the h-VISA strains was compared.     

A simplified system for biotyping Staphylococcus aureus strains isolated from different animal species

D evriese , L.A. 1984. A simplified system for biotyping Staphylococcus aureus strains isolated from different animal species. Journal of Applied Bacteriology 56 , 215–220.
A biotyping system for Staphylococcus aureus strains is proposed which is a simplified version of biotyping procedures described in the literature. It differentiates Staph. aureus strains from man and animals into host-specific ecovars and biotypes which are not host-specific. With the help of tests for βhaemolysin, staphylokinase, coagulation of bovine plasma and the crystal-violet reaction, the origin of many but not all Staph. aureus strains can be determined: 604 of 809 strains from man. poultry, cattle, pigs, goats, rabbits and foods could be alloted to four ecovars which are typically associated with man, poultry, sheep and goats and cattle. The other strains belonged to five non-host specific biotypes.     

Comparison of type A enterotoxigenic Staphylococcus aureus strains isolated from geographically far distant locations by pulsed field gel electrophoresis

Staphylococcal enterotoxin A (SEA) is one of the major staphylococcal enterotoxins which may cause food-borne outbreaks. In order to investigate the difference in genomic types and to elucidate the most disseminated strains for enterotoxin A-producing strains of Staphylococcus aureus , a total of 60 SEA Staph. aureus strains isolated from food and clinical samples in Taiwan and 30 strains of the same enterotoxigenic type of strains obtained from geographically far distant locations were compared for their pulsed field gel electrophoresis (PFGE) patterns. The rare cutting endonuclease Sma I generated 10 distinct genome patterns for the 60 local SEA isolates and 15 and eight genome patterns, respectively, for the 20 and 10 SEA strains originally isolated from the USA and other countries. The local isolates are less diverse in genome patterns as compared to the US isolates. Of all these PFGE patterns, a certain pattern, such as pattern 3, is shared by the food and clinical isolates and the local and foreign isolates. Thus, although SEA Staph. aureus strains from geographically far distant locations showed considerable genetic diversity, PFGE pattern 3 strain might be one of the most disseminated strains.     

Production of enterotoxins by strains of Escherichia coli isolated from pigs

The production of enterotoxins by 237 hemolytic strains of Escherichia coli isolated from pigs was determined with the use of CTE in CHO. Vero and Hela cells and ILT. More frequent (p less than 0.01) production of enterotoxins, determined by ILT, was found for the serotypes being pathogenic for the animals (63.8% of the strains). No correlation between intensity of ILT and particular serotype was observed. Both the serotypes pathogenic for pigs and other serotypes produced LT enterotoxins and ST toxin. The frequency of LT enterotoxin production was statistically insignificant compared to the frequency of ST enterotoxin production by strains with serotypes pathogenic for the pigs. Strains of E. coli producing only enterotoxin ST belonged both to the pathogenic serotypes as well as to other hemolytic serotypes. The cytotoxic activity of supernatants of E. coli strains with different serotypes isolated from pigs in Vero and Hela cells and simultaneous CTE in CHO cells was observed. This suggests the production by the strains of enterotoxin LT and cytotoxin VT. Seven out of the 96 isolates showing CTE in CHO cells gave no reaction in the ILT in pigs. This suggests the production by these isolates of a toxin (toxins) differing from the E. coli enterotoxins.     

Comparison of disk-diffusion method and PCR for detection of methicillin resistance in Staphylococcus aureus strains

The aim of the study was to compare the disk-diffusion (oxacillin 1 microg, cefoxitin 30 microg) method and PCR for detection of methicillin-resistance in S. aureus. The investigation were carried out on 120 S. aureus strains isolated from clinical materials of patients hospitalized in the University Hospital at the L. Rydygier Collegium Medicum in Bydgoszcz, University of Nicolaus Copernicus in Toruń. Of the 120 S. aureus strains tested, 60 (50%) were mecA-positive by PCR. Consistency of results between oxacillin disk-difussion method and PCR amounted 92.5% and cefoxitin disk-diffusion method and PCR--98.3%. The oxacillin disk-difussion method falsely identified 3 (2.5%) strains as MSSA (sensitivity 95.0%) and 4 strains as MRSA (specificity 93.3%) in comparison with PCR. The cefoxitin disk-diffusion method falsely identified 2 (1.6%) strains as MSSA (sensitivity 96.7%) and there were no false resistant results (specificity 100%). Our results showed that in disk-diffusion tests, cefoxitin is a better than oxacillin for the identification of MRSA.