Isolation of strains of a new ecological variant of Staphylococcus aureus from asses

47 coagulase-positive staphylococcal strains were isolated from the nasal smears of 175 healthy donkeys. In accordance with the schemes of Akatov--Devriese and Mayer-Witte--Akatov, 10.6% of the cultures were classified with the coagulase-positive species S. hyicus and 89.3%, with the species S. aureus. Out of S. aureus strains, 11.9% were found to have the characteristics of ecovar hominis, while 16.2% of the cultures could not be classified with definite ecovars. Most of the strains (71.4%) were found to differ from the known ecovars of S. aureus in their biological properties. For this reason, the above strains were classified with the new ecovar asinae. The authors propose to make the existing S. aureus identification scheme (the scheme of Mayer-Witte--Akatov) more complete by adding the tests for hyaluronidase and phosphatase.     

Characterization of Staphylococcus aureus strains involved in human and bovine mastitis

Staphylococcus aureus is one of the main etiological agents of mastitis in different mammalian species. At present, it is unknown whether strains isolated from human mastitis cases share phenotypic properties and genetic background with those obtained from animal mastitis cases. Therefore, the objective of this study was to characterize S. aureus strains isolated from women with lactational mastitis and to compare them with the strains responsible for bovine mastitis and noninfectious strains. All the strains were genotyped by both pulsed field gel electrophoresis and multilocus sequence typing and submitted to a characterization scheme that included diverse assays related to pathogenic potential and antibiotic resistance. Apart from siderophore production, no significant association was observed between the strains from bovine and human mastitis. Statistical differences between human- and bovine-mastitis-associated strains were detected for some traits and virulence determinants, such as the presence of prophages and cna and hlb genes, which were more frequently found within the bovine group. On the contrary, resistance to penicillin was significantly higher among strains isolated from human lactational mastitis, probably related to the common presence of the blaZ gene. A high genetic diversity was found among the strains involved in mastitis in breastfeeding women.     

Detection of low-enterotoxin-producing Staphylococcus aureus strains

Culture supernatant fluids from 26 (23.6%) monkey feeding test-positive Staphylococcus aureus strains, negative for enterotoxins by gel diffusion, were positive by enzyme-linked immunosorbent assay for one or more of the identified enterotoxins. Staphylococcal enterotoxin D (SED) was produced by 23 (88.5%) strains, SED and SEA were produced in two strains, and SED and SEC were produced in one strain. One strain produced only SEA, and two strains produced only SEC.     

Characterization of hemolytic activity of Staphylococcus aureus strains isolated from bovine mastitic milk

Beta (beta) and delta (delta)-hemolysin of Staphylococcus aureus strains were cultured in vitro in milk lactoserum (whey) prepared from both healthy and mastitis bovine milk. Production of beta- and delta-hemolysins were detected in 12 out of 50 strains studied. The association between N-acetyl-beta-D-glucosaminidase (NAGase) activity, plasmin activity (PL) and trypsin inhibitory capacity (TIC), known as inflammatory indicators for mastitis, and hemolytic activity were also studied. Mastitic milk decreased directly the lytic effect of both beta-and delta-hemolysins of S. aureus on hemolytical blood agar plates. S. aureus in healthy milk samples produced more beta-hemolysin (3 times) and delta-hemolysin (2 times) when compared to S. aureus supernatants in milk from infected quarters. Furthermore, beta- and delta-hemolysis correlated negatively with TIC and NAGase and PL activities. Addition of reduced glutathione (GSH) or beta-mercaptoethanol into the artificial medium enhanced hemolysins activity.     

Detection of low-enterotoxin-producing Staphylococcus aureus strains.

Culture supernatant fluids from 26 (23.6%) monkey feeding test-positive Staphylococcus aureus strains, negative for enterotoxins by gel diffusion, were positive by enzyme-linked immunosorbent assay for one or more of the identified enterotoxins. Staphylococcal enterotoxin D (SED) was produced by 23 (88.5%) strains, SED and SEA were produced in two strains, and SED and SEC were produced in one strain. One strain produced only SEA, and two strains produced only SEC.     

253株金黄色葡萄球菌耐药现状分析

目的 了解医院金黄色葡萄球菌临床分布情况及其对常用抗菌药物的耐药率,为临床合理使用抗菌药物提供依据.方法 回顾分析医院2010年5月至2011年4月检出的金黄色葡萄球菌,采用VITEK-AMS全自动微生物分析仪进行菌种鉴定和药敏分析.结果 共检出金黄色葡萄球菌253株,菌株的主要来源为痰130株(51.4％)、血液39株(15.4％)、创面24株(9.5％);菌株主要科室分布前3位是神内科35株(13.8％)、ICU30( 11.8％)、脑外科26株(10.3％);其中耐甲氧西林金黄色葡萄球菌( MRSA)为165株(65.2％),MRSA对多种抗菌药物耐药率＞70.0％,MSSA为88株(34.8％),对除青霉素、红霉素外的大多数抗菌药物敏感,未发现耐万古霉素菌株.结论 MRSA检出率高,耐药现状严重,应加强对金黄色葡萄球菌耐药性的监测,并根据药敏试验结果合理使用抗菌药物.     

Glycine dependence of Staphylococcus aureus strains]

Glycine dependent Staphylococcus aureus var. bovis strains (TSCHAPE and RISCHE 1971) were tested for their ability to grow on glycine containing and glycine deprived media. We observed glycine dependence only in minimal media. In complete media the strains grew in absence of glycine. Testing the ability of some glycine precursors we found that in minimal media glycine could be replaced by threonine and in some cases by serine. One mutant (Gly 100 Glyox.r.) was able to metabolize glyoxylate instead of glycine. Aspartic acid was metabolized in presence of glycine. Using 14C-aspartic acid we detected 14C-glycine and 14C-threonine. Presumably the bacteria metabolize aspartic acid to glycine via threonine.     

Characterization of a Staphylococcus aureus Bacteriocin

The bacteriocin produced by a strain of Staphylococcus aureus has been isolated and designated staphylococcin (414), and a study was made of its chemical, physical, and biological properties. The staphylococcin is released in appreciable quantities after breakage of the cells and can be purified through differential centrifugation and column chromatography. In the native state, it appears to be a lipoprotein-carbohydrate complex with a molecular weight in excess of 200,000. The complex can be dissociated by sodium dodecyl sulfate into smaller subunits which retain activity. The gross chemical and physical properties of the bacteriocin closely resemble those ascribed to certain preparations of cell membranes. Staphylococcin (414) is not a lytic enzyme like lysostaphin and does not have the same spectrum of activity. Like other bacteriocins from gram-positive microorganisms, it does not inhibit any gram-negative bacteria, but does inhibit several other genera.     

Characterization of specific egg yolk immunoglobulin (IgY) against mastitis-causing Staphylococcus aureus

Aims: To evaluate the in vitro activity of egg yolk immunoglobulin (IgY) against mastitis-causing Staphylococcus aureus. Methods and Results: Specific IgY was produced by immunizing hens with formaldehyde-killed Staph. aureus, using a bacterial strain known to cause mastitis. The IgY, of 94% purity, was obtained from yolks by water dilution, salt precipitations, ultrafiltration and gel filtration. ELISA indicated that the IgY produced was specific to the antigen and five Staph. aureus isolates obtained from mastitic cows. The growth of Staph. aureus was inhibited by specific IgY at concentrations from 1 to 10 mg ml⁻¹ in a dose-dependent manner. The phagocytosis of Staph. aureus by milk macrophages was enhanced in the presence of specific IgY with the highest phagocytic percentage being 30% higher than that without IgY (P < 0·05). Conclusions: The specific IgY against mastitis-causing Staph. aureus inhibited the growth of Staph. aureus and enhanced the phagocytosis of Staph. aureus by milk macrophages. Significance and Impact of the Study: Specific IgY would be a potential treatment for bovine mastitis.     

Antiseptic resistance of clinical strains of Staphylococcus aureus

To evaluate the activity of antiseptics and the sensitivity-resistance of bacteria to antiseptics, a number of characteristics has been used, including the minimum inhibiting concentration for different strains, the frequency of statistical and clinical resistance, the antiseptic activity index. A wide spread of S. aureus strains isolated from patients with hospital infections has been revealed. Differences in the resistance of bacterial strains have been established, depending on the type of the antiseptic and the ecovar of bacteria: among hospital ecovars, resistant strains occur more frequently and can resist a wider range of antibiotics. In staphylococcal hospital ecovars the occurrence and level of resistance to a number of widely used antiseptics increase with time. In connection with a wide spread of staphylococcal hospital strains resistant to antiseptics, measures on the control of the circulation of such strains should be introduced into hospitals, and the data thus obtained should be used for the periodic reevaluation of antiseptics used in medical practice and for the choice of preparations to be used for individual therapeutic and prophylactic antisepsis.     

Characteristics of penicillinase plasmids from Staphylococcus aureus strains

Penicillinase plasmids are present in most MRSA strains. They are very varying in their genotype and phenotype they confer. Penicillinase plasmids were transduced from 80 hospital MRSA strains to NCTC 8325 and the phenotype as well as the incompatibility group of plasmid were determined. Resistance to cadmium (high and low level), resistance to organic and nonorganic mercury compounds, arsenate/arsenite/antimonium resistance, resistance to bismuth and hypersensitivity to bismuth, resistance to macrolides as well as beta-lactamase production and its inductibility were checked. Among the examined strains 20 different phenotypes of penicillinase plasmids were found. Patterns of penicillinase plasmids were compared to DNA patterns of the investigated strains after digestion with SmaI and separation in pulsed field electrophoresis (PFGE). It was shown that strains with the same PFGE pattern often differ in the type of their penicillinase plasmid. Determining of penicillinase plasmid phenotype could be useful in differentiating S. aureus strains sharing the same pattern of PFGE.     

Characterization of MLS(b) resistance among Staphylococcus aureus and Staphylococcus epidermidis isolates carrying different SCCmec types

This work characterizes MLS(b) resistance in 39 methicillin-resistant Staphylococcus aureus (MRSA) and 32 Staphylococcus epidermidis (MRSE) isolates. Of 21 erm(A) gene encoding MRSA isolates, 71.4% carried SCCmecIII, whereas of 12 isolates carrying the erm(C) gene, 83.3% carried SCCmecIV. Among the 25 MRSE isolates positive for the erm(C) gene, 80% had SCCmecIV or nontypeable cassettes. Isolates carrying these genes had MIC(90) ≥ 256 μg/mL to erythromycin and clindamycin. The msr(A) gene was associated with a low MIC(90) to these drugs. The erm(A) gene was associated with SCCmecIII in MRSA isolates, whereas the erm(C) gene was associated with SCCmecIV in both MRSA and MRSE isolates.     

Characterization of Staphylococcus aureus SarA binding sites

The staphylococcal accessory regulator locus (sarA) encodes a DNA-binding protein (SarA) that modulates expression of over 100 genes. Whether this occurs via a direct interaction between SarA and cis elements associated with its target genes is unclear, partly because the definitive characteristics of a SarA binding site have not been identified. In this work, electrophoretic mobility shift assays (EMSAs) were used to identify a SarA binding site(s) upstream of the SarA-regulated gene cna. The results suggest the existence of multiple high-affinity binding sites within the cna promoter region. Using a SELEX (systematic evolution of ligands by exponential enrichment) procedure and purified, recombinant SarA, we also selected DNA targets that contain a high-affinity SarA binding site from a random pool of DNA fragments. These fragments were subsequently cloned and sequenced. Randomly chosen clones were also examined by EMSA. These DNA fragments bound SarA with affinities comparable to those of recognized SarA-regulated genes, including cna, fnbA, and sspA. The composition of SarA-selected DNAs was AT rich, which is consistent with the nucleotide composition of the Staphylococcus aureus genome. Alignment of selected DNAs revealed a 7-bp consensus (ATTTTAT) that was present with no more than one mismatch in 46 of 56 sequenced clones. By using the same criteria, consensus binding sites were also identified upstream of the S. aureus genes spa, fnbA, sspA, agr, hla, and cna. With the exception of cna, which has not been previously examined, this 7-bp motif was within the putative SarA binding site previously associated with each gene.     

Characterization of Staphylococcus aureus strains isolated from cystic fibrosis patients by conventional and molecular typing

The phenotypic and genotypic characteristics of Staphylococcus aureus strains isolated from respiratory tract of cystic fibrosis (CF) patients were investigated. Slime production, cell-surface hydrophobicity, type of capsular polysaccharide, profile of heteroresistance to methicillin and Sma I restriction profiles were evaluated. S. aureus CF strains have been shown to be heterogeneous in respect to several important features. All of them were slime producing with variation in colony morphology. High or moderate cell-surface hydrophobicity (CSH) was found for, respectively, 16.2% and 83.8% strains. Thirty strains were resistant to methicillin, 60% of them showed heteroresitance and 40% were homoresistant. It was found that 59.6% of strains produced capsular polysaccharides (CP) of 5 or 8 type. Among CP5/CP8 strains, CP8 was the predominant type (81.1%). Typing of 62 CF strains by macrorestriction analysis of chromosomal DNA revealed several major types, differing in their SmaI profiles with a similarity coefficient lower than 0.4. Some of the strains isolated from the same patient at different times of hospitalization, as well as strains isolated at the same time from the relatives, were identical in their PFGE pattern.     

Occurrence of adhesin genes in coagulase-negative Staphylococcus aureus strains

Sixty fenotypically coagulase-negative Staphylococcus aureus strains were screened for the presence of six adhesion genes. The strains were isolated from varied clinical samples and varied patients in 16 medical centers, in majority from the region of Gdansk. Multiplex PCR in two primer sets was used for detection of the following genes: bbp (bone binding protein), cna (collagen binding protein), ebp (elastin binding protein)and fnbB (fibronectin B binding protein), fib (fibrinogen bindng protein) and clfA (clunmping factor A). More than half (57%) of the examined population harbored four genes: fnbB,fib, cna i clfA. All of the strains were found to be clfA positive and 90% of them were positive for fnbB, 90% for fib and 67% for cna. All of these genes were significantly more common in MRSA than in MSSA. The particular genes were occurred in strains derived from varied clinical samples.     

Characterization of a holin (HolNU3-1) in methicillin-resistant Staphylococcus aureus host

The gene encoding holin protein HolNU3-1 from a clinical isolate of methicillin-resistant Staphylococcus aureus (MRSA) NU3-1 was cloned and expressed in S. aureus RN4220. HolNU3-1 encoded by the holNU3-1 gene, which is located upstream of the deleted endolysin gene, was functional. Expression of the holNU3-1 gene induced a decrease in culture turbidity and formation of translucent (empty ghost) cells in S. aureus. We found heterogeneity of the holin genes and diversity of the two-component lysis system, which consists of holin and endolysin, in MRSA hosts. We suggest that this diversity is important in the identification of the evolution of clinical isolates of S. aureus.