Search

The characterization of Staphylococcus aureus isolates from buffalo, bovine, ovine and caprine milk samples collected in Rio de Janeiro state, Brazil was studied. Major clone A in different herds was detected among all species and in infection, while colonization samples showed its geographical spread among Rio de Janeiro state.

A mufF conditional mutant was used to evaluate the effect of suboptimal transcription of this on the transcriptome of the methicillin-resistant Staphylococcus aureus strain COL. The mutant was grown in the presence of optimal and suboptimal concentrations of the inducer, and the relative levels of transcription of genes were evaluated genome wide with an Affymetrix DNA microarray that included all open reading frames (ORFs) as well as intergenic sequences derived from four sequenced S. aureus strains. Using a sensitivity threshold value of 1.5, suboptimal expression of murF altered the transcription of a surprisingly large number of genes, i.e., 668 out of the 2,740 ORFs (close to one-fourth of all ORFs), of the genome ofS. aureus strain COL. The genes with altered transcription were distributed evenly around the S. aureus chromosome, and groups of genes involved with distinct metabolic functions responded in unique and operon-specific manners to modulation in murF transcription. For instance, all genes belonging to the isd operon and all but 2 of the 35 genes of prophage L54a were down-regulated, whereas all but one of the 21 members of the vraSR regulon and most of the 79 virulence-related genes (those for fibronectin binding proteins A and B, clumping factor A, gamma hemolysin, enterotoxin B, etc.) were up-regulated in cells with suboptimal expression of murF. Most importantly, the majority of these altered gene expression profiles were reversible by resupplying the optimal concentration of IPTG (isopropyl-[beta]-D-thiogalactopyranoside) to the culture. The observations suggest the coordinate regulation of a large sector of the S. aureus transcriptome in response to a disturbance in cell wall synthesis.

A study was conducted on the organization of the mecA region in methicillin-susceptible and methicillin-resistant strains of Staphylococcus sciuri. The findings indicate a low degree of sequence diversity among the mecA homologs despite the broad genetic diversity of the strains. Moreover, the results suggest that the ugpQ-like gene together with the homolog of mecA in strain K11 are evolutionary relatives and/or precursors of the genetic determinant of methicillin resistance in S aureus.

The Staphylococcus aureus femR315 gene's role in the interruption that results in reduced methicillin resistance was analyzed. The S. aureus strain COL. femR315 showed significant amino acid sequence homology with phosphoglucomutases and other similar enzymes catalyzing isomerization of hexoses and hexosamine phosphates. A staphylococcal femR315 gene can also fully complement a well-characterized glmM deficiency.

Focuses on the recruitment of the mecA gene homologue of Staphylococcus sciuri into a resistance determinant and expression of the resistant phenotype in Staphylococcus aureus. Effect of the emergence and global spread of methicillin-resistant Staphylococcus aureus; Isolation of a beta-lactam antibiotic-resistant step mutant of Staphylococcus sciuri.

Reports that the gene pbpC from Staphylococcus aureus was sequenced. Encoded penicillin-binding protein (PBP) including the transpeptidase conserved motifs SXXK, SXN and KTG; Indication of the encoding of the staphylococcal PBP 3; Generation of cells of abnormal size and shape and disoriented septa with an inactivated pbpC.

Identifies a gene cluster located on the chromosomal SmaI I fragment of a highly methicillin resistant strain of Staphylococcus aureus. Reduction of methicillin resistance in Tn551 insertional mutants; Similarities of the gene cluster to the Bacillus subtilis sig B operon; Comparison of amino acid sequences in known proteins.

Studies the complementation of the essential peptidoglycan transpeptidase function of penicillin-binding protein 2 by the drug resistance protein PBP2 in Staphylococcus aureus (SA). Effect of suppression of pbp2 transcription on growth of methicillin-resistant SA strain COL and methicillin-susceptible SA strain RN4220; Cell wall composition and morphology of SA constructs grown with and without PBP2.

The β-lactam resistance gene meca was acquired by Staphylococcus aureus from an extraspecies source. The search for the possible origin of this gene has led to the identification of a close structural homologue of meca as a native gene in the animal species Staphylococcus sciuri. Surprisingly, the overwhelming majority of S. sciuri isolates were fully susceptible to β-lactam antibiotics in spite of the ubiquitous presence of the mecA homologue in the bacteria. We now describe two unusual S. sciuri strains isolated from humans—SS-37 and SS-41—that showed resistance to methicillin associated with high rates of transcription of the mecA homologue and production of a protein resembling penicillin binding protein 2a, the gene product of S. aureus mecA. In strain SS-37 increased transcription of the mecA homologue was related to insertion of an IS256 element upstream of the structural gene, and strain SS-41 had single nucleotide alterations in the promoter region of the meca homologue which appear to be related to up-regulation of the rate of transcription. A third methicillin-resistant human isolate of S. sciuri that carries both the native meca homologue and a methicillin-resistant S. aureus (MRSA) type mecA, strain K3, was now shown to be unstable in the absence of drug selection, causing the segregation of antibiotic-susceptible cells accompanied by the loss of the MRSA type mecA. These observations illustrate the remarkable variety of strategies available to bacteria for acquiring mechanisms of drug resistance in the in vivo environment. [ABSTRACT FROM AUTHOR]