The present report describes a very rare case of an aortic homograft valve endocarditis caused by Cardiobacterium hominis. The case was complicated by an agranulocytosis after 3 weeks of antibiotic treatment induced by ceftriaxone. Alternative oral treatment with ciprofloxacin and rifampicin was successful, no surgical intervention was needed and homograft function could be preserved.
Antibiotics targeting the bacterial ribosome typically bind to highly conserved rRNA regions with only minor phylogenetic sequence variations. It is unclear whether these sequence variations affect antibiotic susceptibility or resistance development. To address this question, we have investigated the drug binding pockets of aminoglycosides and macrolides/ketolides. The binding site of aminoglycosides is located within helix 44 of the 16S rRNA (A site); macrolides/ketolides bind to domain V of the 23S rRNA (peptidyltransferase center). We have used mutagenesis of rRNA sequences in Mycobacterium smegmatis ribosomes to reconstruct the different bacterial drug binding sites and to study the effects of rRNA sequence variations on drug activity. Our results provide a rationale for differences in species-specific drug susceptibility patterns and species-specific resistance phenotypes associated with mutational alterations in the drug binding pocket.The bacterial ribosome is a target for many antibacterial agents that interfere with protein synthesis, such as aminoglycosides, macrolides, ketolides, oxazolidinones, and lincosamides (23). These compounds target different steps in translation, including decoding, peptide bond formation, and translocation (33,37,40). While different classes of antibiotics bind to different ribosomal regions and interfere with different steps in translation, they all interact directly with rRNA nucleotides at or near functionally important sites (38, 39). These rRNA residues typically show high phylogenetic sequence conservation within bacteria. It is largely unclear whether the minor sequence variations present in the bacterial drug binding sites affect antibiotic susceptibility and/or resistance development.Structures of antibiotics bound to the ribosome have been resolved primarily with extremophiles such as Thermus thermophilus, Deinococcus radiodurans, or Haloarcula morismortui (2, 9, 30). Most genetic data, however, have been generated with Escherichia coli and Mycobacterium smegmatis (4-6, 10, 14, 15, 20-22, 26, 28, 29, 32). It has still to be established whether the conclusions drawn from diverse model organisms hold true for other bacterial clades as well. To address this question, we investigated rRNA alterations corresponding to phylogenetic sequence variations that are found in bacteria and which are located in two major drug binding sites, the 23S rRNA peptidyltransferase region and the 16S rRNA-decoding region. These two regions are targeted by different classes of antibiotic compounds: macrolides/ketolides (23S rRNA) and aminoglycosides (16S rRNA) (23, 37).Macrolide/ketolide antibiotics are a diverse class of naturally occurring and synthetic compounds based on a polyketide macrolactone ring substituted with one or more nonnitrogenous and/or amino sugar moieties (27). These compounds exert their inhibitory effect on protein synthesis by binding to the opening of the ribosomal polypeptide exit tunnel to obstruct elongation of the nascent polypeptide chain (30, 34). Aminoglycos...
Ureaplasma species are usually associated with infection of the urogenital tract. An unusual case of a sternal wound infection caused by Ureaplasma urealyticum in a 41-year-old male after aortic valve replacement is described.
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