Cephalosporin P1

Fusidane-type antibiotics are a group of triterpenoid antibiotics. They include helvolic acid, fusidic acid, and cephalosporin P1, among which fusidic acid has been used clinically. We have recently elucidated the biosynthesis of helvolic acid and fusidic acid, which share an early biosynthetic route involving six conserved enzymes. Here, we report two separate gene clusters for cephalosporin P1 biosynthesis. One consists of the six conserved genes, and the other contains three genes encoding a P450 enzyme (CepB4), an acetyltransferase (CepD2), and a short-chain dehydrogenase/reductase (CepC2). Introduction of these three genes into Aspergillus oryzae, which harbors the six conserved genes, produced cephalosporin P1. Stepwise introduction revealed that CepB4 not only catalyzes stereoselective dual oxidation of C6 and C7, but also monooxygenation of C6 or C7. This led to the generation of five new analogues. Using monohydroxylated products as substrates, we demonstrated that CepD2 specifically acetylates C6-OH, although both C6-OH and C7-OH acetylated analogues have been identified in nature.

Background: In cases of acute cholecystitis (AC), empirical antibiotics are used to prevent infectious morbidities following cholecystectomy. However, there are still no exact guidelines on which antibiotics to use. Methods: We enrolled 300 patients who had been admitted for cholecystectomy because of grade I or II AC. We randomly allocated them to one of two groups empirically: the first group was to be given first-generation cephalosporins (group I, 150 patients) and the second group was to be given second-generation cephalosporins (group II, 150 patients). We analyzed the clinical outcomes and the incidence of postoperative infectious morbidities. Results: The incidence rate of overall infectious morbidities (18 cases, 12% in group I; 17 cases, 11.3% in group II; P = .859) showed no difference between the two groups. The incidence rate of sepsis (only one case, 0.7% in group II, P = 1.000) or surgical site infection (nine cases, 6% in group I and eight cases, 5.3% in group II, P = 1.000) were also similar in both groups. Conclusions: The empirical use of first-generation cephalosporins for mild-to-moderate AC without gallbladder perforation was not inferior to using second-generation cephalosporin for prophylaxis against postoperative infection. Our results could allow for a tailored treatment strategy of empirical antibiotics according to the severity of the cholecystitis.

Antibiotic resistance is rapidly spreading via the horizontal transfer of resistance genes in mobile genetic elements. While plasmids are key drivers of this process, few integrative phages encode antibiotic resistance genes. Here, we find that phage-plasmids, elements that are both phages and plasmids, often carry antibiotic resistance genes. We found 60 phage-plasmids with 184 antibiotic resistance genes, providing resistance for broad-spectrum-cephalosporins, carbapenems, aminoglycosides, fluoroquinolones, and colistin. These genes are in a few hot spots, seem to have been cotranslocated with transposable elements, and are often in class I integrons, which had not been previously found in phages. We tried to induce six phage-plasmids with resistance genes (including four with resistance integrons) and succeeded in five cases. Other phage-plasmids and integrative prophages were coinduced in these experiments. As a proof of concept, we focused on a P1-like element encoding an extended spectrum β-lactamase, blaCTX-M-55. After induction, we confirmed that it is capable of infecting and converting four other E. coli strains. Its reinduction led to the further conversion of a sensitive strain, confirming that it is a fully functional phage. This study shows that phage-plasmids carry a large diversity of clinically relevant antibiotic resistance genes that they can transfer across bacteria. As plasmids, these elements seem plastic and capable of acquiring genes from other plasmids. As phages, they may provide novel paths of transfer for resistance genes because they can infect bacteria that are distant in time and space from the original host. As a matter of alarm, they may also mediate transfer to other types of phages. IMPORTANCE The dissemination of antimicrobial resistance is a major threat to global health. Here, we show that a group of temperate bacterial viruses (phages), termed phage-plasmids, commonly encode different and multiple types of resistance genes of high clinical importance, often in integrons. This is unexpected, as phages typically do not carry resistance genes and, hence, do not confer upon their hosts resistance via infection and genome integration. Our experiments with phage-plasmids isolated from clinical settings confirmed that they infect sensitive strains and render them antibiotic resistant. The spread of antibiotic resistance genes by phage-plasmids is worrisome because it dispenses cell-to-cell contact, which is necessary for canonical plasmid transfer (conjugation). Furthermore, their integrons become genetic platforms for the acquisition of novel resistance genes.