NADP-Dependent Aldehyde Dehydrogenase from Archaeon Pyrobaculum sp.1860

We present the functional and structural characterization of the first archaeal thermostable NADP-dependent aldehyde dehydrogenase AlDHPyr1147. In vitro, AlDHPyr1147 catalyzes the irreversible oxidation of short aliphatic aldehydes at 60–85°С, and the affinity of AlDHPyr1147 to the NADP+ at 60°С is comparable to that for mesophilic analogues at 25°С. We determined the structures of the apo form of AlDHPyr1147 (3.04 Å resolution), three binary complexes with the coenzyme (1.90, 2.06, and 2.19 Å), and the ternary complex with the coenzyme and isobutyraldehyde as a substrate (2.66 Å). The nicotinamide moiety of the coenzyme is disordered in two binary complexes, while it is ordered in the ternary complex, as well as in the binary complex obtained after additional soaking with the substrate. AlDHPyr1147 structures demonstrate the strengthening of the dimeric contact (as compared with the analogues) and the concerted conformational flexibility of catalytic Cys287 and Glu253, as well as Leu254 and the nicotinamide moiety of the coenzyme. A comparison of the active sites of AlDHPyr1147 and dehydrogenases characterized earlier suggests that proton relay systems, which were previously proposed for dehydrogenases of this family, are blocked in AlDHPyr1147, and the proton release in the latter can occur through the substrate channel

SEROTYPES AND ANTIMICROBIAL SUSCEPTIBILITY OF NASOPHARYNGEAL PNEUMOCOCCI ISOLATED FROM CHILDREN IN 2010–2016: A RETROSPECTIVE COHORT STUDY

Background. Pneumococci (Streptococcus pneumoniae) represent major pathogens that cause acute infections in children. Objective. Our aim was to analyze dynamics of the distribution of nasopharyngeal pneumococcal serotypes and their antimicrobial susceptibility in children. Methods. A retrospective cohort study was conducted. We examined nasopharyngeal pneumococci isolated from children getting care at the National Medical Research Center of Children’s Health (Moscow) in 2010–2016. Serotyping was performed using specific antisera and/or by molecular typing employing PCR. Susceptibility to oxacillin (OXA), erythromycin (ERY), clindamycin (CLI), trimethoprim/sulfamethoxazol, chloramphenicol and tetracycline was tested by the disk diffusion method. In 2013–2016, penicillin (PEN), amoxicillin (AMX), ERY and CLI minimal inhibitory concentrations (MIC) were measured. Results. A total of 1,111 pneumococcal isolates were examined; the sample was obtained from children with a median age of 4 years (P25–P75, 2.4–6.5 years). We identified 48 pneumococcal serotypes; six leading serotypes were serotypes 3, 6А, 6В, 14, 19F and 23F aggregating a proportion of 63.2% in the overall distribution. From 2010 to 2016, the distribution of serotypes has not changed. Wherein, 13-valent pneumococcal conjugate vaccine covered 74% of serotypes in children under 5 years. The five leading serotypes (6А, 6В, 14, 19F, 23F and serotype 19A) had the highest resistance rate. Within 2010–2016, the proportion of OXA- and ERY-resistant pneumococci grew from 21.3% to 35.9% and from 24.5% to 36.9%, respectively. The majority (81.3%) of ERY-resistant isolates possessed an MLSB-phenotype, i. e. were resistant to macrolides, lincosamides, and streptogramin B. In 2013–2016, the rate of PEN- and AMX-resistant pneumococci was 34.6% and 3.5%, respectively. Conclusion. Within the seven year study period, no major shifts in the nasopharyngeal pneumococcal serotype distribution were observed. The pneumococci remained highly susceptible to AMX, but activity of macrolides was significantly reduced. Considering the leading mechanism of macrolide resistance, the use of any macrolides or lincosamides for empiric treatment of pneumococcal infections in children is questionable