SummaryMeningococcal gdhA , encoding the NADP-specific Lglutamate dehydrogenase (NADP-GDH), is essential for systemic infection in an infant rat model. In this paper, a limited transcriptional analysis detected differences in gdhA expression among clinical isolates. In strains expressing high levels of gdhA mRNA, two promoters, gdhA P1 and gdhA P2, initiated transcription of gdhA . In contrast, in strains expressing low mRNA levels, gdhA P2 was not active because of weak expression of gdhR , an associated regulatory gene. Gene knock-out and complementation of a gdhR -defective mutant confirmed that GdhR is a positive regulator for gdhA P2. Trans -activation of gdhA P2 was maximal in complex medium during late logarithmic growth phase and in chemical defined medium (MCDA) when glucose (MCDA-glucose) instead of lactate (MCDA-lactate) was used as a carbon source in the presence of glutamate. gdhR knockout mutants lost both growth phase and carbon source regulation, and exhibited a growth defect more severe in MCDA-glucose than in MCDA-lactate. DNAprotein interaction studies demonstrated that 2-oxoglutarate, a product of the catabolic reaction of the NADP-GDH and an intermediate of the tricarboxylic acid (TCA) cycle, inhibits binding of GdhR to gdhA P2.

bMany studies demonstrate that delayed proper therapy in bloodstream infections caused by Staphylococcus aureus increases the mortality rate, emphasizing the need to shorten the turnaround time for positive blood cultures. Different techniques are currently available, from phenotypic methods to more complex tests such as matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF), real-time PCR (RT-PCR), and fluorescence in situ hybridization using peptide nucleic acid probes (PNA FISH). This study evaluated the performance of the Staphylococcus QuickFISH BC test (QFT), a novel FISH methodology, compared with the direct tube coagulase test (DTCT) on blood cultures exhibiting Gram-positive cocci in clusters. A total of 173 blood cultures collected from 128 different patients were analyzed using the DTCT, evaluated after both 4 and 24 h, and the QFT. A total of 179 isolates were identified using the Vitek2 system. Thirty-five out of 35 Staphylococcus aureus were correctly identified by the QFT (sensitivity ‫؍‬ 100%), with a specificity of 100% (no green fluorescence was detected for strains different from S. aureus). The DTCT was positive after 4 h for 28 out of the 35 samples (sensitivity ‫؍‬ 80%) and after 24 h for 31 out of the 35 samples (sensitivity ‫؍‬ 88.57%). Among the remaining 144 isolates, one was then identified as Corynebacterium striatum and two as Micrococcus luteus. QFT identified 139 out of the 141 coagulase-negative staphylococci (CoNS) (sensitivity ‫؍‬ 98.58%), showing again a specificity of 100% (no fluorescent red signals were detected for strains different from CoNS). We also discuss also the implementation process of this methodology in our setting, with particular emphasis on the workflow and the cost-effectiveness.

Neisseria meningitidis strains belonging to the hypervirulent lineage ET-37 and several unrelated strains are extremely UV sensitive. The phenotype is consequent to the presence of a nonfunctional recB ET-37 allele carrying multiple missense mutations. Phenotypic analysis has been performed with congenic meningococcal strains harboring either the wild-type recB allele or the recB ET-37 allele. Congenic recB ET-37 meningococci, in addition to being sensitive to UV, were defective both in repair of DNA lesions induced by UV treatment and, partially, in recombination-mediated transformation. Consistently, the wild-type, but not the recB ET-37 , allele was able to complement the Escherichia coli recB21 mutation to UV resistance and proficiency in recombination. recB ET-37 meningococci did not exhibit higher frequencies of spontaneous mutation to rifampin resistance than recB-proficient strains. However, mutation rates were enhanced following UV treatment, a phenomenon not observed in the recB-proficient counterpart. Interestingly, the results of PCR-based assays demonstrated that the presence of the recB ET-37 allele considerably increased the frequency of recombination at the pilin loci. The main conclusion that can be drawn is that the presence of the defective recB ET-37 allele in N. meningitidis isolates causes an increase in genetic diversity, due to an ineffective RecBCD-dependent DNA repair and recombination pathway, and an increase in pilin antigenic variation.

Klebsiella pneumoniae is a Gram-negative, rod-shaped bacterium, responsible for hospital and community acquired pneumonia, urinary tract and wound infections, and bloodstream dissemination. K. pneumoniae infection in pregnancy, leading to acute chorioamnionitis (AC), preterm premature rupture of membranes (PPROM) and early pregnancy loss in the second trimester, has been rarely reported. Herein, we present a case of K. pneumoniae AC that caused intrauterine fetal demise (IUFD) at 19 weeks + 5 days. The 36-year-old mother was admitted at 18 weeks + 1 day of gestation for threatened abortion. IUFD occurred 11 days after. Fetal postmortem showed severe AC and funisitis, neutrophils within alveoli and intestinal lumen, associated with rod-like bacteria. Fetal blood and lung cultures grew K. pneumoniae, β-lactamase-non-producing strain. Antibiogram revealed sensitivity for piperacillin/tazobactam. Three days after IUFD, the mother presented with fever (37.8 °C) which persisted for one week. Maternal blood and urine cultures were negative. According to fetal microbiological results, available 6 days after IUFD, initial treatment with amoxicillin/clavulanic acid was replaced with piperacillin/tazobactam with full patient recovery. Therefore, in the event of PPROM and IUFD, fetal microbiological investigations should always be performed to isolate the proper etiologic agent and start the correct medical treatment.