Carbapenems such as imipenem are extended-spectrum β-lactam antibiotics, which are not hydrolyzed by the β-lactamases commonly found in Enterobacteriaceae. Here we report a gene encoding a ...carbapenemase, which was cloned from the chromosome of a clinical isolate of Enterobacter cloacae, strain NOR-1, into pACYC184 plasmid in Escherichia coli. Unlike all the sequenced carbapenemases, which are class B metallo-β-lactamases, the mature protein (NmcA) is a class A serine β-lactamase. NmcA shares the highest amino acid identity (50%) with the extended-spectrum class A β-lactamase MEN-1 from E. coli. In the opposite orientation from the nmcA promoter, an overlapping and divergent promoter was detected, along with an open reading frame, which encoded a 33.5-kDa protein (NmcR). The NmcR amino acid sequence displays homology with LysR-type transcriptional regulatory proteins, including the conserved residues near its N terminus within a helix-turn-helix motif. Deletion of nmcR resulted in decreased carbapenem resistance and a loss of β-lactamase inducibility, demonstrating a positive role of NmcR in NmcA expression.
Over a three-month period, 13 neonates developed staphylococcal scalded skin syndrome (SSSS) in a maternity unit, between four and 18 days after their birth. An epidemiological and descriptive study ...followed by a case-control study was performed. A case was defined as a neonate with blistering or peeling skin, and exfoliative toxin A Staphylococcus aureus positive cultures. Controls were selected at random from the asymptomatic, non-colonized neonates born on the same day as the cases. All staff members and all neonates born during the outbreak period were screened for carriage by nasal swabs and umbilical swabs, respectively. S. aureus isolates were polymerase chain reaction (PCR) screened for etA gene and genotyped by pulsed-field gel electrophoresis (PFGE). Two clusters of eight and five cases were identified. Receiving more than one early umbilical care procedure by the same ancillary nurse was the only risk factor identified in the case-control study (odds ratio=15, 95% confidence intervals 2–328). The ancillary nurse suffered from chronic dermatitis on her hands that favoured S. aureus carriage. Exfoliative-toxin-A-producing strains, as evidenced by PCR and indistinguishable by PFGE, were isolated from all but one of the SSSS cases, from four asymptomatic neonates, from two staff members and from the ancillary nurse's hands. Removal of the ancillary nurse from duty, infection control measures (isolation precautions, chlorhexidine handwashing and barrier protections), and treatment of the carriers (nasal mupirocin and chlorhexidine showers) led to control of the epidemic. In conclusion, this study emphasizes the need for tight surveillance of chronic dermatitis in healthcare workers.
Carbapenem-resistant Acinetobacter baumannii (CR-Ab) ranked third, with a frequency of 24.8%, among 202 strains of multidrug-resistant bacteria isolated from clinical samples in the main hospital of ...New Caledonia in 2004. All CR-Ab isolates were analysed by isoelectric focusing, conjugation, pulsed-field gel electrophoresis and PCR for the presence of carbapenemase genes. Fifty CR-Ab isolates produced carbapenemase OXA-23. The isolates belonged to a single clone presenting several subtypes, suggesting an endemic situation. This study further illustrates the widespread prevalence of carbapenemase OXA-23-producing CR-Ab isolates in the South Pacific.
Synonymous mutations within exons may cause aberrant splicing by disrupting exonic splicing enhancer (ESE) motifs in the vicinity of non consensus splice sites. Mutational analysis of
PDHA1 revealed ...only one silent single nucleotide substitution in exon 5 in two unrelated boys and a girl (c.483C>T and c.498C>T variants, respectively). For both patients, pyruvate dehydrogenase complex activity was low and the immunoreactive E1alpha protein was defective in cultured fibroblasts.
One of the boys was a somatic mosaic for the c.483C>T variant, as shown by the variable ratio of mutant to normal alleles in fibroblast, lymphocyte and single hair root DNA. Transcript analysis in fibroblasts from the three patients revealed the presence of both normal and truncated cDNAs, with the splicing out of exon 5 predicted to result in a frame shift and premature termination (p.Arg141AlafsX11). The treatment of fibroblasts with emetine before harvesting to prevent nonsense mRNA-mediated decay increased the amount of mutant mRNA.
In silico analysis revealed that each variant disrupted a putative SRp55 binding site and that the intron 5 donor splice site (5′ss) contained a weak splicing signal. Transient transfection of COS-7 or Hela cells with hybrid minigene constructs containing wild-type or mutant
PDHA1 exon 5, followed by RT-PCR demonstrated that each variant resulted in the incomplete inclusion of
PDHA1 exon 5, and that this defect was corrected following the restoration of a perfect consensus sequence for the 5′ splice site by site-directed mutagenesis.
These two synonymous mutations expand the spectrum of rare
PDHA1 splicing mutations, all of which are located in non canonical splice sites.
International adoption from developing countries has become an increasing phenomenon in recent years. Given the high prevalence of multidrug-resistant (MDR) bacteria in these countries, the adopted ...children represent a group at risk for both carriage and infection with MDR bacteria. The dynamics of intrafamilial transmission of MDR bacteria after adoption was studied in a prospective study from January 2002 to January 2005. Stool samples, taken at the first visit to the outpatient adoption practice and subsequently every month, from the adopted children of an orphanage of Bamako (Mali) and from all the members of their adoptive families were screened for MDR bacteria and bacterial pathogens. Bacteria were characterized by standard biochemical methods, disc diffusion antibiograms, PFGE and plasmid analysis. β-Lactamase genes were sought by PCR. Over the study period, 52 ESBL-producing Enterobacteriaceae (E-ESBL), with Escherichia coli (56%) being the most prevalent, were isolated from 24/25 adoptees at arrival in France. During follow-up, the transmission of ESBL-producing E. coli and Salmonella enterica Babelsberg between the adoptees and their adoptive family members has clearly been demonstrated for 5/22 families (23%). The mean duration of the carriage for the adopted children was 9 months (1-15 months). CTX-M-15 was the most prevalent resistance gene among the E-ESBLs (93%), while SHV-12 was found among the S. enterica Babelsberg studied. International travellers, transfer of patients and now adoption may contribute to the global emergence of MDR bacteria. Thus, in addition to the usual screening of adopted children for infectious diseases, additional screening for MDR bacteria should be recommended, at least for children coming from countries with a high prevalence of MDR bacteria.
A clinical isolate of Proteus mirabilis Lil-1 was obtained from a Vietnamese patient hospitalized in Paris, France. This isolate was resistant to cephalosporins, and there was marked synergy between ...cephalosporins and clavulanic acid together with unusual synergy between cefoxitin and cefuroxime. PCR analysis revealed the presence of blaVEB-1, an integron-located gene coding for an extended-spectrum β-lactamase (ESBL) identified previously in an Escherichia coli isolate MG-1 from Vietnam. Using class 1 integron primers and blaVEB-1 intragenic primers, the insert region of the blaVEB-1-containing integron along with flanking sequences were amplified from P. mirabilis Lil-1 whole-cell DNA. A novel class 1 integron, In55, was identified that contained, in addition to intI1, qacEΔ1, sul1 and Orf5 genes, an 8 kb variable region. This region was comparable in size to that found previously in E. coli MG-1, but different from those previously identified in two Pseudomonas aeruginosa isolates from Thailand. In55 was located on a 190 kb self-transferable plasmid, which was different in size and structure from that found in E. coli MG-1. The finding of blaVEB-1 on different plasmids and integrons in enterobacterial isolates underlines the interspecies spread of this novel ESBL gene.
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