Likely False-Positive Pneumococcal Antigen Test BinaxNOW Due to Parvimonas micra: A Four-Case Series.

We retrospectively report four cases from two hospitals of nonpneumococcal pleural empyema with a likely false-positive result on the pneumococcal antigen test BinaxNOW (PATB) (Alere) performed in pleural fluid samples in patients with aspiration pneumonia risk factors. To determine whether the positive reaction was due to cross-reactivity, we separately tested the isolates from the pleural fluid samples, along with collection and reference strains. All patients had polymicrobial aerobic and anaerobic positive cultures, including Parvimonas micra in every case. In all cases, 16S rDNA polymerase chain reaction sequencing yielded Fusobacterium nucleatum. Samples for culture and specific polymerase chain reaction were negative for Streptococcus pneumoniae. We found that the false-positive PATB finding was likely due to P micra, a previously unknown cross-reactivity. In case of aspiration pneumonia risk factors, a positive PATB result must be interpreted with caution because there can be a false positivity due to anaerobic infection or co-infection.

Susceptibility of enterohaemorrhagic Escherichia coli to azithromycin in France and analysis of resistance mechanisms.

OBJECTIVES: Antibiotic therapy is not recommended during enterohaemorrhagic Escherichia coli (EHEC) infection. However, the potential benefit of azithromycin has recently been described. This study was conducted to evaluate the macrolide susceptibility of EHEC isolates from France and to analyse the mechanisms of resistance to azithromycin in EHEC. METHODS: Strains from patients with EHEC infections were collected by the associated French National Reference Laboratory for E. coli from 2004 to 2014. Antimicrobial susceptibility testing was performed by disc diffusion and Etest methods. For strains presenting macrolide resistance, antibiotic resistance genes were searched for by PCR. Genetic transfer was performed by conjugation and plasmid analysis was done by Southern-blot hybridization after PFGE. RESULTS: We tested 508 isolates of EHEC. Azithromycin MICs ranged between 0.25 and 16 mg/L (median = 3 mg/L), except for two atypical strains, 34396 and 36493, for which MICs were >256 mg/L. Plasmid transferability of macrolide resistance was demonstrated. Strain 34396, of serotype O106:H18, harboured two macrolide resistance genes [mph(A) and erm(B)] and two other antimicrobial resistance genes (blaDHA-1 for ß-lactam resistance and qnrB4 for quinolone resistance). mph(A), blaDHA-1 and qnrB4 were localized on the same plasmid. Strain 36493 belonging to the highly virulent O26:H11 EHEC clonal group harboured a plasmid containing mph(A). CONCLUSIONS: For the first time we describe plasmid-borne macrolide resistance genes in EHEC strains. Dissemination of such plasmids may threaten the potential benefit of azithromycin during the management of patients infected or colonized with EHEC. Determination of azithromycin MICs should be considered prior to its therapeutic use and 16 mg/L may be used as the epidemiological cut-off value.

Genome Analysis of Kingella kingae Strain KWG1 Reveals How a ß-Lactamase Gene Inserted in the Chromosome of This Species.

We describe the genome of a penicillinase-producing Kingella kingae strain (KWG1), the first to be isolated in continental Europe, whose bla(TEM-1) gene was, for the first time in this species, found to be chromosomally inserted. The bla(TEM) gene is located in an integrative and conjugative element (ICE) inserted in Met-tRNA and comprising genes that encode resistance to sulfonamides, streptomycin, and tetracycline. This ICE is homologous to resistance-conferring plasmids of K. kingae and other Gram-negative bacteria.

First identification of a chromosomally located penicillinase gene in Kingella kingae species isolated in continental Europe.

Kingella kingae is the major pathogen causing osteoarticular infections (OAI) in young children in numerous countries. Plasmid-borne TEM-1 penicillinase production has been sporadically detected in a few countries but not in continental Europe, despite a high prevalence of K. kingae infections. We describe here for the first time a K. kingae ß-lactamase-producing strain in continental Europe and demonstrate the novel chromosomal location of the blaTEM-1 gene in K. kingae species.

Xpert GBS assay for rapid detection of group B streptococcus in gastric fluid samples from newborns.

The Xpert GBS real-time PCR assay was applied to gastric fluid samples from 143 newborns, and it detected group B streptococcus (GBS) within 1 h for 16 (11.2%) cases, while microscopic examination detected only 2 cases. The sensitivity and specificity of the Xpert GBS were 80% and 100%, respectively, with regard to 20 cases of GBS colonization or infection. Concordance of Xpert GBS results versus culture was 92.3%. This test detects in a timely manner newborns at risk for invasive GBS disease.

Evaluation of the ßLacta test, a rapid test detecting resistance to third-generation cephalosporins in clinical strains of Enterobacteriaceae.

For decades, third-generation cephalosporins (3GC) have been major drugs used to treat infections due to Enterobacteriaceae; growing resistance to these antibiotics makes the rapid detection of such resistance important. The ßLacta test is a chromogenic test developed for detecting 3GC-resistant isolates from cultures on solid media within 15 min. A multicenter prospective study conducted in 5 French and Belgian hospitals evaluated the performance of this test on clinical isolates. Based on antibiotic susceptibility testing, strains resistant or intermediate to cefotaxime or ceftazidime were classified as 3GC resistant, and molecular characterization of this resistance was performed. The rates of 3GC resistance were 13.9% (332/2,387) globally, 9.4% in Escherichia coli (132/1,403), 25.6% in Klebsiella pneumoniae (84/328), 30.3% in species naturally producing inducible AmpC beta-lactamases (109/360), and 5.6% in Klebsiella oxytoca and Citrobacter koseri (7/124). The sensitivities and specificities of the ßLacta test were, respectively, 87.7% and 99.6% overall, 96% and 100% for E. coli and K. pneumoniae, and 67.4% and 99.6% for species naturally producing inducible AmpC beta-lactamase. False-negative results were mainly related to 3GC-resistant strains producing AmpC beta-lactamase. Interestingly, the test was positive for all 3GC-resistant extended-spectrum beta-lactamase-producing isolates (n = 241). The positive predictive value was 97% and remained at ≥96% for prevalences of 3GC resistance ranging between 10 and 30%. The negative predictive values were 99% for E. coli and K. pneumoniae and 89% for the species producing inducible AmpC beta-lactamase. In conclusion, the ßLacta test was found to be easy to use and efficient for the prediction of resistance to third-generation cephalosporins, particularly in extended-spectrum beta-lactamase-producing strains.

Functional amyloid formation within mammalian tissue.

Amyloid is a generally insoluble, fibrous cross-beta sheet protein aggregate. The process of amyloidogenesis is associated with a variety of neurodegenerative diseases including Alzheimer, Parkinson, and Huntington disease. We report the discovery of an unprecedented functional mammalian amyloid structure generated by the protein Pmel17. This discovery demonstrates that amyloid is a fundamental nonpathological protein fold utilized by organisms from bacteria to humans. We have found that Pmel17 amyloid templates and accelerates the covalent polymerization of reactive small molecules into melanin-a critically important biopolymer that protects against a broad range of cytotoxic insults including UV and oxidative damage. Pmel17 amyloid also appears to play a role in mitigating the toxicity associated with melanin formation by sequestering and minimizing diffusion of highly reactive, toxic melanin precursors out of the melanosome. Intracellular Pmel17 amyloidogenesis is carefully orchestrated by the secretory pathway, utilizing membrane sequestration and proteolytic steps to protect the cell from amyloid and amyloidogenic intermediates that can be toxic. While functional and pathological amyloid share similar structural features, critical differences in packaging and kinetics of assembly enable the usage of Pmel17 amyloid for normal function. The discovery of native Pmel17 amyloid in mammals provides key insight into the molecular basis of both melanin formation and amyloid pathology, and demonstrates that native amyloid (amyloidin) may be an ancient, evolutionarily conserved protein quaternary structure underpinning diverse pathways contributing to normal cell and tissue physiology.