Inoculum effect of Enterobacterales co-expressing OXA-48 and CTX-M on the susceptibility to ceftazidime/avibactam and meropenem.

BACKGROUND: The treatment of infections caused by OXA-48/CTX-M-coproducing Enterobacterales may be based on new beta-lactam/beta-lactamase inhibitors, such as ceftazidime/avibactam (CZA), or on high dose of meropenem (MER). However, bacterial density at the infection site may vary widely, and the inoculum effect of such antimicrobial strategies has never been specifically investigated. To determine if CZA or MER susceptibilities are impacted by high inocula of Enterobacterales co-expressing both enzymes: OXA-48 like and CTX-M. METHODS: Determination of an inoculum effect was performed with a standard inoculum of 108 CFU/mL (0.5 McFarland) as recommended by EUCAST guidelines and compared to a twofold increase as well as a tenfold increase (1 McFarland and 5 McFarland respectively). RESULTS: Thirty-nine isolates of ceftazidime-resistant Enterobacterales were included of which 27 (70%) co-expressed OXA-48 + CTX-M-15, 6 (15%) OXA-48 + CTX-M-14, and 6 (15%) OXA-181 + CTX-M-15. The susceptibility to the CZA combination was preserved whatever the inoculum used. Regarding MER, 24 (61.5%) of the isolates were susceptible to MER with the standard inoculum, 19 (48.7%) with a twofold increase, and only 15 (38.5%) with a tenfold increase. CONCLUSION: We showed that in vitro inoculum effect was observed with meropenem but not with CZA for OXA-48- combined with CTX-M-producing Enterobacterales.

Infections caused by Tissierella praeacuta: A report of two cases and literature review.

Herein we report two cases of infections caused by Tissierella praeacuta and a review of the literature. The first case was a septic pseudarthrosis of the left femur after multiple fractures. Two per-operative samples were positive with T. praeacuta. The patient was successfully treated by piperacillin - tazobactam and metronidazole. The second case was a bacteremia in a patient suffering from pyonephrosis and a hepatic abscess. The treatment was meropenem. No relapses were observed in both cases. Identification of the strains using MALDI-TOF coupled to mass spectrometry (MS) (Beckman coulter, France) was inconclusive in the two cases. Identification by 16S rRNA sequencing was then performed. This bacterium was susceptible to beta-lactams, chloramphenicol, rifampicine and metronidazole.

Prospective evaluation of the Alere i Influenza A&B nucleic acid amplification versus Xpert Flu/RSV.

The rapid and accurate detection of influenza virus in respiratory specimens is required for optimal management of patients with acute respiratory infections. Because of the variability of the symptoms and the numerous other causes of influenza-like illness, the diagnosis of influenza cannot be made on the basis of clinical criteria alone. Thus, rapid influenza diagnostic tests have been developed such as the Alere i Influenza A&B isothermal nucleic acid assay. We prospectively evaluated the performance of the Alere i Influenza A&B assay in comparison with our routine Xpert Flu/RSV assay. Positive samples were subtyped according to the protocol from the National Influenza Center (Paris, France). A total of 96 respiratory nasal swab samples were analyzed: with both methods, 38 were positive and 56 were negative. Samples were prospectively collected from January 20 to April 8, 2015, from patient (86 adult and 10 pediatric patients) presenting with an influenza-like illness through the French influenza season. In comparison with the Xpert Flu/RSV assay, the overall sensitivity and specificity of the Alere i Influenza A&B assay were 95% and 100%, respectively. Our results indicate that the Alere i Influenza A&B assay has a good overall analytical performance and a high degree of concordance with the PCR-based Xpert Flu/RSV assay. The Alere i Influenza A&B isothermal nucleic acid amplification test is a powerful tool for influenza detection due to its high sensitivity and specificity as well as its ability to generate results within 15min.