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.

Emergence of Ceftriaxone Resistance during a Case of Pneumococcal Meningitis with Fatal Evolution.

We report a case of a 62-year-old man treated for Streptococcus pneumoniae meningitis by ceftriaxone and dexamethasone. After neurological improvement, neurological degradation by vasculitis occurred, despite effective concentrations of ceftriaxone in the serum and cerebrospinal fluid (CSF). S. pneumoniae with increased MICs to third-generation-cephalosporins (3GC) was isolated from the ventricular fluid 10 days after the isolation of the first strain. Isolate analysis showed that a mutation in the penicillin-binding protein 2X (PBP2X) has occurred under treatment.

Implementation of Alere i Influenza A & B point of care test for the diagnosis of influenza in an ED.

STUDY OBJECTIVE: This study aimed to evaluate the impact of implementing rapid point-of-care testing (POCT) with the Alere i Influenza A & B in an emergency department (ED) during an influenza epidemic. METHODS: Direct nasal swabs were prospectively collected following the physical examination of patients aged >18years who presented to the ED of a tertiary hospital in France with influenza-like illness (ILI) symptoms (N=301) between February 1st and March 31st, 2016, which coincided with an influenza epidemic. Laboratory-based testing (standard of care) was used to obtain a diagnosis in February 2016 (pre-POCT cohort) and positive results were confirmed using polymerase chain reaction. The primary endpoint was patient time in the ED. RESULTS: A total of 169 and 132 patients participated in the pre-POCT phase and POCT phase respectively. A significantly higher proportion of patients received a positive diagnosis in the POCT cohort compared with the pre-POCT cohort (31% versus 5.3%, P<0.01). Mean time spent in the ED and hospitalization rate were significantly lower in the POCT cohort (6.06h versus 4.15h, P=0.03, and 44.4% versus 9.7%, P=0.02, respectively). Despite similar rates in the prescription of antibiotics and antiviral therapies, the proportion of patients who were referred for additional tests was significantly lower in the POCT cohort (78.1% versus 62.1%, P=0.003, and 80.5% versus 63.6%, P=0.01, respectively). CONCLUSIONS: The Alere i Influenza A & B POCT reduced the length of stay in ED, the hospitalization rates, and the number of additional diagnostic tests compared with standard of care testing.

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.

Infective endocarditis: Clinical presentation, etiology, and early predictors of in-hospital case fatality.

OBJECTIVE: We aimed to assess the clinical presentation, microbial etiology and outcome of patients presenting with infective endocarditis (IE). PATIENTS AND METHODS: We conducted a four-year retrospective study including all patients presenting with IE. RESULTS: We included 121 patients in the study. The median age was 74.8years. Most patients had native valve IE (57%). Staphylococcus aureus accounted for 24.8% of all IE. Surgery was indicated for 70 patients (57.9%) but actually performed in only 55 (44.7%). Factors associated with surgery were younger age (P=0.002) and prosthetic valve IE (P=0.001). Risk factors associated with in-hospital mortality were diabetes mellitus (OR=3.17), chronic renal insufficiency (OR=6.62), and surgical indication (OR=3.49). Mortality of patients who underwent surgery was one sixth of that of patients with surgical indication who did not have the surgery (P<0.001).

[Shoulder arthritis due to Haemophilus aphrophilus]. / Arthrite d'épaule à Haemophilus aphrophilus.

We report a case of shoulder arthritis due to Haemophilus aphrophilus. The patient, a 56 year-old woman, was immunocompetent. She presented with a septic arthritis of the left shoulder without portal of entry. A synovial fluid sample was cultured and positive for a gram-negative bacillus after 8 days. It was identified as Haemophilus aphrophilus, in the HACCEK group, by PCR ARN 16S. We did not find any associated endocarditis. The patient recovered. As far as we know, this is only the 5th reported case of arthritis due to this microorganism.

[Resistance to antibiotics caused by decrease of the permeability in gram-negative bacteria]. / Résistance aux antibiotiques par diminution de la perméabilité chez les bactéries à gram négatif.

Due to their outer membrane, Gram negative bacteria are the only germs which can resist antibiotics by a mechanism of reduced permeability. This outer hydrophobic membrane allows hydrophilic molecules to pass only through its aqueous pores. The transmembrane pores have a trimere structure with a monomere component acting as an aqueous channel. Mean pore diameter is 1 to 1.2 nm. Changes in the absolute number of pores or in qualitative function reduce the diffusion of antibiotics entering the cell. This mechanism of reduced permeability can lead to cross resistance to several families of antibiotics. It is difficult to determine the clinical incidence since such resistances are not always detected. The species most often involved are enterobacteria including Klebsiella, Enterobacter, Serratia and Salmonella. For Pseudomonas aeruginosa, resistance to imipenem by reduced permeability results from a deficit in protein D2 and concerns 12 to 15% of the strains identified in French Hospitals. Reduced permeability is particularly effective when associated with another mechanism of resistance allowing the bacteria to express a higher level of resistance.

[Detection of nasal colonization methicillin-resistant Staphylococcus aureus: a prospective study comparing real-time genic amplification assay vs selective chromogenic media]. / Détection de la colonisation nasale de Staphylococcus aureus résistant à la méthicilline : étude prospective comparant l'amplification génique temps réel vs les milieux chromogènes sélectifs.

UNLABELLED: In contrast to "classical" genic amplification, real-time genic amplification can be performed in every laboratory without the need of sophisticated isolation procedures. Moreover, real-time genic amplification allows an early detection of meticillin resistant Staphylococcus aureus colonization, 2 hours compared to 1 or 2 days for culture. OBJECTIVE: In order to assess the feasibility on Smartcycler of the IDI-MRSA real-time genic amplification assay in comparison with chromogenic media. METHODS: A prospective study has been initiated in July 2004: nasal swabs were taken from patients entering the ICU, vascular surgery, diabetology and geriatry wards. During a 4 months period, 682 specimens have been obtained from 508 patients. RESULTS: Sixty-four (9.3%) patients were positive by genic amplification and selective agar culture (CHROMagar MRSA, MRSASelect and/or ORSAB), 19 (2.9%) were positive by genic amplification only (3 of these patients were under antibiotic treatment); 572 specimens remained negative by both methods. The sensitivity and specificity of this assay were 100% and 96% respectively with a positive predictive value of 70% and negative predictive value of 100%. Initially 82 nasal specimens were unresolved (12%). 38 were resolved following a freeze-thaw cycle. Thus, 44 (6.4%) were unresolved specimens. Comparison between CHROMagar MRSA and MRSASelect showed a good correlation for the detection at 24 hours (5.5% and 5.6% respectively). These two chromogenic media allowed a much better detection of MRSA than ORSAB medium within 24H. CONCLUSION: The results obtained by the early real-time genic amplification for the detection of meticillin resistant Staphylococcus aureus are promising. Despite 6.4% amplification failure, we consider that IDI-MRSA real-time genic amplification assay represents a significant breakthrough in the detection of colonization.

A novel, double mutation in DNA gyrase A of Escherichia coli conferring resistance to quinolone antibiotics.

A spontaneous Escherichia coli mutant, named Q3, resistant to nalidixic acid was obtained from a previously described clinical isolate of E. coli, Q2, resistant to fluoroquinolones but susceptible to nalidixic acid (E. Cambau, F. Bordon, E. Collatz, and L. Gutmann, Antimicrob. Agents Chemother. 37:1247-1252, 1993). Q3 harbored the mutation Asp82Gly in addition to the Gly81Asp mutation of Q2. The different mutations leading to Gly81Asp, Asp82Gly, and Gly81AspAsp82Gly were introduced into the gyrA gene harbored on plasmid pJSW102, and the resulting plasmids were introduced into E. coli KNK453 (gyrAts) by transformation. The presence of Asp82Gly or Gly81Asp alone led to a low-level resistance to fluoroquinolones but not to nalidixic acid resistance. When both mutations were present, resistance to both nalidixic acid and fluoroquinolones was expressed. Purified gyrases of the different mutants showed similar rates of supercoiling. Dominance of the various gyrA mutant alleles harbored on plasmids was examined. The susceptibility to quinolones associated with wild-type gyrA was always dominant. The susceptibility to nalidixic acid expressed by the Gly81Asp mutant was dominant, while that expressed by the Asp82Gly mutant was recessive. From these results, we hypothesize that some amino acids within the quinolone resistance-determining region of gyrase A are more important for the association of subunits rather than for the activity of the holoenzyme.