QMAC-dRAST for the direct testing of antibiotic susceptibility for Enterobacterales in positive blood-culture broth: a comparison of the performances with the MicroScan system and direct disc diffusion testing methods.

OBJECTIVES: To evaluate the performances of the QMAC-dRAST GN (Gram-negative) kit for rapid antimicrobial sensitivity testing (AST) and two other methods, directly on positive blood-culture broth (PBCB), by comparison with a reference method: the MicroScan method based on broth microdilution on colonies isolated on PBCB subculture. METHODS: In total, 156 samples were collected prospectively from blood cultures positive for a Gram-negative rod. Each sample was tested with four AST techniques: (i) the QMAC dRAST GN kit, (ii) the disc diffusion (DD) method, (iii) the MicroScan method applied directly to PBCB; and (iv) MicroScan with isolates from PBCB subculture, as a reference. RESULTS: For 124 PBCB containing Enterobacterales, overall essential agreement (EA) and categorical agreement (CA) between the QMAC-dRAST on PBCB and the reference reached 95.7% and 93.5%, respectively. There were 3.0% very major errors (VME), 4.0% major errors (ME) and 2.8% minor errors (mE). A comparison of MicroScan on PBCB and the reference yielded 98.8% EA, 98.5% CA, and rates of 0.6% VME, 0.9% ME and 0.7% mE. The DD method on PBCB gave a CA of 95.8% and rates of 1.7% for VME, 2.0% for ME and 1.9% for mE. Results were obtained more rapidly for QMAC-dRAST (median of 6 h 37 min versus 18 h for the MicroScan and DD methods on PBCB). CONCLUSIONS: The QMAC-dRAST system provided rapid results well correlated with the reference method on PBCB containing Enterobacterales. Given the shorter time-to-results, the QMAC-dRAST system constitutes a fast and reliable alternative to conventional AST methods.

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.

Brucella suis biovar 2 infection in humans in France: emerging infection or better recognition?

Brucellosis is usually acquired by humans through contact with infected animals or the consumption of raw milk from infected ruminants. Brucella suis biovar 2 (BSB2) is mainly encountered in hares and wild boars (Sus scrofa), and is known to have very low pathogenicity to humans with only two case reports published in the literature. Human cases of brucellosis caused by BSB2 were identified through the national mandatory notification of brucellosis. The identification of the bacterium species and biovar were confirmed by the national reference laboratory. Epidemiological data were obtained during medical follow-up visits. Seven human cases were identified between 2004 and 2016, all confirmed by the isolation of BSB2 in clinical specimens. All patients had direct contact with wild boars while hunting or preparing wild boar meat for consumption. Five patients had chronic medical conditions possibly responsible for an increased risk of infection. Our findings suggest that BSB2 might be an emerging pathogen in hunters with massive exposure through the dressing of wild boar carcasses. Hunters, especially those with chronic medical conditions, should be informed about the risk of BSB2 infection and should receive information on protective measures.

Retrospective analysis of nocardiosis in a general hospital from 1998 to 2017.

OBJECTIVES: To describe the epidemiological, clinical, microbiological, and therapeutic characteristics of Nocardiosis patients treated in a general hospital. PATIENTS AND METHODS: Monocentric retrospective analysis of patients presenting with Nocardia-positive biological sample from January 1, 1998 to May 1, 2017. RESULTS: We identified nine cases of Nocardia infections. Risk factors were oral corticosteroid therapy (n=3), solid cancer (n=2), hematological cancer (n=1), COPD (n=1). No risk factor was identified in patients with isolated cutaneous presentation (n=2). Disseminated presentations (n=3) were observed in patients receiving corticosteroid therapy (n=2) and presenting with ENT cancer (n=1). Identified Nocardia species were Nocardia nova (n=4), Nocardia cyriacigeorgica (n=2), Nocardia abscessus (n=1), Nocardia brasiliensis (n=1), and Nocardia asteroides (n=1). The median diagnostic time was 17 days. Antibiotic therapy was prolonged and included trimethoprim-sulfamethoxazole in 6/9 cases. The overall one-year case fatality was high (3/8). No recurrence was observed. We identified two cases of respiratory colonization with N. abscessus and N. cyriacigeorgica in COPD patients. CONCLUSION: Nocardiosis can occur both in immunocompetent and immunocompromised patients. It is a severe infection, with a miscellaneous clinical spectrum and complex treatments. Greater knowledge of nocardiosis is required from physicians for optimal medical care.

Bordetella bronchiseptica infection.

OBJECTIVE: To collect data of all patients admitted to hospital with a positive test to Bordetella bronchiseptica between 2001 and 2015. METHODS: We performed a retrospective monocentric study of all hospitalized patients over the past 15 years with a positive test to B. bronchiseptica. RESULTS: Nine patients were included between 2001 and 2015; two presented with infectious relapses, i.e. a total of 14 positive test samples were observed. Age, induced immunodeficiency, and preexisting respiratory illnesses are risk factors. All patients showed symptoms at sample collection and the infection was exclusively respiratory. The diagnosis was obtained through a cytobacteriological test of sputum, bronchial aspiration, or bronchial fibroscopy with a bronchoalveolar lavage. The drug susceptibility test revealed a natural resistance to cephalosporins including ceftazidime, monobactam, and fosfomycin. There were cases of resistance to penicillin A and to the trimethoprim/sulfamethoxazole association. The classically used antibiotic treatment for community-acquired pneumonia is based on probability and may thus fail. Four patients died. The duration and nature of the antibiotics to use have not been codified. CONCLUSION: B. bronchiseptica infection mainly affects the elderly. All patients should be treated, regardless of the importance of the inoculum, and all infected animals should be treated.

Assessment of sediment ecotoxicity and genotoxicity in freshwater laboratory microcosms.

One possible fate of dredged sediments is disposal in a submerged gravel pit, but this practice may be a source of contamination of the aquatic environment. In an attempt to assess the risks for the aquatic ecosystem, a microcosm test was conducted in the laboratory on three sediments of channel sections to be dredged. After a 3-day period of stabilization, pelagic organisms (microalgae, daphnids, duckweeds, pond snails) and benthic organisms (amphipods, chironomids) were introduced into microcosms. Survival and growth of organisms were monitored during 28 days. Genetic damage was measured weekly in pond snail hemocytes through the comet assay. The sediments contained high levels of metals (up to 740 mg copper/kg and 1220 mg zinc/kg), but were moderately contaminated by PAHs (total PAH content < 10 mg/kg) and PCBs (total PCB content < 0.6 mg/kg). Only moderate effects on the biota were observed, except for genetic damage on pond snail hemocytes which was significant in all microcosms. The absence of pronounced toxic effects on organisms was not expected since concentrations of some sediment toxicants were above threshold values reported in the literature, especially for metals in two sediments, and for PAHs in the three sediments. Speciation, influence of organic matter and presence of sulfides might explain the low toxicity observed. By contrast, assessment of DNA damage revealed to be more sensitive and enabled a ranking of sediments coherent with their toxic load. In the present work, the microcosm protocol previously set up with a formulated sediment appears to be fitted to natural sediments.