Rapid Detection of Carbapenem Resistance in Acinetobacter baumannii Using Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

Rapid detection of carbapenem-resistant Acinetobacter baumannii strains is critical and will benefit patient care by optimizing antibiotic therapies and preventing outbreaks. Herein we describe the development and successful application of a mass spectrometry profile generated by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) that utilized the imipenem antibiotic for the detection of carbapenem resistance in a large series of A. baumannii clinical isolates from France and Algeria. A total of 106 A. baumannii strains including 63 well-characterized carbapenemase-producing and 43 non-carbapenemase-producing strains, as well as 43 control strains (7 carbapenem-resistant and 36 carbapenem-sensitive strains) were studied. After an incubation of bacteria with imipenem for up to 4 h, the mixture was centrifuged and the supernatant analyzed by MALDI-TOF MS. The presence and absence of peaks representing imipenem and its natural metabolite was analyzed. The result was interpreted as positive for carbapenemase production if the specific peak for imipenem at 300.0 m/z disappeared during the incubation time and if the peak of the natural metabolite at 254.0 m/z increased as measured by the area under the curves leading to a ratio between the peak for imipenem and its metabolite being <0.5. This assay, which was applied to the large series of A. baumannii clinical isolates, showed a sensitivity of 100.0% and a specificity of 100.0%. Our study is the first to demonstrate that this quick and simple assay can be used as a routine tool as a point-of-care method for the identification of A. baumannii carbapenemase-producers in an effort to prevent outbreaks and the spread of uncontrollable superbugs

Investigation of the relationships between anatomical pattern, density and local swelling of oak wood

We Coupled a digital X-ray imaging system with a humid air conditioner. This new configuration allows the shrinkage behaviour of thin samples to be measured. In order to control both the temperature and the relative humidity in the chamber, an air generator was developed which ensures very stable conditions even over several months. The X-ray beam passes through the chamber to the 2D detector. Twelve samples can be placed on a rotating sample holder. The strain field due to the moisture content variations is determined by an image correlation algorithm, which compares X-ray images collected at different Moisture conditions. Moreover, inspection by X-ray simultaneously produces complementary data: the local density and the spatial organisation of the tissues within the anatomical pattern. Twelve oak samples, chosen for their wide variability of the anatomical pattern, were characterised using this device. Some models available in the literature are used to predict the swelling. The comparison between measurements and prediction is rather poor. The variable anatomical structure of the annual rings permits some explanations for this decrepancy and leads to the conclusion that the complete spatial organisation of the tissues has to be quantified to understand and to predict the behaviour of oak wood

Study of the incompatibility and replication of the 70-kb virulence plasmid of Yersinia

The 70-kb virulence plasmid, vir, from four Yersinia enterocolitica and one Y. pseudotuberculosis strains are incompatible with IncFI plasmids F'Lac and R386 while they are compatible with plasmids representing nine other incompatibility groups. Hybridization experiments carried out on one of these virulence plasmids showed that it contains the F incompatibility determinant D, incD. This determinant was cloned onto pACYC184 and the recombinant clone expressed incompatibility with F'Lac. We conclude that the incompatibility observed between F or R386 and the 70-kb virulence plasmid of Y. enterocolitica and Y. pseudotuberculosis is mediated by incD. Replication genes (rep) from the same plasmid were cloned independently in Escherichia coli. Rep and incD map on two different BamHI fragments. Surprisingly, the replicon isolated is not sensitive to inc D incompatibility. Apart from incD, vir and F share extremely little homology. In particular, there is no evidence for the presence of an F-like transfer operon on vir

A Deep Camouflage: Evaluating Android’s Anti-malware Systems Robustness Against Hybridization of Obfuscation Techniques with Injection Attacks

The threats facing smartphones have become one of the most dangerous cyberspace threats; therefore, many solutions have been developed in the commercial or academic domain to address these threats. This paper aims to test the defence robustness of some well-known commercial anti-malware systems against camouflage techniques. To this end, multiple attacks have been proposed and applied to create multiple camouflaged malware datasets based on well-known malware datasets. First of all, we proposed two injection attacks, namely benign permissions injection attack and benign permissions-code injection attack; these attacks have been used with one more attack called app re-signing attack. To the best of our knowledge, these injection attacks have been used for the first time in the Android OS domain. Furthermore, the proposed attacks have been hybridized with some commonly used obfuscation techniques, namely string encryption, class encryption, and reflection, to obtain a high degree of camouflage and avoiding anti-malware systems’ detection. To our knowledge, this is the first time that the obfuscation techniques are hybridized with other attacks. The obtained results showed that the detection accuracy of most tested anti-malware systems dropped to about 10% or less. Moreover, the average number of engines which was able to detect malware samples decreased from 45 engines when the original dataset has been tested to about 12 engines when the camouflaged datasets have been tested. © 2019, King Fahd University of Petroleum & Minerals

Genotypical and phenotypical characterization of potential virulence of intestinal avian Escherichia coli strains isolated in Algeria

In order to characterize potential pathogenic Escherichia coli strains isolated from diarrheic hens and chickens originating from intensive battery rearing in North Algeria, the presence of a large range of virulence factors and markers was studied in 50 strains by DNA-DNA hybridization on colonies and phenotypic tests. The sequences we focused on were those coding for adhesins F5, F41, F17, Pap, Afa, and Sfa; intimin Eae; and toxins STa, STb, LT1, Stx1, Stx2, CNF1, and CNF2. The phenotypes explored were the colicins, aerobactin, hemolysins, and hemagglutinin production and serum resistance. The genotypic and phenotypic tests enabled us to categorize the isolates into two distinct groups: those with a potential to invade the host (27 strains were serum resistant and/or produced aerobactin), among which three strains were also potentially diarrheagenic, one strain was LT1 + F17+ Afa+ Pap+ (enterotoxigenic E. coli) and the two others were Stx1 (verotoxigenic E. coli). Twenty-three strains were colicinogenic, including 19 strains producing colicin V. This latter factor was also detected in isolates negative for the other virulence factors. On the basis of the type of erythrocytes agglutinated, we established 14 mannose-resistant hemagglutination patterns among the 37 strains tested, including 22 serum-resistant and/or aerobactin producing strains and 15 strains negative for these two characters. None of the strains produced alpha hemolysin, whereas two strains produced beta hemolysin and enterohemolysin, respectively. Congo red fixation was observed in 25 strains. No relationship could be detected between Congo red fixation and the presence of other virulence markers, such as serum resistance and aerobactin production. This study shows that among isolates originating from the feces of diarrheic chickens, the proportion of potentially diarrheagenic E. coli strains is low

Résistance aux antibiotiques de souches d'Escherichia coli bovines et aviaires isolées en Algérie

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