Sofiane Bakour

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.

Worldwide emergence of colistin resistance in Klebsiella pneumoniae from healthy humans and patients in Lao PDR, Thailand, Israel, Nigeria and France owing to inactivation of the PhoP/PhoQ regulator mgrB: an epidemiological and molecular study

The emergence of colistin-resistant Klebsiella pneumoniae (CRKP) is a major public health concern worldwide. In this study, the prevalence and molecular basis of colistin resistance in CRKP isolated from healthy individuals and patients in Lao PDR, Thailand, Nigeria and France were investigated. Stool samples were screened by culture for the presence of colistin-resistant Klebsiella spp. Whole-genome sequence analysis was used to decipher the molecular mechanism of colistin resistance in a blaNDM-1-positive in vitro-selected CRKP mutant. PCR amplification and sequencing of the mgrB genetic environment was performed for all CRKP isolates as well as control colistin-susceptible K. pneumoniae (CSKP) isolates recovered from the same stools. A total of 869 stool samples were screened for colistin-resistant Klebsiella spp., yielding 32 CRKP and 2 colistin-resistant Klebsiella oxytoca. Comparative whole-genome sequence analysis revealed that an in vitro-selected CRKP mutant had an insertion sequence in its mgrB gene, as well as missense mutations in other selected clones. Of the 34 colistin-resistant Klebsiella spp. isolates, 14 (41.2%; 13 CRKP and 1 K. oxytoca) from the four countries also had various defects in their mgrB genes, but no such defects were found in the CSKP controls (P<10(-4)). Few mutations were observed in pmrAB compared with mgrB among the CRKP isolates. The worldwide emergence of CRKP is a major public health concern. Detection and surveillance of such strains are warranted to prevent an uncontrollable pandemic. Inactivation of the PhoP/PhoQ regulator gene mgrB is associated with ≥40% of colistin resistance among the CRKP isolates observed in this study.

Rapid identification of carbapenemase-producing Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii using a modified Carba NP test.

Biochemical tests have been previously developed to identify carbapenemase-producing Enterobacteriaceae, Pseudomonas spp. (Carba NP test) and Acinetobacter spp. (CarbAcineto NP test). We evaluated a modified Carba NP test to detect carbapenemase production in Enterobacteriaceae, Pseudomonas and Acinetobacter species using a single protocol with rapid results and found good reliability and speed.

Characterization of NDM-1- and OXA-23-producing Acinetobacter baumannii isolates from inanimate surfaces in a hospital environment in Algeria

BACKGROUND Investigation of several outbreaks of multidrug-resistant Acinetobacter baumannii infection has demonstrated that contamination of the inanimate hospital environment could be implicated in the spread of these multidrug-resistant strains. AIM To investigate the occurrence of carbapenem-resistant A. baumannii on inanimate surfaces and possible dissemination in the hospital environment in Algeria as a potential source of infection in humans. METHODS A. baumannii strains were isolated from the hospital environment and identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Antimicrobial susceptibility was determined using disc diffusion and E-test methods. Carbapenemase activity was detected using microbiological tests, including modified Hodge test, modified Carba NP test, and EDTA test. Carbapenem resistance determinants were studied by polymerase chain reaction (PCR) and sequencing. Clonal relatedness was determined using multi-locus sequence typing (MLST). RESULTS A total of 67 A. baumannii isolates were obtained from 868 environmental samples and identified by MALDI-TOF MS. Among them, 61 isolates were resistant to imipenem with minimum inhibitory concentration >32 μg/mL and positive by the modified Hodge test and modified Carba NP test. In addition, the activity of carbapenemase was inhibited by EDTA in 32 strains. PCR and sequencing showed the presence of blaOXA-23 gene in 29 strains, and the blaNDM-1 gene in 32 isolates. MLST demonstrated the presence of five types of ST (ST19, ST2, ST85, ST98, and ST115). CONCLUSION Our study demonstrated the dissemination of carbapenemase-producing A. baumannii strains recovered from inanimate surfaces in a hospital environment, surrounding patients, healthcare workers and visitors, in Algeria as a potential source for nosocomial infection.

High Prevalence of blaNDM-1 Carbapenemase-Encoding Gene and 16S rRNA armA Methyltransferase Gene among Acinetobacter baumannii Clinical Isolates in Egypt

ABSTRACT The main objective of this study was to decipher the molecular mechanism of resistance to carbapenems and aminoglycosides in a large series of 150 Acinetobacter baumannii clinical isolates collected from July 2012 to September 2013 in Egypt. We report for the first time the emergence of blaNDM-1 and the cooccurrence of 16S rRNA methylase armA with blaNDM-1 and blaOXA-23 in Egyptian hospitals. Multilocus sequence typing identified 27 distinct sequence types, 11 of which were novel.

Molecular characterisation of extended-spectrum β-lactamase- and plasmid AmpC-producing Escherichia coli strains isolated from broilers in Béjaïa, Algeria

This study aimed to characterise the molecular support of antibiotic resistance in expanded-spectrum cephalosporin (ESC)-resistant Escherichia coli isolates recovered from healthy broilers in Béjaïa, northeast Algeria. A total of 61 intestinal swabs from slaughtered broilers from four regions in Béjaïa locality, Algeria, were collected between February and April 2014, from which 20 ESC-resistant E. coli strains were isolated. Escherichia coli isolates were identified by classical biochemical and MALDI-TOF methods. Antibiotic susceptibility testing was performed using disk diffusion and Etest methods. Screening for β-lactamases, aminoglycoside-modifying enzyme (AME)-encoding genes and qnr determinants was performed by PCR and sequencing. Clonal relatedness was determined using molecular typing by multilocus sequence typing (MLST). Antibiotic susceptibility testing revealed that the isolates showed high rates of resistance (>90%) to amoxicillin, amoxicillin/clavulanic acid, piperacillin/tazobactam, aztreonam, ceftazidime, streptomycin, tobramycin, nalidixic acid and ciprofloxacin. Low rates of resistance were observed for kanamycin (35%), amikacin (30%), cefoxitin (20%) and cefotaxime (15%). Molecular characterisation revealed that all of the isolates expressed the blaTEM-1 gene. Fourteen of them harboured the blaSHV-12 gene, two harboured the blaCTX-M-1 gene and four isolates harboured blaCMY-2. Screening for AME-encoding genes demonstrated that all isolates contained the aadA gene. In addition, qnrA was detected as the quinolone resistance determinant in 13 isolates. MLST revealed four known sequence types (STs), including ST744, ST38, ST1011 and ST2179, as well as one new sequence type (ST5086). Here we report the first study describing the clonal diversity of extended-spectrum β-lactamase (ESBL)- and plasmid AmpC-producing E. coli isolated from healthy broilers in Algeria.

Carbapenemases and extended-spectrum β-lactamases producing Enterobacteriaceae isolated from Tunisian and Libyan hospitals.

INTRODUCTION The aim of the study was to investigate the prevalence of extended-spectrum β-lactamase (ESBL) and carbapenemase production among clinical isolates of Enterobacteriaceae recovered from Tunisian and Libyan hospitals. METHODOLOGY Bacterial isolates were recovered from patients in intensive care units and identified by biochemical tests and MALDI-TOF. Antibiotic susceptibility testing was performed by disk diffusion and the E-test method. ESBL and carbapenemase activities were detected using standard microbiological tests. Antibiotic resistance-encoding genes were screened by PCR and sequencing. Clonal relationships between Klebsiella pneumoniae strains were carried out using multi-locus sequence typing (MLST). RESULTS A total of 87 isolates were characterized, with 51 and 36, respectively, identified as E. coli and K. pneumoniae. Overall the resistance prevalence was high for aminoglycosides (> 60%), fluoroquinolones (> 80%), and extended-spectrum cephalosporins (> 94%), and was low for imipenem (11.4%). Among this collection, 58 strains (66.6%) were ESBL producers and 10 K. pneumoniae strains (11.4%) were carbapenemase producers. The antibiotic resistance-encoding genes detected were blaCTX-M-15 (51.7%), blaTEM-1 (35.6%), several variants of blaSHV (21.8%), and blaOXA-48 (11.4%). The MLST typing of K. pneumoniae isolates revealed the presence of multiple clones and three novel sequence types. Also, close relationships between the OXA-48-producing strains from Tunisia and Libya were demonstrated. CONCLUSIONS This study is the first paper describing the emergence of carbapenemase- and ESBL-producing Enterobacteriaceae, sensitive to colistin, isolated in Tunisia and Libya. Active surveillance and testing for susceptibility to colistin should be implementing because resistance to colistin, mainly in Klebsiella, has been recently reported worldwide.

Early detection of metallo-β-lactamase NDM-1- and OXA-23 carbapenemase-producing Acinetobacter baumannii in Libyan hospitals

Acinetobacter baumannii is an opportunistic pathogen causing various nosocomial infections. The aim of this study was to characterise the molecular support of carbapenem-resistant A. baumannii clinical isolates recovered from two Libyan hospitals. Bacterial isolates were identified by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). Antibiotic susceptibility testing was performed using disk diffusion and Etest methods, and carbapenem resistance determinants were studied by PCR amplification and sequencing. Multilocus sequence typing (MLST) was performed for typing of the isolates. All 36 imipenem-resistant isolates tested were identified as A. baumannii. The blaOXA-23 gene was detected in 29 strains (80.6%). The metallo-β-lactamase blaNDM-1 gene was detected in eight isolates (22.2%), showing dissemination of multidrug-resistant (MDR) A. baumannii in Tripoli Medical Center and Burn and Plastic Surgery Hospital in Libya, including one isolate that co-expressed the blaOXA-23 gene. MLST revealed several sequence types (STs). Imipenem-resistant A. baumannii ST2 was the predominant clone (16/36; 44.4%). This study shows that NDM-1 and OXA-23 contribute to antibiotic resistance in Libyan hospitals and represents the first incidence of the association of these two carbapenemases in an autochthonous MDR A. baumannii isolated from patients in Libya, indicating that there is a longstanding infection control problem in these hospitals.

Emergence of KPC-producing Klebsiella pneumoniae ST512 isolated from cerebrospinal fluid of a child in Algeria

We report class A carbapenemase (KPC)-3-producing Klebsiella pneumoniae meningitis in a 6-month-old child in Algeria. Multilocus sequence typing showed that the sequence type obtained corresponded to ST512, an allelic single-locus variant of the pandemic ST258 widely distributed in KPC producers from Europe. To our knowledge, this is the first report of KPC-3-producing K. pneumoniae ST512 in a North African country.

High rates of CTX-M-15-producing Escherichia coli and Klebsiella pneumoniae in wild boars and Barbary macaques in Algeria

OBJECTIVES The present study aimed to screen for the presence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in wild boars and Barbary macaques in Béjaïa and Jijel, Algeria. METHODS A total of 216 faecal samples collected between September 2014 and August 2015 were cultured on MacConkey agar supplemented with 1μg/mL ceftazidime. Isolates were identified by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). Antimicrobial susceptibility testing was performed by the disk diffusion method, and ESBLs were characterised by PCR and sequencing. Clonal relatedness was studied by multilocus sequence typing (MLST). RESULTS A total of 47 ESBL-producing isolates were recovered from faecal samples from 40 (44%) of 90 wild boars and 7 (6%) of 126 from Barbary macaques, including 30 Escherichia coli and 17 Klebsiella pneumoniae. Results of PCR and sequencing analysis showed that all of the isolates produced CTX-M-15, and 25 isolates co-produced TEM-1. MLST demonstrated the presence of eight sequence types (STs) among the E. coli isolates (ST617, ST131, ST648, ST405, ST1431, ST1421, ST69 and ST226), whereas only one clone (ST584) was identified for all isolates of K. pneumoniae recovered from wild boars (n=10) and Barbary macaques (n=7). CONCLUSIONS This is the first report of CTX-M-15-producing E. coli and K. pneumoniae in wild animals from Algeria. The results show that African wildlife can act as a reservoir of the epidemic E. coli clone ST131 producing CTX-M-15, suggesting that this lineage can survive in different ecological niches and adapt to different hosts.