CHROMagar Acinetobacter Research Articles

Soil-specific responses in the antibiotic resistome of culturable Acinetobacter spp. and other non-fermentative Gram-negative bacteria following experimental manure application.

Acinetobacter spp. and other non-fermenting Gram-negative bacteria (NFGNB) represent an important group of opportunistic pathogens due to their propensity for multiple, intrinsic, or acquired antimicrobial resistance (AMR). Antimicrobial resistant bacteria and their genes can spread to the environment through livestock manure. This study investigated the effects of fresh manure from dairy cows under antibiotic prophylaxis on the antibiotic resistome and AMR hosts in microcosms using pasture soil. We specifically focused on culturable Acinetobacter spp. and other NFGNB using CHROMagar Acinetobacter. We conducted two 28-days incubation experiments to simulate natural deposition of fresh manure on pasture soil and evaluated the effects on antibiotic resistance genes (ARGs) and bacterial hosts through shotgun metagenomics. We found that manure application altered the abundance and composition of ARGs and their bacterial hosts, and that the effects depended on the soil source. Manure enriched the antibiotic resistome of bacteria only in the soil where native bacteria had a low abundance of ARGs. Our study highlights the role of native soil bacteria in modulating the consequences of manure deposition on soil and confirms the potential of culturable Acinetobacter spp. and other NFGNB to accumulate AMR in pasture soil receiving fresh manure.

Assessment of the presence of Acinetobacter spp. resistant to β-lactams in commercial ready-to-eat salad samples

Acinetobacter baumannii is a well-known nosocomial infection causing agent. However, other Acinetobacter spp. have also been implicated in cases of human infection. Additionally, these bacteria are known for the development of antibiotic resistance thus making the treatment of the infections they cause, challenging. Due to their relevance in clinical setups less attention has been paid to their presence in foods, and its relation with infection/dissemination routes. In the current study commercial Ready-To-Eat (RTE) salads were analyzed seeking for antibiotic resistant Acinetobacter spp. A preliminary screening allowed us to recover Gram-negative bacteria resistant to β – lactams using cefotaxime, third generation cephalosporins, as the selective agent, and this was followed by identification with CHROMagar™ Acinetobacter and 16S rDNA sequencing. Finally, the isolates identified as Acinetobacter spp. were reanalyzed by PCR to determine the presence of nine potential Extended Spectrum β Lactamases (ESBL). Two commercial RTE salad brands were included in the study (2 batches per brand and 8 samples of each batch making a total of 32 independent samples), and compared against an organic lettuce. High concentrations of β – lactam, resistant bacteria were found in all the samples tested (5 log CFU/g). Additionally, 209 isolates were phenotypically characterized on CHROMagar Acinetobacter. Finally, PCR analysis identified the presence of different ESBL genes, being positive for blaACC, blaSHV, blaDHA and blaVEB; out of these, blaACC was the most prevalent. None of the isolates screened were positive for more than one gene. To conclude, it is important to highlight the fact that pathogenic species within the genus Acinetobacter spp., other than A. baumannii, have been identified bearing resistance genes not typically associated to these microorganisms highlight the importance of continuous surveillance.

Evaluation of CHROMagar Acinetobacter and MacConkey media for the recovery of Acinetobacter baumannii from soil samples.

The opportunistic pathogen Acinetobacter baumannii occupies niches in human and veterinary clinics and other environments. This comparative study was designed to assess the recovery rate of Ac. baumannii from 20 soil samples collected in Germany (from which Ac. baumannii had been previously isolated) on selective CHROMagar Acinetobacter (CMA) and MacConkey Agar (MCA). Suspected Ac. baumannii were confirmed by detection and sequencing of blaOXA-51-like genes. Overall, the recovery rate of Ac. baumannii from both media was similar. Out of the 20 soil samples enriched in mineral salt medium (MM) plus 0.2% acetate for 5h, Ac. baumannii was recovered from 12 (60%) on CMA and 11 (55%) on MCA, and from 14 (70%) with both selective media after enrichment for 24h. Typical and distinct colonies of Ac. baumannii were more often observed on CMA with soil enriched in MM for 5h, while on MCA distinct colonies were more obvious after 24h. In five soil samples (25%), strains harbouring different OXA-51-like variants were recovered on MCA. Late lactose fermentation (48h) was observed on MCA. The study suggests that no single growth medium would efficiently recover Ac. baumannii from all soil samples.

Cattle manure application triggers short-term dominance of Acinetobacter in soil microbial communities

Manure application improves soil productivity but also spreads microorganisms, some of which can be of clinical relevance. The ability of manure to spread common human pathogens has been widely studied but we lack understanding on whether it also disseminates opportunistic pathogens like Acinetobacter and other non-fermenting Gram-negative bacteria (NFGNB). We designed a microcosm experiment simulating the application of fresh manure to soil to analyse the effects on soil microbial communities (and vice versa), focusing on Acinetobacter and other NFGNB. We conducted two independent experiments with fresh cattle manure from a dairy farm and two pasture soils from different organic farms. We sampled the microcosms on days 2, 7, 14, 28 and 84, and characterized the microbial communities through sequencing of 16S rRNA amplicons from i) total communities and ii) those cultured on CHROMagar Acinetobacter (i.e., selective for NFGNB) after 24-h growth. Manure altered the community composition of soil microorganisms whereas the reverse effects were weaker, showing a transition to an environmentally structured community. Acinetobacter species increased their relative abundance in manure and soil under manure on day 2, especially in soils previously exposed to γ-irradiation to reduce the load of native microorganisms. Although manure spread most Acinetobacter phylotypes in the soil, it also stimulated a few from the soil that became occasionally abundant in manure. This study demonstrates that Acinetobacter species may dominate in soil and manure for a short time after deposition, and highlights their high responsiveness and competitiveness to changes likely associated with an increase in labile resources.

Molecular Identification of epsA and ompA genes for Acintobacter baumannii Isolated from Burn Wounds

This study was designed to molecular detection of epsA and ompA genes for Acinetobacter baumanniiIsolates that isolated from clinical. Burn wounds samples from a total of 80 clinical different Wounds,samples were collected from Ghazi Al Hariri Hospital and Baghdad hospital in Baghdad / Iraq. The resultsof the current study showed that seventy (87.5%) were clinical wounds positive samples, while the rest (10)were negative wounds samples (12.5 %). From 70 samples inoculated on the Chromagar Acinetobacter, 10isolate were grown on the medium, A. baumannii isolates on the Chromagar appeared as bright red coloniesafter 24h and incubation at 37 C . The results of epsA and ompA genes detection clarify that 8 isolate(80%) of A. baumannii isolates gave a positive result and carrying epsA and ompA genes while 2 (20%) ofAcintobacter baumannii isolates were lack the gene and no cross reactivity could be observed with any ofthe AS-3 and AS-9 isolates. The identification of A. baumannii isolates were depended on culturing theseisolates on CHROM agar Acinetobacter, MacConkey, blood, nutrient agar, biochemical tests and API NE 20test VITEK 2 . Compact were carried out the confirms. Results showed the amplification of epsA and ompAgenes for eight. A. baumannii isolates were AS-1, AS-2, AS-4, AS-5, AS-6, AS-7, AS-8 and AS-10. PCRproduct 531 bp of ompA gene and 451 bp of epsA gene.

New Approaches to Colonization Screening in Response to Emerging Antimicrobial Resistance

Background: The capacity to monitor the emergence of carbapenemase-producing organisms (CPO) is critical in limiting transmission. CPO-colonized patients can be identified by screening rectal specimens for carbapenemase genes and the Cepheid GeneXpert Carba-R (XCR), the only FDA-approved test, is limited to 5 carbapenemase genes and cannot identify the bacterial species. Objective: We describe the development and validation of culture-based methods for the detection of CPO in rectal cultures (RCs) and nonrectal cultures (NRCs) of tracheal aspirate and axilla-groin swabs. Methods: Colonization screening was performed at 3 US healthcare facilities; specimens of RC swabs and NRC ESwabs were collected. Each specimen was inoculated to a MacConkey broth enrichment tube for overnight incubation then were subcultured to MacConkey agar with meropenem and ertapenem 10 µg disks (BEMA) and CHROMagar KPC (KCHR) or CHROMagar Acinetobacter (ACHR). All media were evaluated for the presence of carbapenem-resistant organisms; suspect colonies were screened by real-time PCR for the most common carbapenemase genes. MALDI-TOF was performed for species identification. BEMA, a previously validated method, was the comparator for 52 RCs; clinical culture (CC) served as the comparator method for 66 NRCs. Select CPO-positive and -negative specimens underwent reproducibility testing. Results: Among 56 patients undergoing colonization screening, 12 (21%) carried a CPO. Only 1 patient had CPO solely from RC. Also, 6 patients had both CPO-positive RC and NRC, and 5 patients only had a CPO-positive NRC. Of the latter, 4 had a CPO-positive tracheal specimen, and 1 had a positive culture from both tracheal and axilla-groin specimens. Sensitivity of BEMA (70%) for NRC was lower than for KCHR (96%) and ACHR (88 %) for all specimens. All methods showed a specificity of 100% and reproducibility of 92%. The detected CPO included OXA-23–positive Acinetobacter baumannii, NDM-positive Escherichia coli, KPC-positive Pseudomonas aeruginosa and 4 genera of KPC-positive Enterobacteriaceae. Conclusions:The addition of nonrectal specimens and use of selective media contributed to increased sensitivity and enhanced identification of CPO-colonized patients. Positive cultures were equally distributed among the 3 specimen types. The addition of the nonrectal specimens resulted in the identification of more colonized patients. The culture-based method was successful in detecting an array of different CPOs and target genes, including genes not detected by the Carba-R assay (eg, blaOXA-23-like). Enhanced isolation and characterization of CPOs will be key in aiding epidemiologic investigations and strengthening targeted guidance for containment strategies.Funding: NoneDisclosures: We discuss the drug combination aztreonam-avibactam and acknowledge that this drug combination is not currently FDA approved.

Comparative assessment of growth media and incubation conditions for enhanced recovery and isolation of Acinetobacter baumannii from aquatic matrices

Acinetobacter baumannii causes serious multidrug resistant nosocomial infections around the world. This comprehensive comparative study was designed to assess the effect of temperature (30, 37 and 42 °C), incubation (aerobic and microaerobic) condition and selective [CHROMagar Acinetobacter (CHR) and Leeds Acinetobacter Medium (LAM)] and non-selective [Modified Karmali Agar (MKA)] growth media on the enhanced recovery of A. baumannii from a variety of water (agricultural, recreational, raw drinking intake source, pre-chlorinated and post-chlorinated wastewater effluent) samples spiked with a known number of A. baumannii cells. After spiking each water type with a known number of cells in 10 mL volume, the sample was passed through a membrane filter (pore size 0.45 μm) and filters were placed on different selective media plates and subjected to incubate at various incubation conditions. The results reported in this study show that for all water types tested (except post-chlorinated wastewater effluent), LAM was the most effective selective growth medium in combination with variable temperature and incubation conditions for yielding high recovery rates of A. baumannii cells. Overall, A. baumannii showed that it has a high adaptive capacity to grow on selective and non-selective growth media at different temperature and incubation conditions. The data described in this study suggest that no single incubation condition and growth media would efficiently recover A. baumannii from all environmental water types tested. This data also indicate that selective growth media and incubation condition can significantly affect the recovery of A. baumannii. Differences in recovery of A. baumannii observed in this study which appeared to be dependent on the temperature and environmental characteristics of incubation as well as the sample type, suggest the need for caution when comparing recovery using different protocols.

Direct detection of Acinetobacter baumannii by loop-mediated isothermal amplification in patients with respiratory tract infection

Background Rapid detection and treatment of Acinetobacter baumannii which is a health-care-associated pathogen that causes outbreaks and frequently encountered in ICU patients on mechanical ventilation is very important. Aim The present study aimed to detect the frequency of A. baumannii in sputum sample by loop-mediated isothermal amplification (LAMP) assay in comparison with the different culture methods. Patients and methods In all, 200 sputum samples and 100 tracheal aspirates (TA) were included to detect the frequency of Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, A. baumannii, Pseudomonas aeruginosa, and Enterobacter spp. (ESKAPE) pathogens by cultural methods and to detect A. baumannii from sputum sample by LAMP assay comparing its results with CHROMagar Acinetobacter and conventional culture methods referring to the rate of multidrug-resistant A. baumannii. Results By conventional culture, positive culture was reported in 228/300 (76%) of all samples. A. baumannii and Klebsiella spp. were the most identified pathogens as they were detected in 27/145 (18.6%) and 19/145 (13%) of sputum samples and 19/83 (22%) and 43/83 (51.8%) of TA. Regarding culture on CHROMagar 46 isolates were identified as A. baumannii, 27 were from sputum sample, and 19 from TA. Out of 46 A. baumannii isolates multidrug-resistant A. baumannii were detected in 9/27 (33.3%) and 15/19 (78.9%) in sputum samples and TA, respectively. DNA of A. baumannii was detected in 28/200 (14%) by LAMP assay from sputum samples. Sensitivity and specificity of LAMP assay were 100 and 99.5% when compared with the conventional culture. Conclusion CHROMagar Acinetobacter and LAMP assay are cost-efficient methods in comparison to conventional culture. LAMP assay is distinguished from the others for its simplicity and rapid detection of pathogens.

Phenotypic and Molecular detection of Acinetobacter baumannii isolated from patients in Duhok city-Iraq

Acinetobacter baumannii (A. baumannii) is an opportunistic pathogen and one of the most importnat Multidrug resistant microorganisms responsible for a vast array of nosocomial infections. 41 (6.8 %) isolates of A. baumannii were obtained from a total of 603 clinical samples of burn and sputum during the period from March 2018 to February 2019. Twenty two isolates (3.6%) of A. baummanni were recovered from burn infections and nineteen isolates (3.2%) from sputum specimens. Identification and characterization of these isolates was accomplished by the aid of selective media (CHROM agar Acinetobacter) and was finally confirmed by VITEK 2 identification system test. Molecular identification utilizing genus and species-specific primers to detect the 16S rRNA and blaOXA-51 was also applied. The Antibiotic resistance testing was done by the Kirby-Bauer disc diffusion method, 24 .4% of the isolates were Multi-Drug Resistance (MDR), while 65.9% were extensive drug resistance (XDR). All isolates were absolutely resistant (100 %) to most of the antibiotics in use: cefixime, cefotaxime, ceftriaxone, ceftazidime, piperacillin-tazobactam, amoxicillin-tazobactam, while the resistant profile for the other antibiotics can be represented as follows 98 %, 95 %, 90 %, and 83 % For both ciprofloxacin and norfloxacin, gentamycin and meropenem, amikacin, and azithromycin and imipenem, respectively. On the other hand, levofloxacin has a moderate effect on the isolates shown by 51% resistant isolates followed by doxycycline for which 39% of the isolates were resistant. Colistin was the only antimicrobial agent that has an intense effect as the majority of the isolates were sensitive. All the selected isolates of A. baumannii were successfuly produced band corresponded to the intended genes. Accurate and early detection of such bacteria is essential for stimulates effective treatment specifically in intensive care units. Molecular techniques have been successfully applied with high specificity using 16S rRNA and blaOXA-51-like gene as a simple and reliable method to differentiate A. baumannii strains.

Prevalence of Genes Involved in Colistin Resistance in Acinetobacter baumannii: First Report from Iraq.

Background and Aim: Colistin is increasingly being used as a "last-line" therapy to treat infections caused by multidrug-resistant (MDR) Acinetobacter baumannii isolates, when essentially no other options are available in these days. The aim of this study was to detect genes associated with colistin resistance in A. baumannii. Methods: One hundred twenty-one isolates of A. baumannii were collected from clinical and environmental samples during 2016 to 2018 in Baghdad. Isolates were diagnosed as A. baumannii by using morphological tests, Vitek-2 system, 16SrRNA PCR amplification, and sequencing. Antibiotic susceptibility test was carried out using disk diffusion method. Phenotypic detection of colistin resistance was performed by CHROMagar™ COL-APSE medium and broth microdilution method for the determination of the minimal inhibitory concentration. Molecular detection of genes responsible for colistin resistance in A. baumannii was performed by PCR. Results: Ninety-two (76%) of the 121 A. baumannii isolates were colistin resistant. Twenty-six (21.5%) of the 121 isolates showed positive growth on CHROMagar Acinetobacter base for MDR. PCR detected mcr-1, mcr-2, and mcr-3 genes in 89 (73.5%), 78 (64.5%), and 82 (67.8%) A. baumannii isolates, respectively. Seventy-eight (64.5%) of the 121 isolates harbored the integron intI2 gene and 81 (66.9%) contained intI3 gene. Moreover, 60 (49.6%) of the 121 isolates were positive for the quorum sensing lasI gene. Conclusion: The presence of a large percentage of colistin-resistant A. baumannii strains in Baghdad may be due to the presence of mobile genetic elements, and it is urgent to avoid unnecessary clinical use of colistin.

Characterization of Acinetobacter baumannii from water and sludge line of secondary wastewater treatment plant

The elimination of potentially pathogenic bacteria in wastewater treatment plants (WWTPs) attracts much attention in public health. Reports on the occurrence of the emerging hospital pathogen Acinetobacter baumannii in wastewaters do not include a continuous monitoring at all WWTP stages. The objective of this study was to characterize A. baumannii recovered from the water and sludge line of the secondary WWTP in Zagreb, Croatia over the period of one year. Recovery of A. baumannii was performed using CHROMagar Acinetobacter plates. Antimicrobial susceptibility testing was performed with broth microdilution and results interpreted using EUCAST breakpoints for clinical isolates of A. baumannii. Molecular characterization was performed by WGS and cgMLST. The secondary WWTP treating the urban wastewater is constantly receiving viable A. baumannii along with genes encoding carbapenem resistance, and emitting them via effluent into the environment. Furthermore, A. baumannii from influent are incorporated into activated sludge flocs in aeration basin. A. baumannii can survive the technological process of anaerobic mesophilic sludge digestion, and is finally destroyed in alkaline lime-treated stabilized sludge. The majority (102/119) of A. baumannii isolates were carbapenem-resistant, while antibiotic-susceptible isolates (17/119) were rarely recovered from all WWTP stages. Carbapenem-resistant isolates belonged to international clonal lineage IC2 carrying OXA-23 and IC1 carrying OXA-72, while the susceptible isolates belonged to IC5 or were unclustered. Increased resistance to antibiotics, together with the appearance of carbapenem- and even pandrug-resistant isolates in effluent as compared to influent wastewater, suggests the need of additional disinfection of effluent prior to its discharge into the natural recipient.

Study the antibacterial Effect of CO2 Laser againstMultidrug Resistant Biofilm formationAcinetobacterbaumanniiIsolated from Different Samples

Acinetobacterbaumanniihas become known as an imperative healthcare associated and multidrug-resistant microorganismwarrants the training of novel methodologies for prevention and treatment. This report aimed to estimate the antimicrobial properties ofCO2laser at 10600 nm on A.baumannii isolates. Two hundred specimens were collected from patients suffering from wound infections, urinary tract infections, respiratory infections and medical equipment samples. 50 samples for each. These samples were gathered from diverse hospitals in Baghdad\Iraq. The collected specimens were streaked directly on CHROM agar Acinetobacter. The positive culture results were diagnosed genotypicaly, recA gene (a house keeping gene) was used for this purpose. All isolates were tested for antibiotic sensitivity testing and 13 divers of antibiotics were used. Also, the ability of biofilm formation was detected. CO2laser 10600 nm at power densities (1000,1500,2000 and 2500) W/cm2 with exposure time (15,30, 45 and 60) second was used for the irradiation experiment.17 isolates were positive to A. baumannii which were distributed as follows 4 ,6, 3 and 4 isolates from wounds,urine , sputum and medical equipments samples respectively. Antibiotic sensitivitytest results considered ten of A.baumanniias MDR isolates because of its capability to resist ten antibiotics belong to cephalosporins, carbapenems,ampicillinsulbactam, fluoroquinolones, and aminoglycosides groups. In additions 14(82.35%) out of the 17 isolates were biofilm producer ranged from weak, moderate to strong biofilm produer. Four isolates, one from four different isolation sources were chosen for CO2 laser irradiation each isolate resisted to all antibiotics used in this study and strong biofilm producer. In general, in this study the results showed that when using power densities (2000 and 2500 W/cm2 at exposure time 30s and 45s) of CO2 laser irradiations the maximum rate of killing percentage was ranged from 97% to 100% for A.baumannii isolated from clinical samples while more exposure time were needed (45s and 60s) to get the same killing percentage for A.baumannii isolated from medical equipments. Consequently, the use of CO2 laser 10600 nm which is independent towards the antibacterial agents resistance pattern of MDR A.baumannii could verify advantageous in treatment of various types of infections caused by these bacteria in addition it may be used in sterilization of some medical equipment surfaces

Emission of extensively-drug-resistant Acinetobacter baumannii from hospital settings to the natural environment

Acinetobacter baumannii is a leading emerging pathogen that is frequently recovered from patients during hospital outbreaks. The role of environmental A.baumannii reservoirs is therefore of great concern worldwide. To investigate the connection between A.baumannii causing hospital outbreaks and environmental isolates from hospital wastewater, urban sewage and river water as the final natural recipient of wastewaters. Clinical isolates from patients with hospital-acquired pneumonia and environmental isolates from water were collected during a two-month monitoring period. Recovery of A.baumannii was performed using CHROMagar Acinetobacter plates, incubated at 42°C for 48h. Identification was performed by matrix-assisted laser desorption ionization-time of flight mass spectrometry and analyses of rpoB gene. The antibiotic resistance profiles were interpreted according to criteria given for clinical isolates of A.baumannii. The sequence types (ST) were retrieved by multi-locus sequence typing. Fourteen of 19 isolates recovered from patients, hospital wastewaters, urban sewage and river water belonged to ST-195. The remaining five isolates recovered from patients and river water were assigned to ST-1421. All isolates showed very strong relatedness and clustered into CC92, which corresponds to IC2. All isolates were non-susceptible to at least one agent in all but two or fewer antimicrobial categories, and thus were classified as 'extensively-drug-resistant' (XDR). Heteroresistance to colistin was found in two isolates from hospital wastewater. Close relatedness of clinical and environmental isolates suggests the emission of XDR A.baumannii via the untreated hospital wastewater in the natural environment.

CHROMagar Acinetobacter medium for detection of carbapenemase-producing Acinetobacter spp. strains from spiked stools

The recently modified CHROMagar Acinetobacter medium was evaluated for detection of carbapenemase-producing Acinetobacter baumannii from spiked stools. A total of 45 Acinetobacter spp. isolates were tested. The CHROMagar Acinetobacter medium had a high sensitivity of 86.5% and a specificity of 75%. This medium is likely to be most useful for controlling outbreaks and in endemic situations.

Culture Media for Detection of Acinetobacter baumannii Selective Media for Detection of A baumannii

Detection of Acinetobacter baumannii is of crucial importance to the prevention of the development of nosocomial infections. CHROMagar Acinetobacter® is a new selective medium recently developed for the rapid identification of A. baumannii. This medium incorporates enzymatic substrates that enable colour- based preliminary identification of bacterial colonies recovered within 18 to 24 h of inoculation. Sheep blood agar (SBA) supplemented with ertapenem contains few modifications and has not yet been defined in the literature. The aim of this study was to evaluate CHROMagar Acinetobacter® for detection of A. baumannii and compare its performance to that of SBA supplemented with ertapenem. A total of 73 Gram-negative bacteria were evaluated. A. baumannii, Pseudomonas aeruginosa, Stenotrophomonas maltophilia and carbapenemase-positive Klebsiella pneumoniae were grown on CHROMagar Acinetobacter® and supplemented SBA media. Susceptible clinical isolates and standard strains of Enterobacteriaceae were inhibited by both CHROMagar Acinetobacter® and supplemented SBA. C. albicans isolates, inoculated with mixed samples, did not grow on CHROMagar Acinetobacter® after 24 or 48 h, but did grow on supplemented SBA after 24 h and exhibited distinct colony morphology. A. baumannii, the most clinically relevant of the bacteria tested, have a particular propensity for nosocomial transmission, due in part to their sustained survival on environmental surfaces as well as their multidrug resistance. The prevalence of infection with A. baumannii has increased significantly during the last decade. Due to well-designed solid selective culture media are required for detection of Acinetobacter spp. We advise the use of supplemented SBA and CHROMagar Acinetobacter® medium for rapid detection of nosocomial infection in the absence of a confirmatory procedure. Investigation into the metabolism of A. baumannii will facilitate the development of chromogenic media.

Epidemiology of extensive drug resistant Acinetobacter baumannii (XDRAB) at Security Forces Hospital (SFH) in Kingdom of Saudi Arabia (KSA)

Objectives:Extensively drug-resistant Acinetobacter baumannii (XDRAB) became a worldwide nosocomial threat. The aim of this study was to assess the epidemiology and to evaluate the prevalence of carbapenem-resistant A. baumannii (CRAB). We also discuss therapeutic options for the management of their infections.Methods:Antibiotic susceptibility was determined in 506, 510 and 936 duplicate isolates of A. baumannii isolated in 2006, 2009 and 2012, respectively. In 2012, 12 unique XDRAB strains were isolated from patients with serious ventilator-associated pneumonia (VAP). Susceptibility tests were performed using the microdilution method according to Clinical and Laboratory Standards Institute (CLSI) recommendations. MICs were determined in triplicate by E-test according to the manufacturer's recommendations. Susceptible and multidrug-resistant A. baumannii (MDRAB) strains were detected using CHROMagar Acinetobacter medium. Carbapenem resistant A. baumannii was investigated for carbapenemase production by the modified Hodge test (MHT) and by multiplex PCR. A Synergy test was performed using the E-test method.Results:Considering years 2006, 2009 and 2012, the susceptibilities to meropenem and imipenem were 64–81.2%, 34.5–45.3%, and 8.3–11%, respectively. Concerning the 12 XDRAB strains, all isolates were susceptible to colistin and resistant to meropenem and imipenem. Culture on CHROMagar Acinetobacter confirmed that all are MDRAB. The gene profiles detected in PCR assays showed that all the strains possess OXA-51.Out of the 12 isolates, 11 possess the oxa-23 gene and one harbours the gene 24/40. A good synergistic effect was detected between colistin and tigecycline.Conclusions:In this study, A. baumannii susceptibility to carbapenems showed a drastic reduction and represents a major epidemiological concern. The main carbapenem resistance mechanism is mediated by class D-OXA-type enzymes (oxa-23 and oxa-24/40) with Carbapenemase activity. Therapeutic options are exceedingly limited, relying on polymyxin combinations with other antibiotics. We are clearly missing new active agents against XDRAB.

Prevalence of digestive tract colonization of carbapenem-resistant Acinetobacter baumannii in hospitals in Saudi Arabia.

Carbapenem-resistant Acinetobacter baumannii is a major health problem worldwide, especially in intensive care units (ICUs). This study aimed to detect the prevalence of A. baumannii colonization of the gastrointestinal tract of patients admitted to the ICU in two hospitals in Saudi Arabia. In addition, it aimed to characterize the molecular mechanisms of carbapenem resistance in these isolates. From January to June 2014, 565 rectal swab specimens were screened for Acinetobacer strains and carbapenem resistance using CHROMagar Acinetobacter and CHROMagar KPC agar plates, respectively. Organism identification and susceptibility were detected using the Vitek 2 system. A total of 47 Acinetobacter spp. were detected, and 35 were resistant to carbapenem, making the prevalence of Acinetobacter spp. 8.3% (47/565) and carbapenem resistance (6.2%, 35/565). The 47 strains showed remarkable clonal diversity as revealed by PFGE. Using PCR, OXA-51, a chromosomal marker for A. baumannii, was detected in 46 strains. OXA-23 β-lactamase was detected in all 35 carbapenem-resistant A. baumannii. No IMP, VIM, SPM, SIM, GIM, KPC or NDM β-lactamases were detected in these isolates. Thus, OXA-23 was the main mechanism of carbapenem resistance in these isolates. To the best of our knowledge, this is the first study to detect the prevalence of Acinetobacter colonization in the digestive tract of ICU patients in Saudi Arabia. This study revealed the importance of having well-established protocols for early identification of these multidrug-resistant organisms, optimizing infection-control strategies and having active surveillance studies to reduce morbidity, mortality and cost.

Laboratory evaluation of different agar media for isolation of carbapenem-resistant Acinetobacter spp.

The optimal method for surveillance of carbapenem-resistant Acinetobacter spp. (CRAB) is unknown. A collection of CRAB strains (n = 42), carbapenem-susceptible strains (CSAB), and non-Acinetobacter strains (n = 18) was used to evaluate six laboratory surveillance methods: MacConkey (MAC), MAC + 1 μg/ml imipenem (MAC-IPM), minimal salts agar + 1 % acetate (MSA), MSA with IPM disk (MSA-IPM), CHROMagarKPC, and CHROMagar Acinetobacter with CR102 (CHROMAcineto). CHROMAcineto was 100 % sensitive and specific. CHROMagarKPC and MAC-IPM were highly sensitive (>95 %), but their specificity was substantially hampered by the breakthrough growth of CSAB. MSA was unsuitable for CRAB detection. CHROMAcineto is a promising medium for CRAB detection and warrants further clinical evaluation.

Modified CHROMagar Acinetobacter Medium for Direct Detection of Multidrug-Resistant Acinetobacter Strains in Nasal and Rectal Swab Samples

This study aimed to investigate whether CHROMagar Acinetobacter medium (CHROMagar, France) in combination with an antimicrobial supplement (modified CHROMagar Acinetobacter; CHROMagar, France) can be used for detecting and isolating multidrug-resistant Acinetobacter species (MRA) in nasal and rectal surveillance cultures. Nasal and rectal swab samples were collected from patients in an intensive care unit at a teaching hospital. The samples were used to inoculate modified CHROMagar Acinetobacter plates, which were examined after 24 and 48 hr of incubation at 37℃. Their susceptibility against the antimicrobial agents meropenem, imipenem, ciprofloxacin, and amikacin was analyzed using the Etest (bioMerieux, France). A total of 406 paired samples (406 nasal swabs and 406 rectal swabs) were obtained from 226 patients, and 120 samples (28 nasal and 28 rectal cultures, 47 nasal cultures only, and 17 rectal cultures only) yielded MRA. Seventy-five MRA isolates (18.5%) were recovered from the 406 nasal samples, and 45 MRA isolates (11.1%) were recovered from the 406 rectal samples. Of the 120 MRA isolates, 3 (2.5%) were detected only after 48 hr of incubation. The use of modified CHROMagar Acinetobacter together with nasal and rectal swabs and 1-day incubation is an effective surveillance tool for detecting MRA colonization.

Variations of CHROMagar Acinetobacter to detect imipenem-resistant Acinetobacter baumannii–calcoaceticus complex

Acinetobacter baumannii-calcoaceticus complex (ABC) isolates are often multidrug-resistant, including to carbapenems. Chromogenic media can facilitate the rapid detection of Gram-negative bacteria, often with the addition of supplements to a base chromogenic medium to detect resistance. We examined various combinations of available media to detect imipenem resistance among 107 ABC clinical isolates. CHROMagar Orientation, CHROMagar KPC, and CHROMagar Acinetobacter, by itself, with Acinetobacter supplement, with KPC supplement, or CHROMagar Acinetobacter with increasing concentrations (1, 2.5, and 5 ml/l) of a new CR102 supplement, were examined. Sensitivity for the detection of isolates was high (> 98%) for all formulations. Specificity was high for CHROMagar Acinetobacter with 2.5 ml/l and 5 ml/l of the CR102 supplement, at 95.3% and 97.7%, respectively, with positive predictive values of 97% and 98.5%. Negative predictive values of these 2 formulations were 100%. CHROMagar Acinetobacter with the addition of the CR102 supplement at 2.5 ml/l and 5ml/l is highly sensitive and specific for the detection of imipenem-resistant ABC, and may be useful for the rapid detection of imipenem-resistant ABC in clinical samples.