Nosocomial Isolates Of Acinetobacter Baumannii Research Articles

Plasmid-Mediated Class 1 and 2 Integron Carriage in Drug-Resistant Nosocomial Isolates of Acinetobacter baumannii

Background: Acinetobacter baumannii is an opportunistic multidrug-resistant pathogen associated with nosocomial infections in critically ill patients. Antibiotic resistance genes are often encoded by class 1 and 2 integrons and located on plasmids that can facilitate their horizontal transfer among bacteria. Objectives: The aim of this research was to study the correlation between plasmid carriage and presence of class 1 and 2 integrons in nosocomial isolates of A. baumannii. Methods: Fifty isolates collected between October 2014 and March 2015 from Imam Hussein hospital in Tehran were examined. Bacterial identification was carried out by biochemical identification as well as detection of the blaOXA-51 gene among the isolates. Susceptibility to 18 antibiotics was determined by disc diffusion method. Class 1 and 2 integrons were detected in total DNA extracts as well as in isolated plasmids using specific primers and PCR. Results: All isolates were extremely drug-resistant (XDR). Integron carriage was observed in 32 isolates (64%). Seventeen isolates (34%) carried plasmids with molecular sizes of > 20 kbp. Among them, six (35.4%) carried class 1, three (17.6%) harbored class 2, four (23.5%) had both integron classes, and four isolates (23.5%) carried no integrons. Of the plasmid negative isolates, 14 (42.4%) had no integron, 10 (30.3%) carried integron 2, five (15.2%) harbored integron 1 and interestingly, four (12.1%) carried both integron classes. Conclusions: No correlation was found between antibiotic resistance profiles and integron carriage. Class 1 integron was significantly associated with plasmid carriage showing its role in the dissemination of drug resistance in A. baumannii. No association was observed between class 2 integrons and plasmid carriage suggesting their chromosomal location.

Virulence profiles and innate immune responses against highly lethal, multidrug-resistant nosocomial isolates of Acinetobacter baumannii from a tertiary care hospital in Mexico.

Virulence profiles and innate immune responses were studied in Acinetobacter baumannii from nosocomial infections collected over one year in a tertiary care hospital in Mexico. A. baumannii were identified by VITEK 2 System followed by susceptibility tests. Carbapenemase genes, active efflux mechanism to imipenem and meropenem and outer membrane proteins profile were analyzed to evaluate their role on the activity of carbapenem resistance. All isolates were genotyped by pulsed field gel electrophoresis. The ability to form biofilm was determined on a polystyrene surface. The resistance to complement was determined with a pooled human normal serum and TNFα release by infected macrophages was determined by ELISA. The 112 isolates from this study were associated with a 52% of mortality. All were resistance to β-lactams, fluoroquinolones, and trimethroprim-sulfamethoxal, 96 and 90% were resistant to meropenem and imipenem, respectively, but with high susceptibility to polymyxin B, colistin and tigecyclin. Isolates were classified in 11 different clones. Most isolates, 88% (99/112), were metallo-β-lactamases and carbapenemases producers, associated in 95% with the presence of blaOXA-72 gene. Only 4/99 and 1/99 of the carbapenem-resistant isolates were related to efflux mechanism to meropenem or imipenem resistance, respectively. The loss of expression of 22, 29, and/or 33-36-kDa proteins was detected in 8/11 of the clinical isolates with resistance to carbapenem. More than 96% (108/112) of the isolates were high producers of biofilms on biotic surfaces. Finally, all isolates showed variable resistance to normal human serum activity and were high inductors of TNFα release by macrophages. In summary, these results suggest that multidrug-resistant A. baumannii can persist in the hospital environment through its ability to form biofilms. The high mortality observed was due to their ability to survive normal human serum activity and capability to induce potent inflammatory immune response making this nosocomial pathogen a serious threat to hospitalized patients.

Antibacterial effects of cinnamon oil against carbapenem resistant nosocomial Acinetobacter baumannii and Pseudomonas aeruginosa isolates

Widespread existence of drug-resistant pathogens poses a threat to the successful treatment of bacterial diseases and increases the need for new antibacterial agents. Natural products are the basic source of antibacterial therapeutic agents for now, and will remain so in the future. Therefore, the aim of this study was to determine the antibacterial activity of cinnamon oil against carbapenem-resistant nosocomial isolates of Acinetobacter baumannii (111) and Pseudomonas aeruginosa (136). The essential oil composition of cinnamon oil was analyzed by GC, GC/MS and the antimicrobial effect of cinnamon oil was determined by disk diffusion method. The observed zone diameters were compared with carbapenem breakpoints (CLSI standard) and it was found that only one of the P. aeruginosa isolates was within resistance limits. Thus, cinnamon oil has antimicrobial activity with potential use as an antimicrobial agent in the pharmaceutical industry and an additive in the food industry.

Investigation of sulbactam sensitivity rates in nosocomial Acinetobacter baumannii isolates by E-test

of their local antimicrobial susceptibility patterns. The aim of the present prospective study was to determine the aetiology and antimicrobial susceptibility of uropathogens in culture-positive, in women seen at primary health care settings with acute uncomplicated cystitis. Methods & Materials: This prospective study investigated consecutive adult’s women presenting with suspected acute uncomplicated cystitis to primary health care clinics in Rwanda, over a 6-months period between 2 February 2011 and 20 July 2011. Results: Of the total215 mid-stream urine samples, 57 (26.5%) pure significant bacterial growths were isolated and Escherichia coli was the most common isolate (87.7%). %). E. coli isolates exhibited an excellent susceptibility to ceftriaxone (100%), followed by ciprofloxacin (94%) and nitrofurantoin (94%); however, only 28% of E. coli isolates were susceptible to trimethoprimsulfamethoxazole. Conclusion: Uncomplicated cystitisis a common problem among healthy adult women, occurring in about 26% of the study population. Nitrofurantoin or ciprofloxacin may be considered as drugs of choice for empirical antimicrobial agent for acute uncomplicated cystitis at primary health settings in Rwanda.

Genetic linkage of blaNDM among nosocomial isolates of Acinetobacter baumannii from a tertiary referral hospital in northern India

The aim of this study was to evaluate the emergence of blaNDM-1 among clinical isolates of Acinetobacter baumannii isolated from a north Indian tertiary care hospital and to assess the gene cassettes and resistance determinants located within them. In total, 74 A. baumannii were screened for MBL production by the imipenem–EDTA method and were characterised for antibiotic sensitivity. PCR was performed to detect the presence of blaNDM and the co-existence of ESBL and AmpC genes. NDM-producing isolates were typed by ERIC-PCR, and the association of integrons with blaNDM-1 and the presence of gene cassettes were determined using specific primers. The genetic location of blaNDM in ISAba125 was also determined. Transformation was performed using a heat-shock method. Three isolates were found to harbour blaNDM, all of which co-produced blaEBC, blaDHA and blaCIT AmpC β-lactamases. All MBL-producers showed resistance to cephalosporins, carbapenems, aminoglycosides, fluoroquinolones and tigecycline but were susceptible to polymyxin B. Presence of class 1 integrons was demonstrated in all three blaNDM-harbouring isolates, whilst linkage between the integron and blaNDM could not be established. Detection of gene cassettes revealed the presence of dihydrofolate reductase (dhfr) and aminoglycoside 6′-N-acetyltransferase [aac(6′)] genes. Presence of blaNDM in ISAba125 was also observed. These findings suggest that ISAba125 appears to be the main genetic component for dissemination of blaNDM in A. baumannii. The association of blaNDM-1 with ISAba125 and the mobility of other multiresistance region (gene cassette)-carrying integrons provide an easy way to cross species barriers and reach a level that places the patients at risk.

Variable Resistance Patterns of Integron-Associated Multidrug-ResistantAcinetobacter baumanniiIsolates in a Surgical Intensive Care Unit

Between 1998 and 2000, we characterized 91 nosocomial isolates of Acinetobacter baumannii by antibiotyping and genotyping. A total of 25 ribotypes were obtained among these 91 isolates. When the isolates from surgical intensive care units (ICUs) and other wards were compared, multiresistant A. baumannii isolates with the same ribotype 25 (R-25) were significantly more prevalent in nosocomial infections among the surgical patients. Further subtyping of the strains by pulsed-field gel electrophoresis confirmed that strains of the same ribotype in surgical ICUs and a few isolates from other wards were identical or clonally related. Different antibiotic resistance profiles were observed among these R-25 isolates. All R-25 isolates contained intI1 integrase, and two clusters of integron cassettes were found. These clusters of cassettes were encoded by an open reading frame (ORF) of -5'CS-aac(3)Ia-aadA1a-unknown or f-3'CS or 5'CS-aacA4-aadA1-catB8-3'CS, indicating the involvement of different resistant genes. Two isolates contained bla (IMP-1), which was acquired from a conjugatively transferable plasmid and did not involve integron-associated resistance. In conclusion, an epidemic of nosocomial infections associated with A. baumannii strains that have different resistance profiles was identified. Resistance profiles can change by a combination of plasmid- and integron-associated acquisition, especially in a unit with high antibiotic selective pressures. Infectious control personnel should be alert to the change in resistance profiles during routine monitoring.

Frequencies and mechanisms of resistance to moxifloxacin in nosocomial isolates of Acinetobacter baumannii.

To compare the in vitro activity of moxifloxacin and ciprofloxacin against 226 nosocomial isolates of Acinetobacter baumannii from 44 hospitals in the UK. MICs of ciprofloxacin and moxifloxacin were determined by Etest. PCR analysis was used to detect chromosomal mutations in the gyrA and parC genes. Isolates resistant to ciprofloxacin and susceptible to moxifloxacin were examined for the ability to generate spontaneous moxifloxacin-resistant isolates. Of 226 isolates, 49.1% were resistant to ciprofloxacin and 39.4% were moxifloxacin-resistant according to BSAC criteria. Approximately 20% of isolates resistant to ciprofloxacin remained susceptible to moxifloxacin. A GyrA mutation at Ser-83 was found in all ciprofloxacin-resistant isolates. Single mutations in both the gyrA and parC genes at codons Ser-83 and Ser-80, respectively, were found in ciprofloxacin- and moxifloxacin-resistant isolates. Isolates that were ciprofloxacin-resistant but moxifloxacin-susceptible generated spontaneous moxifloxacin-resistant mutants when grown on medium containing up to 8x their initial MIC. However, these mutants were not stable and none displayed high-level moxifloxacin resistance. Moxifloxacin retained in vitro activity against some ciprofloxacin-resistant clinical A. baumannii isolates. Mutations in both gyrA and parC were necessary for resistance to moxifloxacin in most isolates of A. baumannii.

Comparative activities of cecropin A, melittin, and cecropin A–melittin peptide CA(1–7)M(2–9)NH 2 against multidrug-resistant nosocomial isolates of Acinetobacter baumannii

The in vitro activity of three polycationic peptides, cecropin A, melittin, and cecropin A–melittin hybrid peptide CA(1–7)M(2–9)NH 2, alone and in combination with various clinically used antimicrobial agents, was investigated against 32 nosocomial isolates of Acinetobacter baumannii. Antimicrobial activities were measured by MIC, MBC and bacterial killing assay. The peptides demonstrated different ranges of inhibitory values: overall, the organisms were more susceptible to CA(1–7)M(2–9)NH 2 (MIC range, 0.25–16 mg/l) than to cecropin A (0.50–32 mg/l) and melittin (0.50–32 mg/l). Synergy was observed when CA(1–7)M(2–9)NH 2 and melittin were combined with β-lactam antibiotics.

Interactions of colistin and rifampin on multidrug-resistant Acinetobacter baumannii

The increased incidence of nosocomial infections by multidrug-resistant Acinetobacter spp creates demand on the application of some combinations of older antimicrobials on that species. The in vitro activities of colistin and of rifampin and of their interaction were tested on 39 nosocomial isolates of Acinetobacter baumannii. All isolates were resistant to ampicillin/sulbactam, to 3 rd and 4 th generation cephalosporins, to amikacin and to ciprofloxacin. MICs were determined by a microdilution technique and interactive studies between 1× or 4× MIC of colistin and rifampin were performed by the time-kill assay. Rifampin was applied at a concentration of 2μg/mL which is equal to its mean serum level. All isolates were inhibited by colistin and only 15.2% by rifampin. Synergy between 1× MIC of colistin and rifampin was detected in 15.4% of isolates at 6 h of growth and in 51.3% of isolates at 24 h of growth. Synergy between 4× MIC of colistin and rifampin was detected in 15.4% of isolates at 6 h of growth and in 66.7% of isolates at 24 h of growth. It is concluded that colistin is highly active on multidrug-resistant Acinetobacter spp and its activity on A.baumannii is increased in the presence of rifampin, so that their administration might be proposed for nosocomial infections by these isolates.

Transferable Antibiotic Resistance in Multiresistant Nosocomial Acinetobacter baumannii Strains from Seven Clinics in the Slovak and Czech Republics

Sixty-seven multiresistant nosocomial Acinetobacter baumannii isolates from patients hospitalized mostly in intensive care units of seven clinics in Slovak and Czech Republic were tested to determine their ability to transfer antibiotic resistance. All isolates were resistant to kanamycin, ticarcillin, cephalothin, cefotaxime, ceftazidime, aztreonam and susceptible to carbapen-ems, sulbactam and ampicillin/sulbactam. Sixty-five out of 67 strains transferred resistance determinants to Escherichia coli K-12 and Proteus mirabilis P-38 recipients. Analysis of selected transconjugants by an indirect selection method showed a more variable pattern of transferred resistance determinants. The clonal spread of strains transferring resistance seems to be an additional risk for occurrence of strains resistant to ceftazidime and aztreonam.

Comparative activities of polycationic peptides and clinically used antimicrobial agents against multidrug-resistant nosocomial isolates of Acinetobacter baumannii.

The in vitro activity of buforin II, cecropin P1, indolicidin, magainin II and ranalexin, alone and in combination with eight clinically used antimicrobial agents was investigated against 12 multidrug-resistant strains of Acinetobacter baumannii isolated from immunocompromised patients. Antimicrobial activities were measured by MIC, MBC and viable count. The peptides had a varied range of inhibitory values: overall, the organisms were more susceptible to buforin II (MIC range 0.25-16 mg/L), cecropin P1 (0.50-32 mg/L) and magainin II (0.50-16 mg/L). Synergy occurred when magainin II was combined with beta-lactam antibiotics.

Correlation of six methods for typing nosocomial isolates of Acinetobacter baumannii

A comparative study of biotyping, antimicrobial susceptibility, whole-cell protein analysis, plasmid analysis, pulsed-field gel electrophoresis of chromosomal DNA and polymerase chain reaction with arbitrary primers of Acinetobacter baumannii isolates from three large hospitals was performed to determine the best markers for epidemiological purposes. Ninety-two isolates were included: 38 belonged to a previously described outbreak and 54 were randomly selected from sporadic cases of infection. Biotyping, whole-cell protein and plasmid analysis were the least discriminatory methods, whereas antimicrobial susceptibility and polymerase chain reaction with arbitrary primers showed moderate discriminatory power. Typing based on pulsed-field gel electrophoresis of chromosomal DNA appeared to be the best discriminatory method (discrimination index of 0.9623). The addition of polymerase chain reaction with arbitrary primers or antimicrobial susceptibility to pulsed-field gel electrophoresis of chromosomal DNA did not further increase the discriminatory power.