Imipenem-resistant Acinetobacter Baumannii Research Articles

Nationwide surveillance of antimicrobial resistance among non-fermentative Gram-negative bacteria in Intensive Care Units in Taiwan: SMART programme data 2005

A nationwide surveillance of the antimicrobial susceptibilities of glucose non-fermentative Gram-negative bacteria isolates was conducted from 1 September 2005 to 30 November 2005 in Taiwan. A total of 456 isolates were recovered from patients hospitalised in the Intensive Care Units (ICUs) of ten major teaching hospitals. Rates of resistant pathogens, such as ciprofloxacin-resistant Pseudomonas aeruginosa (19%) and imipenem-resistant Acinetobacter baumannii (25%), were higher than those reported in 2000 (8% and 22%, respectively). Increased rates of isolates with resistant phenotypes correlated with prolonged length of ICU stay (48 h to ≤7 days vs. >7 days) for ceftazidime-non-susceptible P. aeruginosa (20.0% and 29.7%, respectively), imipenem-non-susceptible P. aeruginosa (4.0% and 13.5%, respectively) and imipenem-non-susceptible A. baumannii (15.4% and 29.8%, respectively), but not for ciprofloxacin-resistant P. aeruginosa. Alarming rates of emergence of extensively drug-resistant (XDR) A. baumannii (15%) and XDR P. aeruginosa (1.8%) were found, particularly among those isolates that were not susceptible to tigecycline and colistin. Interhospital dissemination of some clones of XDR A. baumannii in different ICUs was also noted. This study illustrates the crucial nature of continuous nationwide surveillance of resistant pathogens and implementation of effective strategies for ICU infection control and antibiotic restriction.

Abstracts of the Tissue Viability Society Annual Meeting, Peterborough, 2008

This study describes an outbreak caused by imipenem-resistant Acinetobacter baumannii (IRAB) involving 2 general wards at the Penghu branch of Tri-Service General Hospital.Clinical data obtained from the patients with IRAB during an outbreak from May 2014-October 2014 were reviewed. Microbiologic sampling from the environment and the hands of health care workers (HCWs) was performed. Clinical isolates from case patients were genotyped using pulsed-field gel electrophoresis (PFGE).During the outbreak period, 12 patients were colonized or infected with IRAB. The hospital room environments of the case patients were contaminated with IRAB. Hands of nurses and physicians were not colonized with IRAB, but the hands of 2 bedside caregivers of case patients were colonized with IRAB. The PFGE analysis revealed that at least 2 major genetically distinct strains disseminated between 2 different wards. After implementation of infection control measures with a cohort of nursing patients, hand hygiene education for caregivers who had not received instructions before the outbreak, and a critical value alert system to notify case patients, the outbreak was controlled successfully.This outbreak study highlights the importance of adherence to hand hygiene by all HCWs to prevent the dissemination of multidrug-resistant organisms.

Identification of an atypical integron carrying an IS 26-disrupted aadA1 gene cassette in Acinetobacter baumannii

An unusual class 1 integron was identified that carries an IS 26-disrupted aadA1 gene cassette (designated as ‘integron-IS 26’) in an imipenem-resistant Acinetobacter baumannii (IRAB) outbreak strain. DNA sequencing revealed that integron-IS 26 contained two gene cassettes, the aac(6’)-Im cassette and a peculiar aadA1 cassette that was disrupted by IS 26 (disrupted aadA1 cassette). Southern blotting localised integron-IS 26 to the chromosome. Nested polymerase chain reaction (PCR) was performed to define the frequency of integron-IS 26 in five groups of bacteria. Nested PCR identified integron-IS 26 in 19 (73.1%) of 26 clinical outbreak strains of IRAB, 10 (100%) of 10 IRAB isolated from environmental cultures, 3 (13.0%) of 23 imipenem-susceptible A. baumannii (ISAB) non-outbreak strains, 1 (3.6%) of 28 netilmicin- and tobramycin-resistant A. baumannii and none of the netilmicin- and tobramycin-resistant Pseudomonas aeruginosa. In conclusion, we have identified a novel class I integron that carries the aac(6’)-Im cassette and an IS 26-disrupted copy of aadA1 (integron-IS 26) in most IRAB outbreak strains and in a few ISAB non-outbreak control strains. Integron-IS 26 is located chromosomally.

Clinical and epidemiological characterization of infections due to imipenem resistant Acinetobacter baumannii at the university hospital Sahloul, Tunisia

to characterize epidemiological and clinical features related to the multi-drug Acinetobacter baumannii infections in the university hospital Sahloul in Tunisia. retrospective study including twenty-four imipenem resistant Acinetobacter baumannii isolated from twenty patients hospitalized in different wards of the hospital. Study of clinical features related to the infection by multi-drug Acinetobacter baumannii, bacterial identification by classical identification scheme, antibiotic susceptibilities were determined by the disk diffusion method; genotyping was performed by arbitrarily-primed PCR. the most incriminated ward was the intensive care unit with a high prevalence of septicaemia. All studied strains were multi-drug to all beta-lactams tested. Genotyping has shown the clonality of studied strains. Features incriminated in the acquisition of infection were essentially immunodeficiency, invasive manoeuvring and antibiotherapy. multidrug Acinetobacter baumannii is increasingly isolated in our hospital. Rational use of antibiotics and rigorous application of hygienic rules could contribute to limit dissemination of such strains.

Dissemination of imipenem-resistant Acinetobacter baumannii strains carrying the ISAba1–bla OXA-23 genes in a Chinese hospital

An outbreak of 95 clinical infections with imipenem-resistant Acinetobacter baumannii in a Chinese hospital was investigated and the carbapenemase-encoding genes and their relationship with ISAba1 of these and a further 16 isolates recovered from the intensive care unit (ICU) environment were analysed. Almost all isolates were resistant to a wide range of antimicrobials; the lowest resistance rates were found for polymyxin E (17.1 %), cefoperazone/sulbactam (30.6 %) and ampicillin/sulbactam (67.6 %). Six pattern types defined by DNA macrorestriction patterns were distinguished among the clinical isolates with dissemination of pattern A (50 isolates) to patients in seven hospital units and pattern B (35 isolates) to eight units; the environmental isolates from ICUs were also of pattern A. All isolates were positive for the bla(OXA-66) and bla(OXA-23) genes. The OXA-23-encoding gene was located 34 bp downstream of ISAba1. No plasmids were detected and conjugal transfer of resistance was not demonstrated. The bla(OXA-23) probe hybridized with 200 and 220 kb ApaI chromosomal fragments for type patterns A and B, respectively.

Widespread occurrence of aminoglycoside resistance due to ArmA methylase in imipenem-resistant Acinetobacter baumannii isolates in China

Widespread occurrence of aminoglycoside resistance due to ArmA methylase in imipenem-resistant Acinetobacter baumannii isolates in China

Risk factors for nosocomial imipenem-resistant Acinetobacter baumannii infections

To identify the risk factors for nosocomial imipenem-resistant Acinetobacter baumannii (IRAB) infections. A prospective case-control study, set in an 1100-bed referral and tertiary-care hospital, of all patients who had nosocomial A. baumannii infections between January 1 and December 31, 2004. Only the first isolation of A. baumannii was considered. IRAB was isolated from 66 (53.7%) patients and imipenem-sensitive Acinetobacter baumannii (ISAB) was isolated from 57 (46.3%) patients during the study period. The mean duration of hospital stay until A. baumannii isolation was 20.8+/-13.6 days in IRAB infections, whereas it was 15.4+/-9.4 days in ISAB infections. Of the patients, 65.2% with IRAB infections and 40.4% with ISAB infections were followed at the intensive care unit (ICU). Previous carbapenem use was present in 43.9% of the patients with IRAB and 12.3% of the patients with ISAB infection. In univariate analysis female sex, longer duration of hospital stay until infection, ICU stay, emergent surgical operation, total parenteral nutrition, having a central venous catheter, endotracheal tube, urinary catheter or nasogastric tube, previous antibiotic use, and previous administration of carbapenems were significant risk factors for IRAB infections (p<0.05). In multivariate analysis, longer duration of hospital stay until A. baumannii isolation (odds ratio (OR) 1.043; 95% confidence interval (CI) 1.003-1.084; p=0.032), previous antibiotic use (OR 5.051; 95% CI 1.004-25.396; p=0.049), and ICU stay (OR 3.100; 95% CI 1.398-6.873; p=0.005) were independently associated with imipenem resistance. Our results suggest that the nosocomial occurrence of IRAB is strongly related to an ICU stay and duration of hospital stay, and that IRAB occurrence may be favored by the selection pressure of previously used antibiotics.

In vitro Antimicrobial Synergy against Imipenem-Resistant Acinetobacter baumannii

Most imipenem-resistant Acinetobacter baumannii (IRAB) isolates are multiresistant, leaving few options for an effective antimicrobial therapy. We purposed to select possible candidates for the combinations of antimicrobials that are synergistic in vitro for inhibitory or bactericidal activities against IRAB and evaluate the usefulness of double disk synergy test (DDS) in predicting synergistic bactericidal activity. Fifty-five IRAB isolates recovered from patients during the period from August 1999 to November 2000 were tested for susceptibilities to amikacin, gentamicin, tobramycin, piperacillin, piperacillin/tazobactam, cefotaxime, cefepime, cefoperazone/sulbactam (C/S), imipenem, meropenem, ciprofloxacin, levofloxacin, trimethoprim/sulfamethoxazole, chloramphenicol, minocycline, and colistin by the Clinical and Laboratory Standard Institute agar dilution method. Three isolates showing different susceptibility profiles were tested for antimicrobial synergy by DDS and then by timekill study (TKS) using DDS-positive combinations. Colistin, C/S, and minocycline were active in 50 (90.9%), 50, and 44 (80.0%) isolates, respectively, and all the other drugs were active in less than 20% of isolates. Minocycline-imipenem, minocycline-C/S, minocycline-amikacin, imipenem-tobramycin, C/S-amikacin, and C/S-tobramycin combinations showed synergistic inhibitory or bactericidal activity by TKS when the same combinations were synergistic in DDS; however, C/S-imipenem was found synergistic on DDS, but not by TKS. Colistin, C/S, and minocycline were relatively active against IRAB. DDS might help predict the synergistic antimicrobial effect of TKS if one of the combinations was susceptible.

Acquisition of imipenem-resistant Acinetobacter baumannii in a pediatric intensive care unit: a case-control study

To investigate the risk factors associated with nosocomial acquisition of imipenem-resistant Acinetobacter baumannii (IRAB) among pediatric intensive care patients. A retrospective case control study was conducted in a pediatric intensive care unit (PICU). Cases were children in whom IRAB was isolated from any clinical specimen obtained at least 48 h following admission to PICU. Controls were children without IRAB matched to cases in 2:1 ratio. Twenty-six cases were matched with 52 controls according to the chronological order of admission. Between July 2001 and December 2003, 52 (62%) of 84 clinical A. baumannii isolates were found nonsusceptible to imipenem (MIC > or = 8 microg/ml). Demographic variables, comorbid conditions, clinical picture at admission, invasive procedures, use of antimicrobials and other drugs were analyzed as potential risk factors. Use of carbapenems and other beta-lactams, aminoglycosides, ranitidine, mechanical ventilation, central venous or urinary catheters and length of stay in PICU were among the factors significantly associated with IRAB acquisition in the univariate analysis. By multivariate analysis, however, only aminoglycoside use and length of stay in the PICU were independent risk factors. Acquisition of IRAB by PICU patients was independently associated with aminoglycoside use and prolonged stay in the unit. Studies of evaluation of infection control policies need to be pursued.

Multicenter pilot survey of resistant bacteria in the Mediterranean area

With the aim of testing the feasibility of a multiresistant bacteria (MRB) surveillance methodology and evaluating the level of antimicrobial resistance and dissemination of resistant pathogens in the Mediterranean area, a pilot study was carried out in nine university hospitals in Algeria, Tunisia and France. The results indicate that third-generation cephalosporin-resistant Enterobacteriaceae comprise the major MRB in Algerian and Tunisian hospitals. In France, the highest incidence rates were found for methicillin-resistant Staphylococcus aureus, while in Tunisian hospitals, imipenem-resistant Acinetobacter baumannii seems to be a particularly prevalent organism. Although the data were not representative of the participating countries as a whole, the results show the importance and ubiquity of the problem in the area and the feasibility of surveillance.

Outbreak of multiple clones of imipenem-resistant Acinetobacter baumannii isolates expressing OXA-58 carbapenemase in an intensive care unit

To investigate the resistance mechanisms and the genetic relationship of imipenem-resistant Acinetobacter baumannii isolates recovered in the intensive care unit (ICU) of a tertiary care hospital. Imipenem-resistant A. baumannii clinical and environmental isolates were collected in the ICU of the Red Cross General Hospital, Athens, Greece between March and October 2002. The isolates were tested by Etest MBL, PCR, RT-PCR and sequencing for carbapenemase-encoding genes, PFGE and synergy experiments using meropenem and the efflux pump inhibitor carbonyl cyanide chlorophenylhydrazone. During the study period, 15 clinical and two environmental imipenem-resistant (MIC 8 to >128 mg/L) A. baumannii isolates were recovered. PFGE showed six different clones that included both clinical and environmental isolates. All 17 isolates were negative by Etest MBL and PCR for genes bla(IMP), bla(VIM), bla(SPM), bla(OXA-23-like) and bla(OXA-24-like). Genes bla(OXA-51-like) and bla(OXA-58-like) were amplified from 15 and 14 isolates, respectively. Sequencing of bla(OXA-51-like) amplicons identified bla(OXA-66) (nine cases) and bla(OXA-69) (six cases), whereas bla(OXA-58-like) sequences were classical bla(OXA-58). Reverse transcriptase-PCR showed that bla(OXA-51-like) genes were expressed in 12 and bla(OXA-58) in 10 isolates; in these isolates, inhibition of OXA enzymes by 200 mM of NaCl reduced carbapenem MICs by up to 4-fold. Overexpression of proton-gradient dependent efflux pumps did not contribute to carbapenem resistance in any isolate. Similarly, although AmpC expression was demonstrated in eight isolates, inhibition of AmpC with cloxacillin did not reduce the MICs of carbapenems significantly. These findings indicate wide dissemination of OXA-58 carbapenemase, which contributes, at least partially, to the imipenem resistance of unrelated A. baumannii isolates in our ICU.

Integron-associated imipenem resistance in Acinetobacter baumannii isolated from a regional hospital in Taiwan

We investigated the genetic properties of imipenem-resistant Acinetobacter baumannii collected from a regional hospital in Taiwan. Pulsed-field gel electrophoresis demonstrated that the isolates were genetically diverse. Polymerase chain reaction, DNA sequencing, and DNA–DNA hybridisation showed that the bla IMP-1 gene resided as a cassette in a plasmid-borne class 1 integron in two isolates. The majority of the resistant isolates were plasmid-less and carried no bla IMP, bla VIM or bla CFI genes, indicating that other uncharacterised metallo-β-lactamases or mechanisms other than enzyme production are involved in carbapenem resistance in this group of A. baumannii. We conclude that multidrug resistance of A. baumannii was a combined effect of lateral gene transfer and clonal spread of multiple resistant clones. Strict measures should be implemented to control the further spread of resistance.

Risk-factors for the acquisition of imipenem-resistant Acinetobacter baumannii in Spain: a nationwide study

Potential risk-factors for the acquisition of imipenem-resistant Acinetobacter baumannii were investigated in a cohort study in 25 Spanish hospitals. The clonal relationship among isolates was determined by pulsed-field gel electrophoresis (PFGE). In total, A. baumannii was isolated from 203 patients, with imipenem-resistant (MIC(90) 128 mg/L) isolates being obtained from 88 patients (43%), and imipenem-susceptible isolates from 115 patients (57%). A wide clonal distribution was observed among the imipenem-resistant isolates, but spread of the same clone among centres was not demonstrated. The results indicated that imipenem-resistant A. baumannii is a widely distributed nosocomial pathogen in Spain and reaches an alarming frequency in some centres. Independent risk-factors for the acquisition of imipenem-resistant A. baumannii were a hospital size of >500 beds (multivariate OR, 6.5; 95% CI, 1.8--23), previous antimicrobial treatment (multivariate OR, 4.3; 95% CI, 1.6--11), a urinary catheter (multivariate OR, 2.7; 95% CI, 1.1--6.7) and surgery (multivariate OR, 2; 95% CI, 1.07--3.8).

Detección de carbapenemasas en clones de Acinetobacter baumannii resistentes a imipenem

The aim of this study was to detect carbapenemases in imipenem-resistant Acinetobacter baumannii isolates obtained in the microbiology department of a Basque Country Public Health Service hospital over a period of 19 months, and to genetically characterize the resistant clones. Susceptibility tests to imipenem, meropenem, ticarcillin, ceftazidime, cefotaxime, cefepime and aztreonam were done by determining the minimum inhibitory concentration on agar plates. A tRNA technique was used for species identification and PCR with primers ERIC2, AP3 and M13 for genetic typing of resistant isolates. Carbapenemase production was detected by the Hodge test and metallo-beta-lactamase by the EDTA test and Etest MBL. A total of 76 isolates were resistant to imipenem and 49 of these were resistant to all the betalactam antibiotics tested. Genetic typing showed three predominant clones, denominated I (9 isolates), II (48 isolates) and III (8 isolates). Hodge and EDTA tests were positive in 45 and 8 isolates belonging to clone II, 8 and 4 belonging to clone I and 7 and 3 belonging to clone III, respectively. The Etest confirmed 7 results (45% of the 17 positive EDTA test isolates). Our results show that one factor contributing to the high level of imipenem resistance in the isolates analyzed is dissemination of a predominant, multiresistant clone able to produce OXA-type carbapenemases and metallo-beta-lactamases.

Risk factors for acquisition of imipenem-resistant Acinetobacter baumannii: a case-control study.

Risk factors for the nosocomial occurrence of imipenem-resistant Acinetobacter baumannii (IRAB) were determined. A case-control study design was used for a comparison of two groups of A. baumannii-positive patients with control patients. Nosocomial IRAB was isolated from the first group of A. baumannii-positive patients, and imipenem-susceptible A. baumannii (ISAB) was isolated from the second group. The control patients were randomly selected in a 4:1 ratio from the same medical or surgical services from which the A. baumannii-positive patients were receiving care when the isolation of IRAB occurred. Risk factors analyzed included demographic variables, comorbid conditions, variables related to hospitalization, and the antimicrobials used. IRAB was isolated from 104 patients, and ISAB was isolated from 387 patients between January and December 2000. The risk factors for IRAB were a previous intensive care unit (ICU) stay (odds ratio [OR], 21.54; 95% confidence interval [CI], 10.73 to 43.23) and prior exposure to imipenem (OR, 9.18; 95% CI, 3.99 to 21.13) or third-generation cephalosporins (OR, 2.11; 95% CI, 1.13 to 3.95). Risk factors for ISAB were a previous ICU stay (OR, 8.05; 95% CI, 5.67 to 11.44) and exposure to third-generation cephalosporins (OR, 2.07; 95% CI, 1.47 to 2.91). Our results suggest that the nosocomial occurrence of IRAB or ISAB is strongly related to an ICU stay, and IRAB occurrence may be favored by the selection pressure of imipenem.

An outbreak of imipenem-resistant Acinetobacter baumannii in critically ill surgical patients.

To describe an outbreak of imipenem-resistant Acinetobacter baumannii (IR-Ab) and the measures for its control, and to investigate risk factors for IR-Ab acquisition. An observational and a case-control study. A surgical intensive care unit (ICU) in a university tertiary care hospital. After admission to the ICU of an IR-Ab-positive patient, patients were prospectively screened for IR-Ab carriage upon admission and then once a week. Environmental cleaning and barrier safety measures were used for IR-Ab carriers. A case-control study was performed to identify factors associated with IR-Ab acquisition. Cases were patients who acquired IR-Ab. Controls were patients who were hospitalized in the ICU at the same time as cases and were exposed to IR-Ab for a similar duration as cases. The following variables were investigated as potential risk factors: baseline characteristics, scores for severity of illness and therapeutic intervention, presence and duration of invasive procedures, and antimicrobial administration. Beginning in May 1996, the outbreak involved 17 patients over 9 months, of whom 12 acquired IR-Ab (cases), 4 had IR-Ab isolates on admission to the ICU, and 1 could not be classified. Genotypic analysis identified two different IR-Ab isolates, responsible for three clusters. Ten of the 12 nosocomial cases developed infection. Control measures included reinforcement of barrier safety measures, limitation of the number of admissions, and thorough environmental cleaning. No new case was identified after January 1997. Eleven of the 12 cases could be compared to 19 controls. After adjustment for severity of illness, a high individual therapeutic intervention score appeared to be a risk factor for IR-Ab acquisition. The outbreak ended after strict application of control measures. Our results suggest that high work load contributes to IR-Ab acquisition.

Making sense of antimicrobial use and resistance surveillance data: application of ARIMA and transfer function models

Making sense of antimicrobial use and resistance surveillance data: application of ARIMA and transfer function models

Pseudo-outbreak of imipenem-resistant Acinetobacter baumannii resulting from false susceptibility testing by a rapid automated system.

Introduction of the Vitek GNS-506 susceptibility testing cards in the Hippokration General Hospital, Thessaloniki, Greece, resulted in an apparently high prevalence of imipenem-resistant Acinetobacter baumannii. When 35 of these isolates were further tested by disk diffusion, broth microdilution, and agar dilution assays, 32 were imipenem sensitive by all tests and three were sensitive or intermediate, depending on the method. The pseudoresistant acinetobacters did not form a genetically homogeneous group. It is suggested that the detection of imipenem-resistant A. baumannii isolates by this system should be confirmed by an additional susceptibility test.

Outer-membrane proteins pattern and detection of β-lactamases in clinical isolates of imipenem-resistant Acinetobacter baumannii from Brazil

In order to compare imipenem-sensitive and -resistant Acinetobacter baumannii strains isolated from three patients, ribotyping, plasmid, β-lactamase detection and outer-membrane analysis were performed. Ribotyping and the use of a β-lactam during the period when the strains were isolated suggested that they had a common origin and that resistance occurred in vivo. Outer membrane analysis showed no difference between susceptible and resistant strains with the exception of an A2 imipenem-resistant strain that lost a protein band of 31–36 kDa. Beta-lactamases were detected using isoelectric focusing in all strains ( pI of 7.4). In addition, two β-lactamases ( pI of 5.9 and 6.7) were found in imipenem-resistant isolates. The double-disc technique demonstrated the presence of a β-lactamase capable of imipenem inactivation in resistant strains. Plasmid analysis showed that all susceptible strains had the same pattern, one resistant strain did not have any plasmid, one had the same plasmid pattern of its susceptible pair and only one had a different pattern when compared with its susceptible pair.

Limitation of Acinetobacter baumannii treatment by plasmid-mediated carbapenemase ARI-2

Acinetobacter species now account for 10% of nosocomial infections in intensive therapy units (ITU) in Europe. They are invariably multiresistant, and one major concern is the increasing incidence of carbapenem-resistant isolates, since these antibiotics are frequently the therapeutic choice for these infections. Carbapenem resistance in South America has already reached levels that significantly influence therapeutic choices (Carlos Bantar, unpublished data), and this looks set to be a problem in some European countries. 1 Tankovic J Legrand P De Gatines G Chemineau V Brun-Buisson C Duval J Characterisation of a hospital outbreak of imipenem-resistant Acinetobacter baumannii by phenotypic and genotypic typing methods. J Clin Microbiol. 1994; 32: 2677-2681 PubMed Google Scholar ARI-1, a plasmid-mediated enzyme capable of hydrolysing imipenem, was the first carbapenemase to be isolated from this genus. 2 Paton H Miles RS Hood J Amyes SGB ARI-1: beta-lactamase-mediated imipenem resistance in Acinetobacter baumannii. Int J Antiomicrob Agents. 1993; 2: 81-88 Summary Full Text PDF PubMed Scopus (220) Google Scholar We report a novel plasmid-mediated carbapenemase (ARI-2) from a multiresistant clinical isolate of A baumannii from Argentina (first described in 1996). 3 Brown S Bantar C Young H-K Amyes SGB An outbreak of imipenem-resistance in Acinetobacter strains from Buenos Aires, Argentina. in: Abstracts of the 36th Interscience Conference on Antimicrobial Agents and Chemotherapy, New Orleans. American Society for Microbiology, Washington, DC1996: 56 Google Scholar