Carbapenem-resistant Acinetobacter species are increasingly recognized as major nosocomial pathogens, especially in patients with critical illnesses or in intensive care. The ability of these organisms to accumulate diverse mechanisms of resistance limits the available therapeutic agents, makes the infection difficult to treat, and is associated with a greater risk of death. In this review, we provide an update on the epidemiology, resistance mechanisms, infection control measures, treatment, and outcomes of carbapenem-resistant Acinetobacter infections.
Acinetobacter ; Acinetobacter baumannii ; Acinetobacter Infections ; Colistin ; Critical Illness ; Drug Therapy ; Epidemiology ; Humans ; Infection Control ; Critical Care

Acinetobacter Infections ; diagnosis ; therapy ; Acinetobacter baumannii ; Child ; Drug Resistance, Bacterial ; Humans

Acinetobacter baumannii has emerged as one of the leading bacteria for nosocomial infections, especially in burn wards and ICUs. The bacteria can easily form biofilm and readily attach to abiotic and biotic surfaces, resulting in persistent biofilm-mediated infections. Being surrounded by self-produced extracellular polymeric substance (EPS), the microorganisms in biofilm can acquire protective property against detrimental environment and their tolerance toward antibiotics is increased. Poly-β-1-6-N-acetylglucosamine (PNAG), the common constituent of EPS in Acinetobacter baumannii, acts as the key virulence factor and plays a crucial role in biofilm formation process. This review describes the properties and functions of the PNAG and its influence on biofilm formation and drug resistance of Acinetobacter baumannii.
Acinetobacter Infections ; drug therapy ; Acinetobacter baumannii ; drug effects ; Anti-Bacterial Agents ; therapeutic use ; Biofilms ; drug effects ; growth & development ; Burns ; Cross Infection ; Drug Resistance, Multiple, Bacterial ; beta-Glucans ; metabolism

OBJECTIVETo analyze the clinical characteristics and antibiotic resistance in children with invasive Acinetobacter baumannii infection (IABI).

METHODSA retrospective analysis was performed on the clinical and drug sensitivity data of 52 children with IABI between January 2004 and December 2011.

RESULTSOf the 52 children with IABI, 35 (67%) were less than one year old and 35 (67%) had IABI in the summer and autumn, 19 (37%) of these children were clinically diagnosed with septicemia, 16 (31%) with urinary tract infection, and 12 (23%) with skin and soft tissue infection, and 38 (73%) of them suffered from underlying diseases. The incidence rates of hospital-acquired and community-acquired IABIs were 90% and 10% respectively; 44 cases (85%) were cured or showed improvement in symptoms, and 8 cases (15%) died. All the IAB strains isolated from these children were sensitive to amikacin, 82% of them were sensitive to imipenem, more than 70% were sensitive to fluoroquinolone and to cefoperazone/sulbactam, 13% were sensitive to cefoperazone, 8% were sensitive to aztreonam, 21% developed multidrug resistance, and 17% developed pan-drug resistance.

CONCLUSIONSIABI occurs more frequently in children under one year of age, and most children with IABI have underlying diseases. IABI mainly results in septicemia, urinary tract infection and skin and soft tissue infection and is mostly hospital-acquired. Multi-drug resistance and pan-drug resistance are severe in IAB strains.

Acinetobacter Infections ; drug therapy ; Acinetobacter baumannii ; Adolescent ; Child ; Child, Preschool ; Drug Resistance, Microbial ; Drug Resistance, Multiple, Bacterial ; Female ; Humans ; Infant ; Infant, Newborn ; Male ; Prognosis ; Retrospective Studies

No abstract available.
Acinetobacter/*isolation & purification ; Acinetobacter Infections/*drug therapy/*microbiology ; Anti-Bacterial Agents/*therapeutic use ; Cross Infection/*microbiology/*therapy ; Female ; Humans ; Male ; Meningitis, Bacterial/*drug therapy/*microbiology ; Staphylococcal Infections/*drug therapy/*microbiology ; Staphylococcus/*isolation & purification

BACKGROUND: Despite increasing importance of Acinetobacter baumannii in nosocomial infections and rapid development of multi-antimicrobial resistance in this strain, the resistance mechanisms of beta-lactam antimicrobials in A. baumannii were not clearly defined. In order to observe the resistance mechanisms against beta-lactams and carbapenem, we characterized the production of beta-lactamases and outermembrane protein (OMP) profiles for the 44 clinical isolates of A. baumannii. METHODS: The MICs of antimicrobials were determined by agar dilution test. The secondary beta-lactamases were characterized by isoelectric focusing, polymerase chain reactions and nucleotide sequencing, and the production of chromosomal beta-lactamases was quantitated by spectrophotometric method. For two strains with an elevated MIC of carbapenem, outermembrane protein (OMP) profile was analyzed by ultracentrifugation of the sonicated bacteral cells and SDS-PAGE. RESULTS AND CONCLUSION: Twenty two or 4 of 44 strains produced TEM-1-like beta-lactamase or PER-1 extended-spectrum beta-lactamase, respectively. However, when we analyzed the MICs of several beta-lactams with the beta-lactamase production, the resistance level of beta-lactam was mainly determined by the production of chromosomal beta-lactamase, not by the secondary beta-lactamases in the clinical isolates of A. baumannii. In two strains with an elevated MIC of imipenem, a decrease or loss of about 35 kDa and 22 kDa proteins in OMP was observed, which suggested that the change of OMP played a role in carbapenem resistance.
Acinetobacter/*drug effects/isolation & purification/metabolism ; Acinetobacter Infections/drug therapy/microbiology ; Antibiotics, Lactam/*pharmacology ; Bacterial Outer Membrane Proteins/biosynthesis ; Carbapenems/pharmacology ; Cross Infection/drug therapy/microbiology ; Drug Resistance, Bacterial ; Human ; beta-Lactamases/biosynthesis

OBJECTIVETo analyze clinical characteristics and therapy of pan-resistant Acinetobacter baumannii (PDRAB) infection and explore the methods for effective therapy and prevention of this infection.

METHODSNine hospitalized patients with PDRAB infection confirmed by pathogen and susceptibility testing were analyzed for the risk factors and the treatment outcomes were assessed by case analysis.

RESULTSPDRAB infections occurred mainly in patients with severe complications, most of whom had complications by diabetes or hypertension or damaged mucosal integrity due to mechanical ventilation, surgery and catheterization. The polymyxin sensitivity were 100% for these infections, but all the bacteria identified showed a antimicrobial resistance rates of 100%. The majority of the infections were acquired during hospitalization occurring mainly in the lungs; all the patients had prolonged hospitalization and received antibiotic treatments with high proportions of broad-spectrum antimicrobial agents especially third-generation cephalosporins and quinolones. Exclusive or sequential use of carbapenems and sulbactam in combination with quinolone or aminoglycoside produced favorable effects.

CONCLUSIONSThe prevalence of hospital-acquired pan-resistance of PDRAB infections increased significantly in recent years, particularly in patients with high risk factors. The widespread use of broad-spectrum antibiotics may have some relevance to drug resistant occurrence. The application of carbapenems or sulbactam, or their sequential use, in combination with other agents may produce good effects.

Acinetobacter Infections ; drug therapy ; microbiology ; Acinetobacter baumannii ; drug effects ; Anti-Infective Agents ; therapeutic use ; Cross Infection ; drug therapy ; microbiology ; Drug Resistance, Multiple, Bacterial ; Humans ; Microbial Sensitivity Tests ; Middle Aged

Acinetobacter has been the major pathogen of nosocomial infection. With the wide use of carbapenems, the emergence of multi-resistant isolates especially those resistant to carbapenem, brings a great problem to clinical treatment. The production of inactive enzymes is the main mechanism for antibiotic resistance, particularly the production of carbapenemases mediated by chromosome or plasmid. Combinations of β-lactam antibiotics and sulbactam may show synergism or partial synergism for acinetobacter isolates.
Acinetobacter ; drug effects ; enzymology ; Acinetobacter Infections ; drug therapy ; Anti-Bacterial Agents ; pharmacology ; therapeutic use ; Bacterial Proteins ; metabolism ; Carbapenems ; pharmacology ; therapeutic use ; Drug Resistance, Bacterial ; Microbial Sensitivity Tests ; beta-Lactamases ; metabolism

OBJECTIVETo investigate antibiotic resistance, clonal relatedness and carbapenemase genotype among carbapenem-resistant Acinetobacter baumannii collected from 3 comprehensive hospitals in Ningbo city, Zhejiang province.

METHODS28 strains of carbapenem resistant Acinetobacter baumannii were collected from Ningbo Li Hui-li Hospital, Ningbo Li Hui-li Hospital, Ningbo First Hospital, and N ingbo Second Hospital. The minimum inhibitory concentrations (MIC) of these strains were examined by agar dilution and E-test method. Homology of these isolates was analyzed by pulse-field gel electrophoresis (PFGE) and Genotype of carbapenemases were analyzed by PCR and verified by DNA sequencing.

RESULTS28 strains of Acinetobacter baumanii were highly resistant to all of the antibiotics except polymyxin E. They were classified into 4 clones based on PFGE pattern. Clone A and B had been spreading widely. All of the 28 strains produced carbapenemases which were confirmed as OXA-23 by PCR and sequencing. Metallo-beta-lactamase was not detected in any of the isolates.

CONCLUSIONAll of t hecarbapenem-resistant Acinetobacter baumannii collected from Ningbo were producing OXA-23 carbapenemase, suggesting that the transmission of clones had occurred in the 3 hospitals.

Acinetobacter Infections ; drug therapy ; epidemiology ; Acinetobacter baumannii ; drug effects ; genetics ; metabolism ; Bacterial Proteins ; genetics ; China ; Drug Resistance, Microbial ; Genotype ; Hospitals ; Humans ; Molecular Epidemiology ; Polymerase Chain Reaction ; beta-Lactamases ; genetics

OBJECTIVETo analyze the detection, drug resistance, and status of infection of Acinetobacter baumannii (AB) in burn ICU during 3 years.

METHODSA total of 2 010 specimens of wound secretion, blood, venous catheter attachment, sputum, stool and urine were collected from 505 burn patients hospitalized in our burn ICU from January 2011 to December 2013, and bacterial culture was performed. Pathogens were identified by automatic microorganism identifying and drug sensitivity analyzer. Drug resistance of all the obtained AB to 16 antibiotics commonly used in clinic, including cefoperazone/sulbactam, polymyxin, etc., was tested with K-B paper disk diffusion method. Patients with AB infection were ascertained. The WHONET 5.6 software was used to analyze the distribution of pathogens during 3 years, the isolation of AB with different sources and the status of drug resistance of AB to 16 antibiotics each year, and the status of patients with AB infection, and their outcome.

RESULTSA total of 961 strains of pathogens were isolated, among which 185 (19.25%) strains were Gram positive cocci, 728 (75.75%) strains were Gram negative bacilli, and 48 (4.99%) strains were fungi. A total of 172 strains of AB were isolated, ranking the second place among all the detected pathogens, with 67 (38.95%) strains from wound secretion, 11 (6.40%) strains from blood, 23 (13.37%) strains from venous catheter attachment, and 71 (41.28%) strains from sputum, no AB strain was isolated from feces or urine. The AB strains were found sensitive to polymyxin and with relatively low drug resistance rate to minocycline, while the drug resistance rates were over 80.0% to the other 14 antibiotics commonly used in clinic in 2013. AB culture of wound secretion was positive in 27 patients. Among them, 7 patients suffered from wound infection, and the wound infection was caused by AB in 1 out of the 7 patients. AB culture of blood was positive in 7 patients. Among them, 3 patients suffered from bloodstream infection, and the infection was due to AB invasion in 1 out of the 3 patients. AB culture of venous catheter attachment was positive in 20 patients. Among them, 8 patients suffered from bloodstream infection, and the infection was due to AB invasion in 1 out of the 8 patients. AB culture of sputum was positive in 35 patients. Among them, 13 patients suffered from ventilatory associated pneumonia, and 2 out of the 13 patients were diagnosed as AB infection. A total of 69 patients were AB culture positive, among them 64 patients were cured, 2 patients were transferred to other hospitals, and 3 patients died, with the mortality rate of 4.35%.

CONCLUSIONSAB in our burn ICU has a high detection rate and extensive drug resistance in above-mentioned 3 years. However, AB was mainly colonized in patients with extensive burns with a low mortality rate.

Acinetobacter Infections ; drug therapy ; epidemiology ; microbiology ; Acinetobacter baumannii ; drug effects ; isolation & purification ; Anti-Bacterial Agents ; pharmacology ; Burns ; microbiology ; Cross Infection ; Drug Resistance ; Gram-Negative Bacteria ; isolation & purification ; Humans ; Intensive Care Units ; Microbial Sensitivity Tests