Acinetobacter baumannii is a Gram-negative opportunistic pathogen widely distributed in hospital settings. It can survive for a long time and cause a variety of infections, including pneumonia, septicemia, urinary tract infections, and meningitis. The bacterium demonstrates extensive resistance, particularly to critical antibiotics like carbapenems and polymyxins, posing a serious threat to the recovery of severely ill patients. Carbapenem-resistant A. baumannii has been designated as a pathogen of critical priority on the World Health Organization (WHO) Bacterial Pathogen Priority List, requiring urgent development of new therapeutic agents. Phages, as a novel biological control approach, exhibit substantial potential in combating A. baumannii infections due to their specific ability to infect and lyse bacteria. This review highlights the application and potential of phages and phage-derived enzymes against multidrug-resistant A. baumannii, considering the epidemiological trends of A. baumannii in China, with the aim of providing innovative insights and strategies for phage therapy of drug-resistant bacterial infections.
Acinetobacter baumannii/drug effects* ; Drug Resistance, Multiple, Bacterial ; Phage Therapy/methods* ; Acinetobacter Infections/microbiology* ; Humans ; Bacteriophages/physiology* ; Anti-Bacterial Agents/pharmacology*

BACKGROUND: Ciprofloxacin is usually used in the treatment of lower respiratory tract infections (LRTIs). Recent studies abroad have shown ciprofloxacin is inadequately dosed and might lead to worse outcomes. The aim of this study was to perform pharmacokinetic and pharmacodynamic analyses of ciprofloxacin in elderly Chinese patients with severe LRTIs caused by Gram-negative bacteria. METHODS: From September 2012 to June 2014, as many as 33 patients were empirically administered beta-lactam and ciprofloxacin combination therapy. Patients were infused with 200 or 400 mg of ciprofloxacin every 12 h, which was determined empirically by the attending physician based on the severity of the LRTI and the patient's renal condition. Ciprofloxacin serum concentrations were determined by high-performance liquid chromatography. Bacterial culture was performed from sputum samples and/or endotracheal aspirates, and the minimum inhibitory concentrations (MICs) of ciprofloxacin were determined. The ratios of the area under the serum concentration-time curve to the MIC (AUC/MIC) and of the maximum serum concentration of the drug to the MIC (Cmax/MIC) were calculated. The baseline data and pharmacokinetic parameters were compared between clinical success group and clinical failure group, bacteriologic success group and bacteriologic failure group. RESULTS: Among the 33 patients enrolled in the study, 17 were infected with Pseudomonas aeruginosa, 14 were infected with Acinetobacter baumannii, and two were infected with Klebsiella pneumoniae. The mean age of the patients was 76.9 ± 6.7 years. Thirty-one patients (93.4%) did not reach the target AUC/MIC value of >125, and 29 patients (87.9%) did not reach the target Cmax/MIC value of >8. The AUC/MIC and Cmax/MIC ratios in the clinical success group were significantly higher than those in the clinical failure group (61.1 [31.7-214.9] vs. 10.4 [3.8-66.1], Z = -4.157; 9.6 [4.2-17.8] vs. 1.3 [0.4-4.7], Z = -4.018; both P < 0.001). The AUC/MIC and Cmax/MIC ratios in the patients for whom the pathogens were eradicated were significantly higher than those in the patients without the pathogens eradicated (75.3 [31.7-214.9] vs. 10.5 [3.8-66.1], Z = -3.938; 11.4 [4.2-17.8] vs. 1.4 [0.4-5.4], Z = -3.793; P < 0.001 for both). Receiver operating characteristic curve analysis showed that the AUC/MIC and Cmax/MIC values were closely associated with clinical and bacteriologic efficacies (P < 0.001 in both). CONCLUSIONS Ciprofloxacin is inadequately dosed against Gram-negative bacteria, especially for those with relatively high MIC values. Consequently, the target values, AUC/MIC > 125 and Cmax/MIC > 8, cannot be reached.
Acinetobacter baumannii ; drug effects ; pathogenicity ; Aged ; Aged, 80 and over ; Chromatography, High Pressure Liquid ; Ciprofloxacin ; pharmacokinetics ; pharmacology ; Female ; Gram-Negative Bacteria ; drug effects ; pathogenicity ; Humans ; Male ; Microbial Sensitivity Tests ; Pseudomonas aeruginosa ; drug effects ; pathogenicity ; Respiratory Tract Infections ; drug therapy ; metabolism ; microbiology

BACKGROUNDAcinetobacter baumannii has emerged as an important pathogen causing a variety of infections. Using data from the China Surveillance of Antimicrobial Resistance Program conducted biennially, we investigated the secular changes in the resistance of 2917 isolates of A. baumannii from 2004 to 2014 to differ antimicrobial agents.

METHODSPathogen samples were collected from 17 to 20 hospitals located in the eastern, central, and western regions of China. Minimum inhibitory concentrations (MICs) were determined by a 2-fold agar dilution method, and antimicrobial susceptibility was established using the 2014 Clinical Laboratory Standards Institute-approved breakpoints. Isolates not susceptible to all the tested aminoglycosides, fluoroquinolones, β-lactams, β-lactam/β-lactam inhibitors and carbapenems were defined as extensively drug resistant.

RESULTSThe rates of nonsusceptibility to common antimicrobial agents remained high (>65%) over the years with some fluctuations to certain agents. The prevalence of imipenem-resistant A. baumannii (IRAB) increased from 13.3% in 2004 to 70.5% in 2014 and that of extensively drug-resistant A. baumannii (XDRAB) increased from 11.1% in 2004 to 60.4% in 2014. The activity of tigecycline was stable with MIC90 ≤4 mg/L against A. baumannii from 2009 to 2014. Susceptibility to colistin remained high (97.0%) from 2009 to 2014. The prevalence of XDRAB increased in all the three surveillance regions over the years and was significantly higher in Intensive Care Unit (ICU) wards than non-ICU wards.

CONCLUSIONSThis longitudinal multicenter surveillance program revealed the nationwide emergence of A. baumannii in China and showed a significant increase in prevalence from 2004 to 2014. High levels of bacterial resistance were detected among samples collected from clinical settings in China, with IRAB and XDRAB being especially prevalent. This study will help to guide empirical therapy and identify at-risk groups requiring more intense interventional infection control measures, while also helping to focus surveillance efforts.

Acinetobacter baumannii ; drug effects ; Amikacin ; pharmacology ; Anti-Infective Agents ; pharmacology ; Cefoperazone ; pharmacology ; Ceftazidime ; pharmacology ; Cephalosporins ; pharmacology ; China ; Colistin ; pharmacology ; Drug Resistance, Multiple, Bacterial ; Humans ; Imipenem ; pharmacology ; Levofloxacin ; pharmacology ; Microbial Sensitivity Tests ; Minocycline ; pharmacology ; Penicillanic Acid ; analogs & derivatives ; pharmacology ; Piperacillin ; pharmacology ; Sulbactam ; pharmacology

Acinetobacter baumannii ; drug effects ; Anti-Bacterial Agents ; pharmacology ; Drug Resistance, Multiple, Bacterial ; Microbial Sensitivity Tests

BACKGROUND: Extensively drug-resistant (XDR) Pseudomonas aeruginosa and Acinetobacter baumannii are a threat to hospitalized patients. We evaluated the effects of antimicrobial combinations on XDR P. aeruginosa and A. baumannii isolates. METHODS: P. aeruginosa and A. baumannii isolates, which were resistant to all antibiotics except colistin (CL), were collected from eight hospitals in Korea. Genes encoding metallo-beta-lactamases (MBLs) and OXA carbapenemases were detected by PCR in eight P. aeruginosa and 30 A. baumannii isolates. In vitro synergy of antimicrobial combinations was tested by using the checkerboard method. RESULTS: Minimum inhibitory concentrations of beta-lactams, aminoglycosides, and fluoroquinolones were very high, while that of CL was low for majority of XDR P. aeruginosa and A. baumannii isolates. Antimicrobial combinations including Imipenem (IPM)-CL, ceftazidime (CAZ)-CL, and rifampin (RIF)-CL exerted only additive/indifferent effects on majority of XDR P. aeruginosa isolates. Proportions of XDR A. baumannii isolates that showed synergistic and additive/indifferent inhibition after treatment with antimicrobial combinations used are as follows: IPM-ampicillin-sulbactam (AMS), 17% and 80% isolates, respectively; IPM-rifampin (RIF), 13% and 81% isolates, respectively; IPM-CL, 13% and 87% isolates, respectively; and RIF-COL, 20% and 73% isolates, respectively. Significant proportion (19%) of XDR P. aeruginosa isolates produced MBLs, and majority (82%) of A. baumannii isolates produced either MBLs or OXA-23. CONCLUSIONS: Our results suggest that combinations of IPM-AMS, IPM-RIF, IPM-CL, and RIF-CL are more useful than individual drugs for treating 13-20% of XDR A. baumannii infections.
Acinetobacter baumannii/*drug effects/genetics/isolation & purification ; Aminoglycosides/pharmacology ; Anti-Infective Agents/*pharmacology ; Bacterial Proteins/genetics/metabolism ; Drug Resistance, Multiple, Bacterial/*drug effects ; Drug Synergism ; Fluoroquinolones/pharmacology ; Imipenem/pharmacology ; Microbial Sensitivity Tests ; Polymerase Chain Reaction ; Pseudomonas aeruginosa/*drug effects/genetics/isolation & purification ; beta-Lactamases/genetics/metabolism

BACKGROUND: Acinetobacter baumannii infections are difficult to treat owing to the emergence of various antibiotic resistant isolates. Because treatment options are limited for multidrug-resistant (MDR) A. baumannii infection, the discovery of new therapies, including combination therapy, is required. We evaluated the synergistic activity of colistin, doripenem, and tigecycline combinations against extensively drug-resistant (XDR) A. baumannii and MDR A. baumannii. METHODS: Time-kill assays were performed for 41 XDR and 28 MDR clinical isolates of A. baumannii by using colistin, doripenem, and tigecycline combinations. Concentrations representative of clinically achievable levels (colistin 2 microg/mL, doripenem 8 microg/mL) and achievable tissue levels (tigecycline 2 microg/mL) for each antibiotic were used in this study. RESULTS: The colistin-doripenem combination displayed the highest rate of synergy (53.6%) and bactericidal activity (75.4%) in 69 clinical isolates of A. baumannii. Among them, thedoripenem-tigecycline combination showed the lowest rate of synergy (14.5%) and bacteri-cidal activity (24.6%). The doripenem-tigecycline combination showed a higher antagonistic interaction (5.8%) compared with the colistin-tigecycline (1.4%) combination. No antagonism was observed for the colistin-doripenem combination. CONCLUSIONS: The colistin-doripenem combination is supported in vitro by the high rate of synergy and bactericidal activity and lack of antagonistic reaction in XDR and MDR A. baumannii. It seems to be necessary to perform synergy tests to determine the appropri-ate combination therapy considering the antagonistic reaction found in several isolates against the doripenem-tigecycline and colistin-tigecycline combinations. These findings should be further examined in clinical studies.
Acinetobacter Infections/drug therapy/microbiology ; Acinetobacter baumannii/*drug effects/genetics/isolation & purification ; Anti-Bacterial Agents/*pharmacology/therapeutic use ; Bacterial Proteins/genetics ; Carbapenems/*pharmacology/therapeutic use ; Colistin/*pharmacology/therapeutic use ; Drug Resistance, Multiple, Bacterial/*drug effects ; Drug Synergism ; Drug Therapy, Combination ; Humans ; Microbial Sensitivity Tests ; Minocycline/*analogs & derivatives/pharmacology/therapeutic use ; Multilocus Sequence Typing ; beta-Lactamases/genetics

BACKGROUND: We investigated the whole genome sequence (WGS) of a carbapenem-resistant Acinetobacter baumannii isolate belonging to the global clone 2 (GC2) and predicted resistance islands using a software tool. METHODS: A. baumannii strain YU-R612 was isolated from the sputum of a 61-yr-old man with sepsis. The WGS of the YU-R612 strain was obtained by using the PacBio RS II Sequencing System (Pacific Biosciences Inc., USA). Antimicrobial resistance genes and resistance islands were analyzed by using ResFinder and Genomic Island Prediction software (GIPSy), respectively. RESULTS: The YU-R612 genome consisted of a circular chromosome (ca. 4,075 kb) and two plasmids (ca. 74 kb and 5 kb). Its sequence type (ST) under the Oxford scheme was ST191, consistent with assignment to GC2. ResFinder analysis showed that YU-R612 possessed the following resistance genes: four β-lactamase genes bla(ADC-30), bla(OXA-66), bla(OXA-23), and bla(TEM-1); armA, aadA1, and aacA4 as aminoglycoside resistance-encoding genes; aac(6')Ib-cr for fluoroquinolone resistance; msr(E) for macrolide, lincosamide, and streptogramin B resistance; catB8 for phenicol resistance; and sul1 for sulfonamide resistance. By GIPSy analysis, six putative resistant islands (PRIs) were determined on the YU-R612 chromosome. Among them, PRI1 possessed two copies of Tn2009 carrying bla(OXA-23), and PRI5 carried two copies of a class I integron carrying sul1 and armA genes. CONCLUSIONS: By prediction of resistance islands in the carbapenem-resistant A. baumannii YU-R612 GC2 strain isolated in Korea, PRIs were detected on the chromosome that possessed Tn2009 and class I integrons. The prediction of resistance islands using software tools was useful for analysis of the WGS.
Acinetobacter Infections/*drug therapy/microbiology ; Acinetobacter baumannii/drug effects/*genetics/isolation & purification ; Anti-Bacterial Agents/pharmacology/*therapeutic use ; Bacterial Proteins/genetics ; Carbapenems/*therapeutic use ; DNA, Bacterial/chemistry/*genetics/metabolism ; Drug Resistance, Bacterial ; Genomic Islands/genetics ; Humans ; Microbial Sensitivity Tests ; Multilocus Sequence Typing ; Plasmids/genetics/metabolism ; Polymerase Chain Reaction ; Sequence Analysis, DNA

BACKGROUND/AIMS: Nosocomial infections caused by multidrug-resistant (MDR) Acinetobacter baumannii have become public-health problem. However, few studies have evaluated the control of endemic MDR A. baumannii in Intensive Care Units (ICUs). Therefore, we investigated the effectiveness of antimicrobial stewardship and comprehensive intensified infection control measures for controlling endemic MDR A. baumannii in ICUs at a tertiary care center. METHODS: Carbapenem use was strictly restricted through antimicrobial stewardship. Environmental cleaning and disinfection was performed at least 3 times per day in addition to basic infection control measures. Isolation using plastic curtains and contact precautions were applied to patients who were colonized or infected with MDR A. baumannii. The outcome was measured as the incidence density rate of hospital-onset MDR A. baumannii among patients in the ICUs. RESULTS: The incidence density rate of hospital-onset MDR A. baumannii decreased from 22.82 cases per 1,000 patient-days to 2.68 cases per 1,000 patient-days after the interventions were implemented (odds ratio, 0.12; 95% confidence interval, 0.03 to 0.4; p < 0.001). The mean monthly use of carbapenems also decreased from 134.99 +/- 82.26 defined daily doses per 1,000 patient-days to 94.85 +/- 50.98 defined daily doses per 1,000 patient-days (p = 0.016). CONCLUSIONS: Concomitant implementation of strict antimicrobial stewardship and comprehensive infection control measures effectively controlled endemic MDR A. baumannii in our ICUs within 1 year.
Acinetobacter Infections/epidemiology/microbiology/*prevention & control/transmission ; Acinetobacter baumannii/*drug effects/pathogenicity ; Anti-Bacterial Agents/adverse effects/*therapeutic use ; Carbapenems/adverse effects/*therapeutic use ; Chi-Square Distribution ; Cross Infection/epidemiology/microbiology/*prevention & control/transmission ; Disinfection ; *Drug Resistance, Multiple, Bacterial ; *Endemic Diseases ; Hand Disinfection ; Humans ; Incidence ; Infection Control/*methods ; Microbial Sensitivity Tests ; Odds Ratio ; Patient Isolation ; Program Evaluation ; Republic of Korea/epidemiology ; Risk Factors ; Tertiary Care Centers ; Time Factors ; Treatment Outcome

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 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