Acinetobacter Infections ; etiology ; Acinetobacter baumannii ; drug effects ; isolation & purification ; Child, Preschool ; Drug Resistance, Bacterial ; Female ; Humans ; Infant ; Intensive Care Units, Pediatric ; Male ; Risk Factors

Acinetobacter Infections ; microbiology ; Acinetobacter baumannii ; drug effects ; isolation & purification ; Anthracosis ; microbiology ; Anti-Bacterial Agents ; pharmacology ; Drug Resistance, Bacterial ; Fosfomycin ; pharmacology ; Humans ; Imipenem ; pharmacology ; Pneumonia, Bacterial ; microbiology

OBJECTIVETo investigate the distribution of burn pathogens and their antibiotic resistance in a burn unit, so as to provide reference for clinical practice.

METHODSThree hundred and forty-eight burn patients hospitalized in our department were enrolled in this study. The pathogens isolated from the wounds, blood, venous catheter, sputum, urine, purulent discharge of wounds in these patients, and their antibiotic resistance were surveyed by retrospective analysis from Jan, 2001 to Dec, 2006.

RESULTSTotal-ly 464 strains were isolated, among which Gram negative (G-) bacilli accounted for 52.6%, Gram positive microorganisms (G+) accounted for 40.5%, and fungi accounted for 6.9%. The main pathogens were Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter species and Escherichia coli, among which Staphylococcus aureus (MRSA) was predominant (93.5%). MRSA was 100% resistant to levofloxacin, penicillium, oxacillin, and it was also resistant to other antibiotics except Vancomycin. The resistance rate of Pseudomonas aeruginosa to Cefoperazone/Sulbactam, Imipenem and cefepime were 15.8%, 36.8%, 33.3%, respectively.

CONCLUSIONStaphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter species and Escherichia coli were predominant in the burn unit,among them Staphylococcus aureus and Acinetobacter were more resistant to antibiotics.

Acinetobacter baumannii ; drug effects ; isolation & purification ; Burn Units ; Burns ; microbiology ; Cross Infection ; microbiology ; Drug Resistance, Bacterial ; Escherichia coli ; drug effects ; isolation & purification ; Humans ; Pseudomonas aeruginosa ; drug effects ; isolation & purification ; Retrospective Studies ; Staphylococcus aureus ; drug effects ; isolation & purification

OBJECTIVETo observe the antimicrobial activity of topical agents commonly used for burns on Acinetobacter baumannii (AB) in both free and biofilm states, and their synergistic effect with ambroxol on AB within biofilm.

METHODSEleven AB strains were isolated from wound excretion, respiratory tract, and blood of patients hospitalized in our hospital from August 2005 to April 2007. (1) The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of mafenide acetate and chlorhexidine acetate to free AB (including drug-resistant, drug-sensitive, and standard strains) were determined by dilution method. (2) AB was cultured with LB or TSB medium for 12, 24, and 48 h to form biofilm, and it was treated with above-mentioned two topical agents in MBC (mafenide group and chlorhexidine group) for 30 min. Biofilm not treated by topical agent was used as control group. The biofilm thickness was determined with confocal laser scanning microscope. The proportion of living bacteria in biofilm was calculated. AB biofilm in each topical agent group was mixed and inoculated into LB culture dish to observe the growth of bacteria. (3) AB was cultured with LB medium for 48 h to form biofilm, which was respectively treated by above-mentioned two topical agents in MBC (mafenide group and chlorhexidine group) and combination of each topical agent with 3.75 mg/mL ambroxol solution (ambroxol + mafenide group and ambroxol + chlorhexidine group) for 30 min. Biofilm not treated by topical agents was used as control group. Growth of bacteria in biofilm was detected with MTT method (denoted as absorbance value). Data were processed with one-way analysis of variance and LSD-t test.

RESULTS(1) MIC of mafenide acetate and chlorhexidine acetate for free AB was respectively 25.00 mg/mL and 0.03 mg/mL. MBC of both agents for free AB was the same as their MIC. (2) Among three groups, the thickness of biofilm of sensitive AB was thicker than that of drug-resistant bacteria at most of the time points. Compared with those in control group, biofilm thickness and proportion of living bacteria in biofilm were slightly decreased in mafenide and chlorhexidine groups. The growth of bacteria was abundant in each group. (3) Absorbance value of drug-resistant bacteria in control, mafenide, and chlorhexidine groups was respectively 0.776 ± 0.071, 0.625 ± 0.063, and 0.420 ± 0.068. Absorbance value of drug-resistant bacteria in ambroxol + mafenide group (0.174 ± 0.089) was significantly lower than that of control group (t = 11.823, P = 0.000) and mafenide group (t = 9.248, P < 0.01). Absorbance value of ambroxol + chlorhexidine group (0.178 ± 0.044) was significantly lower than that of control group (t = 16.009, P = 0.000) and chlorhexidine group (t = 6.681, P < 0.01).

CONCLUSIONSDrug-resistant AB forms biofilm readily, which prevents topical agents from killing the bacteria inside. Combined use of ambroxol with topical agents gives synergistic effect on killing AB in biofilm in the wound.

Acinetobacter baumannii ; drug effects ; isolation & purification ; Anti-Bacterial Agents ; pharmacology ; Biofilms ; drug effects ; Burns ; microbiology ; Chlorhexidine ; pharmacology ; Drug Resistance, Bacterial ; Humans ; Mafenide ; pharmacology ; Microbial Sensitivity Tests

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
Acinetobacter baumannii/*drug effects/isolation & purification ; Anti-Bacterial Agents/*pharmacology ; Drug Resistance, Bacterial ; Drug Synergism ; Humans ; Imipenem/*pharmacology ; Microbial Sensitivity Tests ; Time Factors

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

OBJECTIVETo analyze the distribution and drug resistance of bacteria in different wound infections and provide evidence for wound infection control in subtropical regions.

METHODSThis study involved 265 patients from 4 different departments of our hospital who experienced wound infections between July, 2007 and July, 2008. The bacterial strain distribution in the wounds and drug resistance of the bacteria were analyzed.

RESULTSAcinetobacter baumanii (39% of the total strain identified) was the most frequent bacterial strain causing infection of the burn wounds, followed by Proteus mirabilis (20%) and Pseudomonas aeruginosa (20%). E. coli infection was prevalent in the departments of general surgery (37%) and urinary surgery (64%), and Pseudomonas aeruginosa and Pseudomonas pneumonia infections were detected at the rate of 30% and 43% in the urinary surgery department, respectively. Different bacterial strains were found at similar rates around 10% in the wounds of patients undergoing traumatic surgery.

CONCLUSIONDespite that the commonly seen pathogenic bacteria in burn patients including Staphylococcus aureus have been effectively controlled by early application of antibiotics, the opportunistic pathogens such as Acinetobacter baumanii and Proteus mirabilis often survive these antibiotics, and some strains evolve to be drug-resistant and even multi-drug-resistant. E. coli infection is prevalent in general surgery and urinary surgery departments, where Staphylococcus aureus and Pseudomonas aeruginosa infections can also be found frequently. All kinds of bacteria infection are present in trauma surgery department, each found at the rate around 10%.

Acinetobacter baumannii ; drug effects ; isolation & purification ; Adolescent ; Adult ; Burns ; complications ; Child ; Child, Preschool ; Drug Resistance, Bacterial ; Escherichia coli ; drug effects ; isolation & purification ; Female ; Humans ; Male ; Middle Aged ; Pseudomonas aeruginosa ; drug effects ; isolation & purification ; Wound Infection ; etiology ; microbiology ; Young Adult

Acinetobacter baumannii ; drug effects ; isolation & purification ; Drug Resistance, Multiple, Bacterial ; Female ; Humans ; Infant, Extremely Low Birth Weight ; Infant, Newborn ; Pneumonia, Ventilator-Associated ; etiology

OBJECTIVETo investigate the role of AdeABC efflux pump in carbapenems resistance of Acinetobacter baumannii in light of the phenotype and genetype of the efflux pump.

METHODSThe phenotype of the efflux pump was detected in 138 clinical isolates of A.baumannii using the efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP). The mRNA expression of pump-encoding gene adeB in the strains was detected using quantitative real-time RT-PCR.

RESULTSOf the 138 strains, 28 showed positivities for AdeABC efflux pump identified by Mueller-Hinton Broth with CCCP. Of the 39 strains resistant to meropenem, 15 (38.4%) showed positive results in CCCP assay, a rate significantly higher than that among the 99 sensitive strains (13.1%, 13/99) (X(2)=12.477(b), P=0.01). The mRNA expression of efflux pump-encoding gene adeB was detected by real-time RT-PCR at a level of 0.899∓∓1.172 in meropenem-sensitive strains, significantly lower than the level of 21.101∓∓21.443 in meropenem-resistant strains (t=4.403, P=0.000).

CONCLUSIONSEfflux plays a role in carbapenems resistance in the clinical isolates of A. baumannii. The AdeABC efflux pump may be an important factor in reducing carbapenems sensitivity in A. baumannii.

Acinetobacter baumannii ; drug effects ; isolation & purification ; Bacterial Proteins ; genetics ; metabolism ; Carbapenems ; pharmacology ; Humans ; Membrane Transport Proteins ; genetics ; metabolism ; beta-Lactam Resistance ; genetics

OBJECTIVETo investigate the molecular mechanism of carbapenem resistance in the clinical isolates of Acinetobacter baumannii from Xi'an and their profile of carbapenemase production.

METHODSA total of 146 Acinetobacter baumannii strains were isolated from 6 general hospitals in Xi'an. Antimicrobial susceptibility test was performed for all the strains, followed by detection of imipenem resistance using E-test for metallo-beta-lactamase (MBL) and NaCl inhibition test for OXA type carbapenemase. Bla(OXA-23)and bla(OXA-58) were amplified by PCR, and the positive products were sequenced.

RESULTSFrom the collected strains, 15 non-repetitive imipenem-resistant Acinetobacter baumannii strains were identified, among which 14 yielded negative results in E-test for MBL production. All the resistant strains showed increased sensitivity to imipenem after NaCl inhibition, suggesting the presence of carbapenemase production. Eleven of the strains harbored OXA -23 type gene and 1 harbored OXA -58 type gene. The concordance rate of the results by NaCl inhibition test and PCR was 85.7%.

CONCLUSIONSProduction of OXA-type carbapenemase is the most important reason for carbapenem resistance in Acinetobacter baumannii in Xi'an. The OXA-58 type gene is a novel carbapenemase genotype in China. NaCl inhibition test is a convenient and cost-effective method for detecting carbapenemase in Acinetobacter baumannii.

Acinetobacter baumannii ; drug effects ; genetics ; isolation & purification ; Anti-Bacterial Agents ; pharmacology ; Bacterial Proteins ; genetics ; China ; Humans ; Imipenem ; pharmacology ; beta-Lactam Resistance ; beta-Lactamases ; genetics