Microorganisms inhabiting soils contaminated with heavy metals produce melanin, a dark brown pigment, as a survival strategy. In this study, a melanin-producing bacterium, Acinetobacter sp. ME1, with heavy metal tolerance and plant growth-promoting traits, was isolated from abandoned mine soil. Strain ME1 exhibited growth at concentrations of Zn up to 250 mg/L, Cd and Pb up to 100 mg/L, and Cr up to 50 mg/L. It had the ability to produce the plant hormone indole-3-acetic acid and siderophores along with 1-aminocyclopropane-1-carboxylic acid deaminase and protease activities. Additionally, it showed antioxidant activity, including catalase and 2,2-diphenyl-1-picryhydrazyl (DPPH) scavenging activities. The optimal conditions for melanin production by ME1 were a pH of 7 and a temperature of 35 ℃. At 1000 mg/L, ME1-extracted melanin exhibited DPPH radical scavenging activity of (25.040±0.007)%, a sun protection factor of 15.200±0.260, and 19.6% antibacterial activity against the plant pathogen Xanthomonas campestris. Furthermore, its adsorption capacity was (0.235±0.073) mg/g melanin for Zn and (0.277±0.008) mg/g melanin for Ni. In plants of Brassica chinensis grown under conditions of hydroponic cultivation with single heavy metal contamination of Cd, Zn, Pb, or Cr, the removal efficiency of each heavy metal was improved by 0.1‒1.8 times after 3 d following inoculation with the strain ME1 compared to the plants grown under the same conditions without inoculation. In addition, ME1 inoculation improved the removal efficiency of each heavy metal by 0.1‒1.0 times under multiple heavy metal contamination conditions. These findings suggest that Acinetobacter sp. ME1 could be used to enhance phytoremediation efficiency in heavy metal-contaminated soils. Moreover, the melanin it produces also holds promise in cosmetics, household products, and medical applications due to its photoprotective, antioxidant, and antimicrobial properties.
Acinetobacter/metabolism* ; Biodegradation, Environmental ; Metals, Heavy/metabolism* ; Melanins/metabolism* ; Soil Microbiology ; Antioxidants/metabolism* ; Plant Development ; Soil Pollutants/metabolism* ; Indoleacetic Acids/metabolism*

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*

Introduction: Intensive care unit (ICU) patients are at the greatest risk of acquiring nosocomial infections, partly because of their serious underlying disease, but also by exposure to life-saving invasive procedures. Hospital-acquired infections increase patient morbidity, increase the length of hospital stay and hospital costs, and also increases mortality rate. The basic knowledge of organisms infecting ICU patients is very important to empirically select appropriate antibiotics, so that the most likely infecting organisms are addressed. Objective: The aim of the study was to find out the etiologic agents causing infection in medical intensive care unit patients. Results In our study of 289 patients, 180 (62.3%) showed a growth of organism during the stay in ICU. The most common site of infection was the respiratory tract in 138 patients (47.8%) with 60 patients (20.8%) showing Acinetobacter baumannii.
Cross Infection ; Intensive Care Units ; Acinetobacter baumannii ; Respiration, Artificial

OBJECTIVE: To investigate the incidence and infection regularity of ventilator-associated pneumonia (VAP) in patients undergoing tracheal intubation and to provide reference for the prevention and treatment of VAP infection in the future. METHODS: A retrospective study was conducted to collect the microbial data of airway secretion cultures from 72 patients with endotracheal intubation admitted to the emergency ward of Shanghai Fifth People's Hospital from May 2020 to February 2021, and the species of microorganisms and intubation time were statistically analyzed. RESULTS: Among 72 patients with endotracheal intubation, males were more than females (58.33% vs. 41.67%); Patients over 60 years old accounted for 90.28%; pneumonia was the main primary disease, accounting for 58.33%. Pathogenic tests showed that: (1) 72 patients were infected with Acinetobacter baumannii (AB), Klebsiella pneumoniae (KP), and Pseudomonas aeruginosa (PA) 48 hours after intubation, 51.39% (37/72), 27.78% (20/72), and 26.39% (19/72), respectively. The infection rate of AB was significantly higher than that of KP and PA. Within 48 hours of intubation, the infection rates of AB, KP, and PA were 20.83% (15/72), 13.89% (10/72), and 4.17% (3/72), respectively. Of the 42 patients with primary pneumonia, 61.90% (26/42) were infected with one or more of the three pathogenic bacteria AB, KP, and PA 48 hours after intubation, indicating a change in the etiology of the pathogenic bacteria, with the main pathogenic bacteria transitioning from other pathogenic bacteria to AB, KP, and PA. (2) AB, KP, and PA were prone to cause late onset VAP (i.e., intubation ≥ 5 days). Respectively, among VAP patients infected with AB, late onset VAP accounted for 59.46% (22/37). Among patients infected with KP, 75.00% (15/20) had late onset VAP. Among patients infected with PA, late onset VAP accounted for 94.74% (18/19), indicating a higher proportion of late onset VAP caused by PA and KP. (3) Infection was closely related to intubation time, and the pipeline can be replaced according to the peak period of infection. AB and KP infections peaked within 4 days after intubation, reaching 57.69% (30/52) and 50.00% (15/30), respectively. It is recommended to replace the tubes or undergo sensitive antimicrobial therapy around 3-4 days after starting the machine. The proportion of PA infection after 7 days of intubation was 72.73% (16/22), and it was considered to replace the pipeline after 7 days. (4) Most of the three pathogenic bacteria, AB, KP, and PA were carbapenem resistant pathogens with multiple drug resistance. Except for PA, the infection rate of carbapenem resistant bacteria (CRAB, CRKP) was significantly higher than that of non-carbapenem resistant bacteria (AB, KP), accounting for 86.54% (45/52) and 66.67% (20/30) of the corresponding infection cases, respectively, while CRPA only accounts for 18.18% (4/22). CONCLUSIONS The main differences in VAP infection caused by AB, KP, and PA pathogens are infection time, infection probability, and carbapenem resistance. Targeted prevention and treatment measures can be implemented for patients with intubation.
Female ; Male ; Humans ; Middle Aged ; Pneumonia, Ventilator-Associated ; Retrospective Studies ; China ; Intubation, Intratracheal ; Acinetobacter baumannii ; Klebsiella pneumoniae

Objective: To understand the risk factors and antibiotics-resistant patterns of invasive Acinetobacter baumannii infection in Children. Methods: This retrospective study was conducted in 6 tertiary hospitals from January 2016 to December 2018. The basic information, clinical data and the results of antimicrobial susceptibility testing were collected from the 98 pediatric inpatients with Acinetobacter baumannii isolated from blood or cerebrospinal fluid and analyzed. According to the susceptibility of the infected strains to carbapenems, they were divided into carbapenem-sensitive Acinetobacter baumannii (CSAB) group and carbapenem-resistant Acinetobacter baumannii (CRAB) group. According to the possible sources of infection, they were divided into nosocomial infection group and community infection group. Chi-square test or Fisher exact test were used to analyze categorical variables and rank sum test were used to analyze continuous variables. The risk factors of invasive CRAB infection in children were analyzed by Logistic regression. Result: There were 56 males and 42 females in 98 cases. The onset age of patients was 8 (2, 24) months. There were 62 cases (63%) from rural area. A total of 87 cases (89%) were confirmed with bloodstream infection, and 12 cases (12%) confirmed with meningitis (1 case was accompanied with bloodstream infection). In these patients, 66 cases (67%) received invasive medical procedures or surgery, 54 cases (55%) received carbapenems-containing therapy. Twenty-four cases were infected with CRAB, and 74 cases with CSAB. The onset age of cases in CRAB group was lower than that in CSAB group (4 (1, 9) vs. 10 (4, 24) months, Z=-2.16, P=0.031). The proportions of hospitalization in intensive care unit, carbapenem antibiotics using, pneumonia and adverse prognosis in CRAB group were higher than those in CSAB group (6 cases (25%) vs. 4 cases (5%), 18 cases (75%) vs. 36 cases (49%), 17 cases (71%) vs. 17 cases (23%), 6 cases (25%) vs. 4 cases (5%), χ²=5.61, 5.09, 18.32, 5.61, all P<0.05). Seventy-seven cases were nosocomial infection and 21 cases were hospital-acquired infection. The proportion of children hospitalized in high-risk wards for nosocomial infections, length of hospitalization, number of antimicrobial therapy received and duration of antimicrobial therapy were higher in the hospital associated infection group than those in the community acquired infection group (all P<0.05). Logistic regression analysis showed that children from rural area (OR=8.42, 95%CI 1.45-48.88), prior mechanical ventilation (OR=12.62, 95%CI 1.31-121.76), and prior antibiotic therapy (OR=4.90, 95%CI 1.35-17.72) were independent risk factors for CRAB infection. The resistance percentage of CSAB isolates to many classes of antibiotics was <6% except to gentamicin, which was as high as 20% (13/65). All CRAB isolates of resistant to ampicillin-sulbactam (20/20), cefepime (23/23), piperacillin (17/17), meropenem (23/23) and imipenem (24/24) were 100%. The resistance percentage to other antibiotics were up to 42%-96%. Conclusions: Most of invasive Acinetobacter baumannii infection in children in China are hospital-acquired. The outcome of invasive CRAB infection was poorer than that of CSAB infection. The drug resistance rate of CRAB strains isolated is high. Living in rural area, prior invasive mechanical ventilation and prior antibiotic therapy were independent risk factors for invasive CRAB infection. The prevention and control of nosocomial infection and appropriate use of antibiotics to reduce Acinetobacter baumannii infection.
Acinetobacter Infections/epidemiology* ; Acinetobacter baumannii ; Anti-Bacterial Agents/therapeutic use* ; Carbapenems/therapeutic use* ; Child ; Cross Infection/epidemiology* ; Drug Resistance, Multiple, Bacterial ; Female ; Humans ; Infant ; Male ; Microbial Sensitivity Tests ; Retrospective Studies ; Risk Factors ; Sepsis

Aims: Polymyxins are an important last-line treatment for infections caused by multidrug-resistant Gram-negative bacteria. Nonetheless, the emergence of polymyxin-resistance and the limiting of polymyxin monotherapy urgently demands its optimisation. Aquilaria malaccensis (Agarwood) has been widely used as traditional medicine. Many parts of the plant including leaves exhibit a considerable in vitro antibacterial activity against microbial pathogens. Exploiting A. malaccensis in combination with polymyxins provides a novel strategy in fighting antimicrobial resistance. The objective of this study was to evaluate the combination effects of A. malaccensis extract with polymyxins against Acinetobacter baumannii and Klebsiella pneumoniae. Methodology and results: In vitro time-kill studies and GC-MS analysis were performed to evaluate the bacterial killing of polymyxin B and extract combination and analyse chemical compounds of the extract, respectively. The combination of polymyxin B (1 mg/L) and A. malaccensis extract (32 mg/mL and 64 mg/mL) treatments exhibited enhanced bacterial killing compared to polymyxin B alone at 4 h and 24 h. Combination treatments also inhibited the bacterial growth of both A. baumannii and K. pneumoniae observed throughout the 24 h. More than sixty compounds including phytol, 9,12-octadecadienal, fatty acid, alkanes and terpenoids were putatively identified as the compounds that likely contributed to the antibacterial activity. Conclusion, significance and impact of study This study was the first to report the potential application of A. malaccensis extract in combination with polymyxin B in treatment against A. baumannii and K. pneumoniae and can be further investigated and optimized for the treatment of bacterial infectious diseases.
Thymelaeaceae ; Polymyxins ; Acinetobacter baumannii--immunology ; Klebsiella pneumoniae--immunology

Aims: Acinetobacter baumannii has been identified as one of the six most pathogenic bacteria that is the cause of most hospital bacterial infections according to Infectious Disease Society of America (IDSA). These nosocomial pathogens are notorious worldwide due to its ability in causing lethal infections among immunocompromised patients and its resistance to many strong antibiotics. This study aims to compare the expressed proteins of two A. baumannii strain, ATCC 19606 and a pathogenic clinically isolated strain known as AB-13. Methodology and results: AB-13 clinically strain was isolated from the lower respiratory tract of a patient with pneumonia. In this study, the proteomic profile of both ATCC 19606 and AB-13 are produced using 2-dimensional gel electrophoresis. The total protein contents were extracted, quantified and separated using 2-DE with a pH range of 4-7 to acquire the proteomic profile for comparison. The final analytical gel was analysed using Delta2D software and among the 324 protein spots successfully resolved, 10 spots exhibited signs of differential expression with 7 spots found to be downregulated and 3 spots upregulated (p< 0.01). These differences could signify the evolution AB-13 has undergone as it acquires traits ultimately aiding in its survivability, antimicrobial resistance and pathogenicity within varied environments especially during infections. Conclusion, significance and impact of study These findings support the presence of variation in AB-13 from a proteomic perspective, highlighting the pathogen’s evolution improving survivability and pathogenicity, warranting in-depth exploration towards understanding A. baumannii virulence and pathogenicity.
Acinetobacter baumannii--pathogenicity ; Two-Dimensional Difference Gel Electrophoresis ; Proteomics

OBJECTIVES: To determine the risk factors, clinical features, and outcomes of newborns in a tertiary care hospital who developed Acinetobacter baumannii infection.

METHODOLOGY: A retrospective case control study was performed, comparing each case of newborn infected with Acinetobacter baumannii to two uninfected controls.

RESULTS: Ninety charts were reviewed, comprising 30 cases and 60 controls. Risk factors (use of total parenteral nutrition, prior antibiotic use, presence of a central line, mechanical ventilation and intubation, blood transfusion, surgical procedure, intensive care unit admission and presence of a co-morbidity) were noted to be significantly associated with the development of A. baumannii infection (p value <0.001). A. baumannii infection manifests more commonly as fever, respiratory distress, leukocytosis, and thrombocytopenia.

CONCLUSIONS: Acinetobacter baumannii is associated with certain risk factors that increase the likelihood for its perpetuation and acquisition. The increasing number of multi-drug resistant strains of A. baumanni signifies the need to focus on certain issues as infection control and the conscientious use of antibiotics in newborns.

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

Background: Intraventricular antimicrobial therapy (IVT), defined as the direct installation of antimicrobial agents into the lateral ventricles has been utilized as the last therapeutic option for the treatment of multidrug-resistant ventriculitis. The aim of this case series is to report our institution’s experience with IVT in pediatric patients with ventriculitis. Material and Methods: Retrospective chart review was done. The demographic data, cerebrospinal fluid (CSF) culture isolates, treatment regimens, and clinical outcomes of these patients were collected and described. Results: Between 2016 to 2018, seven (7) pediatric patients diagnosed with ventriculitis caused by multidrug-resistant organisms underwent intraventricular antimicrobial therapy in combination with intravenous therapy. The median age was 1 year (range 1 month to 17 years old, mean: 4.4 years). Fifty-seven (57) percent of the patients were females. The isolated pathogens were Acinetobacter baumannii MDRO (n = 3), Klebsiella pneumoniae MDRO (n = 2), Methicillin-resistant Staphylococcus aureus (n = 1), and Methicillin-resistant Staphylococcus epidermidis (n = 2).One patient had mixed isolates on CSF culture (Acinetobacter baumannii and MRSE). The antimicrobial agents for IVT used were colistin (n = 4), vancomycin (n = 2), and gentamicin (n = 1). The mean time to initiation of intraventricular therapy from the diagnosis of ventriculitis was 19 days. The mean duration of IVT therapy was 15 days. The survival rate was 57%. Conclusion Ventriculitis caused by drug-resistant organisms is an emerging concern. Optimal therapy is not yet established and experience with IVT is limited. This series showed that there were no adverse effects related to IVT thus it may be considered an option for MDRO ventriculitis. Gram negative organisms are more common causes of ventriculitis in our institution.
Acinetobacter baumannii ; Methicillin-Resistant Staphylococcus aureus