Isolation of a lytic bacteriophage against extensively drug-resistant Acinetobacter baumannii infections and its dramatic effect in rat model of burn infection

Objectives

Acinetobacter Baumannii is an opportunistic nosocomial pathogen belonging to the Moraxellaceae family. The emergence of multidrug resistant strains of this pathogen caused many problems for hospitals and patients. The aim of the current study was to isolate, identify, and morphologically, physiologically, and in vivo analyze a new lytic bacteriophage targeting extensively drug‐resistant (XDR) A. baumannii.

Materials and Methods

Different wastewater samples were tested for isolation of lytic bacteriophage against 19 A. baumannii isolates obtained from patients hospitalized in a hospital in Arak, Iran, from January 2019 to March 2019. The phenotypic and genotypic characteristics of A. baumannii strains (resistance genes including: adeA, adeB, adeC, adeR, adeS, ISAba1, blaOXA‐23, blaOXA‐24) were analyzed. The isolated phage characteristics including adsorption time, pH and thermal stability, host range, one‐step growth rate, electron microscopy examination, and therapeutic efficacy of the phage were also investigated. Therapeutic efficacy of the phage was evaluated in a rat model with burn infection of XDR A. baumannii. The lesion image was taken on different days after burning and infection induction and was compared with phage untreated lesions.

Results

The results showed unique characteristics of the isolated phage (vB‐AbauM‐Arak1) including high specificity for Acinetobacter baumannii, stability at a relatively wide range of temperatures and pH values, short adsorption time, short latent period, and large burst size. In relation to the therapeutic efficacy of the phage, the lesion area decreased in phage‐treated groups over 14 days than in those untreated, significantly (p < 0.05).

Conclusion

Our findings demonstrated that isolated lytic phage was able to eliminate burn infections caused by XDR A. baumannii in a rat model. So, it may be recommended as alternative options toward to developing a treatment for extensively drug resistant Acinetobacter infections.

Pandrug-resistant Gram-negative bacteria: a systematic review of current epidemiology, prognosis and treatment options

BACKGROUND

The literature on the epidemiology, mortality and treatment of pandrug-resistant (PDR) Gram-negative bacteria (GNB) is scarce, scattered and controversial.

OBJECTIVES

To consolidate the relevant literature and identify treatment options for PDR GNB infections.

METHODS

A systematic search in MEDLINE, Scopus and clinical trial registries was conducted. Studies reporting PDR clinical isolates were eligible for review if susceptibility testing for all major antimicrobials had been performed. Characteristics and findings of retrieved studies were qualitatively synthesized.

RESULTS

Of 81 studies reviewed, 47 (58%) were published in the last 5 years. The reports reflected a worldwide dissemination of PDR GNB in 25 countries in 5 continents. Of 526 PDR isolates reported, Pseudomonas aeruginosa (n=175), Acinetobacter baumannii (n=172) and Klebsiella pneumoniae (n=125) were most common. PDR GNB were typically isolated in ICUs, but several studies demonstrated wider outbreak potential, including dissemination to long-term care facilities and international spread. All-cause mortality was high (range 20%-71%), but appeared to be substantially reduced in studies reporting treatment regimens active in vitro. No controlled trial has been performed to date, but several case reports and series noted successful use of various regimens, predominantly synergistic combinations, and in selected patients increased exposure regimens and newer antibiotics.

CONCLUSIONS

PDR GNB are increasingly being reported worldwide and are associated with high mortality. Several treatment regimens have been successfully used, of which synergistic combinations appear to be most promising and often the only available option. More pharmacokinetic/pharmacodynamic and outcome studies are needed to guide the use of synergistic combinations.

Cloning of ompA gene from Acinetobacter baumannii into the eukaryotic expression vector pBudCE4.1 as DNA vaccine

Antibiotic resistant features of Acinetobacter baumannii is partly due to the decreased outer membrane proteins (OMPs) permeability. The OmpA is one of the most conserved proteins among A. baumannii with a considerable antigenic potential to stimulate the multidimensional immune system responses. The present study was aimed to clone the ompA gene into the eukaryotic expression vector with potential as DNA vaccine. The ompA gene of A. baumannii was amplified using polymerase chain reaction (PCR). The target DNA was cloned and sub-cloned into the pTZ57R/T and pBudCE4.1 vectors, respectively. The recombinant vectors containing ompA were then validated using colony PCR, vector sequencing and double-digestion strategies. The pBudCE4.1-ompA recombinant plasmid was transfected into the human dermal fibroblast cells (HDF) and presence of ompA transcript and protein was evaluated using reverse transcribed-PCR (RT-PCR) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Our finding from colony PCR, sequencing and enzyme double digestion result confirmed that target gene has been successfully inserted into the pTZ57RT and pBudCE4.1. The presence of an expected band (1112 bp) in RT-PCR as wells as a ~ 38 kDa band during SDS-PAGE showed that the recombinant pBudCE4.1-ompA construct was efficiently transfected into the HDF cells and expressed. Altogether, our observation demonstrated that the recombinant pBudCE4.1-ompA construct was successfully produced although further experiments are needed.

Epidemiology of multidrug-resistant Acinetobacter baumannii strains in Iran: a systematic review and meta-analysis

Acinetobacter baumannii is an important opportunistic pathogen that causes major public health concern especially in hospitalized patients due to the acquisition of multidrug resistance (MDR). The aim of this study was to systematically review published data about the prevalence rate of MDR-A. baumannii (MDR-AB) from different parts of Iran and provide an overall relative frequency (RF) using meta-analysis. All available national and international databanks were searched to find published studies up to June 2016. Quality of studies was assessed by STROB and PRISMA forms. Because of the significant heterogeneity observed, random effects model was used to combine the results. STATA SE version 11.2 was used for statistical analysis. Out of the 9646 results, 37 suitable articles were extracted according to inclusion and exlusion criteria. The pooled prevalence of MDR-AB was estimated 72% annually. Relative frequency of MDR-AB in different studies varied from 22.8 to 100%. Since the prevalence of MDR-AB is higher than many other countries, measures should be taken to keep the emergence and transmission of these strains to a minimum.

Elevated prevalence of multidrug-resistant Acinetobacter baumannii with extensive genetic diversity in the largest burn centre of northeast Iran

OBJECTIVES

The emergence and spread of multidrug-resistant (MDR) Acinetobacter baumannii isolates is now frequently associated with nosocomial infections. The aim of this study was to evaluate the genetic relatedness and patterns of antimicrobial resistance amongst A. baumannii isolated from a burn centre at a teaching hospital in Iran.

METHODS

A total of 54 A. baumannii isolates were collected from burn wound infections of hospitalised patients. Antimicrobial susceptibility of the isolates was determined, and genotyping analysis was performed by repetitive extragenic palindromic PCR (rep-PCR). PCR assay was performed to investigate the distribution of β-lactamase, aminoglycoside-modifying enzyme and efflux pump genes.

RESULTS

Etest results revealed that the most active antimicrobial agent was colistin (100% susceptibility), followed by tigecycline (96.3%). The bla_OXA-51 and bla_ADC genes were detected in all of the isolates, but bla_OXA-58-like was not detected. The prevalence of bla_TEM, bla_IMP, bla_VIM, bla_OXA-23-like and bla_OXA-24-like genes was 64.8%, 70.4%, 70.4%, 66.7% and 68.5%, respectively. ISAba1 was detected upstream of bla_OXA-23-like and bla_ADC in 66.7% and 77.8% of isolates, respectively. This study showed a high level of distribution of adeB (72.2%), aphA6 (81.5%), aacC1 (85.2%), aadA1 (59.3%), aadB (31.5%), tetB (70.4%) and aphA1 (29.6%) in A. baumannii strains. Based on rep-PCR analysis, four clusters (I-IV) were defined.

CONCLUSIONS

The elevated prevalence of MDR A. baumannii strains in this burn centre suggests that local antibiotic prescription policies should be precisely revised. Moreover, strict infection control procedures to prevent further dissemination need to be prioritised immediately.

Distributions and Types of Multidrug-Resistant Acinetobacter baumannii in Different Departments of a General Hospital

Background:

Acinetobacter baumannii is the most prevalent strain in hospitals and different clinical departments.

Objectives:

The current study aimed to investigate the genetic characteristics and resistance mechanisms of A. baumannii isolated from clinical samples in Shaoxing people’s hospital affiliated to Zhejiang University, Shaoxing, China.

Patients and Methods:

Acinetobacter baumannii strains were isolated from blood, phlegm and skin of the patients hospitalized in different departments as respiratory medicine, plastic surgery and intensive care unit (ICU). Multilocus sequence typing (MLST) was used to characterize the isolates. Kirby-Bauer test was used to evaluate antibiotic resistance of the bacteria. The expression of resistance inducing genes was detected by reverse transcription polymerase chain reaction (RT-PCR). The results were analyzed and compared.

Results:

Two bacterial types, ST208, and ST218, were identified in all 140 samples. The ST208 mainly came from ICU and department of respiratory medicine, while ST218 from department of plastic surgery; 70.21% of ST208 and 84.78% of ST218 were carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenem-susceptible Acinetobacter baumannii (CSAB), respectively. Multidrug-resistance genes in CRAB isolated from the hospital mainly included, oxa-23, oxa-5, intl 1 and qaceΔ1-sul 1. Besides, the highest and lowest antibiotic resistance was observed in the strains isolated from blood samples and wounds, respectively.

Conclusions:

The distribution of AB varies in different clinical departments and samples. In the hospital under study, the main types of AB were ST208 and ST218. The genes which affect the ability of antibiotic-resistance were oxa-23, oxa-51, intl 1 and qaceΔ1-sul 1.

Phenotypic and Molecular Epidemiology of Acinetobacter calcoaceticus baumannii Complex Strains Spread at Nemazee Hospital of Shiraz, Iran

Background

Acinetobacter calcoaceticus baumannii (ACB) complex are Gram-negative opportunistic bacteria with low virulence properties. Their resistance to antibiotics has become a matter of concern in hospital infections.

Objectives

The present study aimed to determine the prevalence and antimicrobial susceptibility of ACB isolates collected from the Nemazee hospital of Shiraz. In addition, Pulsed Field Gel Electrophoresis (PFGE) was used to determine the genetic patterns of these strains.

Patients and Methods

In this cross-sectional study, 93 strains of ACB complex were isolated from patients of Nemazee hospital, Shiraz, Iran. The antibiotic susceptibility patterns of the isolates to the following 15 antibiotics were determined: gentamicin, ticarcillin, ceftazidime, co-trimoxazole, imipenem, piperacillin tazobactam, amikacin, aztreonam, sulbactam, meropenem, tobramycin, cefotaxime, ceftriaxone, colistin, polymyxin B. Pulsed Field Gel Electrophoresis was used to determine the clonal relationship of these strains.

Results

Most of the isolates were found to be resistant to cefotaxime, co-trimoxazole, ceftriaxone, aztreonam, ceftazidime and ticarcillin (90%), and the least resistance was observed to colistin and polymyxin B. Among the 93 tested samples, 35 antimicrobial susceptibility patterns and 47 PFGE patterns were obtained.

Conclusions

High resistance to antibiotics was observed among the strains of ACB complex and the least resistance was towards colistin and polymyxin B, indicating that these antibiotics could be effective for treatment, in case there is no other choice. Using PFGE, the similarity between some strains of Acinetobacter was determined, which indicated epidemics in different parts of the hospital; such epidemics can in turn lead to increased incidence of Acinetobacter infections.

Antibiotic Resistance of Acinetobacter baumannii in Iran: A Systemic Review of the Published Literature

OBJECTIVES

Acinetobacter baumannii is a bacterium responsible for health care-associated infections, and it frequently develops multiple drug resistance (MDR). The prevalence of antibiotic-resistant A. baumannii in Iran has increased, and this may cause significant clinical problems. Therefore, in order to elucidate the development of antibiotic resistance, we performed a systematic review of the literature published on antibiotic-resistant A. baumannii reported in Iran.

METHODS

Thirty-six publications that met the criteria for inclusion were reviewed from an initial 87 papers. Selected papers published between 2008 and September 2014, were categorized on the basis of the sample collecting year been between 2001 and 2013.

RESULTS

Analysis of data revealed that, in general, there was an increase in antimicrobial resistance. During the initial time point of these studies (2001-2007) there was a high rate of resistance to all antibiotics, with the exception of carbapenems, lipopeptides, and aminoglycosides that had a low resistance rate in comparison with the others. Also, the resistance rate was increased in one group of these three antimicrobial groups from 2010 to 2013. In particular, there was an increase in resistance to carbapenems (imipenem and meropenem) from 2010-2011 and 2012-2013, whereas no significant change in the resistance rate of the other two antimicrobial groups (lipopeptides and aminoglycosides) during the study time was observed, although we did observe certain trends in amikacin (aminoglycoside group antibiotic) between 2011-2012 and 2012-2013.

CONCLUSION

These findings indicate that antimicrobial resistance of A. baumannii in Iran has increased, which may very well affect the antimicrobial resistance of this organism worldwide. Based on these results, novel prevention and treatment strategies against A. baumannii infections are warranted. Furthermore, these data may assist in revising treatment guidelines and regional policies in care units to slow the emergence of antimicrobial resistance.

High Prevalence of Class 1 to 3 Integrons Among Multidrug-Resistant Diarrheagenic Escherichia coli in Southwest of Iran

OBJECTIVES

Horizontal transfer of integrons is one of the important factors that can contribute to the occurrence of multidrug-resistant (MDR) bacteria. This study aimed to determine the prevalence of integrons among MDR Escherichia coli strains isolated from stool specimens and investigate the associations between the existence of integrons and MDR properties in the southwest of Iran.

METHODS

There were 164 E. coli strains isolated from January 2012 to June 2012. Fecal specimens identified as E. coli by the conventional methods. Subsequently the antibiotic resistance was assessed using Clinical and Laboratory Standard Institute criteria. The presence of class 1-3 integrons and embedded gene cassettes was verified using specific primers by multiplex polymerase chain reaction assay.

RESULTS

Among a total of 164 studied samples, 69 (42.07%) isolates were multidrug resistant. Class 1 and class 2 integrons were present in 78.26% and 76.81% MDR isolates, respectively. For the first time in Iran, class 3 integron was observed in 26.09% MDR isolates. Significant correlations were identified between: class 1 integron and resistance to amikacin, gentamicin, chloramphenicol, ampicillin, tetracycline, nalidixic acid, and co-trimoxazole; class 2 integron and resistance to aminoglycosides, co-trimoxazole, cefalexin, ampicillin, and chloramphenicol; and class 3 integron and resistance to gentamicin, kanamycin, and streptomycin.

CONCLUSION

Our results indicate that integrons are common among MDR isolates and they can be used as a marker for the identification of MDR isolates. Therefore, due to the possibility of a widespread outbreak of MDR isolates, molecular surveillance and sequencing of the integrons in other parts of the country is recommended.

Novel cassette array in a class 1 integron in clinical isolates of Acinetobacter baumannii from central Iran

Antibiotic resistance in Acinetobacter baumannii is a major problem in the hospital and outbreaks caused by this organism have been reported frequently. The present study aimed at determining the antibiotic susceptibility patterns, the prevalence of different classes of integrons and the characterization of integron class 1 gene cassettes in Iranian A. baumannii isolates. A total of 63 non-duplicate A. baumannii isolates were collected from clinical and environmental specimens in the Vali-Asr hospital in the central province of Iran (March to September, 2011). The antimicrobial susceptibility for 15 antibiotics which are used conventionally was determined by disk diffusion. The presence of different integron classes was investigated by PCR and the size of gene cassettes in class 1 integrons was then determined by PCR as well. Moreover, integron cassette arrays of isolates were delineated by RFLP and sequencing amplicons with different lengths. Of 63 isolates 62 (98.4%) carried a class 1 integron. The prevalence of IntI2 was 15.9% and the length of the amplicons ranged from 500 bp to 3 kb. Sequencing of integrons of class 1 revealed the presence of many resistance genes (aadA, aacA, aacC, dfrA, bla(GES) and bla(IMP)). We identified a completely new gene cassette which contained aacA7-qacF-aadA5-bla(IMP), this cassette has not been reported previously in A. baumannii.