Origanum vulgare essential oil: antibacterial activities and synergistic effect with polymyxin B against multidrug-resistant Acinetobacter baumannii.

Antimicrobial resistance is increasing around the world and the search for effective treatment options, such as new antibiotics and combination therapy is urgently needed. The present study evaluates oregano essential oil (OEO) antibacterial activities against reference and multidrug-resistant clinical isolates of Acinetobacter baumannii (Ab-MDR). Additionally, the combination of the OEO and polymyxin B was evaluated against Ab-MDR. Ten clinical isolates were characterized at the species level through multiplex polymerase chain reaction (PCR) for the gyrB and blaOXA-51-like genes. The isolates were resistant to at least four different classes of antimicrobial agents, namely, aminoglycosides, cephems, carbapenems, and fluoroquinolones. All isolates were metallo-ß-lactamase (MßL) and carbapenemase producers. The major component of OEO was found to be carvacrol (71.0%) followed by ß-caryophyllene (4.0%), γ-terpinene (4.5%), p-cymene (3,5%), and thymol (3.0%). OEO showed antibacterial effect against all Ab-MDR tested, with minimum inhibitory concentrations (MIC) ranging from 1.75 to 3.50 mg mL-1. Flow cytometry demonstrated that the OEO causes destabilization and rupture of the bacterial cell membrane resulting in apoptosis of A. baumannii cells (p < 0.05). Synergic interaction between OEO and polymyxin B (FICI: 0.18 to 0.37) was observed, using a checkerboard assay. When combined, OEO presented until 16-fold reduction of the polymyxin B MIC. The results presented here indicate that the OEO used alone or in combination with polymyxin B in the treatment of Ab-MDR infections is promising. To the best of our knowledge, this is the first report of OEO and polymyxin B association against Ab-MDR clinical isolates.

Antibiofilm Activity of Acidic Phospholipase Isoform Isolated from Bothrops erythromelas Snake Venom.

INTRODUCTION: Bacterial resistance is a worldwide public health problem, requiring new therapeutic options. An alternative approach to this problem is the use of animal toxins isolated from snake venom, such as phospholipases A2 (PLA2), which have important antimicrobial activities. Bothropserythromelas is one of the snake species in the northeast of Brazil that attracts great medical-scientific interest. Here, we aimed to purify and characterize a PLA2 from B. erythromelas, searching for heterologous activities against bacterial biofilms. METHODS: Venom extraction and quantification were followed by reverse-phase high-performance liquid chromatography (RP-HPLC) in C18 column, matrix-assisted ionization time-of-flight (MALDI-ToF) mass spectrometry, and sequencing by Edman degradation. All experiments were monitored by specific activity using a 4-nitro-3-(octanoyloxy) benzoic acid (4N3OBA) substrate. In addition, hemolytic tests and antibacterial tests including action against Escherichiacoli, Staphylococcusaureus, and Acinetobacterbaumannii were carried out. Moreover, tests of antibiofilm action against A. baumannii were also performed. RESULTS: PLA2, after one purification step, presented 31 N-terminal amino acid residues and a molecular weight of 13.6564 Da, with enzymatic activity confirmed in 0.06 µM concentration. Antibacterial activity against S. aureus (IC50 = 30.2 µM) and antibiofilm activity against A. baumannii (IC50 = 1.1 µM) were observed. CONCLUSIONS: This is the first time that PLA2 purified from B. erythromelas venom has appeared as an alternative candidate in studies of new antibacterial medicines.

Antimicrobial action of 1,10-phenanthroline-based compounds on carbapenemase-producing Acinetobacter baumannii clinical strains: efficacy against planktonic- and biofilm-growing cells.

Therapeutic options are limited for patients infected with Acinetobacter baumannii due to its multidrug-resistance profile. So, the search for new antimicrobials against this gram-negative bacterial pathogen has become a worldwide priority. The present study aimed to evaluate the effects of 1,10-phenanthroline (phen), 1,10-phenanthroline-5,6-dione (phendione), [Ag(phendione)2]ClO4 (Ag-phendione) and [Cu(phendione)3](ClO4)2·4H2O (Cu-phendione) on 26 carbapenemase-producing A. baumannii strains. The susceptibility to carbapenems was performed by detecting the metallo-beta-lactamase (MBL) genes by PCR and by determining the MIC. Also, disk diffusion method was applied to evaluate the susceptibility to other antimicrobial classes. The test compounds were evaluated on both planktonic- and biofilm-growing bacterial cells. The results revealed that all A. baumannii strains had the intrinsic blaoxa-51 gene, and at least one of the blaoxa-23 or blaoxa-24 genes. The geometric mean MIC and minimum bactericidal concentration (MBC) values, respectively, were as follows: Cu-phendione (1.56 and 2.30 µM), Ag-phendione (2.48 and 3.63 µM), phendione (9.44 and 9.70 µM), and phen (70.46 and 184.28 µM). The test compounds (at 0.5 × MIC) affected the biofilm formation and disrupted the mature biofilm, in a typically dose-dependent manner, reducing biomass and viability parameters. Collectively, silver and copper-phendione derivatives presented potent antimicrobial action against planktonic- and biofilm-forming cells of carbapenemase-producing A. baumannii.

In Vitro and In Vivo Assessment of the Efficacy of Bromoageliferin, an Alkaloid Isolated from the Sponge Agelas dilatata, against Pseudomonas aeruginosa.

The pyrrole-imidazoles, a group of alkaloids commonly found in marine sponges belonging to the genus Agelas, display a wide range of biological activities. Herein, we report the first chemical study of the secondary metabolites of the sponge A. dilatata from the coastal area of the Yucatan Peninsula (Mexico). In this study, we isolated eight known alkaloids from an organic extract of the sponge. We used NMR and MS analysis and comparison with existing databases to characterize the alkaloids: ageliferin (1), bromoageliferin (2), dibromoageliferin (3), sceptrin (4), nakamuric acid (5), 4-bromo-1H-pyrrole-2-carboxylic acid (6), 4,5-dibromopyrrole-2-carboxylic acid (7) and 3,7-dimethylisoguanine (8). We also evaluated, for the first time, the activity of these alkaloids against the most problematic multidrug-resistant (MDR) pathogens, i.e., the Gram-negative bacteria Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii. Bromoageliferin (2) displayed significant activity against P. aeruginosa. Comparison of the antibacterial activity of ageliferins 1-3 (of similar structure) against P. aeruginosa revealed some relationship between structure and activity. Furthermore, in in vitro assays, 2 inhibited growth and biofilm production in clinical strains of P. aeruginosa. Moreover, 2 increased the survival time in an in vivo Galleria mellonella model of infection. The findings confirm bromoageliferin (2) as a potential lead for designing new antibacterial drugs.

Characterization of the Different Stages of Biofilm Formation and Antibiotic Susceptibility in a Clinical Acinetobacter baumannii Strain.

Acinetobacter baumannii is a relevant opportunistic pathogen, and one of the main microorganisms responsible for outbreaks in nosocomial infections worldwide. Its pathogenicity is mainly due to its resistance to multiple antibiotics and to its ability to form biofilms on abiotic surfaces. The objective of this study was to characterize the biofilm formation cycle of A. baumannii isolated from a patient in a hospital and compare its antibiotic resistance with the planktonic cells. To study biofilm formation, the classical microtiter assay was used, with crystal violet staining and optical density reading to classify the type of biofilm. Also, the effect of gentamicin and colistin on bacterial biofilm was studied with an extra step of antibiotic addition. For the characterization of the different biofilm formation stages, the strain was grown on a coverslip, and the stain was made with a mixture of fluorophores markers to visualize the biofilm with a confocal laser microscope. It was possible to differentiate the A. baumannii biofilm formation stages. Through these observations, it was possible to estimate the time elapsed between each stage. As the strain was susceptible to colistin and gentamicin, both antibiotics were evaluated after the biofilm was formed. Neither antibiotics showed an effect on the eradication of A. baumannii biofilm.

Origanum vulgare L. essential oil inhibits the growth of carbapenem-resistant gram-negative bacteria.

INTRODUCTION: Plant products are sources for drug development against multidrug resistant bacteria. METHODS: The antimicrobial activity of Origanum vulgare L. essential oil (OVeo) against carbapenem-resistant strains was assessed by disk-diffusion, microdilution (REMA-Resazurin Microtiter Assay), and time kill assays. RESULTS: Carbapenemase production was confirmed for all strains. OVeo exhibited a minimum inhibitory concentration of 0.059% v/v for Klebsiella pneumoniae and Serratia marcescens, and of 0.015 % v/v for Acinetobacter baumannii. A decrease in cell count was observed after a 4 h treatment. CONCLUSIONS: OVeo antimicrobial effect was rapid and consistent, making it a candidate for developing alternative therapeutic options against carbapenem-resistant strains.

Biofilm contamination of high-touched surfaces in intensive care units: epidemiology and potential impacts.

The aim of this study was to determine the epidemiology (location, microbial load, microbiome, presence/absence of biofilm and pathogens, including ESKAPE-Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter species, and antimicrobial susceptibility profiles) of the bacterial contamination on intensive care units (ICUs) surfaces. Fifty-seven high-touched surfaces were collected from adult, paediatric and neonatal ICUs from two large public Brazilian hospitals from central and north regions. Samples (c. 4 cm2 ) were subjected to culture (qualitative), qPCR targeting 16s rRNA gene (microbial load-bacteria per cm2 ), 16s rRNA amplicon sequencing (microbiome analysis) and scanning electron (SEM) or confocal laser scanning microscopy (CLSM) (biofilm presence). Multidrug resistant organisms (MROs) were detected using specific chromogenic agar. The average bacterial load was 1·32 × 104 bacteria per cm2 , container for newborn feeding bottles, stretcher mattress, humidicrib mattress filling and computer keyboards presented the higher bioburden. However, only 45·6% (26/57) were culture-positive, including 4/26 with MROs. ESKAPE organisms were detected in 51·8% of the samples subjected to next-generation sequencing. Viability staining and CLSM demonstrated live bacteria on 76·7% of culture-negative samples. Biofilm was present on all surfaces subjected to microscopy (n = 56), demonstrating that current cleaning practices are suboptimal and reinforcing that MROs are incorporated into hospital surfaces biofilm. SIGNIFICANCE AND IMPACT OF THE STUDY: Contamination of healthcare facilities surfaces has been shown to play a major role in transmission of pathogens. The findings of this study show that dry surface biofilms are widespread and can incorporate pathogens and multidrug-resistant organisms (MROs). Biofilms on highly touched surfaces pose a risk to patients, as dry surface biofilms persist for long period and micro-organisms within biofilm have been shown to be transmitted. This study also provides a better understanding of microbial populations in hospital environments, reinforcing that pathogens and MROs are found incorporated into biofilm, which impacts the difficulty in cleaning/disinfection.

Origanum vulgare L. essential oil inhibits the growth of carbapenem-resistant gram-negative bacteria

Abstract INTRODUCTION: Plant products are sources for drug development against multidrug resistant bacteria. METHODS The antimicrobial activity of Origanum vulgare L. essential oil (OVeo) against carbapenem-resistant strains was assessed by disk-diffusion, microdilution (REMA-Resazurin Microtiter Assay), and time kill assays. RESULTS Carbapenemase production was confirmed for all strains. OVeo exhibited a minimum inhibitory concentration of 0.059% v/v for Klebsiella pneumoniae and Serratia marcescens, and of 0.015 % v/v for Acinetobacter baumannii. A decrease in cell count was observed after a 4 h treatment. CONCLUSIONS OVeo antimicrobial effect was rapid and consistent, making it a candidate for developing alternative therapeutic options against carbapenem-resistant strains.

In vitro activity of tigecycline and comparators (2014-2016) among key WHO 'priority pathogens' and longitudinal assessment (2004-2016) of antimicrobial resistance: a report from the T.E.S.T. study.

We report contemporary (2014-2016) Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) global data on activity of tigecycline and comparators against WHO 'priority pathogens', and global trends (2004-2016) in antimicrobial resistance. MICs were determined using CLSI broth microdilution methodology. Antimicrobial resistance was determined using CLSI breakpoints (FDA breakpoints for tigecycline). Data are reported for Africa, Asia, Europe, North America and South America. From 2014-2016, Africa, Asia and South America reported highest resistance rates among Acinetobacter baumannii; North America lowest (all antimicrobials tested). The tigecycline MIC90 against A. baumannii was 2 mg/L in all regions except South America (1 mg/L). Among Enterobacteriaceae, meropenem resistance was low and tigecycline resistance was ≤1.3% in all regions (Escherichia coli, 0.0-0.3%; Klebsiella pneumoniae 0.0-1.3%; Enterobacter spp. 0.5-1.1%; Serratia marcescens 0.0-1.3%). Ceftriaxone resistance among E. coli ranged from 14.5% (North America) to 54.7% (Asia), and among K. pneumoniae from 9.1% (North America) to 54.0% (South America). North America reported highest rates of vancomycin-resistant Enterococcus faecium (64.6%); Europe lowest (17.7%). The tigecycline MIC90 against methicillin-resistant Staphylococcus aureus (MRSA) ranged from 0.12 mg/L (Africa and North America) to 0.5 mg/L (Asia). From 2004-2016, carbapenem resistance increased among A. baumannii (all regions), reaching 92.3% in Africa and 85.7% in South America (2016). Rates of ceftriaxone-resistant E. coli increased in all regions except Asia. Ceftriaxone resistance in K. pneumoniae increased in Europe. Rates of vancomycin-resistant E. faecium and MRSA were highest in North America and South America (and Asia for MRSA); lowest in Europe.

Distinct Genetic Diversity of Carbapenem-Resistant Acinetobacter baumannii from Colombian Hospitals.

The global success of multidrug-resistant Acinetobacter baumannii has been associated with the dissemination of a high-risk clone designated clonal complex (CC) 92B (Bartual scheme)/CC2P (Pasteur scheme), which is the most frequent genetic lineage in European, Asian, and North American carbapenem-resistant Acinetobacter isolates. In these isolates, carbapenem resistance is mainly mediated by ß-lactamases encoded by blaOXA-23-like, blaOXA-24-like, blaOXA-51-like, and/or blaOXA-58-like genes. In this study, we characterized the population genetics of 121 carbapenem-resistant A. baumannii complex isolates recovered from 14 hospitals in seven cities in Colombia (2008-2010). Multiplex PCR was used to detect blaOXA-23-like, blaOXA-24-like, blaOXA-51-like, and blaOXA-58-like genes. Molecular typing was performed using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). PCR showed that 118 (97.5%) of the isolates were positive for both blaOXA-23-like and blaOXA-51-like genes, and three other isolates were only positive for blaOXA-51-like. PFGE identified 18 different pulsotypes, while MLST identified 11 different sequence types (STs), seven of which had not been previously described in Acinetobacter. None of the STs found in this study was associated with CC92B/CC2P. The most widespread STs in our isolates belonged to ST636 and their single-locus variants ST121/ST124/ST634 (CC636B) followed by STs belonging to CC110B. Our observations suggest a wide distribution of diverse A. baumannii complex clones containing blaOXA-23-like in Colombian hospitals (especially CC636B and CC110B) that differ from the high-risk clones commonly found in other regions of the world, indicating a distinct molecular epidemiology of carbapenem-resistant Acinetobacter spp. in Colombia.

Characterization of dioxygenases and biosurfactants produced by crude oil degrading soil bacteria

ABSTRACT Role of microbes in bioremediation of oil spills has become inevitable owing to their eco friendly nature. This study focused on the isolation and characterization of bacterial strains with superior oil degrading potential from crude-oil contaminated soil. Three such bacterial strains were selected and subsequently identified by 16S rRNA gene sequence analysis as Corynebacterium aurimucosum, Acinetobacter baumannii and Microbacterium hydrocarbonoxydans respectively. The specific activity of catechol 1,2 dioxygenase (C12O) and catechol 2,3 dioxygenase (C23O) was determined in these three strains wherein the activity of C12O was more than that of C23O. Among the three strains, Microbacterium hydrocarbonoxydans exhibited superior crude oil degrading ability as evidenced by its superior growth rate in crude oil enriched medium and enhanced activity of dioxygenases. Also degradation of total petroleum hydrocarbon (TPH) in crude oil was higher with Microbacterium hydrocarbonoxydans. The three strains also produced biosurfactants of glycolipid nature as indicated d by biochemical, FTIR and GCMS analysis. These findings emphasize that such bacterial strains with superior oil degrading capacity may find their potential application in bioremediation of oil spills and conservation of marine and soil ecosystem.

Characterization of dioxygenases and biosurfactants produced by crude oil degrading soil bacteria.

Role of microbes in bioremediation of oil spills has become inevitable owing to their eco friendly nature. This study focused on the isolation and characterization of bacterial strains with superior oil degrading potential from crude-oil contaminated soil. Three such bacterial strains were selected and subsequently identified by 16S rRNA gene sequence analysis as Corynebacterium aurimucosum, Acinetobacter baumannii and Microbacterium hydrocarbonoxydans respectively. The specific activity of catechol 1,2 dioxygenase (C12O) and catechol 2,3 dioxygenase (C23O) was determined in these three strains wherein the activity of C12O was more than that of C23O. Among the three strains, Microbacterium hydrocarbonoxydans exhibited superior crude oil degrading ability as evidenced by its superior growth rate in crude oil enriched medium and enhanced activity of dioxygenases. Also degradation of total petroleum hydrocarbon (TPH) in crude oil was higher with Microbacterium hydrocarbonoxydans. The three strains also produced biosurfactants of glycolipid nature as indicated d by biochemical, FTIR and GCMS analysis. These findings emphasize that such bacterial strains with superior oil degrading capacity may find their potential application in bioremediation of oil spills and conservation of marine and soil ecosystem.

Repurposing the anticancer drug mitomycin C for the treatment of persistent Acinetobacter baumannii infections.

Acinetobacter baumannii is an emergent opportunistic bacterial pathogen responsible for recalcitrant infections owing to its high intrinsic tolerance to most antibiotics; therefore, suitable strategies to treat these infections are needed. One plausible approach is the repurposing of drugs that are already in use. Among them, anticancer drugs may be especially useful due their cytotoxic activities and ample similarities between bacterial infections and growing tumours. In this work, the effectiveness of four anticancer drugs on the growth of A. baumannii ATTC BAA-747 was evaluated, including the antimetabolite 5-fluorouracil and three DNA crosslinkers, namely cisplatin, mitomycin C (MMC) and merphalan. MMC was the most effective drug, having a minimum inhibitory concentration for 50% of growth in Luria-Bertani medium at ca. 7 µg/mL and completely inhibiting growth at 25 µg/mL. Hence, MMC was tested against a panel of 21 clinical isolates, including 18 multidrug-resistant (MDR) isolates, 3 of which were sensitive only to colistin. The minimum inhibitory concentrations and minimum bactericidal concentrations of MMC in all tested strains were found to be similar to those of A. baumannii ATCC BAA-747, and MMC also effectively killed stationary-phase, persister and biofilm cells. Moreover, MMC was able to increase survival of the insect larvae Galleria mellonella against an otherwise lethal A. baumannii infection from 0% to ≥53% for the antibiotic-sensitive A. baumannii ATCC BAA-747 strain and the MDR strains A560 and A578. Therefore, MMC is highly effective at killing the emergent opportunistic pathogen A. baumannii.

Rapid Blue-Carba test: reduction in the detection time of carbapenemases performed from a 4-hour bacterial lawn.

The increase in carbapenem-resistant gram-negative bacteria is a matter of concern due to the limited therapeutic options available. In severe infections caused by these isolates, the rapid detection of the mechanisms of resistance is vital. We described a slightly modified version of the Blue-Carba test, rapid Blue-Carba test, which allows the detection of carbapenemases at 4 h of incubation from a haze of bacterial growth obtained from a positive blood culture. It was able to detect carbapenemase-producing isolates (Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii) with a sensitivity and specificity of 98.1 and 100%, respectively. It is a rapid, easy-to-perform and an inexpensive technique that can be applied to routine laboratories, together with the simultaneous identification by mass spectrometry which would help to screen non-enzymatic carbapenem resistance; this method allows the detection of clinically relevant multidrug-resistant bacteria and the early implementation of accurate therapeutic interventions.

Selective amino acid substitution reduces cytotoxicity of the antimicrobial peptide mastoparan.

The emergence of antibiotic-resistant clinical isolates and the decreased rate of development of new antibiotics are a constant threat to human health. In this context, the therapeutic value of mastoparan (MP), a toxin from wasp venom, has been extensively studied. However, since MP shows significant cytotoxic activities, further optimization is needed. Here we evaluated the antimicrobial and cytolytic activities of an MP analog created by Ala-substitution in positions 5 and 8, named [I5, R8] mastoparan ([I5, R8] MP). We found that [I5, R8] MP displayed a broad-spectrum antimicrobial activity against bacteria and fungi (MIC in the range 3-25µM), without being hemolytic or cytotoxic toward HEK-293 cells. In addition, [I5, R8] MP-amide was highly potent (MIC=3µM) against antibiotic-resistant bacteria. The interaction with microbial membranes was investigated revealing that [I5, R8] MP is able to form an active amphipathic α-helix conformation and to disturb membranes causing lysis and cell death. Based on our findings, we hypothesize that [I5, R8] MP follows a mechanism of action similar to that proposed for MP, where the pore-forming activity leads to cell death. Our results indicate that hydrophobic moment modified by amino acid substitution may enhance MP selectivity.

Population Structure Analysis of Carbapenem-Resistant Acinetobacter baumannii Clinical Isolates from Brazil Reveals Predominance of Clonal Complexes 1, 15, and 79.

The population structure of 71 carbapenem-resistantAcinetobacter baumanniiclinical isolates from several hospitals in Brazil was investigated by ApaI pulsed-field gel electrophoresis,blaOXA-51-like subtyping, and multilocus sequence typing (Institute Pasteur scheme). In addition to the predominance of strains carryingblaOXA-23, we detected the presence ofblaOXA-72andblaOXA-231 We observed a predominance of clonal complex 1 (CC1), CC15, and CC79 and representative strains of the worldwide-disseminated international clone I.

Synergistic effects of sulbactam in multi-drug-resistant Acinetobacter baumannii.

Acinetobacter baumannii is a frequently isolated etiologic agent of nosocomial infections, especially in intensive care units. With the increase in multi-drug resistance of A. baumannii isolates, finding appropriate treatment alternatives for infections caused by these bacteria has become more difficult, and available alternate treatments include the use of older antibiotics such as colistin or a combination of antibiotics. The current study aimed to evaluate the in vitro efficacy of various antibiotic combinations against multi-drug resistant A. baumannii strains. Thirty multi-drug and carbapenem resistant A. baumannii strains isolated at the Ankara Training and Research Hospital between June 2011 and June 2012 were used in the study. Antibiotic susceptibility tests and species-level identification were performed using conventional methods and the VITEK 2 system. The effects of meropenem, ciprofloxacin, amikacin, tigecycline, and colistin alone and in combination with sulbactam against the isolates were studied using Etest (bioMérieux) in Mueller-Hinton agar medium. Fractional inhibitory concentration index (FIC) was used to determine the efficacy of the various combinations. While all combinations showed a predominant indifferent effect, a synergistic effect was also observed in 4 of the 5 combinations. Synergy was demonstrated in 43% of the isolates with the meropenem-sulbactam combination, in 27% of the isolates with tigecycline-sulbactam, and in 17% of the isolates with colistin-sulbactam and amikacin-sulbactam. No synergy was detected with the sulbactam-ciprofloxacin combination and antagonism was detected only in the sulbactam-colistin combination (6.66% of the isolates). Antibiotic combinations can be used as an alternative treatment approach in multi-drug resistant A. baumannii infections.

Synergistic effects of sulbactam in multi-drug-resistant Acinetobacter baumannii

Abstract Acinetobacter baumannii is a frequently isolated etiologic agent of nosocomial infections, especially in intensive care units. With the increase in multi-drug resistance of A. baumannii isolates, finding appropriate treatment alternatives for infections caused by these bacteria has become more difficult, and available alternate treatments include the use of older antibiotics such as colistin or a combination of antibiotics. The current study aimed to evaluate the in vitro efficacy of various antibiotic combinations against multi-drug resistant A. baumannii strains. Thirty multi-drug and carbapenem resistant A. baumannii strains isolated at the Ankara Training and Research Hospital between June 2011 and June 2012 were used in the study. Antibiotic susceptibility tests and species-level identification were performed using conventional methods and the VITEK 2 system. The effects of meropenem, ciprofloxacin, amikacin, tigecycline, and colistin alone and in combination with sulbactam against the isolates were studied using Etest (bioMérieux) in Mueller-Hinton agar medium. Fractional inhibitory concentration index (FIC) was used to determine the efficacy of the various combinations. While all combinations showed a predominant indifferent effect, a synergistic effect was also observed in 4 of the 5 combinations. Synergy was demonstrated in 43% of the isolates with the meropenem-sulbactam combination, in 27% of the isolates with tigecycline-sulbactam, and in 17% of the isolates with colistin-sulbactam and amikacin-sulbactam. No synergy was detected with the sulbactam-ciprofloxacin combination and antagonism was detected only in the sulbactam-colistin combination (6.66% of the isolates). Antibiotic combinations can be used as an alternative treatment approach in multi-drug resistant A. baumannii infections.