Isolation and identification of Acinetobacter species with special reference to antibiotic resistance

Whole-genome sequencing of two multidrug-resistant acinetobacter baumannii strains isolated from a neonatal intensive care unit in Egypt: a prospective cross-sectional study

BACKGROUND

Acinetobacter baumannii (A. baumannii) is a life-threatening and challenging pathogen. In addition, it accounts for numerous serious infections, particularly among immunocompromised patients. Resistance to nearly all clinically used antibiotics and their ability to spread this resistance is one of the most important concerns related to this bacterium.

OBJECTIVES

This study describes different molecular mechanisms of two multidrug-resistant A. baumannii isolates obtained from endotracheal aspirates collected from the neonatal intensive care unit (NICU), Ain Shams University Hospital, Egypt.

METHODS

Following the identification of two isolates, they were examined for susceptibility to antimicrobial agents. This was followed by multilocus sequence typing as well as whole-genome sequence (WGS). Additionally, a Pathosystems Resources Integration Center (PATRIC) analysis was performed.

RESULTS

Two isolates, Ab119 and Ab123, exhibited resistance to all tested antibiotics except for tigecycline and colistin. The WGS analysis of antimicrobial resistance genes (AMR) indicated that both isolates shared beta-lactam, aminoglycoside, macrolides, and sulfonamide resistance genes. Furthermore, each strain revealed different resistance genes such as blaNDM-1, blaNDM-10, OXA-64, aph (3')-VI, Tet-B in Ab119 strain and blaOXA-68, blaPER-1, blaPER-7, Tet-39 in Ab123 strain. Multiple efflux pump genes were detected. Multilocus sequence typing indicated that both isolates belong to the same sequence type (ST931), which belongs to international clone (IC3). Both isolates exhibited the presence of multiple mobile genetic elements (MGEs), but no plasmid was detected in either of them.

CONCLUSIONS

A low prevalence of the IC3 sequence type was identified among two A. baumannii isolates obtained from the NICU in Egypt, exhibiting a high resistance level. Healthcare workers must have knowledge regarding the prevalence of A. baumannii among different populations in order to administer suitable treatment, improve patient outcomes, and apply effective infection control practices.

Carbapenem Resistance in Acinetobacter calcoaceticus-baumannii Complex Isolates From Kathmandu Model Hospital, Nepal, Is Attributed to the Presence of bla OXA-23-like and bla NDM-1 Genes

The Acinetobacter calcoaceticus-baumannii (ACB) complex, also known as ACB complex, consists of four bacterial species that can cause opportunistic infections in humans, especially in hospital settings. Conventional therapies for susceptible strains of the ACB complex include broad-spectrum cephalosporins, β-lactam/β-lactamase inhibitors, and carbapenems. Unfortunately, the effectiveness of these antibiotics has declined due to increasing rates of resistance. The predominant resistance mechanisms identified in the ACB complex involve carbapenem-resistant (CR) oxacillinases and metallo-β-lactamases (MBLs). This research, conducted at Kathmandu Model Hospital in Nepal, sought to identify genes associated with CR, specifically blaNDM-1, blaOXA-23-like, and blaOXA-24-like genes in carbapenem-resistant Acinetobacter calcoaceticus-baumannii (CR-ACB) complex. Additionally, the study is aimed at identifying the ACB complex through the sequencing of the 16s rRNA gene. Among the 992 samples collected from hospitalized patients, 43 (approximately 4.334%) tested positive for the ACB complex. These positive samples were mainly obtained from different hospital units, including intensive care units (ICUs); cabins; and neonatal, general, and maternity wards. The prevalence of infection was higher among males (58.14%) than females (41.86%), with the 40-50 age group showing the highest infection rate. In susceptibility testing, colistin and polymyxin B exhibited a susceptibility rate of 100%, whereas all samples showed resistance to third-generation cephalosporins. After polymyxins, gentamicin (30.23%) and amikacin (34.88%) demonstrated the highest susceptibility. A substantial majority (81.45%) of ACB complex isolates displayed resistance to carbapenems, with respiratory and pus specimens being the primary sources. Polymerase chain reaction (PCR) revealed that the primary CR gene within the ACB complex at this hospital was bla OXA-23-like, followed by bla NDM-1. To ensure the accuracy of the phenotypic assessment, 12 samples were chosen for 16s rRNA sequencing using Illumina MiSeq™ to confirm that they are Acinetobacter species. QIIME 2.0 analysis confirmed all 12 isolates to be Acinetobacter species. In the hospital setting, a substantial portion of the ACB complex carries CR genes, rendering carbapenem ineffective for treatment.

Ciprofloxacin- and levofloxacin-loaded nanoparticles efficiently suppressed fluoroquinolone resistance and biofilm formation in Acinetobacter baumannii

The spread of fluoroquinolone (FQ) resistance in Acinetobacter baumannii represents a critical health threat. This study aims to overcome FQ resistance in A. baumannii via the formulation of polymeric nanoFQs. Herein, 80 A. baumannii isolates were obtained from diverse clinical sources. All A. baumannii isolates showed high resistance to most of the investigated antimicrobials, including ciprofloxacin (CIP) and levofloxacin (LEV) (97.5%). FQ resistance-determining regions of the gyrA and parC genes were the most predominant resistant mechanism, harbored by 69 (86.3%) and 75 (93.8%) of the isolates, respectively. Additionally, plasmid-mediated quinolone resistance genes aac(6')-Ib and qnrS were detected in 61 (76.3%) and 2 (2.5%) of the 80 isolates, respectively. The CIP- and LEV-loaded poly ε-caprolactone (PCL) nanoparticles, FCIP and FLEV, respectively, showed a 1.5-6- and 6-12-fold decrease in the MIC, respectively, against the tested isolates. Interestingly, the time kill assay demonstrated that MICs of FCIP and FLEV completely killed A. baumannii isolates after 5-6 h of treatment. Furthermore, FCIP and FLEV were found to be efficient in overcoming the FQ resistance mediated by the efflux pumps in A. baumannii isolates as revealed by decreasing the MIC four-fold lower than that of free CIP and LEV, respectively. Moreover, FCIP and FLEV at 1/2 and 1/4 MIC significantly decreased biofilm formation by 47-93% and 69-91%, respectively. These findings suggest that polymeric nanoparticles can restore the effectiveness of FQs and represent a paradigm shift in the fight against A. baumannii isolates.

Assessment of Bacteria Contaminants in Different Zones and Point Sources of Sandy Beaches in Accra, Ghana

Background

Bacteria are ubiquitous in the marine environment. Increasing concern for human health has led to growing interest in contamination on public beaches. The presence of pathogenic microorganisms originating from anthropogenic activities such as defecation and disposal of sewage on beaches are of special concern. In this study, presence of pathogenic bacteria and bacterial load in beach zones and point sources were investigated.

Methods

Sand core samples from the subtidal zone, intertidal zone, supratidal zone and point sources from 5 beaches in Accra, Ghana, were collected and analysed. Total aerobic, coliform and Escherichia (E. coli) counts were determined for each zone in the respective beaches. Bacteria isolates were presumptively identified using biochemical tests and confirmed with MALDI-TOF MS.

Results

Mean total aerobic count and total coliform counts ranged from 2.10 to 3.01 log CFU/g and 0.29 to 2.18 log CFU/g respectively while E. coli counts ranged from 0.12 to 1.71 log CFU/g for the beaches. Total aerobic count from point sources was 2.4-folds higher than the subtidal zone while total coliform counts were 5-folds higher in the point sources compared to the supratidal zone. Point sources had 10 times (P = .0016) more E. coli counts as compared to the subtidal zone. Isolates recovered (n = 35) belonged to 10 bacteria genera. These were Bacillus spp. (25.7%), Acinetobacter spp. (14.3%), Aeromonas spp. (14.3%), Klebsiella pneumoniae (14.3%), Aerococcus viridans (8.6%), Staphylococcus spp. (8.6%), Shewanella profunda (5.7%), Rheinheimera soli (2.9%), Pseudomonas aeruginosa (2.9%), and Exiguobacterium aurantiacum (2.9%).

Conclusion

Point sources are major contributors to contamination on beaches. The presence of potentially pathogenic bacteria in beach sand could be a public health risk. Sensitization on cleanliness in the marine environment including beaches in Ghana is needed to enhance public health and safety.

Identification and genome-wide analysis provide insights into the genetic diversity and biotechnological potentials of novel cold-adapted Acinetobacter strain

Extreme cold environments, such as polar regions or high-altitude mountains, are known for their challenging conditions including low temperatures, high salinity, and limited nutrient availability. Microbes that thrive in these environments have evolved specialized strategies to survive and function under such harsh conditions. The study aims to identify, sequence the genome, perform genome assembly, and conduct a comparative genome-wide analysis of Acinetobacter sp. strain P1, which was isolated from the Batura glacier regions of Pakistan. A basic local alignment search tool of NCBI using 16 s RNA gene sequence confirmed the strain Acinetobacter following phylogenetic analysis revealed that strain P1 clustered with Acinetobacter sp. strain AcBz01. The high-throughput Genome sequencing was done by the NovaSeq 6000 sequencing system following de novo genome assembly reported 23 contigs, a genome size of 3,732,502 bp containing approximately 3489 genes and 63 RNAs (60 tRNA, 3 rRNA). The comparative genome analysis revealed that Acinetobacter sp. strain P1 exhibited the highest homology with the Acinetobacter baumannii ATCC 17978 genome and encompassed 1668 indispensable genes, 1280 conserved genes 1821 specific genes suggesting high genomic plasticity and evolutionary diversity. The genes with functional assignments include exopolysaccharide phosphotransferase enzyme, cold-shock proteins, T6SS, membrane modifications, antibiotic resistance, and set of genes related to a wide range of metabolic characteristics such as exopolysaccharides were also present. Moreover, the structural prediction analysis of EPS proteins reveals that structural flexibility allows for conformational modifications during catalysis, which boosts or increases the catalytic effectiveness at lower temperatures. Overall, the identification of Acinetobacter, a cold-adapted bacterium, offers promising applications in bioremediation, enzyme production, food preservation, pharmaceutical development, and astrobiology. Further research and exploration of these microorganisms can unlock their full biotechnological potential and contribute to various industries and scientific endeavors.

Molecular Characterization of Carbapenem-Resistant Acinetobacter baumannii with Special Reference to Carbapenemases: A Systematic Review

Carbapenemases are β-lactamase enzymes that hydrolyze a variety of β-lactams including carbapenem and belong to different Ambler classes (A, B, D). These enzymes can be encoded by plasmid or chromosomal-mediated genes. The major issues associated with carbapenemases-producing organisms are compromising the activity and increasing the resistance to carbapenems which are the last resort antibiotics used in treating serious infections. The global increase of pathogen, carbapenem-resistant A. baumannii has significantly threatened public health. Thus, there is a pressing need for a better understanding of this pathogen, to know the various carbapenem resistance encoding genes and dissemination of resistance genes from A. baumannii which help in developing strategies to overcome this problem. The horizontal transfer of resistant determinants through mobile genetic elements increases the incidence of multidrug, extensive drug, and Pan-drug resistant A. baumannii. Therefore, the current review aims to know the various mechanisms of carbapenem resistance, categorize and discuss carbapenemases encoding genes and various mobile genetic elements, and the prevalence of carbapenemase genes in recent years in A. baumannii from various geographical regions.

Multidrug-Resistant Acinetobacter: Detection of ESBL, MBL, bla NDM-1 Genotype, and Biofilm Formation at a Tertiary Care Hospital in Eastern Nepal

Background

The Acinetobacter species is an important hospital-acquired pathogen. The rapid development of resistance to multiple drugs and the ability to form biofilm make these bacteria more adaptable to survive in healthcare facilities, thus posing a challenge to their effective management.

Objective

This study aimed to characterize clinical isolates of Acinetobacter spp and to study their antimicrobial susceptibility patterns and ability to form biofilm. Resistant Acinetobacter was further analyzed for the detection of extended-spectrum β-lactamases (ESBLs), metallo β-lactamases (MBLs), carbapenemase production, and presence of blaNDM-1 gene.

Materials and Methods

A total of 324 Acinetobacter species were isolated from various clinical specimens which were submitted to the Department of Microbiology, B.P. Koirala Institute of Health Sciences, Dharan, Nepal, and were studied for antibiotic susceptibility testing, detection of ESBL and MBL production, and formerly biofilm formation was performed by standard microbiological methods. PCR was carried out to determine the presence of the blaNDM-1 gene.

Results

The predominant Acinetobacter species isolated was A calcoaceticus-baumannii Complex (Acb complex) 167 (51.5%). Among those, all A. species 128 (40%) were multidrug resistant (MDR). In which 13 (4.0%) were ESBL producers, 70 (61.9%) were MBL, and 12 (10.6%) were carbapenemases producers. The blaNDM1 gene was present in 33 isolates. Thirty-seven percent (121/324) of isolates formed biofilm. The majority of A. species were resistant to cefotaxime 73.8% (239) and cefepime 74.4% (241). A significant proportion of biofilm producers were MDR (p < 0.001).

Conclusion

Drug-resistant Acinetobacter formed a substantial proportion of this hospital's samples with a large presence of the bla NDM-1 gene. A matter of great concern is the association of multidrug-resistant phenotype with biofilm formation. This situation warranted stringent surveillance and adherence to infection prevention and control practices.

The role of pmrCAB genes in colistin-resistant Acinetobacter baumannii

The progressively increasing antimicrobial-resistant Acinetobacter baumannii infections have enforced the use of colistin as the last option for therapy, resulting in the colistin resistance evolution. This work aimed to study the pmrCAB expression in A. baumannii isolates as well as the presence of the mcr-1 gene. Colistin MICs of 100 A. baumannii isolates were measured using the broth microdilution assay. In four colistin-susceptible and four colistin-resistant isolates, the relative expression of the pmrA, pmrB, and pmrC genes was determined using reverse transcription PCR, and then selected isolates were sequenced using the Sanger technique. Finally, the mcr-1 gene was detected using conventional PCR. The colistin resistance rate among the studied isolates was 49%. The expression levels of pmrA and pmrB were statistically significantly higher in colistin-resistant isolates than in colistin-susceptible ones, while the pmrC expression had no statistically significant change. There was a weak positive correlation between colistin MICs and the expression levels of each of the pmrA and pmrB genes. By sequencing, two colistin-resistant strains with low pmrCAB expression showed insertion mutations 3277188_3277189T in pmrB and 1185149_1185150T in pmrC. Only one isolate (1%) was positive for the presence of mcr-1. We concluded that pmrCAB increased expression and/or mutations may cause colistin resistance in A. baumannii. However, increased pmrC expression may not necessarily result in colistin resistance. In Egypt, this is the first study to reveal the existence of mcr-1 in A. baumanni. This should attract attention in clinical settings due to the ultimate tendency of spreading colistin resistance.

Role of Efflux Pumps in Reduced Susceptibility to Tigecycline among Clinical Isolates of Acinetobacter baumannii

Background

Acinetobacter baumannii (A. baumannii) is a very well-known emerging pathogen and has become a major burden on healthcare system especially in intensive care units (ICUs). Tigecycline is the last resort drug for treatment of multidrug-resistant A. baumannii infections. However, non-susceptibility to this drug is a rising problem. Resistance to tigecycline is mediated by Resistance-nodulation-cell division (RND) efflux pumps.

Objective

This study was done to detect efflux pump genes (adeABC) and regulator genes (adeS,adeR) responsible for tigecycline resistance among the clinical isolates of A. baumannii.

Materials and Methods

A total of 150 OXA-51 confirmed clinical isolates were subjected for tigecycline susceptibility test by broth microdilution (BMD) method. All isolates irrespective of their MIC were subjected to conventional PCR for detection of efflux genes (adeABC) and regulator genes (adeRS).

Results

Prevalence of tigecycline resistance was found to be 14 (9.33%) by the reference broth microdilution method (BMD). Overall prevalence of efflux genes was highest for adeB (69%) and lowest for adeR (29%). Combination of genes especially three, four or five were found more prevalent among resistant isolates with higher minimum inhibitory concentration (MIC).

Conclusion

Combination of efflux genes confer higher MIC and can be a major contributor for resistance to tigecycline.

Evolutionarily stable gene clusters shed light on the common grounds of pathogenicity in the Acinetobacter calcoaceticus-baumannii complex

Nosocomial pathogens of the Acinetobacter calcoaceticus-baumannii (ACB) complex are a cautionary example for the world-wide spread of multi- and pan-drug resistant bacteria. Aiding the urgent demand for novel therapeutic targets, comparative genomics studies between pathogens and their apathogenic relatives shed light on the genetic basis of human-pathogen interaction. Yet, existing studies are limited in taxonomic scope, sensing of the phylogenetic signal, and resolution by largely analyzing genes independent of their organization in functional gene clusters. Here, we explored more than 3,000 Acinetobacter genomes in a phylogenomic framework integrating orthology-based phylogenetic profiling and microsynteny conservation analyses. We delineate gene clusters in the type strain A. baumannii ATCC 19606 whose evolutionary conservation indicates a functional integration of the subsumed genes. These evolutionarily stable gene clusters (ESGCs) reveal metabolic pathways, transcriptional regulators residing next to their targets but also tie together sub-clusters with distinct functions to form higher-order functional modules. We shortlisted 150 ESGCs that either co-emerged with the pathogenic ACB clade or are preferentially found therein. They provide a high-resolution picture of genetic and functional changes that coincide with the manifestation of the pathogenic phenotype in the ACB clade. Key innovations are the remodeling of the regulatory-effector cascade connecting LuxR/LuxI quorum sensing via an intermediate messenger to biofilm formation, the extension of micronutrient scavenging systems, and the increase of metabolic flexibility by exploiting carbon sources that are provided by the human host. We could show experimentally that only members of the ACB clade use kynurenine as a sole carbon and energy source, a substance produced by humans to fine-tune the antimicrobial innate immune response. In summary, this study provides a rich and unbiased set of novel testable hypotheses on how pathogenic Acinetobacter interact with and ultimately infect their human host. It is a comprehensive resource for future research into novel therapeutic strategies.

The spread of multi- and pan-drug resistant bacterial pathogens is a worldwide threat to human health. Understanding the genetics of host colonization and infection can substantially help in devising novel ways of treatment. Acinetobacter baumannii, a nosocomial pathogen ranked top by the World Health Organization in the list of bacteria for which novel therapeutic approaches are needed, is a prime example. Here, we have carved out the genetic make-up that distinguishes A. baumannii and its pathogenic next relatives from other and mostly apathogenic Acinetobacter species. We found a rich spectrum of pathways and regulatory modules that reveal how the pathogens have modified biofilm formation, iron scavenging, and their carbohydrate metabolism to adapt to their human host. Among these, the capability to metabolize kynurenine is particularly intriguing. Humans produce this substance to contain bacterial invaders and to fine-tune the innate immune response. But A. baumannii and closely related pathogens found a way to feed on kynurenine. This suggests that the pathogens might be able to dysregulate the human immune response. In summary, our study substantially deepens the understanding of how a highly critical pathogen interacts with its host, which substantially eases the identification of novel targets for innovative therapeutic strategies.

Multidrug-resistant Acinetobacter baumannii infections: looming threat in the Indian clinical setting

INTRODUCTION

The recent increase in multidrug-resistant strains of A. baumannii has increased the incidences of ventilator-associated pneumoniae, catheter-associated urinary tract infections, and central line-associated blood stream infections, together increasing hospital stay, treatment cost, and mortality. Resistance genes blaOXA and blaNDM are dominant in India. Carbapenem-resistant A. baumannii (CRAB) International clone-2 (IC-2) are rising in India. High dependency on carbapenems and last-resort combination of tigecycline and polymyxins have aggravated outcomes. Despite nursing barriers, ward closure, environmental disinfections etc for detecting and controlling transmission, MDR isolates and CRAB nosocomial outbreaks continue. Treatment cost overruns by AMR adversely affect 80% of Indians without insurance cover.

AREA COVERED

This narrative review will cover epidemiology, resistance pattern, genetic diversity, device-related infection, cost, and mortality due to multidrug-resistant and CRAB in India. A comprehensive literature search in PubMed and Google Scholar using appropriate keywords at different time points yielded relevant articles.

EXPERT OPINION

It is challenging to enforce policies to control MDR A. baumannii in India. Government and hospitals should enforce stringent infection control measures, surveillance, and antimicrobial stewardship to prevent further spread and emergence of more virulent and resistant strains. Knowledge on antibiotic resistance mechanisms can help design novel antibiotics that can evade, resistance.

Molecular Characterization Identifies Upstream Presence of ISAba1 to OXA Carbapenemase Genes in Carbapenem-Resistant Acinetobacter baumannii Isolated from a Tertiary Care Hospital in Western Maharashtra

Background  Evaluating the expression pattern of oxacillinases (OXA) carbapenemases is essential to understand the prevalence and spread of carbapenem resistance Acinetobacter baumannii .

Objectives  The aim of the study is to evaluate the presence of OXA carbapenemase genes and IS Aba1 upstream to these genes in carbapenem-resistant A. baumannii clinical isolates.

Materials and Methods   A. baumannii isolated from clinical samples were phenotypically identified and antibiotics sensitivity was performed. Multiplex polymerase chain reaction (PCR) was used to detect OXA51-like gene, OXA carbapenemases genes (OXA-23-like, OXA-24-like, and OXA-58-like), and IS Aba1 in carbapenem-resistant isolates.

Results  Out of 55 Acinetobacter isolates, 54 were confirmed as A. baumannii by PCR. Bla_OXA-23 -like gene was observed in 51 isolates of A. baumannii and none of the isolates showed the presence of bla_OXA-24 -like and bla_OXA-58 -like genes. Presence of IS Aba1 upstream to OXA-23-like gene, OXA-51-like gene, and both OXA-51-like/OXA-23-like genes was observed in 51, 7, and 4 A. baumannii isolates, respectively.

Conclusion  The genetic pattern of carbapenem-resistant A. baumannii isolated in this study was unique, which should be factored for clinical protocols to manage infections caused by emerging resistant strains of A. baumannii .

Photoelimination Potential of Chitosan Nanoparticles-Indocyanine Green Complex Against the Biological Activities of Acinetobacter baumannii Strains: A Preliminary In Vitro Study in Burn Wound Infections

Introduction: Acinetobacter baumannii strains are important agents causing serious nosocomial infections including soft-tissue and skin infections in patients with burn wounds which have become resistant to several classes of antibiotics. Antimicrobial photodynamic therapy (aPDT) as an alternative antimicrobial procedure is suggested for the treatment of these kinds of infections. The aim of the current study is to evaluate the antibacterial and anti-biofilm efficiency of aPDT by the utilization of an improved form of indocyanine green (ICG) which is encapsulated in chitosan nanoparticles (NCs@ICG). Methods: NCs@ICG were synthesized and confirmed by the scanning electron microscope (SEM). aPDT was performed using NCs@ICG with an 810 nm wavelength of the diode laser at the fluency of 31.2 J/cm² on 50 A. baumannii strains isolated from burn wounds. The antibacterial and antibiofilm potential of NCs@ICG-aPDT was determined via the colony forming unit (CFU)/mL and crystal violet assays, respectively. In addition, microbial biofilm degradation was evaluated by the SEM. Results: According to the results, NCs@ICG-aPDT showed a significant reduction of 93.2% on the CFU/ mL of planktonic A. baumannii strains compared to the control group (untreated group; P < 0.05). In addition, the biofilm formation of A. baumannii strains was significantly reduced by 55.3% when the bacteria were exposed to NCs@ICG-aPDT (P < 0.05). In contrast, NCs@ICG, ICG, and the diode laser alone were not able to inhibit the CFU/mL and biofilm of A. baumannii strains (P > 0.05). Based on the results of SEM images, NCs@ICG-aPDT disrupted the biofilm structure of A. baumannii strains more than other groups. Conclusion: NCs@ICG-aPDT demonstrates a promising treatment candidate for exploitation in wound infections against both planktonic and biofilm forms of A. baumannii strains.

The so-called "bovine aortic arch": a possible biomarker for embolic strokes?

PURPOSE

To examine the prevalence of the so-called bovine aortic arch variation (common origin of the brachiocephalic trunk and the left common carotid artery) in embolic stroke patients, compared with a control group.

METHODS

Aortic arch branching patterns were retrospectively evaluated in 474 individuals with (n = 152) and without (n = 322) acute embolic stroke of the anterior circulation. Contrast-enhanced CT scans of the chest and neck (arterial contrast phase, 1-2-mm slice thickness) were used to evaluate aortic arch anatomy. The stroke cohort included 152 patients who were treated for embolic strokes of the anterior circulation between 2008 and 2018. A total of 322 randomly selected patients who had received thoracic CT angiographies within the same time frame were included as a control group.

RESULTS

With a prevalence of 25.7%, the bovine aortic arch variant was significantly more common among patients suffering from embolic strokes, compared with 17.1% of control patients (p = 0.039, OR = 1.67, 95%CI = 1.05-1.97). Stroke patients were more likely to show the bovine arch subtype B (left common carotid artery originating from the brachiocephalic trunk instead of the aortic arch) (10.5% vs. 5.0%, p = 0.039, OR = 2.25, 95%CI = 1.09-4.63), while subtype A (V-shaped common aortic origin of the brachiocephalic trunk and the left carotid) was similarly common in both groups. There was no significant difference regarding the frequency of other commonly observed variant branching patterns of the aortic arch.

CONCLUSION

The bovine aortic arch, particularly the bovine arch subtype B, was significantly more common among embolic stroke patients. This might be due to altered hemodynamic properties within the bovine arch.

High antimicrobial resistant rates among Gram-negative pathogens in intensive care units. A retrospective study at a tertiary care hospital in Southwest Saudi Arabia

OBJECTIVES

To determine the distribution and resistance profiles of Gram-negative bacteria (GNB) in intensive care units (ICUs) at King Abdullah Hospital in Bisha, Saudi Arabia. Methods: A record based retrospective study was conducted from December 2016 to January 2018. In total, 3736 non-duplicate clinical specimens from the general intensive care unit (ICU), neonatal ICU (NICU), and coronary CU (CCU) were analyzed for pathogens. Results: Of 3736 specimens, 9.6% (358) were positive for pathogens, and GNB constituted the majority (290/358; 81%). Acinetobacter is predominant in the general ICU, whereas Klebsiella pneumoniae is common in the NICU and CCU. Overall, GNB revealed a high resistance rate for cefuroxime (75.8%) trimethoprim/sulfamethoxazole (73.4%), cefotaxime (72.9%), aztreonam (64.6%), piperacillin (62.1%), and ciprofloxacin (61.5%). Acinetobacter revealed a high resistance (93.4% to 97.5%) to all antimicrobials except colistin (4%). Klebsiella pneumoniae showed a high resistance to trimethoprim/sulfamethoxazole (71.8%), cefotaxime (71.4%) and aztreonam (65.2%). Pseudomonas aeruginosa showed good activity for aminoglycosides but increasing resistance for cephalosporins and meropenem. GNB exhibited a high rate of multi-drug-resistant (MDR) phenotypes (67.9%) with a higher level among Acinetobacter spp. (97.5%). There were no significant differences in the resistance rates of GNB from different ICUs except for imipenem (p=0.002) and ciprofloxacin (p=0.003).  Conclusions: Increased antimicrobial resistance with high proportions of MDR patterns were found among GNB from ICUs. Comprehensive surveillance programs are needed to track the origins and emergence pathways of resistant pathogens.

Antimicrobial Susceptibility Patterns of an Emerging Multidrug Resistant Nosocomial Pathogen: Acinetobacter baumannii

Multidrug-resistant (MDR) Acinetobacter baumannii (A. baumannii) bacterium, a nosocomial pathogen associated with a high mortality rate and limited therapeutic options have emerged as a serious problem throughout the world. The present study aimed to assess the current levels of antibiotic susceptibility among the isolates of Acinetobacter species. The sensitivity patterns were analysed from various clinical specimens obtained from both in-patients and outpatients of a teaching hospital. Isolation was performed on 5% sheep blood agar and MacConkey agar. Urine samples were inoculated into CLED agar. Antibiotic susceptibility was performed by the disc diffusion method. A total of 16,452 samples were collected. The total number of samples positive for Acinetobacter species was 67 (0.4%). The highest number of isolates 26 (38.8%) were obtained from urine. Majority 80.3% of the isolates exhibited resistance to three or more classes of antibiotics. All isolates were susceptible to colistin (100%). The susceptibility rate of A. baumannii isolates was 80% for tigecycline and 53.3% for carbapenem. Combination therapies including colistin and tigecycline seem to be the rational treatment for MDR A. baumannii until new alternatives come forward.