GES-11-producing Acinetobacter baumannii clinical isolates from Tunisian hospitals: Long-term dissemination of GES-type carbapenemases in North Africa

Screening for Resistant Bacteria, Antimicrobial Resistance Genes, Sexually Transmitted Infections and Schistosoma spp. in Tissue Samples from Predominantly Vaginally Delivered Placentae in Ivory Coast and Ghana

Medical complications during pregnancy have been frequently reported from Western Africa with a particular importance of infectious complications. Placental tissue can either become the target of infectious agents itself, such as, e.g., in the case of urogenital schistosomiasis, or be subjected to contamination with colonizing or infection-associated microorganisms of the cervix or the vagina during vaginal delivery. In the retrospective cross-sectional assessment presented here, the quantitative dimension of infection or colonization with selected resistant or pathogenic bacteria and parasites was regionally assessed. To do so, 274 collected placental tissues from Ivory Coastal and Ghanaian women were subjected to selective growth of resistant bacteria, as well as to molecular screening for beta-lactamase genes, Schistosoma spp. and selected bacterial causative agents of sexually transmitted infections (STI). Panton-Valentine-negative methicillin-resistant Staphylococcus aureus (MRSA) was grown from 1.8% of the tissue samples, comprising the spa types t008 and t688, as well as the newly detected ones, t12101 (n = 2) and t12102. While the culture-based recovery of resistant Enterobacterales and nonfermentative rod-shaped Gram-negative bacteria failed, molecular assessments confirmed beta-lactamase genes in 31.0% of the samples with multiple detections of up to four resistance genes per sample and blaCTX-M, blaIMP, blaGES, blaVIM, blaOXA-58-like, blaNDM, blaOXA-23-like, blaOXA-48-like and blaKPC occurring in descending order of frequency. The beta-lactamase genes blaOXA-40/24-like, blaNMC_A/IMI, blaBIC, blaSME, blaGIM and blaDIM were not detected. DNA of the urogenital schistosomiasis-associated Schistosoma haematobium complex was recorded in 18.6% of the samples, but only a single positive signal for S. mansoni with a high cycle-threshold value in real-time PCR was found. Of note, higher rates of schistosomiasis were observed in Ghana (54.9% vs. 10.3% in Ivory Coast) and Cesarean section was much more frequent in schistosomiasis patients (61.9% vs. 14.8% in women without Schistosoma spp. DNA in the placenta). Nucleic acid sequences of nonlymphogranuloma-venereum-associated Chlamydia trachomatis and of Neisseria gonorrhoeae were recorded in 1.1% and 1.9% of the samples, respectively, while molecular attempts to diagnose Treponema pallidum and Mycoplasma genitalium did not lead to positive results. Molecular detection of Schistosoma spp. or STI-associated pathogens was only exceptionally associated with multiple resistance gene detections in the same sample, suggesting epidemiological distinctness. In conclusion, the assessment confirmed considerable prevalence of urogenital schistosomiasis and resistant bacterial colonization, as well as a regionally expected abundance of STI-associated pathogens. Continuous screening offers seem advisable to minimize the risks for the pregnant women and their newborns.

Molecular characterization of multidrug resistant Acinetobacter baumannii clinical isolates from Alexandria, Egypt

Carbapenem resistant Acinetobacter baumannii is a major global concern, especially in countries of the Middle East and North Africa, where the antibiotic resistance rates are on the rise. The aim of this study was to study the genomic characteristics and antimicrobial susceptibility profile of thirty-six multidrug resistant A. baumannii clinical isolates obtained in hospitals from Alexandria, Egypt. Antibiotic resistance rates were estimated by determination of Minimum Inhibitory Concentrations. Carbapenemase genes, other antibiotic resistance genes and virulence factors were then screened by the use of Whole Genome Sequencing. Isolates were also subjected to Multi Locus Sequence Typing (MLST) using the Pasteur Scheme and to core genome MLST to study their clonal relatedness. In addition, plasmid analysis was performed by the use of a commercial kit and S1- Pulsed Field Gel Electrophoresis, and Hybridization experiments with DIG-labeled DNA probes for bla NDM-1, blaPER-7 and bla GES-like were performed to locate these genes. The majority of isolates were resistant to β-lactams (including carbapenems), fluoroquinolones, aminoglycosides and trimethoprim; and some showed resistance to cefiderocol and minocycline. We identified 8 different bla OXA-51-like variants including bla OXA-51, bla OXA-64, bla OXA-65, bla OXA-66, bla OXA-68, bla OXA-91, bla OXA-94 and bla OXA-336; bla OXA-23, bla NDM-1, bla PER-7, bla GES-like and bla ADC-like and other antibiotic resistance genes, some of these genes were within transposons or class 1 integrons. Multiple virulence factors responsible for adherence, biofilm production, type II and type VI secretion systems, exotoxins, exoenzymes, immune modulation and iron uptake were observed and 34 out of 36 isolates showed motility. Thirty-five out of 36 isolates clustered with International Clones 2, 4, 5, 7, 8 and 9; and 9 STs were identified including ST570, ST2, ST600, ST15, ST113, ST613, ST85, ST158, ST164. Plasmids ranging in size from 1.7 to 70 kb were found; bla NDM-1 and blaPER-7 genes were located in the chromosome and bla GES-like genes were simultaneously located in the chromosome and in a plasmid of 70kb. In conclusion, this study revealed a wide spectrum of antibiotic resistance genes and a variety of lineages among A. baumannii isolated in hospitals from Alexandria, and highlights the importance of investigating the molecular epidemiology to control the spread of multi-drug resistant isolates.

The Prevalence of Multidrug-Resistant Acinetobacter baumannii and Its Vaccination Status among Healthcare Providers

There is growing concern among healthcare providers worldwide regarding the prevalence of multidrug-resistant Acinetobacter baumannii (A. baumannii). Some of the worst hospital-acquired infections, often in intensive care units (ICUs), are caused by this bacterial pathogen. In recent years, the rise in multidrug-resistant A. baumannii has been linked to the overuse of antimicrobial drugs and the lack of adequate infection control measures. Infections caused by this bacterial pathogen are the result of prolonged hospitalization and ICU stays, and they are associated with increased morbidity and mortality. This review outlines the epidemiology, risk factors, and antimicrobial resistance associated with A. baumannii in various countries, with a special focus on the Kingdom of Saudi Arabia. In response to the growing concern regarding this drug-resistant bacteria, fundamental information about its pathology has been incorporated into the development of vaccines. Although these vaccines have been successful in animal models, their effectiveness in humans remains unproven. The review will discuss the development of A. baumannii vaccines, potential related obstacles, and efforts to find an effective strategy against this pathogen.

Multidrug-resistant Acinetobacter baumannii in healthcare settings in Africa

The emergence of multidrug-resistant Acinetobacter baumannii is a major concern to healthcare providers and facilities in many parts of the world. This bacterial pathogen is commonly implicated in hospital-acquired infections, particularly in critically ill patients admitted to the intensive care unit (ICU). The extensive use of antibiotics, particularly in ICUs, and the lack of proper infection control interventions in many hospitals have led to an increased emergence of multidrug-resistant A. baumannii. Infections due to multidrug-resistant A. baumannii are associated with prolonged hospital stays and high morbidity and mortality, particularly among hospitalized ICU patients. The lack of antibiotic stewardship programmes in many healthcare facilities has exacerbated the burden of A. baumannii infections in many parts of Africa. This review discusses the prevalence and antibiotic-resistance pattern of the multidrug-resistant A. baumannii, and the possible ways to address or minimise its emergence in healthcare settings in Africa.

Molecular epidemiology and antimicrobial susceptibility of Pseudomonas spp. and Acinetobacter spp. from clinical samples at Jimma medical center, Ethiopia

Introduction

Pseudomonas aeruginosa (P. aeruginosa) and Acinetobacter baumannii (A. baumannii) can cause difficult-to-treat infections. We characterized molecular epidemiology of ceftazidime-resistant P. aeruginosa and carbapenem-resistant A. baumannii at a tertiary hospital in Ethiopia.

Materials and methods

Non-fermenting gram-negative bacilli (n = 80) isolated from admitted patients were subjected for species identification by MALDI-TOF. Pseudomonas species resistant to ceftazidime or meropenem, and Acinetobacter species resistant to meropenem, or imipenem were selected for whole genome sequencing. DNA extracted with EZ1 Advanced XL instrument (Qiagen, Hilden, Germany) was sequenced on Illumina (HiSeq2500) using libraries prepared by NEXTRA-kits (Illumina). Raw reads were assembled using SPAdes 3.13.0, and assembled genomes were used to query databases for resistome profile and sequence types.

Result

Among Pseudomonas species isolated, 31.7% (13/41), and 7.3% (3/41) were non-susceptible to ceftazidime, and meropenem, respectively. Carbapenem-resistance was 56.4% (22/39) among Acinetobacter species. Moreover, 92% (12/13) of Pseudomonas species non-susceptible to ceftazidime and/or meropenem, and 89.4% (17/19) of Acinetobacter species encoded multiple resistance genes for at least three classes of antimicrobials. The prevalent β - lactamase genes were bla_OXA–486 (53.8%, 7/13), bla_CTX–M–15 (23.0%, 3/13) among Pseudomonas, and bla_GES–11 (57.8%, 11/19) among Acinetobacter. The bla_OXA–51-like β - lactamase, bla_OXA–69 (63.1%, 12/19) was the most prevalent carbapenemase gene among Acinetobacter isolates. Single isolates from both P. aeruginosa, and A. baumannii were detected with the bla_NDM–1. Sequence type (ST)1 A. baumannii and ST274 P. aeruginosa were the prevalent sequence types. A cgMLST analysis of the ST1 A. baumannii isolates showed that they were closely related and belonged to the international clonal complex one (ICC1). Similarly, ST274 P. aeruginosa isolates were clonally related.

Conclusion

The prevalence of MDR isolates of Pseudomonas and Acinetobacter spp. was high. A. baumannii isolates were clonally spreading in the admission wards at the hospital. Emergence of bla_NDM–1 in the intensive care, and surgical wards of the hospital is a severe threat that requires urgent intervention.

Infections Due to Acinetobacter baumannii-calcoaceticus Complex: Escalation of Antimicrobial Resistance and Evolving Treatment Options

Bacteria within the genus Acinetobacter (principally A. baumannii-calcoaceticus complex [ABC]) are gram-negative coccobacilli that most often cause infections in nosocomial settings. Community-acquired infections are rare, but may occur in patients with comorbidities, advanced age, diabetes mellitus, chronic lung or renal disease, malignancy, or impaired immunity. Most common sites of infections include blood stream, skin/soft-tissue/surgical wounds, ventilator-associated pneumonia, orthopaedic or neurosurgical procedures, and urinary tract. Acinetobacter species are intrinsically resistant to multiple antimicrobials, and have a remarkable ability to acquire new resistance determinants via plasmids, transposons, integrons, and resistance islands. Since the 1990s, antimicrobial resistance (AMR) has escalated dramatically among ABC. Global spread of multidrug-resistant (MDR)-ABC strains reflects dissemination of a few clones between hospitals, geographic regions, and continents; excessive antibiotic use amplifies this spread. Many isolates are resistant to all antimicrobials except colistimethate sodium and tetracyclines (minocycline or tigecycline); some infections are untreatable with existing antimicrobial agents. AMR poses a serious threat to effectively treat or prevent ABC infections. Strategies to curtail environmental colonization with MDR-ABC require aggressive infection-control efforts and cohorting of infected patients. Thoughtful antibiotic strategies are essential to limit the spread of MDR-ABC. Optimal therapy will likely require combination antimicrobial therapy with existing antibiotics as well as development of novel antibiotic classes.

Prevalence and molecular epidemiology of carbapenem-resistant Gram-negative bacilli and their resistance determinants in the Eastern Mediterranean Region over the last decade

Carbapenem resistance in Enterobacteriaceae, Acinetobacter baumannii and Pseudomonas aeruginosa is increasing worldwide, which has led the World Health Organization (WHO) to list these bacteria in the critical priority pathogens group. Infections by such pathogens pose a serious threat to hospitalised patients and are associated with clinical and economic consequences. What worsens the case is the weak pipeline of available antimicrobial agents to treat such infections and the absence of new drugs. The aim of this review was to shed light on all studies tackling carbapenem resistance in Enterobacteriaceae, A. baumannii and P. aeruginosa in the Eastern Mediterranean region, with indication for each country, description of studies timeline, prevalence of carbapenem resistance, and carbapenem resistance-encoding genes detected in these countries.

Carbapenemase Producing Gram-Negative Bacteria in Tunisia: History of Thirteen Years of Challenge

The wide spread of multidrug-resistant bacteria, particularly carbapenem-resistant Gram-negative bacteria (CR-GNB), constitutes a major public health threat worldwide, owing to the limited therapeutic options. This review will describe and uncover the Tunisian experience in the challenge against carbapenem resistance. Indeed, we illuminate on the dissemination of CR-GNB in different hospitals, animals, and other natural environments in this country. We resumed the different carbapenemase variants detected from various bacterial species and mapped their regional distribution, basing on Tunisian published data during a period extended from 2006, the date of its first description in Tunisia, to February 2019. We also resumed the different mobile genetic elements implicated in their dissemination. This review shows that the majority of the research reports focused in the north and the coastal cities in spite of the fact that KPC and IMP carbapenemases were uncommonly detected in our country. However, VIM, NDM-1, and OXA-48 enzymes were usually reported with the predominance of OXA-48 among Enterobacteriaceae. Furthermore, OXA-23, OXA-51, and OXA-58 carbapenemases constituted the main mechanism conferring carbapenem resistance among Acinetobacter baumannii in Tunisia. Collaborative efforts and raising awareness of the threat of antibiotic resistance are required in order to minimize the spread of multidrug-resistant bacteria.

Antibiotic Resistance Profiles, Molecular Mechanisms and Innovative Treatment Strategies of Acinetobacter baumannii

Antibiotic resistance is one of the biggest challenges for the clinical sector and industry, environment and societal development. One of the most important pathogens responsible for severe nosocomial infections is Acinetobacter baumannii, a Gram-negative bacterium from the Moraxellaceae family, due to its various resistance mechanisms, such as the β-lactamases production, efflux pumps, decreased membrane permeability and altered target site of the antibiotic. The enormous adaptive capacity of A. baumannii and the acquisition and transfer of antibiotic resistance determinants contribute to the ineffectiveness of most current therapeutic strategies, including last-line or combined antibiotic therapy. In this review, we will present an update of the antibiotic resistance profiles and underlying mechanisms in A. baumannii and the current progress in developing innovative strategies for combating multidrug-resistant A. baumannii (MDRAB) infections.

Targeting the Class A Carbapenemase GES-5 via Virtual Screening

The worldwide spread of β-lactamases able to hydrolyze last resort carbapenems contributes to the antibiotic resistance problem and menaces the successful antimicrobial treatment of clinically relevant pathogens. Class A carbapenemases include members of the KPC and GES families. While drugs against KPC-type carbapenemases have recently been approved, for GES-type enzymes, no inhibitors have yet been introduced in therapy. Thus, GES carbapenemases represent important drug targets. Here, we present an in silico screening against the most prevalent GES carbapenemase, GES-5, using a lead-like compound library of commercially available compounds. The most promising candidates were selected for in vitro validation in biochemical assays against recombinant GES-5 leading to four derivatives active as high micromolar competitive inhibitors. For the best inhibitors, the ability to inhibit KPC-2 was also evaluated. The discovered inhibitors constitute promising starting points for hit to lead optimization.

First virtual screening and experimental validation of inhibitors targeting GES-5 carbapenemase

The worldwide spread of beta-lactamases with hydrolytic activity extended to last resort carbapenems is aggravating the antibiotic resistance problem and endangers the successful antimicrobial treatment of clinically relevant pathogens. As recently highlighted by the World Health Organization, new strategies to contain antimicrobial resistance are urgently needed. Class A carbapenemases include members of the KPC, GES and SFC families. These enzymes have the ability to hydrolyse penicillins, cephalosporins and carbapenems, while also being less susceptible to available beta-lactam inhibitors, such as clavulanic acid. The KPC family is the most prevalent. It is mostly found on plasmids in Klebsiella pneumoniae, meaning that great amounts of attention, in terms of inhibitor design and structural biology, have been dedicated to it, whereas no efforts have yet been dedicated to GES-type enzymes, despite their ability to rapidly and horizontally disseminate. We herein report the first in silico screening against GES-5, which is the most dangerous GES-type beta-lactamase, using a library of 800K commercially available candidates that all share drug-like properties, such as their MW, logP, rotatable bonds and HBA/HBD atoms. The best screening results were filtered to enrich the number of different chemotypes, and then submitted to molecular docking. The 34 most promising candidates were selected for in vitro validation in biochemical assays against recombinant GES-5. Six hits acted as inhibitors, in the high micromolar range, towards GES-5 and led to the identification of the first, novel chemotypes with inhibitory activity against this clinically relevant carbapenemase.

Molecular characterization of carbapenemases of clinical Acinetobacter baumannii-calcoaceticus complex isolates from a University Hospital in Tunisia

The aim of this study was to identify the carbapenemases from clinical carbapenem-resistant Acinetobacter baumannii-calcoaceticus complex (CRABC) isolates and to assess their potential dissemination by conjugation and natural transformation. CRABC (n = 101) were collected consecutively from inpatients of the University Hospital of Monastir, Tunisia, from 2013 to 2016. Antimicrobial susceptibility was determined by the disk diffusion method and E-test. Carbapenemase-encoding genes were screened by PCR. Genotyping was performed by Pasteur MLST scheme. Isolates were resistant to all beta-lactams, fluoroquinolones and aminoglycosides while 80 and 90% were susceptible to tigecycline and colistin, respectively. Resistance and intermediate resistance to imipenem were 87 and 13%, respectively. The genes bla_OXA-24-like, bla_OXA-58-like, bla_OXA-143-like, bla_OXA-48-like, bla_VIM, bla_IMP, and bla_KPC were not found. The bla_OXA-51-like and bla_OXA-23-like genes were present in 100 and 82.17% isolates, respectively. One isolate (< 1%) carried bla_NDM-1 and bla_OXA-51-like and belonged to Sequence Type 85 (ST85). Absence of transconjugants suggests a chromosomal location of NDM-1 determinant. The bla_NDM-1 gene was inserted in a truncated form of Tn125, which may explain the absence of bla_NDM-1 carrier-transformants. To our knowledge, this is the first report of the finding of NDM-positive A. baumannii in Tunisian territory. The study shows that despite the low prevalence and potential spread of NDM-1 enzyme among CRABC, continuous regional antimicrobial resistance surveillance and improved infection control measures are required in Tunisia to prevent further dissemination.

New STs in multidrug-resistant Acinetobacter baumannii harbouring β-lactamases encoding genes isolated from Brazilian soils

AIMS

We investigated the resistance profile, presence of β-lactamases encoding genes and the clonal relationships in Acinetobacter baumannii isolated from Brazilian soils.

METHODS AND RESULTS

Soil isolates of A. baumannii were subjected to antimicrobial susceptibility testing by disk diffusion and minimum inhibitory concentration methods. Different β-lactamases encoding genes were screened by PCR and the molecular typing of these isolates was performed through the multilocus sequence typing. Non-susceptibility to different antibiotics was found, since environmental isolates were classified as multidrug-resistant. The bla_SHV gene was the most prevalent, followed by bla_GES. All sequence types (STs) found (ST1584, ST1607, ST1608, ST1609, ST1610, ST1611 and ST1612) were described for the first time in this study.

CONCLUSION

The wide variety of new alleles and new STs detected in the present study indicates a divergent population compared to studies that are carried out in the clinical environment and points to an even larger genetic diversity within the species than was anticipated.

SIGNIFICANCE AND IMPACT OF THE STUDY

A number of the environmental isolates represented multidrug-resistant strains, a phenotype that has been more commonly reported for clinical isolates of A. baumannii; the detection of several β-lactamase encoding genes in the investigated isolates is of great concern suggesting that there is a large reservoir of these resistance genes in the environment.

Complete Genome Sequencing of Acinetobacter baumannii Strain K50 Discloses the Large Conjugative Plasmid pK50a Encoding Carbapenemase OXA-23 and Extended-Spectrum β-Lactamase GES-11

Multidrug-resistant (MDR) Acinetobacter baumannii strains appeared as serious emerging nosocomial pathogens in clinical environments and especially in intensive care units (ICUs). A. baumannii strain K50, recovered from a hospitalized patient in Kuwait, exhibited resistance to carbapenems and additionally to ciprofloxacin, chloramphenicol, sulfonamides, amikacin, and gentamicin. Genome sequencing revealed that the strain possesses two plasmids, pK50a (79.6 kb) and pK50b (9.5 kb), and a 3.75-Mb chromosome. A. baumannii K50 exhibits an average nucleotide identity (ANI) of 99.98% to the previously reported Iraqi clinical isolate AA-014, even though the latter strain lacked plasmid pK50a. Strain K50 belongs to sequence type 158 (ST158) (Pasteur scheme) and ST499 (Oxford scheme). Plasmid pK50a is a member of the Aci6 (replication group 6 [RG6]) group of Acinetobacter plasmids and carries a conjugative transfer module and two antibiotic resistance gene regions. The transposon Tn2008 carries the carbapenemase gene bla_OXA-23, whereas a class 1 integron harbors the resistance genes bla_GES-11, aacA4, dfrA7, qacEΔ1, and sul1, conferring resistance to all β-lactams and reduced susceptibility to carbapenems and resistance to aminoglycosides, trimethoprim, quaternary ammonium compounds, and sulfamethoxazole, respectively. The class 1 integron is flanked by MITEs (miniature inverted-repeat transposable elements) delimiting the element at its insertion site.

Biology of Acinetobacter baumannii: Pathogenesis, Antibiotic Resistance Mechanisms, and Prospective Treatment Options

Acinetobacter baumannii is undoubtedly one of the most successful pathogens responsible for hospital-acquired nosocomial infections in the modern healthcare system. Due to the prevalence of infections and outbreaks caused by multi-drug resistant A. baumannii, few antibiotics are effective for treating infections caused by this pathogen. To overcome this problem, knowledge of the pathogenesis and antibiotic resistance mechanisms of A. baumannii is important. In this review, we summarize current studies on the virulence factors that contribute to A. baumannii pathogenesis, including porins, capsular polysaccharides, lipopolysaccharides, phospholipases, outer membrane vesicles, metal acquisition systems, and protein secretion systems. Mechanisms of antibiotic resistance of this organism, including acquirement of β-lactamases, up-regulation of multidrug efflux pumps, modification of aminoglycosides, permeability defects, and alteration of target sites, are also discussed. Lastly, novel prospective treatment options for infections caused by multi-drug resistant A. baumannii are summarized.