Outbreak of extended-spectrum beta-lactamase VEB-1-producing isolates of Acinetobacter baumannii in a French hospital

AdeIJK Pump-Specific Inhibitors Effective against Multidrug Resistant Acinetobacter baumannii

Multidrug-resistant Acinetobacter baumannii is a serious threat pathogen rapidly spreading in clinics and causing a range of complicated human infections. The major contributor to A. baumannii antibiotic resistance is the overproduction of AdeIJK and AdeABC multidrug efflux pumps of the resistance-nodulation-division (RND) superfamily of proteins. The dominant role of efflux in antibiotic resistance and the relatively high permeability of the A. baumannii outer membrane to amphiphilic compounds make this pathogen a promising target for the discovery of clinically relevant efflux pump inhibitors. In this study, we identified 4,6-diaminoquoniline analogs with inhibitory activities against A. baumannii AdeIJK efflux pump and followed up on these compounds with a focused synthetic program to improve the target specificity and to reduce cytotoxicity. We identified several candidates that potentiate antibacterial activities of antibiotics erythromycin, tetracycline, and novobiocin not only in the laboratory antibiotic susceptible strain A. baumannii ATCC17978 but also in multidrug-resistant clinical isolates AB5075 and AYE. The best analogs potentiated the activities of antibiotics in low micromolar concentrations, did not have antibacterial activities on their own, inhibited AdeIJK-mediated efflux of its fluorescent substrate ethidium ion, and had low cytotoxicity in A549 human lung epithelial cells.

Genomic plasticity and adaptive capacity of the quaternary alkyl-ammonium compound and copper tolerant Acinetobacter bohemicus strain QAC-21b isolated from pig manure

Here, we present the genomic characterization of an Acinetobacter bohemicus strain QAC-21b which was isolated in the presence of a quaternary alky-ammonium compound (QAAC) from manure of a conventional German pig farm. The genetic determinants for QAAC, heavy metal and antibiotic resistances are reported based of the whole genome shotgun sequence and physiological growth tests. A. bohemicus QAC-21b grew in a species typical manner well at environmental temperatures but not at 37 °C. The strain showed tolerance to QAACs and copper but was susceptible to antibiotics relevant for Acinetobacter treatments. The genome of QAC-21b contained several Acinetobacter typical QAAC and heavy metal transporting efflux pumps coding genes, but no key genes for acquired antimicrobial resistances. The high genomic content of transferable genetic elements indicates that this bacterium can be involved in the transmission of antimicrobial resistances, if it is released with manure as organic fertilizer on agricultural fields. The genetic content of the strain was compared to that of two other A. bohemicus strains, the type strain ANC 3994^T, isolated from forest soil, and KCTC 42081, originally described as A. pakistanensis, a metal resistant strain isolated from a wastewater treatment pond. In contrast to the forest soil strain, both strains from anthropogenically impacted sources showed genetic features indicating their evolutionary adaptation to the anthropogenically impacted environments. Strain QAC-21b will be used as model strain to study the transmission of antimicrobial resistance to environmentally adapted Acinetobacter in agricultural environments receiving high content of pollutants with organic fertilizers from livestock husbandry.

Genotypic Patterns of Multidrug-Resistant Acinetobacter baumannii: A Systematic Review

Acinetobacter baumannii (A. baumannii) is one of the most common bacteria in nosocomial infections. Inappropriate usage of antibiotics has led to expanding emergence resistance to A. baumannii as a multidrug-resistant (MDR) strain. Empirical antibiotic therapy is necessary to evaluate the resistant gene pattern of MDR A. baumannii. For this purpose, the present study evaluated the resistance genes pattern of MDR A. baumannii collected from hospitalized patients using a genotypic diagnostic technique. To find evidence related to the study objectives, databases were searched such as Google Scholar, Web of Science, Science Direct, PubMed, and Scopus from 2000 to 2022, with specified keywords in the title and text of the articles. Articles were included based on inclusion and exclusion criteria. The mentioned database displayed 284 articles. After screening, 65 eligible articles were included. The results showed that various b-lactamases genes, aminoglycoside-modifying enzymes (AMEs) genes, and pump-expressing genes are resistance gene patterns in MDR A. baumannii isolates. MDR A. baumannii has significantly become resistant to b-lactams, carbapenems, and aminoglycosides.

Na+ homeostasis in Acinetobacter baumannii is facilitated via the activity of the Mrp antiporter

The human opportunistic pathogen Acinetobacter baumannii is a global threat to healthcare institutions worldwide, since it developed very efficient strategies to evade host defense and to adapt to the different environmental conditions of the host. This worked focused on the importance of Na⁺ homeostasis in A. baumannii with regards to pathobiological aspects. In silico studies revealed a homologue of a multicomponent Na⁺ /H⁺ antiporter system. Inactivation of the Mrp antiporter through deletion of the first gene (mrpA') resulted in a mutant that was sensitive to increasing pH values. Furthermore, the strain was highly sensitive to increasing Na⁺ and Li⁺ concentrations. Increasing Na⁺ sensitivity is thought to be responsible for growth impairment in human fluids. Furthermore, deletion of mrpA' is associated with energetic defects, inhibition of motility and survival under anoxic and dry conditions.

Genomic analysis of CTX-M-115 and OXA-23/-72 co-producing Acinetobacter baumannii, and their potential to spread resistance genes by natural transformation

OBJECTIVES

To characterize Acinetobacter baumannii strains co-producing the ESBL CTX-M-115 and carbapenem-hydrolysing class D β-lactamases (CHDLs), and to assess the potential diffusion of their resistance genes by horizontal transfer.

METHODS

Nineteen CTX-M-115/CHDL-positive A. baumannii were collected between 2015 and 2019 from patients hospitalized in France. Their whole-genome sequences were determined on Illumina and Oxford Nanopore platforms and were compared through core-genome MLST (cgMLST) and SNP analyses. Transferability of resistance genes was investigated by natural transformation assays.

RESULTS

Eighteen strains were found to harbour CHDL OXA-72, and another one CHDL OXA-23, in addition to CTX-M-115, narrow-spectrum β-lactamases and aminoglycoside resistance determinants including ArmA. cgMLST typing, as well as Oxford Scheme ST and K locus typing, confirmed that 17 out of the 18 CTX-M-115/OXA-72 isolates belonged to new subclades within clonal complex 78 (CC78). The chromosomal region carrying the blaCTX-M-115 gene appeared to vary greatly both in gene content and in length (from 20 to 79 kb) among the strains, likely because of IS26-mediated DNA rearrangements. The blaOXA-72 gene was localized on closely related plasmids showing structural variations that occurred between pdif sites. Transfer of all the β-lactamase genes, as well as aminoglycoside resistance determinants to a drug-susceptible A. baumannii recipient, was easily obtained in vitro by natural transformation.

CONCLUSIONS

This work highlights the propensity of CC78 isolates to collect multiple antibiotic resistance genes, to rearrange and to pass them to other A. baumannii strains via natural transformation. This process, along with mobile genetic elements, likely contributes to the considerable genomic plasticity of clinical strains, and to the diversity of molecular mechanisms sustaining their multidrug resistance.

Detection of Extended-Spectrum β-Lactamases among Acinetobacter Baumannii Isolated from Hospitals of Qazvin, Iran

Background

Acinetobacter baumannii is a major contributor to nosocomial infections. Extended-spectrum β-lactamase (ESBL)-producing A. baumannii is spreading worldwide. We aimed to determine the frequency of ESBL-encoding genes in clinical isolates of A. baumannii and to access their clonal relationship by repetitive extragenic palindromic-PCR (rep-PCR).

Methods

In this descriptive cross-sectional study, 203 isolates of A. baumannii were collected from Qazvin hospitals. The Identification of isolates was performed by standard laboratory methods. To verify ESBL production, all isolates were screened by disk agar diffusion and confirmed by the combined disk method. Subsequently, ESBL-encoding genes were detected by PCR and sequencing. Possible clonal association of ESBL-producing isolates was evaluated using rep-PCR.

Results

Two hundred (98.5%) isolates showed reduced susceptibility to one of the antibiotics used in the ESBL screening test, of which 127 isolates (62.6%) produced ESBL. PCR results showed bla_OXA-1 (20.5%) was the most prevalent gene followed by bla_TEM-1 (20%), bla_GES-1 (15.7%), bla_CTX-M-15 (7.9%), and bla_PER-1 (1.6%). Rep-PCR results revealed that ESBL-producing isolates belonged to clones A (85%), B (13.4%), and C (1.6%).

Conclusion

Our study showed the significant presence of bla_OXA-1, bla_TEM-1, bla_GES-1, bla_CTX-M-15, and bla_PER-1 genes in ESBL-producing A. baumannii isolates in the studied hospitals. This is the first report on the emergence of bla_OXA-1 gene in these isolates in Iran. The use of comprehensive antimicrobial treatment guidelines based on laboratory data and appropriate infection control interventions are essential.

Molecular and epidemiological investigation of a colistin-resistant OXA-23-/NDM-1-producing Acinetobacter baumannii outbreak in the Southwest Indian Ocean Area

Dual resistance to colistin and carbapenems is a milestone reached by certain extensively-drug resistant (XDR) Gram-negative bacteria. This study describes the first outbreak of XDR colistin- and carbapenem-resistant OXA-23-/NDM-1-producing Acinetobacter baumannii (CCRAB) in the European overseas territory of Reunion Island (France, Indian Ocean). Between April 2019 and June 2020, 13 patients admitted to the University Hospital of Reunion Island were involved in the outbreak, of whom eight were infected and six died. The first case was traced to a medical evacuation from Mayotte Island (Comoros archipelago). An epidemiological link could be established for 11 patients. All of the collected CCRAB isolates showed the same resistance profile and co-produced intrinsic β-lactamases OXA-69 and ADC-191, together with acquired carbapenem-hydrolysing β-lactamases OXA-23 and NDM-1. A mutation likely involved in colistin resistance was detected in the two-component system PmrAB (D82N in PmrA). All of the isolates were found to belong to ST^Pas1/ST^Ox231 clonal complex and were phylogenetically indistinguishable. Their further characterization by whole-genome sequence analyses (whole-genome multi-locus sequence typing, single nucleotide polymorphisms) provided hints about the transmission pathways. This study pleads for strict application of control and prevention measures in institutions where the risk of imported XDR bacteria is high.

Extended-spectrum β-lactamases: an update on their characteristics, epidemiology and detection

Extended-spectrum β-lactamase (ESBL)-producing Gram-negative pathogens are a major cause of resistance to expanded-spectrum β-lactam antibiotics. Since their discovery in the early 1980s, they have spread worldwide and an are now endemic in Enterobacterales isolated from both hospital-associated and community-acquired infections. As a result, they are a global public health concern. In the past, TEM- and SHV-type ESBLs were the predominant families of ESBLs. Today CTX-M-type enzymes are the most commonly found ESBL type with the CTX-M-15 variant dominating worldwide, followed in prevalence by CTX-M-14, and CTX-M-27 is emerging in certain parts of the world. The genes encoding ESBLs are often found on plasmids and harboured within transposons or insertion sequences, which has enabled their spread. In addition, the population of ESBL-producing Escherichia coli is dominated globally by a highly virulent and successful clone belonging to ST131. Today, there are many diagnostic tools available to the clinical microbiology laboratory and include both phenotypic and genotypic tests to detect β-lactamases. Unfortunately, when ESBLs are not identified in a timely manner, appropriate antimicrobial therapy is frequently delayed, resulting in poor clinical outcomes. Several analyses of clinical trials have shown mixed results with regards to whether a carbapenem must be used to treat serious infections caused by ESBLs or whether some of the older β-lactam-β-lactamase combinations such as piperacillin/tazobactam are appropriate. Some of the newer combinations such as ceftazidime/avibactam have demonstrated efficacy in patients. ESBL-producing Gram-negative pathogens will continue to be major contributor to antimicrobial resistance worldwide. It is essential that we remain vigilant about identifying them both in patient isolates and through surveillance studies.

Acinetobacter baumannii Antibiotic Resistance Mechanisms

Acinetobacter baumannii is a Gram-negative ESKAPE microorganism that poses a threat to public health by causing severe and invasive (mostly nosocomial) infections linked with high mortality rates. During the last years, this pathogen displayed multidrug resistance (MDR), mainly due to extensive antibiotic abuse and poor stewardship. MDR isolates are associated with medical history of long hospitalization stays, presence of catheters, and mechanical ventilation, while immunocompromised and severely ill hosts predispose to invasive infections. Next-generation sequencing techniques have revolutionized diagnosis of severe A. baumannii infections, contributing to timely diagnosis and personalized therapeutic regimens according to the identification of the respective resistance genes. The aim of this review is to describe in detail all current knowledge on the genetic background of A. baumannii resistance mechanisms in humans as regards beta-lactams (penicillins, cephalosporins, carbapenems, monobactams, and beta-lactamase inhibitors), aminoglycosides, tetracyclines, fluoroquinolones, macrolides, lincosamides, streptogramin antibiotics, polymyxins, and others (amphenicols, oxazolidinones, rifamycins, fosfomycin, diaminopyrimidines, sulfonamides, glycopeptide, and lipopeptide antibiotics). Mechanisms of antimicrobial resistance refer mainly to regulation of antibiotic transportation through bacterial membranes, alteration of the antibiotic target site, and enzymatic modifications resulting in antibiotic neutralization. Virulence factors that may affect antibiotic susceptibility profiles and confer drug resistance are also being discussed. Reports from cases of A. baumannii coinfection with SARS-CoV-2 during the COVID-19 pandemic in terms of resistance profiles and MDR genes have been investigated.

Antibacterial effect of carbon nanotube containing chemical compounds on drug-resistant isolates of Acinetobacter baumannii

Background and Objectives:

Acinetobacter baumannii is recognized as an important pathogen responsible for serious infections causing episodes of hospital infection. Carbon nanotubes (CNTs) have recently emerged as superior materials against antibiotic-resistant bacteria. In this study, a new chemical compound was designed in order to combat A. baumannii infections. Subsequently, the effect of this novel carbon nanotube coated with an antibacterial compound on Extensively Drug-Resistant (XDR), Multidrug-Resistant (MDR) and Pan-Drug-Resistance (PDR) strains of A. baumannii was investigated.

Materials and Methods:

A total of 122 clinical isolates of A. baumannii were cultured from burn patients and their susceptibility to antibiotics were checked using disk diffusion method and Minimum inhibitory concentration. Antimicrobial effects of the coated carbon nanotube were evaluated on XDR, MDR and PDR isolates of A. baumannii. Cell viability was determined using tetrazolium reduction assay (MTT) on human fibroblast cell line (HDFa). Wound healing processes were assessed by quantitative polymerase chain reaction.

Results:

Of the 50 A. baumannii isolates, 38 (76%) were found to be MDR and 12 (24%) were XDR. No PDR strains were detected. Results indicated that the carbon nanotube combined with mercury had antibacterial effect against different A. baumannii species and it also was able to increase the expression of epidermal growth factor, platelet-derived growth factor and vascular endothelial growth factor A mRNA levels which are involved in wound healing.

Conclusion:

The engineered carbon nanotube compound can potentially be used for treatment of burn related infections. This can potentially give clinicians a new tool for treating A. baumannii infections.

Inactivation of AdeABC and AdeIJK efflux pumps elicits specific nonoverlapping transcriptional and phenotypic responses in Acinetobacter baumannii

Multidrug resistant (MDR) strains of Acinetobacter baumannii present a serious clinical challenge. The development of antibiotic resistance in this species is enabled by efflux pumps of the Resistance-Nodulation-Division (RND) superfamily of proteins creating an efficient permeability barrier for antibiotics. At least three RND pumps, AdeABC, AdeIJK, and AdeFGH are encoded in the A. baumannii genome and are reported to contribute to antibiotic resistance in clinical isolates. In this study, we analyzed the contributions of AdeABC and AdeIJK in antibiotic resistance and growth physiology of the two MDR strains, AYE and AB5075. We found that not only the two pumps have nonoverlapping substrate specificities, their inactivation leads to specific nonoverlapping changes in gene expression as determined by RNA sequencing and confirmed by gene knockouts and growth phenotypes. Our results suggest that inactivation of AdeIJK elicits broader changes in the abundances of mRNAs and this response is modified in the absence of AdeB. In contrast, inactivation of AdeB leads to a focused cellular response, which is not sensitive to the activity of AdeIJK. We identified additional efflux pumps and transcriptional regulators that contribute to MDR phenotype of clinical A. baumannii isolates.

Scarless Removal of Large Resistance Island AbaR Results in Antibiotic Susceptibility and Increased Natural Transformability in Acinetobacter baumannii

With a great diversity in gene composition, including multiple putative antibiotic resistance genes, AbaR islands are potential contributors to multidrug resistance in Acinetobacter baumannii. However, the effective contribution of AbaR to antibiotic resistance and bacterial physiology remains elusive. To address this, we sought to accurately remove AbaR islands and restore the integrity of their insertion site. To this end, we devised a versatile scarless genome editing strategy.

With a great diversity in gene composition, including multiple putative antibiotic resistance genes, AbaR islands are potential contributors to multidrug resistance in Acinetobacter baumannii. However, the effective contribution of AbaR to antibiotic resistance and bacterial physiology remains elusive. To address this, we sought to accurately remove AbaR islands and restore the integrity of their insertion site. To this end, we devised a versatile scarless genome editing strategy. We performed this genetic modification in two recent A. baumannii clinical strains: the strain AB5075 and the nosocomial strain AYE, which carry AbaR11 and AbaR1 islands of 19.7 kbp and 86.2 kbp, respectively. Antibiotic susceptibilities were then compared between the parental strains and their AbaR-cured derivatives. As anticipated by the predicted function of the open reading frame (ORF) of this island, the antibiotic resistance profiles were identical between the wild type and the AbaR11-cured AB5075 strains. In contrast, AbaR1 carries 25 ORFs, with predicted resistance to several classes of antibiotics, and the AYE AbaR1-cured derivative showed restored susceptibility to multiple classes of antibiotics. Moreover, curing of AbaRs restored high levels of natural transformability. Indeed, most AbaR islands are inserted into the comM gene involved in natural transformation. Our data indicate that AbaR insertion effectively inactivates comM and that the restored comM is functional. Curing of AbaR consistently resulted in highly transformable and therefore easily genetically tractable strains. Emendation of AbaR provides insight into the functional consequences of AbaR acquisition.

Carbapenemase -producing Pseudomonas aeruginosa isolates from Turkey: first report of P. aeruginosa high-risk clones with VIM-5- and IMP-7-type carbapenemases in a tertiary hospital

We investigated the presence of carbapenemases in carbapenem-resistant Pseudomonas aeruginosa isolates, which were collected over a 14-month period in a Turkish hospital, with in-depth molecular characterization of carbapenemase-producing isolates. Among 45 study isolates, 2 isolates were identified as carbapenemase producers by both Carba NP and Carbapenem Inactivation Method tests, and only 1 of them gave a positive result in polymerase chain reaction tests for a carbapenemase gene (bla_VIM). Whole genome sequencing of the 2 isolates revealed the presence of bla_VIM-5 gene in an ST308 isolate, while the other one expressed IMP-7 in an ST357 isolate; both STs are considered high-risk clones. The 2 carbapenemase-producing isolates were multidrug resistant, as they harbored other resistance determinants, including a variant of the recently described plasmid-encoded fluoroquinolone resistance determinant crpP gene, crpP-2. We report for the first time P. aeruginosa high-risk clones carrying VIM-5- and IMP-7-type carbapenemases with multiple resistance determinants in Turkey.

The Acinetobacter trimeric autotransporter adhesin Ata controls key virulence traits of Acinetobacter baumannii

Acinetobacter baumannii is a Gram-negative pathogen that causes a multitude of nosocomial infections. The Acinetobacter trimeric autotransporter adhesin (Ata) belongs to the superfamily of trimeric autotransporter adhesins which are important virulence factors in many Gram-negative species. Phylogenetic profiling revealed that ata is present in 78% of all sequenced A. baumannii isolates but only in 2% of the closely related species A. calcoaceticus and A. pittii. Employing a markerless ata deletion mutant of A. baumannii ATCC 19606 we show that adhesion to and invasion into human endothelial and epithelial cells depend on Ata. Infection of primary human umbilical cord vein endothelial cells (HUVECs) with A. baumannii led to the secretion of interleukin (IL)-6 and IL-8 in a time- and Ata-dependent manner. Furthermore, infection of HUVECs by WT A. baumannii was associated with higher rates of apoptosis via activation of caspases-3 and caspase-7, but not necrosis, in comparison to ∆ata. Ata deletion mutants were furthermore attenuated in their ability to kill larvae of Galleria mellonella and to survive in larvae when injected at sublethal doses. This indicates that Ata is an important multifunctional virulence factor in A. baumannii that mediates adhesion and invasion, induces apoptosis and contributes to pathogenicity in vivo.

New Multidrug Efflux Inhibitors for Gram-Negative Bacteria

Active efflux of antibiotics preventing their accumulation to toxic intracellular concentrations contributes to clinically relevant multidrug resistance. Inhibition of active efflux potentiates antibiotic activity, indicating that efflux inhibitors could be used in combination with antibiotics to reverse drug resistance. Expression of ramA by Salmonella enterica serovar Typhimurium increases in response to efflux inhibition, irrespective of the mode of inhibition. We hypothesized that measuring ramA promoter activity could act as a reporter of efflux inhibition. A rapid, inexpensive, and high-throughput green fluorescent protein (GFP) screen to identify efflux inhibitors was developed, validated, and implemented. Two chemical compound libraries were screened for compounds that increased GFP production. Fifty of the compounds in the 1,200-compound Prestwick chemical library were identified as potential efflux inhibitors, including the previously characterized efflux inhibitors mefloquine and thioridazine. There were 107 hits from a library of 47,168 proprietary compounds from L. Hoffmann La Roche; 45 were confirmed hits, and a dose response was determined. Dye efflux and accumulation assays showed that 40 Roche and three Prestwick chemical library compounds were efflux inhibitors. Most compounds had specific efflux-inhibitor-antibiotic combinations and/or species-specific synergy in antibiotic disc diffusion and checkerboard assays performed with Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and Salmonella Typhimurium. These data indicate that both narrow-spectrum and broad-spectrum combinations of efflux inhibitors with antibiotics can be found. Eleven novel efflux inhibitor compounds potentiated antibiotic activities against at least one species of Gram-negative bacteria, and data revealing an E. coli mutant with loss of AcrB function suggested that these are AcrB inhibitors.IMPORTANCE Multidrug-resistant Gram-negative bacteria pose a serious threat to human and animal health. Molecules that inhibit multidrug efflux offer an alternative approach to resolving the challenges caused by antibiotic resistance, by potentiating the activity of old, licensed, and new antibiotics. We have developed, validated, and implemented a high-throughput screen and used it to identify efflux inhibitors from two compound libraries selected for their high chemical and pharmacological diversity. We found that the new high-throughput screen is a valuable tool to identify efflux inhibitors, as evidenced by the 43 new efflux inhibitors described in this study.

[Factors associated with the quality of sterilization of surgical drapes at the National Hospital University Hubert Koutoukou Maga of Cotonou]

Introduction

La stérilisation des linges opératoires joue un rôle important dans la prévention des infections associées aux soins. Au Centre National Hospitalier Universitaire Hubert Koutoukou MAGA (CNHU-HKM), le processus de stérilisation des linges rencontre des problèmes. La présente étude avait pour objectif d’étudier les facteurs associés à la qualité de stérilisation du linge opératoire au CNHU-HKM.

Méthodes

Il s’agissait d’une étude transversale, descriptive et analytique qui avait porté sur 20 linges opératoires stérilisés, 41 agents impliqués dans la gestion des linges et 55 membres de l’équipe chirurgicale. La méthode avait été probabiliste pour les linges opératoires stérilisés et non probabiliste pour les autres. Le test de Khi carré de Pearson et la régression logistique ont été utilisés pour rechercher l’association avec un seuil significatif et un p <0,05.

Résultats

Quatre-vingt-six virgule quarante-six pourcent des sujets étaient de sexe masculin avec un âge médian de 42 ans. La qualité du processus de stérilisation du linge opératoire n’était pas bonne dans les deux services en charge de traiter les linges. Le contrôle bactériologique avait montré que sur les 20 linges opératoires stérilisés, 9 portaient Acinetobacter spp. un germe d’infection nosocomiale multi résistant. L’analyse multivariée avait montré que l’expérience professionnelle (p=0,015) et le contrôle de qualité dans le processus de traitement (p=0,034) sont statistiquement associés à la qualité de la stérilisation.

Conclusion

Acinetobacter spp. trouvé sur des linges stérilisés montre que la stérilisation des linges au CNHU-HKM n’est pas de qualité. Un renforcement des compétences des prestataires est nécessaire pour l’amélioration de la qualité du processus de stérilisation.

Prevalence of β-lactamase genes, class 1 integrons, major virulence factors and clonal relationships of multidrug-resistant Pseudomonas aeruginosa isolated from hospitalized patients in southeast of Iran

Objective(s):

Pseudomonas aeruginosa is one of the most important nosocomial pathogens causing a high rate of mortality among hospitalized patients. Herein, we report the prevalence of antibiotic resistance genes, class 1 integrons, major virulence genes and clonal relationship among multidrug- resistant (MDR) P. aeruginosa, isolated from four referral hospitals in the southeast of Iran.

Materials and Methods:

In this study, 208 isolates of P. aeruginosa were collected from four referral hospitals in southeast of Iran. Disk diffusion method was used to determine susceptibility to 13 antibacterial agents. AmpC was detected by phenotypic method and β-lactamase genes, virulence genes and class 1 integrons were detected by PCR. Clonal relationship of the isolates was determined by RAPD-PCR.

Results:

All the isolates were susceptible to polymyxin-B and colistin. Overall, 40.4% of the isolates were MDR, among which resistance to third generation cephalosporins, aminoglycosides, and carbapenems was 47.5%, 32.3% and 40%, respectively. None of the isolates was positive for bla_NDM-1 genes, while 84.5% and 4.8% were positive for the bla_IMP-1 and bla_VIM, metallo-β-lactamase genes, respectively. Incidence of class 1 integrons was 95% and AmpC was detected in 33% of the isolates. Prevalence of exoA, exoS, exoU, pilB and nan1 were 98.8%, 44%, 26%, 8.3% and 33.3%, respectively. RAPD profiles identified four large clusters consisting of 77 isolates, and two small clusters and three singletons.

Conclusion: :

The rate of MDR P. aeruginosa isolates was high in different hospitals in this region. High genetic similarity among MDR isolates suggests cross-acquisition of infection in the region.

Burden of Multidrug-Resistant Acinetobacter baumannii Infection in Hospitalized Patients in a Tertiary Care Hospital of Nepal

Introduction

Acinetobacter baumannii has emerged as a significant multidrug-resistant (MDR) nosocomial pathogen worldwide and is responsible for various healthcare-associated infections. The MDR strains have been reported increasingly during the last decades in hospitalized patients. They have developed resistance to most of the available antibiotics and are known to produce various acquired β-lactamases. The β-lactamase producing strains have a potential for rapid dissemination in hospital settings, as it is often plasmid-mediated. The Infectious Diseases Society of America (ISDA) stated A. baumannii as one of the “red alert” pathogens that greatly threatens the utility of our current antibacterial armamentarium. The study attempted to investigate the spectrum and antimicrobial resistance among MDR A. baumannii and their potential implications in hospitalized patients in a tertiary care hospital of Nepal.

Methods

This study was conducted at Tribhuvan University Teaching Hospital (TUTH), Nepal from January 2017 to December 2017. A total of 177 A. baumannii isolated from hospitalized patients were included in the study. The AST was performed by disc diffusion method. The MDR strains were identified by the criteria of Magiorakos et al, ESBL production by CLSI guidelines, and AmpC β-lactamase production by the AmpC disc test. MBL and KPC production were detected as per the method of Tsakris et al.

Results

Out of 177 A. baumannii, 91.0% were MDR isolates. Among the MDR isolates, the majority were isolated from respiratory tract specimens and were isolated from ICU patients. Most of the MDR isolates were resistant to all first-line antibiotics and all were completely sensitive to only polymyxin B and colistin sulfate. MBL (67.7%) was the common β-lactamase production among MDR isolates.

Conclusion

Acinetobacter baumannii can cause a vast variety of infections in hospitalized patients. The highly resistant MDR strains are common in tertiary care hospitals. This bacteria lead to high morbidity and mortality as we are left with the only option of treating them by potentially toxic antibiotics like colistin sulfate and polymyxin B. Detection of drug resistance and rational use of antibiotics play a crucial role in the fight against this MDR pathogen.

An insight into the emergence of Acinetobacter baumannii as an oro-dental pathogen and its drug resistance gene profile - An in silico approach

Background

Acinetobacter baumannii, a potential nosocomial pathogen has stealthily gained entry into the oral cavity. Their association with other pathogens like Pseudomonas aeruginosa in chronic and aggressive periodontitis cases is well documented. The magnitude of problem caused by A . baumannii could be attributed to resistance genes acquired by the organism. Since the microbiome of oral cavity is heterogeneous and complex, the transfer of genes from multidrug resistant A . baumannii may be a serious threat in infection control and management. In view of this fact, the present study aims to categorize and characterize drug resistant genes present in each of the 19 genomes of Acinetobacter Sp. selected for the study.

Methods

About 19 genome sequences of Acinetobacter spp. with the predominance of different strains of A . baumannii was genotyped using in silico restriction digestion and pulse field gel electrophoresis (PFGE). Further, the prevalence of common drug resistant genes in the genome of various Acinetobacter spp. was recorded using in silico PCR analysis.

Results

Based on the PFGE pattern, phylogenetic tree was constructed and the genomes were clustered into 6 genotypes. Genotype 4 (n = 8; 42.10%) and 5 (n = 6; 31.57%) were predominant, followed by genotypes 2 (n = 2; 10.52%), 1, 3 and 6 (n = 1; 5.26%). Three species were excluded from the list since they were negative for most of the drug resistant genes tested. Prevalence of drug resistant genes in each of the 16 genomes analysed found oxa-51, ISAba 1 and ADC 1 to be the major genes found in A . baumannii. Acinetobacter spp. belonging to genotypes 4 and 5 were found to harbour 6-10 and 2-8 potential drug resistant genes respectively.

Conclusion

The present study showed cluster of multi-drug resistant genes in genomes analysed, thus, warranting the need for antibiotic surveillance, alternate therapeutic measures and development of novel antimicrobials. An extensive study on the genes conferring drug resistance in this pathogen will open new avenues for battling the entry and spread of this pathogen in vulnerable patient groups.

Co-production of AmpC and extended spectrum beta-lactamases in cephalosporin-resistant Acinetobacter baumannii in Egypt

Acinetobacter baumannii is an opportunistic pathogen that has been held responsible for a lot of infections worldwide. Infections caused by this pathogen are difficult to control because of the widespread of antimicrobial resistance mechanisms. The aim of the present study is to assess the prevalence of extended spectrum β-lactamases (ESBLs) and AmpC β-lactamases among isolates of A. baumannii collected from different clinical sources in Mansoura University Hospitals, Egypt. Antimicrobial susceptibility testing has demonstrated elevated resistance level to β-lactams, quinolones and aminoglycosides. All isolates were sensitive to colistin and polymyxin B. ESBL activity was detected in 86% of the isolates. Among the tested ESBL encoding genes, bla_TEM gene was the most prevalent gene as it was detected in 52% of the isolates. While bla_PER, bla_SHV and bla_VEB were detected in 12%, 4%, and 2%, respectively. AmpC activity and bla_ADC gene were detected in 90% of the tested isolates. Insertion sequence ISAba1 was located 9 bp upstream of bla_ADC gene in 88.9% of the ADC-expressing isolates providing a potent promoter activity for its expression. To our knowledge this is the first report of loss of intrinsic ADC activity, in 10% of the tested isolates, as a result of insertional inactivation by an element belonging to IS5 family transposase. Co-expression of both ESBLs and AmpC β-lactamases was detected in 78% of the isolates. The study demonstrates high prevalence of resistance to β-lactam antibiotics through ESBLs and AmpC β-lactamases production among A. baumannii clinical isolates. Prevalence of β-lactamases should be detected routinely and reported in hospitals to avoid inappropriate use of antibiotics and therapeutic failure.

Molecular mechanisms of antimicrobial resistance in Acinetobacter baumannii, with a special focus on its epidemiology in Lebanon

Acinetobacter baumannii is an opportunistic bacterium involved in several types of infection with high mortality and morbidity, especially in intensive care units. Treatment of these infections remains a challenge due to the worldwide emergence of broad-spectrum resistance to many antibiotics. Following the implementation of molecular techniques to study A. baumannii outbreaks, it has been shown that they are mainly caused by specific clones such as international clones I, II and III. The present work aims to review the available data on the mechanisms underlying antimicrobial resistance in A. baumannii, with a special focus on the molecular epidemiology of this species in Lebanon.

Antibiofilm activity of an EDTA-containing nanoemulsion on multidrug-resistant Acinetobacter baumannii

Acinetobacter baumannii have evolved as an exceedingly troublesome pathogenic microorganisms and prevention and controlling this pathogen is considered to be a public health problem. Nanoemulsions (NE) are a distinctive type of decontaminator produced by integration of immiscible oil phase with aqueous phase under extreme shear forces. The effectiveness of NEs and their components was determined against four stains of A. baumannii by MBC, adherence assay, biofilm assay and SEM studies. NE dilutions ranging from 125 to 225 reduced adhesion by from 61.8 to 99.9% in NE-treated groups (p<.05) as determined by MBC. Four-day-old A. baumannii biofilms were treated with NE; LIVE/DEAD staining showed dead cell intensity of 56.2-92.0% in NE-treated groups. After NE treatment and observation by SEM, cell surfaces appeared to be remarkably disintegrated. Irregular boundaries were observed and margins of cell walls were unclear. The anti-adherence, anti-biofilm and morphological disruption effects of NE suggest that this material could be useful for the development of promising antimicrobial agents.

New eight genes identified at the clinical multidrug-resistant Acinetobacter baumannii DMS06669 strain in a Vietnam hospital

Background

Acinetobacter baumannii is an important nosocomial pathogen that can develop multidrug resistance. In this study, we characterized the genome of the A. baumannii strain DMS06669 (isolated from the sputum of a male patient with hospital-acquired pneumonia) and focused on identification of genes relevant to antibiotic resistance.

Methods

Whole genome analysis of A. baumannii DMS06669 from hospital-acquired pneumonia patients included de novo assembly; gene prediction; functional annotation to public databases; phylogenetics tree construction and antibiotics genes identification.

Results

After sequencing the A. baumannii DMS06669 genome and performing quality control, de novo genome assembly was carried out, producing 24 scaffolds. Public databases were used for gene prediction and functional annotation to construct a phylogenetic tree of the DMS06669 strain with 21 other A. baumannii strains. A total of 18 possible antibiotic resistance genes, conferring resistance to eight distinct classes of antibiotics, were identified. Eight of these genes have not previously been reported to occur in A. baumannii.

Conclusions

Our results provide important information regarding mechanisms that may contribute to antibiotic resistance in the DMS06669 strain, and have implications for treatment of patients infected with A. baumannii.

Electronic supplementary material

The online version of this article (10.1186/s12941-017-0250-9) contains supplementary material, which is available to authorized users.

Towards the complete proteinaceous regulome of Acinetobacter baumannii

The emergence of Acinetobacter baumannii strains, with broad multidrug-resistance phenotypes and novel virulence factors unique to hypervirulent strains, presents a major threat to human health worldwide. Although a number of studies have described virulence-affecting entities for this organism, very few have identified regulatory elements controlling their expression. Previously, our group has documented the global identification and curation of regulatory RNAs in A. baumannii. As such, in the present study, we detail an extension of this work, the performance of an extensive bioinformatic analysis to identify regulatory proteins in the recently annotated genome of the highly virulent AB5075 strain. In so doing, 243 transcription factors, 14 two-component systems (TCSs), 2 orphan response regulators, 1 hybrid TCS and 5 σ factors were found. A comparison of these elements between AB5075 and other clinical isolates, as well as a laboratory strain, led to the identification of several conserved regulatory elements, whilst at the same time uncovering regulators unique to hypervirulent strains. Lastly, by comparing regulatory elements compiled in this study to genes shown to be essential for AB5075 infection, we were able to highlight elements with a specific importance for pathogenic behaviour. Collectively, our work offers a unique insight into the regulatory network of A. baumannii strains, and provides insight into the evolution of hypervirulent lineages.

PER-8, a Novel Extended-Spectrum β-Lactamase PER Variant, from an Acinetobacter baumannii Clinical Isolate in Nepal

A novel PER-type extended-spectrum β-lactamase, PER-8, was identified in an Acinetobacter baumannii clinical isolate obtained in Nepal. The amino acid sequence of PER-8 has a substitution at position 39 (Gly to Glu) compared with that of PER-7. The k_cat/K_m ratio of PER-8 for aztreonam was lower than that of PER-7, while the k_cat/K_m ratio of PER-8 for imipenem was higher than that of PER-7. The genomic environment surrounding bla_PER-8 was intI1 bla_PSE-1qacEDI sulI ISCR1-bla_PER-8gts sulI orfX on a 100-kb plasmid.

Acinetobacter baumannii Biofilm Formation in Human Serum and Disruption by Gallium

Biofilm-associated infections caused by Acinetobacter baumannii are extremely recalcitrant to antibiotic treatment. We report that A. baumannii develops a mature biofilm when grown in complement-free human serum (HS). We demonstrate that 16 μM gallium nitrate (GaN) drastically reduces A. baumannii growth and biofilm formation in HS, whereas 64 μM GaN causes massive disruption of preformed A. baumannii biofilm. These findings pave the way to the repurposing of GaN as an antibiofilm agent for A. baumannii.

Bibliometric analysis of global scientific research on carbapenem resistance (1986-2015)

BACKGROUND

Antimicrobial resistance is a global public health challenge and carbapenem resistance, in particular, is considered an urgent global health threat. This study was carried out to give a bibliometric overview of literature on carbapenem resistance. In specific, number of publications, top productive countries and institutes, highly cited articles, citation analysis, co-authorships, international collaboration, top active authors, and journals publishing articles on carbapenem resistance were analyzed and discussed.

METHODS

Specific keywords pertaining to carbapenem resistance were used in Scopus database. Quantitative and qualitative analysis of retrieved data were presented using appropriate bibliometric indicators and visualization maps.

RESULTS

A total of 2617 journal articles were retrieved. The average number of citations per article was of 21.47. The growth of publications showed a dramatic increase from 2008 to 2015. Approximately 9 % of retrieved articles on carbapenem resistance were published in Antimicrobial Agents and Chemotherapy journal. Retrieved articles were published by 102 different countries. The United States of America (USA) contributed most with 437 (16.70 %) articles followed by China with 257 (9.82 %) articles. When productivity was stratified by population size, Greece ranked first followed by France. Greece also ranked first when data were stratified by gross domestic product (GDP). Asian countries have lesser international collaboration compared with other countries in the top ten list. Five of top ten productive institutes were Europeans (France, the UK, Greece, Italy, and Switzerland) and two were Asians (China and South Korea). Other active institutes included an Israeli and a Brazilian institute. Four of the top ten cited articles were published in Antimicrobial Agents and Chemotherapy journal and two were published in The Lancet Infectious Diseases.

CONCLUSION

There was a dramatic increase in number of publications on carbapenem resistance in the past few years. These publications were produced from different world regions including Asia, Europe, Middle East, and Latin America. International collaboration needs to be encouraged particularly for researchers in Asia. Molecular biology and epidemiology dominated the theme of the top ten cited articles on carbapenem resistance. This bibliometric study will hopefully help health policy makers in planning future research and allocating funds pertaining to carbapenem resistance.

Resistance mechanisms

By definition, the terms sepsis and septic shock refer to a potentially fatal infectious state in which the early administration of an effective antibiotic is the most significant determinant of the outcome. Because of the global spread of resistant bacteria, the efficacy of antibiotics has been severely compromised. S. pneumonia, Escherichia coli (E. coli), Klebsiella, Acinetobacter, and Pseudomonas are the predominant pathogens of sepsis and septic shock. It is common for E. coli, Klebsiella, Acinetobacter and Pseudomonas to be resistant to multiple drugs. Multiple drug resistance is caused by the interplay of multiple resistance mechanisms those emerge via the acquisition of extraneous resistance determinants or spontaneous mutations. Extended-spectrum beta-lactamases (ESBLs), carbapenemases, aminoglycoside-modifying enzymes (AMEs) and quinolone resistance determinants are typically external and disseminate on mobile genetic elements, while porin-efflux mechanisms are activated by spontaneous modifications of inherited structures. Porin and efflux mechanisms are frequent companions of multiple drug resistance in Acinetobacter and P. aeruginosa, but only occasionally detected among E. coli and Klebsiella. Antibiotic resistance became a global health threat. This review examines the major resistance mechanisms of the leading microorganisms of sepsis.

VEB-1 extended-spectrum β-lactamase-producing multidrug-resistant Proteus mirabilis sepsis outbreak in a neonatal intensive care unit in India: clinical and diagnostic implications

Introduction:

Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, multidrug-resistant (MDR) pathogens, are increasingly implicated in nosocomial outbreaksworldwide, particularly in neonatal intensive care units (NICUs). Proteus mirabilis is an uncommon nosocomial pathogen causing sepsis in neonates.

Case Presentation:

We report an outbreak of ESBL-positive MDR P. mirabilis sepsis involving five babies within 10 days in a NICU, which was promptly detected and managed. The aim of this study was to characterize the molecular mechanism of resistance to third-generation cephalosporins (3GCs) in the bacteria. Surveillance cultures were collected from health-care personnel (hand swabs, urine) and the surrounding patient-care environment. Ribotyping was performed to determine the clonality of the strain. Thirteen P. mirabilis were recovered from the blood cultures of the five babies and surveillance cultures. Twelve isolates were positive for the VEB-1 ESBL type, and were susceptible only to ciprofloxacin and carbapenems. There was an unusual phenotypic synergy observed between the 3GCs and imipenem/cefoxitin. The source of infection was traced to a contaminated multidose vial. The outbreak was associated with a high mortality (80 %). A change of empirical antibiotic policy to ciprofloxacin, with strict infection control measures, brought the outbreak to an abrupt end.

Conclusion:

This is believed to be the first report of a nosocomial outbreak of VEB-1 ESBL-producing P. mirabilis sepsis in neonates from India. The present report of infection due to VEB-1-producing P. mirabilis, an uncommon pathogen for an epidemic in a neonatal unit, highlights the growing significance of such Gram-negative bacteria as a cause of infections in newborns. Epidemic spread in a neonatal unit of an ESBL-producing Proteus species, which also had an intrinsically reduced susceptibility to imipenem, and resistance to colistin and tigecycline, can be a threatening situation and can result in high neonatal mortality unless recognized and controlled in a timely manner.

Genome sequence of OXA-23 producing Acinetobacter baumannii IHIT7853, a carbapenem-resistant strain from a cat belonging to international clone IC1

Background

Multidrug resistance in Acinetobacter baumannii has dramatically increased in recent years worldwide. Thus, last-line antibiotics like carbapenems are increasingly being used which in turn further augments selection pressure for resistant strains. Resistance to carbapenems in A. baumannii is frequently mediated by carbapenemases, particularly OXA-23 and OXA-58. Carbapenemase-producing bacteria are mainly described in human patients and the intestinal tract represents a common source for such pathogens. In this study, we sequenced and analyzed the genome of A. baumannii IHIT7853, a carbapenem-resistant, OXA-23 producing strain isolated from cystitis in a cat in 2000 in Germany.

Results

Phylogenetic analysis revealed that IHIT7853 belonged to the globally distributed international clone IC1 and MLST type ST1/ST231 (Pasteur/Oxford MLST scheme). A phylogenetic tree based on the maximum common genome of 18 A. baumannii isolates placed IHIT7853 close to human clinical isolates, such as the multidrug-resistant (MDR) outbreak strain AYE that was isolated from a patient with pneumonia and cystitis in 2001 in France. The OXA-23 plasmid sequence could be determined as 53,995 bp in size, possessing resistance genes strA and strB in addition to bla_OXA-23.

Conclusions

The analysis of the genome of IHIT7853 reveals that companion animals carry MDR A. baumannii that resemble relevant clonal lineages involved in severe infections in humans. As urinary tract infections are often caused by bacteria that reside in the intestinal tract, future studies should unveil, if the animal gut serves as a source for MDR A. baumannii.

Identification of Novel VEB β-Lactamase Enzymes and Their Impact on Avibactam Inhibition

Ceftazidime-avibactam has activity against Pseudomonas aeruginosa and Enterobacteriaceae expressing numerous class A and class C β-lactamases, although the ability to inhibit many minor enzyme variants has not been established. Novel VEB class A β-lactamases were identified during characterization of surveillance isolates. The cloned novel VEB β-lactamases possessed an extended-spectrum β-lactamase phenotype and were inhibited by avibactam in a concentration-dependent manner. The residues that comprised the avibactam binding pocket were either identical or functionally conserved. These data demonstrate that avibactam can inhibit VEB β-lactamases.

Antibiotic Resistance Patterns and a Survey of Metallo-β-Lactamase Genes Including bla-IMP and bla-VIM Types in Acinetobacter baumannii Isolated from Hospital Patients in Tehran

Background: Metallo-β-lactamases (MBLs) producing strains of Acinetobacter baumannii are serious etiological agents of hospital infections worldwide. Among the β- lactams, carbapenems are the most effective antibiotics used against A. baumannii. However, resistance to these drugs among clinical strains of A. baumannii has been increasing in recent years. In this study, the antimicrobial sensitivity patterns of A. baumannii strains isolated from eleven different hospitals in Tehran, Iran, and the prevalence of MBL genes (bla-VIM and bla-IMP) were determined. Method: During a period of 5 months, 176 isolates of A. baumannii were collected from different clinical specimens from hospitalized patients in Tehran. All isolates were confirmed by biochemical methods. The isolates were tested for antibiotic sensitivity by the Kirby-Bauer disk diffusion method. Following minimum inhibitory concentration determination, imipenem-resistant isolates were further tested for MBL production by the double disk synergy test (DDST) method. PCR assays were performed for the detection of the MBL genes bla-IMP and bla-VIM. Results: The DDST phenotypic method indicated that among the 169 imipenem-resistant isolates, 165 strains were MBL positive. The PCR assays revealed that 63 of the overall isolates (36%) carried the bla-VIM gene and 70 strains (40%) harbored bla-IMP. Conclusions: It is obvious that nosocomial infections associated with multidrug-resistant Acinetobacter spp. are on the rise. Therefore, the determination of antibiotic sensitivity patterns and screening for MBL production among A. baumannii isolates is important for controlling clinical Acinetobacter infections.

Prevalence of Extended-Spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Isolates in Nosocomial and Community-Acquired Urinary Tract Infections

Background

Klebsiella pneumoniae is a family member of Enterobacteriaceae. Isolates of K. pneumoniae produce enzymes that cause decomposition of third generation cephalosporins. These enzymes are known as extended-spectrum beta-lactamase (ESBL). Resistance of K. pneumoniae to beta-lactamase antibiotics is commonly mediated by beta-lactamase genes.

Objectives

The aim of this study was to identify the ESBL produced by K. pneumoniae isolates that cause community-acquired and nosocomial urinary tract infections within a one-year period (2013 to 2014) in Kashani and Hajar university hospitals of Shahrekord, Iran.

Patients and Methods

From 2013 to 2014, 150 strains of K. pneumoniae isolate from two different populations with nosocomial and community-acquired infections were collected. The strains were then investigated by double disk synergism and multiplex polymerase chain reaction (PCR).

Results

The study population of 150 patients with nosocomial and community-acquired infections were divided to two groups of 75 each. We found that 48 of the K. pneumoniae isolates in the patients with nosocomial infection and 39 isolates in those with community-acquired infections produced ESBL. The prevalence of TEM1, SHV1 and VEB1 in ESBL-producing isolates in nosocomial patients was 24%, 29.3% and 10.6%, and in community-acquired patients, 17.3%, 22.7% and 8%, respectively.

Conclusions

The prevalence of ESBL-producing K. pneumoniae isolate is of great concern; therefore, continuous investigation seems essential to monitor ESBL-producing bacteria in patients with nosocomial and community-acquired infections.

Wide distribution of carbapenem resistant Acinetobacter baumannii in burns patients in Iran

Antimicrobial resistance in carbapenem non-susceptible Acinetobacter baumannii (CNSAb) is a major public health concern globally. This study determined the antibiotic resistance and molecular epidemiology of CNSAb isolates from a referral burn center in Tehran, Iran. Sixty-nine CNSAb isolates were tested for susceptibility to antimicrobial agents using the E test methodology. Multiple locus variable number tandem repeat analysis (MLVA), Multilocus sequence typing (MLST) and multiplex PCR were performed. PCR assays tested for ambler classes A, B, and D β-lactamases. Detection of ISAba1, characterization of integrons, and biofilm formation were investigated. Fifty-three (77%) isolates revealed XDR phenotypes. High prevalence of bla_OXA-23-like (88%) and bla_PER-1 (54%) were detected. ISAba1 was detected upstream of bla_ADC, bla_OXA-23-like and bla_OXA51-like genes in, 97, 42, and 26% of isolates, respectively. Thirty-one (45%) isolates were assigned to international clone (IC) variants. MLVA identified 56 distinct types with six clusters and 53 singleton genotypes. Forty previously known MLST sequence types forming 5 clonal complexes were identified. The Class 1 integron (class 1 integrons) gene was identified in 84% of the isolates. The most prevalent (33%) cassette combination was aacA4-catB8-aadA1. The IC variants were predominant in the A. baumannii lineage with the ability to form strong biofilms. The XDR-CNSAb from burned patients in Iran is resistant to various antimicrobials, including tigecycline. This study shows wide genetic diversity in CNSAb. Integrating the new Iranian A. baumannii IC variants into the epidemiologic clonal and susceptibility profile databases can help effective global control measures against the XDR-CNSAb pandemic.

Emerging broad-spectrum resistance in Pseudomonas aeruginosa and Acinetobacter baumannii: Mechanisms and epidemiology

Multidrug resistance is quite common among non-fermenting Gram-negative rods, in particular among clinically relevant species including Pseudomonas aeruginosa and Acinetobacter baumannii. These bacterial species, which are mainly nosocomial pathogens, possess a diversity of resistance mechanisms that may lead to multidrug or even pandrug resistance. Extended-spectrum β-lactamases (ESBLs) conferring resistance to broad-spectrum cephalosporins, carbapenemases conferring resistance to carbapenems, and 16S rRNA methylases conferring resistance to all clinically relevant aminoglycosides are the most important causes of concern. Concomitant resistance to fluoroquinolones, polymyxins (colistin) and tigecycline may lead to pandrug resistance. The most important mechanisms of resistance in P. aeruginosa and A. baumannii and their most recent dissemination worldwide are detailed here.

Complete genome sequence of hypervirulent and outbreak-associated Acinetobacter baumannii strain LAC-4: epidemiology, resistance genetic determinants and potential virulence factors

Acinetobacter baumannii is an important human pathogen due to its multi-drug resistance. In this study, the genome of an ST10 outbreak A. baumannii isolate LAC-4 was completely sequenced to better understand its epidemiology, antibiotic resistance genetic determinants and potential virulence factors. Compared with 20 other complete genomes of A. baumannii, LAC-4 genome harbors at least 12 copies of five distinct insertion sequences. It contains 12 and 14 copies of two novel IS elements, ISAba25 and ISAba26, respectively. Additionally, three novel composite transposons were identified: Tn6250, Tn6251 and Tn6252, two of which contain resistance genes. The antibiotic resistance genetic determinants on the LAC-4 genome correlate well with observed antimicrobial susceptibility patterns. Moreover, twelve genomic islands (GI) were identified in LAC-4 genome. Among them, the 33.4-kb GI12 contains a large number of genes which constitute the K (capsule) locus. LAC-4 harbors several unique putative virulence factor loci. Furthermore, LAC-4 and all 19 other outbreak isolates were found to harbor a heme oxygenase gene (hemO)-containing gene cluster. The sequencing of the first complete genome of an ST10 A. baumannii clinical strain should accelerate our understanding of the epidemiology, mechanisms of resistance and virulence of A. baumannii.

Current molecular methods in epidemiological typing of Acinetobacter baumannii

ABSTRACT 

The emergence of Acinetobacter baumannii during recent decades as an important nosocomial pathogen responsible of worldwide, intensively documented, outbreaks has resulted in a need for effective epidemiological typing methods. Throughout the years, many typing methods for A. baumannii epidemiological studies have been proposed from phenotypic to molecular methods. Currently, the use of phenotypic typing methods have declined considerably and been progressively replaced by molecular methods. In this review, we introduce the current molecular methods available for A. baumannii typing. Each method has its own advantages and disadvantages, and the selection of an appropriate genotyping method depends on studied objectives. This review sheds light on questions in different epidemiological settings and most molecular methods used to fit these objectives.

Co-production of ESBL and AmpC β-Lactamases in Clinical Isolates of A. baumannii and A. lwoffii in a Tertiary Care Hospital From Northern India

BACKGROUND

Acinetobacter baumannii is an important cause of health care associated infections which are difficult to control and treat, because of widespread antimicrobial resistance which is possessed by this organism.

AIMS

The aim of the present study was to know the prevalence of ESBLs and AmpC β-lactamases in clinical isolates of Acinetobacter spp. which were cultured from various clinical specimens by using different phenotypic methods.

SETTINGS AND DESIGN

Study was conducted over a period of one year at the Microbiology Department of a tertiary care teaching hospital. A total of 100 consecutive, non-duplicate strains of Acinetobacter species which were isolated from various clinical samples were included.

MATERIALS AND METHODS

All the isolates were identified by standard microbiological procedures and antimicrobial susceptibility testing was done by Kirby-Bauer disc diffusion technique. Isolates which showed reduced susceptibilities to third generation cephalosporins were tested for ESBL production by CLSI double disc synergy method and also by using sulbactam as an inhibitory agent. Isolates which showed reduced susceptibilities to cefoxitin were tested for AmpC detection by doing AmpC disc test.

STATISTICAL ANALYSIS

SPSS, version 17 was used to calculate p-value. If the p-value was <0.05, it was considered to be significant.

RESULTS

Out of 100 isolates, 82 were Acinetobacter baumannii and 18 were Acinetobacter lwoffii. ESBL were mentioned in 4% of the Acinetobacter isolates and in 77% of the isolates by using clavulanic acid and sulbactam as inhibitory agents respectively. AmpC β-lactamase production was detected in 60% isolates of Acinetobacter spp. Co-production of both ESBL and AmpC enzymes were seen in 29% of the Acinetobacter strains.

CONCLUSION

Failure in detecting β-lactamases contributes to their uncontrolled spread and therapeutic failures. Hence, these β-lactamases should be detected routinely and they should be reported to clinicians in time, so that inappropriate use of antibiotics can be stopped in time.

Antimicrobial susceptibility pattern in nosocomial infections caused by Acinetobacter species in Asir Region, Saudi Arabia

This study aimed at evaluating the sensitivity of antibiotics towards nosocomial infections caused by Acinetobacter species. The study took place during the period Dec. 2011- Dec. 2012 at Assir Central Hospital in collaboration with the department of microbiology, college of medicine, King Khalid University, Abha. A prospective study involving 150 patients presented with nosocomial infections due to Acinetobacter species detected by bacteriological tests; direct microscopy, culture in blood agar media, fermentation test in MacConkey media and MIC (minimum inhibitory concentration) for antibiotics sensitivity using Muller Hinton media and Chemical test using API 20. A 150 nosocomial infections in this study showed gram-negative coccobacilli, non motile, glucose-negative fermentor and oxidase negative. All isolates showed 100% sensitivity to: Imipramine, Meropenem, Colistin. From the rest of tested antibiotics the higher resistant ones were; Nitrofurantoin 87% and Cefoxitin 85%. The least resistant antibiotics; Imipenem 3% and Ticarcillin 7%. While variable resistance in the rest of tested antimicrobials. A 47 patients (31.3%) have used antibiotics prior to this study. The high rate of usage occurred in elder patients. The frequency of Acinetobacter calcoaceticus baumannii complex multi-drugs resistance ABCMDR is rising including almost all commonly used antibiotics. Only few antibiotics exert 100% sensitivity towards these bacteria.

Class D β-lactamases: are they all carbapenemases?

Carbapenem-hydrolyzing class D β-lactamases (CHDLs) are enzymes of the utmost clinical importance due to their ability to produce resistance to carbapenems, the antibiotics of last resort for the treatment of various life-threatening infections. The vast majority of these enzymes have been identified in Acinetobacter spp., notably in Acinetobacter baumannii. The OXA-2 and OXA-10 enzymes predominantly occur in Pseudomonas aeruginosa and are currently classified as narrow-spectrum class D β-lactamases. Here we demonstrate that when OXA-2 and OXA-10 are expressed in Escherichia coli strain JM83, they produce a narrow-spectrum antibiotic resistance pattern. When the enzymes are expressed in A. baumannii ATCC 17978, however, they behave as extended-spectrum β-lactamases and confer resistance to carbapenem antibiotics. Kinetic studies of OXA-2 and OXA-10 with four carbapenems have demonstrated that their catalytic efficiencies with these antibiotics are in the same range as those of some recognized class D carbapenemases. These results are in disagreement with the classification of the OXA-2 and OXA-10 enzymes as narrow-spectrum β-lactamases, and they suggest that other class D enzymes that are currently regarded as noncarbapenemases may in fact be CHDLs.

Antimicrobial Resistance Patterns and Prevalence of blaPER-1 and blaVEB-1 Genes Among ESBL-producing Pseudomonas aeruginosa Isolates in West of Iran

BACKGROUND

Pseudomonas aeruginosa is a leading cause of nosocomial infections worldwide. Resistance of P. aeruginosa strains to the broad-spectrum cephalosporins may be caused by extended-spectrum β-lactamases (ESBLs).

OBJECTIVES

The aim of this study was to determine the antimicrobial resistance patterns and prevalence of PER-1 and VEB-1 type genes among ESBL producing strains of P. aeruginosa.

MATERIAL AND METHODS

A total of 106 P. aeruginosa isolates were collected from two university hospitals in Hamadan, Iran, during a7-month study (2009). The antimicrobial susceptibility of isolates was determined by disc diffusion method and interpreted according to the clinical and laboratory standards institute (CLSI) recommendations. Production of ESBL was determined by combined disk test and presence of PER-1 and VEB-1 type ESBL genes was identified by PCR.

RESULTS

The resistance against broad-spectrum cephalosporins and monobactames were: cefepime (97%), cefotaxime (92.5%) ceftazidime (51%), and aztreonam (27%). Ciprofloxacin (91.5%), imipenem (84.9%) and meropenem (82.1%) were the most effective anti-pseudomonas agents in this study. The results revealed that 88.7% of the isolates were multidrug resistant, 58.25% of those were ESBL positive. Sixteen (26.6%), 9 (15%) and 3 (5%) strains among ESBL-producing strains contained blaPER-1, blaVEB and blaPER-1-blaVEB, respectively.

CONCLUSIONS

This study highlighted the need to establish antimicrobial resistance surveillance networks for P. aeruginosa to determine the appropriate empirical treatment regimens. The high prevalence of multidrug resistance and production of ESBLs in P. aeruginosa isolates confirms the necessity of protocols considering these issues in the hospitals.