Distribution and expression of the aac(6')-Im (aacA16) aminoglycoside resistance gene.

BACKGROUND: The aac(6')-Im (aacA16) amikacin, netilmicin and tobramycin resistance gene cassette had been circulating globally undetected for many years in a sublineage of Acinetobacter baumannii global clone 2. OBJECTIVES: To identify sources for the aac(6')-Im fragment found in A. baumannii. METHODS: MinION long-read sequencing and Unicycler hybrid assemblies were used to determine the genetic context of the aac(6')-Im gene. Quantitative reverse transcriptase PCR was used to measure expression. RESULTS: Among >60 000 non-Acinetobacter draft genomes in the MRSN collection, the aac(6')-Im gene was detected in Pseudomonas putida and Enterobacter hormaechei isolates recovered from patients in Thailand between 2016 and 2019. Genomes of multiply resistant P. putida MRSN365855 and E. hormaechei MRSN791417 were completed. The class 1 integron containing the aac(6')-Im cassette was in the chromosome in MRSN365855, and in an HI2 plasmid in MRSN791417. However, MRSN791417 was amikacin susceptible and the gene was not expressed due to loss of the Pc promoter of the integron. Further examples of aac(6')-Im in plasmids from or the chromosome of various Gram-negative species were found in the GenBank nucleotide database. The aac(6')-Im context in integrons in pMRSN791417-8 and a Klebsiella plasmid pAMR200031 shared similarities with the aac(6')-Im region of AbGRI2-Im islands in A. baumannii. In other cases, the cassette array including the aac(6')-Im cassette was different. CONCLUSIONS: The aac(6')-Im gene is widespread, being found so far in several different species and in several different gene cassette arrays. The lack of amikacin resistance in E. hormaechei highlights the importance of correlating resistance gene content and antibiotic resistance phenotype.

Psychosocial support interventions for children and adolescents experiencing gender dysphoria or incongruence: a systematic review.

BACKGROUND: National and international guidelines recommend that psychosocial support should be a key component of the care offered to children and adolescents experiencing gender dysphoria/incongruence. However, specific approaches or interventions are not recommended. AIM: To identify and summarise evidence on the outcomes of psychosocial support interventions for children and adolescents (age 0-18) experiencing gender dysphoria/incongruence. METHODS: Systematic review and narrative synthesis. Database searches (MEDLINE; EMBASE; CINAHL; PsycINFO; Web of Science) were performed in April 2022, with results assessed independently by two reviewers. Peer-reviewed articles reporting the results of studies measuring outcomes of psychosocial support interventions were included. Quality was assessed using the Mixed Methods Appraisal Tool. RESULTS: Ten studies were included. Half were conducted in the US, with others from Australia, Canada, New Zealand and the UK. Six were pre-post analyses or cohort studies, three were mixed methods, and one was a secondary analysis of intervention data from four trials. Most studies were of low quality. Most analyses of mental health and psychosocial outcomes showed either benefit or no change, with none indicating negative or adverse effects. CONCLUSIONS: The small number of low-quality studies limits conclusions about the effectiveness of psychosocial interventions for children/adolescents experiencing gender dysphoria/incongruence. Clarity on the intervention approach as well as the core outcomes would support the future aggregation of evidence. More robust methodology and reporting is required. PROSPERO REGISTRATION NUMBER: CRD42021289659.

Characteristics of children and adolescents referred to specialist gender services: a systematic review.

BACKGROUND: Increasing numbers of children/adolescents experiencing gender dysphoria/incongruence are being referred to specialist gender services. Services and practice guidelines are responding to these changes. AIM: This systematic review examines the numbers and characteristics of children/adolescents (under 18) referred to specialist gender or endocrinology services. METHODS: Database searches were performed (April 2022), with results assessed independently by two reviewers. Peer-reviewed articles providing at least birth-registered sex or age at referral were included. Demographic, gender-related, mental health, neurodevelopmental conditions and adverse childhood experience data were extracted. A narrative approach to synthesis was used and where appropriate proportions were combined in a meta-analysis. RESULTS: 143 studies from 131 articles across 17 countries were included. There was a twofold to threefold increase in the number of referrals and a steady increase in birth-registered females being referred. There is inconsistent collection and reporting of key data across many of the studies. Approximately 60% of children/adolescents referred to services had made steps to present themselves in their preferred gender. Just under 50% of studies reported data on depression and/or anxiety and under 20% reported data on other mental health issues and neurodevelopmental conditions. Changes in the characteristics of referrals over time were generally not reported. CONCLUSIONS: Services need to capture, assess and respond to the potentially co-occurring complexities of children/adolescents being referred to specialist gender and endocrine services. Agreement on the core characteristics for collection at referral/assessment would help to ensure services are capturing data as well as developing pathways to meet the needs of these children.PROSPERO registration number CRD42021289659.

Interventions to suppress puberty in adolescents experiencing gender dysphoria or incongruence: a systematic review.

BACKGROUND: Treatment to suppress or lessen effects of puberty are outlined in clinical guidelines for adolescents experiencing gender dysphoria/incongruence. Robust evidence concerning risks and benefits is lacking and there is a need to aggregate evidence as new studies are published. AIM: To identify and synthesise studies assessing the outcomes of puberty suppression in adolescents experiencing gender dysphoria/incongruence. METHODS: A systematic review and narrative synthesis. Database searches (Medline, Embase, CINAHL, PsycINFO, Web of Science) were performed in April 2022, with results assessed independently by two reviewers. An adapted version of the Newcastle-Ottawa Scale for cohort studies was used to appraise study quality. Only moderate-quality and high-quality studies were synthesised. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guidelines were used. RESULTS: 11 cohort, 8 cross-sectional and 31 pre-post studies were included (n=50). One cross-sectional study was high quality, 25 studies were moderate quality (including 5 cohort studies) and 24 were low quality. Synthesis of moderate-quality and high-quality studies showed consistent evidence demonstrating efficacy for suppressing puberty. Height increased in multiple studies, although not in line with expected growth. Multiple studies reported reductions in bone density during treatment. Limited and/or inconsistent evidence was found in relation to gender dysphoria, psychological and psychosocial health, body satisfaction, cardiometabolic risk, cognitive development and fertility. CONCLUSIONS: There is a lack of high-quality research assessing puberty suppression in adolescents experiencing gender dysphoria/incongruence. No conclusions can be drawn about the impact on gender dysphoria, mental and psychosocial health or cognitive development. Bone health and height may be compromised during treatment. More recent studies published since April 2022 until January 2024 also support the conclusions of this review. PROSPERO REGISTRATION NUMBER: CRD42021289659.

Clinical guidelines for children and adolescents experiencing gender dysphoria or incongruence: a systematic review of guideline quality (part 1).

BACKGROUND: Increasing numbers of children and adolescents experiencing gender dysphoria/incongruence are being referred to specialist gender services. There are various guidelines outlining approaches to the clinical care of these children and adolescents. AIM: To examine the quality and development of published guidelines or clinical guidance containing recommendations for managing gender dysphoria/incongruence in children and/or adolescents (age 0-18). A separate paper reports the synthesis of guideline recommendations. METHODS: A systematic review and narrative synthesis. Databases (Medline, Embase, CINAHL, PsycINFO, Web of Science) were searched to April 2022 and web-based searches and contact with international experts continued to December 2022, with results assessed independently by two reviewers. The Appraisal of Guidelines for Research and Evaluation tool was used to examine guideline quality. RESULTS: Twenty-three guidelines/clinical guidance publications (1998-2022) were identified (4 international, 3 regional and 16 national). The quality and methods reporting in these varied considerably. Few guidelines systematically reviewed empirical evidence, and links between evidence and recommendations were often unclear. Although most consulted with relevant stakeholders, including 10 which involved service users or user representatives, it was often unclear how this influenced recommendations and only two reported including children/adolescents and/or parents. Guidelines also lacked clarity about implementation. Two international guidelines (World Professional Association for Transgender Health and Endocrine Society) formed the basis for most other guidance, influencing their development and recommendations. CONCLUSIONS: Most clinical guidance for managing children/adolescents experiencing gender dysphoria/incongruence lacks an independent and evidence-based approach and information about how recommendations were developed. This should be considered when using these to inform service development and clinical practice. PROSPERO REGISTRATION NUMBER: CRD42021289659.

Gender services for children and adolescents across the EU-15+ countries: an online survey.

BACKGROUND: Over the last 10-15 years, there has been an increase in the number of children and adolescents referred to gender services, particularly among adolescent birth-registered females. This population shows a higher prevalence of co-occurring mental health difficulties and neurodevelopmental conditions. Some countries have recently restricted access to medical treatments in recognition of the uncertain evidence base. AIM: To understand the current provision of gender services for children and adolescents across the EU-15+ countries that have comparable high-income healthcare systems, to inform service development in the UK. METHODS: An e-survey of paediatric gender services was conducted between September 2022 and April 2023. It covered service structure, care pathways, interventions and data collection. Data were described and compared to identify similarities and differences among participating services. RESULTS: 15 services in eight countries (Australia, Belgium, Denmark, Norway, Northern Ireland, The Netherlands, Spain and Finland) responded. While a multidisciplinary team was present in all services, its composition and organisation varied. Clinical practice was informed by international guidelines, with four countries following their own national guidelines. Differences were observed in referral criteria, care pathways for prepubertal children and those with co-occurring conditions. Eligibility criteria for medical interventions also varied. Psychosocial support and interventions were limited, and outcome data collection was scarce. CONCLUSIONS: This survey revealed both similarities and key variations in the clinical practice of paediatric gender services across eight different countries. The study emphasises the need for service development that both considers the management of co-occurring conditions and embeds routine data collection in practice.

Care pathways of children and adolescents referred to specialist gender services: a systematic review.

BACKGROUND: Increasing numbers of children and adolescents experiencing gender dysphoria/incongruence are being referred to specialist gender services. However, little is currently known about the proportions accessing different types of care and treatment following referral. AIM: This systematic review examines the range of care pathways of children/adolescents (under 18) referred to specialist gender or endocrinology services. METHODS: Database searches were performed (April 2022), with results assessed independently by two reviewers. Peer-reviewed articles providing data for numbers of children and/or adolescents at referral/assessment and their treatment pathways were included. A narrative approach to synthesis was used and where appropriate proportions were combined in a random-effects meta-analysis. RESULTS: 23 studies across nine countries were included, representing 6133 children and/or adolescents with a median age at assessment of 14-16 and overall a higher percentage of birth-registered females. Of those assessed, 36% (95% CI 27% to 45%) received puberty suppression, 51% (95% CI 40% to 62%) received masculinising or feminising hormones, 68% (95% CI 57% to 77%) received puberty suppression and/or hormones and 16% (95% CI 10% to 24%) received surgery. No study systematically reported information about the full pathway or psychological care received by children/adolescents. Follow-up in many studies was insufficient or unclear. Reasons for discontinuation were rarely provided. CONCLUSIONS: Prospective studies with long-term follow-up reporting information about the full range of pathways are needed to understand what happens to children and adolescents referred to specialist gender services. Information about provision of psychological care is needed considering high rates of psychosocial difficulties in this population.PROSPERO registration number CRD42021289659.

Clinical guidelines for children and adolescents experiencing gender dysphoria or incongruence: a systematic review of recommendations (part 2).

BACKGROUND: Increasing numbers of children and adolescents experiencing gender dysphoria/incongruence are being referred to specialist gender services and there are various published guidelines outlining approaches to clinical care. AIM: To examine the recommendations about the management of children and/or adolescents (age 0-18) experiencing gender dysphoria/incongruence in published guidelines or clinical guidance. A separate paper examines the quality and development of guidelines. METHODS: A systematic review and narrative synthesis. Databases (Medline, Embase, CINAHL, PsycINFO, Web of Science) were searched to April 2022 and web-based searches and contact with international experts continued to December 2022, with results assessed independently by two reviewers. The Appraisal of Guidelines for Research and Evaluation tool was used to examine guideline quality. RESULTS: 23 guidelines/clinical guidance publications (1998-2022) were identified (4 international, 3 regional, 16 national). Guidelines describe a similar care pathway starting with psychosocial care for prepubertal children, puberty suppressants followed by hormones for eligible adolescents and surgical interventions as these adolescents enter adulthood. In general, there is consensus that adolescents should receive a multidisciplinary assessment, although clear guidance about the purpose or approach is lacking. There are differing recommendations about when and on what basis psychological and medical interventions should be offered. There is limited guidance about what psychological care should be provided, about the management of prepubertal children or those with a non-binary gender identity, nor about pathways between specialist gender services and other providers. CONCLUSIONS: Published guidance describes a similar care pathway; however, there is no current consensus about the purpose and process of assessment for children or adolescents with gender dysphoria/incongruence, or about when psychological or hormonal interventions should be offered and on what basis. PROSPERO REGISTRATION NUMBER: CRD42021289659.

Masculinising and feminising hormone interventions for adolescents experiencing gender dysphoria or incongruence: a systematic review.

BACKGROUND: Clinical guidelines outline the use of hormones for masculinisation/feminisation in adolescents experiencing gender dysphoria or incongruence. Robust evidence concerning risks and benefits is lacking. There is a need to aggregate evidence as research becomes available. AIM: Identify and synthesise studies assessing the outcomes of hormones for masculinisation/feminisation in adolescents experiencing gender dysphoria/incongruence. METHODS: Systematic review and narrative synthesis. Database searches (MEDLINE, Embase, CINAHL, PsycINFO, Web of Science) were performed in April 2022, with results assessed independently by two reviewers. An adapted version of the Newcastle-Ottawa Scale for Cohort Studies was used to assess study quality. Moderate- and high-quality studies were synthesised. RESULTS: 12 cohort, 9 cross-sectional and 32 pre-post studies were included (n=53). One cohort study was high-quality. Other studies were moderate (n=33) and low-quality (n=19). Synthesis of high and moderate-quality studies showed consistent evidence demonstrating induction of puberty, although with varying feminising/masculinising effects. There was limited evidence regarding gender dysphoria, body satisfaction, psychosocial and cognitive outcomes, and fertility. Evidence from mainly pre-post studies with 12-month follow-up showed improvements in psychological outcomes. Inconsistent results were observed for height/growth, bone health and cardiometabolic effects. Most studies included adolescents who received puberty suppression, making it difficult to determine the effects of hormones alone. CONCLUSIONS: There is a lack of high-quality research assessing the use of hormones in adolescents experiencing gender dysphoria/incongruence. Moderate-quality evidence suggests mental health may be improved during treatment, but robust study is still required. For other outcomes, no conclusions can be drawn. More recent studies published since April 2022 until January 2024 also support the conclusions of this review.PROSPERO registration number: CRD42021289659.

Impact of social transition in relation to gender for children and adolescents: a systematic review.

BACKGROUND: Increasing numbers of children and adolescents experiencing gender dysphoria or incongruence are being referred to specialist gender services. Historically, social transitioning prior to assessment was rare but it is becoming more common. AIM: To identify and synthesise studies assessing the outcomes of social transition for children and adolescents (under 18) experiencing gender dysphoria/incongruence. METHODS: A systematic review and narrative sythesis. Database searches (Medline, Embase, CINAHL, PsycINFO, Web of Science) were perfomed in April 2022. Studies reporting any outcome of social transition (full or partial) for children and adolescents experiencing gender dysphoria/incongruence were included. An adapted version of the Newcastle-Ottawa Scale for cohort studies was used to appraise study quality. RESULTS: Eleven studies were included (children (n=8) and adolescents (n=3)) and most were of low quality. The majority were from the US, featured community samples and cross-sectional analyses. Different comparator groups were used, and outcomes related to mental health and gender identity reported. Overall studies consistently reported no difference in mental health outcomes for children who socially transitioned across all comparators. Studies found mixed evidence for adolescents who socially transitioned. CONCLUSIONS: It is difficult to assess the impact of social transition on children/adolescents due to the small volume and low quality of research in this area. Importantly, there are no prospective longitudinal studies with appropriate comparator groups assessing the impact of social transition on mental health or gender-related outcomes for children/adolescents. Professionals working in the area of gender identity and those seeking support should be aware of the absence of robust evidence of the benefits or harms of social transition for children and adolescents. PROSPERO REGISTRATION NUMBER: CRD42021289659.

Variation in the plasmid backbone and dif module content of R3-T33 Acinetobacter plasmids.

The predominant type of plasmids found in Acinetobacter species encode a Rep_3 initiation protein and many of these carry their accessory genes in dif modules. Here, available sequences of the 14 members of the group of Rep_3 plasmids typed as R3-T33, using a threshold of 95% identity in the repA gene, were compiled and compared. These plasmids were from various Acinetobacter species. The pdif sites were identified allowing the backbone and dif modules to be defined. As for other Rep_3 plasmids carrying dif modules, orfX encoding a protein of unknown function was found downstream of repA followed by a pdif site in the orientation XerC binding site-spacer-XerD binding site. Most backbones (n = 12) also included mobA and mobC genes but the two plasmids with the most diverged repA and orfX genes had different backbone contents. Although the gene content of the plasmid backbone was largely conserved, extensive recombinational exchange was detected and only two small groups carried identical or nearly identical backbones. Individual plasmids were associated with 1 to 13 dif modules. Many different dif modules were identified, including ones containing antibiotic or chromate resistance genes and several toxin/antitoxin gene pairs. In some cases, modules carrying the same genes were significantly diverged. Generally, the orientation of the pdif sites alternated such that C modules (XerC binding sites internal) alternated with D modules (XerD binding sites internal). However, fusions of two dif modules via mutational inactivation or loss of a pdif site were also detected.

Aminoglycoside resistance genes in early members of the Acinetobacter baumannii ST78A (SMAL, Italian clone) reside in an IS26-bounded island in the chromosome.

BACKGROUND: The Acinetobacter baumannii isolate called SMAL, previously used to determine the structures of capsular polysaccharide and lipooligosaccharide, was recovered in Pavia, Italy in 2002 among the collection of aminoglycoside-resistant isolates designated as SMAL type. This type was later called the Italian clone, then ST78. ST78 isolates are now widely distributed. OBJECTIVES: To establish the resistance gene complement and the location and structure of acquired resistance regions in early members of the Italian/ST78 clone. METHODS: The draft genome of SMAL2002 was assembled from Illumina MiSeq reads. Contigs containing resistance genes were joined and located in the chromosome using PCR with custom primers. The resistance profile was determined using disc diffusion. RESULTS: SMAL2002 is an ST78A isolate and includes three aminoglycoside resistance genes, aadB (gentamicin, kanamycin, tobramycin) aphA1 (kanamycin, neomycin) and aac(6')-Ian (amikacin, kanamycin, tobramycin). The aadB gene cassette is incorporated at a secondary site in a relative of the aphA1-containing, IS26-bounded pseudo-compound transposon, PTn6020. The aac(6')-Ian gene is in an adjacent IS26-bounded structure that includes sul2 (sulphonamide) and floR (florfenicol) resistance genes. The two pseudo-compound transposons overlap and are in the chromosomal hutU gene flanked by an 8 bp target site duplication. Although aac(6')-Ian was not noticed previously, the same genes and structures were found in several available draft genomes of early ST78A isolates. CONCLUSIONS: This study highlights the importance of correlating resistance profiles with resistance gene content. The location of acquired resistance genes in the SMAL2002 chromosome represents the original location in the ST78A lineage of ST78.

IS26 and the IS26 family: versatile resistance gene movers and genome reorganizers.

SUMMARYIn Gram-negative bacteria, the insertion sequence IS26 is highly active in disseminating antibiotic resistance genes. IS26 can recruit a gene or group of genes into the mobile gene pool and support their continued dissemination to new locations by creating pseudo-compound transposons (PCTs) that can be further mobilized by the insertion sequence (IS). IS26 can also enhance expression of adjacent potential resistance genes. IS26 encodes a DDE transposase but has unique properties. It forms cointegrates between two separate DNA molecules using two mechanisms. The well-known copy-in (replicative) route generates an additional IS copy and duplicates the target site. The recently discovered and more efficient and targeted conservative mechanism requires an IS in both participating molecules and does not generate any new sequence. The unit of movement for PCTs, known as a translocatable unit or TU, includes only one IS26. TU formed by homologous recombination between the bounding IS26s can be reincorporated via either cointegration route. However, the targeted conservative reaction is key to generation of arrays of overlapping PCTs seen in resistant pathogens. Using the copy-in route, IS26 can also act on a site in the same DNA molecule, either inverting adjacent DNA or generating an adjacent deletion plus a circular molecule carrying the DNA segment lost and an IS copy. If reincorporated, these circular molecules create a new PCT. IS26 is the best characterized IS in the IS26 family, which includes IS257/IS431, ISSau10, IS1216, IS1006, and IS1008 that are also implicated in spreading resistance genes in Gram-positive and Gram-negative pathogens.

Revised structure of the polysaccharide from Acinetobacter baumannii LUH5551 assigned as the K63 type capsular polysaccharide.

K63 capsular polysaccharide produced by Acinetobacter baumannii isolate LUH5551 (previously designated isolate O24) was re-examined using sugar analysis, Smith degradation, and one- and two-dimensional 1H and 13C NMR spectroscopy. Though previously reported as O24 consisting of linear tetrasaccharide units that include a 7-acetamido-5-acylamino form of 8-epilegionaminic acid [8eLeg5R7Ac, acylated at C5 with (S)-3-hydroxybutanoyl or acetyl (1:1)], the elucidated structure of the K63 type capsule was found to include a derivative of 5,7-diamino-3,5,7,9-tetradeoxy-d-glycero-d-galacto-non-2-ulosonic (legionaminic) acid, Leg5Ac7R, where R is either (S)-3-hydroxybutanoyl or an acetyl group (∼1:1 ratio). This finding is consistent with the presence of the lgaABCHIFG gene module for Leg5Ac7R biosynthesis in the KL63 gene cluster at the capsular polysaccharide (CPS) biosynthesis K locus in the LUH5551 genome. The glycosyltransferases (Gtrs) and Wzy polymerase encoded by KL63 were assigned to linkages in the linear K63 tetrasaccharide unit and linkage of the K63 units.

The Acinetobacter baumannii K70 and K9 capsular polysaccharides consist of related K-units linked by the same Wzy polymerase and cleaved by the same phage depolymerases.

IMPORTANCE: Bacteriophage show promise for the treatment of Acinetobacter baumannii infections that resist all therapeutically suitable antibiotics. Many tail-spike depolymerases encoded by phage that are able to degrade A. baumannii capsular polysaccharide (CPS) exhibit specificity for the linkage present between K-units that make up CPS polymers. This linkage is formed by a specific Wzy polymerase, and the ability to predict this linkage using sequence-based methods that identify the Wzy at the K locus could assist with the selection of phage for therapy. However, little is known about the specificity of Wzy polymerase enzymes. Here, we describe a Wzy polymerase that can accommodate two different but similar sugars as one of the residues it links and phage depolymerases that can cleave both types of bond that Wzy forms.

The extensively antibiotic resistant ST111 Acinetobacter baumannii isolate RBH2 carries an extensive mobile element complement of plasmids, transposons and insertion sequences.

The complete genome of RBH2, a sporadic, carbapenem resistant ST111 Acinetobacter baumannii isolate from Brisbane, Australia was determined and analysed. RBH2 is extensively resistant and the chromosome includes two transposons carrying antibiotic resistance genes, AbaR4 (oxa23 in Tn2006) and Tn7::Tn2006 (dfrA1, sat2, aadA1, oxa23). The chromosome also includes two copies of Tn6175, a transposon carrying putative copper resistance genes, and 1-17 copies of six different insertion sequences. RBH2 has six plasmids ranging in size from 6 kb - 141 kb, four carrying antibiotic resistance genes. Plasmids pRBH2-1 (aadB) and pRBH2-2 (aphA6 in TnaphA6) were found to be essentially identical to known plasmids pRAY*-v1 and pS21-1, respectively. The largest plasmids, pRBH2-5 (oxa23 in AbaR4) and pRBH2-6 (oxa23 in AbaR4::ISAba11 and sul2, tet(B), strA and strB in Tn6172) have known transfer-proficient relatives. pRBH2-5, an RP-T1 (RepAci6) plasmid, also carries a different putative copper resistance transposon related to Tn6177 found in pS21-2. The backbone of pRBH2-5 is related to those of previously described RepAci6 plasmids pAb-G7-2 and pA85-3 but has some distinctive features. Three different RepAci6 backbone types were distinguished, Type 1 (pAb-G7-2), Type 2 (pA85-3) and Type 3 (pRBH2-5 and pS21-2). pRBH2-6 is closely related to pAB3 and their backbones differ by only 5 SNPs. Plasmids pRBH2-3 and pRBH2-4 do not carry antibiotic resistance genes. pRBH2-3 does not include an identifiable rep gene and is a novel plasmid type. pRBH2-4 is of the R3-T3 type and includes segments of the larger pABTJ2 that heads this group. Other ST111 genomes carry different plasmids.

Acinetobacter baumannii GC2 Sublineage Carrying the aac(6')-Im Amikacin, Netilmicin, and Tobramycin Resistance Gene Cassette.

The aminoglycoside antibiotics amikacin, gentamicin, and tobramycin are important therapeutic options for Acinetobacter iinfections. Several genes that confer resistance to one or more of these antibiotics are prevalent in the globally distributed resistant clones of Acinetobacter baumannii, but the aac(6')-Im (aacA16) gene (amikacin, netilmicin, and tobramycin resistance), first reported in isolates from South Korea, has rarely been reported since. In this study, GC2 isolates (1999 to 2002) from Brisbane, Australia, carrying aac(6')-Im and belonging to the ST2:ST423:KL6:OCL1 type were identified and sequenced. The aac(6')-Im gene and surrounds have been incorporated into one end of the IS26-bounded AbGRI2 antibiotic resistance island and are accompanied by a characteristic 70.3-kbp deletion of adjacent chromosome. The compete genome of the 1999 isolate F46 (RBH46) includes only two copies of ISAba1 (in AbGRI1-3 and upstream of ampC) but later isolates, which differ from one another by <10 single nucleotide differences (SND), carry two to seven additional shared copies. Several complete GC2 genomes with aac(6')-Im in an AbGRI2 island (2004 to 2017; several countries) found in GenBank and two additional Australian A. baumannii isolates (2006) carry different gene sets, KL2, KL9, KL40, or KL52, at the capsule locus. These genomes include ISAba1 copies in a different set of shared locations. The distribution of SND between F46 and AYP-A2, a 2013 ST2:ST208:KL2:OCL1 isolate from Victoria, Australia, revealed that a 640-kbp segment that includes KL2 and the AbGRI1 resistance island replaces the corresponding region in F46. Over 1,000 A. baumannii draft genomes also include aac(6')-Im, indicating that it is currently globally disseminated and significantly underreported. IMPORTANCE Aminoglycosides are important therapeutic options for treatment of Acinetobacter infections. Here, we show that a little-known aminoglycoside resistance gene, aac(6')-Im (aacA16), that confers amikacin, netilmicin, and tobramycin resistance has been circulating undetected for many years in a sublineage of A. baumannii global clone 2 (GC2), generally with a second aminoglycoside resistance gene, aacC1, which confers resistance to gentamicin. These two genes are commonly found together in GC2 complete and draft genomes and globally distributed. One isolate appears to be ancestral, as its genome contains few ISAba1 copies, providing insight into the original source of this insertion sequence (IS), which is abundant in most GC2 isolates. Tracking ISAba1 spread can provide a simple means to track the development and ongoing evolution as well as the dissemination of specific lineages and detect the formation of many sublineages. The complete ancestral genome will provide an essential base point for tracking this process.

Effect of the S008-sgaCD operon on IncC plasmid stability in the presence of SGI1-K or absence of an SGI1 variant.

An IncC or IncA plasmid is needed to enable transfer of SGI1 type integrative mobilisable elements but an IncC plasmid does not stably co-exist with SGI1. However, the plasmid is stably maintained with SGI1-K, a natural SGI1 deletion variant that lacks the sgaDC genes (S007 and S006) and the upstream open reading frame (S008) found in the SGI1 backbone. Here, the effect of the sgaDC genes and S008 on the stability of an IncC plasmid in an Escherichia coli strain with or without SGI1-K was examined. Co-transcription of the S008 open reading frame with the downstream sgaDC genes was established. When a strain containing SGI1-K complemented with a pK18 plasmid that included S008-sgaDC or sgaDC expressed from the constitutive pUC promoter was grown without antibiotic selection, the resident IncC plasmid was rapidly lost but loss was slower when S008 was present. In contrast, SGI1-K and the S008-sgaDC or sgaDC plasmid were quite stably maintained for >100 generations. However, the high copy number plasmids carrying the SGI1-derived S008-sgaDC or sgaDC genes constitutively expressed could not be introduced into an E. coli strain carrying the IncC plasmid but without SGI1-K. Using equivalent plasmids with S008-sgaDC or sgaDC genes controlled by an arabinose-inducible promoter, under inducing conditions the IncC plasmid was stable but the plasmid containing the SGI1-derived genes was rapidly lost. This unexpected observation indicates that there are multiple interactions between the IncC plasmid and SGI1 in which the transcriptional activator genes sgaDC play a role. These interactions will require further investigation.

The Acinetobacter baumannii website (Ab-web): a multidisciplinary knowledge hub, communication platform, and workspace.

Acinetobacter baumannii is a Gram-negative bacterium increasingly implicated in hospital-acquired infections and outbreaks. Effective prevention and control of such infections are commonly challenged by the frequent emergence of multidrug-resistant strains. Here we introduce Ab-web (https://www.acinetobacterbaumannii.no), the first online platform for sharing expertise on A. baumannii. Ab-web is a species-centric knowledge hub, initially with 10 articles organized into two main sections, 'Overview' and 'Topics', and three themes, 'epidemiology', 'antibiotic resistance', and 'virulence'. The 'workspace' section provides a spot for colleagues to collaborate, build, and manage joint projects. Ab-web is a community-driven initiative amenable to constructive feedback and new ideas.

The RuvABC Holliday Junction Processing System Is Not Required for IS26-Mediated Targeted Conservative Cointegrate Formation.

The insertion sequence IS26 plays a key role in the spread of antibiotic resistance genes in Gram-negative bacteria. IS26 and members of the IS26 family are able to use two distinct mechanisms to form cointegrates made up of two DNA molecules linked via directly oriented copies of the IS. The well-known copy-in (formerly replicative) reaction occurs at very low frequency, and the more recently discovered targeted conservative reaction, which joins two molecules that already include an IS, is substantially more efficient. Experimental evidence has indicated that, in the targeted conservative mode, the action of Tnp26, the IS26 transposase, is required only at one end. How the Holliday junction (HJ) intermediate generated by the Tnp26-catalyzed single-strand transfer is processed to form the cointegrate is not known. We recently proposed that branch migration and resolution via the RuvABC system may be needed to process the HJ; here, we have tested this hypothesis. In reactions between a wild-type and a mutant IS26, the presence of mismatched bases near one IS end impeded the use of that end. In addition, evidence of gene conversion, potentially consistent with branch migration, was detected in some of the cointegrates formed. However, the targeted conservative reaction occurred in strains that lacked the recG, ruvA, or ruvC genes. As the RuvC HJ resolvase is not required for targeted conservative cointegrate formation, the HJ intermediate formed by the action of Tnp26 must be resolved by an alternate route. IMPORTANCE In Gram-negative bacteria, the contribution of IS26 to the spread of antibiotic resistance and other genes that provide cells with an advantage under specific conditions far exceeds that of any other known insertion sequence. This is likely due to the unique mechanistic features of IS26 action, particularly its propensity to cause deletions of adjacent DNA segments and the ability of IS26 to use two distinct reaction modes for cointegrate formation. The high frequency of the unique targeted conservative reaction mode that occurs when both participating molecules include an IS26 is also key. Insights into the detailed mechanism of this reaction will help to shed light on how IS26 contributes to the diversification of the bacterial and plasmid genomes it is found in. These insights will apply more broadly to other members of the IS26 family found in Gram-positive as well as Gram-negative pathogens.