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

Bacteriophage show promise for the treatment of infections that resist all therapeutically suitable antibiotics. Many tail-spike depolymerases encoded by phage that are able to degrade 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.

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.

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.

Characterisation of an early South African multiply antibiotic-resistant global clone 1 Acinetobacter baumannii isolate.

Objectives: The aim of this study was to characterise an early clinical multiply antibiotic resistant Acinetobacter baumannii global clone 1 (GC1) isolate from Africa.

Methods: The draft genome sequence was determined using short-read (Illumina MiSeq) sequence data and compared to other early GC1 isolates. Resistance genes and other features were identified using various bioinformatics tools.

Can SGI1 family integrative mobilizable elements overcome entry exclusion exerted by IncA and IncC plasmids on IncC plasmids?

Though IncC and IncA plasmids are compatible, they exert high level exclusion on one another. Here, the question of whether the presence of an SGI1 family element in the donor can overcome the exclusion of an IncC plasmid exerted by an IncC or IncA plasmid in the recipient was investigated. The transfer of the integrative mobilizable element SGI1 and its many variant forms into a new host is dependent on transfer machinery supplied by IncC or IncA plasmids.

Extensively resistant Acinetobacter baumannii isolate RCH52 carries several resistance genes derived from an IncC plasmid.

Objectives: To identify the origins of resistance in a sporadic extensively resistant Acinetobacter baumannii isolate.

Methods: The complete genome of RCH52 was determined by combining available Illumina short reads with MinION (Oxford Nanopore) long reads using Unicycler. Bioinformatic searches were used to identify features of interest.

dfrA trimethoprim resistance genes found in Gram-negative bacteria: compilation and unambiguous numbering.

To track the spread of antibiotic resistance genes, accurate identification of individual genes is essential. Acquired trimethoprim resistance genes encoding trimethoprim-insensitive homologues of the sensitive dihydrofolate reductases encoded by the folA genes of bacteria are increasingly found in genome sequences. However, naming and numbering in publicly available records (journal publications or entries in the GenBank non-redundant DNA database) has not always been unambiguous.

An outbreak of multiply antibiotic-resistant ST49:ST128:KL11:OCL8 Acinetobacter baumannii isolates at a Sydney hospital.

Objectives: To understand the acquisition of resistance genes by a non-GC1, non-GC2 Acinetobacter baumannii strain responsible for a 4 year outbreak at a Sydney hospital.

Methods: Representative isolates were screened for resistance to antibiotics. Three were subjected to WGS using Illumina HiSeq.

Novel trimethoprim resistance gene, dfrA35, in IncC plasmids from Australia.

Background: In Gram-negative bacteria, over 30 different genes are known to encode a trimethoprim-insensitive dihydrofolate reductase that confers resistance to trimethoprim.

Objectives: To determine whether a gene encoding a putative dihydrofolate reductase found in type 2 IncC plasmids isolated between 2002 and 2013 in healthcare facilities in Melbourne, Australia, confers trimethoprim resistance.

Methods: Conjugation was used to transfer plasmids into a laboratory Escherichia coli.

Evolution and typing of IncC plasmids contributing to antibiotic resistance in Gram-negative bacteria.

The large, broad host range IncC plasmids are important contributors to the spread of key antibiotic resistance genes and over 200 complete sequences of IncC plasmids have been reported. To track the spread of these plasmids accurate typing to identify the closest relatives is needed. However, typing can be complicated by the high variability in resistance gene content and various typing methods that rely on features of the conserved backbone have been developed.

Compatibility and entry exclusion of IncA and IncC plasmids revisited: IncA and IncC plasmids are compatible.

In an early study, IncA and IncC plasmids that were reported to be compatible were grouped as the "A-C complex" based on similarities and on strong entry exclusion. However, recently, the term IncA/C has been used frequently to describe plasmids belonging to both of these two groups. Granted that the supporting data was not included in the original reports and that the consensus iteron sequences have since been shown to be essentially identical, we have addressed the question again.

Destabilization of IncA and IncC plasmids by SGI1 and SGI2 type Salmonella genomic islands.

Both the Salmonella genomic islands (SGI) and the conjugative IncC plasmids are known to contribute substantially to the acquisition of resistance to multiple antibiotics, and plasmids in the A/C group are known to mobilize the Salmonella genomic island SGI1, which also carries multiple antibiotic resistance genes. Plasmid pRMH760 (IncC; A/C) was shown to mobilize SGI1 variants SGI1-I, SGI1-F, SGI1-K and SGI2 from Salmonella enterica to Escherichia coli where it was integrated at the preferred location, at the end of the trmE (thdF) gene. The plasmid was transferred at a similar frequency.

A large conjugative Acinetobacter baumannii plasmid carrying the sul2 sulphonamide and strAB streptomycin resistance genes.

Acinetobacter baumannii is an important nosocomial pathogen that often complicates treatment because of its high level of resistance to antibiotics. Though plasmids can potentially introduce various genes into bacterial strains, compared to other Gram-negative bacteria, information about the unique A. baumannii plasmid repertoire is limited.