Rhodobacter capsulatus is a nonsulfur purple photosynthetic bacterium that possesses two cbb operons, cbb I and cbb II , encoding enzymes involved in the Calvin-Benson-Bassham (CBB) reductive pentose phosphate pathway of carbon dioxide fixation (24, 25) (Fig. 1). The cbb I operon of R. capsulatus contains cbbL and cbbS, encoding the large and small subunits of form I ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (RubisCO), respectively, as well as two genes, cbbQ and cbbO, of unknown function. Aside from cbbM, which encodes form II RubisCO, the cbb II operon also contains cbbF, encoding fructose-1,6/sedoheptulose-1,7-bisphosphatase; cbbP, encoding phosphoribulokinase; cbbT, encoding transketolase; cbbG, encoding glyceraldehyde 3-phosphate dehydrogenase; cbbA, encoding fructose-1,6-bisphosphate aldolase; cbbM, encoding the large subunit of form II RubisCO; cbbE, encoding ribulose-5-phosphate-3-epimerase; cbbZ, encoding 2-phosphoglycolate phosphatase; and cbbY, encoding an unknown function, as well as three unidentified open reading frames.Divergently transcribed from the cbb I and cbb II operons are cbbR I and cbbR I , respectively, which encode regulators that positively affect transcription of their cognate operons. R. capsulatus cbb I and cbb II are regulated independently, and their expression levels have been shown to vary depending on the growth conditions (13,14,24,25,29,43). The level of cbb I and cbb II expression is maximal under photoautotrophic conditions, when the CBB pathway is used to synthesize organic carbon from CO 2 to support growth and maintain the redox balance of the cell (18, 46). During photoheterotrophic growth (i.e., anaerobic growth conditions in the presence of an organic carbon source), cbb II expression is reduced, while cbb I is not expressed. Under aerobic chemoheterotrophic conditions, when CO 2 fixation is not needed, the level of cbb expression is lowest. Regulatory cross talk between the two operons also occurs, since inactivation of either of the two cbb operons in R. capsulatus leads to a compensatory increase in the expression of the remaining operon (25).While the RegB-RegA two-component regulatory system is also involved in derepressing both cbb I and cbb II operon expression under photoautotrophic growth conditions (43), CbbR I and CbbR II for the most part specifically regulate their cognate operons. However, there is some indication that, in the absence of CbbR II , CbbR I may cross regulate cbb II operon expression under photoheterotrophic conditions (43). In addition, partial expression of the cbb II operon occurs under photoautotrophic conditions in the complete absence of CbbR I

Streptococcus agalactiae, also known as Lancefield Group B Streptococcus (GBS), is typically regarded as a neonatal pathogen; however, several studies have shown that the bacteria are capable of causing invasive diseases in non-pregnant adults as well. The majority of documented cases were from Southeast Asian countries, and the most common genotype found was ST283, which is also known to be able to infect fish. This study sequenced 12 GBS ST283 samples collected from adult patients in Thailand. Together with publicly available sequences, we performed temporo-spatial analysis and estimated population dynamics of the bacteria. Putative drug resistance genes were also identified and characterized, and the drug resistance phenotypes were validated experimentally. The results, together with historical records, draw a detailed picture of the past transmission history of GBS ST283 in Southeast Asia.

A total of 83 Acinetobacter baumannii isolates from patients attending a tertiary care university hospital in Thailand were investigated for their clonal relatedness, antimicrobial susceptibility profiles, and integron carriage. Susceptibility profiles showed that 56 (67%) of these isolates exhibited multiple drug resistance (MDR). Pulsed-field gel electrophoresis (PFGE) showed that 73% of these resistant isolates were clustered into three predominant PFGE types: 6, 7, and 36. This suggested that the high number of isolates exhibiting MDR phenotypes observed in the hospital is, to some extent, due to the spread of these three resistant clones. Class 1 integrase genes were detected in all MDR isolates belonging to PFGE type 6, most MDR isolates belonging to PFGE type 7 and none of the isolates belonging to PFGE type 36. Five different class 1 gene cassette arrays, dfrA1-orfC, bla(IMP-14)-aac6', aacA4- catB8-aadA1, aacC1-orfX-orfX'-aadA1a, and aacC1-orfX-orfX-orfX'-aadA1a, were identified, of which the bla(IMP-14)-aac6' array has only been found in Thai isolates. Two isolates identified in this study carried a class 2 integrase gene with a 2.2 kb cassette array containing aadA1-sat-dfrA1.

Resistance to the last-line antibiotics against invasive Gram-negative bacterial infection is a rising concern in public health. Multidrug resistant (MDR) Acinetobacter baumannii Aci46 can resist colistin and carbapenems with a minimum inhibitory concentration of 512 µg/mL as determined by microdilution method and shows no zone of inhibition by disk diffusion method. These phenotypic characteristics prompted us to further investigate the genotypic characteristics of Aci46. Next generation sequencing was applied in this study to obtain whole genome data. We determined that Aci46 belongs to Pasture ST2 and is phylogenetically clustered with international clone (IC) II as the predominant strain in Thailand. Interestingly, Aci46 is identical to Oxford ST1962 that previously has never been isolated in Thailand. Two plasmids were identified (pAci46a and pAci46b), neither of which harbors any antibiotic resistance genes but pAci46a carries a conjugational system (type 4 secretion system or T4SS). Comparative genomics with other polymyxin and carbapenem-resistant A. baumannii strains (AC30 and R14) identified shared features such as CzcCBA, encoding a cobalt/zinc/cadmium efflux RND transporter, as well as a drug transporter with a possible role in colistin and/or carbapenem resistance in A. baumannii. Single nucleotide polymorphism (SNP) analyses against MDR ACICU strain showed three novel mutations i.e., Glu229Asp, Pro200Leu, and Ala138Thr, in the polymyxin resistance component, PmrB. Overall, this study focused on Aci46 whole genome data analysis, its correlation with antibiotic resistance phenotypes, and the presence of potential virulence associated factors.

The emergence in Southeast Asia of invasive group B Streptococcus (GBS) infections in adults by sequence type (ST) 283 is suggested to be associated with fish consumption. Genotyping of 55 GBS clinical isolates revealed that 33/44 invasive isolates belonged to ST283/capsular polysaccharide type (CPS) III. This included 15/16 isolates recovered from younger adults aged 16–36 years. Seven ST283/CPSIII isolates from the blood, cerebrospinal fluid, or joint fluid were selected by the patient’s age at random to perform interaction studies with intestinal epithelial Caco-2 monolayers. The invasion efficiency profiles from this study classified these isolates into two groups; a higher invasion efficiency group 1 recovered from patients aged between 23 and 36 years, and a lower invasion efficiency group 2 recovered from the elderly and neonate. Intracellular survival tests revealed that only group 1 members could survive inside Caco-2 cells up to 32 h without replication. Additionally, all isolates tested were able to traverse across polarized Caco-2 monolayers. However, the timing of translocation varied among the isolates. These results indicated the potential of GBS invasion via the gastrointestinal tract and showed phenotypic variations in invasiveness, intracellular survival, and translocation efficiency between genetically closely related ST283 isolates infecting young adults and those infecting the elderly.