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Purpose . To highlight the clinical significance of carbapenem-resistant Klebsiella pneumoniae (CRKP) rectal colonization by examining the risk factors for CRKP rectal colonization and subsequent bloodstream infection (BSI) in critically ill patients.

Methodology . Prospective study of CRKP rectal colonization in an intensive care unit (ICU) during a 39-month period. CRKP strains isolated from both the blood cultures and corresponding rectal specimens (n=96) of patients were screened by PCR for the presence of antibiotic resistance-associated genes. Molecular analyses were conducted to investigate the clonal relatedness of CRKP strains from the rectal and blood specimens.

Results . Among the 498 patients, 226 were rectally colonized by CRKP, 48 of whom developed a CRKP BSI. The median time from hospital admission to the detection of CRKP rectal colonization was 8 days, while the median time from colonization to BSI was 4 days. The duration of ICU stay, patient/nurse ratio and prior use of antianaerobic antimicrobials were associated with CRKP rectal colonization. No specific factor was associated with BSIs in the colonized patients. The bla _KPC-2 gene was detected in all 96 strains, which were all classified as sequence type ST-258. Representative pairs (n=48) of CRKP strains colonizing and infecting the same patient shared the same pulsotype.

Conclusion . Our results indicate that hospitalized patients become infected with their colonizing strains, supporting the strong association between colonization and BSI. Limiting antianaerobic antimicrobial administration, reducing the duration of ICU stay and maintaining a low patient/nurse ratio are possible strategies to restrict rectal CRKP colonization in ICUs.

Several species of Aeromonas produce the enzyme CphA metallo-β-lactamase. This study describes an isolate of Aeromonas hydrophila harbouring an acquired gene encoding the carbapenemase GES-24. This isolate was obtained from an inpatient in Okinawa, Japan, with no apparent record of travelling overseas. The minimum inhibitory concentrations of carbapenems against this isolate were 8 µg ml−1 for imipenem and 16 µg ml−1 for meropenem. Recombinant GES-24 hydrolyzed all of the tested β-lactams, including imipenem and meropenem. The genomic environment surrounding bla _GES-24 was intI1-bla _GES-24 -aac(6′)-IIc-qacEdelta1-sulI-orfX-tetR-tetE. This is the first report of A. hydrophila producing a GES-type carbapenemase.

Bacterial biofilms can cause serious health care complications associated with increased morbidity and mortality. There is an urge to discover and develop new biofilm inhibitors from natural products or by modifying natural compounds or understanding the modes of action of existing compounds. Cinnamaldehyde (CAD), one of the major components of cinnamon oil, has been demonstrated to act as an antimicrobial agent against a number of Gram-negative and Gram-positive pathogens, including Pseudomonas aeruginosa, Helicobacter pylori and Listeria monocytogenes. Despite the mechanism of action of CAD against the model organism P. aeruginosa being undefined, based on its antimicrobial properties, we hypothesized that it may disrupt preformed biofilms of P. aeruginosa. The minimum inhibitory concentration (MIC) of CAD for planktonic P. aeruginosa was determined to be 11.8 mM. Membrane depolarization assays demonstrated disruption of the transmembrane potential of P. aeruginosa. CAD at 5.9 mM (0.5 MIC) disrupted preformed biofilms by 75.6 % and 3 mM CAD (0.25 MIC) reduced the intracellular concentrations of the secondary messenger, bis-(3′–5′)-cyclic dimeric guanosine monophosphate (c-di-GMP), which controls P. aeruginosa biofilm formation. The swarming motility of P. aeruginosa was also reduced by CAD in a concentration-dependent manner. Collectively, these findings show that sub-MICs of CAD can disrupt biofilms and other surface colonization phenotypes through the modulation of intracellular signalling processes.

Phytoplasmas are plant-pathogenic bacteria that infect many important crops and cause serious economic losses worldwide. However, owing to an inability to culture phytoplasmas, screening of antimicrobials on media is difficult. The only antimicrobials being used to control phytoplasmas are tetracycline-class antibiotics. In this study, we developed an accurate and efficient screening method to evaluate the effects of antimicrobials using an in vitro plant–phytoplasma co-culture system. We tested 40 antimicrobials, in addition to tetracycline, and four of these (doxycycline, chloramphenicol, thiamphenicol and rifampicin) decreased the accumulation of ‘Candidatus (Ca.) Phytoplasma asteris'. The phytoplasma was eliminated from infected plants by the application of both tetracycline and rifampicin. We also compared nucleotide sequences of rRNAs and amino acid sequences of proteins targeted by antimicrobials between phytoplasmas and other bacteria. Since antimicrobial target sequences were conserved among various phytoplasma species, the antimicrobials that decreased accumulation of ‘Ca. P. asteris' may also have been effective against other phytoplasma species. These approaches will provide new strategies for phytoplasma disease management.

Purpose. Ceftriaxone is the drug of choice for typhoid fever and the emergence of resistant Salmonella Typhi raises major concerns for treatment. There are an increasing number of sporadic reports of ceftriaxone-resistant S. Typhi and limiting the risk of treatment failure in the patient and outbreaks in the community must be prioritized. This study describes the use of whole genome sequencing to guide outbreak identification and case management.

Methodology. An isolate of ceftriaxone-resistant S. Typhi from the blood of a child taken in 2000 at the Popular Diagnostic Center, Dhaka, Bangladesh was subjected to whole genome sequencing, using an Illumina NextSeq 500 and analysis using Geneious software.

Results/Key findings. Comparison with other ceftriaxone-resistant S. Typhi revealed an isolate from the Democratic Republic of the Congo in 2015 as the closest relative but no evidence of an outbreak. A plasmid belonging to incompatibility group I1 (IncI1-ST31) which included bla CTX-M-15 (ceftriaxone resistance) associated with ISEcp-1 was identified. High similarity (90 %) was seen with pS115, an IncI1 plasmid from S. Enteritidis, and with pESBL-EA11, an incI1 plasmid from E. coli (99 %) showing that S. Typhi has access to ceftriaxone resistance through the acquisition of common plasmids.

Conclusions. The transmission of ceftriaxone resistance from E. coli to S. Typhi is of concern because of clinical resistance to ceftriaxone, the main stay of typhoid treatment. Whole genome sequencing, albeit several years after the isolation, demonstrated the success of containment but clinical trials with alternative agents are urgently required.

Purpose. A selective chromogenic culture medium for the laboratory isolation and differentiation of colistin resistant A cinetobacter, Pseudomonas, Stenotrophomonas and E nterobacteriaceae spp. (CHROMagar COL-APSE) was developed, evaluated and compared to an existing selective bacterial culture medium (SuperPolymyxin).

Methodology. The medium was challenged with 84 isolates, including polymyxin B (POL B)-susceptible and -resistant type strains and colistin (COL)-resistant organisms recovered from human and animal samples. Susceptibility to COL and POL B was determined by agar dilution and broth microtitre dilution. The lower limit for the detection of COL-resistant organisms was also calculated for both CHROMagar COL-APSE and SuperPolymyxin media. The ability to isolate and correctly differentiate COL-resistant organisms within mixed cultures was also assessed and compared using both media.

Results. Using CHROMagar COL-APSE, Gram-negative pathogens (n=71) with intrinsic (n=8) or acquired COL (n=63) resistance were recovered with 100 % specificity down to the lower limit of detection of 101 colony-forming units (c.f.u.). The growth on SuperPolymyxin was similar, but notably weaker for COL-resistant non-fermentative bacteria (Acinetobacter, Pseudomonas and Stenotrophomonas). CHROMagar COL-APSE was also more sensitive in supporting the growth of Enterobacteriaceae with COL resistance associated with the carriage of mcr-1.

Conclusion. CHROMagar COL-APSE is a sensitive and specific medium for the growth of COL-resistant bacterial pathogens. Due to the low limit of detection (101 c.f.u.), it may be useful as a primary isolation medium in the surveillance and recovery of COL-resistant bacteria from complex human, veterinary and environmental samples, especially those with plasmid-mediated MCR-1 or novel mechanisms of polymyxin resistance.

Non-tuberculous mycobacteria (NTM) infections are increasingly being reported worldwide. They are a major concern for healthcare professionals for multiple reasons, ranging from the intrinsic resistance of NTM to most conventionally utilized antimicrobials to inharmonious diagnostic criteria utilized for evaluation of NTM-infected patients, leading to high morbidity. In this review, we highlight the paucity of drugs having potent anti-NTM activity amongst the new antimicrobials currently under various stages of development for anti-tubercular activity and issue a call for the establishment of a concerted dedicated drug discovery pipeline targeting NTM.