X-AMR, a pop-up journal

Purpose. Non-albicans Candida species have emerged as fungal pathogens that cause invasive infections, with many of these species displaying resistance to commonly used antifungal agents. This study was confined to studying the characteristics of clinical isolates of the C. rugosa complex and C. pararugosa species.

Methodology. Seven isolates of the C. rugosa complex and one isolate of C. pararugosa were obtained from two tertiary referral hospitals in Malaysia. Their antifungal susceptibilities, biofilm, proteinase, phospholipase, esterase and haemolysin activities were characterized. Biofilms were quantified using crystal violet (CV) and tetrazolium (XTT) reduction assays at 1.5, 6, 18, 24, 48 and 72 h.

Results/Key findings. The E-test antifungal tests showed that both species have elevated MICs compared to C. albicans and C. tropicalis. The highest biomass was observed in one of the C. rugosa isolates (0.237), followed by C. pararugosa (0.206) at 18 h of incubation. However, the highest bioactivity was observed in the C. rugosa ATCC 10571 strain at 24 h (0.075), followed by C. pararugosa at 48 h (0.048) and the same C. rugosa strain at 24 h (0.046), with P<0.05. All isolates exhibited high proteinase activity (+++) whereas six isolates showed very strong esterase activity (++++). All the isolates were alpha haemolytic producers. None of the isolates exhibited phospholipase activity.

Conclusion. Elevated MICs were shown for the C. rugosa complex and C. pararugosa for commonly used antifungal drugs. Further studies to identify virulence genes involved in the pathogenesis and genes that confer reduced drug susceptibility in these species are proposed.

Purpose. This study was aimed at investigating the occurrence and genetic mechanisms of resistance to ciprofloxacin, tetracycline and erythromycin in clinical isolates of Campylobacter jejuni recovered from human cases of acute gastroenteritis in Turkey.

Methodology. MIC values of each antibiotic were determined with the epsilometer test (E-test). Resistance genes/mutations were first screened by PCR and analysed by subsequent DNA sequencing.

Results. From a total of 152 C. jejuni isolates tested, 113 (74.3%), 38 (25%) and 9 (5.9%) were found to be resistant to ciprofloxacin, tetracycline and erythromycin, respectively. Sequence analysis of ciprofloxacin-resistant isolates showed that all resistant strains (n=113) carried Thr-86-Ile substition in the gyrA gene, which is the most frequently observed mutation in fluoroquinolone-resistant Campylobacter . All of the tetracycline-resistant isolates (n=38) carried the tetO gene. All of the erythromycin-resistant isolates (n=9) harboured the point mutation A2075G in the 23S rRNA gene, which is the most common mutation conferring macrolide resistance in C. jejuni .

Conclusion. The phenotypic susceptibility testing results were found to agree well with those obtained by genetic detection methods for the C. jejuni isolates tested. The findings of this study showed a very high level of resistance to ciprofloxacin and to a lesser extent to tetracycline while resistance to erythromycin remained at a low level. Thus, erythromycin may be considered as the first choice for treatment of Campylobacter infections in this geographical region when indicated.

Purpose. Antimicrobial resistance (AMR) profiles of 754 strains of Shigella dysenteriae isolated between 2004 and 2017 from UK travellers reporting symptoms of gastrointestinal (GI) disease were reviewed to look for evidence of emerging AMR associated with travellers’ diarrhoea.

Methodology. A travel history was provided for 72.7 % (548/754) of cases, of which 90.9 % (498/548) reported travel outside the UK within 7 days of onset of symptoms, and 9.1 % (50/498) reported no travel in that time frame. During the course of this study, whole genome sequencing (WGS) was implemented for GI disease surveillance, and we compared phenotypic AMR profiles with those derived from WGS data (n=133).

Results/Key findings. The phenotypic and genotypic AMR results correlated well, with 90.1 % (121/133) isolates having concordant results to 10 classes of antimicrobials. Resistance to the first-line drugs commonly used in the treatment of shigellosis was observed throughout the study (ampicillin, 54.1%; chloramphenicol, 33.7 %; sulphonamides, 76.0 %; trimethoprim, 80.0%). Between 2004 and 2017, resistance to all classes of antimicrobials (except the phenicols) increased. The proportion of isolates exhibiting reduced susceptibility to ciprofloxacin increased from 3.8 % in 2004 to 75.7 % in 2017, and this was significantly associated with cases reporting travel to Asia compared to Africa (P<0.001). Of the 201 sequenced isolates, 3.0 % (20/201) had either bla _CTX-M-15 or bla _CMY-4.

Conclusions. Increasing MDR, along with resistance to the fluroquinolones and the third generation cephalosporins, in Shigella dysenteriae causing travellers’ diarrhoea provides further evidence for the need to regulatethe use of antimicrobial agents and continuous monitoring of emerging AMR.

Although tuberculosis treatment is dependent on drug-susceptibility testing (DST) and molecular drug-resistance detection, treatment failure and relapse remain a challenge. This could be partially due to the emergence of antibiotic-tolerant dormant mycobacteria, where host lipids have been shown to play an important role. This study evaluated the susceptibility of Mycobacterium tuberculosis to two antibiotic combinations – rifampicin, moxifloxacin, amikacin and metronidazole (RIF-MXF-AMK-MTZ), and rifampicin, moxifloxacin, amikacin and pretomanid (RIF-MXF-AMK-PA) – in a lipid-rich dormancy model. Although their effectiveness in in vitro cultures with dextrose as a carbon source has been proved, we observed that none of the antibiotic mixtures were bactericidal in the presence of lipids. The presence of lipids may confer tolerance to M. tuberculosis against the mixture of antibiotics tested and such tolerance could be even higher during the dormant stages. The implementation of lipids in DST on clinical isolates could potentially lead to a better treatment strategy.

Aeromonas salmonicida subsp. salmonicida is a fish pathogen known to have a rich plasmidome. In the present study, we discovered an isolate of this bacterium bearing an additional unidentified small plasmid. After having sequenced the DNA of that isolate by next-generation sequencing, it appeared that the new small plasmid is a ColE1-type replicon plasmid, named here pAsa7. This plasmid bears a functional chloramphenicol-acetyltransferase-encoding gene (cat-pAsa7) previously unknown in A. salmonicida and responsible for resistance to chloramphenicol. A comparison of pAsa7 with pAsa2, the only known ColE1-type replicon plasmid usually found in A. salmonicida subsp. salmonicida, revealed that even if both plasmids share a high structural similarity, it is still unclear if pAsa7 is a derivative of pAsa2 since they showed several mutations at the nucleotide level. Transcriptomic analysis revealed that the cat-pAsa4 gene, another chloramphenicol-acetyltransferase-encoding gene, found on the large plasmid pAsa4, was significantly more transcribed than cat-pAsa7. This was correlated with a higher chloramphenicol resistance for isolates bearing pAsa4 compared with the one having pAsa7. Finally, a phylogenetic analysis showed that both CAT-pAsa4 and CAT-pAsa7 proteins were in different clusters. The clustering was supported by the identity of residues involved in the catalytic site. In addition, to give a better understanding of the large drug-resistance panel of A. salmonicida, this study reinforces the hypothesis that A. salmonicida subsp. salmonicida is a considerable reservoir for mobile genetic elements such as plasmids.