- Volume 71, Issue 6, 2022

Candida auris is a recently emerged multidrug-resistant fungal pathogen that causes life-threatening infections to the human population worldwide. Recent rampant outbreaks of C. auris in coronavirus disease 2019 (COVID-19) patients, together with outbreaks in over 45 countries, highlight its threat to patients and healthcare economies. Unlike other pathogenic Candida species, C. auris is capable of surviving in abiotic surfaces of healthcare facilities for prolonged periods, leading to increased risk of transmission within nosocomial settings. C. auris is resistant to multiple classes of antifungal agents, forms dry biofilms and transmits independently to regional epicentres, making its eradication from nosocomial environment arduous. The lack of strategies for environmental decontamination of C. auris from nosocomial settings is evident from the generic guidance and recommendations provided by leading global healthcare bodies. Therefore, this minireview discusses the current guidelines for environmental decontamination of C. auris and compounds and strategies currently under investigation for potential future use. While established guidelines recommend the use of products mainly consisting of sodium hypochlorite and hydrogen peroxide, initial works have been reported on the promising anti-C. auris properties of various other compounds and some biocompatible alternatives. Further validation of these approaches, coupled up with environmentally friendly decontamination protocols, are warranted to achieve superior elimination of C. auris from healthcare settings.

Introduction. The emergence of resistance to fluconazole in Candida albicans has made the clinical treatment of this microbe difficult. A potential strategy to address this problem involves diminishing fungal resistance to antimicrobial drugs.

Hypothesis. Berberine hydrochloride (BH), the primary active ingredient of the traditional Chinese medicine (TCM) Coptis, inhibits the growth of fluconazole-resistant C. albicans through its action on the high-osmolarity glycerol mitogen-activated protein kinase (HOG-MAPK) pathway.

Aim. To examine the effect of BH on the HOG-MAPK pathway to assess the potential molecular mechanism by which BH inhibits fluconazole-resistant C. albicans.

Methodology. The minimum inhibitory concentration (MIC) of BH to fluconazole-resistant C. albicans was measured using the broth microdilution approach to determine the concentration of effective drug intervention. Changes in physiological functions regulated by the HOG-MAPK pathway in response to BH treatment were measured, as well as the expression of central signalling pathway genes and key downstream factors by qRT-PCR and Western blotting, respectively.

Results. BH inhibited fluconazole-resistant C. albicans and the sensitivity to fluconazole increased after BH treatment. At a concentration of 256 and 64 μg ml−1 BH may affect key downstream factors that regulate several physiological functions of C. albicans by upregulating the core genes expression of SLN1, SSK2, HOG1, and PBS2 in the HOG-MAPK pathway. Upregulation of GPD1, the key gene for glycerol synthesis, increased cell osmotic pressure. BH treatment increased the accumulation of reactive oxygen species by upregulating the expression of the key respiratory metabolism gene ATP11 and downregulating the expression of the superoxide dismutase gene SOD2. Furthermore, downregulation of mycelial-specific HWP1 hindered the morphological transformation of C. albicans and inhibition of the chitin synthase gene CHS3 and the β-(1,3) glucan synthase gene GSC1 impaired cytoderm integrity.

Conclusion. BH affects multiple target genes in diminishing the resistance of C. albicans strains to fluconazole. This effect may be related to the action of BH on the HOG-MAPK pathway.

Tigecycline is an important rescue antibiotic for many bacterial infections. In Mycobacteroides abscessus , tigecycline resistance has been associated with dysregulated stress response caused by aberrations in the interaction of the SigH and RshA factors. In this study, two tigecycline-resistant mutants of M. abscessus (CL5A and CL6A) with mutations in the rshA gene were studied using gene complementation, RT-qPCR and the bacterial adenylate cyclase two-hybrid (BACTH) system. The results supported the premise that mutations in the rshA interrupt the RshA–SigH interaction to cause the overexpression of the sigH gene that leads to tigecycline resistance or reduced susceptibility.

Introduction. Nontuberculous mycobacteria (NTM) infections are increasing worldwide and are relatively resistant to many of the first- and second-line drugs to treat tuberculosis. Macrolide antibiotics, such as clarithromycin and azithromycin, are the key drugs for treating NTM infections. Fidaxomicin is a macrolide antibiotic that is widely used in treating Clostridium difficle (C.difficile) infections, and has high in vitro activity against Mycobacterium tuberculosis especially multidrug-resistant tuberculosis (MDR-TB) and has no cross-resistance with rifampicin.

Hypothesis. Fidaxomicin may have in vitro activity against NTM strains.

Aim. To find that whether the macrolide antibiotic fidaxomicin has in vitro activity against NTM strains.

Methodology. Fidaxomicin used in this study was firstly tested on C. difficile reference strains and has shown to be effective and workable. And then 28 rapidly growing mycobacteria (RGM), 12 slowly growing mycobacteria (SGM) reference strains and 103 NTM clinical isolates were tested by the microplate-based AlamarBlue assay (MABA) method to determine the MICs. Fidaxomicin, rifampicin and clarithromycin were tested against M. abcessus complex subspecies 14 M . abscessus and 5 M . massiliense strains for inducible resistance determination.

Results. In total, 21 out of 28 RGM and 9 of 12 SGM reference strains have the MICs of fidaxomicin at or below 1 µg ml−1. Fidaxomicin also showed low MIC values for some clinical isolates including M. abscessus complex, M. avium complex, M. fortuitum , M. kansasii and M. parascrofulaceum . Fidaxomicin also has no inducible macrolide resistance in M. abscessus complex in comparison with clarithromycin.

Conclusion. Fidaxomicin has high in vitro activity against most of the NTM reference strains and some prevalent NTM clinical isolates. This promising finding warrants further investigation on the actions of fidaxomicn in vivo and as a potential antibiotic for NTM treatment.

Introduction. Aminoglycoside antibiotics are widely used to treat infections of Pseudomonas aeruginosa . The MexXY-OprM efflux pump is an important contributor to aminoglycoside tolerance in P. aeruginosa reference strains and expression of the mexXY genes is repressed by the MexZ repressor protein. Direct investigation of the role of this efflux pump in clinical isolates is relatively limited.

Hypothesis. The contribution of MexXY-OprM to P. aeruginosa aminoglycoside resistance is isolate-specific.

Aim. To quantify the role of MexXY-OprM and its repressor, MexZ, in clinical isolates of P. aeruginosa.

Methodology. The mexXY genes were deleted from ten clinical isolates of P. aeruginosa , and the mexZ gene from nine isolates. Antimicrobial susceptibility testing was carried out for commonly used antipseudomonal drugs on the engineered mutants and the isogenic wild-type isolates. RT-qPCR was used to measure expression of the mexX gene.

Results. All but one of the mexXY mutants were more susceptible to the clinically used aminoglycosides tobramycin, gentamicin and amikacin but the degree to which susceptibility increased varied greatly between isolates. The mexXY mutants were also more susceptible to a fluoroquinolone, ciprofloxacin. In three isolates with functional MexZ, deletion of mexZ increased expression of mexXY and aminoglycoside tolerance. Conversely, deleting mexZ from six clinical isolates with mexZ sequence variants had little or no effect on expression of mexXY or on aminoglycoside susceptibility, consistent with the variants abolishing MexZ function. Genome analysis showed that over 50 % of 619 clinical isolates had sequence variants predicted to reduce the affinity of MexZ for DNA, likely increasing mexXY expression and hence efflux of aminoglycosides.

Conclusion. Our findings show that the interplay between MexXY, MexZ and the level of mexXY expression plays an important role in aminoglycoside resistance in clinical isolates of P. aeruginosa but the magnitude of the contribution of this efflux pump to resistance is isolate-specific.

Carbapenemase-producing Enterobacterales (CPE) pose one of the most serious antimicrobial resistance threats to public health worldwide. The outcome of CPE infection differs depending on the resistance mechanism. Therefore, rapid detection of CPE infection is essential for optimizing patient management. The carbapenem inactivation method (CIM) and modified CIM (mCIM) are standard methods for detecting CPE, but they usually require 24 h to generate results.

Recently, an immunochromatographic assay, NG-Test CARBA 5, has become commercially available. It detects the five most common carbapenemase producers (KPC, IMP, NDM, VIM, and OXA-48) rapidly and accurately.

We aimed to evaluate the diagnostic accuracy of NG-Test CARBA 5 for detecting carbapenemase-producing Gram-negative bacilli (CPGNB).

We used 116 carbapenemase-producing strains and 48 non-carbapenemase-producing strains. Of the 116 carbapenemase-producing strains, 107 harboured genes for at least one of the five most common carbapenemases, KPC, IMP, NDM, VIM, and OXA-48-like. Forty-eight non-carbapenemase-producing strains, including carbapenem-resistant Enterobacterales , harboured genes for extended-spectrum β-lactamases (CTX-M groups [n=25] and SHV groups [n=2]) or plasmid-mediated AmpC β-lactamases (DHA [n=3], CMY-2 [n=2], and CFE-1 [n=1]). Antimicrobial susceptibility was tested using the agar dilution method, according to the Clinical and Laboratory Standards Institute guidelines.

Of the 116 carbapenemase-producing strains, 79 were resistant to at least meropenem or imipenem. The sensitivity and specificity of the NG-Test CARBA 5 for the strains were 99.1 % (106 strains positive for 107 strains of the five most common carbapenemase producers) and 100 % (60 strains negative for other types of CPGNB [n=10] and non-CPGNB strains [n=48]), respectively. The carbapenemase-producing strain with a false-negative result produced IMP-66.

The NG-Test CARBA 5 had high sensitivity and specificity for detecting carbapenemase-producing strains.

Background. Clostridioides difficile is a spore-forming pathogen responsible for antibiotic-associated diarrhoea. In the USA high incidence of C. difficile infection (CDI) in clinical environments has led to interest in C. difficile spore transmission.

Hypothesis. Single use hospital surgical gown ties act as a reservoir for C. difficile spores.

Aim. This study sought to examine whether single-use hospital surgical gown ties used in surgery, from an acute healthcare facility, harboured C. difficile spores.

Methodology. Used surgical gowns ties worn by clinicians in the healthcare facility were examined for C. difficile spore presence via spread plate and anaerobic culture. The colonies isolated from each gown tie were subcultured on C. difficile selective agar for phenotypic confirmation. Presumptive C. difficile colonies were examined using C. difficile Quik Check Complete, 16–23S PCR Ribotyping and MALDI-TOF analysis.

Results. In total 17 suspected C. difficile colonies were isolated from 15 gown ties via culture. C. difficile Quik Check Complete found two isolates as possible C. difficile . MALDI-TOF and PCR Ribotyping confirmed one isolate as C. difficile PCR ribotype 027 associated with clinical outbreaks.

Discussion. Our study revealed the presence of hypervirulent C. difficile ribotype 027 spores on single-use gown ties. This highlights the potential of gown ties as a vector of spore transmission across clinical environments, especially when gowns are not worn appropriately.

Conclusions. Appropriate compliance to infection control procedures by healthcare workers is essential to prevent spore dissemination across clinical facilities and reduce CDI rates.

The world has experienced several waves of SARS-CoV-2 variants of concern (VoCs) throughout the COVID-19 pandemic since the first cases in December 2019. The Omicron VoC has increased transmission, compared to its predecessors, and can present with sore throat and other cold-like symptoms. Given the predominance of throat symptoms, and previous work demonstrating better sensitivity using antigen-based rapid detection tests when a throat swab is included in the standard nasal sampling, this quality improvement project sought to ensure ongoing suitability of both combined oropharyngeal/nares (OPN) and nasopharyngeal (NP) swab sampling used throughout the pandemic. Consenting participants meeting Public Health testing criteria (mostly symptomatic or a close contact of a known case) were enrolled, and paired NP and OPN swabs were subjected to nucleic acid amplification testing (NAAT). Comparing paired specimens from 392 participants sensitivity of NP swabs was 89.1 % (95 % CI, 78.8–94.9), and that of OPN was 98.4 % (95 % CI: 90.9->99.9) (P-value 0.052). This project demonstrated that both NP and combined OPN swabs detected the Omicron variant with similar sensitivity by NAAT, supporting the continued use of either swab collection for SARS-CoV-2 molecular detection.

Microorganisms produce a wide variety of volatile organic compounds (VOCs) as products of their metabolism and some of them can be specific VOCs linked to the microorganism's identity, which have proved to be helpful for the diagnosis of infection via odour fingerprinting. The aim of this study was to determine the VOCs produced and consumed to characterize the volatile metabolism of seven isolates of different clonal complexes (CCs) of Listeria monocytogenes . For this purpose, dichloromethane extracts from the thioglycolate broth medium were analysed by gas chromatography coupled to mass spectrometry (GC/MS). Also, multivariate analyses were applied to the data obtained. Results showed that all the isolates of L. monocytogenes produced de novo isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-(methylthio)−1-propanol, acetic acid, isobutyric acid, butanoic acid, and isovaleric acid. Significant differences were found among isolates for the production amount of these volatiles, which allowed their differentiation. Thus, CC4 (ST-219/CT-3650) and CC87 (ST-87/CT-4557) showed an active volatile compounds metabolism with high consumption nitrogen and sulphur compounds and production of alcohols and acids, and CC8 (ST-8/CT-8813) and CC3 (ST-3/CT-8722) presented a less active volatile metabolism. Moreover, within the VOCs determined, huge differences were found in the production of butanol among the seven isolates analysed, being probably a good biomarker to discriminate among isolates belonging to different CCs. Hence, the analysis of volatile profile generated by the growth of L. monocytogenes in vitro could be a useful tool to differentiate among CCs isolates.

Introduction. India is home to the most significant number of tuberculosis (TB) cases around the globe. The COVID-19 crisis has massively affected TB healthcare services in the country.

Hypothesis/Gap Statement. Are we sufficiently equipped to fight against TB during emergencies?

Aim. Our study aims to provide a true insight into the disruption of TB care during the pandemic period at a tertiary care hospital in India.

Methods. A retrospective observational cohort analysis was conducted on 6491 patients who accessed the TB diagnostics at the tertiary care hospital during the study period, i.e. the COVID-19 pandemic period (March 2020 to March 2021) compared with 14 665 in the control period (March 2019 to Feb 2020).

Results. Out of the total tested, 3136 patients were notified as new TB cases in the study period than 4370 in the control period (P-value=0.0000001), i.e. 28.23 % decline in notifications. A drastic decline of 69 % in notifications was observed during the lock down months in the pandemic period, i.e. March to June 2020 (P-value=0.00001). A reduction of 44 % in treatment accession by 3690 TB patients in the control period compared with 2062 in the study period (P-value=0.0000001) was noted. Lost to follow-up patients increased by 65 % from 460 in the control period to 760 in the study period (P-value=0.0000001). Also, an increased death rate by 43 % from control to study period (P-value=0.0000001) was reported.

Conclusion. There is an urgent need to maintain the continuity of essential TB services to reduce the rising burden in vulnerable populations. The need of the hour is to undertake novel strategies for tuberculosis control to combat such emergencies in the coming future.