Phenotypic and genotypic evaluation of adherence and biofilm development in Candida albicans respiratory tract isolates from hospitalized patients

Snapshot of resistance and virulence features in ESCAPE strains frequently isolated from surgical wound infections in a Romanian hospital

Background: The aim of this study was to investigate the phenotypic features (adherence, biofilm formation, virulence, antibiotic susceptibility) and the genetic background of antibiotic resistance in nosocomial ESCAPE strains consecutively isolated from surgical wound infections in hospitalized patients.

Methods: 86 bacterial strains consecutively isolated from various wound infections were analysed by their antibiotic resistance (antibiotic susceptibility testing and PCR for certain antibiotic resistance genes), virulence, biofilm formation and cellular adherence.

Results: The bacterial isolates were identified as: Enterobacterales (n = 39) including Escherichia coli (n = 9), Klebsiella pneumoniae (n = 14) Proteus mirabilis (n = 7), followed by Staphylococcus aureus (n = 26) and Enterococcus faecalis (n = 20). Compared to other isolates, S. aureus strains exhibited the highest capacity to produce soluble virulence factors and to develop biofilms in vitro, with significant differences between methicillin resistant and methicillin susceptible isolates. Among enterobacterial isolates, K. pneumoniae strains expressed the highest capacity to develop biofilms. The assessment of bacterial adherence to HeLa cells revealed that all bacterial strains adhered to the cellular substrata, showing various adherence patterns. E. faecalis strains exhibited a low soluble virulence factors profile, a lower capacity to adhere to epithelial cells and to develop biofilms.

Conclusions: The present study could contribute to the understanding of the pathology of infected wounds, depending on the etio-logical agents, providing data with positive impact on the therapeutic management of surgical wounds infections.

Characterization of virulence factors, antifungal resistance with ERG-11 gene among Candida species isolated from pulmonary samples

BACKGROUND

Candida is a part of the normal oropharyngeal flora and the upper respiratory tract. Candida albicans(C. albicans), is the predominant species causing respiratory tract infections associated with pneumonia. Resistance to azole antifungal agents among the C. albicans may be due to alteration of the target enzymes, which are encoded in ERG11 gene. The biofilm formation may also be a cause to antifungal resistance.

MATERIALS AND METHODS

This study was conducted at Chettinad Hospital and Research Institute. Samples were collected from June 2018-June 2019, for a period of 1 year. After species confirmation, virulence factor among the Candida species were identified by hemolysis test, coagulase test and biofilm formation. Genotypic confirmation of C. albicans and their azole resistance due to ERG 11 gene were done using multiplex PCR.

RESULTS

In our study, 31 (55%) C. albicans, 8 (14%) Candida glabrata(C. glabrata) and 10 (17%) Candida tropicalis(C. tropicalis), three Aspergillus flavus(A. flavus), two Aspergillus fumigatous (A. fumigatous), one Aspergillus niger (A. niger) and one Mucor species were isolated. In C. albicans, 31 were positive for Germ tube and Chalmydospore formation. Six of candida species were isolated along with bacterial co infection. Among the Candida isolates, 17 (55%) C. albicans strains were strongly biofilm positive and 14(45%) were negative. The susceptibility pattern of (n = 31) C. albicans were as follows: fluconazole (21(68%) S, 10(32%) R), voriconazole (22(71%)S),9(21%) R) and Amphotericin B 31(100%) S). Among the 19 C. albicans, four were positive for ERG11 gene.

CONCLUSION

The isolation of C. albicans and non - albicans from respiratory specimens should be reconsidered as these organisms are re-emerging pathogens. Speciation is needed due to variation in species pathogenicity and their susceptibility.