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Pathogenic microbes of the oral environment

Park AW, Yaacob HB

J Nihon Univ Sch Dent, 1994 Mar;36(1):1-33.
PMID: 8207501
Matched MeSH terms: Candida/pathogenicity
Candida and invasive candidiasis: back to basics

Lim CS, Rosli R, Seow HF, Chong PP

Eur J Clin Microbiol Infect Dis, 2012 Jan;31(1):21-31.
PMID: 21544694 DOI: 10.1007/s10096-011-1273-3

The ubiquitous Candida spp. is an opportunistic fungal pathogen which, despite treatment with antifungal drugs, can cause fatal bloodstream infections (BSIs) in immunocompromised and immunodeficient persons. Thus far, several major C. albicans virulence factors have been relatively well studied, including morphology switching and secreted degradative enzymes. However, the exact mechanism of Candida pathogenesis and the host response to invasion are still not well elucidated. The relatively recent discovery of the quorum-sensing molecule farnesol and the existence of quorum sensing as a basic regulatory phenomenon of the C. albicans population behavior has revolutionized Candida research. Through population density regulation, the quorum-sensing mechanism also controls the cellular morphology of a C. albicans population in response to environmental factors, thereby, effectively placing morphology switching downstream of quorum sensing. Thus, the quorum-sensing phenomenon has been hailed as the 'missing piece' of the pathogenicity puzzle. Here, we review what is known about Candida spp. as the etiological agents of invasive candidiasis and address our current understanding of the quorum-sensing phenomenon in relation to virulence in the host.

Matched MeSH terms: Candida/pathogenicity*
Genetic relatedness of Candida strains isolated from women with vaginal candidiasis in Malaysia

Chong PP, Lee YL, Tan BC, Ng KP

J Med Microbiol, 2003 Aug;52(Pt 8):657-66.
PMID: 12867559

The aims of this study were to compare the genetic relatedness of: (i) sequential and single isolates of Candida strains from women with recurrent vaginal candidiasis (RVC); and (ii) Candida strains from women who had only one episode of infection within a 1-year period. In total, 87 isolates from 71 patients were cultured, speciated and genotyped by random amplification of polymorphic DNA (RAPD) analysis. Patients were categorized into three groups, namely those with: (i) a history of RVC from whom two or more yeast isolates were obtained (group A); (ii) a history of RVC from whom only a single isolate was obtained (group B); and (iii) a single episode of vaginal candidiasis within a 1-year period (group C). Six yeast species were detected: Candida albicans, Candida glabrata, Candida lusitaniae, Candida famata, Candida krusei and Candida parapsilosis. Interestingly, the prevalence of non-albicans species was higher in group A patients (50 %) than in patients in groups B (36 %) or C (18.9 %). Eighty RAPD profiles were observed, with a total of 61 polymorphic PCR fragments of distinct sizes. Clustering analysis showed that, overall, the majority of patients in group A had recurrent infections caused by highly similar, but not identical, sequential strains [mean pairwise similarity coefficient (S(AB)) = 0.721 +/- 0.308]. The range of mean S(AB) values for intergroup comparisons for C. albicans isolates alone was 0.50-0.56, suggesting that there was no significant relatedness between strains from different groups. Genetic similarity of C. albicans isolates from patients in group A was lower than that of C. albicans isolates from patients in group C (mean S(AB) = 0.532 +/- 0.249 and 0.636 +/- 0.206, respectively); this difference was statistically significant (P = 0.036). These results demonstrate that the cause of recurrent infections varies among individuals and ranges between strain maintenance, strain microevolution and strain replacement; the major scenario is strain maintenance with microevolution. They also show that C. albicans strains that cause recurrent infections are less similar to each other than strains that cause one-off infections, suggesting that the former may represent more virulent subtypes.

Matched MeSH terms: Candida/pathogenicity
Fulltext Effect of phenotypic switching on the biological properties and susceptibility to chlorhexidine in Candida krusei ATCC 14243

Arzmi MH, Abdul Razak F, Yusoff Musa M, Wan Harun WH

FEMS Yeast Res., 2012 May;12(3):351-8.
PMID: 22225549 DOI: 10.1111/j.1567-1364.2011.00786.x

Phenotypic switching is characterized as a virulence factor of Candida spp. This study was carried out to evaluate the phenotypic switching ability of C. krusei ATCC 14243 and to determine its effect on the biological properties, adherence capacity and susceptibility towards chlorhexidine digluconate (CHX). To induce switched generations C. krusei was cultured under nitrogen-depleted growth conditions by adding phloxine B. These phenotypically switched colonies were designated as the 1st generation. Subsequent sub-culturing was performed to produce the 2nd, 3rd and 4th switched generations. The recovery of the 3rd generation was the highest at 85.7% while that of the 4th generation was lower at 70.8%, and the recovery of the 1st and 2nd generations gradually reduced to 46.6% and 36.4%, respectively. All generations of C. krusei were susceptible towards CHX. The unswitched C. krusei was the most susceptible but the least adherent to coated hard surfaces. The 2nd generation was the least susceptible, but with the highest adherent ability. The minimum inhibition concentration and minimal fungicidal concentration of C. krusei of all generations were determined at 0.4 mg mL(-1) . These observations suggest that the switching activity of C. krusei induces changes to its biological properties and susceptibility towards CHX.

Matched MeSH terms: Candida/pathogenicity
Onychomycosis in Malaysia

Ng KP, Saw TL, Madasamy M, Soo Hoo T

Mycopathologia, 1999;147(1):29-32.
PMID: 10872513

The common etiological agents of onychomycosis are dermatophytes, molds and yeasts. A mycological nail investigation of onychomycosis using direct microscopy and culture was conducted by the Mycology Unit, Department of Medical Microbiology, University of Malaya from March 1996 to November 1998. The study involved 878 nail clippings or subungal scrapings from subjects with onychomycosis. On direct microscopy examination, 50% of the specimens were negative for fungal elements. On culture, 373 specimens had no growth; bacteria were isolated from 15 nail specimens. Among the 490 specimens with positive fungal cultures, 177 (36.1%) were dermatophytes, 173 (35.5%) were molds and 130 (26.5%) were Candida. There were 2% (10/490) mixed infections of molds, yeasts and dermatophytes. Trichophyton rubrum (115/177) and Trichophyton mentagrophytes (59/177) were the main dermatophytes isolated. The molds isolated were predominantly Aspergillus niger (61/173), Aspergillus nidulans (30/173), Hendersonula toruloidea (26/173) and Fusarium species (16/173). 96.9% of the Candida species identified were Candida albicans.

Matched MeSH terms: Candida/pathogenicity
Fulltext Oral Candidal Load and Oral Health Status in Chronic Obstructive Pulmonary Disease (COPD) Patients: A Case-Cohort Study

Khijmatgar S, Belur G, Venkataram R, Karobari MI, Marya A, Shetty V, et al.

Biomed Res Int, 2021;2021:5548746.
PMID: 34545329 DOI: 10.1155/2021/5548746

Objective: The objective of this study was to determine the candidal load of the patients with Chronic Obstructive Pulmonary Disease (COPD) and evaluate the oral health status of subjects with COPD. Material and Methods. N = 112 COPD subjects and N = 100 control subjects were included in the study. The selection of COPD cases was confirmed based on the set criteria from the American College of Physicians. The oral health status was assessed as per WHO criteria to determine the score of decayed, missing, and filled teeth (DMFT), significant caries index (SiC), community periodontal index and treatment needs (CPITN), and oral hygiene index-simplified (OHI-S). Gram staining was performed to identify Candida using the whole saliva. Quantitative evaluation of the candidal load was carried out using Sabouraud Dextrose Agar (SDA). Chrome agar was used to differentiate between the commensal carriages. A statistical analysis paired t-test and 95% confidence interval (CI) for proportions was carried out using STATA software.
Results: Candidal growth was found in 21.42% (n = 24) of COPD cases and 1.1% (n = 11) of control cases (p < 0.05) (95% CI 0.45, 0.59). The DMFT score was 8.26 in COPD subjects and 4.6 in controls, the SiC score was 16.42 in COPD subjects and 10.25 in controls, and the CPITN score for both COPD and control cases was score 2.
Conclusion: In conclusion, there was a higher candidal load among subjects suffering from COPD. Theophylline medication can be a risk factor for increased candidal load in COPD patients.

Matched MeSH terms: Candida/pathogenicity
Epidemiology of candidemia and antifungal susceptibility in invasive Candida species in the Asia-Pacific region

Wang H, Xu YC, Hsueh PR

Future Microbiol, 2016 10;11:1461-1477.
PMID: 27750452

In the Asia-Pacific region, Candida albicans is the predominant Candida species causing invasive candidiasis/candidemia in Australia, Japan, Korea, Hong Kong, Malaysia, Singapore and Thailand whereas C. tropicalis is the most frequently encountered Candida species in Pakistan and India. Invasive isolates of C. albicans, C. parapsilosis complex and C. tropicalis remain highly susceptible to fluconazole (>90% susceptible). Fluconazole resistance (6.8-15%), isolates with the non-wild-type phenotype for itraconazole susceptibility (3.9-10%) and voriconazole (5-17.8%), and echinocandin resistance (2.1-2.2% in anidulafungin and 2.2% in micafungin) among invasive C. glabrata complex isolates are increasing in prevalence. Moreover, not all isolates of C. tropicalis have been shown to be susceptible to fluconazole (nonsusceptible rate, 5.7-11.6% in China) or voriconazole (nonsusceptible rate, 5.7-9.6% in China).

Matched MeSH terms: Candida/pathogenicity*