Applications of multilocus enzyme electrophoresis in medical microbiology

Genotyping of oral Candida albicans and Candida tropicalis strains in patients with orofacial clefts undergoing surgical rehabilitation by MALDI-TOF MS: Case-series study

Patients with orofacial clefts are more likely to develop oral fungal diseases due to anatomo-physiological changes and surgical rehabilitation treatment. This case-series study evaluated the genetic diversity and dynamics of oral colonization and spread of C. albicans and C. tropicalis in four patients with orofacial clefts, from the time of hospital admission, perioperative and outpatient follow-up, with specialized physician. Candida biotypes previously identified by CHROMagar Candida and PCR methods were studied by MALDI-TOF MS assays and clustering analyses. Possible correlations with pathogenicity characteristics were observed, including production of hydrolytic exoenzymes and the antifungal sensitivity profiles. Amphotericin B-sensitive and fluconazole-resistant (low frequency) C. tropicalis and C. albicans, including clinically compatible MIC of nystatin, were found in the oral cavity of these patients. Clusters of isolates revealed phenomena of (i) elimination in the operative phase, (ii) maintenance or (iii) acquisition of oral C. tropicalis in the perioperative period and specialized outpatient and medical follow-up. For C. albicans, these phenomena included (i) elimination in the operative phase, (ii) acquisition in the operative phase and propagation from the hospital environment, and (iii) maintenance during hospitalization and operative phase. Amphotericin B and nystatin were shown to be effective in cases of clinical treatment and/or prophylaxis, especially considering the pre-existence of fluconazole-resistant strains. This study confirmed the phenomena of septic maintenance, septic neocolonization and septic elimination involving the opportunistic pathogens. MALDI-TOF MS associated with clustering analysis may assist the monitoring of clinical isolates or groups of epidemiologically important microbial strains in the hospital setting.

Methicillin-Resistant Staphylococcus aureus: Molecular Characterization, Evolution, and Epidemiology

Staphylococcus aureus, a major human pathogen, has a collection of virulence factors and the ability to acquire resistance to most antibiotics. This ability is further augmented by constant emergence of new clones, making S. aureus a "superbug." Clinical use of methicillin has led to the appearance of methicillin-resistant S. aureus (MRSA). The past few decades have witnessed the existence of new MRSA clones. Unlike traditional MRSA residing in hospitals, the new clones can invade community settings and infect people without predisposing risk factors. This evolution continues with the buildup of the MRSA reservoir in companion and food animals. This review focuses on imparting a better understanding of MRSA evolution and its molecular characterization and epidemiology. We first describe the origin of MRSA, with emphasis on the diverse nature of staphylococcal cassette chromosome mec (SCCmec). mecA and its new homologues (mecB, mecC, and mecD), SCCmec types (13 SCCmec types have been discovered to date), and their classification criteria are discussed. The review then describes various typing methods applied to study the molecular epidemiology and evolutionary nature of MRSA. Starting with the historical methods and continuing to the advanced whole-genome approaches, typing of collections of MRSA has shed light on the origin, spread, and evolutionary pathways of MRSA clones.

Isoenzymatic genotyping of Staphylococcus aureus from dairy cattle and human clinical environments reveal evolutionary divergences

Background

The genetic variability of 610 S. aureus isolates from the hands of professional dentists (A), dental clinic environment air (B), bovine milk from cows with and without mastitis (C), an insufflator for milking equipment (D) and milking environment air (E) was studied by isoenzyme genotyping and genetic and cluster analysis.

Results

Monoclonal and polyclonal patterns of S. aureus were detected in every bacterial population; however, isolates belonging to the same strain were not found among the populations, suggesting the genetic heterogeneity and the intrapopulation spread of strains. Genetic relationship analysis revealed the co-existence of highly related strains at low frequency among populations.

Conclusion

The data suggest that some strains can adapt and colonize new epidemiologically unrelated habitats. Consequently, the occurrence of an epidemiological genotypic identity can assume a dynamic character (spread to new habitats), however infrequently. A tendency of microevolutionary and genetic divergences among populations of S. aureus from human sources (AB) and bovine milk (DE), and especially the mammary quarter (C), is also suggested. This research can contribute to the knowledge on the distribution and dissemination of strains and the implementation of control measures and eradication of S. aureus in important dental clinic environments, as well as animal environments and dairy production.

Dynamics of the seasonal airborne propagation of Staphylococcus aureus in academic dental clinics

Objective

Staphylococcus aureus strains can be disseminated during dental treatments and occasionally lead to the contamination and infection of patients and dentists, which is an important public health problem. The dynamics of the airborne propagation and the genetic diversity of S. aureus isolated in an academic dental clinic environment were investigated using isoenzyme typing.

Material and Methods

The isoenzymes of 44 previously reported isolates were obtained from fresh cultures and extracted using glass beads. Nine isoenzymes were investigated using multilocus enzyme electrophoresis (MLEE). The genetic diversity and relationship among the strains (electrophoretic type – ET) were determined using statistics previously described by Nei²⁵ (1972) and the SAHN grouping method (UPGMA algorithm).

Results

Clonal pattern analyses indicated a high level of genetic polymorphism occurring among the 33 ETs, which were grouped into five taxa. Each taxon presented one or more clusters that were moderately related and that contained two or more identical/highly related isolates, revealing seasonal airborne propagation in these dental clinic environments.

Conclusions

These data suggest the occurrence of active microevolutionary processes in S. aureus as well as the possibility of environmental propagation during a 14-month time span. Such findings are important to show that multiuser academic dental clinics can retain certain strains that are spreadable to different niches.

Multilocus enzyme electrophoresis analysis of rapidly-growing mycobacteria: an alternative tool for identification and typing

OBJECTIVES

Rapidly growing mycobacteria (RGM) have emerged as important pathogens in clinical settings, associated with esthetic procedures and postsurgical infections, pulmonary infections among cystic fibrosis patients, and other structural pulmonary diseases. Microorganisms belonging to Mycobacterium abscessus-Mycobacterium chelonae and to Mycobacterium fortuitum groups have frequently been associated with outbreaks and various epidemics. In the present study, RGM strains were characterized in order to investigate molecular markers based on proteomic analysis.

METHODS

Multilocus enzyme electrophoresis (MLEE) was used for species identification and clonal analysis of RGM recovered from postsurgical wound infections during an epidemic. The study included 30M. abscessus subsp. bolletii clinical isolates, most belonging to the BRA100 clone (epidemic in Rio de Janeiro city), as well as 16 RGM ATCC reference strains.

RESULTS

Molecular typing allowed the detection of diversity in the studied population and revealed species-specific isoenzymatic patterns. Additionally, the clonal relationship among M. abscessus subsp. bolletii outbreak isolates, as examined using MLEE, was markedly consistent.

CONCLUSIONS

Isoenzymatic characterization was found to be a useful molecular tool to identify RGM species and to determine the relatedness among closely related M. abscessus subsp. bolletii isolates. This may be considered a powerful approach for epidemiological studies on RGM.

Candida albicans or Candida dubliniensis?

Candida albicans is increasing as an opportunistic pathogen causing candidemia and candidiasis worldwide. In addition, other non-albicans Candida species are now also associated with pertinent infections. These include the closely related C. dubliniensis, which shares many phenotypic similarities with C. albicans. These similarities pose problems in the identification of isolates and have previously led to misidentification of these species. As a result, several identification techniques based on phenotypic and genotypic characteristics have been developed to differentiate between these Candida species. This review will focus on the similarities and differences between these two Candida species highlighting different identification methods and their advantages and disadvantages.

Distribution and hydrolytic enzyme characteristics of Candida albicans strains isolated from diabetic patients and their non-diabetic consorts

INTRODUCTION

The aim of this study was to investigate the oral colonization profile of Candida albicans strains isolated from diabetic patients and their non-diabetic consorts. In addition hydrolytic enzyme activity of these isolates was analysed.

METHODS

The genetic diversity of C. albicans oral isolates from 52 couples was established using isoenzyme marker and cluster analysis. Hydrolytic enzyme characteristics, namely secreted aspartyl proteinases (SAPs) and phospholipases (PLs) were also analysed.

RESULTS

Simultaneous colonization by C. albicans was observed in the consorts of 12 couples (23.1%). Patterns of monoclonal and polyclonal oral colonization by C. albicans strains were identified and the coexistence of identical or highly related strains was observed in both members of eight couples. The genetic diversity observed in the total yeast population revealed four large, genetically distinct groups (A to D) and the coexistence of strains in couples or consorts conjugally unrelated. SAP and PL activity was observed in the majority of C. albicans isolates without any association to particular strain, strain clusters (highly related isolates), or clinical characteristics of the consorts (diabetic, non-diabetic, and gender).

CONCLUSION

Possible sources of transmission and oral propagation of groups (clusters) of strains of C. albicans can occur between diabetic and non-diabetic consorts. A conjugal genotypic identity exists in most C. albicans-positive couples, that is, both consorts share identical or highly related strains; however, this identity is not couple-specific as seen by the coexistence of clusters in couples and unrelated consorts.

Genetics and evolution of Neisseria meningitidis: importance for the epidemiology of meningococcal disease

Meningococcal disease is a life-threatening illness occurring worldwide with incidence rates varying from 1 to 1000 cases per 100,000. The causative organism, Neisseria meningitidis, is a normal commensal of humans. While strains associated with asymptomatic carriage are highly diverse, a few hyper-invasive genetic clones of the species may spread rapidly through human populations, resulting in countrywide epidemics of meningococcal meningitis. N. meningitidis fitness for spread and colonization is directly linked to the capability of the bacterium to change its genome and adapt to its environment, by means of a variety of genetic mechanisms. This review addresses some of the impacts of the evolutionary potential of N. meningitidis on the occurrence of meningococcal disease.

Parity among interpretation methods of MLEE patterns and disparity among clustering methods in epidemiological typing of Candida albicans

The typing of C. albicans by MLEE (multilocus enzyme electrophoresis) is dependent on the interpretation of enzyme electrophoretic patterns, and the study of the epidemiological relationships of these yeasts can be conducted by cluster analysis. Therefore, the aims of the present study were to first determine the discriminatory power of genetic interpretation (deduction of the allelic composition of diploid organisms) and numerical interpretation (mere determination of the presence and absence of bands) of MLEE patterns, and then to determine the concordance (Pearson product-moment correlation coefficient) and similarity (Jaccard similarity coefficient) of the groups of strains generated by three cluster analysis models, and the discriminatory power of such models as well [model A: genetic interpretation, genetic distance matrix of Nei (d(ij)) and UPGMA dendrogram; model B: genetic interpretation, Dice similarity matrix (S(D1)) and UPGMA dendrogram; model C: numerical interpretation, Dice similarity matrix (S(D2)) and UPGMA dendrogram]. MLEE was found to be a powerful and reliable tool for the typing of C. albicans due to its high discriminatory power (>0.9). Discriminatory power indicated that numerical interpretation is a method capable of discriminating a greater number of strains (47 versus 43 subtypes), but also pointed to model B as a method capable of providing a greater number of groups, suggesting its use for the typing of C. albicans by MLEE and cluster analysis. Very good agreement was only observed between the elements of the matrices S(D1) and S(D2), but a large majority of the groups generated in the three UPGMA dendrograms showed similarity S(J) between 4.8% and 75%, suggesting disparities in the conclusions obtained by the cluster assays.

Application of molecular techniques in the study of Staphylococcus aureus clonal evolution - A Review

Staphylococcus aureus is an important agent of healthcare-associated and community-acquired infections. A major characteristic of this microorganism is the ability to develop resistance to antimicrobial agents. Several molecular techniques have been applied for the characterization of S. aureus in epidemiological studies. In the present review, we discuss the application of molecular techniques for typing S. aureus strains and describe the nomenclature and evolution of epidemic clones of this important pathogen.

Multilocus enzyme electrophoresis typing of Candida albicans populations isolated from healthy children according to socioeconomic background

The aim of this research was to evaluate the genetic diversity within and between C. albicans populations isolated from the oral cavity of healthy Brazilian children classified into five socioeconomic categories (A to E). Multilocus Enzyme Electrophoresis (MLEE) analysis was the method used to assess genetic diversity. High genetic diversity was observed in all populations that showed predominance of some C. albicans subtypes (Electrophoretic Types - ETs). However, no correlation was observed between a specific ET and a specific population of children. Clustering analysis showed one or more highly related ET clusters, suggesting the existence of indirect and direct propagation routes of C. albicans among healthy children. Microevolutionary changes were observed in some C. albicans populations isolated from children with the same or very similar socioeconomic condition. Furthermore, low transition of C. albicans subtypes can be occurring among certain populations of children coming from high and medium/high, or high and medium/low, or medium/high and medium/low socioeconomic categories, which can also be explained by their own socioeconomic and cultural characteristics.

Genotypic diversity and virulence traits of Streptococcus mutans in caries-free and caries-active individuals

The present study evaluated the relationship between clonal diversity and some virulence traits of Streptococcus mutans isolated from eight caries-free and eight caries-active subjects. A total of 155 S. mutans isolates from caries-free subjects and 144 isolates from caries-active subjects were obtained from samples of saliva, dental plaque and tongue surface and identified by PCR. The isolates were submitted to arbitrarily primed (AP)-PCR (OPA-2 and OPA-13) and multilocus enzyme electrophoresis (MLEE) to establish the genotypic diversity. Production of water-insoluble glucan (WIG) (monitored by SDS-PAGE), final pH of cultures and the ability of bacterial cells to adhere to smooth glass in the presence of sucrose were measured. High and comparable abilities of MLEE and AP-PCR were found to distinguish S. mutans genotypes, using Simpson's index of discrimination (0.971 and 0.968, respectively). The results showed a significant difference (P < 0.01) in the number of genotypes when caries-free and caries-active groups were compared by both fingerprinting methods used. Final pH (P = 0.32) and the percentage of adherence to a glass surface (P = 0.62) did not show differences between the two groups; however, the intensities of WIG bands from the caries-active group were greater than those from the caries-free group (P < 0.01). In addition, WIG was positively correlated with the ability of S. mutans to adhere to a glass surface (r = 0.34, P = 0.02) from caries-active subjects. These data showed that AP-PCR analysis and MLEE are both effective methods for assessing the genetic relatedness of S. mutans. Using these techniques, it was found that there is a larger number of genotypes of S. mutans with increased ability to synthesize WIG in caries-active individuals.