Phenotypic and molecular methods used for identification of oral streptococci and related microorganisms.

The oral cavity contains the greatest biodiversity, over 70 species being isolated from mouth mucosa, saliva, denture surfaces and/or dental-plaque. The oral streptococci, representing over 80% of the mouth micro flora, are able to synthesize glucosyl-transferases, enzymes involved in glucans production. Glucans are involved in production of an extracellular slime layer promoting adhesion and formation of a dental plaque biofilm. The 43 isolates studied obtained from partially and/or totally edentulous, were identified by VITEK system using gram-positive identification cards. Species-specific regions within the genes coding for glucosyl-transferases (gtf genes) were targeted for PCR identification of isolates. Sequencing of 16S rRNA was used as gold standard for strain confirmation. VITEK system identified a number of 11 strains as S. mitis/oralis, 12 strains as S. anginosus/gordonii, 12 strains as S. sanguinis/parasanguinis, 3 strains as S. salivarius, 3 strains as S. plurianimalium, 1 strain as S. cristatus and 1 strain as S. alactolyticus, respectively. The PCR system targeting gtf genes was able to identify S. oralis, S. salivarius and S. gordonii strains. Sequence of 16S rRNA discriminated among streptococci species and revealed 16 strains of Leuconostoc mesenteroides. Many studies are needed in order to select the most reliable phenotypic and genotypic methods in order to improve the identification algorithm for oral streptococci used by clinical laboratories. Their accurate identification is mandatory for better understanding their role in human infections.

A multiple typing approach is recommended for the laboratory-based surveillance of salmonellosis in Romania.

In Romania, Salmonella enterica serovar Typhimurium isolates are currently typed by antimicrobial resistance profiles and phage typing, as part of the national laboratory-based surveillance system of human enteric infections. The aim of the present study was to assess the added value of complementing this approach with molecular fingerprinting, namely pulsed-field gel electrophoresis (PFGE) and multiple-locus variable-number tandem-repeats analysis (MLVA). Thirty-six S. Typhimurium isolates received by the Reference Center for Human Salmonella Infections for confirmation and typing from the Microbiology Departments of three Public Health Authorities, were selected for this study. Phage typing revealed that 14 isolates (39%) were nontypeable (NT). Twenty-two isolates were assigned to 5 phage types: DT193 (11 isolates), U302 (7 isolates), DT116 (2 isolates), DT41 (1 isolate) and DT86 (1 isolate). Antimicrobial susceptibility testing showed that all the NT and DT116 isolates were multidrug resistant and extended-spectrum betalactamase producers. All the examined isolates were typeable when using the molecular approach. Both methods gave conclusive and comparable results, documenting the genetic relatedness and discriminating the outbreak isolates from sporadic cases. We conclude that in order to improve outbreak investigation and surveillance of salmonellosis in Romania, the current routine typing of Salmonella isolates should be complemented with at least one of these DNA fingerprinting methods.

[Bacterial enteric pathogens' resistance to fluoroquinolones and last generation cephalosporines]. / Rezistenta patogenilor enterici bacterieni la fluoroquinolone si cefalosporine de ultima generatie.

The increase of incidence of resistance to the antibiotics became the most worrisome subject within the clinical and research communities in the medical fields. Intrinsic resistance genetic mutations, horizontal transfer of mobile structures carrying genes coding for resistance to the antibiotics within the pan-microbial genome are representing the bacterial resistome which is bearing the genetic information regarding the defensive mechanisms developed by micro-organisms to protect themselves against antibiotics. Rice in the resistance of enteric bacteria, pathogens involved in a large number of human infections, to the cephalosporin of last generation and to the fluoroquinolones is a very actual subject in the medical area. Production of beta-lactamases with extended spectrum is the most important enzymatic defence system, developed by micro-organisms, consisting in the inactivation of beta-lactam antibiotics by destroying the beta-lactam ring. Enterobacteria are able to produce beta-lactamases of type TEM, SHV and/or CTX-M. Punctual mutations in nucleotide structure of bla genes, coding for beta-lactamases synthesis, are leading on production of a large diversity of enzymes with enlarged spectrum of activity (ESBL). At the beginning of 90's the first beta-lactamases resistance to clavulanic acid were detected and in our days more then 170 TEM, 120 SVH and 90 CTX-MESBLs are known. Escherichia coli strains are producing, firstly, TEM ESBLs, Klebsiella pneumoniae SHV ESBLs. and both are producing CTX-M type ESBLs, are resistant to the fluoroquinolones due to punctual mutations in nucleotide structure of gyr gene coding for gyrases production, enzymes involved in nucleic acids replication. Resistance to the antibiotics with extended activity is a public health threat due to their capacity of large spreading within bacterial population, when the coding structures are located on mobile genetic structures. The menace increase when genes coding for fluoroquinolones resistance (qnr) are identified on such of structures.

Antimicrobial Susceptibility Testing for Corynebacterium Species Isolated from Clinical Samples in Romania.

Antimicrobial resistance is one of the most important public health issues. Besides classical multidrug resistance species associated with medical care involved in superficial or invasive infections, there are strains less commonly associated with hospital or outpatient setting's infections. Non-diphtheria Corynebacterium spp. could produce infections in patients with or without immune-compromised status. The aim of our study was to determine the susceptibility to antimicrobial agents to Corynebacterium spp. from clinical samples collected from Romanian hospitalized individuals and outpatients. Twenty Corynebacterium strains were isolated and identified as Corynebacterium striatum (n = 7), Corynebacterium amycolatum (n = 7), C. urealyticum (n = 3), Corynebacterium afermentans (n = 2), and Corynebacterium pseudodiphtheriticum (n = 1). All isolates have been tested for antibiotic susceptibility by standardized disc diffusion method and minimal inhibitory concentration (MIC) tests. Seventeen isolates demonstrated multidrug resistance phenotypes. The molecular support responsible for high resistance to quinolones for ten of these strains was determined by the detection of point mutation in the gene sequence gyrA.

Pulsed-field gel electrophoresis associated to phage typing improves the discrimination of epidemiologically unrelated Salmonella enterica serovar typhimurium isolates.

A combination of phage typing and pulsed-field gel electrophoresis (PFGE) of Xbal- and Blnl-digested chromosomal DNA has been used to study 18 epidemiologically unrelated human Salmonella enterica serovar Typhimurium isolates, which were collected during 2007 within a single Romanian county. Phage typing could assign only four of the isolates to three definitive phage types (DT41, DT86, and DT116), the rest being untypable by this classical method. PFGE analysis of the double enzyme-digested DNA, performed in an attempt to further discriminate the strains, allowed the typing of all the studied isolates. Xbal-digested genomic DNA segregated the isolates into 7 X-types and Blnl restriction differentiated them into 8 B-types. Our PFGE results documented the circulation of a rather homogeneous population of S. Typhimurium strains within the same county. As in the case of other human pathogens, epidemiological conclusions might be more accurate if based on both phenotypic and genotypic methods, therefore molecular typing should be added within the national laboratory-based surveillance of Salmonella infections.

Identification of plasmid-mediated quinolone resistance qnr-like genes in Romanian clinical isolates of Escherichia coli and Klebsiella pneumoniae.

A collection of putative ESBL-producing Escherichia coli (119 isolates) and Klebsiella pneumoniae (122 isolates) originating from extraintestinal human specimens was screened for qnrA, qnrB, and qnrS-like genes by PCR. Seven K. pneumoniae isolates, which were resistant to ciprofloxacin, were detected as carrying qnrA1-like genes, while one K. pneumoniae and one E. coli isolate were positive for qnrS-like determinant. The latter isolates were susceptible to ciprofloxacin. This is the first study identifying qnr-like genes in our area. Further studies are needed to document the contribution of the plasmid mediated quinolone resistance to the increase in bacterial resistance to fluoroquinolones in Romania.

Laboratory diagnosis of infectious diarrhoea syndrome; a three years study in two hospitals of infectious diseases.

Infectious diarrhoea is a syndrome caused by a variety of bacterial, viral and parasitic organisms which represents a major cause of morbidity and mortality all over the world. The wide diversity of etiological agents impairs the surveillance and the diagnosis and affects the correct treatment applied to reduce the long-term complications. Besides well known enteric pathogens such as Salmonella, Shigella and Yersinia, a high number of emergent and re-emergent aetiologies are now recognised to be at the origin of diarrhoea. The lack of a correct diagnostic algorithm and adequate methods of analyses leads to under-evaluation and incertitude in an important number of clinical cases. Our study was designed as a complex analysis of the stool specimens collected from the patients, in the purpose to improve the laboratory diagnostic and to enhance the number of confirmed cases of infectious diarrhoea. A number of 756 samples from inpatients with diarrhoea were tested targeting pathogenic and opportunistic bacteria, viruses and parasites by classical and molecular methods. We documented that, in case of non-Salmonella, non-Shigella, non-Yersinia diarrhoea, the quality of diagnostic was improved by increasing the percentage of positive specimens to 22.49% compared to 11.12% when only bacteria, 5.56% when only viruses and 4.10% when only parasites were investigated. The laboratory data are of great value in evaluating the diarrhoea syndrome offering the documentation for an accurate epidemiological response and an adequate treatment.

Molecular detection of verotoxin-producing Escherichia coli isolates in stool samples from patients with diarrhea.

Despite its occurence as a commensal in the human intestine, Escherichia coli is also known as a versatile gastrointestinal pathogen. Identification of diarrheagenic E. coli (DEC) requires the accurate discrimination of pathogenic strains from commensal flora, and this is not an easy task if the diagnostic tools are inadequate. As the information regarding the relative contribution of DEC among other identifiable causes of infectious diarrhea in Romanian patients is scarce, a prospective study was conducted to evaluate the prevalence of enteropathogenic Escherichia coli (EPEC) and verotoxin-producing Escherichia coli (VTEC) isolates in the diarrheagenic stool specimens of 120 children and 270 adults. PCR-based detection of the eae, bfp, vtx1 and vtx2 genes was added to the conventional culture and slide agglutination with 12 commercial EPEC antisera and O157:H7 antisera for identifying EPEC and VTEC isolates. Even though E. coli colonies belonging to traditional EPEC serogroups were isolated from 35 children and 17 adults, only the isolates recovered from 16 children and 2 adults harboured at least one of the targeted pathogenicity-associated genes. The children shedding EPEC outnumbered the adults (16.7% vs. 7.4%). Based on the virulence genotype identified, the prevalence of atypical EPEC (eae+) was higher than of typical EPEC (eae+ bfpA+), and typical EPEC identification was restricted to children. Owing to the molecular analysis 5 children and 10 adults that could have been overlooked by the routine microbiological investigation were diagnosed as infected with VTEC. Considering that none of the screened stool specimens was positive for E. coli O157:H7, this study reports for the first time the presence of VTEC nonO157 in local patients with diarrhea. Our results bring evidence that both EPEC and VTEC isolates are circulating as agents of local sporadic cases of human diarrhea. Further studies are needed to evaluate the contribution of DEC to the human disease burden in Romania, based on improved diagnostic tools targeting the main virulence traits of E. coli clinical isolates.

Characteristics of Romanian fluoroquinolone-resistant human clinical Escherichia coli isolates.

Alarming progressive increase in the prevalence of antimicrobial resistance in Escherichia coli has been documented worldwide. Previous studies have suggested that many E. coli clinical isolates are actually low-virulence opportunists whose success derives more from antibiotic resistance than from pathogenic capability. The co-existence of ESBL production and fluoroquinolone resistance was reported as a major therapeutic challenge for E. coli infections. Considering the sparse information regarding the genetic background of virulence and antibiotic resistance of local isolates, a collection of ciprofloxacin-resistant E. coli isolates from human extraintestinal specimens was analyzed using PCR, PCR-sequencing, and PFGE, in order to clarify some aspects regarding their mechanisms of antimicrobial resistance, phylogenetic origin, the content of virulence-encoding determinants, and clonal relatedness. The tested fluoroquinolone resistant E. coli (FQREC) isolates, which displayed genetic heterogeneity, carried double mutations in the QRDR of gyrA previously described, which could explain their high resistance to ciprofloxacin. More than half of them (69%) possessed group 1 blaCTX. like genes, and with one exception, all these isolates were ESBL producers. The FQREC isolates belonging to non B2 phylogenetic groups outnumbered the isolates derived from B2 group (60 versus 27 isolates), and their overall content of virulence-encoding genes (fim, pap, sfa/foc, afa, hly, cnf and aer) was reduced. Regardless of the phylogenetic origin, the most prevalent virulence-associated genes possessed by the FQREC isolates were aer and fim determinants, while none of these isolates carried hly and cnf genes. In the case of weakened patients, the E. coli isolates do not need a robust virulence repertoire in order to overcome the host defense systems. The co-resistance of many FQREC isolates to extended-spectrum cephalosporins may provide a substantial advantage to their survival and spreading within the hospital environment.

Virulence genotypes of Escherichia coli strains from bacteremia in relation to phylogeny.

Bacteremia is the principal way of dissemination of local infections to distant organs. Escherichia coli bacteremia is almost always clinically significant, suggesting an increased risk of developing sepsis syndrome. Fifty-one E. coli bloodstream human isolates were analyzed using PCR technique for several molecular markers associated with extraintestinal virulence, and their phylogenetic group assignment, taking into account the link between the phylogenetic background and the intrinsic virulence of this species. Sixteen virulence genotypes have been identified, the majority of the blood isolates carrying the association of two genes. The genes encoding type 1 fimbria and aerobactin had the highest prevalence. As a confirmation of other studies, the strains assigned to E. coli phylogenetic group B2 exhibited the highest concentration of virulence genes, and represented almost half of the clinical blood isolates. The multifactorial virulence of E. coli strains isolated from invasive infections reflects a phylogenetic inheritance, and supports the concept of ExPEC pathotype as a subset of E. coli population involved in human infectious diseases. The surveillance of geographical variation of E. coli pathogenic clones is useful for epidemiological analysis.