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Alexander Sulakvelidze

Publications and source records attributed to Alexander Sulakvelidze.

12 recordsLinked to original sources
PubMed2006

Genetic background and antibiotic resistance of Staphylococcus aureus strains isolated in the Republic of Georgia.

The genetic composition and antibiotic sensitivities of 50 clinical isolates of Staphylococcus aureus obtained from various clinics in the Republic of Georgia were characterized. S. aureus strains ATCC 700699 and ATCC 29737 were included as reference standards in all analyses. All 52 strains had identical 16S rRNA profiles. In contrast, pulsed-field gel electrophoresis (PFGE) identified 20 distinct PFGE types among the 52 strains examined, which indicates that PFGE is more discriminating than is 16S rRNA sequence analysis for differentiating S. aureus strains. The results of our PFGE typing also suggest that multiple genetic subpopulations (related at the ca. 85% similarity level, based on their SmaI PFGE patterns) exist among the Georgian S. aureus strains. Twenty-two of the 50 Georgian strains were methicillin resistant and PCR positive for mecA, and 5 strains were methicillin sensitive even though they possessed mecA. None of the strains were vancomycin resistant or contained vanA. The nucleotide sequences of mecA fragments obtained from all mecA-containing strains were identical. Our data indicate that the population of S. aureus strains in Georgia is fairly homogeneous and that the prevalence of methicillin-resistant, mecA-positive strains is relatively high in that country.

Anti-Bacterial Agents↗
PubMed2005

Spontaneous tail length variation in a Salmonella myovirus.

Salmonella phage SPT-1, a member of the Myoviridae family and a relative of phage O1, produces abnormally long tails with coordinate variations of sheath and core length. The length of abnormal tails varies between 140 and 445 nm.

Microscopy, Electron↗
PubMed2005

The use of a novel biodegradable preparation capable of the sustained release of bacteriophages and ciprofloxacin, in the complex treatment of multidrug-resistant Staphylococcus aureus-infected local radiation injuries caused by exposure to Sr90.

In December 2001, three Georgian lumberjacks from the village of Lia were exposed to a strontium-90 source from two Soviet-era radiothermal generators they found near their village. In addition to systemic effects, two of them developed severe local radiation injuries which subsequently became infected with Staphylococcus aureus. After hospitalization in Tbilisi, Georgia, the patients were treated with various medications, including antibiotics and topical ointments; however, wound healing was only moderately successful, and their S. aureus infection could not be eliminated. Approximately 1 month after hospitalization, treatment with PhagoBioDerm (a wound-healing preparation consisting of a biodegradable polymer impregnated with ciprofloxacin and bacteriophages) was initiated. Purulent drainage stopped within 2-7 days. Clinical improvement was associated with rapid (7 days) elimination of the aetiologic agent, a strain of S. aureus resistant to many antibiotics (including ciprofloxacin), but susceptible to the bacteriophages contained in the PhagoBioDerm preparation.

Anti-Infective Agents↗
PubMed2005

Multilocus sequence typing versus pulsed-field gel electrophoresis for characterization of extended-spectrum beta-lactamase-producing Escherichia coli isolates.

Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli strains are emerging pathogens. Molecular typing of ESBL-producing E. coli is useful for surveillance purposes, to monitor outbreaks and track nosocomial spread. Although pulsed-field gel electrophoresis (PFGE) is the current "gold standard" for bacterial molecular typing, multilocus sequence typing (MLST) may offer advantages. Forty ESBL-producing E. coli isolates were selected at random from a cohort of intensive care unit patients who had active surveillance perirectal cultures done. PFGE identified 19 unique PFGE types (PT) among the 40 isolates; MLST identified 22 unique sequence types. MLST had greater discriminatory ability than PFGE for ESBL-producing E. coli. Simpson's indices of diversity for PFGE and MLST were 0.895 and 0.956, respectively. There were five clonal complexes (CCs) (isolates with differences of no more than two loci) that each contained multiple PT, but each PT was found in only one CC, indicating genetic consistency within a CC. MLST has clear utility in studies of ESBL-producing E. coli, based on a greater discriminatory ability and reproducibility than PFGE and the ability to a priori define genetically related bacterial strains.

Bacterial Typing Techniques↗
PubMed2005

Multilocus sequence typing for studying genetic relationships among Yersinia species.

The intra- and interspecies genetic relationships of 58 strains representing all currently known species of the genus Yersinia were examined by multilocus sequence typing (MLST), using sequence data from 16S RNA, glnA, gyrB, recA, and Y-HSP60 loci. Yersinia aldovae, Y. bercovieri, Y. intermedia, Y. pestis, Y. pseudotuberculosis, Y. rohdei, and Y. ruckeri were genetically more homogeneous than were Y. enterocolitica, Y. frederiksenii, Y. kristensenii, and Y. mollaretii. The MLST data concerning the genetic relatedness within and among various species of Yersinia support the idea that Y. pestis and Y. pseudotuberculosis are two lineages within the same species rather than two distinct species. Y. ruckeri is the genetically most distant species within the genus. There was evidence of O-antigen switching and genetic recombination within and among various species of Yersinia. The genetic relatedness data obtained by MLST of the four housekeeping genes and 16S RNA agreed in most, but not all, instances. MLST was better suited for determining genetic relatedness among yersiniae than was 16S RNA analysis. Some strains of Y. frederiksenii and Y. kristensenii are genetically less related to other strains within those species, compared to strains of all other species within the genus. The taxonomic standing of these strains should be further examined because they may represent currently unrecognized Yersinia species.

Animals↗
PubMed2004

Comparative analysis of multilocus sequence typing and pulsed-field gel electrophoresis for characterizing Listeria monocytogenes strains isolated from environmental and clinical sources.

One hundred seventy-five Listeria monocytogenes strains were characterized by serotyping, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) based on loci in actA, betL, hlyA, gyrB, pgm, and recA. One hundred twenty-two sequence types (STs) were identified by MLST based on allelic profiles of the four housekeeping genes (betL, gyrB, pgm, and recA), and 34 and 38 alleles were identified for hlyA and actA, respectively. Several actA and hlyA alleles appeared to be predominantly associated with clinical isolates. MLST differentiated most of the L. monocytogenes strains better than did PFGE, and the discriminating ability of PFGE was better than that of serotyping. Several strains with different serotypes were found, by MLST and PFGE, to have very closely related genetic backgrounds, which suggested possible "antigen switching" among them. MLST can be a useful typing tool for differentiating L. monocytogenes strains (including strains undistinguishable by PFGE typing and serotyping), and it may be of value during investigations of food-borne outbreaks of listeriosis.

Bacterial Typing Techniques↗
PubMed2003

Biocontrol of Listeria monocytogenes on fresh-cut produce by treatment with lytic bacteriophages and a bacteriocin.

The fresh-cut produce industry has been the fastest-growing portion of the food retail market during the past 10 years, providing consumers with convenient and nutritious food. However, fresh-cut fruits and vegetables raise food safety concerns, because exposed tissue may be colonized more easily by pathogenic bacteria than intact produce. This is due to the higher availability of nutrients on cut surfaces and the greater potential for contamination because of the increased amount of handling. We found that applied Listeria monocytogenes populations survived and increased only slightly on fresh-cut Red Delicious apples stored at 10 degrees C but increased significantly on fresh-cut honeydew melons stored at 10 degrees C over 7 days. In addition, we examined the effect of lytic, L. monocytogenes-specific phages via two phage application methods, spraying and pipetting, on L. monocytogenes populations in artificially contaminated fresh-cut melons and apples. The phage mixture reduced L. monocytogenes populations by 2.0 to 4.6 log units over the control on honeydew melons. On apples, the reduction was below 0.4 log units. In combination with nisin (a bacteriocin), the phage mixture reduced L. monocytogenes populations by up to 5.7 log units on honeydew melon slices and by up to 2.3 log units on apple slices compared to the control. Nisin alone reduced L. monocytogenes populations by up to 3.2 log units on honeydew melon slices and by up to 2.0 log units on apple slices compared to the control. The phage titer was stable on melon slices, but declined rapidly on apple slices. The spray application of the phage and phage plus nisin reduced the bacterial numbers at least as much as the pipette application. The effectiveness of the phage treatment also depended on the initial concentration of L. monocytogenes.

Bacteriophages↗
PubMed2003

Multilocus sequence typing has better discriminatory ability for typing Vibrio cholerae than does pulsed-field gel electrophoresis and provides a measure of phylogenetic relatedness.

Twenty-two Vibrio cholerae isolates, including some from "epidemic" (O1 and O139) and "nonepidemic" serogroups, were characterized by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) by using three housekeeping genes, gyrB, pgm, and recA; sequence data were also obtained for the virulence-associated genes tcpA, ctxA, and ctxB. Even with the small number of loci used, MLST had better discriminatory ability than did PFGE. On MLST analysis, there was clear clustering of epidemic serogroups; much greater diversity was seen among tcpA- and ctxAB-positive V. cholerae strains from other, nonepidemic serogroups, with a number of tcpA and ctxAB alleles identified.

Alleles↗
PubMed2002

A novel sustained-release matrix based on biodegradable poly(ester amide)s and impregnated with bacteriophages and an antibiotic shows promise in management of infected venous stasis ulcers and other poorly healing wounds.

Healing of poorly vascularized and venous stasis ulcers is often refractory to therapy, particularly when they are infected. Systemic antibiotic therapy may be of little benefit in this setting because of poor penetration of the antibiotic into the wound and the frequent associated emergence of bacterial strains resistant to common antimicrobial agents. Given the clinical significance of these problems, there is a need to explore alternative management approaches for these difficult-to-treat wounds. PhagoBioDerm is a novel wound-healing preparation consisting of a biodegradable polymer impregnated with an antibiotic and lytic bacteriophages, which was recently licensed for sale in the Republic of Georgia (one of the former Soviet Union republics). In 1999-2000, in Tbilisi, Georgia, 107 patients who had ulcers that had failed to respond to conventional therapy were treated with PhagoBioDerm alone or in combination with other interventions. The wounds/ulcers healed completely in 67 (70%) of 96 patients for whom follow-up data were available. In 22 cases in which microbiologic data were available, healing was associated with the concomitant elimination of, or a reduction in, specific pathogenic bacteria in the ulcers. Our findings suggest that this slow-release biopolymer is safe and of possible benefit in the management of refractory wounds, and they support the apparent utility of bacteriophages in this setting. Further studies, including carefully designed clinical trials, will be required to rigorously evaluate the efficacy of this novel wound dressing preparation.

Adult↗
PubMed2002

Evidence for the emergence of non-O1 and non-O139 Vibrio cholerae strains with pathogenic potential by exchange of O-antigen biosynthesis regions.

The novel epidemic strain Vibrio cholerae O139 Bengal originated from a seventh-pandemic O1 El Tor strain by antigenic shift resulting from homologous recombination-mediated exchange of O-antigen biosynthesis (wb*) clusters. Conservation of the genetic organization of wb* regions seen in other serogroups raised the possibility of the existence of pathogenic non-O1 and non-O139 V. cholerae strains that emerged by similar events. To test this hypothesis, 300 V. cholerae isolates of non-O1 and non-O139 serogroups were screened for the presence of virulence genes and an epidemic genetic background by DNA dot blotting, IS1004 fingerprinting, and restriction fragment length polymorphism (RFLP) analysis. We found four non-O1 strains (serogroups O27, O37, O53, and O65) with an O1 genetic backbone suggesting exchange of wb* clusters. DNA sequence analysis of the O37 wb* region revealed that a novel approximately 23.4-kb gene cluster had replaced all but the approximately 4.2-kb right junction of the 22-kb O1 wbe region. In sharp contrast to the backbones, the virulence regions of the four strains were quite heterogeneous; the O53 and O65 strains had the El Tor vibrio pathogenicity island (VPI) cluster, the O37 strain had the classical VPI cluster, and the O27 strain had a novel VPI cluster. Two of the four strains carried CTXphi; the O27 strain possessed a CTXphi with a recently reported immune specificity (rstR-4** allele) and a novel ctxB allele, and the O37 strain had an El Tor CTXphi (rstR(ET) allele) and novel ctxAB alleles. Although the O53 and O65 strains lacked the ctxAB genes, they carried a pre-CTXphi (i.e., rstR(cla)). Identification of non-O1 and non-O139 serogroups with pathogenic potential in epidemic genetic backgrounds means that attention should be paid to possible future epidemics caused by these serogroups and to the need for new, rapid vaccine development strategies.

Base Sequence↗
PubMed2002

Multilocus sequence typing for characterization of clinical and environmental salmonella strains.

Multilocus sequence typing (MLST) based on the 16S RNA, pduF, glnA, and manB genes was developed for Salmonella, and its discriminatory ability was compared to those of pulsed-field gel electrophoresis (PFGE) and serotyping. PFGE differentiated several strains undifferentiable by serotyping, and 78 distinct PFGE types were identified among 231 Salmonella isolates grouped into 22 serotypes and 12 strains of undetermined serotype. The strains of several PFGE types were further differentiated by MLST, which suggests that the discriminatory ability of MLST for the typing of Salmonella is better than that of serotyping and/or PFGE typing. manB-based sequence typing identified two distinct genetic clusters containing 32 of 54 (59%) clinical isolates whose manB gene sequences were analyzed. The G+C contents and Splitstree analysis of the manB, glnA, and pduF genes of Salmonella indicated that the genes differ in their evolutionary origins and that recombination played a significant role in their evolution.

Animals↗