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S Gaines

Publications and source records attributed to S Gaines.

At least 19 recordsLinked to original sources
PubMed2003

A novel spectrofluorometric microassay for Streptococcus mutans adherence to hydroxylapatite.

Adherence to the tooth surface by Streptococcus mutans is an important step in initiation of dental caries. Current in vitro methods used to study bacterial adherence are time-consuming and may involve the use of radiolabels. The aim of this study was to develop a more convenient, high-throughput, microtitre-plate assay of bacterial adherence to hydroxylapatite. S. mutans was labelled with the fluorescent indicator BCECF/AM and fluorescence measured using a spectrofluorometer. Fluorescence microscopy confirmed label uptake. Optimal labelling occurred at 120 min with 50 microM BCECF/AM in DMSO. Viability was similar in control untreated bacterial cells, bacteria treated with DMSO alone or with the label for up to 4 h. Preliminary adherence experiments were performed using four commercially available types of hydroxylapatite. Fluorescence from pre-labelled bacteria was measured for bound cells. The assay was then optimised with respect to time and bacterial concentration using Fluka crude hydroxylapatite. Time course studies demonstrated that adherence reached saturation by 30 min incubation when using 1x10(7) cfu/ml labelled bacteria to 1 mg hydroxylapatite, coated with PBS or saliva. The fluorescence-based adherence assay was highly reproducible in repeated analyses and was useful in demonstrating interference with adherence. In conclusion, this microtitre-plate assay offers a more convenient approach to examine streptococcal adherence and could be used to screen for potential anti-adhesive agents.

Bacterial Adhesion↗
PubMed2002

Characterization of antimicrobial resistance among Escherichia coli O111 isolates of animal and human origin.

Fifty isolates of Escherichia coli serogroup O111 recovered from humans and various animal species over a 24-year period (1976-1999) were examined for typical virulence-associated factors and susceptibilities to antimicrobials of human and veterinary significance. Nine H (flagellar) types were identified including nonmotile (n = 24), 32 (n = 12), negative (n = 5), and 56 (n = 3). Thirty-five (70%) isolates possessed at least one Shiga-toxin-producing E. coli (STEC)-associated virulence determinants (eae, stxl, stx2, hlyA) via PCR analysis. Of these 35 isolates, 20 possessed eae, stxl, and hlyA genes, whereas three isolates possessed eae, stxl, stx2, and hylA genes. Multiple antibiotic resistance was observed in 70% of the 50 E. coli O111 isolates. The majority of isolates displayed resistance to streptomycin, sulfamethoxazole, tetracycline, and kanamycin. Bacterial resistance to ampicillin, gentamicin, chloramphenicol, trimethoprim and apramycin was also observed. Integrons were identified in 23 (46%) of the E. coli isolates assayed, with a 1-kb amplicon being most frequently observed. DNA sequencing of these integrons revealed the presence of the aadA gene, encoding resistance to streptomycin. Two integrons of 1.5 and 2 kb contained the aadA2 and either dfrI or dfrXII genes, encoding resistance to streptomycin and trimethoprim, respectively. Integrons were also identified from isolates dating back to 1982. Isolates were further genetically characterized via ribotyping, which identified 15 distinct ribogroups, with 62% of isolates clustering into four major ribogroups. Certain riboprint patterns from different animal species, including humans, were observed in isolates spanning the 24-year collection period, suggesting the dissemination of specialized pathogenic O111 clones.

Animals↗
PubMed2001

Identification and characterization of integron-mediated antibiotic resistance among Shiga toxin-producing Escherichia coli isolates.

A total of 50 isolates of Shiga toxin-producing Escherichia coli (STEC), including 29 O157:H7 and 21 non-O157 STEC strains, were analyzed for antimicrobial susceptibilities and the presence of class 1 integrons. Seventy-eight (n = 39) percent of the isolates exhibited resistance to two or more antimicrobial classes. Multiple resistance to streptomycin, sulfamethoxazole, and tetracycline was most often observed. Class 1 integrons were identified among nine STEC isolates, including serotypes O157:H7, O111:H11, O111:H8, O111:NM, O103:H2, O45:H2, O26:H11, and O5:NM. The majority of the amplified integron fragments were 1 kb in size with the exception of one E. coli O111:H8 isolate which possessed a 2-kb amplicon. DNA sequence analysis revealed that the integrons identified within the O111:H11, O111:NM, O45:H2, and O26:H11 isolates contained the aadA gene encoding resistance to streptomycin and spectinomycin. Integrons identified among the O157:H7 and O103:H2 isolates also possessed a similar aadA gene. However, DNA sequencing revealed only 86 and 88% homology, respectively. The 2-kb integron of the E. coli O111:H8 isolate contained three genes, dfrXII, aadA2, and a gene of unknown function, orfF, which were 86, 100, and 100% homologous, respectively, to previously reported gene cassettes identified in integrons found in Citrobacter freundii and Klebsiella pneumoniae. Furthermore, integrons identified among the O157:H7 and O111:NM strains were transferable via conjugation to another strain of E. coli O157:H7 and to several strains of Hafnia alvei. To our knowledge, this is the first report of integrons and antibiotic resistance gene cassettes in STEC, in particular E. coli O157:H7.

Animals↗
PubMed2000

Genetic structure of populations of the red sea urchin, Strongylocentrotus franciscanus.

Population subdivision was evaluated in the red sea urchin, Strongylocentrotus franciscanus, using DNA sequence data from 134 adult individuals collected in 1995 and 1996. On average 22 individuals were sequenced from six geographic locations between Alaska and Baja California (N=134), nearly the full extent of the species range. DNA sequence data was obtained from direct sequencing of a 273 base pair region of the bindin gene, which encodes a sperm fertilization protein. Results indicate that bindin is sufficiently polymorphic to serve as a genetic marker. We identified 14 unique alleles present in the entire range sampled with a maximum of eight alleles at a specific site. Mean pairwise comparison of the 14 unique alleles indicates moderate sequence diversity (p-distance=1.06). Although there is conflicting evidence to suggest that Alaska populations may deviate from the Hardy-Weinberg expectations, analysis of bindin genotype frequencies indicate that it is not possible to reject the null hypothesis of random mating throughout the species range. The results of a chi-square test with pooling conform to Hardy-Weinberg expectations for all populations (P>0.05) except for the Alaska population (P=0.037). Inbreeding coefficients are consistent with this result and suggest that for the bindin locus, there is high gene flow. These results are compared with previously published results of genetic substructuring in sea urchins to examine relationships among population structure, dispersal potential and biogeography.

Journal Article↗
PubMed1997

Modeling drug residue uptake by eggs: yolks contain ampicillin residues even after drug withdrawal and nondetectability in the plasma.

The present study was conducted to determine whether: 1) preovulatory yolks may be an important storage depot for drug residues in eggs laid days to weeks after drug withdrawal; and 2) the prediction model based on the pattern of drug incorporation in developing yolks is predictive of the pattern of residues contained in the sequence of eggs laid during and after drug withdrawal. To test these possibilities, 24 hens were dosed for either 1, 2, or 3 d with ampicillin, and the content and pattern of residues in laid eggs were evaluated during and after dosing. Hens were bled 24 h after the final dosing, and plasma ampicillin concentrations were determined. Ampicillin was used in this study because it has an extremely short plasma halflife in laying hens that limits additional drug transfer after drug withdrawal. Ampicillin concentrations were not detectable in plasma from hens injected with ampicillin for either 1, 2 or 3 d (assay sensitivity of 0.6 ng/ml or 0.6 ppb). Hens from all three injection groups produced eggs containing detectable ampicillin residues for 6 d after the last injection. These data demonstrate that drug residues are contained in eggs laid a number of days after drug withdrawal. Because plasma ampicillin was not detectable even 24 h after final dosing, the majority, if not all, of the incurred ampicillin residues contained in eggs laid after drug withdrawal were due to incorporation and storage of drug in preovulatory yolks during the dosing period. Additionally, accounting for ampicillin's stability, our model is predictive of the pattern of residues contained in eggs. These data emphasize the importance of transfer and storage of drugs in preovulatory yolks as a significant contributing mechanism for the production of incurred drug residues in eggs.

Ampicillin↗
PubMed1990

The geriatric market.

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Attitude of Health Personnel↗
PubMed1988

Recruitment dynamics in complex life cycles.

Organisms living in the marine rocky intertidal zone compete for space. This, together with predation, physical disruption, and differing species tolerances to physiological stress, explains the structure of the ecological communities at some sites. At other sites the supply of larvae is limiting, and events in the offshore waters, such as wind-driven upwelling, explain the composition of intertidal communities. Whether the community ecology at a site is governed by adult-adult interactions within the site, or by limitations to the supply of larvae reaching the site, is determined by the regional pattern of circulation in the coastal waters. Models combining larval circulation with adult interactions can potentially forecast population fluctuations. These findings illustrate how processes in different ecological habitats are coupled.

Animals↗
PubMed1985

Larval settlement rate: A leading determinant of structure in an ecological community of the marine intertidal zone.

Field studies demonstrate that the population structure of the barnacle Balanus glandula differs between locations of high and low larval settlement rate. These observations, together with results from a model for the demography of an open, space-limited population, suggest that the settlement rate may be a more important determinant of rocky intertidal community structure than is presently realized. Locations with a low larval settlement rate exhibit a generally low abundance of barnacles that varies slightly within years and greatly between years, reflecting yearly differences in settlement. Locations with a high-settlement rate exhibit a generally high abudance of barnacles. However, the abundance varies greatly within years with a significant oscillatory component (period, 30 weeks) and only slightly between years regardless of yearly differences in settlement. At the low-settlement location mortality of barnacles is independent of the area occupied by barnacles. At the high-settlement location mortality is cover-dependent due to increased predation by starfish on areas of high barnacle cover. In both locations the cover-independent component of mortality does not vary with age during the first 60 weeks. As assumed in the demographic model, the kinetics of larval settlement can be described as a process in which the rate of settlement to a quadrat is proportional to the fraction of vacant space within the quadrat. Generalizations that the highest species diversity in a rocky intertidal community is found at locations of intermediate disturbance, and that competition causes zonation between species of the barnacle genera Balanus and Chthamalus, seem to apply only to locations with high-settlement rates.

Journal Article↗
PubMed1984

Comparison of predicted and adult heights in short boys: effect of androgen therapy.

We evaluated the accuracy of height predictions based on the tables of Bayley and Pinneau (2) in 43 boys with short stature. Sixteen boys were treated with androgens and 27 received no treatment. In 17 boys whose bone ages were within normal limits, and who received no treatment, the mean +/- SE predicted height of 164.9 +/- 1.5 cm was not significantly different from the mean adult height (166.5 +/- 1.5 cm). The predicted height exceeded the actual adult height by more than 5.1 cm in only one instance [5.1 cm is the degree of accuracy reported by Bayley and Pinneau (2)]. In 10 boys, whose bone ages were severely delayed (more than 2 SD below their chronologic age) and also were not treated, predicted height overestimated adult height by more than 5.1 cm in five of them. This difference was statistically significant (P less than 0.05). In five boys with normal bone ages, androgen therapy had no significant effect on either predicted height (168.1 +/- 4.1 before, 166.8 +/- 4.4 cm after) or actual adult height (166.5 +/- 4.1 cm). The 11 boys with severely delayed bone ages had a significant increase in predicted height during androgen therapy (165.4 +/- 1.5 to 169.8 +/- 1.7 cm, P less than 0.01), but actual adult height (162.4 +/- 2.4 cm) was not significantly greater than pretreatment predicted height. Further, the number of boys whose predicted height exceeded their adult height by 5.1 cm was not significantly different in treated (4/11) or untreated (5/10) boys.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1971

Characteristics of antimicrobial resistance of Escherichia coli from animals: relationship to veterinary and management uses of antimicrobial agents.

Five-hundred fifty-five (555) isolates of Escherichia coli were obtained from fecal specimens of a representative number of animals from five farms in the United States. Antibiotic exposure of the selected herds was determined by an epidemiological survey of these farms. The incidence of multiple resistance in the E. coli isolates was higher in herds exposed to continuous feeding of antimicrobial agents (84.8%) than in a herd not receiving antimicrobials (15.7%). The most common resistance configuration observed was the triple pattern of dihydrostreptomycin (DS), sulfonamide (SU), and tetracycline (TE). The second most frequent pattern consisted of four resistances: ampicillin (AM), DS, SU, and TE. The frequency of transfer factors was much higher in multiply resistant organisms from the herds exposed to antimicrobial medicaments. The E. coli isolates were relatively efficient in fostering and transferring heterologous resistance factors. AM resistance factors occurred more frequently in herds which were exposed to feed levels of penicillin (27.9%) than in those that were not (6.4%).

Animal Diseases↗