No description available.

No description available.

Thesis (MApSc(MedicalLaboratorySce))--University of South Australia, 2003.

Antibiotic resistance is increasing worldwide, which is threatening the effectiveness of even the most potent and recent antibiotics. The successful treatment of disease is hampered due to the multidrug resistant (MDR) phenotype exhibited by the bacterial pathogens. Therefore, the aims of this thesis were to investigate MDR through several different approaches. Integrons are important contributors to the MDR profile of nosocomial isolates within Australia, therefore the incidence of integrons was assessed in a collection of 72 conjugative clinical plasmids isolated from E. coli, a cohort of 30 urinary tract infection (UTI) isolates and a cohort of four bacteria producing metallo-beta-lactamases (MBLs). Integrons were found in 63% (45/72) of the conjugative plasmids by polymerase chain reaction (PCR). Sequencing of gene cassette arrays revealed that cassettes of the dfr and aadA families were most common. Within the cohort of UTI bacteria, 37% (11/30) were positive for class 1 integrons, and the dfrA17-aadA5 gene cassette array was most common. The four MBL-producers contained the gene cassette blaIMP-4 found within a class 1 integron which was responsible for the MBL phenotype. An assay based on real-time PCR was also developed to measure the recombination activity of the integron integrase (IntI) enzymes. The existing method of IntI measurement, the in vivo conduction assay, was used as a basis for the development of the real-time PCR assay. Five 59-be from the gene cassettes aadB, orfA, sat2, dfrA1 and aacA4 were cloned as recognition sites used in the real-time PCR assay. IntI1 was the most active integrase and showed an activity of 2.31 ?? 10??-1 when recombining the aadB and orfA 59-be. The highest level of class 2 integrase activity was 2.00 ?? 10-1?? during recombination of the sat2 and dfrA1 59-be, while IntI3 showed its highest recombination frequency of 2.29 ?? 10-1?? when the aadB and orfA 59-be were used. Additionally, the real-time PCR assay was used assess the levels of IntI activity over time. Using this method, the level of recombination as time progressed remained stable at a level of 4.10 ?? 10-2????. MDR was also analysed in 37 Acinetobacter baumannii isolates which were collected from four hospitals in Sydney. Minimum inhibitory concentration (MIC) analysis to 25 antibiotics revealed that all isolates showed a reduced susceptibility to between five and 24 antibiotics. PCR was performed to detect the presence of resistance determinants. Class 1 integrons encoding resistance to aminoglycosides, antiseptics and disinfectants were found in 35 % (13/37) of the isolates. Aminoglycoside resistance genes including aphA1 (12/37), strA (1/37) and strB (22/39) were also found. Resistance to beta-lactams was also observed in all isolates, which correlated with the presence of the ampC and blaOXA-51-like genes. The insertion sequence ISAba1 which provides an alternative promoter leading to increased gene expression was found upstream of the ampC gene in 29 isolates; the same isolates also contained the identical insertion sequence upstream of the carbapenemase resistance gene blaOXA-23. These 29 isolates also possessed the tetracycline resistance gene tetB. All but one of these 29 isolates also contained the gene blaTEM-1. Resistance to quinolones and fluoroquinolones was attributed to the presence of a Ser83-Leu83 gyrA mutation present in 36 resistant isolates. Furthermore, a putative dihydrofolate resistance gene, folA, was found in all isolates. Repetitive extragenic palindromic PCR revealed the presence of seven clonal groups. Overall, this study demonstrated the widespread impact and dissemination of MDR within nosocomial settings in Australia. The use of new assays, such as the real-time PCR assay developed in this thesis, is essential to the understanding of dissemination of antibiotic resistance.

Antibiotic production kinetics of Streptomyces strain JS1 (an isolate selected from an industrial screen for biocontrol activity) and Streptomyces hygroscopicus (a culture collection strain with similar biocontrol activity to JS1) were examined. Growth-associated niphimycin production was observed in both strains during carbon-limited batch culture. Growth associated antibiotic production in carbon-limited medium has not been reported elsewhere and the antibiotic production physiology of biocontrol isolates has not been extensively studied in other laboratories. Increases in biomass and antibiotic production occurred simultaneously in JS1 (24h) and S. hygroscopicus (40h) carbon-limited cultures. Specific growth and antibiotic production rates peaked simultaneously (35h in S. hygroscopicus, 30h in JS1). Examination of the correlation between intracellular protein synthesis rate and niphimycin production rate was consistent with the relationship between these parameters proposed (in our laboratory and elsewhere) for the more frequently reported phenomenon of growth- dissociated antibiotic production. Evidence was obtained which resulted in a hypothesis that the unusual antibiotic production kinetics were a result of the unusually low affinity of JS1 for glucose. A novel approach (multi-compartment nonlinear modelling) to the determination of substrate affinity constants yielded a Ks value of 2.9mM which compares to 7.55muM (i.e. significantly higher affinity) value for Saccharopolyspora erythraea, a species which demonstrates the more common, growth dissociated form of production. Antibiotic production in nitrogen-limited culture was also growth- associated, but this has been reported elsewhere. Work reported here suggests that affinity for nitrogen substrate is significantly lower than that for glucose in S. erythraea (4.45mM compared to 7.55muM) a strain that also exhibits growth-associated antibiotic production under nitrogen limitation. This presumably explains the more growth-associated production kinetics observed in nitrogen-limited cultures. It is tempting to speculate a link between antibiotic production kinetics and biocontrol potential. A micro-organism capable of releasing anti-microbial product in synchrony with cell growth would presumably have more effect in reducing the rhizosphere microflora, prior to colonising the habitat, than a species producing the antibiotic as a secondary metabolite. If this hypothesis is justified, then it may explain the success of JS1 and S. hygroscopicus in the industrial screen. A mutant of JS1, unable to produce niphimycin, displayed diminished biocontrol capability, indicating that niphimycin has a role in the observed biological control effect, in this instance. An attempt to increase the biocontrol effectiveness of JS1 by enhancing niphimycin production in hydroponic and agar tomato culture systems was unsuccessful due to the production kinetics displayed by JS1. Manipulating culture conditions for increased niphimycin production inevitably resulted in increased JS1 growth which was associated with plant death. Electron microscopy suggested that this enhanced growth resulted in excessive colonisation of the root system, possibly resulting in plant death due to root oxygen starvation. The fungal pathogens Phytophthora capsici and Fusarium oxysporum, used as challenge organisms in the industrial screen, had significantly higher affinities for the substrates examined (15muM and < 10muM, respectively for glucose and 22muM and < 38muM, respectively, for nitrate) compared to the affinities of JS1 (2.9mM and 2.4mM, respectively, for glucose and nitrate) indicating that competition for nutrients was unlikely to account for the success of JS1 in the screen. An additional novel concept explored in this work was the use of a fractional factorial medium design procedure (the Plackett-Burman technique) for the attempted identification of nutrients that could be used to simultaneously enhance growth of biocontrol agents whilst inhibiting the growth of target pathogens. Nutritional requirements thus elucidated were compared to those of variant strains of S. hygroscopicus and other Streptomyces species.

Class of 2012 Abstract / Specific Aims: The primary purpose of this study was to evaluate the time of vancomycin pre-operative surgical site infection prophylaxis administration relative to other scheduled antibiotic therapy at a tertiary care, academic medical center. The secondary purpose was to characterize the incidence of adverse events post-surgery that were associated with vancomycin therapy in patients who received both pre-operative scheduled vancomycin therapy and vancomycin for surgical site infection prophylaxis Methods: This descriptive study was a retrospective medical chart review of all patients over the age of 28 days who received vancomycin for surgical site infection prophylaxis between February 2011 and May 2011 at a tertiary care, academic medical center. This study was approved be the Institutional Review Board. The subject population included patients admitted to the hospital for at least 72 hours who received at least 48 hours of scheduled vancomycin (IV), daptomycin or linezolid therapy before index surgery and subsequently received surgical site infection prophylaxis with vancomycin. Main Results: Of the 20 subjects who meet the study inclusion criteria, 18 (90%) subjects received scheduled vancomycin doses within 48 hours prior to surgery, 5 (25%) subjects within 4 hours, and 4 (20%) subjects within 2 hours. No surgical site infections were reported. Conclusions: This was a pilot study to evaluate the timing of vancomycin surgical site infection prophylaxis doses with scheduled vancomycin, linezolid, and daptomycin. No adverse effects associated with surgical site infection prophylaxis were reported but the sample size is small and likely inadequate to detect this potential issue.

Master of Science in Biomedical Sciences / Department of Clinical Sciences / Walter C. Renberg / OBJECTIVE: The purpose of the study reported here was to evaluate pharmacokinetics of cefazolin in dogs receiving a single IV injection of cefazolin (22 mg/kg) and dogs receiving simultaneous IV and IM injections of cefazolin (total dose, 44 mg/kg). METHODS: Twelve purpose-bred Beagles (6/group) were assigned to receive a single injection of cefazolin (22 mg/kg, IV) or simultaneous injections (22 mg/kg, IV, and 22 mg/kg, IM). Interstitial fluid was collected over a 5-hour period using ultrafiltration probes for pharmacokinetic analysis. RESULTS: Mean cefazolin concentration in the interstitial fluid at 1, 1.5, 2, 3, 4, and 5 hours after injection was 39.6, 29.1, 21.1, 10.3, 6.4, and 2.7 μg/mL, respectively, for the IV group and 38.3, 53.3, 46.4, 31.7, 19.1, and 8.9 μg/mL, respectively, for the IV + IM group. The mean area under the concentration-time curve extrapolated to infinity, maximum concentration, half life and time to the maximum concentration was 74.99 and 154.16 h•μg/mL, 37.3 and 51.5 μg/mL, 0.96 and 1.11 hours, 1.28 and 1.65 hours, respectively, for the IV and IV + IM groups. CONCLUSIONS AND CLINICAL RELEVANCE: Cefazolin concentrations in interstitial fluid of dogs were maintained at > 4 μg/mL for 4 hours after a single IV injection and for 5 hours after simultaneous IV and IM injections. Based on these results, simultaneous administration of cefazolin IV + IM 30 to 60 minutes before surgery should provide interstitial fluid concentrations effective against the most common commensal organisms (Staphylococcus spp and Streptococcus spp) on the skin of dogs for surgical procedures lasting ≤ 4 hours.

Class of 2008 Abstract / Objectives: To evaluate changes in parental knowledge regarding antibiotic use and antibiotic resistance with an educational intervention given at elementary school parent-teacher association (PTA) meetings. Methods: This was an analytical pre-test/post-test study of an educational intervention given at two elementary schools in the Phoenix metro area. The primary dependent variable was a knowledge measure, calculated as a total score. The changes between the pre- and post-test total score means were compared using a dependent t-test. The a-priori alpha level used was 0.05. Results: The study sample consisted of 25 participants. Study data were collected between September 2007 and December 2007. The mean (SD) pre- and post-test scores were 33.7 (4.4) and 40.7 (2.7), respectively (p < 0.05). Conclusions: The educational intervention presented at elementary school PTA meetings resulted in a significant knowledge increase regarding the appropriate use of antibiotics when pre- and post-test scores were compared.

The purpose of this investigation is to add to the present day knowledge concerning the presence of antibiotics in additional members of the spermatophyte group of plants.

Infectious disease has always been and will continue to be a heavy burden on human society worldwide. Terrestrial actinobacteria, notable as a source of antibiotics, have been well investigated in the past. In constrast, marine actinobacteria, especially sponge-associated species, have received much less attention and isolates are sparse. With the aim of studying and discovering novel marine actinobacteria, 11 different species of sponges were collected from the Central Red Sea in Saudi Arabia and cultured with three different types of media. 16S rRNA gene-sequencing revealed that among all 75 isolated bacterial strains 13 belonged to the order actinomycetales. These 13 actinomycetes fall into four different families and can be assigned to six different genera. Antibiotic activity tests using disc diffusion assay were performed against Gram-positive bacteria (Bacillus sp.), Gram-negative bacteria (Escherichia coli), fungi (Fusarium sp.) and West Nile virus NS3 protease. Nine strains presented different level of bioactivity against these pathogens. These findings provide evidence that actinomycetes are presented in marine sponges and that they have the potential to be good candidates in the search for new effective antibiotic, antifungal, and antiviral compounds.