1) Nitrapyrin was less inhibitory to Nitrosomonas europaea in soil culture than in liquid batch culture.2) In the course of liquid batch culture studies, 3 strains of N. europaea were isolated which exhibited differing responses to nitrapyrin. All 3 strains however, were inhibited by 0.5 ppm nitrapyrin and stationary phase cells were found to be less sensitive than exponentially growing cells. 3) 6-chloropicoline, a hydrolysis product of nitrapyrin, was found to inhibit exponentially growing but not stationary phase cells. 4) Cells of N. europaea adhered to glass slides and during the initial stages of colonisation cells were not protected from the inhibitory effect of nitrapyrin. Once cells had become established at the solid/liquid interface there was a significant reduction in the specific growth rate compared with freely suspended cells and 0.5 ppm nitrapyrin no longer inhibited growth. 5) The specific growth rate of cells detached from the surface of a glass slide was not significantly different from that of cells adhered to the surface but significantly less than the specific growth rate of freely suspended cells. Detached cells were not significantly inhibited by 0.5 ppm nitrapyrin. 6) In the presence of montmorillonite, vermiculite and ammonia-treated vermiculite (ATV), growth of N. europaea occurred in two distinct growth phases. All three clay types reduced the inhibitory effect of nitrapyrin and inhibition was only observed during the second growth phase. In the presence of a fourth clay type, illite, growth occurred in one phase only and there was no significant reduction in inhibition by nitrapyrin. 7) Addition of Cu2+ and A13+ enhanced inhibition of N. europaea by nitrapyrin in liquid batch culture. 8) Growth of N. europaea at sub-optimal rates in chemostat culture reduced the sensitivity of cells to nitrapyrin. Productivity increased with increasing nitrapyrin concentrations and ammonia oxidizing activity per cell increased following addition of 0.5 ppm and 1.5 ppm nitrapyrin to steady state cultures. 9) Therefore the clay content of soils and the physiological state of N. europaea may reduce the effectiveness of nitrapyrin when applied in the field.

The KefB and KefC systems of E. coli are two separate potassium efflux systems that are regulated by glutathione and specific glutathione metabolites. The aims of this study were to clone and sequence the E. coli kefB structural gene and to investigate the subunit stoichiometry of the E. coli KefC protein. A further objective was to determine the distribution of the KefC class of transport system in a range of bacterial species, with the ultimate aim of cloning the kefC homologue from a highly divergent organism. Attempts to clone the kefB gene by various strategies proved unsuccessful; possible explanations for this are discussed. Analysis of the suppression of a kefC leaky mutation by plasmids bearing varying lengths of the wild-type kefC gene indicated that the mutant and wild-type KefC proteins interact in the membrane to form a structure that has intermediate properties. These observations are consistent with KefC functioning as an oligomer. Using a variety of techniques, it was demonstrated that the KefC class of transport system is widely distributed among Gram-negativespecies but is absent from all the Gram-positive bacteria tested with the exception of Staph. aureus. In addition the kefC homologue from Er. carotovora was cloned and DNA sequencing initiated. The cloned Er. carotovora kefC gene product was able to suppress an E. coli kefC leaky mutation, thus providing further evidence that KefC exists as an oligomer.

SUMMARY This study retrospectively analysed the bacteriology of 226 patients who were admitted, with acute complicated sinusitis, to the University of the Witwatersrand’s ENT complex over a 5-year period, between the 1st January 2002 and 31st December 2006. There were 159 male and 67 females (ratio 2.4:1) aged between 1 and 74 (mean 16.5 ± 0.7) years. 116 (51.3%) patients were 15 years and younger and 110 (48.7%) were above the age of 15 years. All 226 patients had one or more of an orbital, soft tissue or bony complication and underwent open sinus surgery by way of an external frontoethmoidectomy approach (or ethmoidectomy) with maxillary sinus puncture and sinus washout. Intracranial complications were present in 37 (16.4%) patients of whom 12 required drainage of a subdural empyema and, one required drainage of a brain abscess. 233 microorganisms were isolated for analysis from positive cultures obtained from 163 (72.1%) patients (1.4 isolates per specimen) and 63 (27.9%) cultures were negative. Aerobic and facultative anaerobes accounted for 199 (85.4%) of the isolates whilst anaerobes accounted for 31 (13.3%) and fungi for 3 (1.3%). 107 (65.4%) of the positive culture specimens were monomicrobial whilst 56 (34.6%) contained 2 to 4 different species of microorganism. The proportion of anaerobes was notably higher (p<0.05) polymicrobial specimen than in monomicrobial specimen.The most commonly isolated aerobic microorganisms were Streptococcus milleri (18.5%), Staphylococcus aureus (12.4%), β-haemolytic streptococci groups A, C, F, and G (10.3%), coagulase negative staphylococcus (8.6%) and Haemophilus influenzae (8.6%). In contrast, Streptococcus pneumoniae (2.6%) and Moraxella catarrhalis (0.4%) were not major pathogens. Peptostreptococcus (6.4%) and Prevotella (4.7%) species were the most common anaerobes. The profile of isolates was not influenced by gender or by the presence of intracranial complications. However, age and location did have a significant (p<0.05) impact. Haemophilus influenzae was more significant (p<0.05) in patients aged 15 years and younger. Streptococcus milleri was the most common isolate (28.3%) at the Chris Hani Baragwanath Hospital but ranked 5th (2.3%) at the Johannesburg Hospital. β-haemolytic streptococci and coagulase negative staphylococcus ranked 1st (20.8%) and 2nd (14.8%) respectively at the Johannesburg Hospital but only 4th (4.8%) and 5th (2.8%) respectively at the Chris Hani Baragwanath Hospital. Penicillin, ampicillin and erythromycin were effective against Streptococcus milleri, β-haemolytic streptococci, Streptococcus pneumoniae and streptococcal species. Cloxacillin was effective against Staphylococcus aureus and coagulase negative staphylococci. Methicillin-resistant Staphylococcus aureus was isolated in 3 patients (1.3%). Haemophilus influenzae was resistant to ampicillin in 22.2% cases in which it was the sole pathogen.

Introduction Bacterial vaginosis (BV) is a highly prevalent vaginal infection which poses a significant public health burden in Sub-Saharan Africa (SSA) due to its association with HIV, other STIs and several gynaecological and obstetrical complications. The aim of this study was to explore the underlying and proximate factors associated with BV and the relationships between them. Materials and Methods This study was a cross-sectional secondary analysis of the data collected during the Microbial Development Program (MDP) 301 trial. Logistic regression and structural equation modelling were used to test for the associations between BV and the explanatory variables and to test for the direct, indirect and total effects of the variables on BV. Results A total of 2 470 women were included in the analysis and of these 2 203 were aged 40 and below. The majority of them were unemployed at 72% and 51,8% were in the lowest socio-economic level. The baseline prevalence of BV was 40.5%. In the logistic regression, high socio-economic level (AOR=1.66; 95% CI 1.04-2.64) and using a condom during their last sexual encounter (AOR 0.82; 95% CI 0.69-0.97) were associated with BV infection. The STIs significantly associated with BV infection were: Herpes Simplex Virus 2 (HSV2) (AOR=1.31; 95% CI 1.10-1.56), trichomoniasis (AOR=2.68; 95% CI 1.97-3.64) and chlamydia infection (AOR 2.02; 95% CI 1.61-2.62). In the structural equation modelling (SEM) high socio-economic status had a positive direct effect on BV infection (beta=0.12, OR=1.14).Condom use during the last sex act had a negative direct effect on BV (beta=-0.043, OR=0.96). The presence of T.vaginalis, HSV2 or chlamydia infection had significant positive effects on BV infection. Conclusions Sexual behavioural factors and the presence of STIs were significantly associated with BV. The SEM analysis showed the interaction of contraceptive use and sexual behavioural factors. No interaction between the STIs and sexual behaviour could be demonstrated in this study.

Leptospirosis is a zoonosis of ubiquitous distribution and causes a wide spectrum of disease. Burkholderia species are important plant and human pathogens. Little or no investigation has been performed on any clinically-relevant Burkholderia or Leptospira species in Johannesburg. Environmental samples were taken from different sites in Johannesburg along the Jukskei River. These were subjected to culturing for Burkholderia spp. and polymerase chain reaction (PCR) for Burkholderia and Leptospira spp. Human serum, animal serum and kidney samples were also subjected to PCR for both organisms. A Leptospira IgM ELISA was also performed on human serum samples. More Burkholderia spp. were isolated by culture from soil samples than water samples. The PCR yielded a significantly higher PCR positive from soil samples (p = 0.015). There was a high prevalence of pathogenic Leptospira spp. in soil samples. The ELISA yielded only 7.8% (26/332) positive samples. There were no human or animal positive PCR results for either organism. There is an environmental presence of both leptospires and Burkholderia in the area sampled. More studies are needed to establish how both organisms might affect patients with compromised immune systems, and how often both infections are incorrectly or under-diagnosed.

Introduction Analysis of surveillance data on bacterial respiratory pathogens most commonly causing bacteraemia and meningitis may be useful to measure the impact of vaccination, monitor antimicrobial resistance emergence and document changes in disease epidemiology. Materials and methods Active, laboratory-based, national surveillance for invasive Haemophilus influenzae, meningococcal and pneumococcal disease in South Africa was conducted. Isolates, cultured from normally sterile sites, were submitted for phenotypic and genotypic characterisation. Trends are described and univariate and multivariable models were used to assess differences among groups. Results Following the introduction of H. influenzae serotype b conjugate vaccine (HibCV) in 1999, the number of Hib cases reported for infants <1 year decreased by 65%, from 55 cases in 1999-2000 to 19 cases in 2003-2004. Despite high HibCV coverage, rates of Hib disease in children <5 years then increased from 0.7 per 100,000 population in 2003 to 1.3/100,000 in 2009. Among 263 Hib episodes, 135 (51%) were classified as vaccine failures and 53% of these occurred among children who were not HIV infected. An investigation of meningococcal disease in Gauteng, revealed rates of disease which increased from 0.8/100,000 in 2000 to 4.0/100,000 in 2005; the percentage due to serogroup W135 increased during this time from 7% (4/54) of cases to 75% (221/295). Overall case-fatality ratios doubled from 11% in 2003 to 22% in 2005. Our investigations revealed that the expansion of the Hajj clone explained the emergence of serogroup W135 during this time, as 95% of W135 isolates (285/301) were identified as one clone by pulsed-field gel electrophoresis and seven representative strains belonged to the ST-11/ET-37 complex. Among invasive pneumococcal disease (IPD) cases, 12 levofloxacin-non-susceptible pneumococci were identified in children <15 years, and were found to be associated with a history of tuberculosis (TB) treatment and nosocomial IPD in two treatment centres for multidrug-resistant TB (MDR TB). From 2003 through 2008, prior to pneumococcal conjugate vaccine (PCV) introduction, among IPD cases in children <5 years, 58% (3849/6668), 65% (4314/6668), and 85% (5669/6668) of cases and 61% (455/751), 64% (482/751), 82% (616/751) of deaths were due to serotypes included in 7-valent PCV (PCV-7), PCV-10 and PCV-13, respectively. PCV-13 had significantly higher coverage for isolates from blood culture than for isolates from cerebrospinal fluid: 3882/4531 (86%) vs. 1670/2009 (83%), p=0.009, but only differed by 3%. An analysis of risk factors revealed the relative risk of IPD was 21-fold (95% CI, 19–24) and 34-fold (29–41) greater in HIV-infected compared to HIV-uninfected children in the <1 year and 1–4-year-old age groups, respectively. Discussion and conclusions After initial reductions in Hib disease, vaccine failures, occurring in both HIV-infected and -uninfected children, comprised half of the rise in Hib disease detected 10 years after national introduction of Hib vaccine, given as three doses without a booster. These data contributed to the decision to add a booster dose of Hib vaccine in South Africa in 2009. Continued surveillance of meningococcal serogroup W135 revealed evidence that this serogroup had become endemic in Gauteng causing more severe disease than the previous predominant serogroup A strain. Paediatric fluoroquinolone use for MDR TB led to the emergence and nosocomial spread of levofloxacin-non-susceptible pneumococci. Existing pneumococcal vaccine formulations have the potential to prevent most cases and deaths from IPD among HIV-infected and -uninfected children in South Africa. Surveillance of pneumococcal meningitis may provide representative data for monitoring the impact of PCV.

Vita. / Digitized by Kansas Correctional Industries

No description available.

Understanding bacterial adhesion and biofilm formations on abiotic surfaces are important biological processes that affect the growth of bacteria, with its far-spreading impacts on in everyday life, either as a benefactor or as an inhibitor. To study these bacterial interactions, tools to probe these interfaces are also important to provide further means for discovery of the adhesion mechanisms. In this thesis, a customized imaging platform was developed, utilizing brightfield microscopy to study E. coli K12 on silica surfaces over the stages of bacteria growth. Results observed bacteria adhering onto silica surfaces in a preferential pattern to already existing bacteria-adhered colonies. This suggest that bacteria, once adhered to the surface, enhance attraction of other planktonic bacteria. The platform was designed to enable concurrent Raman measurements, with further optimization required in order to enhance the Raman signals from individual cells. Results from this study provide strong evidence to link changes in interfacial water structure with previous surface vibrational spectroscopy experiments, where the surface coverage of bacteria was found to reach a maximum earlier in the stages of growth compared to the surface water response, indicating that adhesion alone is not the primary contributing factor to modification of the surface microenvironment. / Graduate

Graduation date: 2001