Thesis (Ph.D.)--Mississippi State University. College of Veterinary Medicine. / Title from title screen. Includes bibliographical references.

Thesis (M.Sc.(Microbiology)) -- University of Limpopo, 2019 / Salmonella enterica serovar Gallinarum biovars Gallinarum, and Pullorum, Pasteurella multocida and Escherichia coli are among the most important pathogens in poultry and are the causal agents of fowl typhoid, pullorum disease, fowl cholera and collibacillosis in poultry. The present study was designed to identify and determine the distribution of these pathogens in household-raised chickens and their antibiotic and virulence profiles. For this purpose, 40 chickens were bought from household families at Ga-Dikgale, GaMolepo and Ga-Mphahlele in the Capricorn district of Limpopo Province and sacrificed for sampling. Tissues including breast meat, lungs, small and large intestines were harvested from each chicken. Bacteria associated with these samples were cultured in selective bacteriological media followed by biotyping using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) for identification. Out of a total of 160 tissue samples evaluated, E. coli and Salmonella were detected in these tissues. Furthermore, determination of the pathogenic E. coli and Salmonella strains at species level using primer sets that target selected genes of interest in the polymerase chain reaction (PCR) assay was employed. The invA gene, a confirmatory gene for Salmonella species was detected in all the Salmonella isolates using PCR. For the pathogenic E. coli, astA, eae, hlyA, fIiCH7, stxI and the fimbrial genes (F6 and F41) were detected in some of the E. coli isolates recovered from the samples. Disk diffusion test was also performed to determine the antibiotic susceptibility of the bacteria. The results from the current samples reveals that there is a high distribution of Salmonella and pathogenic E. coli in these areas and therefore further epidemiological and identification studies are needed to determine these organisms at species level and investigate their pathogenicity. The antimicrobial susceptibly data generated from this study can be a valuable reference to veterinarians for treating bacterial diseases in poultry.

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Ko Mui Lam. / Thesis submitted in: December 2003. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 84-100). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter A. --- Antibiotic use and resistance --- p.1 / Chapter B. --- Selection of resistant strains by antibiotics --- p.2 / Chapter C. --- Fluoroquinolones --- p.5 / Chapter D. --- β-Lactams --- p.8 / Chapter E. --- Aminoglycosides --- p.9 / Chapter F. --- Salmonella sp --- p.9 / Chapter a. --- Microbiology and clinical significance --- p.9 / Chapter b. --- Antimicrobial susceptibilities --- p.10 / Chapter G. --- Escherichia coli --- p.14 / Chapter a. --- Microbiology and clinical significance --- p.14 / Chapter b. --- Antimicrobial susceptibilities --- p.15 / Chapter H. --- Pseudomonas aeruginosa --- p.18 / Chapter a. --- Microbiology and clinical significance --- p.18 / Chapter b. --- Antimicrobial susceptibilities --- p.18 / Chapter I. --- Objectives --- p.22 / Chapter Chapter 2 --- Materials and Methods --- p.23 / Chapter A. --- Bacterial strains --- p.23 / Chapter B. --- Methods --- p.23 / Chapter a. --- Identification --- p.23 / Chapter i) --- Salmonella --- p.23 / Chapter ii) --- Escherichia coli --- p.24 / Chapter iii) --- Pseudomonas aeruginosa --- p.24 / Chapter b. --- Antimicrobial susceptibility testing --- p.24 / Chapter i) --- Determination of minimal inhibitory concentrations (MICs) of antibiotics --- p.24 / Chapter ii) --- "Determination of the antimicrobial susceptibility of Salmonella sp, Escherichia coli and Pseudomonas aeruginosa by the breakpoint method" --- p.28 / Chapter c. --- Effects of antimicrobial agents on the development of resistant mutants --- p.28 / Chapter Chapter 3 --- Results --- p.32 / Chapter A. --- Antimicrobial susceptibilities --- p.32 / Chapter B. --- Effects of fluoroquinolones on the development of resistance --- p.36 / Chapter a. --- Salmonella sp --- p.38 / Chapter b. --- Escherichia coli --- p.40 / Chapter c. --- Pseudomonas aeruginosa --- p.46 / Chapter C. --- Effects of β-lactams on the development of resistance --- p.49 / Chapter a. --- Salmonella sp --- p.49 / Chapter b. --- Escherichia coli --- p.53 / Chapter c. --- Pseudomonas aeruginosa --- p.56 / Chapter D. --- Effects of aminoglycosides on the development of resistance --- p.60 / Chapter a. --- Salmonella sp --- p.60 / Chapter b. --- Escherichia coli --- p.68 / Chapter c. --- Pseudomonas aeruginosa --- p.68 / Chapter Chapter 4 --- Discussion --- p.76 / References --- p.84 / List of Tables / Chapter I-1 --- Antimicrobial susceptibilities of salmonellae reported in the literature --- p.12 / Chapter I-2 --- Antimicrobial susceptibilities of Escherichia coli reported in the literature --- p.16 / Chapter I-3 --- Antimicrobial susceptibilities of Pseudomonas aeruginosa reported in the literature --- p.20 / Chapter II-1 --- Antibiotics and their solvents --- p.26 / Chapter II-2 --- Antibiotics and their concentrations tested --- p.27 / Chapter II-3 --- Antibiotics and their breakpoint concentration tested --- p.29 / Chapter III-1 --- Susceptibilities of 40 isolates of Salmonella sp to 12 antimicrobial agents --- p.33 / Chapter III-2 --- Susceptibilities of 40 isolates of Escherichia coli to 12 antimicrobial agents --- p.34

Gastrointestinal illnesses have continually become a global public health issue. Exposure to zoonotic food borne pathogens such as Salmonella and diarrhoegenic E. coli either by direct or indirect contact through the consumption of food producing animals is likely an important mode of infection to humans. More so, the use of antibiotics in farm animals similar to those used in humans can select for resistance in bacteria frequently harboured by them. These resistant strains can be passed on to humans through contaminated meat products and water leading to resistant infections with consequences such as prolonged illnesses, treatment failures, and increased morbidity and mortality. In animals, these can lead to reduced productivity. Monitoring the level of resistance among bacteria from animal isolates will help in generating data that could be used to create awareness of their presence in the environment and aid in preventing a potential epidemic in the community. In this study, we investigated the prevalence and antimicrobial resistance profile of Escherichia coli serogroups and Salmonella species in faecal samples collected from pigs in Nkonkobe Municipality in the Eastern Cape Province, South Africa between April – July, 2014. A total of 310 presumptive Shiga toxin producing Escherichia coli (STEC) were confirmed as E. coli spp using polymerase chain reaction (PCR) technique by amplification of the uidA gene, out of which 179 (58%) were confirmed positive. Approximately, serogrougs O157:H7, O145 and O26 made up 24% (n=43), 8% (n=14) and 20% (n=35) of the E. coli population respectively. Only E. coli O26 was positive for stx2 gene in 31% of the isolates harbouring the gene, while the other serogroups were non-pathogenic. Susceptibility of the isolates to 18 antibiotics was carried out in vitro by the standardized agar disc-diffusion method. All the isolates were susceptible to imipenem. Similarly, a relatively high susceptibility was observed in norfloxacin (83-100%), ciprofloxacin (63-100%), gentamycin (77-100%), and chloramphenicol (77-100%). However, all the isolates were resistant to tetracycline and its long acting counterpart oxytetracycline. Resistances observed against other antimicrobials are as follows: ampicillin (84-91%), streptomycin (14-100%), erythromycin (91-100%), ceftazidime (35%). Multiple antimicrobial resistance patterns and indices ranged from 3 to 12 and 0.2 to 0.7 to respectively. Genes encoding resistances to ampicillin (ampC), streptomycin (strA) and tetracycline (tetA) were frequently detected in 50-100%, 22-29% and 40-86% of the resistant isolates respectively. In the other arm of the dissertation, two hundred and fifty eight presumptive isolates of Salmonella were recovered from the faecal samples of pigs. Specific primers targeting serogroups A, B, C1, C2, and D were used to delineate the isolates into different serogroups using PCR. Only serogroup A (n=48) was detected. These isolates were examined for antimicrobial susceptibility by disc diffusion method using 18 antibiotics. The results showed that a large proportion of the isolates were resistant to tetracycline (100%), oxytetracycline (100%), ampicillin (75%), sulphamethoxazole/trimethoprim (75%) and streptomycin (75%). Majority of the isolates exhibited multidrug resistances with the predominant multiple antibiotic resistance (MAR) phenotype being against eleven antibiotics. A high multiple antibiotic resistance (MAR) index in a range of 0.3- 0.6 was observed. The incidence of genes encoding resistance against tetracycline (tetA), streptomycin (stra), and ampicillin (ampC) were 54%, 44% and 61% respectively. These findings reveal that pigs within the Nkonkobe Municipality in the Eastern Cape Province could harbour Shiga toxins and multidrug resistant serogroups of E. coli as well as resistant Salmonella which could be transmitted to humans through the food chain. To ensure public health safety, continuous monitoring and sufficient sanitation in swine industries must be ensured.

Salmonella enterica subtype Typhimurium (S. Typhimurium) is one of many non-typhoidal Salmonella enterica strains responsible for over one million cases of salmonellosis in the United States each year. These Salmonella strains are also a leading cause of diarrheal disease in developing countries. Nontyphoidal salmonellosis induces gastrointestinal distress that is characterized histopathologically by an influx of polymorphonuclear leukocytes (PMNs), the non-specific effects of which lead to tissue damage and contribute to diarrhea. Prior studies from our lab have demonstrated that the type III secreted bacterial effector SipA is a key regulator of PMN influx during S. Typhimurium infection and that its activity requires processing by caspase-3. Although we established caspase-3 activity is required for the activation of inflammatory pathways during S. Typhimurium infection, the mechanisms by which caspase-3 is activated remain incompletely understood. Most challenging is the fact that SipA is responsible for activating caspase-3, which begs the question of how SipA can activate an enzyme it requires for its own activity. In the present study, we describe our findings that the eukaryotic tetraspanning membrane protein PERP is required for the S. Typhimuriuminduced influx of PMNs. We further show that S. Typhimurium infection induces PERP accumulation at the apical surface of polarized colonic epithelial cells, and that this accumulation requires SipA. Strikingly, PERP accumulation occurs in the absence of caspase-3 processing of SipA, which is the first time we have shown SipA mediates a cellular event without first requiring caspase-3 processing. Previous work demonstrates that PERP mediates the activation of caspase-3, and we find that PERP is required for Salmonella-induced caspase-3 activation. Our combined data support a model in which SipA triggers caspase-3 activation via its cellular modulation of PERP. Since SipA can set this pathway in motion without being cleaved by caspase-3, we propose that PERP-mediated caspase-3 activation is required for the activation of SipA, and thus is a key step in the inflammatory response to S. Typhimurium infection. Our findings further our understanding of how SipA induces inflammation during S. Typhimurium infection, and also provide additional insight into how type III secreted effectors manipulate host cells.

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