Random amplified polymorphic DNA typing of clinical and environmental Aeromonas hydrophila strains from Limpopo province, South Africa.

The aim of the present study was to determine the genetic relatedness of strains isolated from diarrhoeal stool and water specimens collected from water-storage containers from different geographical areas in the Limpopo province. In total, 32 Aeromonas strains isolated from stool specimens collected from HIV/AIDS patients suffering from gastroenteritis and their household drinking-water stored in 20-L and 25-L containers were analyzed by random amplified polymorphic DNA PCR (RAPD). The RAPD fingerprints obtained proved reproducible when repeated on three different occasions using whole-cell DNA isolated from the Aeromonas strains. In total, 12 unique RAPD fingerprints were found. The results revealed a tendency of the isolates to cluster according to their origin of isolation (best-cut test 0.80 and bootstrap values >50%). However, a certain degree of similarity was also observed between isolates of water sources and clinical sources which indicated genetic relatedness. There were also genetic similarities between the clinical and the environmental strains of Aeromonas spp. isolated from different geographical areas. This study has demonstrated the genetic relatedness of Aeromonas hydrophila isolates from household drinking-water and clinical sources in South Africa, which may be due to cross-contamination from water to patients or vice-versa. This observation is of public-health significance, particularly in the era of HIV/AIDS. This study points to the importance of monitoring and evaluating infection-control measures for improved hygiene and to prevent cross-contaminations.

Antibiotic Synergy Profiles of Multidrug-Resistant - Pseudomonas aeruginosa in a Nosocomial Environment

Pseudomonas aeruginosa is one of the most common nosocomial pathogens in intensive care units (ICUs); with an increased prevalence of multidrug resistance in nosocomial infections. This study aimed to determine antibiotic synergy profiles of multidrugresistantP. aeruginosa originating from ICU patients in a teaching hospital in Pretoria; South Africa. Susceptibility studies and in vitrosynergy testing were performed; utilising agar dilution and Etest methodology; respectively. Susceptibility studies revealed 94of isolates exhibiting resistance to more than three anti-pseudomonal agents tested. Results from antibiotic synergy studies suggested that cefepime (p0.0001) or meropenem (p0.0001) in combination with amikacin are possible treatment options available in this specific setting

GES-2, a class A beta-lactamase from Pseudomonas aeruginosa with increased hydrolysis of imipenem.

Pseudomonas aeruginosa GW-1 was isolated in 2000 in South Africa from blood cultures of a 38-year-old female who developed nosocomial pneumonia. This isolate harbored a self-transferable ca. 100-kb plasmid that conferred an expanded-spectrum cephalosporin resistance profile associated with an intermediate susceptibility to imipenem. A beta-lactamase gene, bla(GES-2), was cloned from whole-cell DNA of P. aeruginosa GW-1 and expressed in Escherichia coli. GES-2, with a pI value of 5.8, hydrolyzed expanded-spectrum cephalosporins, and its substrate profile was extended to include imipenem compared to that of GES-1, identified previously in Klebsiella pneumoniae. GES-2 activity was less inhibited by clavulanic acid, tazobactam and imipenem than GES-1. The GES-2 amino acid sequence differs from that of GES-1 by a glycine-to-asparagine substitution in position 170 located in the omega loop of Ambler class A enzymes. This amino acid change may explain the extension of the substrate profile of the plasmid-encoded beta-lactamase GES-2.