A comparative study of coastal and clinical isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa is a ubiquitous Gram-negative bacterium having a versatile metabolic potential and great ecological and clinical significance. The geographical distribution of P. aeruginosahas revealed the existence of an unbiased genetic arrangement in terrestrial isolates. In contrast, there are very few reports about P. aeruginosa strains from marine environments. The present work was aimed at studying the distribution of P. aeruginosa in coastal waters along the Indian Peninsula and understanding the environmental influence on genotypic, metabolic and phenotypic characteristics by comparing marine and clinical isolates. Of the 785 marine isolates obtained on selective media, only 32 (~4.1%) were identified as P. aeruginosa, based on their fatty acid methyl ester profiles. A low Euclidian distance value (< 2.5) obtained from chemotaxonomic analysis suggested that all the environmental (coastal and marine) isolates originated from a single species. While UPGMA analyses of AP-PCR and phenotypic profiles separated the environmental and clinical isolates, fatty acid biotyping showed overlapping between most clinical and environmental isolates. Our study revealed the genetic diversity among different environmental isolates of P. aeruginosa. While biogeographical separation was not evident based solely on phenotypic and metabolic typing, genomic and metatranscriptomic studies are more likely to show differences between these isolates. Thus, newer and more insightful methods are required to understand the ecological distribution of this complex group of bacteria.

AP-PCR and Antimicrobial Susceptibility Patterns of Fusobacterium nucleatum Associated with Chronic Periodontitis among Patients at Lagos University Teaching Hospital.

Aims: To isolate, identify and evaluate the genetic diversity and antimicrobial susceptibility of F. nucleatum recovered from Nigerian patients with chronic periodontitis. Study Design: Cross-sectional design. Place and Duration of Study: Department of Medical Microbiology and Parasitology, College of Medicine, University of Lagos, between January 2007 and July 2008. Methodology: We analyzed F. nucleatum species recovered from Nigerian patients with chronic periodontitis. Bacterial identification was done using colonial morphology; Grams stain reaction, conventional biochemical tests, API 20-A and Polymerase chain reaction (PCR). The minimum inhibitory concentration (MIC) of 6 antibiotics was determined by agar dilution method on Brucella blood agar while the bacterial genetic diversity was studied using the Arbitrarily Primed-PCR (AP-PCR) method with the arbitrary primer OPA-05. The interrelationship and genetic similarity matrix among the isolates was determined and by Numerical taxonomy and multivariate analysis system (NTSYS-pc) statistical package. Results: We obtained 48 isolates of F. nucleatum from 50 Nigerian patients (28 males and 22 females) with chronic periodontitis. They were susceptible to metronidazole, clindamycin, cefoxitin, tetracycline, amoxicillin and clavulanate. One was resistant to amoxicillin (MIC >32 μg/ml) and produced β-lactamase. The isolates were further placed into five groups (A, B, C, D and E) based on their AP-PCR profile. Conclusion: The AP-PCR analysis showed heterogeneity among strains. By using APPCR, we observed a single β-lactamase producing clone resistant to amoxicillin which eventually formed a distinct group showing that such genetic difference may have contributed to the formation of a separate clone.

Molecular epidemiology profile of methicillin-resistant Staphylococcus aureus in ICU ward / 中国实用内科杂志

Objective To investigate molecular epidemiology profile of methicillin-resistant Staphylococcus aureus (MRSA) in ICU ward.Methods Twenty-five MRSA strains were typed by arbitrarily primed PCR (AP-PCR).Results Ten different AP-PCR patterns (A-G) were found among 25 MRSA strains.Most of MRSA in ICU ward were A and B pulsotype.Conclusion Hospital acquired MRSA is multi-resistant to antibiotics.A and B pulsotype MRSA outbreak occures in ICU ward.