Phenotypic and molecular characterization of Staphylococcus aureus from mobile phones in Nigeria.

The presence of Staphylococcus aureus, a normal human flora on cellphones of different professionals in Ile-Ife was investigated with a view to determining their antibiotic susceptibility profile and nature of resistance and virulence genes. One hundred swab samples were collected aseptically from mobile phones of various users based on their profession. Surfaces of the mobile phones were swabbed and the streak plate method was used to isolate colonies showing characteristic golden yellow on mannitol salt agar plates. These isolates were further identified using standard microbiological methods. The antibiotic susceptibility of the isolates was determined using Kirby-Bauer's disk diffusion technique. Molecular detection of nuc, mecA and pvl genes in some isolates was carried out by polymerase chain reaction technique. All the 36 isolates obtained in this study were 100% resistant to amoxicillin and augmentin; the isolates also displayed 55.6%, 44.4% and 41.7% resistance to ceftriazone, erythromycin and chloramphenicol, respectively. Based on resistance to oxacillin, prevalence of methicillin resistant Staphylococcus aureus (MRSA) was 11.1%. Only one S. aureus was positive for plasmid analysis. MecA gene was genetically confirmed in four (4) out of the 16 suspected phenotypic MRSA strains, nuc gene was confirmed in all 28 isolates investigated, while there was no pvl gene in the strains investigated. Mobile phones harbor multiple antibiotics resistant S. aureus, which are responsible for important diseases in humans and could be difficult to manage with antibiotics thereby posing serious health risks.

Biosynthesis and Antimicrobial Activity of Pseudodesmin and Viscosinamide Cyclic Lipopeptides Produced by Pseudomonads Associated with the Cocoyam Rhizosphere.

Pseudomonas cyclic lipopeptides (CLPs) are encoded non-ribosomally by biosynthetic gene clusters (BGCs) and possess diverse biological activities. In this study, we conducted chemical structure and BGC analyses with antimicrobial activity assays for two CLPs produced by Pseudomonas strains isolated from the cocoyam rhizosphere in Cameroon and Nigeria. LC-MS and NMR analyses showed that the Pseudomonas sp. COR52 and A2W4.9 produce pseudodesmin and viscosinamide, respectively. These CLPs belong to the Viscosin group characterized by a nonapeptidic moiety with a 7-membered macrocycle. Similar to other Viscosin-group CLPs, the initiatory non-ribosomal peptide synthetase (NRPS) gene of the viscosinamide BGC is situated remotely from the other two NRPS genes. In contrast, the pseudodesmin genes are all clustered in a single genomic locus. Nano- to micromolar levels of pseudodesmin and viscosinamide led to the hyphal distortion and/or disintegration of Rhizoctonia solani AG2-2 and Pythium myriotylum CMR1, whereas similar levels of White Line-Inducing Principle (WLIP), another member of the Viscosin group, resulted in complete lysis of both soil-borne phytopathogens. In addition to the identification of the biosynthetic genes of these two CLPs and the demonstration of their interaction with soil-borne pathogens, this study provides further insights regarding evolutionary divergence within the Viscosin group.