"Of all the numerous drug-resistance mechanisms acquired by staphylococci the most devastatingly effective one was the acquisition of mecA since it provides the bacteria with a wide-spectrum resistance against the largest and most effective group of antimicrobial agents," says Hermnia de Lencastre, Ph.D., senior research associate at Rockefeller and head of the Laboratory of Molecular Genetics at the Instituto de Tecnologia Qumica e Biolgica, Universidade Nova de Lisboa, Portugal, who led the current research effort.
In order to better understand the origin of MRSA, Rockefeller researchers in the Laboratory of Microbiology combined forces with scientists from the Laboratory of Molecular Genetics at the Instituto de Tecnologia Qumica e Biolgica and the State Serum Institute in Denmark. The aim of the group was to identify the nature of the first staphylococcal strain to receive the mecA gene.
The very first MRSA was detected in 1961 in a British hospital within one year of the introduction of the methicillin class of antibiotics into clinical practice.
Shortly afterwards, in 1963, MRSA appeared among staphylococci causing blood stream infections in Danish hospitals. Danish colleagues had saved all blood isolates of staphylococci since 1957, including both drug-susceptible and drug-resistant strains.
Using a combination of various molecular techniques, the researchers were able to obtain a characteristic fingerprint of the first MRSA isolates from the United Kingdom and Denmark.
Interestingly, these early isolates from the two countries proved to be identical. Equipped with this information the scientists then began a search among methicillin-susceptible strains collected in the same era in order to find bacteria with the same molecular portrait as that of the first MRSA strains.