The first whole genome analysis of a Staphylococcus aureus collection recovered from carriage in an African country has just been published by a team of European and African researchers, including ITQB NOVA’s Laboratory of Molecular Genetics and the Escola Superior de Saúde da Cruz Vermelha Portuguesa. The analysis covers work developed for almost 25 years, when the team led by ITQB NOVA’s researcher Hermínia de Lencastre did the first surveillance study on S. aureus in Cape Verde hospitals. At the time, no isolates of methicillin-resistant S. aureus (MRSA) were found – a situation that has substantially changed since then.
S. aureus is a major human colonizer which is able to turn into a pathogen under disrupted host immune barriers, being responsible for a wide variety of infections, ranging from mild skin and soft-tissue infections to life-threatening conditions. Its high capacity to acquire antimicrobial resistance and virulence led to the emergence of multidrug resistance strains such as MRSA, identified as one of the current major bacterial threats worldwide. MRSA was responsible for 34.8% of S. aureus invasive infections reported in Portugal in 2019, far above the average European prevalence of 15.5%. Therefore, surveillance studies on MRSA prevalence and phenotypic and genotypic characterization of the isolates are of major importance for the design and implementation of effective infection control programs. In addition, individuals nasally colonized by S. aureus are at major risk for infection, while asymptomatic carriers could represent major reservoirs of resistant bacteria in the population.
Prevalence rates of MRSA colonization in low- and middle-income countries as the Portuguese speaking African countries (PALOP), with a close demographic and economic relationship to Portugal were, for many years, almost inexistent. The team led by Hermínia de Lencastre has been devoting efforts to shed light on this subject since 1997, when the first surveillance study was carried out in Cape Verde hospitals, under on-site screening supervision of Marta Aires de Sousa, a member of the ITQB NOVA research team. “Patients and health care workers were nasal screened for S. aureus carriage, but no MRSA isolates were identified at that time“, explains Hermínia de Lencastre.
Additional screenings were performed in Cape Verde hospitals in 2013 and 2014, under the scope of an FCT funded project coordinated by Marta Aires de Sousa, chairman of direction board of Escola Superior de Saúde da Cruz Vermelha Portuguesa - Lisboa, in collaboration with Hermínia de Lencastre and Teresa Conceição from ITQB NOVA. Surveillance was extended to other PALOP countries, São Tomé and Principe (STP) and Angola, as well as East Timor. “Among a total of 2,065 nasal swabs recovered, the MRSA prevalence was very high in Angola (61.6%), moderate in STP (25.5%), low in Cape Verde (5.6%), and null in East Timor. Project results were transmitted to the PALOP local infection control commissions and rooted infection control strategies”, explains Marta Aires de Sousa.
With the availability and extraordinary potential of whole genome sequencing on the epidemiology of S. aureus, an in-depth characterization of the unique S. aureus collection recovered from Cape Verde in the three surveillance periods (1997, 2013 and 2014), was performed. The study published in the Journal of Global Antimicrobial Resistance described the first whole genome analysis of a S. aureus carriage collection obtained during an extended period of time from an African country. “We found a high genetic variability among S. aureus carriage isolates, with the detection of 27 sequence types(ST) and three primary genetic clusters associated to lineages ST152, ST15 and ST5, commonly found in S. aureus infections occurring not only in Africa, but worldwide”, explains Teresa Conceição.
The prevalent MRSA lineage reported in Cape Verde, ST5-VI, was described for the first time in a Portuguese Pediatric hospital in the early 1990s, by the ITQB NOVA team. This MRSA ST5-VI lineage was recovered consecutively (2013 and 2014) from the same healthcare workers over a large period of time, evidencing that healthcare workers may act as reservoirs and constitute transmission routes of MRSA in Cape Verde hospitals. Moreover, the genetic analysis that was performed unveiled additional MRSA adaptation and evolution trends, namely the acquisition and/or loss of central multi-drug resistance genetic elements as blaZ gene, predicting the establishment of MRSA multidrug-resistant lineages in Cape Verde.
This study enhances the global understanding of the evolution and antimicrobial adaptation of the first MRSA isolates identified in Cape Verde. Although antimicrobial usage is still limited, there is a progressive and worrying increase of multidrug resistance leading to the urgent implementation of additional intervention measures to constraint antimicrobial drug resistance.
The research was developed in collaboration with researcher Marco R Oggioni from the Department of Genetics and Genome Biology, University of Leicester (Leicester, UK) together with researchers and medical doctors from the Cape Verde hospitals and Cape Verde University. The study was supported by the UK Academy of Medical Sciences Global Challenges Research Fund Networking Grants, FCT (Fundação e Ciência e Tecnologia), and performed within the projects funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (funding MOSTMICRO Research Unit) and by ONEIDA project co-funded by FEEI - “Fundos Europeus Estruturais e de Investimento” from “Programa Operacional Regional Lisboa2020”.
Journal of Global Antimicrobial Resistance