Staphylococcus aureus ( MRSA and CA-MRSA strains ) in South ! " # $ % & ' ( ) & * " + '

Background: In the last few years, 3 different strains of MRSA have emerged: Community-associated Methicillin-resistant S. aureus (CA-MRSA), Hospital-associated (HA-MRSA), and Livestock-associated (LA-MRSA). The most common CA-MRSA strain is USA 300 lineage. In Brasil, this superbacteria is an important public health problem, once they are associated with severe infections (sepsis, shock and osteomyelitis), high mortality rates (including babies) and low response to usual treatments. Aim: To review attempts to compare CA-MRSA strains in South America and propose an interconnection with patterns of North America and worldwide strains. Methods: Non-systematic review. Findings:!"#$%&'$()(*$+,)!,-%!.&-(/0#$-*!%&1-$/$(-2!3&4&! used to compare different strains in different continents. Thus, we could determine ST30 as the most common lineage in the Brazil and South America, USA 300 lineage as the most common in North America and ST80 as the most common in Europe. Conclusion: MRSA is a seriously public health problem in Brazil and worldwide. In few years scientist will need a better understand of bacteria-derived factors that participate in enhanced MRSA pathogenesis & host susceptibility. Also, scientists will need to improve tools for an early diagnosis and they will need to enhance preventative/therapeutic modalities. However, new challenges will keep emerging.


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Staphylococcus aureus is a Gram-positive bacteria and it is a pore-forming toxic molecule producer.The leading cause of human bacterial infections worldwide usually lives as a commensal organism in humans and it affects asymptomatically 1/3 of human population.Nostrils are the most common colonization site, but there are known extra-nasal sites (e.g.throat, axilla, groin, perirectal area).[3] Transmission occurs via direct contact with the organism, in other words, skin-to-skin contact with colonised or infected individuals.Fomites and sexual transmission are other possible ways to get infected.The main predisposing risk factors are skin trauma, infection drug use, and poor personal hygiene.According to CDC, there are 5C-risk factors: crowding, contact, contaminated, compromised, and cleanliness. 1,2mptoms varies widely in severity.The most common is skin and soft tissue infections (SSTI) -abscesses and cellulitisresponsible for around 90% of the worldwide cases.Invasive infections can cause bacteraemia, leading to complex cases and syndromes (e.g.Purpura fulminans, Myositis, Necrotising fasciitis, Osteomyelitis, Necrotizing pneumonia and Endocarditis).In the past 60 years, MRSA strains started an age of antibiotic resistance epidemic.Normally associated with nosocomial infections, besides this notion has changed greatly in the past few years.[3] In the last 20 years, MRSA became hyper-virulent.Thus, it became multidrug resistant.The pandemic clones ST5, ST8, In 2000, a different lineage emerged CC8 or "USA300".The latter quickly eclipsed MW2 (USA400), becoming the primary cause of skin and soft tissue infections (SSTI) in the US, and greatly increasing the burden of community MRSA carriage and transmission.During the same period, genetically distinct CA lineages were reported from numerous countries. 4 the last few years CA-MRSA became a health problem worldwide.For instance, in the period of 2000-2003, it was responsible for more than 50% of USA infections while in France it was responsible for just 1-3%.The most used genotyping methods are: 12 1.Spa sequence typing: sequence polymorphism in the variable X region of the spa gene for S. aureus surface protein A. Source: Prepared by the author.
4. Macrorestriction pattern analysis: analysis of restriction polymorphisms of the whole chromosome.

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There are around 20 distinct genetic lineages of MRSA around the world.The 5 global predominant are ST1-IV (WA-1, 86$ 67,9 86$ 67,9 6RXWK :HVW 3DFL¿F clone), St 59-V (Taiwan clone), ST80-IV (European clone).7KHUH DUH VWUDLQV FODVVL¿HG DV SDQGHPLF 67,9 86$ OLQHDJH 67,9 6RXWK :HVW 3DFL¿F FORQH 6:3 )LJXUH 2). 4,6,13he most prevalent area of infection by MRSA is the EUA.The most prevalent strain is "USA300" lineage.A reasonable explanation to this condition are the different social panoramas between EUA and Europe.The USA infection panorama is homogeneous with a predominant lineage, while in Europe there is a heterogeneous panorama once none lineage predominates.However, ST80-IV is the most common lineage in Europe. 4,13The prevalence of MRSA worldwide could be divided in 3 main zones: Americas and Asia (highest prevalence), East Europe (intermediate prevalence) and West Europe (low prevalence). 4,6,13e decline of prevalence of MRSA worldwide could be divided in 3 main zones: Americas and Asia (low decline), East Europe (intermediate decline) and West Europe (high decline).This data contribute to a social analysis of the infection.Nations with more precarious health systems are less OLNHO\ WR ¿JKW DQG FRQWDLQ 056$ LQIHFWLRQ ZKLOH GHYHORSHG nations where MRSA is combated quickly and effectively. 4,6,13 South America, the 2 predominant HA-MRSA clones are: Brazilian clone (sequence type ST239) -related to Russian clones, which bears the SCCmecIII (MRSA0ST239-III), and the Chilean/ Cordobes clone (MRSA-ST5-I).However, USA300 has disseminated through Latin America as the main cause of CA-MRSA.In Uruguay and Brazil, USA 300 CA-MRSA isolates have been reported that display distinct genetic characteristics (MRSA-ST30-IVc).Interestingly, this strain, recently dubbed "USA300-LV" (Latin America Variant) appears to be a separate lineage which may be distinguished from the North America strain (USA300-0114) by various molecular features including SCCmec subtype (IVc) and absence of ACME.The dissemination of CA-MRSA isolates in South America hospital environments was ¿UVW UHSRUWHG LQ &RORPELD LQ ,Q WKH $QGHDQ FRXQWULHV (Colombia, Venezuela, Peru, and Ecuador), the CA-MRSA isolates present similar characteristics to the USA300 clone, including MRSA-ST8-IVc-E, PVL positivity, and multisusceptibility. 10,14 In the USA, the predominant CA-MRSA clone is ST8+ SCCmecIVa -PVL positive or USA300.Meanwhile, a few years ago USA400 was the predominant clone, but after a clonal expansion it became USA300.ST1+ or USA400 is still predominant in northern areas of America (e.g.Alaska and Canada), while USA300 is predominant in USA itself.USA300 lineage cause the majority of complicated SSTI worldwide, it has a high mortality and high treatment failures and could be considered pandemic and hypervirulent.
The fast emergence of USA lineage comes from the combination of 3 main elements: newly acquired virulence genes (gene acquisition), altered expression of common virulence determinants (altered gene regulation), and In Asia, the 2 predominant clones are ST59-IV (USA1000) and ST59-V (Taiwan clone).However, Asia is a very diverse region with many different clone: ST22-IV & ST772-V in India; ST59-V in Taiwan, Vietnam and China; ST72+ in Korea; ST121+ and ST834+ in Cambodia; and ST30+ in 6RXWK 3DFL¿FD $XVWUDOLD DQG 5XVVLD ,W DOVR FRPPRQ WR $VLDQ strains be PVL negative. 2,4,13,16In Japan, the most prevalent clone is the Japanese ST8 SCCmecIVl (designatedST8 CA/J).7KH ¿UVW FDVH ZDV UHSRUWHG LQ 7KH -DSDQHVH FORQH LV very similar to the USA clone ST8 SCCmecIVa (USA300), but with marked diversity in accessory genes.For example, ST8 CA/J possessed enhanced cytolitic peptide genes, but lacked the PVL phage and ACME, unlike USA300.From a genetic point of view, ST8 CA/J is a geographic variant of ST8 CA-MRSA, which is one of the most disseminated lineages.However, ST8 CA/J -PVL negative is the most common FORQH VRPH 39/ SRVLWLYH VWUDLQV ZHUH LGHQWL¿HG LQ -DSDQ OLNH ST6 and ST59.

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RSA is a seriously health problem across the globe because: lack of knowledge on the genetic control of the bacteria, its high mortality and its multidrug resistance.Thus, in the next years, researchers should focus on better understand the bacteria-derived factors that participate in enhanced MRSA pathogenesis & host susceptibility; improve tools for an early diagnosis; enhance preventative and therapeutic modalities.Otherwise, we will face an increased number of infections, new antibiotic resistance and low positive clinical outcomes.Work on developing research for better understanding of the genetic mechanisms involved will bring the possibility of creating vaccines or immunotherapies able to contain the EDFWHULD PRUH HIIHFWLYH DQG VSHFL¿F ZD\ However, new challenges remain emerging.For instance: drug resistance to the most potent antibiotics actually used (e.g.vancomycin, daptomycin, linezolid); interactions between HA-MRSA, CA -MRSA, LA -MRSA resulting in possible new and more resistant strains; spread by new reservoirs; pandemic clones and not genotyped strains.Thus, scientist will need to continuously develop new methods to identify markers of hypervirulence, transmissibility and persistence; and new/more effective treatments.

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would like to thank Dr Cristiane Cunha for her support during my Microbiology monitoring and in this thesis process.I would like to thank Dr Mal Horsburgh and Dr Viv Dillon for their extraordinary support during this year abroad and in this thesis process.Also, this project would have been impossible ZLWKRXW WKH ¿QDQFLDO VXSSRUW RI WKH 3URJUDP 6FLHQFH ZLWKRXW Borders-UK (SwB-UK) and the National Research Council (CNPq-BR).

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[1][2][3]nd ST45 are nowadays one of the most seriously health problems worldwide.[1][2][3] 1,9,10ock-associated Methicillin-resistant S. aureus (LA-MRSA) or CC398 (most common strain) is related to MRSA in animals.It is widely disseminated among pigs in European countries with high-density pig farming (The Netherlands, Denmark and Germany), but it also affects veal calves, horse and dogs.The main concern about those strains is a possible adaptation to human, as already related in some Chinese Hospitals.Thus, animals will be an endless reservoir of infection. 1,2,6aPIs), plasmids and transposons, SCCmec, SCC (non-mec), genomic islands.They are more prevalent among the USA lineage.Therefore, MGE are one of the possible factors responsible for the success of adaptation of those clones across the globe.1,9,10 10Zh>ES.aureus genome structure has 3 principal components: backbone of core genes, dispersed core of variable genes, and mobile genetic elements.The backbone of core genes is founded in all strains and they are highly conserved.Core variable genes (CV) are dispersed through the backbone composing a high variable group.MGE are constantly transferred and they are especially related to acquisition of PBP-2, an alternative penicillin-binding protein encoded by mecA and harboured in a genetic element: Staphylococcal cassete chromosome (SCCmec) that encodes resistance to methicillin.Depending on the particular SCCmec type, these mobile islands can confer multidrug-resistance. 1,7-10 MRSA defence is based in 2 mains strategies: Immune evasion and Virulence factors.The main components related to Immune evasion are: cytotoxins, immunomodulatory proteins, protease and factors that prevent immune cell recognition and killing (protein A/ capsule/ catalase).Panton-Valentine leucocidin is a bicomponent pore-forming toxin located in prophage phiSA2pvl and encoded in genes lukS-PV and lukF-PV, responsible for induce necrosis and apoptosis in leukocytes by binding to host membranes and (arcC, aroE, glpF, gmk, pta, tpi and yqiL) yielding unique sequence types (STs).STs sharing identity at the majority of these loci are grouped into Clonal Complexes (CCs) encompassing related lineages of MRSA.Scientist discovered PRVW 056$ GLVHDVH ZRUOGZLGH ZDV FDXVHG E\ ¿YH PDMRU CCs: CC5, CC8, CC22, CC30 and CC45.35.Staphylococcal cassette chromosome (SCCmec)There are 8 SCCmec types (I-VIII).The most common is SCCmecIV.SCCmec types could be divided in 2 main groups: 6&&PHF ,,,, DQG 6&&PHF,99 7KH ¿UVW JURXS LV UHODWHG to HA-MRSA: large length, little movement and contain additional drug resistance to several classes of antibiotics.The second group is related to CA-MRSA: small length, spread easily, more mobile and drug resistance only to beta-lactam.106.Toxins: alfa-toxin & Phenol-Soluble Toxins (PSM)Newly acquired sequence of genes that can move around in genome and transferred between strains by horizontal gene transfer leading to selective advantage.MGE are determinants of colonisation/transmissibility rather than virulence.Examples: bacteriophages encoding toxins, pathogenicity and composite islands ( 15fferent from the USA, MRSA infections are less prevalent DQG PRUH KHWHURJHQHRXV LQ (XURSH ,Q WKH ¿UVW (XURSHDQ case was reported in Greece (country where MRSA infections are more prevalent in Europe).The most common clone in Europe is ST80+, but in certain areas there are other clones.SCCmecIV in Russia.The Russian clones are divided according to geographic areas: ST239 is more prevalent in European and Eastern Russia, while ST8 is more prevalent in Siberia Russia.The clones present in Siberia Russia are very similar to Brazilian clones.It could be possible because of migration of strains and transference of genetic material.15 3Q SURWHLQ VHTXHQFHV WKDW LQFUHDVH ¿WQHVV VHTXHQFH polymorphisms -protein sequence divergence).However, it is OLNHO\ WKDW QR VLQJOH H[SODQDWLRQ FDQ VXI¿FH DQG WKDW 056$ represents a continuously emergent phenomenon driven by multi-factorial interactions between the classic triad of host, pathogen, and environment.3 1assive immunization with antibodies to sequester main virulence determinants of S. aureus may represent a valuable alternative to active immunization in the future, but it requires more research.Example:Monoclonal alpha -toxin.1