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Brazilian Journal of Infectious Diseases

versão impressa ISSN 1413-8670

Braz J Infect Dis vol.15 no.5 Salvador set./out. 2011 



Molecular identification and typing of Mycobacterium massiliense isolated from postsurgical infections in Brazil



Fernanda MonegoI; Rafael Silva DuarteII; Sueli Massumi NakataniIII; Wildo Navegantes AraújoIV; Irina Nastassja RiedigerV; Sonia BrockeltVI; Verena SouzaIV; Jamyra Iglesias CataldoVII; Rubens Clayton da Silva DiasVIII; Alexander Welker BiondoIX

IMSc; PhD Student, Molecular and Cellular Biology, Universidade Federal do Paraná (UFPR), PR, Brazil
IIPhD; Associate Professor, Universidade Federal do Rio de Janeiro (UFRJ), RJ, Brazil
IIIPhD; Head of Molecular Biology, Laboratório Central do Estado do Paraná (LACEN-PR), PR, Brazil
IVMSc; Epidemiologists, Secretaria de Vigilância em Saúde (SVS), Departament of Serological Vigilance, Brazil
VMSc; Researcher, LACEN-PR, PR, Brazil
VIMSc; Head of the Mycobacteria Sector, LACEN-PR, PR, Brazil
VIIMSc; PhD Student, Universidade do Estado do Rio de Janeiro (UERJ), RJ, Brazil
VIIIPhD; Researcher, UERJ, RJ, Brazil
IXPhD; Full Professor of Zoonoses, UFPR, PR, Brazil

Correspondence to




OBJECTIVE: One hundred thirty-one cases of postsurgical infections were reported in Southern Region of Brazil between August 2007 and January 2008. Thirty-nine (29.8%) cases were studied; this report describes epidemiological findings, species identification, antimicrobial susceptibility and clonal diversity of rapidly growing mycobacteria isolated in this outbreak.
METHODS: All 39 isolates were analyzed by Ziehl-Nielsen stained smear, bacterial culture and submitted to rpoB partial gene sequencing for identification. The isolates were also evaluated for their susceptibility to amikacin, cefoxitin, clarithromycin, ciprofloxacin, doxycycline, tobramycin and sulfamethoxazole.
RESULTS: Thirty-six isolates out of the confirmed cases were identified as Mycobacterium massilienseand the remaining three were identified as Mycobacterium abscessus, Mycobacterium chelonae and Mycobacterium fortuitum. All M. massiliense isolates were susceptible to amikacin (MIC90 = 8 µg/mL) and clarithromycin (MIC90 = 0.25 µg/mL) but resistant to cefoxitin, ciprofloxacin, doxycycline, tobramycin and sulfamethoxazole. Molecular analysis by pulsed-field gel electrophoresis clustered all 36 M. massiliense isolates and showed the same pattern (BRA 100) observed in three other outbreaks previously reported in Brazil.
CONCLUSIONS: These findings suggest a common source of infection for all patients and reinforce the hypotheses of spread of M. massiliense BRA100 in Brazilian hospital surgical environment in recent years.

Keywords: mycobacteria, atypical; mycobacterium infections; microbiological analysis.




Human infections after cosmetic procedures, surgery, postinjection and nipple piercing1,2 by rapidly growing mycobacteria (RGM) have been described worldwide as mainly associated with Mycobacterium chelonae, Mycobacterium abscessus, Mycobacterium fortuitum and Mycobacterium smegmatis groups.3 These microorganisms have already been isolated from soil, water treatment plants, hospital tap water and distilled water, and considered environmentally adapted species.4 Some RGM strains have been described as being able to develop biofilm and infections related to biofilm represent more than two-thirds of all infections caused by these organisms.5

Hospital outbreaks as well as isolated cases of RGM infections have been reported in different scenarios involving chronic lung disease, disseminated cutaneous infections and postsurgical wound infections.6,7 Outbreaks and pseudo-outbreaks associated with these bacteria have been generally related to contaminated medical equipments, solutions and laboratory reagents.8,9 Strains resistant to disinfectants have also been isolated from endoscope washer disinfector after decontamination with 2% glutaraldehyde solution.10 Since 2% glutaraldehyde is one of the basic compounds most widely used as a chemical disinfectant for surgical equipment in several countries, particularly for non-autoclavable devices, resistance to biocides have become a great concern in hospital practice.

In Brazil, the first reported outbreaks caused by M. chelonae-abscessus group species were related to laser in situ keratomileusis, mesotherapy sessions and breast implant surgeries.11,12 Mycobacterium massiliense has been described as the main agent isolated during these recent RGM outbreaks in several Brazilian states, mainly those that occurred after 2004. Furthermore, in all described postsurgical outbreaks, a specific M. massiliense clone, named BRA100, has emerged as an opportunistic pathogen, usually causing postsurgical wound infections, including superficial abscesses and granulomas.13 The Brazilian Public Health Surveillance System has registered an overall of 1,937 confirmed cases of RGM postsurgical infections since 2001. Up to now, only three M. massiliense outbreaks have been reported in Brazil, all related to surgical site infections following video-assisted surgeries. Even though each of the three Brazilian M. massiliense outbreaks occurred in distant geographical regions (Northern, Central and Southeastern regions of Brazil), strains isolated from each outbreak were identified as clonal by molecular techniques.2,13,14 We report a new postsurgical infection outbreak of M. massiliense in Curitiba, Brazil, which includes clinical findings, microbiological investigation, and molecular typing by pulsed-field gel electrophoresis (PFGE) and rpoB partial gene sequencing.



General aspects and microbiological procedures

From August 2007 to January 2008, 131 patients were submitted to surgical procedures at one of the seven major private hospitals located in the city of Curitiba, in the South region of Brazil. All patients showed signs of postsurgical infections clinically suggestive of RGM, such as wound with local inflammation, presence of abscess, delayed wound healing and no response to the treatment commonly used in cutaneous infections. Out of the 131 patients, a sample of 39 patients were collected by either biopsy or aspiration of abscesses fluids and were cultivated on Lowenstein-Jensen solid medium for up to four weeks at 37ºC.15 A detailed history of patients was obtained by the Public Health Surveillance System. We were not able to inspect environmental conditions such as sterilization measures or antiseptic method applied. This study was approved by the Internal Review Board, Hospital do Trabalhador Ethics Committee.

Species identification

Observation of the growth rate was taken as an evidence of RGM. Definitive confirmation and species identification was based on partial sequencing of the rpoB gene. Extraction of DNA from clinical isolates was carried out using the Kit Nuclisens Basic Nasba Diagnostics (bioMérieux) based on methods previously published.16 DNA amplification and sequencing of the PCR products was performed with primers MycoF (5'-GCA AGG TCA CCC CGA AGG G-3') and MycoR (5'-AGC GGC TGC TGG GTG ATC ATC-3'), that amplify a 764 bp within the rpoB gene.17 PCR mixtures (50 µL) contained 5 µL of 10 X Taq buffer (included with Taqpolymerase), 200 µM each deoxynucleoside triphosphate, 2 mM MgCl2, 1 U of Taq DNA polymerase (Invitrogen), 10 mmol of each primer (Invitrogen), 2 µL of the extracted DNA and ultrapure water. PCR mixtures were subjected to 35 cycles of denaturation at 94ºC for 30s, primer annealing at 64ºC for 30s, and DNA elongation at 72ºC for 90s. Every amplification program began with a denaturation step of 95ºC for 1 min and ended with a final elongation step of 72ºC for 5 min. Amplicons were purified with PureLinkTM PCR purification kit (Invitrogen) and cycle-sequenced using the Big dye terminator kit v.3.1 according to the manufacturer's instructions (Applied Biosystems) with the following program: 30 cycles of denaturation at 94ºC for 10s, primer annealing at 50ºC for 15s, and extension at 60ºC for 4 min. The cycling-sequenced products were purified by Big Dye XTerminatorTM Purification kit (Applied Biosystems) and detected on an ABI Prism 3110 DNA Sequence Analyzer (Applied Biosystems). The resulting sequences were aligned with BioEdit software (version using M. tuberculosis H37Rv (GenBank accession BX842574.1) as the reference sequence. The homology analysis was performed by comparison of the consensus sequence obtained from each isolate with those deposited in the GenBank using the BLAST algorithm (Basic Local Alignment Search Tool,

Antimicrobial susceptibility test

All 39 isolates were evaluated for their susceptibility to amikacin, cefoxitin, clarithromycin, ciprofloxacin, doxycycline, sulfamethoxazole and tobramycin as recommended by the Clinical and Laboratory Standards Institute.19 Staphylococcus aureus ATCC 29213 was used as a control strain.

Pulsed-field gel electrophoresis analysis

All M. massiliense isolates were submitted to genotypic analysis by PFGE. One isolate of M. massiliense BRA 100 clone from a previous outbreak occurred in Rio de Janeiro state (CRM 0020) and two epidemiologically unrelated strains recovered from sputum samples in 2007 in Rio de Janeiro city (CRM 0270 and CRM 0273) were also included for comparison. The agarose plugs were first treated as previously described, and then digested with DraI (Promega).20,21 Agarose gel (1%) was used to separate the restriction fragments in a CHEF-DRIII system (Bio-Rad Laboratories) with pulse times increasing from 1.6 to 21.3s over 22 hr at 14ºC, at a voltage gradient of 6 V/cm and with included angle of 120º. The PFGE profiles generated were analyzed by a commercial molecular analysis fingerprinting GelCompar software (Applied Maths). Fragments patterns were interpreted as previously described.22



Clinical findings and outbreak description

We studied 39 cases of post-surgical infection, which were confirmed by microbiological culture while 92 remained as suspected cases. The median age was 50 years old (range 24-87) and most patients (73.0%) were female. All patients showed abscesses only on the surgical site. One hospital concentrated 77% of the cases. The time from surgery to the manifestation of clinical signs ranged from 5 to 60 days. Most patients (n = 33; 84.6%) were treated with a combined antimicrobial therapy consisting of clarithromycin, amikacin and terizidone. The remaining patients received an initial treatment with clarithromycin, amikacin and minocycline. The majority of cases (n = 37; 94.9%) progressed to cure and two reported deaths were associated with RGM infection.

Species identification

Growth of the isolates was observed in less than seven days and Ziehl-Nielsen stained smears showed acid-fast bacilli. The organisms were identified as rapidly growing non-pigmented mycobacteria and pure culture isolates were used for molecular species identification. Analysis of the rpoB gene sequences of all isolates were identical and presented 100% similarity (695/695) to the sequence from M. massiliense strain INCQS 594 (GenBank accession number EU117207). One sequence was identical (695/695) to M. abscessustype strain P02 (GenBank accession number FJ590436.1). One isolate was similar (695/695) to the M. chelonae ATCC 19237 type strain, retrieved from GenBank under the accession number AY262740.1. The other isolate had the similar sequence (695/695) to M. fortuitum type strain CIP 104534T (GenBank accession number AY147165.1).

Antimicrobial susceptibility test

All M. massiliense isolates were susceptible to amikacin (MIC90 = 8 µg/mL) and clarithromycin (MIC90 = 0.25 µg/mL) but resistant to cefoxitin, doxycycline, sulfamethoxazole and tobramycin. Thirty-five M. massiliense isolates were ciprofloxacin-resistant and a single isolate was characterized as susceptible. M. abscessus isolate was susceptible to amikacin (MIC = 8 µg/mL) and clarithromycin (MIC = 0.25 µg/mL) and intermediate to cefoxitin (MIC90 = 128 µg/mL). However, this isolate was resistant to ciprofloxacin, doxycycline, tobramycin and sulfamethoxazole. M. chelonae isolate was susceptible to clarithromycin (MIC = 0.25 µg/mL) and intermediate to amikacin (MIC = 32 µg/mL) and tobramycin (MIC = 16 µg/mL), but resistant to cefoxitin, ciprofloxacin, doxycycline and sulfamethoxazole. M. fortuitum isolate was susceptible to amikacin (MIC = 8 µg/mL), clarithromycin (MIC = 0.25 µg/mL) and ciprofloxacin (MIC = 16 µg/mL) but resistant to doxycycline, sulfamethoxazole and tobramycin. This isolate presented intermediate resistance to cefoxitin (MIC = 128 µg/mL).

Molecular pattern

PFGE analysis revealed that M. massiliense isolates presented indistinguishable patterns and according to the criteria proposed by Tenover et al.22 these isolates were considered highly related and to belong to the same strain. The PFGE patterns were similar to those of the isolates recovered from a recent epidemic in Rio de Janeiro, Southeastern Brazil (strain CRM 0020, Figure 1).13 M. massilienseisolates obtained from sputum samples (CRM 0270 and CRM 0273) showed no identical eletrophoretic patterns when compared to those isolates from Curitiba and Rio de Janeiro (Figure 2).






The Brazilian Public Health Surveillance System has presented cases of RGM infections from 2001 to date. Since 2001, a total of 1,937 confirmed cases were registered, with an evident increase of outbreaks in the period (Figure 3). However, there are only three reports of M. massiliense outbreaks in Brazil, all related to surgical infection following video-assisted surgeries.

This study reports the identification and molecular epidemiological features of a single clone of M. massiliense isolated from a new outbreak of surgical site infections caused by RGM in Curitiba, Southern region of Brazil. Partial rpoB sequence analysis was considered discriminatory for identification of M. massiliense clinical isolates described here, since we obtained the highest similarity index (100%) when comparing our sequences to that of the M. massiliense type strain. The rpoB partial sequencing and PFGE analysis confirmed the similarity of our isolates with those of previously reported outbreaks in Brazil.2,13,14 The molecular patterns obtained suggest a common source of infection and spread of a single clone of M. massiliense in different regions of the country.

There were some limitations in this study. First a recall bias might have occurred since only 39 cases were included causing the reduced availability of other strains for analysis. Additionally, the lack of standardized procedures or protocols for isolation of RGM from surgical supplies made it difficult to determine the infection sources and its relation with surgical devices and equipments. Since no environmental isolates were obtained, we were not able to definitely identify the source of the infection. In this outbreak surgical equipments were disinfected by immersion in 2% glutaraldehyde and were used in different hospitals by different surgical teams that brought along their own instruments and performed surgeries in other cities and states. Inspections made by public health authorities evidenced that the disinfection protocol was unsettled by some of the hospitals in different ways. Thus, strictly monitoring concerning disinfection in 2% glutaraldehyde solution may explain why some hospitals in Curitiba have not had cases of surgical infections caused by RGM.

The sources of the infections for the surgical cases have not been identified in the first outbreak, in Northern Brazil. Patient procedures were performed by different surgeons, who used their own laparoscopic equipment, referred to be disinfected by immersion in 2% glutaraldehyde between surgeries and which were used in different hospitals.2 Inconsistencies in equipment cleaning, glutaraldehyde concentrations, or contact times were suggested as the cause of the M.massiliense strain selection. The disinfection procedure used in arthroscopic and laparoscopic surgeries in Central Brazil outbreak was also performed by immersion in 2% glutaraldehyde. According to inspections made by public health authorities, the disinfection protocol was incorrectlyimplemented in some hospitals. So, inadequate aseptic techniques during surgeries could have been the possible cause.13 In the Southeastern outbreak, all hospitals that presented cases of M. massiliense infection used 2% alkaline glutaraldehyde solution to sterilize surgical instruments. Interestingly, all M. massiliense isolates consistently presented tolerance to 2% glutaraldehyde.14 The authors suggested that 2% glutaraldehyde tolerance may partially explain the occurrence of outbreaks in three different regions in Brazil.

Based on reported RGM outbreaks, potential source of infection was either the lack of adequate disinfection procedures (that could result in biofilm formation) or resistance to common disinfectants, or even both. Biofilms have been described in a high number of human infections, especially those related to biomaterials.23 Although biofilm formation may contribute to tolerance to biocide solutions,24 biofilm itself could not explain the single clone found on different time periods in distinct Brazilian regions.13 However, since a significant relationship between biofilm development ability and clinical infection has been experimentally demonstrated, biofilm development may be an important pathogenic risk factor for RGM, contributing to development of human infections.25 Moreover, biofilms are a wellknown form of bacterial resistance against antibiotics,26 and therefore the facility to develop these structures can explain treatment failures.27

Non-tuberculosis mycobacteria are often resistant to standard antituberculosis drugs and can be very difficult to treat. If RGM infection is identified and treated early, adequate recovery is possible, otherwise death can ensue. In this report, 33 patients (n = 39, 84.6%) were treated with a combination of amikacin, clarithromycin and terizidone. Treatment with multiple agents is preferable because of a high rate of relapse and emergence of drug resistance.28 Amikacin and clarithromycin exhibited the greatest activity against all RGM isolates in this study and demonstrated to be effective when used in a multidrug regimen. All M. massilienseisolates from Rio de Janeiro outbreak tested in vitro were susceptible to amikacin and clarithromycin and resistant to cefoxitin, ciprofloxacin and doxycycline;13 the same susceptibility pattern observed in our isolates. Although no treatment data was presented in the Rio de Janeiro outbreak, patients from the Central Brazil outbreak were successfully treated with a combination of clarithromycin and amikacin.

After the occurrence of RGM outbreaks, the Brazilian Public Health Surveillance System recommended preventive measures to reduce the infections in Brazilian hospitals. These measures include the discontinuation of chemical sterilization by immersion for invasive items used in abdominal surgeries, conventional laparoscopic and plastic surgery. For disinfection of non-autoclavable equipments used in surgical procedures such as endoscopes, sterilization should be performed by ethylene oxide gas, hydrogen peroxide plasma or low-temperature steam with formaldehyde gas. Since these measures have been adopted by the hospitals no additional case of RGM infection was registered by the Brazilian Public Health Surveillance System.

The obtained results suggest that a single M. massilienseclone might be responsible for the infections that have occurred in Northern, Central and Southeastern regions of Brazil and reinforce the concept of M. massiliense BRA100 as an emergent pathogen in Brazilian hospital surgical environment.



1. Trupiano JK, Sebek BA, Goldfarb J et al. Mastitis due to Mycobacterium abscessus after body piercing. Clin Infect Dis 2001;33:131-4.         [ Links ]

2. Viana-Niero C, Lima KV, Lopes ML et al. Molecular characterization of Mycobacterium massilienseand Mycobacterium bolletii in isolates collected from outbreaks of infections after laparoscopic surgeries and cosmetic procedures. J Clin Microbiol 2008;46:850-55.         [ Links ]

3. Brown-Elliott BA, Wallace RJ. Clinical and taxonomic status of pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria. Clin Microbiol Rev 2002;15:716-46.         [ Links ]

4. Zhibang Y, BiXia Z, Qishan L et al. Large-scale outbreak of infection with Mycobacterium chelonaesubsp. abscessus after penicillin injection. J Clin Microbiol 2002;40:2626-28.         [ Links ]

5. Esteban J, Martın-de-Hijas NZ, Fernandez AI et al. Epidemiology of infections due to Non-pigmented Rapidly Growing Mycobacteria diagnosed in an urban area. Eur J Clin Microbiol Infect Dis 2008;27:951-57.         [ Links ]

6. Kim HY, Kook Y, Yun YJ et al. Proportions of Mycobacterium massilienseand Mycobacterium bolletii strains among Korean Mycobacterium chelonae-Mycobacterium abscessus group isolates. J Clinl Microbiol 2008;46:3384-90.         [ Links ]

7. Falkinham JO. Epidemiology of infection by nontuberculous mycobacteria. Clin Microbiol Rev 1996;9:177-215.         [ Links ]

8. Tiwari TS, Ray B, Jost Jr KC et al. Forty years of disinfectant failure: outbreak of postinjection Mycobacterium abscessus infection caused by contamination of benzalkonium chloride. Clin Infect Dis 2003;36:954-62.         [ Links ]

9. Wilson RW, Steingrube VA, Bottger EC et al. Mycobacterium immunogenum sp. nov., a novel species related to Mycobacterium abscessus and associated with clinical disease, pseudooutbreaks and contaminated metalworking fluids: an international cooperative study on Mycobacterial taxonomy. Int J Syst Evol Microbiol 2001;51:1751-64.         [ Links ]

10. Fraser VJ, Jones M, Murray PR et al. Contamination of flexible fibreoptic bronchoscopes with Mycobacterium chelonae linked to an automated bronchoscope disinfection machine. Am Rev Resp Dis 1992;145:853-55.         [ Links ]

11. Freitas D, Alvarenga L, Sampaio J et al. An outbreak of Mycobacterium chelonae infection after LASIK. Ophthalmol 2003;110:276-85.         [ Links ]

12. Sampaio JL, Chimara E, Ferrazoli L et al. Application of four molecular typing methods for analysis of Mycobacterium fortuitum group strains causing post-mammaplasty infections. Clin Microbiol Infect 2006;12:142-49.         [ Links ]

13. Duarte RS, Lourenço MC, Fonseca L et al. An Epidemic of Postsurgical Infections Caused by Mycobacterium massiliense. J Clin Microbiol 2009;47:2149-55.         [ Links ]

14. Cardoso AM, Martins de Sousa E,Viana-Niero C et al. Emergence of nosocomial Mycobacterium massilienseinfection in Goias, Brazil. Microb Infect 2008;10:1552-57.         [ Links ]

15. McMurray DN. Mycobacteria and nocardia. In: Roberts GD. Laboratory Procedures in Clinical Microbiology. Springer-Verlag, Mayo Foundation, 1985.         [ Links ]

16. Boom R, Sol CJ, Salimans MM et al. Rapid and simple method for purification of nucleic acids. J Clin Microbiol 1990;28:495         [ Links ]

17. Adekambi T, Colson P, Drancourt M. rpoB-based identification of nonpigmented and late-pigmenting rapidly growing mycobacteria. J Clin Microbiol 2003;41:5699-708.         [ Links ]

18. Hall TA. BioEdit: a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. Nucleic Acids Symp 1999;41:95-8.         [ Links ]

19. CLSI. Clinical and Laboratory Standards Institute Quality Manual, 3rd edn. CLSI, 940 West Valley Road, Suite 1400, Wayne, Pennsylvania 19087-1898 USA, 2003.         [ Links ]

20. Coleman NV, Spain JC. Distribution of the coenzyme M pathway of epoxide metabolism among ethene- and vinyl chloridedegrading Mycobacterium strains. Appl Environ Microbiol 2003;69:6041-46.         [ Links ]

21. Sampaio JL, Viana-Niero C, de Freitas D et al. Enterobacterial repetitive intergenic consensus PCR is a useful tool for typing Mycobacterium chelonae and Mycobacterium abscessus isolates. Diagn Microbio Infect Dis 2006;55:107-18.         [ Links ]

22. Tenover FC, Arbeit RD, Goering RV et al. Interpreting chromosomal DNArestriction patterns produced by pulsed-field gel electrophoresis: criteria for bacterial strain typing. J Clin Microbiol 1995;33:2233-39.         [ Links ]

23. Donlan RM. Biofilm formation: a clinically relevant microbiological process. Clin Infect Dis 2001;33;1387-92.         [ Links ]

24. Simoes M, Pereira MO, Vieira MJ. Effect of mechanical stress on biofilms challenged by different chemicals. Water Res 2005;39:5142-52.         [ Links ]

25. Martín-de-Hijas NZ, García-Almeida D, Ayala G et al. Biofilm development by clinical strains of non-pigmented rapidly growing mycobacteria. Clin Microbiol Infect 2009;15:931-36.         [ Links ]

26. Mah TC, O'Toole GA. Mechanisms of biofilm resistance to antimicrobial agents. Trends Microbiol 2001;9:34-9.         [ Links ]

27. De Groote MA, Huitt G. Infections due to rapidly growing mycobacteria. Clin Infect Dis 2006;42:1756-63.         [ Links ]

28. Dalovisio JR, Pankey GA, Wallace RJ. Clinical usefulness of amikacin and doxycycline in the treatment of infection due to Mycobacterium fortuitum and Mycobacterium chelonae. Rev Infect Dis 1981;3:1068-74.         [ Links ]



Correspondence to:
Fernanda Monego
Universidade Federal do Paraná (UFPR), Depart. de Medicina Veterinária
Rua dos Funcionários, 1540
Juveve 80035-050,
Curitiba, Paraná, Brazil
Phone.: +55 41 3350-5723 Fax: +55 41 3350-5623

Submitted on: 01/18/2011
Approved on: 06/29/2011
We declare no conflict of interest.

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