A influência da microbiota de doadores e do armazenamento do enxerto no transplante de córnea / Influence of donor microbiota and of graft storage on corneal transplantation

Introdução: O transplante de córneas é o principal tratamento para pessoas que apresentam distúrbios de curvatura ou transparência da córnea. No Brasil, não há protocolo unificado para meios de preservação, tempo de armazenamento e antibióticos utilizados. A preocupação é a de que patógenos possam ser transferidos aos receptores de transplantes. Objetivo: Realizar o levantamento da microbiota ocular de doadores de córneas a fim de verificar uma possível correlação com infecções em receptores e, dessa forma, auxiliar na melhoria de metodologias e protocolos de armazenamento de córneas. Método: Foi conduzido a partir de revisão da literatura, nas bases de dados PubMed, SciELO e nos portais: periódicos da CAPES, Anvisa, Ministério da Saúde e ABTO, entre 2018 e 2020. Resultados: Estudos baseados em cultivo de microrganismos trazem Staphylococcus coagulase negativa (SCN) de 30% a 100% das amostras isoladas de conjuntivas. Em menor quantidade estão Streptococcus, Corynebacterium e Propionibacterium. Bactérias Gramnegativas aparecem em número inferior, representadas pelos gêneros Haemophilus, Neisseria, Pseudomonas, Enterobacter, Escherichia, Proteus e Acinetobacter. Já as técnicas independentes de cultivo trazem Pseudomonas como a principal colonizadora da conjuntiva. Também apresentam uma diversidade maior de colonizadores, mostrando um potencial campo de estudos, no qual a superfície ocular pode ter uma diversidade muito maior de espécies e potenciais agentes patogênicos. Os principais meios de preservação utilizados no Brasil levam os antimicrobianos gentamicina e estreptomicina em sua composição, porém estudos têm mostrado que as bactérias presentes nos meios de preservação são resistentes a esses antibióticos. Conclusões: Os dados apontam para a necessidade de reavaliação da eficiência desses meios de preservação na descontaminação das córneas para transplante.

Introduction: Corneal transplantation it is the main treatment for people who have corneal curvature or transparency disorders. In Brazil, there is no unifed protocol on the means of preservation, storage time and antibiotics used. The concern is that pathogens are transferred to transplant recipients, causing eye infections after transplantation. Objective: Examine ocular microbiota of corneal donors, to verify a possible correlation with infections in recipients and thus assist in improving corneal storage methodologies and protocols. Method: Literature review conducted in PubMed, SciELO and the following websites: CAPES Journals, Anvisa, Brazilian Ministry of Health and ABTO, between 2018 and 2020. Results: Studies based on microorganism's cultivation show coagulase negative Staphylococcus in 30% to 100% of samples isolated from conjunctiva. In lesser quantities are Streptococcus, Corynebacterium and Propionibacterium. Gram-negative bacteria appear in much lower numbers, represented by the genera Haemophilus, Neisseria, Pseudomonas, Enterobacter, Escherichia, Proteus and Acinetobacter. On the other hand, results based on independent cultivation techniques bring Pseudomonas as the main colonizer of the conjunctiva. Also, they have a much greater diversity of colonizers, showing a potential feld of study. The ocular surface may have a much greater diversity of species and potential pathogens than was expected. The main means of preservation used in Brazil contain the antimicrobials gentamicin and streptomycin in their composition; however, several studies have shown that bacteria present in the means of preservation are resistant to these antibiotics. Conclusions: These data point to the need for a reassessment of the efciency of these means of preservation in decontaminating corneas for transplantation.

Biofilm formation and antibiotic susceptibility of Staphylococcus and Bacillus species isolated from human allogeneic skin.

Human skin banks around the world face a serious problem with the high number of allogeneic skins that are discarded and cannot be used for grafting due to persistent bacterial contamination even after antibiotic treatment. The biofilm formation capacity of these microorganisms may contribute to the antibiotic tolerance; however, this is not yet widely discussed in the literature. Thisstudy analyzed bacterial strains isolated from allogeneic human skin samples,which were obtained from a hospital skin bank that had already been discardeddue to microbial contamination. Biofilm formation and susceptibility topenicillin, tetracycline, and gentamicin were evaluated by crystal violetbiomass quantification and determination of the minimum inhibitoryconcentration (MIC), minimum biofilm inhibitory concentration (MBIC), andminimum biofilm eradication concentration (MBEC) by the broth microdilutionmethod with resazurin dye. A total of 216 bacterial strains were evaluated, and204 (94.45%) of them were classified as biofilm formers with varying degrees ofadhesion. MBICs were at least 512 times higher than MICs, and MBECs were atleast 512 times higher than MBICs. Thus, the presence of biofilm in allogeneicskin likely contributes to the inefficiency of the applied treatments as antibiotictolerance is known to be much higher when bacteria are in the biofilmconformation. Thus, antibiotic treatment protocols in skin banks shouldconsider biofilm formation and should include compounds with antibiofilmaction.

Bacterial contamination of human skin allografts and antimicrobial resistance: a skin bank problem.

BACKGROUND: Bacterial contamination remains the major problem in skin banks, even after antimicrobial treatment, and results in high rates of tissue discarding. This study aimed to analyze bacterial contamination in 32 human skin allografts from the skin bank of Dr. Roberto Corrêa Chem from the Hospital Complex Santa Casa de Misericórdia de Porto Alegre. These samples were already discarded due to microbial contamination. The identification of the bacteria isolated from skin allografts was performed by matrix assisted laser desorption ionization-time of flight. The antimicrobial susceptibility of the isolates to six different classes of antimicrobials was determined using the disk-diffusion agar method, and the evaluation of the inhibitory potential was determined by the minimal inhibitory concentration (50/90) of antimicrobials already used in the skin bank and those that most isolates were susceptible to. RESULTS: A total of 21 (65.6%) skin samples were contaminated with Gram-positive bacteria: 1 (4.7%) with Paenibacillus sp., 12 (61.9%) with Bacillus sp., 6 (28.5%) with Staphylococcus sp., and 2 (9.5%) with Bacillus sp. and Staphylococcus sp. Several resistance profiles, including multiresistance, were found among the isolates. Most of the isolates were susceptible to at least one of the antimicrobials used in the skin bank. All isolates were susceptible to amikacin, gentamicin, and tetracycline, which demonstrated the best inhibitory activities against the isolates and were considered as potential candidates for new antimicrobial treatments. CONCLUSIONS: Bacillus, Paenibacillus, and Staphylococcus were isolated from the skin allografts, thus demonstrating the predominance of Gram-positive bacteria contamination. Other factors not related to the resistance phenotype may also be involved in the persistence of bacterial isolates in the skin allografts after antibiotic treatment. Gentamicin, amikacin, and tetracycline can be considered as an option for a more effective treatment cocktail.

First Report of Human Gastroenteritis Caused by Escherichia coli O157:NM in Brazil.

In September 2005, the Sanitary Surveillance Service of Rio de Janeiro (SSS/RJ), Brazil, investigated a case of gastroenteritis involving a 13-year-old teenager hospitalized because of bloody diarrhea and severe abdominal pain. Owing to the severity of the symptoms, an epidemiological investigation was conducted in two states of Brazil. Escherichia coli O157:NM was isolated from stools and from a tomato and cheese salad prepared at the school canteen where the teenager attended. This is the first report of a human case of gastroenteritis related to E. coli O157:NM infection in Brazil.

Antimicrobial resistance and PCR-ribotyping of Shigella responsible for foodborne outbreaks occurred in southern Brazil

Little information about Shigella responsible for foodborne shigellosis is available in Brazil. The present study aimed to investigate the antimicrobial resistance and PCR-ribotyping patterns of Shigella isolates responsible for foodborne outbreaks occurred in Rio Grande do Sul State (RS), Southern Brazil in the period between 2003 and 2007. Shigella strains (n=152) were isolated from foods and fecal samples of victims of shigellosis outbreaks investigated by the Surveillance Service. Identification of the strains at specie level indicated that 71.1 percent of them were S. flexneri, 21.5 percent S. sonnei, and 0.7 percent S. dysenteriae. Ten strains (6.7 percent) were identified only as Shigella spp. An increasing occurrence of S. sonnei was observed after 2004. Most of the strains were resistant to streptomycin (88.6 percent), followed by ampicillin (84.6 percent), and sulfamethoxazole/trimethoprim (80.5 percent). Resistant strains belonged to 73 patterns, and pattern A (resistance to ampicillin, sulfamethoxazole/trimethoprim, tetracycline, streptomycin, chloramphenicol, and intermediate resistance to kanamycin) grouped the largest number of isolates (n=36). PCR-ribotyping identified three banding patterns (SH1, SH2, and SH3). SH1 grouped all S. flexneri and SH2 grouped all S. sonnei. The S. dysenteriae strain belonged to group SH3. According to the results, several Shigella isolates shared the same PCR-rybotyping banding pattern and the same resistance profile, suggesting that closely related strains were responsible for the outbreaks. However, other molecular typing methods need to be applied to confirm the clonal relationship of these isolates.