Similaridade genética pelo RAPD-PCR de cepas de Staphylococcus sp isolados de portadores humanos e de camas de uma unidade hospitalar

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Detecção dos genes integron, invA e spvC em Salmonella Enteritidis proveniente de material avícola e transferência horizontal do gene integron entre enterobactérias

Pós-graduação em Medicina Veterinária - FMVZ

Ocorrência de Escherichia coli O157:H7 e O26 sorbitol negativas em matadouro frigorífico de bovino e suscetibilidade a antimicrobianos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Resistência antimicrobiana em coliformes totais isolados de tanques de refrigeração de leite bovino

Milk that is adequate for consumption must be of hygienic quality, nutritional value, and should maintain its organoleptic properties. Isolation of fecal and/or total coliforms from bovine milk is considered an indicator of hygiene and good management practices, and can be used as a quality indicator. This study aimed to isolate, identify, and assess the resistance profile of coliforms isolated from collective bulk tanks and individual milk tanks. A total of 89 milk samples were collected from collective bulk tanks and, from these, 21 Klebsiella spp., one E. coli, and 29 Enterobacter spp. were isolated, whereas 102 milk samples from individual tanks showed isolation of one Klebsiella spp. and seven Enterobacter spp. In collective bulk tanks, at least 47% of Klebsiella spp. and Enterobacter spp. were resistant to cephalexin and 30% to ampicillin. From these, at least 24% showed multidrug resistance. Among the microorganisms isolated from the individual tanks, 85% or more were resistant to ampicillin. The ESBL phenotype and the blaTEM gene were detected in strains of Klebsiella spp. isolated from both tanks. It was concluded that contamination of milk with resistant total coliforms, and especially the storage of raw milk from several small producers in the collective bulk tank increase the risk of contamination.

Clonal strains of Pseudomonas aeruginosa in paediatric and adult cystic fibrosis units

Despite recent reports of clonal strains of Pseudomonas aeruginosa in cystic fibrosis (CF) units, the need for routine microbiological surveillance remains contentious. Sputum was collected prospectively from productive patients attending the regional paediatric and adult CF units in Brisbane, Australia. All P. aeruginosa isolates were typed using pulsed-field gel electrophoresis. Spirometry, anthropometrics, hospitalisations and antibiotic sensitivity data were recorded. The first 100 sputum samples (first 50 patients at each clinic) harboured 163 isolates of P. aeruginosa. A total of 39 patients shared a common strain (pulsotype 2), 20 patients shared a strain with at least one other patient and 41 patients harboured unique strains. Eight patients shared a strain identical to a previously reported Australian transmissible strain (pulsotype 1). Compared with the unique strain group, patients harbouring pulsotype 2 were younger and had poorer lung function. Treatment requirements were similar in these two groups, as were the rates of multiresistance. In conclusion, 59% of patients harboured a clonal strain, supporting the need for routine microbiological surveillance. In contrast to previously described clonal strains, the dominant pulsotype was indistinguishable from nonclonal strains with respect to both colonial morphology and multiresistance. The clinical significance of clonal strains remains uncertain and requires longitudinal study.

Prevalence of SOS-mediated control of integron integrase expression as an adaptive trait of chromosomal and mobile integrons

BACKGROUND Integrons are found in hundreds of environmental bacterial species, but are mainly known as the agents responsible for the capture and spread of antibiotic-resistance determinants between Gram-negative pathogens. The SOS response is a regulatory network under control of the repressor protein LexA targeted at addressing DNA damage, thus promoting genetic variation in times of stress. We recently reported a direct link between the SOS response and the expression of integron integrases in Vibrio cholerae and a plasmid-borne class 1 mobile integron. SOS regulation enhances cassette swapping and capture in stressful conditions, while freezing the integron in steady environments. We conducted a systematic study of available integron integrase promoter sequences to analyze the extent of this relationship across the Bacteria domain. RESULTS Our results showed that LexA controls the expression of a large fraction of integron integrases by binding to Escherichia coli-like LexA binding sites. In addition, the results provide experimental validation of LexA control of the integrase gene for another Vibrio chromosomal integron and for a multiresistance plasmid harboring two integrons. There was a significant correlation between lack of LexA control and predicted inactivation of integrase genes, even though experimental evidence also indicates that LexA regulation may be lost to enhance expression of integron cassettes. CONCLUSIONS Ancestral-state reconstruction on an integron integrase phylogeny led us to conclude that the ancestral integron was already regulated by LexA. The data also indicated that SOS regulation has been actively preserved in mobile integrons and large chromosomal integrons, suggesting that unregulated integrase activity is selected against. Nonetheless, additional adaptations have probably arisen to cope with unregulated integrase activity. Identifying them may be fundamental in deciphering the uneven distribution of integrons in the Bacteria domain.