Detection of enterotoxin genes of Staphylococcus sp isolated from nasal cavities and hands of food handlers

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

Surfactin reduces the adhesion of food-borne pathogenic bacteria to solid surfaces

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Prevalence and phenotypic characterization of Enterococcus spp. isolated from food in Brazil

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

Lactobacillus sakei 2a and its Concentrated Acid Extract on Inhibition of Food-Borne Salmonella strains

Lactic acid bacteria are used in food production to provide desirable organoleptic characteristics, and can also act as biopreservatives, controlling the growth of undesirable microorganisms. In this study, we examined the antimicrobial action of Lactobacillus sakei 2a and its concentrated acid extract against food-borne Salmonella spp. The extract was obtained by acid extraction from culture broth of L. sakei 2a and was designated extract 2a. We determined that extract 2a had significant activity (approximately 500 AU ml(-1)). We used different antimicrobial substances alone or in combination with extract 2a to evaluate the inhibitory activity of the various treatments on a pool of five Salmonella strains. The pathogen Listeria monocytogenes Scott A Cm-r Em(r) was used as an indicator strain of inhibitory activity. In summary, all antimicrobials substances that were tested showed an inhibitory effect against the growth of Salmonella, andthis action was enhanced in the presence of extract 2a. Moreover, among the treatments applied, the combination of extract 2a and 0.1% lactic acid exhibited the most potent inhibitory effect towards the pool of Salmonella strains. Our findings indicate that L. sakei 2a and extract 2a, especially in combination with other antimicrobials, present potential technological application in the control of salmonellae in foods.

Antibiotic susceptibility patterns and resistance genes of starter cultures and probiotic bacteria used in food

A survey of starter and probiotic cultures was carried out to determine the current antibiotic resistance situation in microbial food additives in Switzerland. Two hundred isolates from 90 different sources were typed by molecular and other methods to belong to the genera Lactobacillus (74 samples), Staphylococcus (33 samples), Bifidobacterium (6 samples), Pediococcus (5 samples), or were categorized as lactococci or streptococci (82 samples). They were screened for phenotypic resistances to 20 antibiotics by the disk diffusion method. Twenty-seven isolates exhibiting resistances that are not an intrinsic feature of the respective genera were further analyzed by microarray hybridization as a tool to trace back phenotypic resistances to specific genetic determinants. Their presence was finally verified by PCR amplification or Southern hybridization. These studies resulted in the detection of the tetracycline resistance gene tet(K) in 5 Staphylococcus isolates used as meat starter cultures, the tetracycline resistance gene tet(W) in the probiotic cultures Bifidobacterium lactis DSM 10140 and Lactobacillus reuteri SD 2112 (residing on a plasmid), and the lincosamide resistance gene lnu(A) (formerly linA) in L. reuteri SD 2112.

Target genes for virulence assessment of Escherichia coli isolates from water, food and the environment

The widespread species Escherichia coli includes a broad variety of different types, ranging from highly pathogenic strains causing worldwide outbreaks of severe disease to avirulent isolates which are part of the normal intestinal flora or which are well characterized and safe laboratory strains. The pathogenicity of a given E. coli strain is mainly determined by specific virulence factors which include adhesins, invasins, toxins and capsule. They are often organized in large genetic blocks either on the chromosome ('pathogenicity islands'), on large plasmids or on phages and can be transmitted horizontally between strains. In this review we summarize the current knowledge of the virulence attributes which determine the pathogenic potential of E. coli strains and the methodology available to assess the virulence of E. coli isolates. We also focus on a recently developed procedure based on a broad-range detection system for E. coli-specific virulence genes that makes it possible to determine the potential pathogenicity and its nature in E. coli strains from various sources. This makes it possible to determine the pathotype of E. coli strains in medical diagnostics, to assess the virulence and health risks of E. coli contaminating water, food and the environment and to study potential reservoirs of virulence genes which might contribute to the emergence of new forms of pathogenic E. coli.

Harmonised monitoring of antimicrobial resistance in Salmonella and Campylobacter isolates from food animals in the European Union

Many Member States of the European Union (EU) currently monitor antimicrobial resistance in zoonotic agents, including Salmonella and Campylobacter. According to Directive 2003/99/EC, Member States shall ensure that the monitoring provides comparable data on the occurrence of antimicrobial resistance. The European Commission asked the European Food Safety Authority to prepare detailed specifications for harmonised schemes for monitoring antimicrobial resistance. The objective of these specifications is to lay down provisions for a monitoring and reporting scheme for Salmonella in fowl (Gallus gallus), turkeys and pigs, and for Campylobacter jejuni and Campylobacter coli in broiler chickens. The current specifications are considered to be a first step towards a gradual implementation of comprehensive antimicrobial resistance monitoring at the EU level. These specifications propose to test a common set of antimicrobial agents against available cut-off values and a specified concentration range to determine the susceptibility of Salmonella and Campylobacter. Using isolates collected through programmes in which the sampling frame covers all epidemiological units of the national production, the target number of Salmonella isolates to be included in the antimicrobial resistance monitoring per Member State per year is 170 for each study population (i.e., laying hens, broilers, turkeys and slaughter pigs). The target number of Campylobacter isolates to be included in the antimicrobial resistance monitoring per Member State per year is 170 for each study population (i.e., broilers). The results of the antimicrobial resistance monitoring are assessed and reported in the yearly national report on trends and sources of zoonoses, zoonotic agents and antimicrobial resistance.

Antibiotic resistance genes in coagulase-negative staphylococci isolated from food

Coagulase-negative staphylococci were isolated from different raw milk cheeses and raw meat products and screened for their antibiotic resistances. They were identified as Staphylococcus xylosus, S. lentus, S. caprae, S. epidemidis and S. haemolyticus. The most frequent resistances found were those to chloramphenicol, tetracycline, erythromycin and lincomycin. They have been characterized on the molecular level. The chloramphenicol resistance genes were localized in several S. xylosus and S. caprae on plasmids with sizes ranging from 3.8-kb to 4.3-kb and were identified as chloramphenicol acetyltransferase (cat). All the tetracycline resistant strains were identified as S. xylosus and harboured a 4.4-kb plasmid carrying the tetracycline efflux resistance gene (tetK). The two erythromycin/lincomycin resistant S. caprae and S. epidermidis strains did not hybridize with the MLSB resistance genes ermAM, ermA, ermB and ermC. Three erythromycin resistant Staphylococcus sp. strains harboured an erythromycin efflux resistance gene (msr) localized twice on a 18-kb plasmid and once on the chromosome. A S. haemolyticus strain showing resistance to both lincomycin and clindamycin harboured a linA gene-carrying 2.2-kb plasmid. Further resistances to gentamicin, penicillin and kanamycin were less frequently observed and yet not characterized on a molecular level.

High Prevalence of Extended-Spectrum β-Lactamase, Plasmid-Mediated AmpC and Carbapenemase genes in Food for Pets

We evaluated the pet food contained in thirty packages as potential origin of extended-spectrum cephalosporin-resistant Gram-negative organisms and β-lactamase genes (bla). Alive bacteria were not detected by selective culture. However, PCR investigations on food DNA extracts indicated that samples harbored blaCTX-M-15 (53.3%), blaCMY-4 (20%), and blaVEB-4-like (6.7%). Particularly worrisome was the presence of blaOXA-48-like carbapenemases (13.3%). Original pet food ingredients and/or the production process were highly contaminated with bacteria carrying clinically relevant acquired bla genes.