Microbiological Characteristics and Behavior of Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and Staphylococcal Toxin during Making and Maturing Cotija Cheese

Cotija cheese is an artisanal matured Mexican cheese from unpasteurized milk. This work determined the microbiological characteristics and behavior of Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and staphylococcal toxin during cheese elaboration and ripening. Sixteen 20-kg cheeses were used, eight inoculated with 6 log CFU/mL of each pathogen, and eight uninoculated, and samples were taken at each stage of the process. In the uninoculated samples, the survival of S. aureus and L. monocytogenes decreased after 30 days of ripening. The average counts of S. aureus in milk, curd, and serum were 7 log MPN /mL, and 8.7 log MPN /g in cheese, decreasing from day 15. Salmonella spp. counts (initial inoculum: 7.2 log MPN /mL) decreased after 24 h, and L. monocytogenes counts (8.7 log MPN/g at 24 h) decreased from day 15 in the cheese. Salmonella spp. and L. monocytogenes were not detected in any sample after 60 days of ripening, unlike S. aureus, which was detected at the end of the study. Lactic acid bacteria counts were 9 log CFU/mL in milk and whey and 7.2 log CFU/g in cheese. Pathogens behavior during the ripening process reduces the health risks by consuming products made with unpasteurized milk when subjected to ripening.

Prevalence, antimicrobial resistance and staphylococcal toxin gene of blaTEM-1a-producing Staphylococcus aureus isolated from animals in Chongqing, China

Background Livestock-associated Staphylococcus aureus is one of the most important etiological agents in both human and animals. It has been reported with high antimicrobial resistance and multiple staphylococcal superantigen genes in many countries and several provinces of China. However, large-scale investigation of this organism has not been documented in Chongqing, China. The aim of this study is to demonstrate the prevalence, antimicrobial susceptibility and some molecular characteristics of S. aureus acquired from animals in Chongqing. Results A total of 89 S. aureus isolates were cultured from 1371 samples picked up from March 2014 to December 2017. The isolates were originated from pigs (25), cattle (6), goats (10), rabbits (16) and chicken (32). Four MRSA strains were identified from 3 pig samples and 1 chicken sample. The isolates showed high resistance to penicillin (93.3%) and ampicillin (92.1%), but were more susceptible to amikacin and ofloxacin, since the resistance rates of these two drugs were less than 10%. Meanwhile, 74.2% isolates exhibited varying degree of MDR. Almost all strains, except for 3 chicken-originated isolates, were positive for blaTEM-1a, but did not harbor other ESBL genes. Nineteen staphylococcal SE/SEl/TSST-1 genes, except seq, were detected in isolates. The predominant genes were sei (58.4%), tst-1 (56.2%) and seg (51.7%). Conclusions The high antimicrobial resistance and prevalence of blaTEM-1a seriously reminded that it was urgent to standardize and cut down the usage of antimicrobials. The universal existence of staphylococcal toxin genes in isolated strains implied a potential threat of public health from animals to human through the food chain.

Staphylococcal superantigen-specific IgE antibodies: degree of sensitization and association with severity of asthma

ABSTRACT Objective: To determine the presence of staphylococcal superantigen-specific IgE antibodies and degree of IgE-mediated sensitization, as well as whether or not those are associated with the severity of asthma in adult patients. Methods: This was a cross-sectional study involving outpatients with asthma under treatment at a tertiary care university hospital in the city of Rio de Janeiro, Brazil. Consecutive patients were divided into two groups according to the severity of asthma based on the Global Initiative for Asthma criteria: mild asthma (MA), comprising patients with mild intermittent or persistent asthma; and moderate or severe asthma (MSA). We determined the serum levels of staphylococcal toxin-specific IgE antibodies, comparing the results and performing a statistical analysis. Results: The study included 142 patients: 72 in the MA group (median age = 46 years; 59 females) and 70 in the MSA group (median age = 56 years; 60 females). In the sample as a whole, 62 patients (43.7%) presented positive results for staphylococcal toxin-specific IgE antibodies: staphylococcal enterotoxin A (SEA), in 29 (20.4%); SEB, in 35 (24.6%); SEC, in 33 (23.2%); and toxic shock syndrome toxin (TSST), in 45 (31.7%). The mean serum levels of IgE antibodies to SEA, SEB, SEC, and TSST were 0.96 U/L, 1.09 U/L, 1.21 U/L, and 1.18 U/L, respectively. There were no statistically significant differences between the two groups in terms of the qualitative or quantitative results. Conclusions: Serum IgE antibodies to SEA, SEB, SEC, and TSST were detected in 43.7% of the patients in our sample. However, neither the qualitative nor quantitative results showed a statistically significant association with the clinical severity of asthma.