Methicillin Resistance of Food-Borne Biofilm-Forming Staphylococci

Abstract

The aim of this study was to evaluate the biofilm-forming ability and the resistance of planktonic cells and biofilm to methicillin (MIC and MBC, and log CFU/cm2 reduction, respectively). Thirty-four isolates were used, including coagulase-positive Staphylococcus (CPS) and coagulase-negative Staphylococcus (CNS), recovered from ready-to-eat (RTE) foods. Biofilm-forming ability was based on enumeration of viable cells from biofilms formed on three types of surfaces, namely stainless steel, polystyrene, and glass. Thirteen of the thirty-four isolates (38.2%) were methicillin-resistant (MIC higher than 4 µg/mL). Staphylococcus aureus (CPS) and Staphylococcus saprophyticus (CNS) were the species that showed the highest percentage of resistance (50% and 71.4%, respectively). Staphylococcus warneri was the only species susceptible to methicillin. In 20 of the 34 isolates, the MBC value was twice the MIC value. The CPS (S. aureus) and the CNS (the other species) were not significantly different (p > 0.05) on biofilm-forming ability on the three surfaces used. However, when comparing the averages obtained for the biofilm-forming ability of the isolates, the values obtained (log CFU/cm2) in polystyrene were significantly higher (p < 0.05) than those obtained with the isolates on stainless steel. On the other hand, data from biofilm-forming ability of the isolates on glass and stainless steel are positively and significantly correlated with each other (r = 0.54; p = 0.02). It was not possible to determine the concentration of methicillin that promotes biofilm removal since log reductions were less than 3 log CFU/cm2. The results of this study indicate that foodborne CPS and CNS can form biofilms on different types of material. As these biofilms are resistant to high concentrations of methicillin, their occurrence in food environments and their spread to medical settings can result in staphylococcal food poisoning or, in the worst-case scenario, septicemia, respectively. Good hygiene and good manufacturing practices (GHP and GMP) are therefore mandatory to prevent contamination with Staphylococcus spp.

Multidrug Resistance in Enterococci Isolated from Cheese and Capable of Producing Benzalkonium Chloride-Resistant Biofilms

“…The MBC of BAC was determined after the MIC determination, namely, from all the wells that did not show visible bacterial growth after 24 h incubation at 37 • C, 100 µL was removed, inoculated onto TSA-YE, Trypto-Casein-Soy agar plates (Biokar Diagnostics, Beauvais, France), and incubated at 37 • C for 24 h. MBC was defined as the lowest concentration of BAC capable of killing 99.9% of the bacterial population (3 Log reduction) [40,41].…”

“…The evaluation of the biofilm-forming ability of the isolates was performed based on the removal of cells from the biofilms formed on the surface of stainless-steel coupons (SSCs), 1 cm × 1 cm and 1 mm thick, type 304, 2B finish (Metalurgica Quinacorte, Lda, Lousa, Portugal), as previously described [40,41]. Briefly, each coupon was immersed in a well of a 24-well polystyrene microplate containing 1.5 mL of inoculum in TSB (about 10 8 cfu/mL).…”

The Socioeconomic Factors of Street Food Vending in Developing Countries and Its Implications for Public Health: A Systematic Review

“…Infections with methicillin-resistant strains of S. aureus (MRSA) have been linked to hospital-acquired infections (HA-MRSA) [78,104]. However, in recent decades, there has been an increase in the number of community-acquired (CA-MRSA) and livestockassociated (LA-MRSA) MRSA infections [105,106]. Some authors associate this increase in CA-MRSA and LA-MRSA infections with RTE food contamination, either through contaminated raw materials or through contamination by food handlers [78,98].…”