Incidência e controlo de bactérias patogénicas em alimentos frescos e de rua em Moçambique

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Methicillin resistance of food-borne biofilm-forming staphylococci

Publication . Salamandane, Acácio; Correia, Jussara; Muetanene, Belo Afonso; Santos, Madalena dos; Malfeito-Ferreira, Manuel; Brito, Luisa

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 coagulasenegative 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 g/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.

2023-07Journal article

Open access

Antibiotic resistance and virulence encoding genes are present in bacteria isolated from water and street food sold in Mozambique

Publication . Salamandane, Acácio Rosse; Malfeito Ferreira, Manuel; Brito, Luísa

The main objective of this study was, to evaluate the microbiological quality and safety of water and RTE foods sold on the streets of Maputo. For this, 83 RTE street food samples from 83 different vendors and 116 water samples from different sources were analyzed. Selected bacterial isolates were molecularly identified and characterized. High levels of unsatisfactory samples were found in both hot (76.7%) and cold (75%) foods. Based on staphylococcal counts, approximately 25% of the food samples were unsatisfactory/potentially hazardous. A high level of fecal contamination was detected in all types of water samples. In Escherichia coli isolates from food and water, the highest percentages of resistance were for the ß-lactams imipenem (35.5 and 39.3%, respectively) and ampicillin (39.3 and 46.4%, respectively). Multidrug resistance was observed in 31.3% of the isolates, being higher in water isolates (45.5%) than food isolates (19.2%). ESBL was the most frequent (57.7%) antibiotic resistance gene among those encoding β-lactamases, while tetA was the most frequent (50%) among non-β-lactamase genes. Furthermore, 73% of the multidrug-resistant E. coli isolates also had virulence genes. The most frequent virulence gene was sec (30.3%) followed by the hlb (24.2%) and sak and sed genes (12.5% each). Regarding the presence of antibiotic resistance genes in Staphylococcus, blaZ (penicillin resistance) was the most frequent (74.2%) followed by mecA (methicillin resistance) and vancA (vancomycin resistance) genes (43.9% and 42.4%, respectively. Staphylococcus isolates had a high ability to form biofilms on different materials and these biofilms were resistant to high concentrations of methicillin (32 g/ml). The results reported here show that water and food sold on the streets of Maputo, Mozambique, pose a potential risk to public health.

2024-06-17Doctoral thesis

Open access