Biofilm-forming and antimicrobial resistance traits of staphylococci isolated from goat dairy plants.

Myrella Cariry Lira,Francisca Geovânia Canafístula De Sousa,Marciane Magnani,Celso José Bruno De Oliveira,Paricia Emília Naves Givisiez,Denis Augusto Spricigo,Evandro Leite De Souza,Wondwossen Abebe Gebreyes

doi:10.3855/jidc.6714

Abstract

Biofilm-associated antimicrobial resistance is of increasing importance to the maintenance and spread of foodborne pathogens in the food industry. This study aimed to investigate the ability to form biofilm and the antimicrobial resistance of staphylococci contaminating small-scale goat milk dairy plants. Sixty isolates were tested for antimicrobial resistance against 20 drugs by the microdilution method. Biofilm-forming traits were assessed by the microtiter plate method (MtP), Congo red agar method (CRA), and icaD gene detection by polymerase chain reaction (PCR). High antimicrobial resistance to ampicillin (60/60; 100%), penicillin G (21/60; 35%), and erythromycin (15/60; 25%) was observed, but all isolates were susceptible to amoxicillin/K-clavulanate, ceftriaxone, ciprofloxacin, gentamicin, levofloxacin, linezolid, and moxifloxacin. No resistance to oxacillin or vancomycin was seen among Staphylococcus aureus. Twenty-seven isolates (27/60; 45%) were considered to form biofilm according to MtP, and similar biofilm-producing frequencies were observed in coagulase-negative staphylococci (CoNS) (20/44; 45.4%) and S. aureus (7/16; 43.7%). The icaD gene was observed only in S. aureus isolates. There was no association between biofilm production and antimicrobial resistance. A higher frequency of biofilm-producing staphylococci was found in isolates from bulk tank milk and hand swabs. On the other hand, isolates from pasteurized milk showed lower frequency of biofilm formation. Staphylococci contaminating goat dairy plants are potential biofilm producers. The results suggest no association between the ability to form biofilm and antimicrobial resistance.

Highlights

Biofilm-associated antimicrobial resistance is of increasing importance to the maintenance and spread of foodborne pathogens in the food industry
High antimicrobial resistance was observed for ampicillin (60/60 isolates; 100%), penicillin G (21/60 isolates; 35%) and erythromycin (15/60 isolates; 20%)
The high frequency of S. aureus or coagulase-negative staphylococci (CoNS) isolates positive for biofilm formation by MtP might be explained by the high capacity of those organisms to produce biofilm in natural ecosystems, such as those found in milk-processing plants

Summary

Introduction

Biofilm-associated antimicrobial resistance is of increasing importance to the maintenance and spread of foodborne pathogens in the food industry. This study aimed to investigate the ability to form biofilm and the antimicrobial resistance of staphylococci contaminating small-scale goat milk dairy plants. Twenty-seven isolates (27/60; 45%) were considered to form biofilm according to MtP, and similar biofilm-producing frequencies were observed in coagulase-negative staphylococci (CoNS) (20/44; 45.4%) and S. aureus (7/16; 43.7%). Conclusions: Staphylococci contaminating goat dairy plants are potential biofilm producers. The goat production chain comprises mostly family producers, and the milk is pasteurized in small-scale dairy plants before being distributed to public schools in the scope of social programs of the federal government [1]. We showed that both Staphylococcus aureus and coagulase-negative staphylococci (CoNS) isolated from different goat milk processing plants harbor classic and novel enterotoxin-encoding genes [3]. S. aureus is involved in innumerous cases and outbreaks of food poisoning worldwide, and the consumption of contaminated dairy products has been

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