Laboratório de Inspeção de Produtos de Origem Animal, Universidade Federal de Viçosa, Departamento de Veterinária, Campus Viçosa, Centro, 36570-900 Viçosa, Minas Gerais, Brazil (ORCID: https://orcid.org/0000-0002-4954-5824 [L.A.N.]).
3M Food Safety, 3M do Brasil, Via Anhanguera, s/n - Nova Veneza, 13181-900 Sumaré, São Paulo, Brazil.
J Food Prot. 2020 Oct 1;83(10):1757-1763. doi: 10.4315/JFP-20-155.
This study aimed to evaluate the behavior of Petrifilm Lactic Acid Bacteria Count Plates (PLAB) as an alternative methodology to enumerate lactic acid bacteria (LAB) in bacon. Bacon samples (n = 40) were obtained from retail sale, 10-fold diluted with buffered peptone water (BPW, 0.2% [w/v]) and Letheen broth, and subjected to LAB enumeration according to four protocols: (i) de Man Rogosa Sharpe (MRS) agar, pH 5.7, 30°C; (ii) MRS, pH 5.7, 30°C, anaerobiosis; (iii) all-purpose Tween agar (APT), 25°C; and (iv) PLAB, 30°C. Colonies were enumerated at 24, 48, and 72 h, and the results expressed as log CFU per gram for comparison by analysis of variance and regression (P < 0.05). Furthermore, colonies were randomly selected and characterized as LAB (Gram staining and catalase). Mean LAB counts from MRS and PLAB did not present significant differences independently of incubation time or diluent (P > 0.05), whereas counts in APT with BPW after 24 h were significantly lower (P < 0.05). PLAB counts with BPW (24, 48, and 72 h) presented significant correlation with MRS (r ranging from 0.87 to 0.89; in anaerobiosis, r ranging from 0.94 to 0.95) and APT (r ranging from 0.84 to 0.86). With Letheen broth, PLAB (24, 48, and 72 h) presented significant correlation with MRS (r ranging from 0.92 to 0.94; in anaerobiosis, r ranging from 0.93 to 0.96) and APT (r ranging from 0.77 to 0.79). In total, 1,032 colonies (97%) from 1,063 colonies were characterized as LAB. Thus, PLAB can be considered as an alternative tool for enumerating LAB in bacon, with reliable results even after 24 h of incubation.
本研究旨在评估 Petrifilm 乳酸菌计数平板（PLAB）作为替代方法，用于检测培根中的乳酸菌（LAB）。从零售渠道获得 40 份培根样品，用缓冲蛋白胨水（BPW，0.2%[w/v]）和 Letheen 肉汤进行 10 倍稀释，根据以下四种方案进行 LAB 计数：（i） de Man Rogosa Sharpe（MRS）琼脂，pH5.7，30°C；（ii）MRS 琼脂，pH5.7，30°C，厌氧菌；（iii）多用途吐温琼脂（APT），25°C；（iv）PLAB，30°C。24、48 和 72 小时时计数菌落，方差分析和回归分析（P<0.05）比较结果表示为每克菌落形成单位（log CFU）。此外，随机选择菌落并鉴定为 LAB（革兰氏染色和过氧化氢酶）。MRS 和 PLAB 的 LAB 计数平均值无论孵育时间或稀释液如何均无显著差异（P>0.05），而在 24 小时后用 BPW 的 APT 计数显著较低（P<0.05）。PLAB 计数与 MRS（r 范围从 0.87 到 0.89；在厌氧菌中，r 范围从 0.94 到 0.95）和 APT（r 范围从 0.84 到 0.86）用 BPW（24、48 和 72 小时）呈显著相关性。用 Letheen 肉汤，PLAB（24、48 和 72 小时）与 MRS（r 范围从 0.92 到 0.94；在厌氧菌中，r 范围从 0.93 到 0.96）和 APT（r 范围从 0.77 到 0.79）呈显著相关性。总共有 1063 个菌落中的 1032 个（97%）被鉴定为 LAB。因此，PLAB 可被视为检测培根中 LAB 的替代工具，即使在孵育 24 小时后也能得到可靠的结果。
