Adhesion of Pathogenic Bacteria to Food Contact Surfaces: Influence of pH of Culture

Table 4

Surface tension and hydrophobicity (mJ⋅m⁻²) of the four pathogens determined from contact angle measurement.

Organism	pH	𝛾^LW𝑆	𝛾^+𝑆	𝛾^−𝑆	𝛾^AB𝑆	𝛾^TOT	Δ𝐺mwm^1
A. hydrophila	6	35.3±1.0^a	1.9±0.2^b	53.0±0.4^a	20.0±1.0^b	55.3±0.1^a	26.3±0.2^b
	7	35.4±0.7^a	1.5±0.1^b	54.1±0.3^a	18.2±0.8^b	53.6±0.1^a	28.7±0.4^a
	8	35.8±0.4^a	1.7±0.0^b	53.6±0.0^a	18.1±0.0^b	53.9±0.4^a	27.8±0.3^ab
E. coli 0157:H7	6	37.4±0.1^bc	1.5±0.2^a	52.3±1.3^a	17.9±1.3^a	55.3±1.2^a	24.9±0.8^c
	7	38.5±0.1^a	1.4±0.1^a	54.0±0.1^a	17.3±0.3^a	55.8±0.3^a	26.2±0.0^b
	8	38.2±0.6^ab	1.6±0.2^a	53.5±0.4^a	17.9±1.0^a	56.0±0.3^a	25,6±0.4^bc
S. enteritidis	6	36.1±0.7^d	1.7±0.0^a	49.8±0.8^b	18.3±0.3^a	54.4±0.5^a	23.0±1.4^a
	7	38.1±0.0^ab	1.0±0.1^a	51.1±0.2^ab	14.0±0.7^a	52.1±0.7^a	25.1±0.7^a
	8	38.6±0.3^a	1.0±0.2^a	52.0±0.3^a	14.2±1.3^a	52.8±1.0^a	25.6±0.9^a
S. aureus	6	37.5±0.3^b	1.6±0.1^a	46.0±3.5^b	17.0±0.3^a	54.5±0.0^a	17.8±4.4^c
	7	39.7±0.1^a	0.9±0.2^b	54.6±1.3^a	14.2±1.1^b	53.8±1.0^a	27.7±2.1^ab
	8	36.5±0.1^b	1.0±0.1^b	54.7±0.5^a	15.0±0.4^b	51.6±0.3^b	33.4±0.8^a

1Free energy of aggregation of the microorganisms in water where 𝛾^LW_𝑆,𝛾⁺_𝑆,𝛾⁻_𝑆,𝛾^𝐵_𝑆, and 𝛾^TOT are, respectively, the Lifshitz-van der Waals contribution energies, electron acceptor (acid), and electron donor (basic) components of the wetting agent and bacterial lawn, Lewis acid-base bonds and the total surface energy of the bacteria.
a-d In a column, for a given bacterium, values with the same letter are not significantly different (𝑃>.05).