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<p>Advanced water treatment (AWWT) from urban centers is taking on greater ecological and public health importance with the emergence of more antibiotic-resistant pathogens entering coastal oceans. This research elucidates the behavior of β <i>Streptococcus agalactiae</i> (βHS) isolated from the Southern Mediterranean Seas near areas frequented by swimmers and beach tourists. βHS was isolated from the Hammamet Gulf off Northeastern Tunisia. The isolated bacterial strain was tested for its ability to grow and to form biofilms, a characteristic that exacerbates its pathology. Initial bacteria cultures under starvation showed exponential growth for the first 6&#xa0;days of incubation followed by a growth plateau. The bacterial culture formed a biofilm after 2&#xa0;days of starvation conditions. Cultures continuously starved beyond 6&#xa0;days showed an inhibition of biofilm formation. βHS cultures submitted to ferrous sulfate (FeSO<sub>4</sub>), below 20&#xa0;mM, showed both growth and biofilm formation. However, exposure of βHS cultures to over 20&#xa0;mM FeSO<sub>4</sub> showed toxicity to bacterial cells and restricted biofilm formation. In contrast, exposure to all concentrations of zinc sulfate (ZnSO<sub>4</sub>) and copper sulfate (CuSO<sub>4</sub>) (from 10, 20 and 50&#xa0;mM) reduced βHS culture growth and limited biofilm formation. In addition, βHS was sensitive to germicidal ultraviolet light (UV<sub>254</sub>) exposure; increasing UV<sub>254</sub> doses (0, 30, 60, 120 and 240&#xa0;mJ/cm<sup>2</sup>) affected the βHS culture growth. βHS cultures showed resistance to tetracycline (30&#xa0;μg), clindamycin (2&#xa0;μg), erythromycin (15&#xa0;μg), and levofloxacin (5&#xa0;μg) and were sensitive only to penicillin (10 U) when tested for antibiotic susceptibilities (AS) These findings may serve to raise public health awareness to develop strategies limiting the continuous pollution from sewage effluent and trigger policies to require AWWT of effluent before discharging sewage into coastal oceans.</p>

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Hemolytic Streptococcus agalactiae isolation and identification from the Southern Mediterranean Sea and effect on growth- and biofilm-forming ability under stressful environment

  • 期刊论文

  • 发表日期：

    2025年6月6日

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  • Imen Laadouze,
  • Noussaiha Salhi,
  • Ibtissem Khouja,
  • Emna Grami,
  • Kathleen Sullivan Sealey,
  • Neila Saidi

摘要

Advanced water treatment (AWWT) from urban centers is taking on greater ecological and public health importance with the emergence of more antibiotic-resistant pathogens entering coastal oceans. This research elucidates the behavior of β Streptococcus agalactiae (βHS) isolated from the Southern Mediterranean Seas near areas frequented by swimmers and beach tourists. βHS was isolated from the Hammamet Gulf off Northeastern Tunisia. The isolated bacterial strain was tested for its ability to grow and to form biofilms, a characteristic that exacerbates its pathology. Initial bacteria cultures under starvation showed exponential growth for the first 6 days of incubation followed by a growth plateau. The bacterial culture formed a biofilm after 2 days of starvation conditions. Cultures continuously starved beyond 6 days showed an inhibition of biofilm formation. βHS cultures submitted to ferrous sulfate (FeSO4), below 20 mM, showed both growth and biofilm formation. However, exposure of βHS cultures to over 20 mM FeSO4 showed toxicity to bacterial cells and restricted biofilm formation. In contrast, exposure to all concentrations of zinc sulfate (ZnSO4) and copper sulfate (CuSO4) (from 10, 20 and 50 mM) reduced βHS culture growth and limited biofilm formation. In addition, βHS was sensitive to germicidal ultraviolet light (UV254) exposure; increasing UV254 doses (0, 30, 60, 120 and 240 mJ/cm2) affected the βHS culture growth. βHS cultures showed resistance to tetracycline (30 μg), clindamycin (2 μg), erythromycin (15 μg), and levofloxacin (5 μg) and were sensitive only to penicillin (10 U) when tested for antibiotic susceptibilities (AS) These findings may serve to raise public health awareness to develop strategies limiting the continuous pollution from sewage effluent and trigger policies to require AWWT of effluent before discharging sewage into coastal oceans.