Urinary tract infections (UTIs), caused by Escherichia coli 80% to 85% of the time, are one of the most important causes of morbidity and health care spending affecting persons of all ages. These infections lead to many difficult problems, especially increasing resistance to antibiotic drugs. Bacterial biofilms play an important role in UTIs, responsible for persistent infections leading to recurrences and relapses. In this study, we have investigated the antibacterial activity of five medicinal plant essential oils against UTIs caused by E. coli using disc diffusion and minimal inhibition concentration (MIC) methods. In addition, biofilm inhibitory action of oils was realized by crystal violet. Gas chromatography–mass spectrometry (GC–MS) analysis showed a variability between oils in terms of compound numbers as well as their percentages. Antibacterial activity was observed only in cases of Origanum majorana, Thymus zygis and Rosmarinus officinalis, while Juniperus communis and Zingiber officinale did not showed any effect towards E. coli isolates. T. zygis essential oil demonstrated the highest antibacterial activity against E. coli isolates, followed by O. majorana and R. officinalis. Further, oils showed high biofilm inhibitory action with a percentage of inhibition that ranged from 14.94% to 94.75%. R. officinalis oil had the highest antibiofilm activity followed by T. zygis and O. majorana. Accordingly, tested oils showed very effective antibacterial and antibiofilm activities against E. coli UTIs and can be considered as good alternative for antibiotics substitution.

Thirty-five Staphylococcus aureus strains from auricular infections were isolated. The identification of strains was confirmed by Api ID 32 Staph strips, the antibiotic susceptibility test was performed using ATB Staph kit. PCR assay was used to detect the oxacillin resistance gene (mecA) and the erythromycin genes (ermA, ermB, ermC, msrA and mef). The susceptibility profile of all strains revealed a low resistance level to oxacillin and erythromycin. The PCR results show that 60 % of the strains are mecA positive. The frequency of erythromycin genes was: ermA (+) 22.8 %, ermB (+) 45.7, ermC (+) 17.1, msrA (+) 28.6. The mef gene was not detected in any strain. No correlations between genotypic and phenotypic methods for the determination of oxacillin and erythromycin resistance was found. However, multiplex PCR technique was shown to be a fast, practical and economic technique for the detection of methicillin-and erythromycin-resistant staphylococci.

In seawater, enteric bacteria evolve toward a stressed state that is difficult to identify because of major alterations of their phenotype. In this study, we incubated four reference strains of S. enterica serovar Typhimurium in seawater microcosms for 10 months and studied the modifications of their main phenotypic characters. All of the strains lost some key characters used for traditional identification of the Salmonella genus. They became able to produce acetoin, and tryptophane deaminase activity became positive, but they lost the capacity to use rhamnose. We were able to show some modifications of the level of enzymatic profile as well as in their antibiotic susceptibility. The atypical cells of S. enterica serovar Typhimurium were identified by polymerase chain reaction (PCR) methods using the internal transcribed spacer region, and they were confirmed by multiplex PCR after the simultaneous amplification of the phoP, Hin, and H-li genes.

The marine bacteria Vibrio parahaemolyticus and V. alginolyticus were incubated in seawater for 8 months to evaluate their adaptative responses to starvation. The starved cells showed an altered biochemical and enzymatic profiles, respectively, on Api 20E and Api ZYM systems and an evolution to the filterable minicells state capable to pass membrane pore size 0.45 microm. Outer membrane proteins patterns of stressed bacteria were also altered. Indeed, these modifications were manifested by the appearance and/or disappearance of bands as well as in the level of expression of certain proteins. Plasmids profiles analysis showed that V. alginolyticus ATCC 33787 lost three plasmids, whereas other tested strains conserved their initial profiles.

The presence of the ica loci and adhesins genes in clinical Staphylococcus aureus strains were considered important factors of virulence. In this study, 46 strains of Staphylococcus aureus were isolated from auricular infection, and were investigated for slime production using Congo Red Agar method (CRA). In order to detect the adhesins genes (ica A, ica D, fnb A, cna, Clf A) Polymerase Chain Reaction was used. Qualitative biofilm production of S. aureus using CRA plates revealed that 56.5% of strains were slime producers. In addition 78.26% of strains were ica A and ica D positive. While the fnbA gene was present in 76.1% of isolated strains. Furthermore, 56.5% of strains have the cna gene and 30.4% were clfA positives. Overall this study confirms the presence of fnb A and ica A/ica D genes in the majority of studies S. aureus strains isolated from Staphylococcal sepsis.

In this study we investigated the phenotypic slime production of Vibrio alginolyticus and Vibrio parahaemolyticus strains, food-borne pathogens, using a Congo red agar plate assay. Furthermore, we studied their ability to adhere to abiotic surfaces and Vero cells line. Our results showed that only V. alginolyticus ATCC 17749 was a slime-producer developing almost black colonies on Congo red agar plate. Adherence to glace tube showed that all V. alginolyticus strains were more adherent than V. parahaemolyticus. Only V. alginolyticus ATCC 17749 was found to be able to form biofilm on polystyrene microplate wells (OD570 = 0.532). Adherence to Vero cells showed that all tested strains were non adherent after 30 min, however after 60 min all the studied strains become adherent. The percentage of adherence ranged from1.23% to 4.66%.

Vibrio parahaemolyticus and Vibrio alginolyticus were subjected to g-irradiation (0.5 kGy) or starvation by incubation for 8 months in seawater to study modifications in their outer membrane protein patterns. After treatment, outer membrane protein profiles of starved or g-irradiated bacteria were found to be altered when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Altered proteins were identified by mass spectrometry (MS and MS/MS) and analyses revealed that OmpU can be considered a starvation stress-induced protein. In addition, expression of OtnA, OmpW, OmpA and peptidoglycan-associated lipoprotein decreased to non-detectable levels in starved cells. Furthermore, MltA-interacting protein MipA appeared under g-irradiation or starvation conditions. Thus, it can be considered to be a g-irradiation, long-term starvation stress protein in some vibrios.

In this study, we investigated the survival and adhesion ability of Shigella after their incubation in seawater microcosms at ambient temperature and at 4°C during 1 month. Our results showed that the number of cells was considerably decreased after this period of stress. In addition, we have revealed some modifications in the biochemical and enzymatic profiles of stressed cells. These modification were noted by the appearance or/and the disappearance of some activities. Indeed, antibiotic susceptibility of stressed cells has been changed. Adherence assays to KB cells showed on increase in the number of adherent cells from 0.7 to 6.7% after 1 month of incubation in seawater.