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Susceptibilities of 66 Brucella isolates were tested in vitro. All isolates were susceptible to doxycycline, gentamic in and streptomycin. In addition, propyl paraben, cresol and benzalkoniumchloride were found to be the most powerful tested preservative, disinfectant and antiseptic, respectively. All isolates adhered to and invaded into Vero cells by variable degrees. Adherence and invasion of most isolates were significantly reduced by: (1) pretreatment of test isolates with trypsin and sodium metaperiodate; (2) pretreatment of Vero cells with lipase, neuraminidase and sodium metaperiodate; (3) Presence of Ca ++ , Mg ++ and 200mM mannose in the assay medium and (4) growth of test isolates in half MICs of different antimicrobial agents. On the other hand, pretreatment of Vero cells with trypsin increased the adherence and invasion of most test isolates. No significant change in adhesion and invasion by changing the temperature from 27°C to 42°Cor the pH from 6 to 8. Log phase cultures showed higher adherence and invasion than stationary phase cultures.

Respiratory tract infections are one of the leading causes of morbidity and mortality. There is considerable epidemiologic evidence that infection with respiratory viruses increases the incidence and severity of secondary bacterial complications. However, very limited number of studies were concerned with the mechanism behind such synergy. In this context, our study aimed to explore the interaction between Group A Streptococcus pyogenes (GAS) and Influenza A virus (IAV). Our results revealed that the GAS adherence and internalization into Madin-Darby canine kidney (MDCK) cells markedly increased after IAV infection. When M6 protein defective mutant of GAS was used, the virus enhanced adherence and internalization was nearly abolished indicating the involvement of M protein binding sites on the MDCK cell surface. Interestingly, the modulation of some O-linked glycolproteins as well as sialic acid, mucin and fibrinogen-like residues on the surface of MDCK cells contributed to augmented bacterial adherence and/or internalization. In the same way, qRT-PCR experiments showed an overexpression of the membrane associated mucin (MUC1) on the surface of the MDCK cells after IAV infection. Altogether, the present study revealed that IAV infection augments the adherence and internalization of GAS to MDCK cells via modulation of membrane associated O-linked glycoproteins, fibrinogen, sialic acid residues and the mucin, MUC1 on the surface of MDCK cell.

In this article, some mucolytic agents were tested for their activity to prevent bacterial adherence to mammalian cells. Preliminary screening for antiadherent activity showed that ambroxol, bromhexine, ammonium chloride, and ammonium acetate but neither guaiphenesin nor carbocysteine significantly reduced the adherence of the tested clinical isolates to cultured mammalian cells. The antiadherent effect of such agents was observed when mammalian cells were treated with these agents either before or after bacterial adherence, and this effect was exhibited in a dose-dependent manner. The minimum concentrations of ambroxol, bromhexine, ammonium chloride, and ammonium acetate required for mammalian cells treatment to prevent bacterial adherence were 2.5, 5, 50, and 20 ng/ml, respectively, whereas significantly higher mucolytic concentrations were required to eradicate bacteria that adhered to mammalian cells. Upon treatment of mammalian cells with mucolytics, the maximum reduction in adherence of the tested isolates attained by ambroxol, bromhexine, ammonium chloride, ammonium acetate were 99%, 98%, 75%, and 54% to that of control, respectively. Insignificant difference existed between the antiadherent activities of ambroxol and bromhexine, while both agents had significantly higher effect than ammonium chloride and ammonium acetate. Pretreatment of the immobilized mucin with ambroxol, bromhexine, ammonium chloride, or ammonium acetate reduced the adherence of Pseudomonas aeruginosa, Escherichia coli, and staphylococcal isolates to this receptor analogue. A strong correlation was observed for the antiadherent activity of the tested mucolytics in case of mammalian cells and immobilized mucin. Moreover, pretreatment of the immobilized receptor analogues chondroitin sulfate-B and heparin with the abovementioned agents significantly reduced the adherence of Staphylococcus aureus, P. aeruginosa, and E. coli isolates to such immobilized glycoproteins.

In the present study the role of different mammalian cell receptors in adherence of the coagulase positive pathogen, Staphylococcus aureus and some coagulase negative staphylococci, namely Staphylococcus epidermidis and Staphylococcus saprophyticus was investigated. Upon testing the adherence to Vero and Hep-2 cells, S. aureus isolates showed an adherence to both cell lines while S. epidermidis and S. saprophyticus isolates adhered to Vero cells only. According to the obtained results, both O-linked and N-linked mammalian cell surface glycoproteins are involved in the adherence of S. aureus isolates to Vero and Hep-2 cells, whereas only the O-linked ones serve as receptors for adherence of S. epidermidis and S. saprophyticus isolates to Vero cells. Of the O-linked glycoproteins, GAG-like receptors are involved in adherence of all tested isolates to Vero cells. The coagulase positive staphylococci preferred to adhere to the highly sulphated GAGs (Heparin and chondroitin sulphate B) while the coagulase negative isolates showed higher affinity to the less sulphated ones (Chondroitin sulphate A and C). Mucin like receptors appeared to be important for the adherence of all tested staphylococci. The role exhibited by fibronectin- and fibrinogen-like receptors was detected with S. aureus and S. epidermidis but not with S. saprophyticus isolates. While, collagen and gelatin were found to contribute to the adherence of S. aureus isolates only. Neither carbohydrate moieties of the glycoconjugates nor lipid molecules on the mammalian cell surface played a role in the adherence of the tested staphylococcal isolates. Taken together, the results revealed that both coagulase negative and coagulase positive staphylococcal tested isolates adhere to the same classes of mammalian cell surface receptors such as mucin-like, fibrinogen-like, fibronectin-like and GAG-like receptors. However, the tested isolates exhibited different degrees of affinities to such receptors., ((c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)