Listeria monocytogenes insertion mutants defective in hemolysin production were generated using the conjugative transposons Tn916 and Tn1545. All of the nonhemolytic mutants (hly-) lacked a secreted 58-kD polypeptide, presumedly hemolysin, and were avirulent in a mouse model. An intracellular multiplication assay was established in monolayers of mouse bone marrow-derived macrophages, the J774 macrophage-like cell line, the CL.7 embryonic mouse fibroblast cell line, and the Henle 407 human epithelial cell line. The hly+ strain grew intracellularly in all of the tissue culture cells with a doubling time of approximately 60 min. In contrast, the hly- mutants failed to grow in the murine-derived tissue culture cells, but retained the ability to grow in the human tissue culture cells examined. Hemolytic-positive revertants were selected after passage of the hly- mutants through monolayers of J774 cells. In each case, the hemolytic revertants possessed the 58-kD polypeptide, were capable of intracellular growth in tissue culture monolayers and were virulent for mice.

Abstract Introduction: Unprecedented global increases in involuntary migration have created large populations of forcibly displaced people, who are disproportionately likely to have experienced abuse and torture. We undertook this study to better understand the frequency and consequences of specific types of torture and abuse within an immigrant population in our community, San Francisco, East Bay. Methods and Results: We conducted a cross-sectional study of 59 Eritreans seeking asylum in the United States presenting to a human rights clinic for forensic medical and psychological evaluations. Demographic features of individuals, reported history and specific types of torture, and physical and psychological sequelae were analyzed. Over 300 instances of torture were reported, an average of about 6 per person. The primary forms of torture reported were beating and forced positioning, and many others were reported sporadically. 90% of asylum seekers examined had clinical findings which were consistent with the torture they reported, and some physical findings had clinical as well as forensic significance. 86% met diagnostic criteria for post-traumatic stress disorder. Discussion: Forcibly displaced people are likely to have witnessed and experience violence, deprivation, and abuse, and for this reason bear a disproportionate burden of physical, psychological, and social morbidity. Our study describes the epidemiology of torture and its consequences in a specific population, and demonstrates why understanding local and general epidemiology of torture and other forms of abuse is necessary to provide excellent biopsychosocial care to forcibly displaced people.

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