An outbreak of needlestick injuries in hospital employees due to needles piercing infectious waste containers

OBJECTIVES: To investigate the cause of an outbreak of needlestick injuries (NSIs) in hospital employees. SETTING: A 700-bed university hospital. DESIGN: Outbreak investigation, laboratory evaluation of a medical waste disposal device, cost analysis. METHODS: Employee health department records were reviewed of workers suffering sticks from needles piercing fiberboard-contaminated material containers (CMCs). A laboratory evaluation of needle-puncture resistance properties of the CMCs was performed using a testing apparatus. The cost of a hospital waste disposal program using fiberboard CMCs was compared with the cost of a program using rigid plastic (polypropylene) boxes. RESULTS: During 40 months of surveillance in 1986 and from 1989 to 1991, only one NSI had occurred from a needle piercing a CMC. During 9 months in 1993, 13 NSIs occurred due to needles piercing CMCs (P < .001). No clinical illness resulted from the NSIs. The outbreak was halted by a temporary change to plastic (polypropylene) boxes for sharps disposal ($4.92 to $23.33/cu ft) until receipt of a box with a newly designed solid fiberboard liner ($1.25/cu ft). CMC liners used during the epidemic had a mean needle puncture resistance of 527 g, as compared with 660 g for liners used before the outbreak (P < .001). The new solid fiberboard liner has a mean puncture resistance of 1,765 g. A program of waste disposal using fiberboard CMCs was found to cost approximately one-seventh the cost of a program using plastic boxes for disposal of infectious waste. CONCLUSION: A program for infectious waste disposal using fiberboard CMCs can be safe and cost-effective if appropriate standards for puncture resistance are met.     

A room-based diagnostic imaging system for measurement of patient setup

A room-based diagnostic x-ray imaging system for routine measurement of radiotherapy patient orientation has been developed. The system consists of a pair of room-mounted x-ray tubes and a portable imager consisting of an orthogonal pair of phosphor screens, a mirror/lens system, a CCD camera, and computer software for comparing images of the patient to reference images. Orthogonal pairs of images can be acquired quickly and with relatively little exposure, allowing correction of patient setup on a daily basis. This could limit patient setup error to the uncertainty in the measurement and repositioning processes, a potentially significant improvement over the present standard.     

HIV-1 Nef protein protects infected primary cells against killing by cytotoxic T lymphocytes

Cytotoxic T lymphocytes (CTLs) lyse virally infected cells that display viral peptide epitopes in association with major histocompatibility complex (MHC) class I molecules on the cell surface. However, despite a strong CTL response directed against viral epitopes, untreated people infected with the human immunodeficiency virus (HIV-1) develop AIDS. To resolve this enigma, we have examined the ability of CTLs to recognize and kill infected primary T lymphocytes. We found that CTLs inefficiently lysed primary cells infected with HIV-1 if the viral nef gene product was expressed. Resistance of infected cells to CTL killing correlated with nef-mediated downregulation of MHC class I and could be overcome by adding an excess of the relevant HIV-1 epitope as soluble peptide. Thus, Nef protected infected cells by reducing the epitope density on their surface. This effect of nef may allow evasion of CTL lysis by HIV-1-infected cells.     

Mechanisms for selective toxicity of fipronil insecticide and its sulfone metabolite and desulfinyl photoproduct

Fipronil, an N-phenylpyrazole with a trifluoromethylsulfinyl substituent, initiated the second generation of insecticides acting at the gamma-aminobutyric acid (GABA) receptor to block the chloride channel. The first generation includes the polychlorocycloalkanes alpha-endosulfan and lindane. In this study, we examine the mechanisms for selective toxicity of the sulfoxide fipronil and its sulfone metabolite and desulfinyl photoproduct relative to their target site interactions in vitro and ex vivo and the importance in fipronil action of biooxidation to the sulfone. Differences in GABA receptor sensitivity, assayed by displacement of 4'-ethynyl-4-n-[2, 3-3H2]propylbicycloorthobenzoate ([3H]EBOB) from the noncompetitive blocker site, appear to be a major factor in fipronil being much more toxic to the insects (housefly and fruit fly) than to the vertebrates (humans, dogs, mice, chickens, quail, and salmon) examined; in insects, the IC50s range from 3 to 12 nM for fipronil and its sulfone and desulfinyl derivatives, while in vertebrates, the IC50 average values are 1103, 175, and 129 nM for fipronil, fipronil sulfone, and desulfinyl fipronil, respectively. The insect relative to the vertebrate specificity decreases in the following order: fipronil > lindane > desulfinyl fipronil > fipronil sulfone > alpha-endosulfan. Ex vivo inhibition of [3H]EBOB binding in mouse brain is similar for fipronil and its sulfone and desulfinyl derivatives at the LD50 dose, but surprisingly, at higher doses fipronil can be lethal without detectably blocking the [3H]EBOB site. The P450 inhibitor piperonyl butoxide, acting in houseflies, increases the metabolic stability and effectiveness of fipronil and the sulfone but not those of the desulfinyl compound, and in mice it completely blocks the sulfoxide to sulfone conversion without altering the poisoning. Thus, the selective toxicity of fipronil and fipronil-derived residues is due in part to the higher potency of the parent compound at the insect versus the mammalian GABA receptor but is also dependent on the relative rates of conversion to the more persistent and less selective sulfone metabolite and desulfinyl photoproduct.