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Biomedical subjects

F D Lowy

Publications and source records attributed to F D Lowy.

At least 19 recordsLinked to original sources
PubMed2003

Staphylococcus aureus colonization in a community sample of HIV-infected and HIV-uninfected drug users.

HIV-infected individuals, especially those with a history of injecting drug use, are at high risk of Staphylococcus aureus infection. Moreover, the use of antimicrobial agents for opportunistic infections may increase nasal colonization by antimicrobial-resistant Staphylococcus aureus in this population and, subsequently, levels of infection with multidrug-resistant Staphylococcus aureus in the community. Between February 1999 and March 2000, 500 subjects from a community-based cohort of drug users completed an interview and underwent a physical exam. Risk factors for colonization by Staphylococcus aureus were examined, the antibiotic susceptibility profiles of all strains were determined, and DNA strain analysis was performed. One hundred twenty (24%) subjects had positive Staphylococcus aureus nasal cultures. Only HIV infection and homelessness were associated with Staphylococcus aureus colonization. Ten (8%) isolates were methicillin-resistant Staphylococcus aureus. Methicillin-resistant Staphylococcus aureus isolates were found more frequently among HIV-infected than HIV-uninfected respondents (14% vs. 3%, P=0.04). Among those colonized and HIV infected, the mean number of resistant isolates was higher for those currently reporting antibiotic use (5.0 vs. 2.3, P<0.001) and for those with CD4+ counts <or =200/ microl (3.8 vs. 2.3, P=0.02). The increased use of antimicrobial agents in HIV-infected individuals colonized with Staphylococcus aureus may be an underlying mechanism that contributes to the presence of multidrug-resistant Staphylococcus aureus in the community.

AIDS-Related Opportunistic Infections↗
PubMed2001

What determines nasal carriage of Staphylococcus aureus?

Nasal carriage of Staphylococcus aureus is an important risk factor for infection by this organism in both community and hospital settings; this article reviews the role of host and bacterial factors in carriage. A host genetic influence appears likely but the phenotypic determinants are unknown. Possibilities include variability in host adhesins, immune response or secretion of antimicrobial molecules. Colonization resistance by S. aureus, together with the observation that persistent carriers often carry a single strain whereas intermittent carriers can be colonized with unrelated strains over time, suggests that bacterial factors could also be involved.

Carrier State↗
PubMed2001

Multiple antibiotic changes during the first 72 hours of hospitalization.

BACKGROUND: Increasing concern about inappropriate antibiotic use prompted us to examine whether our patients were receiving frequent and perhaps unwarranted changes of antibiotic therapy. METHODS: We evaluated antibiotic prescribing by the physicians in the Emergency Department and by those on the inpatient medical service during the first 72 hours of hospitalization in 119 patients admitted with suspected serious infections to an acute care, university-affiliated, municipal teaching hospital. The appropriateness of antibiotic prescriptions was assessed independently and retrospectively by 2 infectious disease specialists (each based at a different hospital) using a 4-grade scale (from 1 = wrong choice to 4 = appropriate). Of their evaluations of the 427 antibiotic regimens given to the 119 patients during 4 defined intervals during their first 72 hours of hospitalization, 90% agreed with each other within 1 grade. Their evaluations were then compared with the selections that had been made at each interval by the prescribing physicians. RESULTS: Successive prescribing physicians changed the antibiotic regimens in 77% of cases during the first 24 hours and in 56% during the next 48, often without apparent clinical or microbiologic indications. By 72 hours, the 119 patients had received a mean of 3.1 +/- 1.3 (+/-SD) different antibiotics, and 40 received between 4 and 7. Only 7% of the patients had no change in the regimen prescribed originally. CONCLUSIONS: Many patients had multiple changes of antibiotics, often unnecessarily, resulting in exposure to too many agents.

Anti-Bacterial Agents↗
PubMed2000

Staphylococcal infections in the intensive care unit.

Staphylococcus aureus and coagulase-negative staphylococci are among the most common causes of nosocomial infections in the intensive care unit (ICU). The clinical presentation of staphylococcal device-related infections, pneumonias, or surgical wound infections is not unique. However, treatment of these infections is increasingly problematic because of the resistance of clinical isolates to a widening number of antimicrobial agents. The confluence of critically ill patients and the need for multiple invasive procedures, as well as the use of broad-spectrum antimicrobial agents in the ICU, set the stage for the emergence of these multidrug-resistant staphylococci. In the past 10 years, there has been a progressive increase in the overall resistance of staphylococci to antimicrobial agents. Conventional infection control measures, such as handwashing and isolation precautions, to prevent the spread of staphylococcal infections in the ICU setting remain of critical importance. New approaches, including the prophylactic use of topical antistaphylococcal agents to eliminate nasal colonization in high-risk ICU patients and the development of antistaphylococcal vaccines, are currently being investigated.

Cross Infection↗
PubMed2000

Prevention of endothelial cell cytokine induction by a Staphylococcus aureus lipoprotein.

Staphylococcal strain 8325-4, unlike other staphylococcal strains, fails to induce cytokine IL-1 and IL-6 gene expression in human endothelial cells. In the present investigation, this strain was shown to release a product that inhibited cytokine gene expression in endothelial cells infected with another staphylococcal strain. This inhibition was due to prevention of internalization, but not adherence, of bacteria by endothelial cells. Induction of endothelial cell cytokine gene expression by lipopolysaccharide was not affected by the staphylococcal supernatant. In contrast to endothelial cells, 8325-4 did not inhibit Wb-induced cytokine gene expression in monocytes. Further characterization of the inhibitory factor suggests that it is a lipoprotein and that both protein and lipid components play a role in its inhibitory function.

Animals↗
PubMed1997

Staphylococcus aureus nasal colonization in HIV-seropositive and HIV-seronegative drug users.

Nasal colonization plays an important role in the pathogenesis of Staphylococcus aureus infections. To identify characteristics associated with colonization, we studied a cross-section of a well-described cohort of HIV-seropositive and -seronegative active and former drug users considered at risk for staphylococcal infections. Sixty percent of the 217 subjects were Hispanic, 36% were women, 25% actively used injection drugs, 23% actively used inhalational drugs, 23% received antibiotics, and 35% were HIV-seropositive. Forty-one percent of subjects had positive nasal cultures for S. aureus. The antibiotic susceptibility patterns were similar to the local hospital's outpatient isolates and no dominant strain was identified by arbitrarily primed polymerase chain reaction (AB-PCR). Variables significantly and independently associated with colonization included antibiotic use (odds ratio [OR] = 0.37; confidence interval [CI] = 0.18-0.77), active inhalational drug use within the HIV-seropositive population (OR = 2.36; CI = 1.10-5.10) and female gender (OR = 1.97; CI = 1.09-3.57). Characteristics not independently associated included injection drug use, HIV status, and CD4 count. The association with active inhalational drug use, a novel finding, may reflect alterations in the integrity of the nasal mucosa. The lack of association between HIV infection and S. aureus colonization, which is contrary to most previous studies, could be explained by our rigorous control for confounding variables or by a limited statistical power due to the sample sizes.

AIDS-Related Opportunistic Infections↗
PubMed1997

Extracellular matrix heparan sulfate modulates endothelial cell susceptibility to Staphylococcus aureus.

The ability of extracellular matrix heparan sulfate to alter the susceptibility of human endothelial cells to S. aureus was investigated. Endothelial cells grown on extracellular matrix synthesized by S. aureus-infected endothelial cells were more susceptible to subsequent staphylococcal infection than endothelial cells grown on the extracellular matrix synthesized by untreated endothelial cells. Endothelial cells were more susceptible to S. aureus infection when 1) grown on heparitinase-treated extracellular matrix that removed heparan sulfate chains, 2) grown on extracellular matrix produced by chlorate-treated endothelial cells that reduced sulfation in the matrix heparan sulfate proteoglycans, 3) grown on heparan sulfate purified from extracellular matrix elaborated by infected endothelial cells, and 4) endothelial cells were chlorate-treated and therefore expressed desulfated cellular heparan sulfate proteoglycans. Extracellular matrix produced by S. aureus-infected endothelial cells contained heparan sulfate proteoglycans with reduced sulfation. The altered extracellular matrix with reduced sulfated heparan sulfate proteoglycans signalled the uninfected endothelial cells to produce under sulfated cellular heparan sulfate proteoglycans that increased S. aureus adherence to the endothelial cells.

Bacterial Adhesion↗
PubMed1997

Correlation of histopathologic and bacteriologic changes with cytokine expression in an experimental murine model of bacteremic Staphylococcus aureus infection.

Staphylococcus aureus infections are often life threatening. Relatively little is known about the host response to these infections, in particular, the role played by cytokines. We established a mouse model of bacteremic S. aureus infection to correlate bacteriologic findings and pathologic changes with cytokine gene expression. Bacterial density in blood and tissue was highest at 1 h and minimal by 48 h. Despite the rapid clearance of bacteria, pathologic abnormalities and inflammatory cytokines were detected after clearance of the bacteria. The number of infiltrating inflammatory cells, as well as the size of inflammatory foci, increased with time. Interstitial accumulation of inflammatory cells and tissue damage, such as microabscesses, edema, and necrosis progressed following clearance of bacteria from the tissues. Levels of tumor necrosis factor and interleukin-1 protein in serum were detectable at 1 h and peaked at 4 h. Interleukin-6 protein expression showed different kinetics, with low levels detected at 1 h and increasing levels at 72 h postinfection. Tumor necrosis factor and the interleukins were expressed in inflammatory and noninflammatory cells in lung, liver, and heart tissues. Leukocytes in the infected tissues were highly reactive with antibodies to the three cytokines, suggesting that activated leukocytes are a major source of inflammatory cytokines after staphylococcal infection. Expression of interleukin-1 and interleukin-6 in tissue-specific cells and endothelial cells was also detected in infected tissues, indicating that cells other than leukocytes contribute to the elevated cytokine levels in this model. Once initiated, expression of inflammatory cytokines contributes to the pathogenesis of S. aureus disease.

Animals↗
PubMed1996

Comparison of endovascular and conventional vascular prostheses in an experimental infection model.

INTRODUCTION: The causes and management of prosthetic graft infections have been extensively studied for conventional bypass grafts; however, the infectivity and therapy for endovascular graft infections are completely unknown. The aim of this study was to compare the biologic properties of infected aortic grafts when inserted by endoluminal or standard transabdominal techniques. METHODS: Eighteen dogs underwent placement of polytetrafluoroethylene grafts in their infrarenal aortas either by an endovascular technique (8) or a standard interposition technique (10). Endovascular grafts were constructed from polytetrafluoroethylene (3 cm) and two balloon-expandable stents coaxially mounted onto a balloon catheter delivery system. The grafts were inserted through a left carotid arteriotomy under fluoroscopic control. Initially, seven grafts were infected with decreasing inocula of Staphylococcus aureus, starting at 10(7) organisms per ml for 30 minutes and then rinsed briefly (10 seconds) in normal saline solution, until a 50% infective dose for the standard grafts was determined to be 10(2) organisms per ml. After this initial experiment, a second group of 11 dogs were compared at a concentration of 10(2) S. aureus per ml. Five dogs underwent endovascular repair, and six dogs had standard graft interpositions after an identical period of bacterial exposure. All grafts were removed at 2 weeks under sterile conditions and were submitted for quantitative culture analysis. RESULTS: Three of the six dogs (50%) with standard grafts appeared to clear their infections, whereas only one of the five dogs (20%) with an endovascular graft was free of organisms at 14 days. This results was further manifested by statistically significant lower postmortem colony counts in the standard grafts (p < 0.01). CONCLUSIONS: The endoluminal position of the graft and its proximity to the arterial wall do not appear to provide protection against infection. These data suggest that if endovascular grafts become infected, they may be in a disadvantaged position for host defense mechanisms to be effective.

Animals↗
PubMed1996

Staphylococcus aureus binding to human nasal mucin.

Colonization of human nasal mucosa with Staphylococcus aureus sets the stage for subsequent systemic infection. This study characterizes S. aureus adhesion to nasal mucosa in vitro and investigates the interaction of S. aureus with human nasal mucin. S. aureus binding to cell-associated and cell-free mucus was greater than to nonmucin-coated epithelial cells. Scanning electron microscopy of S. aureus incubated with human nasal mucosal tissue showed minimal binding to ciliated respiratory epithelium. In a solid-phase assay, S. aureus bound to purified human nasal mucin-coated wells significantly more than to bovine serum albumin-coated microtiter wells. Binding to mucin was saturable in a dose- and time-dependent fashion. Staphylococcal adherence to human nasal mucin was inhibited by bovine submaxillary mucin but not by fibrinogen. Pretreatment of mucin with periodate but not with pronase reduced adherence. Trypsin treatment of the bacteria significantly reduced adherence to mucin. 125I-labelled nasal mucin bound to two surface proteins (138 and 127 kDa) of lysostaphin-solubilized S. aureus. Binding to human nasal mucin occurs in part via specific adhesin-receptor interactions involving bacterial proteins and the carbohydrate moiety in mucin. These experiments suggest that S. aureus binding to mucin may be critical for colonization of the nasopharyngeal mucosa.

Bacterial Adhesion↗
PubMed1996

Interleukin-8 gene expression in Staphylococcus aureus-infected endothelial cells.

Interleukin-8 (IL-8) plays a crucial role in the migration of neutrophils to bacterium-infected sites. This study investigated IL-8 induction in Staphylococcus aureus-infected endothelial cells (EC). We observed that S. aureus-infected EC were induced to express both IL-8 mRNA and protein, which can promote transmigration of neutrophils across an EC monolayer.

Cells, Cultured↗
PubMed1995

Internalization of Staphylococcus aureus by endothelial cells induces cytokine gene expression.

The ability of the vascular endothelium to elaborate cytokines in response to gram-positive sepsis has received limited attention. This study examined cytokine expression by human umbilical vein endothelial cells (EC) following infection with a gram-positive bacterial pathogen, Staphylococcus aureus. S. aureus infection of EC resulted in the production of interleukin-6 (IL-6) and IL-1 beta. For IL-6, message was detected at 3 h after infection, protein was present at 24 h, and both message and protein persisted for 72 h. IL-1 beta message was detected at 12 h, IL-1 beta protein was detected at 24 h, and both persisted for 72 h. Message for colony-stimulating factor 1 remained unaltered. UV-killed S. aureus also elicited IL-1 beta and IL-6 message and protein expression at 24 and 48 h. Twenty-one clinical isolates of S. aureus were tested, and all induced IL-6 release by 48 h. However, the laboratory strain 8325-4 did not induce cytokine expression at any time point and was internalized by EC 1,000-fold less than other strains were. Internalization of latex beads by EC did not induce IL-6 gene expression. Furthermore, cytochalasin D treatment of the EC prevented IL-1 and IL-6 induction by S. aureus but not by tumor necrosis factor alpha or lipopolysaccharide. These results indicate that S. aureus is a potent inducer of IL-1 and IL-6 in EC and that internalization of S. aureus by EC is necessary for their cytokine expression. Thus, our data suggest that the vascular endothelium may play an important role in the pathogenesis of septicemia caused by gram-positive organisms.

Blotting, Northern↗
PubMed1995

Seronegative chronic relapsing neuroborreliosis.

We report an unusual patient with evidence of Borrelia burgdorferi infection who experienced repeated neurologic relapses despite aggressive antibiotic therapy. Each course of therapy was associated with a Jarisch-Herxheimer-like reaction. Although the patient never had detectable free antibodies to B. burgdorferi in serum or spinal fluid, the CSF was positive on multiple occasions for complexed anti-B. burgdorferi antibodies, B. burgdorferi nucleic acids and free antigen.

Anti-Bacterial Agents↗
PubMed1992

Persistent fever in association with infective endocarditis.

Fever persisting despite adequate antimicrobial therapy for endocarditis can be an ominous sign. To evaluate the significance of persistent fever in this situation, we reviewed the records of patients at three hospital affiliates of Albert Einstein College of Medicine. Twenty-six patients with 27 episodes of endocarditis and fever lasting for > or = 2 weeks despite appropriate antimicrobial therapy were identified and compared with a matched cohort of 26 patients with endocarditis but without prolonged fever. The median duration of fever in the former group was 35 days. Cardiac infection caused fever in 13 of these patients, seven of whom had myocardial abscesses. Additional causes of infection included drug treatment, nosocomial transmission of pathogens, and pulmonary emboli. Sixteen patients required cardiac surgery (seven on an emergent basis), whereas only two controls underwent such a procedure (P < .001). Twenty-two patients with persistent fever and five controls developed nosocomial complications (P < .001). Six patients with fever died, five from endocarditis-related complications. Thus persistent fever often indicates complicated endocarditis. We present an approach for the evaluation of the patients affected by this condition.

Adolescent↗
PubMed1992

Staphylococcus aureus proteins that bind to human endothelial cells.

The adherence of Staphylococcus aureus to human endothelial cells is saturable in both dose- and time-dependent assays. Staphylococcal surface components which bound to endothelial cells in vitro were identified by using biotin-labeled, solubilized staphylococcal proteins. Four trypsin-sensitive components with molecular sizes of 30, 55 to 57, 70, and 85 kDa were recognized. These proteins did not label with the glycan detection system. When staphylococci were harvested during the exponential phase of growth, staphylococcal adherence to endothelial cells was significantly increased and increased expression of the S. aureus binding proteins was observed. Preincubation of endothelial cells with protein A did not reduce S. aureus adherence in an in vitro infection assay. Four S. aureus surface components whose expression is growth phase dependent adhere to human endothelial cells in vitro.

Bacterial Adhesion↗