Absence of gender differences in clinical outcomes in patients with cardiogenic shock complicating acute myocardial infarction. A report from the SHOCK Trial Registry.

OBJECTIVES: The aim of this study was to assess the impact of gender on clinical course and in-hospital mortality in patients with cardiogenic shock (CS) complicating acute myocardial infarction (AMI). BACKGROUND: Previous studies have demonstrated higher mortality for women compared with men with ST elevation myocardial infarctions and higher rates of CS after AMI. The influence of gender and its interaction with various treatment strategies on clinical outcomes once CS develops is unclear. METHODS: Using the SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK? (SHOCK) Registry database of 1,190 patients with suspected CS in the setting of AMI, we examined shock etiologies by gender. Among the 884 patients with predominant left ventricular (LV) failure, we compared the patient demographics, angiographic and hemodynamic findings, treatment approaches as well as the clinical outcomes of women versus men. This study had a 97% power to detect a 10% absolute difference in mortality by gender. RESULTS: Left ventricular failure was the most frequent cause of CS for both gender groups. Women in the SHOCK Registry had a significantly higher incidence of mechanical complications including ventricular septal rupture and acute severe mitral regurgitation. Among patients with predominant LV failure, women were, on average, 4.6 years older, had a higher incidence of hypertension, diabetes and a lower cardiac index. The overall mortality rate for the entire cohort was high (61%). After adjustment for differences in patient demographics and treatment approaches, there was no significant difference in in-hospital mortality between the two gender groups (odds ratio = 1.03, 95% confidence interval of 0.73 to 1.43, p = 0.88). Mortality was also similar for women and men who were selected for revascularization (44% vs. 38%, p = 0.244). CONCLUSIONS: Women with CS complicating AMI had more frequent adverse clinical characteristics and mechanical complications. Women derived the same benefit as men from revascularization, and gender was not independently associated with in-hospital mortality in the SHOCK Registry.

One-year survival following early revascularization for cardiogenic shock.

CONTEXT: Cardiogenic shock (CS) is the leading cause of death for patients hospitalized with acute myocardial infarction (AMI). OBJECTIVE: To assess the effect of early revascularization (ERV) on 1-year survival for patients with AMI complicated by CS. DESIGN: The SHOCK (Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock) Trial, an unblinded, randomized controlled trial from April 1993 through November 1998. SETTING: Thirty-six referral centers with angioplasty and cardiac surgery facilities. PATIENTS: Three hundred two patients with AMI and CS due to predominant left ventricular failure who met specified clinical and hemodynamic criteria. INTERVENTIONS: Patients were randomly assigned to an initial medical stabilization (IMS; n = 150) group, which included thrombolysis (63% of patients), intra-aortic balloon counterpulsation (86%), and subsequent revascularization (25%), or to an ERV group (n = 152), which mandated revascularization within 6 hours of randomization and included angioplasty (55%) and coronary artery bypass graft surgery (38%). MAIN OUTCOME MEASURES: All-cause mortality and functional status at 1 year, compared between the ERV and IMS groups. RESULTS: One-year survival was 46.7% for patients in the ERV group compared with 33.6% in the IMS group (absolute difference in survival, 13.2%; 95% confidence interval [CI], 2.2%-24.1%; P<.03; relative risk for death, 0.72; 95% CI, 0.54-0.95). Of the 10 prespecified subgroup analyses, only age (<75 vs >/= 75 years) interacted significantly (P<.03) with treatment in that treatment benefit was apparent only for patients younger than 75 years (51.6% survival in ERV group vs 33.3% in IMS group). Eighty-three percent of 1-year survivors (85% of ERV group and 80% of IMS group) were in New York Heart Association class I or II. CONCLUSIONS: For patients with AMI complicated by CS, ERV resulted in improved 1-year survival. We recommend rapid transfer of patients with AMI complicated by CS, particularly those younger than 75 years, to medical centers capable of providing early angiography and revascularization procedures.

Clinical and laboratory diagnosis of influenza virus infections.

Influenza epidemics account for more than 20,000 deaths in the United States each year, as well as substantial morbidity, medical costs, and time away from work and school. Since the 1950s, the principal weapon against these seasonal epidemics has been killed virus vaccine formulations. Despite massive efforts to immunize at-risk individuals against influenza, not everyone receives the vaccine. In addition, use of some drugs, such as amantadine and rimantadine, can lead to the development of drug resistant viruses in infected individuals and to transmission of these viruses to susceptible individuals. The many factors that contribute to the high annual incidence of influenza virus infections mandate prompt clinical recognition and appropriate patient management. Rapid diagnostic tests have been developed that may make it possible to avoid the use of antibacterial drugs, quickly decide whether isolation of infected patients is needed, and discharge hospitalized patients sooner.

Oral hairy leukoplakia: a manifestation of primary infection with Epstein-Barr virus?

Oral hairy leukoplakia (OHL) is a characteristic lesion presumably secondary to Epstein-Barr virus (EBV) reactivation. It is frequently seen in individuals infected with the human immunodeficiency virus (HIV) and less often in other immunosuppressed individuals. The frequent association of this lesion with HIV infection and its rare occurrence in normal individuals usually motivates the search for immunosuppression, particularly secondary to HIV, when this lesion is found. We describe here a healthy HIV-negative individual with OHL and clinical and laboratory data suggestive of acute EBV infection.

Clinical and economic impact of enterovirus illness in private pediatric practice.

OBJECTIVE: To characterize the acute clinical course and economic burden of nonpolio enteroviral (NPEV) illness in the summer/fall season as seen in private pediatric practice. METHODS: We prospectively studied 380 children aged 4 to 18 years with systemic NPEV syndromes presenting to private suburban pediatric practices. Seventy-three asymptomatic controls were concurrently enrolled. Clinical diagnosis of NPEV illness was based on the presence of fever plus at least one of the following: headache and stiff neck (n = 2); myalgia and malaise (n = 105); nonpuritic maculopapular rash (n = 10); papulovesicular stomatitis (n = 214); papular rash of the hands, feet, and mouth (H/F/M) (n = 30); or pleurodynia (n = 11). Study participants were enrolled during a 4-month time span (July-October, 1994) and followed daily for 14 days. A parent symptom diary card and twice weekly phone contacts by study nurses characterized the illness to include the frequency of health care contacts, the necessity for laboratory tests, medication use, and school/work absenteeism. RESULTS: Three hundred seventy-two (98%) children completed the study; 122 (33%) of the patients were confirmed to be infected with NPEV. Confirmed NPEV infection was more frequently observed in Rochester, NY (85/147 = 58%) than in Scottsdale, AZ (32/224 = 14%). The age group 4 to 12 years comprised 79% to 90% of the enrollees, depending on the syndrome. Median duration of illness and median number of missed days of school/summer camp/work for the enrolled patients was: meningitis (7 days ill, 2 days missed), myalgia/malaise (9 days ill, 3 days missed), rash (6 days ill, 4 days missed), stomatitis (7 days ill, 2 days missed), H/F/M (7 days ill, 1 day missed), and pleurodynia (8 days ill, 3 days missed). Direct medical costs varied from $69 per case to $771 per case and indirect costs, attributable primarily to parent missed work and/or sick-child care, varied from $63 per case to $422 per case for H/F/M and meningitis, respectively. In households, H/F/M spread to 50% of siblings and 25% of parents. CONCLUSIONS: In our study population, NPEV infection: 1) caused sufficient illness to prompt physician visits in summer and fall; 2) occurred more frequently in 4 to 12 year olds than in adolescents; 3) produced various clinical syndromes concurrently during the same months in the same season of a given year; 4) varied in occurrence geographically; 5) was characterized by numerous symptoms of longer duration than previously recognized; and 6) produced a significant economic impact by generating both direct and indirect costs.

Placental examination in intrauterine coinfection with herpes simplex virus and cytomegalovirus.

Intrauterine coinfections have rarely been reported. However, pregnancies exposed to multiple sexually transmitted infectious agents and drugs are likely to occur with increasing frequency and lead to complex pathology in the newborn. Often it will be difficult to establish a diagnosis, above all when this has to be done retrospectively. A premature (34 weeks) newborn presented with a complex clinical picture after exposure to multiple infectious and noninfectious teratogens during gestation. Immunocytochemical staining of the placental membranes and parenchyma suggested intrauterine coinfection by herpes simplex virus (HSV) type 2 and cytomegalovirus. This case illustrates the importance of careful placental investigation with modern techniques for the diagnosis of intrauterine HSV infection and coinfections.

Prognostic significance of nonfatal reinfarction during 3-year follow-up: results of the Thrombolysis in Myocardial Infarction (TIMI) phase II clinical trial. The TIMI Investigators.

OBJECTIVES: This study sought to assess the independent contribution of nonfatal reinfarction to the risk of subsequent death in patients with acute myocardial infarction undergoing thrombolytic therapy. BACKGROUND: A composite of "unsatisfactory outcomes" as an end point has increased statistical power and facilitated evaluation of evolving treatment regimens in acute myocardial infarction. The significance of nonfatal reinfarction as a component of a composite end point has not been evaluated in the thrombolytic era. METHODS: Event rate of nonfatal reinfarction over 3-year follow-up was evaluated in patients with acute myocardial infarction entered into the Thrombolysis in Myocardial Infarction Phase II trial. The independent risk of nonfatal reinfarction for subsequent death within various time intervals of follow-up was determined. The mortality rate after nonfatal reinfarction was compared with that of a matched control group. RESULTS: During 3-year follow-up, 349 of 3,339 patients had a nonfatal reinfarction. Univariate predictors were history (antedating the index event) of angina (p = 0.01), hypertension (p = 0.01), multivessel disease (p = 0.007) and not a current smoker (p = 0.003); the latter was an independent predictor (relative risk [RR] 1.3, 99% confidence interval [CI] 1.0 to 1.8). Forty-three of the 349 patients with a nonfatal reinfarction died: RR for death (vs. patients without a nonfatal reinfarction) was 1.9 (99% CI 1.1 to 3.2) if reinfarction occurred within 42 days of study entry, 6.2 (99% CI 3.0 to 12.9) if reinfarction occurred between 43 and 365 days and 2.9 (99% CI 0.6 to 13.4) if reinfarction occurred between 366 days and 3 years. The cumulative 3-year death rate was 14.1% in patients with a nonfatal reinfarction compared with 7.9% (p < 0.01) in a matched control group. Univariate predictors of death after nonfatal reinfarction were age > or = 65 years (p < 0.001), not low risk category (p = 0.015) and history of heart failure before the index event (p < 0.001). Age > or = 65 years was the only independent predictor (RR 5.4, 99% CI 2.3 to 12.4). CONCLUSIONS: Nonfatal reinfarction is a strong and independent predictor for subsequent death. It represents a powerful component for a composite end point in patients who received thrombolytic therapy after acute myocardial infarction.

Cytomegalovirus in the perfused human term placenta in vitro.

Cytomegalovirus (CMV) is one of the most frequent causes of intrauterine-acquired infection in the human species. However, very little is known about the pathophysiology of the transplacental transmission of the virus from the mother to the fetus. In this study, the passage of CMV across the human term placenta, and the susceptibility of the human term trophoblast to infection with CMV was investigated. In vitro dual perfusion of human term placental lobules was performed. In five experiments the perfused tissue was exposed to high titres (10(4)-10(6) 50 per cent tissue culture infective doses) of CMV AD169 for up to 9.5 h. Monitoring included placental functional parameters, and virus titres in the perfused tissue, and in the fetal and maternal circuit. Immunocytochemistry with a monoclonal antibody against CMV immediate early antigen was used to search for placental infection. CMV AD169 did not cross the placenta even during many hours of perfusion, up to 9.5 h, and with exposure to high virus titres. No infected placental cells were detected by immunocytochemistry, although the virus cultures from perfused tissue samples were positive. The perfused human term placenta and the term trophoblast in vitro form an effective barrier to cell-free CMV AD169.

Communitywide laboratory-based influenza surveillance focused on older persons, 1989-1992.

We collected surveillance data as part of the Medicare Influenza Vaccine Demonstration to describe communitywide epidemiology of influenza, focusing on the elderly. Laboratory-based surveillance was established in medical practices, hospitals, and nursing homes in a two-county demonstration in upstate New York. Time course and intensity of epidemic influenza were compared between counties, between influenza A and B epidemics, and among several levels of surveillance involving elderly persons as well as children during the years 1989-1992. The counties experienced parallel epidemics during each of the three demonstration years. Influenza A/H3N2, predominant in 1989-1990 and 1991-1992, was equally intense among young and old, accounted for 11%-28% of acute cardiopulmonary hospitalizations of older persons, and caused focal outbreaks in 30%-40% of nursing homes in the respective epidemics. Influenza B, predominant in 1990-1991, showed modest impact among the elderly as compared with children. Influenza A/H1N1 occurred among children each year but was virtually absent among the elderly. Systematic surveillance during the "influenza season" consistently confirms widespread infection among older patients, both in the community and in institutions. However, much febrile respiratory illness in this age group during periods of epidemic influenza is culture-negative for influenza virus and thus may be caused by other respiratory pathogens.

Dobutamine echocardiography and resting-redistribution thallium-201 scintigraphy predicts recovery of hibernating myocardium after coronary revascularization.

The value of dobutamine echocardiography and resting thallium-201 scintigraphy to predict reversal of regional left ventricular wall motion dysfunction after revascularization in patients with chronic coronary artery disease was assessed. Improvement in wall motion during dobutamine echocardiography and normal or mildly decreased uptake on thallium-201 scanning are strong predictors of reversible left ventricular dysfunction. Dobutamine echocardiography and resting thallium-201 scanning are simple and safe methods of assessing hibernating myocardium.

Ultrasound evaluation of the inferior epigastric artery.

Color-flow Doppler ultrasound was used to assess the anatomic characteristics of the inferior epigastric artery (IEA) bilaterally in 20 nonatherosclerotic (group I; mean age, 28 years) and 20 atherosclerotic (group II; mean age, 57 years) subjects. Forty-nine percent of the IEAs were located laterally within the rectus sheath with 34% in a mid and 17% in a medial location. Seventeen percent had a large branch within 5 cm of the origin. Average length of the IEA was 10.7 +/- 3.2 cm. Average proximal and distal internal diameters were 3.0 +/- 0.45 and 1.9 +/- 0.35 mm, respectively. Neither length nor vessel diameter showed any correlation with age or body surface area. Sixty-two percent of the IEAs were greater than or equal to 9 cm in length and 1.5 mm in distal diameter. Stenosis of the vessel (more than 50% diameter) was noted at the proximal 1 cm segment in 20% of the IEAs in the atherosclerotic group but none of the IEAs in the nonatherosclerotic group. Beyond this proximal segment, there was freedom from atherosclerotic stenosis as demonstrated by the IEAs' similarity of length and diameter irrespective of age in these atherosclerotic and nonatherosclerotic populations.

Should all patients undergoing cardiac catheterization or percutaneous transluminal coronary angioplasty receive oxygen?

BACKGROUND: Supplemental oxygen is routinely administered to patients with acute coronary syndromes. The risk of significant morbidity during cardiac catheterization or coronary angioplasty has been well described; however, to our knowledge, the need for routine oxygen supplementation in these patients has not been investigated. METHODS: In phase 1, we prospectively studied 142 patients undergoing diagnostic cardiac catheterization (n = 94) or percutaneous transluminal coronary angioplasty (PTCA) (n = 48) to determine the incidence of procedure-related hypoxemia (pulse oximetry derived oxygen saturation [SpO2] < 90 percent of > 1 min duration) while breathing room air (RA). In phase 2, 134 patients undergoing diagnostic cardiac catheterization (n = 78) or PTCA (n = 56) were randomly allocated to breathe either RA or supplemental oxygen (O2, 6 L/min by nasal cannula) to determine the effect of oxygen administration on procedure-related hypoxemia. Oximetry results were compared with pertinent clinical and procedural data that might predispose patients to develop hypoxemia. RESULTS: Phase 1--Moderate to severe hypoxemia occurred in 36 percent (34/94) of patients undergoing diagnostic catheterization and in 56 percent (27/48) of patients undergoing PTCA. In the diagnostic catheterization group, there were a total of 25 episodes of moderate hypoxemia (SpO2 85 to 89 percent) lasting 4.0 +/- 4.3 min and 11 episodes of severe hypoxemia (SpO2 < 85 percent) of greater duration, 11.7 +/- 7.5 min (p < 0.008). In the PTCA group, there were 24 episodes of moderate hypoxemia and six episodes of severe hypoxemia lasting 4.8 +/- 4.3 min and 8.2 +/- 3.8 min, respectively. A history of chronic lung disease was associated with hypoxemia (p < 0.05) in the diagnostic group. In addition, 11 patients undergoing diagnostic catheterization who had baseline SpO2 < 95 percent all developed hypoxemia during the procedure. In this subset of patients, there was a higher incidence of cigarette smoking (p = 0.02), chronic lung disease (p = 0.04), higher left ventricular diastolic pressure (p = 0.02), and lower ejection fraction (p = 0.002) when compared with the 83 remaining patients undergoing diagnostic catheterization with a baseline SpO2 > 95 percent. Phase 2--Oxygen therapy was associated with a reduction in the incidence of hypoxemia from 42 percent to 5 percent (RA vs O2, p < 0.001) in the diagnostic catheterization group and 39 percent to 11 percent (RA vs O2, p < 0.03) in the PTCA group. CONCLUSIONS: Significant hypoxemia is a common finding among patients undergoing cardiac catheterization or angioplasty despite the absence of predictive risk factors. Severe and prolonged hypoxemic episodes occurred in 10 percent (14/142, phase 1) of patients breathing room air. Patients undergoing diagnostic catheterization with history of chronic lung disease or a baseline SpO2 < 95 percent are at high risk to develop moderate-severe hypoxemia. Oxygen therapy significantly reduced the incidence and severity of procedure-induced hypoxemia in both groups. Our data support the use of both pulse oximetry and oxygen supplementation in patients undergoing cardiac catheterization and PTCA.

Spontaneous coronary dissection treated with directional coronary atherectomy.

We report a case of spontaneous coronary dissection occurring in a middle aged male which was treated with thrombolytic therapy and directional coronary atherectomy. This technique provides a new option for treating this entity in the cardiac catheterization laboratory.

Cytomegalovirus infection of the human placenta: an immunocytochemical study.

In congenital cytomegalovirus (CMV) infection histologic evaluation of the placenta is often unrevealing. In the present study immunocytochemistry to CMV immediate early and early nuclear antigens was used to characterize placental involvement in six cases of symptomatic intrauterine CMV infection. Histologic examination had demonstrated diagnostic viral inclusions in one placenta and non-specific villitis in another. However, immunocytochemistry revealed CMV infection in five of the six placentas, including three with no pathologic changes on routine histologic evaluation. Infected cells were located primarily in the villous stroma. In one case immunoperoxidase staining showed infection in the syncytiotrophoblast. Infected endothelial cells were demonstrated by double staining for CMV and factor VIII antigen. No double-stained cells were seen in tissue sections stained for CMV immediate early nuclear antigen or the human macrophage-associated CD68 antigen, which is expressed in Hofbauer cells. In conclusion, specific immunoperoxidase staining was more sensitive for demonstrating placental CMV infection than was histologic examination and it aided in the characterization of infected cells.

Magnetic resonance imaging of suspected atrial tumors.

Two-dimensional echocardiography has become the standard technique for evaluation of cardiac and paracardiac mass lesions. We have used magnetic resonance imaging (MRI) as an independent assessment of cardiac-associated masses in patients with echocardiograms demonstrating sessile atrial tumors. MRI was performed in seven patients, ages 33 to 84, whose echocardiographic diagnoses included left atrial mass (five), right atrial mass (one), and interatrial mass (one). In four of the patients with a diagnosis of left atrial mass, MRI showed extracardiac compression of the atrium, simulating a tumor (hiatal hernia, tortuous descending aorta, bronchogenic cyst). MRI was entirely normal in one patient with an apparent left atrial mass. MRI elucidated extension of an extracavitary mass into the interatrial septum in two patients. One of these patients with an echocardiographic right atrial mass had extension of a lipoma into the interatrial septum without atrial tumor. MRI confirmed the echocardiographic diagnosis of an interatrial mass in the other patient. We conclude that MRI, because of its ability to define anatomic relationships and tissue characteristics, is a powerful noninvasive tool for evaluating suspected cardiac mass lesions. Although echocardiography remains the primary screening test for the detection of cardiac masses, MRI is a more specific modality for precise diagnosis. Correct MRI interpretation may obviate the need for invasive studies or surgery.

Characterization of an 18,000-molecular-weight outer membrane protein of Haemophilus ducreyi that contains a conserved surface-exposed epitope.

Identification of antigenically conserved surface components of Haemophilus ducreyi may facilitate the development of reagents to diagnose and prevent chancroid. A hybridoma derived from a mouse immunized with nontypeable Haemophilus influenzae produced a monoclonal antibody (MAb), designated 3B9, that bound to 35 of 35 H. ducreyi strains isolated from diverse geographic regions. The MAb 3B9 bound to a non-heat-modifiable H. ducreyi outer membrane protein (OMP) whose apparent molecular weight was 18,000 (the 18K OMP), and the 3B9 epitope did not phase vary at a rate of greater than 10(-3) in H. ducreyi. In immunoelectron microscopy, the 3B9 epitope was surface exposed, and there was intrastrain and interstrain variability in the amount of 3B9 labelling of whole cells. The MAb 3B9 cross-reacted with many species of the family Pasteurellaceae and bound to the 16.6K peptidoglycan-associated lipoprotein (P6 or PAL) of H. influenzae. Unlike P6, the 18K OMP did not copurify with peptidoglycan. In Western blots (immunoblots), five of seven serum samples obtained from patients with chancroid and four of five serum samples obtained from patients with other genital ulcer diseases at the time of presentation contained antibodies that bound to the 18K OMP. In a competition enzyme-linked immunosorbent assay, four of these serum samples inhibited the binding of 3B9 to H. ducreyi by more than 50%. We conclude that members of Pasteurellaceae expressed a conserved epitope on OMPs that sometimes had different physical characteristics. Patients with chancroid usually have antibodies to the 18K OMP and the 3B9 epitope that may have resulted from infection with H. ducreyi or previous exposure to other Haemophilus or Actinobacillus sp. strains.

Microfibrillar cardiomyopathy: An infiltrative heart disease resembling but distinct from cardiac amyloidosis.

Microfibrils-small, ubiquitous components of the extracellular matrix in many tissues-generally have not been recognized as causing infiltrative heart disease, except in a group of cardiac transplant patients treated with cyclosporin. Microfibrils are often associated with elastic tissue and contain the glycoprotein fibrillin, the P component of amyloid, and bound fibronectin. A genetically determined abnormality of fibrillin caused by point mutations of fibrillin genes recently was reported as the cause of Marfan's syndrome. However, to date, no abnormalities of increased fibrillin tissue deposition have been observed. In the last two years, while examining right ventricular endomyocardial biopsies, in four patients we noted abnormal histology distinct from the usual type of congestive cardiomyopathy but with a strong resemblance to amyloidosis. The patients presented with unexplained ventricular tachycardia (N = 3) and/or congestive heart failure (N = 2). Biopsies revealed subendocardial, interstitial, and perivascular hyaline eosinophilic fibrillar material that did not stain with Congo red. Electron microscopy revealed that this material was organized into bundles of tangled microfibrils composed of twisted and tubular structures measuring up to 17 nm wide, which did not resemble amyloid or cyclosporin-associated microfibrils. Immunoelectron microscopy of the index case, using monoclonal antibody to fibrillin, specifically identified these structures as fibrillin microfibrils; fibronectin also was bound to the interstitial microfibrils. We believe that the subendocardial and interstitial deposition of microfibrils in these four symptomatic patients may represent a new type of infiltrative cardiomyopathy, similar to but distinct from cardiac amyloidosis. We do not know yet if this disorder is genetic or acquired, or if the prognosis is better than that of cardiac amyloidosis. However, atypical cases of primary cardiac amyloidosis should be reevaluated in light of these findings.

Use of multiple markers for investigation of an epidemic of Shigella sonnei infections in Monroe County, New York.

Antibiotic susceptibility patterns, plasmid profiles, and endonuclease restriction analysis of plasmid DNA were used in the investigation of an epidemic of Shigella sonnei infections in Monroe County, New York, in 1988 and 1989. The epidemic peaked during the winter, included the simultaneous transmission of the disease from person to person and from common food sources, and especially affected inhabitants of the poor, inner-city neighborhoods, young children of both sexes, and women. Resistance to ampicillin, tetracycline, or trimethoprim-sulfamethoxazole, encoded in a 70-MDa plasmid, was found in most of the examined isolates. Unexpectedly, isolates from patients involved in a food-borne outbreak exhibited three different antibiotic susceptibility patterns, suggesting deletion of antibiotic resistance determinants in some strains. Antibiograms clearly separated food-borne outbreak-related and non-foodborne outbreak-related strains, distinguished more strains than did the plasmid profiles, and were useful in tracing the dissemination of individual isolates in the community. Restriction endonuclease analysis substantially increased the discriminatory value of plasmid profiles and validated the antibiogram results. The present study illustrates the complexity of epidemics of S. sonnei infections and shows the value of combining different biological markers in the investigation.