Jonathan R. Hibbs

Molecular Subtyping to Detect Human Listeriosis Clusters

We analyzed the diversity (Simpson’s Index, D) and distribution of Listeria monocytogenes in human listeriosis cases in New York State (excluding New York City) from November 1996 to June 2000 by using automated ribotyping and pulsed-field gel electrophoresis (PFGE). We applied a scan statistic (p<0.05) to detect listeriosis clusters caused by a specific Listeria monocytogenes subtype. Of 131 human isolates, 34 (D=0.923) ribotypes and 74 (D=0.975) PFGE types were found. Nine (31% of cases) clusters were identified by ribotype or PFGE; five (18% of cases) clusters were identified by using both methods. Two of the nine clusters (13% of cases) identified corresponded with investigated multistate listeriosis outbreaks. While most human listeriosis cases are considered sporadic, highly discriminatory molecular subtyping approaches thus indicated that 13% to 31% of cases reported in New York State may represent single-source clusters. Listeriosis control and reduction efforts should include broad-based subtyping of human isolates and consider that a large number of cases may represent outbreaks.

Prevalence of Human Immunodeficiency Virus Infection, Mortality Rate, and Serogroup Distribution Among Patients with Pneumococcal Bacteremia at Denver General Hospital, 1984–1994

Pandemics of human immunodeficiency virus (HIV) type 1 infection and penicillin resistance highlight the urgency of preventing invasive pneumococcal disease with vaccination. We characterized pneumococcal serogroup distribution and the mortality rate among 460 patients with pneumococcal bacteremia from 1984 through 1994 at Denver General Hospital and the prevalence of HIV infection in patients for whom pneumococcal bacteremia was diagnosed from 1989 to 1994. Vaccine-related serogroups accounted for 426 isolates (92.6%), including 48 (92.3%) of 52 isolates from HIV-infected patients. Mortality among patients 15 years of age or older was higher during 1984-1988 (18[12.9%] of 140) than during 1989-1994 (10 [5.2%] of 191: rate ratio, 2.5; 95% confidence interval, 1.2-5.2). Of patients 15-59 years of age from 1989 to 1994, 44 (39.6%) of 111 men and three (7.3%) of 41 women were HIV-infected. Four (8.5%) of 47 HIV-infected patients and four (3.8%) of 105 other patients in this group died (age-weighted rate ratio, 1.8; 95% confidence interval, 0.5-6.2). We recommend routine screening of young adults with pneumococcal bacteremia for HIV infection and immunization of HIV-infected patients with pneumococcal vaccine (which includes most serogroups of infecting strains).

Diagnosis and Outcome of 100 Consecutive Patients with Extreme Granulocytic Leukocytosis

PURPOSE To determine the clinical features, causes, and prognostic significance of extreme leukocytosis in adults. PATIENTS AND METHODS Medical records of 100 consecutive patients who presented at the Minneapolis Veterans Affairs Medical Center between March 1993 and January 1994 with more than 25,000 leukocytes/microL blood and with more than 50% granulocytes were reviewed. Demographic, clinical, and outcome information was recorded, and a cause of extreme leukocytosis was sought in each case. RESULTS Extreme leukocytosis was attributed to infection in 48 cases, advanced malignancy in 13 cases, hemorrhage in 9 cases, glucocorticoids in 8 cases, and other causes in 22 cases. Four patients had previously diagnosed conditions resulting in chronic leukocytosis. Higher leukocyte counts were associated with malignancy (chi2 for trend=12.5, P <0.002). Fever was more common in patients with infection (weighted rate ratio=3.7, 95% Confidence interval [CI]=2.2 to 6.2). Mortality was high overall (31%), and was greater in patients with noninfectious diagnoses compared with infected patients, an association which persisted after stratification by leukocyte count (weighted rate ratio=2.5, 95% CI=1.2 to 4.9). CONCLUSION Clinicians should be aware that extreme leukocytosis with a predominance of granulocytes is associated with infection in only 48% of cases. The presence of fever increases the likelihood that infection is the cause. Mortality is high, particularly in patients without infection.

Recurrent Listeria monocytogenes Infection: Relapse or Reinfection with a Unique Strain Confirmed by Molecular Subtyping

We report a case of recurrent listeriosis for which molecular subtyping by automated ribotyping and pulsed-field gel electrophoresis confirmed either relapse of infection or reinfection due to a common source almost 9 months after initial infection due to a unique Listeria monocytogenes strain in a patient with colorectal cancer. This case report illustrates the potential use of molecular subtyping to further understand the pathogenesis and epidemiology of listeriosis and the potential for relapse of Listeria infections in humans.

Levofloxacin Kills Chlamydia pneumoniae and Modulates Interleukin 6 Production by HEp-2 Cells

Background:Chlamydia pneumoniae is known to cause acute respiratory infection and more recently it has been studied as a pathogen causing inflammatory changes in chronic diseases such as atherosclerosis. This study addresses the antichlamydial effect of levofloxacin and its role in modulation of a proinflammatory cytokine IL-6 production by uninfected and infected HEp-2 cells. Methods: HEp-2 cell monolayers were infected with previously prepared and frozen aliquots of C. pneumoniae [1 × 103 inclusion-forming units (IFU)/ml] by centrifugation for 30 min and incubation at 37°C for 1 h. Infected monolayers were treated with levofloxacin (3 or 8 µg/ml) immediately after infection (0 h) or 24 h after infection. Monolayers were examined daily for 96 h after infection by counting inclusions with fluorescently labeled antichlamydial monoclonal antibody. Aliquots of disrupted monolayers were titrated to determine the numbers of viable C. pneumoniae IFU/ml. IL-6 concentrations in cell supernatants were determined by ELISA assays. Results: Infected HEp-2 cells produced IL–6. Noninfected HEp-2 cells demonstrated modulation of IL-6 production by levofloxacin. No viable C. pneumoniae were detected in infected HEp-2 cells when the monolayer was treated with levofloxacin immediately after infection (0 h). In contrast, when cells were treated 24 h after infection, a gradual decline in the number of viable C. pneumoniae occurred; by 96 h into the assay ≧98% of C. pneumoniae were killed. IL-6 concentrations were similar in the supernatants of levofloxacin-treated and nontreated HEp-2 cells. Conclusions: (1) Levofloxacin is effective in eliminating C. pneumoniae from infected HEp-2 cells; (2) although levofloxacin modulates the production of IL-6 in untreated HEp-2 cells, no evidence for such modulation was observed in HEp-2 cells infected with C. pneumoniae. (3) Presence of viable C. pneumoniae may not be necessary for IL-6 production by infected and treated HEp-2 cells.