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Volume 12, Number 8—August 2006

Volume 12, Number 8—August 2006   PDF Version [PDF - 5.37 MB - 131 pages]

Synopses

  • Invasive Enterobacter sakazakii Disease in Infants PDF Version [PDF - 87 KB - 5 pages]
    A. Bowen and C. R. Braden
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    Enterobacter sakazakii kills 40%–80% of infected infants and has been associated with powdered formula. We analyzed 46 cases of invasive infant E. sakazakii infection to define risk factors and guide prevention and treatment. Twelve infants had bacteremia, 33 had meningitis, and 1 had a urinary tract infection. Compared with infants with isolated bacteremia, infants with meningitis had greater birthweight (2,454 g vs. 850 g, p = 0.002) and gestational age (37 weeks vs. 27.8 weeks, p = 0.02), and infection developed at a younger age (6 days vs. 35 days, p<0.001). Among meningitis patients, 11 (33%) had seizures, 7 (21%) had brain abscess, and 14 (42%) died. Twenty-four (92%) of 26 infants with feeding patterns specified were fed powdered formula. Formula samples associated with 15 (68%) of 22 cases yielded E. sakazakii; in 13 cases, clinical and formula strains were indistinguishable. Further clarification of clinical risk factors and improved powdered formula safety is needed.

Research

  • Venezuelan Equine Encephalitis Virus Transmission and Effect on Pathogenesis PDF Version [PDF - 233 KB - 7 pages]
    D. R. Smith et al.
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    Quantifying the dose of an arbovirus transmitted by mosquitoes is essential for designing pathogenesis studies simulating natural infection of vertebrates. Titration of saliva collected in vitro from infected mosquitoes may not accurately estimate titers transmitted during blood feeding, and infection by needle injection may affect vertebrate pathogenesis. We compared the amount of Venezuelan equine encephalitis virus collected from the saliva of Aedes taeniorhynchus to the amount injected into a mouse during blood feeding. Less virus was transmitted by mosquitoes in vivo (geometric mean 11 PFU) than was found for comparable times of salivation in vitro (mean saliva titer 74 PFU). We also observed slightly lower early and late viremia titers in mice that were needle injected with 8 PFU, which represents the low end of the in vivo transmission range. No differences in survival were detected, regardless of the dose or infection route.

  • Bat-transmitted Human Rabies Outbreaks, Brazilian Amazon
    E. da Rosa et al.
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    We describe 2 bat-transmitted outbreaks in remote, rural areas of Portel and Viseu Municipalities, Pará State, northern Brazil. Central nervous system specimens were taken after patients' deaths and underwent immunofluorescent assay and histopathologic examination for rabies antigens; also, specimens were injected intracerebrally into suckling mice in an attempt to isolate the virus. Strains obtained were antigenically and genetically characterized. Twenty-one persons died due to paralytic rabies in the 2 municipalities. Ten rabies virus strains were isolated from human specimens; 2 other cases were diagnosed by histopathologic examination. Isolates were antigenically characterized as Desmodus rotundus variant 3 (AgV3). DNA sequencing of 6 strains showed that they were genetically close to D. rotundus–related strains isolated in Brazil. The genetic results were similar to those obtained by using monoclonal antibodies and support the conclusion that the isolates studied belong to the same rabies cycle, the virus variants found in the vampire bat D. rotundus.

  • Streptococcus suis Sequence Type 7 Outbreak, Sichuan, China PDF Version [PDF - 192 KB - 6 pages]
    C. Ye et al.
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    An outbreak of Streptococcus suis serotype 2 emerged in the summer of 2005 in Sichuan Province, and sporadic infections occurred in 4 additional provinces of China. In total, 99 S. suis strains were isolated and analyzed in this study: 88 isolates from human patients and 11 from diseased pigs. We defined 98 of 99 isolates as pulse type I by using pulsed-field gel electrophoresis analysis of SmaI-digested chromosomal DNA. Furthermore, multilocus sequence typing classified 97 of 98 members of the pulse type I in the same sequence type (ST), ST-7. Isolates of ST-7 were more toxic to peripheral blood mononuclear cells than ST-1 strains. S. suis ST-7, the causative agent, was a single-locus variant of ST-1 with increased virulence. These findings strongly suggest that ST-7 is an emerging, highly virulent S. suis clone that caused the largest S. suis outbreak ever described.

  • Carbapenem Resistance in Klebsiella pneumoniae Not Detected by Automated Susceptibility Testing PDF Version [PDF - 105 KB - 5 pages]
    F. C. Tenover et al.
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    Detecting β-lactamase–mediated carbapenem resistance among Klebsiella pneumoniae isolates and other Enterobacteriaceae is an emerging problem. In this study, 15 blaKPC-positive Klebsiella pneumoniae that showed discrepant results for imipenem and meropenem from 4 New York City hospitals were characterized by isoelectric focusing; broth microdilution (BMD); disk diffusion (DD); and MicroScan, Phoenix, Sensititre, VITEK, and VITEK 2 automated systems. All 15 isolates were either intermediate or resistant to imipenem and meropenem by BMD; 1 was susceptible to imipenem by DD. MicroScan and Phoenix reported 1 (6.7%) and 2 (13.3%) isolates, respectively, as imipenem susceptible. VITEK and VITEK 2 reported 10 (67%) and 5 (33%) isolates, respectively, as imipenem susceptible. By Sensititre, 13 (87%) isolates were susceptible to imipenem, and 12 (80%) were susceptible to meropenem. The VITEK 2 Advanced Expert System changed 2 imipenem MIC results from >16 μg/mL to <2 μg/mL but kept the interpretation as resistant. The recognition of carbapenem-resistant K. pneumoniae continues to challenge automated susceptibility systems.

  • VEB-1 Extended-Spectrum β-lactamase–producing Acinetobacter baumannii, France PDF Version [PDF - 394 KB - 9 pages]
    T. Naas et al.
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    VEB-1 extended-spectrum β-lactamase–producing Acinetobacter baumannii was responsible for an outbreak in hospitals in France. A national alert was triggered in September 2003 when 4 hospitals reported clusters of A. baumannii infection with similar susceptibility profiles. Case definitions and laboratory guidelines were disseminated, and prospective surveillance was implemented; strains were sent to a single laboratory for characterization and typing. From April 2003 through June 2004, 53 hospitals reported 290 cases of A. baumannii infection or colonization; 275 isolates were blaVEB-1-positive and clonally related. Cases were first reported in 5 districts of northern France, then in 10 other districts in 4 regions. Within a region, interhospital spread was associated with patient transfer. In northern France, investigation and control measures led to a reduction of reported cases after January 2004. The national alert enabled early control of new clusters, demonstrating the usefulness of early warning about antimicrobial drug resistance.

  • Macrolide Resistance in Adults with Bacteremic Pneumococcal Pneumonia PDF Version [PDF - 177 KB - 8 pages]
    J. P. Metlay et al.
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    We conducted a case-control study of adults with bacteremic pneumococcal pneumonia to identify factors associated with macrolide resistance. Study participants were identified through population-based surveillance in a 5-county region surrounding Philadelphia. Forty-three hospitals contributed 444 patients, who were interviewed by telephone regarding potential risk factors. In multivariable analyses, prior exposure to a macrolide antimicrobial agent (odds ratio [OR] 2.8), prior flu vaccination (OR 2.0), and Hispanic ethnicity (OR 4.1) were independently associated with an increased probability of macrolide resistance, and a history of stroke was independently associated with a decreased probability of macrolide resistance (OR 0.2). Fifty-five percent of patients with macrolide-resistant infections reported no antimicrobial drug exposure in the preceding 6 months. Among patients who reported taking antimicrobial agents in the 6 months preceding infection, failure to complete the course of prescribed drugs was associated with an increased probability of macrolide resistance (OR 3.4).

  • Antibody Response to Pneumocystis jirovecii PDF Version [PDF - 228 KB - 8 pages]
    K. R. Daly et al.
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    We conducted a prospective pilot study of the serologic responses to overlapping recombinant fragments of the Pneumocystis jirovecii major surface glycoprotein (Msg) in HIV-infected patients with pneumonia due to P. jirovecii and other causes. Similar baseline geometric mean antibody levels to the fragments measured by an ELISA were found in both groups. Serum antibodies to MsgC in P. jirovecii patients rose to a peak level 3–4 weeks (p<0.001) after recovery from pneumocystosis; baseline CD4+ count >50 cells/μL and first episode of pneumocystosis were the principal host factors associated with this rise (both p<0.001). Thus, MsgC shows promise as a serologic reagent and should be tested further in clinical and epidemiologic studies.

Policy Review

  • Virulent Epidemics and Scope of Healthcare Workers' Duty of Care PDF Version [PDF - 132 KB - 4 pages]
    D. K. Sokol
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    The phrase "duty of care" is, at best, too vague and, at worst, ethically dangerous. The nature and scope of the duty need to be determined, and conflicting duties must be recognized and acknowledged. Duty of care is neither fixed nor absolute but heavily dependent on context. The normal risk level of the working environment, the healthcare worker's specialty, the likely harm and benefits of treatment, and the competing obligations deriving from the worker's multiple roles will all influence the limits of the duty of care. As experts anticipate the arrival of an avian influenza pandemic in humans, discussion of this matter is urgently needed.

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