Norovirus Epidemiology and Duration of Shedding in Michigan, 2007-2008

Background: In the United States, an estimated 23 million cases of norovirus (NoV) are reported each year, and although mortality is low, the morbidity and economic impact are substantial. Methods: RT-PCR and sequencing were used for identification of NoV genotypes obtained from outbreak and sporadic cases. RT Quant PCR was used to determine the viral load in fecal specimens. In order to rule out bacterial infection as the cause for acute gastroenteritis (AGE), bacterial culture for Salmonella, E.coli O157, Shigella, Campylobacter and Clostridium difficile was performed by standard laboratory procedures. The duration of NV shedding was investigated with longitudinal sampling in the sporadic cases and an evaluation of the association between viral load and days since clinical onset in the outbreak-associated cases. Results: We describe the epidemiology and strain identification for NoV circulating in Michigan during 2007-8 in concurrent sporadic and outbreak-associated cases. In 2007- 8, 138 norovirus outbreaks (3,437 cases) were reported to the MDCH. Among the 47 outbreak specimens sequenced, GI was identified in 14 (29.8%) and GII in 33 (70.2%). The predominant type was GII.4, found in 23 of the 33 (69.6%) GII specimens. The statistical analysis of outbreak-associated cases showed that neither NoV type nor number of days post-onset were associated with NoV log concentration. Among the sporadic cases, the repeated measures analysis of variance showed that NoV type (I or II) was not associated with log titer (P = 0.90), but that the number of weeks post-onset was statistically associated with declining log titer at p = 0.0005. Conclusion: We found no predominant strain difference between concurrent sporadic and outbreak-associated cases. Prevalent strains of NoV were shed in high concentration for at least two weeks past disease onset, suggesting that current public health recommendations for 2-3 days home isolation following clinical recovery may need to be lengthened

Association of Group B Streptococcus Colonization and Bovine Exposure: A Prospective Cross-Sectional Cohort Study

While Group B Streptococcus (GBS) human colonization and infection has long been suspected as originating from cows, several investigators have suggested that ongoing interspecies GBS transmission is unlikely due to genotyping data demonstrating that human and bovine-derived GBS strains represent mostly distinct populations. The possibility of ongoing transmission between humans and their livestock has not been systematically examined.To examine ongoing interspecies transmission, we conducted a prospective cross-sectional cohort study of 68 families and their livestock. Stool specimens were collected from 154 people and 115 livestock; GBS was detected in 19 (12.3%) humans and 2 (1.7%) animals (bovine and sheep). Application of multilocus sequence typing (MLST) identified 8 sequence types (STs or clones), with STs 1 and 23 predominating. There were 11 families in which two members submitted stools and at least one had GBS colonization. In 3 of these families, both members (consisting of couples) were colonized, yielding a co-colonization rate of 27% (95% CI: 7%-61%). Two of these couples had strains with identical MLST, capsule (cps) genotype, susceptibility, and RAPD profiles. One couple co-colonized with ST-1 (cps5) strains also had a bovine colonized with the identical strain type. On multivariate analysis of questionnaire data, cattle exposure was a predictor of GBS colonization, with each unit increase in days of cattle exposure increasing the odds of colonization by 20% (P = 0.02). These results support interspecies transmission with additional evidence for transmission provided by the epidemiological association with cattle exposure.Although GBS uncommonly colonizes livestock stools, increased frequency of cattle exposure was significantly associated with human colonization and one couple shared the same GBS strains as their bovine suggesting intraspecies transmission. These results set the framework for GBS as a possible zoonotic infection, which has significant public health implications

Drug-resistant Neisseria gonorrhoeae in Michigan

The increasing prevalence of quinolone-resistant Neisseria gonorrhoeae (QRNG) in the United States is a cause for concern. Detecting resistance is complicated by the widespread use of molecular tests that do not provide isolates for susceptibility testing. The Michigan Department of Community Health developed a sentinel surveillance program to detect antimicrobial drug resistance in N. gonorrhoeae. Sentinel surveillance from 11 laboratories submitted 1,122 isolates for antimicrobial drug susceptibility testing and detected 2 clusters of QRNG from January 2003 to September 2004. These clusters were epidemiologically distinct: one involved young, heterosexual youth, and the other involved older men who have sex with men. This finding led to changes in local treatment recommendations that limited spread of resistant strains. Development of the sentinel program, collection of data, and epidemiologic analysis of the clusters are discussed

Urinary tract infections in the catheterized elderly: Change in bacteriurial flora as a risk factor.

Indicators of acute urinary tract infection (UTI) in the catheterized elderly are few: patients often cannot communicate symptoms and may fail to show a fever; polymicrobial colonizing flora and WBCs are nearly universal with the presence of a catheter, complicating laboratory diagnosis. A prospective study was undertaken to increase understanding of the dynamics of acute UTI and to explore the hypothesis that change in bacteriurial flora contributes to acute UTI in this population. For this study, acute UTI was defined as a culture positive with at least one organism at concentrations of greater than 1,000 org/ml, and significant change in the character of the urine (e.g., hematuria) or diagnosis by a physician or fever of equal to or greater than 38\sp\circC unrelated to other causes. Weekly urine samples were obtained for six months from 13 chronically catheterized elderly and cultured to demonstrate all organisms in counts greater than 1,000 organisms/ml. Occurrence of a new organism in culture one week before or the same week as acute UTI was weakly but not significantly statistically associated with acute UTI (RR = 1.5 (95%CI 0.60 to 3.71)). Presence of crystals in urine was strongly associated with an increased risk of death the same week (RR = 47.4 (95% CI 4.86 to 462.89)). Recovery of Proteus mirabilis from urine culture was also strongly associated with risk of death the same week (RR = 26.3 (95% CI 1.79 to 43.98)). Hematuria functioned well in this sample as an indicator of acute UTI but needs to be confirmed in further controlled studies. The role of new organisms in the development of acute UTI, especially those organisms known to have an established potential for pathogenicity in the urinary tract such as Escherichia coli and Staphylococcus aureus, deserves further study. The strong association between death and the recovery of Proteus mirabilis suggests this agent has a high pathogenic potential unique to the urinary tract of the chronically catheterized, possibly due to urease-induced crystal formation. Proteus-dependent and patient-dependent variables in the formation of catheter-obstructing crystals requires further study.Dr.P.H.Hospital and Molecular EpidemiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104066/1/9431755.pdfDescription of 9431755.pdf : Restricted to UM users only

Surveillance for Shiga Toxin–producing Escherichia coli, Michigan, 2001–2005

A surveillance system used different detection methods to estimate prevalence of Shiga toxin–producing Escherichia coli during 2003–2005 and 2001–2002. More non-O157 serotypes were detected by enzyme immunoassay than by evaluation of non-sorbitol–fermenting E. coli isolates. We therefore recommend use of enzyme immunoassay and culture-based methods