Duration of Group A Streptococcus PCR positivity following antibiotic treatment of pharyngitis.

BACKGROUND: Polymerase chain reaction (PCR) has high sensitivity and specificity for detection of group A streptococcus (GAS) in throat swabs and is routinely used for GAS pharyngitis diagnosis at our institution. Herein we defined the natural history of throat swab GAS PCR and culture positivity during and following treatment of GAS pharyngitis. METHODS: Fifty children with a PCR positive GAS throat swab were recruited for participation. Four additional throat swabs were collected over 2 weeks following the initial positive PCR result (during and following a standard course of antibiotic therapy) and tested for GAS using rapid real-time PCR and culture. RESULTS: After the initial positive swab, 45% had a positive PCR 2-4 days, 20% 5-7 days, 18% 8-10 days, 25% 11-13days, and 20% 14-18days later. The median time to a negative PCR was 4 days with the nadir in positive PCR results approximating the end of a typical 10-day treatment interval. Seven subjects remained persistently PCR positive. Culture results remained positive at a stable rate for each time interval, ranging from 5-10%. CONCLUSIONS: If a patient presents with symptoms of GAS pharyngitis after previous positive GAS PCR testing and treatment with appropriate antibiotics, it is reasonable to use PCR testing for GAS pharyngitis testing beginning one week after initial testing. Further studies are warranted to determine if this time frame can be applied to PCR testing used to detect other infections.

Clinical significance and antimicrobial susceptibilities of Aerococcus sanguinicola and Aerococcus urinae.

A retrospective chart review was performed on 92 patients from whom 118 isolates of Aerococcus sanguinicola (n = 52) or Aerococcus urinae (n = 66) were obtained from urine cultures between October 2007 and June 2008 to assess clinical presentation and antimicrobial susceptibilities. The mean patient age was 82 (range 24-101) years. The majority was female (76% and 87% for A. sanguinicola and A. urinae, respectively) and institutionalized (61% and 60%, respectively). The majority of male patients had underlying prostatic disease (55% and 63%, respectively). Thirty-one of 46 patients with A. sanguinicola and 45 of 57 patients with A. urinae isolated from the urine had a clinical diagnosis of urinary tract infection. One subject had A. sanguinicola isolated from blood cultures. A. sanguinicola and A. urinae had low ceftriaxone, penicillin, and vancomycin MICs. MICs to erythromycin and levofloxacin were ≥0.5 and >4 µg/mL in 41% and 78% of A. sanguinicola and 17% and 23% of A. urinae isolates, respectively. In conclusion, A. sanguinicola and A. urinae are not infrequent causes of urinary tract infection and most A. sanguinicola isolates have elevated MICs to levofloxacin.

Three-hour molecular detection of Campylobacter, Salmonella, Yersinia, and Shigella species in feces with accuracy as high as that of culture.

Campylobacter jejuni and Salmonella, Shigella, and Yersinia species (along with Shiga toxin-producing Escherichia coli) are the most common causes of acute bacterial diarrheal disease in the United States. Current detection techniques are time-consuming, limiting usefulness for patient care. We developed and validated a panel of rapid PCR assays for the detection and identification of C. jejuni, C. coli, Salmonella, and Yersinia species and Shigella and enteroinvasive E. coli in stool samples. A total of 392 archived stool specimens, previously cultured for enteric pathogens, were evaluated by PCR. Overall, 104 stool specimens had been culture positive (C. jejuni/coli [n = 51], Salmonella species [n = 42], Shigella species [n = 6], and Yersinia species [n = 5]). Compared to culture, the overall sensitivity and specificity of PCR detection of these organisms were 92 and 98% (96/104 and 283/288), respectively, from fresh or Cary Blair stool (P = 0.41); 87 and 98% (41/47 and 242/246), respectively, from fresh stool (P = 0.53); and 96 and 98% (55/57 and 41/42), respectively, from Cary Blair stool (P = 0.56). For individual genera, PCR was as sensitive as the culture method, with the exception of Salmonella culture using selenite enrichment for which PCR was less sensitive than culture from fresh, but not Cary Blair (P = 0.03 and 1.00, respectively) stools. This PCR assay panel for the rapid diagnosis of acute infectious bacterial diarrheal pathogens has a sensitivity and specificity equivalent to that of culture for stools in Cary Blair transport medium. Paired with reflexive culture of stools testing positive, this should provide an improvement in care for patients with acute infectious diarrheal disease.

High prevalence of tcdC deletion-carrying Clostridium difficile and lack of association with disease severity.

We assessed the prevalence of tcdC deletion-carrying Clostridium difficile using a stool polymerase chain reaction (PCR) assay that detects previously described 18- and 39-bp deletions (J. Clin. Microbiol. 2008;46:1996). We divided inpatients into 2 groups, those for whom the assay detected a deletion in tcdC and those for whom no deletion was detected. We compared risk factors (antibiotic use, hospitalization, nursing home stay, immunocompromise, age >65 years), complications (pseudomembranous colitis, toxic megacolon, colonic perforation, colectomy, and intensive care unit admission), duration of antibiotic treatment, and 30-day mortality between the groups. Forty-two of 141 patients had deletion-positive C. difficile. Prior nursing home stay and age >65 years were significantly more common in the deletion-positive group. Other risk factors, complications, antibiotic duration, and mortality did not differ significantly. Deletion-carrying C. difficile was commonly present but not associated with more severe disease and not markedly different in terms of risk factor profile. Severity of disease was relatively low, regardless of the presence or absence of a deletion.

Incidence of invasive pneumococcal disease among children after introduction of a 7-valent pneumococcal conjugate vaccine: a population-based study in Olmsted County, Minnesota.

OBJECTIVE: To examine the effect of the 7-valent pneumococcal conjugate vaccine in a well-characterized population in Olmsted County, Minnesota, with a combination of urban and rural residents likely to have a relatively low risk of invasive pneumococcal disease (IPD). PATIENTS AND METHODS: This population-based study analyzed data from children younger than 5 years to determine the incidence of IPD from January 1, 1995, to December 31, 2007. RESULTS: From 1995 through 2007, 29 cases of IPD were identified in the study population, but 2 patients denied research authorization; thus, 27 cases were available for review. From 1995-1999 to 2001-2003, the incidence of IPD decreased from 33.5 (95% confidence interval [CI], 16.6-50.5) to 10.8 (95% CI, 0.0-23.0) cases per 100,000 person-years (68% decrease; P=.046). The incidence subsequently increased to 15.2 (95% CI, 3.0-27.4) cases per 100,000 person-years from 2004 through 2007; however this change was not significant (P=.62). All cases of IPD with available serotype data from 2002 through 2007 (n=5) were due to non-7-valent conjugate vaccine serotypes. CONCLUSION: Although the baseline incidence of IPD was much lower than that reported in other populations, the overall incidence of IPD decreased significantly in children younger than 5 years after introduction of a 7-valent conjugate vaccine.

Trends in invasive pneumococcal disease among older adults in Olmsted County, Minnesota.

OBJECTIVE: Following the introduction of a 7-valent pneumococcal conjugate vaccine (PCV-7) for children in early 2000 in the United States, a decrease in the incidence of invasive pneumococcal disease (IPD) was seen in adults, likely due to a herd effect. However, there have been recent increases in IPD in adults caused by Streptococcus pneumoniae serotypes not included in PCV-7, so called "replacement disease". We performed a population-based study to further investigate this emerging concern. METHODS: Population-based incidence study in Olmsted County, Minnesota, United States, in adults aged > or =50 years. RESULTS: From 1/1/1995 to 12/31/2007, 104 cases of IPD were identified in Olmsted County in adults aged > or =50 years. We found a 45% increase in the incidence rate of IPD from 2001-2003 (17.7 cases per 100,000 person-years) to 2004-2007 (32.1 cases per 100,000 person-years) (p=0.029). From 2002-2004 to 2005-2007, the incidence rate of IPD caused by S. pneumoniae serotypes not included in PCV-7 increased from 9.2 to 32.8 cases per 100,000 person-years (p<0.001). CONCLUSION: A recent increase in the incidence of IPD in adults aged > or =50 years was demonstrated in Olmsted County, Minnesota due to serotypes not found in PCV-7. These findings are unique and merit further investigation.

Decreases in case-fatality and mortality rates for invasive pneumococcal disease in Olmsted County, Minnesota, during 1995-2007: a population-based study.

BACKGROUND: Following the introduction of a 7-valent pneumococcal conjugate vaccine for children in 2000, there has been a decrease in the incidence of invasive pneumococcal disease among both children and adults in the United States. We evaluated the hypothesis that the case-fatality and mortality rates for invasive pneumococcal disease have also decreased since 2000. METHODS: We conducted a population-based outcome study in Olmsted County, Minnesota, during the period 1995-2007 that involved patients of all ages. RESULTS: From 1 January 1995 through 31 December 2007, a total of 180 eligible cases of invasive pneumococcal disease were identified in Olmsted County. During the 13-year study period, the overall case-fatality rate for invasive pneumococcal disease decreased from 19% (14 of 74 cases) in 1995-1999 to 5% (5 of 91 cases) in 2001-2007, an 83% decrease, after adjustment for age, sex, and Charlson comorbidity index score (P =.003). The largest decreases in case-fatality rate were seen among adults aged >/=65 years (an 86% decrease, from 31% [9 of 29 cases] to 8% [3 of 40 cases]; P=.02) and patients with invasive pneumonia (a 78% decrease, from 22% [12 of 55 cases] to 7% [5 of 72 cases]; P=.01). The overall mortality rate for invasive pneumococcal disease decreased from 2.9 deaths per 100,000 person-years in 1995-1999 to 0.7 deaths per 100,000 person-years in 2001-2007, a 78% decrease, after adjustment for age and sex in a Poisson regression model (P=.002). CONCLUSIONS: Significant decreases in the case-fatality and mortality rates for invasive pneumococcal disease were demonstrated in the population of Olmsted County. Additional studies are needed to confirm our findings in other populations.

Nonutility of repeat laboratory testing for detection of Clostridium difficile by use of PCR or enzyme immunoassay.

The diagnostic gains of repeat testing for Clostridium difficile by enzyme immunoassay and PCR (i.e., initial negative result followed by positive result) within a 7-day period were 1.9 and 1.7%, respectively. There is little value of repeat testing for C. difficile by enzyme immunoassay or PCR.

Effect of telephoned notification of positive Clostridium difficile test results on the time to the ordering of antimicrobial therapy.

The time between electronic-medical-record reporting of a positive result of a test for Clostridium difficile toxin in stool and the ordering of antimicrobial therapy was compared during consecutive periods when results were not telephoned (n = 274) and when results were telephoned (n = 90) to the clinical service. The mean times to the ordering of antimicrobial therapy were 11.9 and 3.6 hours, respectively (P < .001).