Pertussis Pseudo-outbreak linked to specimens contaminated by Bordetella pertussis DNA From clinic surfaces

BACKGROUND AND OBJECTIVES

We investigated a pertussis outbreak characterized by atypical cases, confirmed by polymerase chain reaction (PCR) alone at a single laboratory, which persisted despite high vaccine coverage and routine control measures. We aimed to determine whether Bordetella pertussis was the causative agent and advise on control interventions.

METHODS

We conducted case ascertainment, confirmatory testing for pertussis and other pathogens, and an assessment for possible sources of specimen contamination, including a survey of clinic practices, sampling clinics for B pertussis DNA, and review of laboratory quality indicators.

RESULTS

Between November 28, 2008, and September 4, 2009, 125 cases were reported, of which 92 (74%) were PCR positive. Cases occurring after April 2009 (n = 79; 63%) had fewer classic pertussis symptoms (63% vs 98%; P < .01), smaller amounts of B pertussis DNA (mean PCR cycle threshold value: 40.9 vs 33.1; P < .01), and a greater proportion of PCR-positive results (34% vs 6%; P < .01). Cultures and serology for B pertussis were negative. Other common respiratory pathogens were detected. We identified factors that likely resulted in specimen contamination at the point of collection: environmentally present B pertussis DNA in clinics from vaccine, clinic standard specimen collection practices, use of liquid transport medium, and lack of clinically relevant PCR cutoffs.

CONCLUSIONS

A summer pertussis pseudo-outbreak, multifactorial in cause, likely occurred. Recommendations beyond standard practice were made to providers on specimen collection and environmental cleaning, and to laboratories on standardizing PCR protocols and reporting results, to minimize false-positive results from contaminated clinical specimens.

How adequate is adequate for the collection of endocervical specimens for Chlamydia trachomatis testing?

BACKGROUND

Endocervical specimen adequacy has been assessed by subjective criteria that are based on arbitrarily chosen thresholds for the presence of target cells observed on microscopic slide examinations.

GOAL OF THIS STUDY

To assess the relationship of chlamydia test positivity to specimen adequacy with the use of a semi-quantitative cytologic staining method for assessing endocervical specimen collection cellularity.

STUDY DESIGN

Endocervical specimens for chlamydia testing (PACE 2, GenProbe, San Diego, CA) and for a slide cytologic examination (n = 3,500) were collected in parallel. A semi-quantitative cytologic examination to determine a specimen adequacy (SA) score was performed for every chlamydia-positive result (n = 163) and approximately every fifth negative result (n = 626). The Chi-square test for linear trends was used to assess the relationship between SA scores and chlamydia positivity. The median SA scores for chlamydia-positive and negative slides were compared.

RESULTS

The median SA scores for chlamydia-positive and -negative slides were 27 and 20, respectively (P < 0.001). Chlamydia positivity rates increased with increasing specimen adequacy scores (0-9, 2.7%; 10-19, 15.1%; 20-29, 24.8%; and 30-45, 31.3%; Chi-square for linear trend: P < 0.001).

CONCLUSION

These results demonstrate a linear relationship between the numbers of cells observed on an endocervical smear and chlamydia positivity rather than the threshold concept in practice. The semiquantitative cytologic technique offers an objective method for further evaluating specimen adequacy for Chlamydia trachomatis testing.

A tale of two sexually transmitted diseases. Prevalences and predictors of chlamydia and gonorrhea in women attending Colorado family planning clinics

BACKGROUND

The comparative prevalences and predictors of chlamydia and gonorrhea have not been studied in the family planning clinic population.

GOALS

To determine the comparative prevalences and predictors of chlamydia and gonorrhea among Colorado family planning clinic patients.

STUDY DESIGN

Cross-sectional study of public and private family planning clinic patients in Colorado tested for both chlamydia and gonorrhea (n = 12,926).

RESULTS

Among women tested for both infections, the chlamydia prevalence rate was 4.5% and the gonorrhea prevalence rate was 0.5%. Multivariate analysis showed that independent predictors of chlamydia were age younger than 25 years, black or Hispanic race-ethnicity, cervical friability, mucopus, exposure to a sex partner with chlamydia, or multiple recent sex partners. Independent predictors of gonorrhea were age younger than 20 years, black or Hispanic race-ethnicity, or exposure to a sex partner with gonorrhea; adjusted odds ratios for exposure to gonorrhea and black race were the highest for either infection.

CONCLUSIONS

The gonorrhea prevalence rate was very low compared to that of chlamydia in patients at Colorado family planning clinics. Cost-effective gonorrhea testing strategies are needed for this population.

Which dogs bite? A case-control study of risk factors

OBJECTIVE

Dog bites cause an estimated 585,000 injuries resulting in the need for medical attention yearly and children are the most frequent victims. This study sought to determine dog-specific factors independently associated with a dog biting a nonhousehold member.

METHODS

A matched case-control design comprising 178 pairs of dogs was used. Cases were selected from dogs reported to Denver Animal Control in 1991 for a first-bite episode of a nonhousehold member in which the victim received medical treatment. Controls were neighborhood-matched dogs with no history of biting a nonhousehold member, selected by modified random-digit dialing based on the first five digits of the case dog owner's phone number. Case and control dog owners were interviewed by telephone.

RESULTS

Children aged 12 years and younger were the victims in 51% of cases. Compared with controls, biting dogs were more likely to be German Shepherd (adjusted odds ratio (ORa) = 16.4, 95% confidence interval (CI) 3.8 to 71.4) or Chow Chow (ORa = 4.0, 95% CI 1.2 to 13.7) predominant breeds, male (ORa = 6.2, 95% CI 2.5 to 15.1), unneutered (ORa = 2.6, 95% CI 1.1 to 6.3), residing in a house with > or = 1 children (ORa = 3.5, 95% CI 1.6 to 7.5), and chained while in the yard (ORa = 2.8, 95% CI 1.0 to 8.1).

CONCLUSIONS

Pediatricians should advise parents that failure to neuter a dog and selection of male dogs and certain breeds such as German Shepherd and Chow Chow may increase the risk of their dog biting a nonhousehold member, who often may be a child. The potential preventability of this frequent public health problem deserves further attention.

Seroepidemiological characterization of a syphilis epidemic in the Republic of the Marshall Islands, formerly a yaws endemic area

The annual numbers of reported cases of syphilis in the Republic of the Marshall Islands (RMI) increased from none in 1983 to more than 600 in 1989, suggesting a large outbreak of syphilis. Much of the increase resulted from expanded serological screening. The apparent outbreak of syphilis, therefore, may have been partly the result of increased surveillance or, since the RMI was formerly a yaws endemic area, possibly due to a resurgence of yaws. To address this problem and better characterize the epidemic, we analysed results from a 1989/90 Ministry of Health Services mass serological screening on Majuro Atoll, the main population centre. Serum specimens from 9160 people (86% of residents aged 15-44 years) on Majuro were screened with the rapid plasma reagin (RPR) card test; we repeated the RPR and performed a confirmatory microhaemagglutination assay for Treponema pallidum-specific antibodies (MHA-TP) on a sample of serum specimens. To estimate the seroprevalence of syphilis, we also tested a sample of RPR nonreactive specimens by MHA-TP. Among people less than 45 years of age, total (11.5%) and high-titre (5.2%) seropositivity rates were highest in the 20-24 year age group, as was MHA-TP seroprevalence (15.9%). These results suggested that a large outbreak of syphilis was responsible for the observed seroreactivity. Cumulative incidence modelling and comparisons with the results of a previous serosurvey conducted in 1985 suggested that the duration of the syphilis epidemic was approximately 10 years and that incidence had not increased appreciably since 1985.

Diverging gonorrhea and syphilis trends in the 1980s: are they real?

BACKGROUND

The purpose of this study was to evaluate whether the divergence in national trends of gonorrhea and syphilis from 1986 to 1989 in the United States was real and if overall trends masked a contemporaneous increase in both diseases in a core group.

METHODS

We analyzed the following: (1) reported cases of gonorrhea and primary and secondary syphilis in the United States for the years 1981 to 1989, (2) gonorrhea screening results from six states for the years 1985 to 1989, and (3) reported cases of gonorrhea and primary and secondary syphilis by census tract for the years 1986 to 1989 in one city.

RESULTS

The incidence of gonorrhea decreased 22% in the United States from 1986 to 1989 while the incidence of primary and secondary syphilis increased 59%. Among Blacks, syphilis incidence increased 100% and gonorrhea incidence decreased 13%; among Whites and Hispanics, the incidence of both diseases decreased. Results from gonorrhea screening among females in six states agree with gonorrhea incidence trends in those areas. Race-specific and census tract analyses of data from a number of metropolitan areas where overall rates diverged did not demonstrate a group in which the incidence of both diseases increased.

CONCLUSIONS

We conclude that diverging trends of gonorrhea and syphilis from 1986 to 1989 are real and emphasize differences in the epidemiologic characteristics of these two sexually transmitted diseases.