Natalie Banniettis

Comparison of Platforms for Testing Antibody Responses against the Chlamydia trachomatis Antigen Pgp3

Abstract. Antibody responses to Chlamydia trachomatis (CT) antigens may be useful tools for surveillance of trachoma by estimating cumulative prevalence of infection within a population. Data were compared from three different platforms—multiplex bead array (MBA), enzyme-linked immunosorbent assay (ELISA), and lateral flow assay (LFA)—measuring antibody responses against the CT antigen protein plasmid gene product 3 (Pgp3). Sensitivity was defined as the proportion of specimens testing antibody positive from a set of dried blood spots from Tanzanian 1–9-year olds who were positive for CT nucleic acid of all nucleic acid amplification test (NAAT)-positive individuals (N = 103). The sensitivity of the LFA could not be determined because of the use of dried blood spots for this test; this specimen type has yet to be adapted to LFA. Specificity was defined as the proportion of sera from U.S. and Bolivian 1–9-year olds that had previously tested negative by the Chlamydia microimmunofluorescence (MIF) assay testing negative to Pgp3-specific antibodies (N = 154). The sensitivity for MBA and ELISA was the same—93.2 (95% confidence interval [CI]: 88.3–98.1). Specificity ranged across platforms from 96.1 (95% CI: 91.8–98.2) to 99.4% (95% CI: 98.2–100). ELISA performance was similar regardless of whether the plates were precoated or freshly coated with antigen. Sensitivity and specificity of control panels were similar if the cutoff was determined using receiver operator curves or a finite mixture model, but the cutoffs themselves differed by approximately 0.5 OD using the different methodologies. These platforms show good sensitivity and specificity and show good agreement between tests at a population level, but indicate variability for ELISA outcomes depending on the cutoff determination methodology.

Seroprevalence of Chlamydia trachomatis in Inner-City Children and Adolescents—Implications for Vaccine Development

Background Prevention of Chlamydia trachomatis infection is an ideal application for a vaccine program, which should optimally be administered before sexual debut. However, there are limited epidemiologic studies of C. trachomatis infection in an unselected pediatric population since routine screening and treatment of pregnant women was implemented in the United States in 1993. Methods Anonymized serum samples were obtained from children younger than 21 years in 2 medical centers in Brooklyn, New York, from 2013 to 2015. Anti–C. trachomatis IgG antibody was determined by a validated enzyme immunoassay. Infants younger than 1 year were excluded from the final analysis due to interference of maternal antibody. Results One thousand two sera were included in the final analysis. Fifty-seven percent were females. No antibody was detected at younger than 11 years. Anti–C. trachomatis IgG antibody was detected in 11.4% and 5.6% of female and male subjects, respectively, older than 11 years (P = 0.0027), and seropositivity increased with age. There was no significant difference in the distribution of age at infection between the centers (P = 0.432), but a difference was detected between genders (P = 0.012) with a higher percentage of female subjects testing positive. Conclusions Antibody was first detected at 11 years of age, likely coinciding with sexual debut. The prevalence of antibody was higher and appeared earlier in females, mirroring national surveillance trends based on nucleic acid amplification testing. The delay in male antibody detection may be due to biological or behavioral differences between genders. These data are critical in informing potential C. trachomatis vaccine strategies.

Latent class modeling to compare testing platforms for detection of antibodies against the Chlamydia trachomatis antigen Pgp3

Latent class modeling can be used to combine the results of multiple tests to compare the sensitivity and specificity of those tests in the absence of a gold standard. Seroepidemiology for chlamydia infection may be useful for determining the cumulative risk of infection within a population. Initial studies using the Chlamydia trachomatis immunodominant antigen Pgp3 have shown utility for seroepidemiology of sexually transmitted chlamydia and the eye disease trachoma. We present our latent class modeling results for comparison of antibody data obtained from three different Pgp3-based platforms – multiplex bead array, ELISA, and lateral flow assay. Sensitivity and specificity estimates from the best fitting latent class models were similar to estimates derived from those previously obtained using a nucleic acid amplification test as a gold standard for sensitivity and non-endemic pediatric specimens for specificity, although the estimates from latent class models had wider confidence intervals. The modeling process and evaluation highlighted the importance of including as many antibody tests as possible when fitting a latent class model to ensure that as many patterns as possible are available for evaluation. Future studies designed to evaluate antibody test performance in the absence of a gold standard should utilize as many tests as possible.

Infective dermatitis associated with HTLV-1 infection in a girl from Trinidad: Case report and review of literature

Infective dermatitis (ID) associated with Human T‐cell leukemia virus type‐1 (HTLV‐1) is a rare form of severe superinfected eczema seen mostly in the Caribbean islands and Latin America. Although rapid response to antibiotic treatment is observed, patients should be monitored for development of complications associated with this retroviral infection, including T‐cell leukemia/lymphoma (ATLL) and HTLV‐1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). Infective dermatitis is rarely seen in the United States and therefore may be under‐recognized by physicians unfamiliar with this condition. Herein, we present an additional case report of an ID associated with HTLV‐1 in an 11‐year‐old girl from Trinidad.

Management Practices for Methicillin-Resistant Staphylococcus aureus Bacteremia by Adult Infectious Diseases Physicians.

Abstract To assess current use of vancomycin for methicillin-resistant Staphylococcus aureus bacteremia, we surveyed adult infectious disease physicians. Most respondents reported personal experience with infections failing to respond to vancomycin despite minimum inhibitory concentration data indicating susceptibility. In a hypothetical case of such an infection, most would change to daptomycin with or without other agents.

Steady-state pharmacokinetics of oral linezolid suspension in a premature infant with osteomyelitis

Sir, Linezolid has activity against a broad range of Gram-positive bacteria, including MRSA. As infections with these organisms have become more common in infants, linezolid may have an important role, particularly in preterm newborns. Most of the published data on pharmacokinetics, efficacy and safety of linezolid are from adult studies. It is established that the pharmacokinetics of linezolid, especially clearance, varies with age. Children younger than 12 years of age have a smaller AUC, faster clearance and shorter elimination half-life than adults. Paediatric data, including from neonates, are limited and were mainly evaluated using the intravenous (iv) formulation. – 6 These studies reported considerable interindividual variability in plasma concentrations within the study populations. To date, there are no steady-state pharmacokinetic studies assessing oral linezolid suspension in infants. We report the steady-state pharmacokinetic parameters of oral linezolid suspension in a premature infant with osteomyelitis. The project was approved by the institutional review board, informed consent was obtained and the research was conducted in accordance with the Declaration of Helsinki. A 4-month-old male infant born at 25 weeks gestation (birth weight 750 g) was being managed in the neonatal ICU for ongoing medical issues since birth; iv access proved challenging throughout the hospital course. On the 44th day of life, the infant developed a skin and soft-tissue infection of the left forearm at an old iv site, along with spontaneously draining pustules at the umbilicus. Cultures obtained from the forearm abscess grew MRSA with a vancomycin MIC of 2 mg/L. The isolate also was resistant to clindamycin. The infant was treated with vancomycin iv for 10 days, although a therapeutic trough was not achieved (3.6 mg/L). On the 89th day of life, the infant developed left ankle swelling at another old iv access site. Imaging revealed significant osteomyelitis of the distal tibia and fibula. Cultures from the bone grew a latex-negative Staphylococcus. However, further speciation and susceptibilities were not conducted as the laboratory discarded the sample. The infant was started on linezolid, iv at 10 mg/kg (29 mg) q8h. Treatment was monitored with serial serum inflammatory markers. Parenteral therapy was disrupted on several occasions as iv access was compromised. After 14 days of parenteral therapy, the infant was switched to oral linezolid suspension, 10 mg/kg q8h, for an additional 4 weeks. Blood samples obtained during the last week of oral linezolid therapy were analysed for quantification of linezolid using HPLC. Blood samples (0.5 mL) were obtained at time 0 before dosing and at 1, 1.5, 2, 4, 6 and 8 h after the oral dose of linezolid. An additional sample, 10 h after the prior dose and 2 h after the afternoon dose, also was obtained. Serum samples were shipped to the Infectious Disease Pharmacokinetics Laboratory in Gainesville (FL, USA) for serum concentration analysis. Linezolid concentrations were determined using a validated HPLC assay described previously. The plasma standard curve for linezolid ranged from 0.50 to 30 mg/L, with linearity extending below 0.50. The within-sample precision (percentage coefficient of variation) of validation in a single standard concentration was 0.69% and the overall validation precision across all standards was 1.04%–4.39%. Non-compartmental analysis of the data was performed with Phoenix software (v.6.4, Pharsight) to obtain the steady-state pharmacokinetic parameters. The 0 and 8 h sample concentrations (minimum plasma concentration, Cmin) were both 0.32 mg/L, confirming that steady-state had been achieved (Figure 1). The steady-state peak plasma concentration (Cmax) was 5.51 mg/L and the time to peak plasma concentration (Tmax) was 2 h. The second 2 h sample (10 h after the prior oral dose) was 3.99 mg/L, somewhat lower than the prior Cmax of 5.51 mg/L. This suggests that the rate of oral absorption varied from dose to dose. Typical linezolid peak concentrations are 12–26 mg/L 2 h after oral doses and trough concentrations are typically 3–9 mg/L. – 3 In this infant, despite q8h dosing, peak and trough concentrations were lower than typically seen. The volume of distribution divided by bioavailability (Vz/F), clearance divided by bioavailability (CL/F), elimination rate constant (kel, estimated with three concentrations), half-life (t1/2) and AUC0 – 8 were estimated at 3.48 L, 1.75 L/h, 0.50 h, 1.38 h and 16.56 mg.h/L, respectively. The pharmacokinetic profile of oral linezolid in our infant differed from what has been published in the literature for full-term infants. Full-term infants who received single doses of iv linezolid had much higher peak plasma concentrations, a larger AUC and a slower clearance. Our infant was born .3 months premature and was treated at a post-gestational age of 1 month (not equivalent to a full-term infant of the same age); therefore, direct correlation is challenging due to the differences in characteristics of the infants in the published studies. The Cmax and AUC were lower in our infant and apparent elimination t1/2 faster than what has been reported in full-term infants. Reasons for this may include incomplete absorption (F,1), faster clearance or a smaller actual volume of distribution. We were only able to estimate Vz/F, leaving our assessment of this parameter less than optimal. Pharmacokinetic data reported in studies in infants