Evaluation of Nucleic Acid Isothermal Amplification Methods for Human Clinical Microbial Infection Detection

Battling infection is a major healthcare objective. Untreated infections can rapidly evolve toward the condition of sepsis in which the body begins to fail and resuscitation becomes critical and tenuous. Identification of infection followed by rapid antimicrobial treatment are primary goals of medical care, but precise identification of offending organisms by current methods is slow and broad spectrum empirical therapy is employed to cover most potential pathogens. Current methods for identification of bacterial pathogens in a clinical setting typically require days of time, or a 4- to 8-h growth phase followed by DNA extraction, purification and PCR-based amplification. We demonstrate rapid (70-120 min) genetic diagnostics methods utilizing loop-mediated isothermal amplification (LAMP) to test for 15 common infection pathogen targets, called the Infection Diagnosis Panel (In-Dx). The method utilizes filtration to rapidly concentrate bacteria in sample matrices with lower bacterial loads and direct LAMP amplification without DNA purification from clinical blood, urine, wound, sputum and stool samples. The In-Dx panel was tested using two methods of detection: (1) real-time thermocycler fluorescent detection of LAMP amplification and (2) visual discrimination of color change in the presence of Eriochrome Black T (EBT) dye following amplification. In total, 239 duplicate samples were collected (31 blood, 122 urine, 73 mucocutaneous wound/swab, 11 sputum and two stool) from 229 prospectively enrolled hospital patients with suspected clinical infection and analyzed both at the hospital and by In-Dx. Sensitivity (Se) of the In-Dx panel targets pathogens from urine samples by In-Dx was 91.1% and specificity (Sp) was 97.3%, with a positive predictive value (PPV) of 53.7% and a negative predictive value (NPV) of 99.7% as compared to clinical microbial detection methods. Sensitivity of detection of the In-Dx panel from mucocutaneous swab samples was 65.5% with a Sp of 99.3%, and a PPV of 84% and NPV of 98% as compared to clinical microbial detection methods. Results indicate the LAMP-based In-Dx panel allows rapid and precise diagnosis of clinical infections by targeted pathogens across multiple culture types for point-of-care utilization.

Prenatal diagnosis and therapy for a fetal hepatic vascular malformation

BACKGROUND

Congenital hepatic arteriovenous malformations complicated by high-output heart failure and hematologic derangements are associated with up to 90% mortality. Prenatal diagnosis alerts the pediatrician to the need for early neonatal intervention.

CASE

A fetal hepatic arteriovenous malformation with associated high-output cardiac failure was diagnosed at 29 weeks' gestation using real-time and color flow Doppler sonography. Hydrocortisone injected directly into the umbilical vein and the amniotic sac resulted in appreciable improvement in hemodynamic and hematologic indices. The pregnancy ended in a preterm delivery at 31 weeks with no evidence of heart failure at birth.

CONCLUSION

The compromised preterm fetus with a hepatic arteriovenous malformation can be treated in utero, avoiding early emergency delivery.