Lecciones aprendidas

In considering the fact that TAC can detect 16S ribosomal RNA of organisms that might not be viable and therefore not causative of sepsis, we also performed TAC assay in blood of neonates considered to be well in order to assess the significance of finding an organisms in neonates with clinical sepsis. In this study we found that among the healthy neonates

(controls) 20% in the first 3 days of life and 27% in the age group 3-27 days had organism detected in blood. These findings brought into question whether blood is a true sterile site as it is commonly referred to or not, and secondly whether the finding of an organism in blood of a sick neonate means that the organism detected is a causative organism or not. The detection of viruses and bacteria in blood by TAC in healthy neonates in the current study challenges the notion that blood is a sterile site. Other studies have also reported that blood from healthy individuals can contain bacterial 16S ribosomal DNA.114-116

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The positive results in blood of healthy neonates based on TAC challenge the notion that healthy humans have sterile blood, as it suggests that non-culturable or dormant forms of organisms are present.350-354 Secondly finding non-culturable organisms such as Ureaplasma species and a statistical modelling using TAC suggests that the presence of a negative blood culture does not mean an absence of a causative organism. Therefore detection of organisms using PCR-based technology like TAC in patients with clinical sepsis should be interpreted with caution as some of the organisms might be dormant or non-viable and therefore not the cause of the current illness, although they have potential for causing disease when reactivated or resuscitated. The finding of organisms in the blood of healthy neonates makes it difficult to implicate an organism found in a neonate with clinical sepsis as being the causative organism. Therefore in order to assess which detected organisms contribute to illness in cases and what the odds are of detecting the pathogenetic organism, a statistically modelling was used for EOS and included positive blood cultures in cases and positive blood and nasopharyngeal results from TAC in both cases and controls. Using the statistical modelling only 27% of cases could be attributed to have aetiological organisms from the organisms which could be detected in blood culture or in TAC, thus 73% of cases could not be attributed a causative organism. Among those neonates with an attributed aetiology, the common pathogens were Ureaplasma species, GBS and Klebsiella pneumoniae. These three organisms are commonly found in the urogenital tract of pregnant women, suggesting acquisition from the mother. This concept is further supported by the finding that vaginal delivery is a predictor of culture- confirmed sepsis.

Though GBS and Klebsiella pneumoniae are commonly considered causes of neonatal sepsis, Ureaplasma species has not been considered a common pathogen in neonatal sepsis. The neonatal disease that has been reported to be associated with Ureaplasma colonization/ infection is bronchopulmonary dysplasia, a condition commonly seen in neonates born

preterm.355 Ureaplasma species are detected in 67% of sexually active women of reproductive age, compared to 40% of sexually inactive and 25% of postmenopausal women.356 The prevalence of amniotic fluid infection with Ureaplasma is seen 6-9% in those with preterm and intact membranes compared to 22% in those with preterm labour with ruptured

membranes.357-359 The rate of Ureaplasam species respiratory tract colonization increases with duration of rupture of membranes.360, 361 Therefore this could explain the difference between cases and controls in the prevalence of Ureaplasma in this study as more cases had prolonged rupture of membranes than controls. However, 45% of neonates with Ureaplasma on TAC

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were born preterm, leaving 55% being full-term infants suggesting that this infection is not limited only to those born preterm.

The finding in this study that organisms were identified in both NPOP and blood samples suggests possible translocation of the organism from the mucosa of the respiratory tract. This translocation can occur with or without inflammation.362 and therefore present with or

without clinical signs of infection making it difficult to attribute the illness to the presence of the organism. One study reported that 26% of neonates who had positive Ureaplasma in the lower respiratory tract also had bacteraemia363 and another study reported that 23% of

neonates had positive culture for Ureaplasma in cord blood.364 Therefore it appears that there is a relationship between the presence of Ureaplasma in blood and pharyngeal secretions, supporting translocation from the respiratory tract through the mucosa to the blood stream. A number of studies that looked at treatment of patients with positive tracheal aspirate cultures for Ureaplasma reported that macrolides led to clearance of the organism but no reduction in neonatal morbidity.365 The lack of effect on morbidity in these studies could be related to not having adequate sample size, secondly studying different types of macrolides or that

Ureaplasma does not cause diseases in the neonate. Therefore there is a need to conduct larger randomized clinical trials with clear enrolment criteria to assess the efficacy and safety of available macrolides. .