Urosepsis and uroprophylaxis

Overall prevalence

Approximately 5% of children aged 2 to 24 months with unexplained fever are found to have a UTI. Prevalence can range from 0.1% to 1% in all neonates and 9% to 25% when considering just preterm neonates. ^{, ,} Multiple studies have demonstrated that rates of UTIs increase with decreasing gestational age as well as decreasing birth weight. ^{, ,} Levy et al. reported UTI was significantly more common in very low birth weight (VLBW) infants than in infants with a birth weight of >1500 g (3.2% vs. 0.4%), and Drumm et al. noted the rate of UTI in their extremely low birthweight population was 13.8% vs. 8.5% in their VLBW infants. In general, overall prevalence has been difficult to determine due to inconsistent diagnostic criteria, which will be discussed later.

Rates of urosepsis

Urosepsis is defined as isolation of an identical bacterial pathogen in a concomitant blood culture and urine culture. Rates of urosepsis in term infants can vary from 4% to 12%. ^, In preterm neonates, rates of urosepsis have been found to be significantly higher, ranging anywhere from 11% to 38%. ^{, ,} In one of the largest retrospective reviews available, Downey et al. evaluated data from 322 neonatal intensive care units (NICUs) in the Pediatrix Medical Group network over a 13-year period to determine rates of concordance between positive urine cultures and blood or CSF cultures. They found that 13% of neonates with a UTI also had a concomitant blood culture with the same bacterial pathogen, and 3% had a positive CSF culture with the same pathogen. The risk of urosepsis increased with decreasing gestational age and birth weight, specifically in those infants born less than 26 weeks’ gestation and weighing less than 1500 g. Staphylococcus UTIs were most likely to be concordant (38%), followed by Candida (23%). Although gram-negative organisms were the most frequent causative organisms for UTIs in neonates, they were concordant with blood cultures only 6% of the time. Given the high rates of urosepsis in the preterm population as well as the elevated risk of concomitant meningitis, it is recommended that in an infant that appears clinically ill, clinicians obtain accurate and timely blood and CSF cultures whenever a UTI is suspected to ensure this vulnerable population is being treated appropriately.

Common pathogens

Escherichia coli is by far the most common causative pathogen in community-acquired UTIs in term infants and neonates and has been shown to account for up to 90% of infections in prior studies. In hospitalized preterm patients with predominantly nosocomially acquired UTIs, Klebsiella, Enterobacter spp., Enterococcus spp., coagulase-negative staphylococci, and Candida spp . are found with much higher frequency ( Table 15.1 ). E. coli is less commonly seen in this population, with an average incidence of approximately 18%, though some single-center studies have reported rates as high as 27% in the VLBW population. It is important to note that although coagulase-negative staphylococci is generally considered a contaminant in most term infants and older children, it can in fact be a causative agent for UTI in premature neonates. Downey et al. reported isolation of coagulase-negative staphylococci in 14% of catheterized urine culture samples from infants with suspected infection and 18% concordance with positive blood cultures.

Male predominance and the role of circumcision

Although female sex has previously been identified as a protective clinical factor with regards to neonatal UTI, a clear male predominance has been associated with UTI in both term and preterm infants. In multiple retrospective studies of term infants with community-acquired UTIs, approximately 75%–85% of the affected study population were male. ^, The same can be said for premature infants in the NICU, where approximately 65%–75% of positive UTIs are in male infants. ^{, ,}

Male infants who are uncircumcised have significantly higher rates of UTIs than those who have undergone circumcision. A metaanalysis by Shaikh et al. reported that among febrile male infants less than 3 months of age, only 2.4% of the boys who had been circumcised were diagnosed with a UTI and 20.1% of the uncircumcised boys had a UTI. A separate metaanalysis found that the single risk factor of lack of circumcision confers a 23.3% chance of UTI during one’s lifetime. Although there are limited data with regards to the effects of circumcision in premature infants on rates of UTIs, the data suggest that there are higher rates of UTI in preterm infants who are not circumcised by the time of discharge, and that circumcision may be beneficial in reducing the risk for recurrent future UTIs in this population. Clinicians should therefore be mindful of such trends when counseling families with preterm male infants on the risks and benefits of undergoing circumcision prior to discharge from a neonatal intensive care unit.