Introduction

A urinary tract infection (UTI) is an infection of any part of the urinary tract, the organs that facilitate urination, which include: 

• Kidneys: where urine is produced
• Ureters: which connect the kidney to the urinary bladder
• Urinary bladder: where urine is stored
• Urethra: through which urine is expelled

In newborns, urinary tract infections are common, although they typically do not occur in the first few days of life. Bacteria, specifically a type of bacterium called Escherichia coli (E. coli), are responsible for the majority of UTIs in newborns. Most cases of UTIs in newborns occur in those who are assigned male at birth and uncircumcised. When an infant’s birth parent has had a UTI during pregnancy, the risk of a UTI occurring in the infant is increased.^1,2,3 

Typically, UTIs in newborns present with a fever, poor feeding, vomiting, diarrhoea, difficulty breathing or rapid breathing, and fatigue. Nonetheless, UTIs and the signs and symptoms they cause can be combated with medication, most often antibiotics. There is a risk of UTIs recurring in newborns, with this risk being highest in the first six months following a UTI initially occurring; therefore, understanding the nature of UTIs in newborns is very important.^1,2,3 

Causes of urinary tract infections in newborns

UTIs in newborns are caused by micro-organisms, mostly bacteria, but sometimes by fungi too. Though E. coli is the most common cause of UTIs in newborns, several factors can play a role in the likely cause of a UTI in a newborn.³

Bacteria

Bacteria are the most common cause of UTIs in newborns, specifically E. coli. Newborns assigned male at birth and who have a condition called vesicoureteral reflux, where urine flows back from the bladder to the ureters, are more prone to UTIs resulting from bacteria different from E. coli. Some of these bacteria are Klebsiella pneumoniae, Proteus mirabilis, Proteus vulgaris, Enterobacter aerogenes, and Pseudomonas aeruginosa, among others. Infants born prematurely also may be more likely to have a UTI caused by these less common bacteria.³

Fungi

Fungi are not a common cause of UTIs in newborns. If a UTI caused by fungi occurs, it is more likely due to a type of fungus called Candida, especially in premature newborns.³

Signs and symptoms 

Not all newborns with a UTI will present the same symptoms, as there is a range of signs and symptoms that can result from UTIs, including:³

• Fever
• Poor feeding
• Vomiting
• Diarrhoea
• Difficulty breathing or rapid breathing
• Grunting
• Fatigue
• Yellowing of the skin 

Diagnosis 

Several techniques can be used to diagnose UTIs in newborns. These techniques include physically examining the infant, collecting a urine sample, and imaging techniques.^{3, 4}

Physical examination

A physical examination provides the physician with an opportunity to see some of the signs and symptoms a newborn with a UTI may be experiencing, such as a fever, vomiting, diarrhoea, and grunting, and therefore, the opportunity to help decide what further testing should be done and get closer to forming a diagnosis of the condition.⁵

Urine sample

Collection of a urine sample and its analysis may help determine the organism responsible for the UTI. Furthermore, other substances in urine can indicate the presence of a UTI. High quantities of white blood cells in the urine are indicative of an infection. Additionally, some bacteria produce specific substances which can be present in urine and may further point to the presence of a UTI upon detection.³

Imaging techniques

UTIs can impact anywhere across the urinary tract and can cause changes in its structures. As a result of this, ultrasounds of the urinary tract’s structures can help confirm a diagnosis of UTIs in newborns as they can allow structural abnormalities to be visualised. An ultrasound involves a probe being placed on the skin overlying the area of the body being imaged. This probe produces sound waves which bounce off parts of the body and create echoes which can then lead to the generation of an image of the internal area of the body where the probe is placed.⁴

Treatment 

The treatment of UTIs in newborns varies depending on what organism is causing the infection, specifically. Antibiotics are the most common choice for the treatment of UTIs and include amoxicillin, ceftriaxone, and gentamicin. Depending on the cause of the UTI, or the choice of antibiotic, the antibiotic may be administered intravenously (IV), as an injection into muscle (IM), or orally.^3,4

Sometimes, after taking an antibiotic, but before the prescribed course is completed, signs and symptoms of an infection may subside; however, it is still crucial to complete the prescribed course of antibiotics to ensure that the bacteria causing the infection are cleared completely.

Complications 

Though not necessarily common, UTIs can sometimes result in complications, including:⁶

• Inflamed prostate
• Infections of the kidneys
• High blood pressure
• Leaky urine
• Future UTIs
• Kidney failure

FAQs

Are there risk factors that increase the likelihood of urinary tract infections occurring in newborns?

Certain factors can make it more likely that a newborn is diagnosed with a UTI. Newborns born prematurely are more likely to have a UTI. Furthermore, newborns with vesicoureteral reflex are also more likely to have a UTI. As well as that, if mothers have a UTI during pregnancy, then they are more likely to have a newborn who has a UTI.³

How common are urinary tract infections in newborns?

UTIs in infants are common; however, they are less likely to occur in the first few days of life.³

Can urinary tract infections in newborns be a sign of an underlying condition?

UTIs in newborns may be indicative of an underlying condition, as some conditions, such as vesicoureteral reflux, may make it likelier that an infant has a UTI.³

Summary

UTIs are infections of the urinary tract and are common in infants, though less likely to occur in the first few days of life. Typically, UTIs are caused by bacteria, mostly E. coli, but fungi can also potentially cause UTIs. UTIs do not impact newborns in the same way as signs and symptoms, which can include a fever, vomiting, and diarrhoea, can vary from patient to patient. Some newborns are more susceptible to UTIs, such as those with mothers who had a UTI during pregnancy, who have vesicoureteral reflux, and who were born prematurely. UTIs in newborns are typically cleared and treated with a course of antibiotics.