Diagnosing symptomatic urinary tract infections in infants by catheter urine culture

Contamination rates of different methods of urine culture collection in children: A retrospective cohort study

AIM

Urinary tract infection is a common cause of paediatric morbidity. However, there is no consensus on the default method for urine culture collection in children. This study aimed to examine the contamination rates of different urine collection methods.

METHODS

This was a retrospective cohort study in a paediatric emergency department. Data were collected from electronic health records on all children whose urine culture samples were obtained in the paediatric emergency department between March 2018 and March 2019. Different methods of urine collection included the midstream (MS) method, clean catch (CC), transurethral bladder catheterisation and suprapubic aspiration. Contamination rates and positive urine culture rates were calculated and compared for sex, age, and collection method.

RESULTS

Urine culture samples were collected from 1507 children. There were 284 (18.8%) cultures that were positive with significant growth and 52 (3.5%) that were defined as 'contaminated'. The contamination rates for the midstream method in toilet-trained children were 1.6% (10/609), 4.9% (17/348) for CC in pre-continent children, 4.9% (25/515) for transurethral bladder catheterisation and 0% (0/35) (P = 0.006) for suprapubic aspiration. There was no significant difference in contamination rates of urine cultures collected by CC and catheterisation in the compared groups. The rates of positive cultures in the subgroup of children with high suspicion for Urinary tract infection were also found to be similar.

CONCLUSIONS

Our study shows that CC is non-inferior to catheterisation for collecting urine cultures in young children.

Catheter-Obtained Urine Culture Contamination Among Young Infants: A Prospective Cohort Study

Objectives: A correct diagnosis of urinary tract infection in young infants requires an uncontaminated urine culture, commonly obtained by urethral catheterization. In the current study, we examined the rates and factors associated with contaminations of catheter-obtained urine cultures in very young infants. Methods: This prospective cohort study included 143 catheter-obtained urine cultures of infants ≤2 months of age admitted to the pediatric ward of a tertiary hospital in Israel from April 2019 to September 2020. Patient's and operator's study variables were documented at the time of catheter insertion. Positive urine cultures were reviewed by a pediatric nephrologist and a pediatric infectious disease specialist and designated as infection or contamination. The study variables were compared between those with or without contamination. Results: The contamination rate in our cohort was 29%. Females were more than twice as likely to have a contaminated urine culture (37 vs. 18%, respectively, P = 0.014). Circumcision status, official training about sterile catheterization, a sense of difficult catheterization, and the shift in which the culture was obtained did not influence the contamination rate. Conclusions: Catheter-obtained urine cultures have a high contamination rate among very young infants, especially among girls.

Microbiota—implications for immunity and transplantation

Each individual harbours a unique set of commensal microorganisms, collectively referred to as the microbiota. Notably, these microorganisms exceed the number of cells in the human body by 10-fold. This finding has accelerated a shift in our understanding of human physiology, with the realization that traits necessary for health are both encoded and influenced by the human genome and the microbiota. Our understanding of the aetiology of complex diseases has, therefore, evolved with increasing awareness that the human microbiota has an active and critical role in maintaining health and inducing disease. Indeed, findings from bioinformatic studies indicate that the microbiota and microbiome have multiple effects on the innate and adaptive immune systems, with effects on infection, autoimmune disease and cancer. In this Review, we first address the important statistical and informatics aspects that should be considered when characterizing the composition of microbiota. We next highlight the effects of the microbiota on the immune system and the implications of these effects on organ failure and transplantation. Finally, we reflect on the future perspectives for studies of the microbiota, including novel diagnostic tests and therapeutics.

Comparison of Escherichia coli uropathogenic genes (kps, usp and ireA) and enteroaggregative genes (aggR and aap) via multiplex polymerase chain reaction from suprapubic urine specimens of young children with fever

OBJECTIVE

Escherichia coli is the most frequently identified microbiological agent in childhood urinary tract infections (UTIs). However, the pathogenic role of this organism in young children remains to be clearly elucidated. So far, no studies have been conducted in which multiplex polymerase chain reaction (PCR) has been applied to determine the association between childhood UTIs and E. coli and urovirulent genes.

MATERIAL AND METHODS

Altogether, 330 suprapubic urine specimens from febrile young children were cultured. In 33 of the cases, E. coli was identified; among these cases, 18 had a UTI (>10(4)-10(5) cfu/ml), four had a suspected UTI (>10(2)-10(3) cfu/ml) and 11 did not have UTIs (10(2) cfu/ml). Using multiplex PCR, three uropathogenic E. coli (UPEC) genes and two enteroaggregative E. coli (EAEC) genes were detected.

RESULTS

In the UTI-UPEC cases, the kps gene was detected in 18 of 22 cases (82%) and the usp gene in 16 of 22 cases (73%). Among the 18 cases of children with UTIs characterized by 10(4)-10(5) E. coli cfu/ml, urinary tract abnormalities were identified via dimercaptosuccinic acid scans in seven of 18 cases (39%) and via voiding cystourethrograms in four of the 18 cases (22%).

CONCLUSIONS

The UPEC kps and usp genes were clearly associated with childhood UTIs, and may also be associated with kidney or urinary tract dysfunctions in young children. Escherichia coli colony count numbers in excess of 10(4)-10(5) cfu/ml in the suprapubic urine were considered to be strong evidence of UTI in infants.

[Microbiological diagnosis of urinary tract infections]

Definitive diagnosis of urinary tract infection (UTI) is performed through quantitative urine culture. Traditionally the presence of 100,000 or more bacteria/ml in urine has been considered to represent significant bacteriuria, indicating UTI. However, this criterion is only applicable to certain population groups and cannot currently be considered an absolute criterion. The "real" presence of any number of bacteria in urine can represent a UTI when there are specific symptoms and pyuria. In the last few years various automatic systems have been introduced onto the market which, by adapting classical diagnostic techniques, allow the presence of a UTI to be rapidly ruled out, although their clinical utility is controversial. In addition, the new chromogenic culture media allow direct identification of uropathogens and, in particular, are of enormous help in the detection of polymicrobial cultures. Likewise, automatic systems can provide results on identification and sensitivity to be obtained in a single day. However, because new phenotypes of resistance are continually appearing, the antibiogram model used with classical uropathogens has had to be modified, requiring special techniques for pathogen detection and characterization. Correct interpretation of the antibiogram in these cases is essential to detect these phenotypes and achieve therapeutic success.

Pediatric urinary tract infections

Pediatric urinary tract infections are common. These infections have been recognized as a source of acute morbidity and long-term medical consequences in adulthood. There are various risk factors and clinical presentations in children with urinary tract infections. The main objectives in management include prompt diagnosis, appropriate antimicrobial therapy, identification of anatomic anomalies, and, in select patients, long-term follow-up.