Urinary tract infection in full-term newborn infants: value of urine culture by bag specimen collection

Infecção urinária em recém-nascido de termo: valor da cultura de urina obtida através de saco coletor

Abstracts

OBJETIVE: to evaluate the efficacy of urine culture by bag specimen for the detection of neonatal urinary tract infection in full-term newborn infants. Retrospective study (1997) including full-term newborn infants having a positive urine culture (>100,000 CFU/ml) by bag specimen collection. The urinary tract infection diagnosis was confirmed by positive urine culture (suprapubic bladder aspiration method). The select cases were divided into three groups, according to newborn infant age at the bag specimen collection: GI (< 48 h, n = 17), GII (48 h to 7 d, n = 35) and GIII (> 7 d, n = 9). Sixty one full-term newborn infants were studied (5.1 % of total infants). The diagnosis was confirmed on 19/61 (31.1 %) of full-term infants born alive. Distribution among the groups was: GI = 2/17 (11.8 %), GII = 10//35 (28.6 %), and GIII = 7/9 (77.7 %). The most relevant clinical symptoms were: fever (GI - 100 %, GII - 91.4 %) and weight loss (GI - 35.3 %, GII - 45.7 %). Urine culture results for specimens collected by suprapubic aspiration were: E. coli GI (100 %), GII (40 %) and GIII (28.6 %), E. faecalis GI (30%), Staphylococcus coagulase-negative GII (20 %) and GIII (42.8 %), and Staphylococcus aureus GII (10 %). Correlation between positive urine culture collection (bag specimen method) and urinary tract infection diagnosis, using relative risk analysis, produced the following results: GI=0.30 (CI95% 0.08-1.15), GII=0.51 (CI 95% 0.25-1.06) and GIII=3.31 (CI95% 1.8-6.06) The most frequent urinary tract infection clinical signs in the first week were fever and weight loss, while non-specific symptomatology occurred later. E. coli was most frequent infectious agent, although from the 7th day of life, staphylococcus was noted. The urine culture (bag specimen method) was effective in detecting urinary tract infection only after the 7th day of life.

Urine culture; Urinary tract infection; Newborn infant

URINARY TRACT INFECTION IN FULL-TERM NEWBORN INFANTS: VALUE OF URINE CULTURE BY BAG SPECIMEN COLLECTION

Mário Cícero Falcão, Cléa Rodrigues Leone, Renata A. P. D'Andrea, Roberta Berardi, Nilce A. Ono and Flávio Adolfo Costa Vaz

RHCFAP/2969

FALCÃO, M. C. et al. - Urinary tract infection in full-term newborn infants: value of urine culture by bag specimen collection. Rev Hosp Clín Fac Med S Paulo, 54 (3): 91 - 96,1999.

SUMMARY: Objective: to evaluate the efficacy of urine culture by bag specimen for the detection of neonatal urinary tract infection in full-term newborn infants. Retrospective study (1997) including full-term newborn infants having a positive urine culture (>100,000 CFU/ml) by bag specimen collection. The urinary tract infection diagnosis was confirmed by positive urine culture (suprapubic bladder aspiration method). The select cases were divided into three groups, according to newborn infant age at the bag specimen collection: GI (< 48 h, n = 17), GII (48 h to 7 d, n = 35) and GIII (> 7 d, n = 9). Sixty one full-term newborn infants were studied (5.1 % of total infants). The diagnosis was confirmed on 19/61 (31.1 %) of full-term infants born alive. Distribution among the groups was: GI = 2/17 (11.8 %), GII = 10//35 (28.6 %), and GIII = 7/9 (77.7 %). The most relevant clinical symptoms were: fever (GI - 100 %, GII - 91.4 %) and weight loss (GI - 35.3 %, GII - 45.7 %). Urine culture results for specimens collected by suprapubic aspiration were: E. coli GI (100 %), GII (40 %) and GIII (28.6 %), E. faecalis GI (30%), Staphylococcus coagulase-negative GII (20 %) and GIII (42.8 %), and Staphylococcus aureus GII (10 %). Correlation between positive urine culture collection (bag specimen method) and urinary tract infection diagnosis, using relative risk analysis, produced the following results: GI=0.30 (CI95% 0.08-1.15), GII=0.51 (CI 95% 0.25-1.06) and GIII=3.31 (CI95% 1.8-6.06) The most frequent urinary tract infection clinical signs in the first week were fever and weight loss, while non-specific symptomatology occurred later. E. coli was most frequent infectious agent, although from the 7th day of life, staphylococcus was noted. The urine culture (bag specimen method) was effective in detecting urinary tract infection only after the 7th day of life.

DESCRIPTORS: Urine culture. Urinary tract infection. Newborn infant.

Urinary tract infection is generally defined as the presence of microorganisms in the urine, revealed without contamination, with or without symptoms¹⁴.

Diagnosis of neonatal urinary tract infection is difficult due to lack of specific symptomatology. Symptoms can include the presence of fever, weight loss debilitate suction, feeding intolerance, failure to thrive, vomiting, diarrhea, abdominal distension, hypoactivity, irritability, cyanosis, hepatomegaly, splenomegaly, jaundice, and late-onset sepsis symptoms.³ For these reasons, diagnosis depends on the urine culture¹⁰.

Failure of urine culture to produce reliable results can most commonly be associated with improper material transport and inadequate collection methods^5,10.

Urine collection by bag specimen is widely used, since it is safe and easy; however, this method is characterized by low reliability due to bacterial contamination^8,9.

The purpose of this study was to evaluate the efficacy of urine culture by bag specimen for the detection of neonatal urinary tract infection in full-term newborn infants.

PATIENTS AND METHODS

We conducted a retrospective study in Berçário Anexo à Maternidade - Instituto da Criança "Prof. Pedro de Alcântara - Hospital das Clínicas - Faculdade de Medicina da Universidade de São Paulo, including all full-term newborn infants (gestational age - 37 to 42 weeks) having positive urine culture by bag specimen collection.

Collection was prescribed based on clinical data as follows: fever (T > 37.8 ºC)¹⁹, weight loss > 10% of birth weight, or non-specific symptomatology (feeding intolerance, failure to thrive, hypoactivity, debilitate suction, or irritability). In these cases, culture of urine specimens collected by suprapubic bladder aspiration was conducted to confirm diagnosis.

The select cases were divided into three groups, according to newborn infant age at the bag specimen collection: GI (< 48 hours), GII (48 hours to 7 days) and GIII ( > 7 days) (See Figure 1).

The finding of 100,000 CFU/ml of the same microorganism constituted a positive test for the bag specimen collection. The finding of any CFU/ml rate constituted a positive test for specimens collected by suprapubic aspiration^5,7,14 .

The study population was characterized by gestational age, birth weight, sex, perinatal asphyxia (Apgar score < 6 at 5 minutes), and membrane rupture time (< 24 hours and > 24 hours).

The procedure for collection of the bag specimens was: antisepsis, followed by fitting of a sterile plastic bag on the genitalia. If diuresis did not occur within 30 minutes, the procedure was repeated until successful specimen collection²⁰.

Suprapubic aspiration of the urine specimen required a full bladder. The overlying skin was disinfected, the bladder was puncture above the symphysis pubis with a 25-gauge needle on a syringe, and about 2 ml of urine was aspirated²⁰.

All urine specimens were transported promptly to the laboratory. Urine specimens were processed onto CLED, Mac Conkey, Thayer-Martin, thioglycolate and blood agar plates. Culture plates were incubated at 35-37 ^oC and read at 24-48 hours; if results were positive an antibiotic susceptibility was determined. The absence of microorganisms within 48 hours characterized the culture as negative²¹.

Data were analyzed through chi-square, Fischer exact test, Student's t test and relative risk. Statistical significance was defined as p< 0.05.

RESULTS

Sixty-one full-term newborn infants were included in this study, representing 5.1% of the total infants born alive in the study period.

The infants were distributed into three groups according to age at the time of sampling (Figure 1): GI (< 48 hrs, n = 17), GII (48 hrs - 7 days, n = 35) and GIII (> 7 days, n = 9) (Table 1)

The most relevant clinical symptoms were fever (GI - 100 %, GII - 91.4 %) and weight loss (GI - 35.3 %, GII - 45.7 %). shows the study population (Table 2).

The diagnosis was confirmed on 19/61 (31.1%) of full-term infants born alive. Distribution of positive diagnosis among groups was: GI = 2/17 (11.8%), GII = 10//35 (28.6%) and GIII = 7/9 (77.7%). No complication occurred from specimen collection by the suprapubic method.

The microbial content of cultures of urine specimens collected by suprapubic aspiration were: E. coli GI (100 %), GII (40 %) and GIII (28.6 %), E. faecalis GI (30 %), Staphylococcus coagulase-negative GII (20 %) and GIII (42.8 %), and Staphylococcus aureus GII (10 %) (Table 3).

Correlation between positive urine culture collection (bag specimen method) and urinary tract infection diagnosis, using relative risk analysis, produced the following results: GI = 0.30 (CI95% 0.08-1.15), GII = 0.51 (CI95% 0.25-1.06) and GIII = 3.31 (CI95% 1.8-6.06) (Table 4).

DISCUSSION

Urinary tract infection in the neonatal period has non-specific symptomatology, so its diagnosis is based on laboratory data³ .

All urine specimens should be transported and should be processed within two hours after collection, because at room temperature (25 ºC), Gram-negative microorganisms proliferate quickly. If a delay in transport or processing can not be avoid, specimens may be refrigerated (4 º C) up to 24 hours⁷.

Urine collected during the neonatal period can be obtained by bag specimen, suprapubic bladder aspiration, or urethral catheterization¹⁸.

Culture results after bag specimen collection are rarely false negative, and therefore can be used as a screen for urinary tract infection; however, false positive results are frequent⁶. Therefore, positive results should be confirmed by one of the other methods mentioned above. With bag specimen collection, several variables may affect the results, including: improper antisepsis, mainly in male newborn infants; difficulty with preputial hygiene; the requirement for replacement of the bag after 30 minutes in the absence of diuresis; pernicious skin lesions, occurrence of colonized distal urethra, mainly by Gram-negative bacteria; inadequate antiseptic methods²⁰. Incomplete soap removal from the perineal skin can inhibit bacterial growth²⁰.

As previously shown, urine collected by the suprapubic bladder aspiration method is the best approach for diagnosis of neonatal urinary tract infection because of its reliability, simplicity, and safety¹.

The study population had a 1.6 % urinary tract infection frequency, a rate close to the low incidence limit of this pathology in the neonatal period. This finding may be due to the low risk factors in the study population. In terms of urinary tract infection, the majority of newborns was admitted to low or medium risk units. It is worth noting that long confinement periods, associated pathologies, or massive use of antibiotics and invasive procedures increase the rate of urinary tract infection¹¹.

There were no differences in birth weight, gestational age, nutritional status, and membrane rupture time (table 1) (p>0.05) in the three groups studied. Differences between groups related to perinatal asphyxia only. Theoretically, asphyxia might indirectly increase the risk of urinary infection, but none of the asphyxiated infants required long confinement in the nursery.

The incidence of fever in groups GI (100 %) and GII (92 %) was higher than that reported in the literature (about 50 %), whereas GIII had and incidence of fever (44 %) close that that reported in literature^4,14. Weight loss and non-specific symptomatology were slightly below the incidence reported in the literature results¹⁴. These findings emphasize that the urinary tract infection in the newborn infant has poor symptomatology, since several neonatal pathologies present same clinical findings. Roughly 7.5% of newborns have fever as a unique symptom that progresses to urinary infection and eventually can develop to late-onset sepsis¹⁴.

In order to confirm the diagnosis, culture of urine collected by suprapubic bladder aspiration was performed with positive results in 31 % of the total, distributed as: GI = 12 %, GII = 29 %, and GIII = 78 %. These results merit discussion because confirmation of the urinary tract infection diagnosis occurred in only one-third of those cases that had positive tests on bag specimen cultures. Infants would be exposed to unnecessary antibiotics if bag specimen collection were used as the only diagnosis technique. Because the health and financial costs of unnecessary antibiotic exposure are significant, a more reliable method such as suprapubic bladder aspiration is recommended².

The suprapubic bladder aspiration method was first used in the 50's, and was first used during the neonatal period in the 60's^1.5. Through improved techniques, this method has became safe, even for preterm newborn infants¹. We emphasize that the procedure is very simple, since when bladder is full-sized, it stays closer to abdominal wall, making the puncture easier and leading to 90 % success on first puncture attempt^14. Ultrasonography for orientation should be conducted in the presence of abdominal distension or urinary tract anomalies, increasing efficacy to 96 %¹³. Transient hematuria caused by the puncture has been reported in only 0.6 % of cases, with no consequences¹⁴. Although gross hemorrhage, hematoma, bowel perforation, peritonitis, abdominal wall abscess, and bacteremia have been reported as more serious complications¹⁷ , no complications were noted in the present study, supporting the safety of this method.

Urethral catheterization could be used if suprapubic aspiration is not indicated (because of a clinical condition or several unsuccessful attempts), but it is associated with the risk of inducing an infection (4 to 6 %) and is technically more difficult, particularly with male preterm newborn infants³.

Gram-negative bacteria occurred at higher frequencies in the first days of life followed later by the presence of gram-positive microorganisms (Staphylococcus coagulase-negative and Staphylococcus aureus). These results are in accordance with the literature, indicating a changing urinary tract infection diagnosis, in which E. coli is not the predominant agent, being replaced to the enteroccocus, staphylococcus, and fungi. This may be explained by the increasing use of invasive procedures and long-term confinements in neonatal intensive care units, predisposing staphylococcus and fungi urinary tract infections¹².

Correlation between positive urine culture collection (bag specimen method) and urinary tract infection diagnosis using relative risk analysis showed that concordance between methods is higher, the higher the age of the infant. This finding is probably due to greater technical ease in collecting bag specimens from older infants, resulting in more reliable data.

In conclusion, the most frequent urinary tract infection clinical signs during the first week were fever and weight loss, while non-specific symptomatology manifested later. E. coli was most frequent microbial agent, although Staphylococcus was noted from the 7^th day of life. Results of urine culture from bag specimens were reliable only after 7 days of age.

Thus, the suprapubic bladder aspiration method is recommended for making accurate etiologic diagnoses. The negative culture of specimens collected using bag collection can be used as a screen to exclude a diagnosis of urinary infection.

RESUMO

RHCFAP/2969

FALCÃO, M. C. e col. - Infecção urinária em recém-nascido de termo: valor da cultura de urina obtida através de saco coletor. Rev Hosp Clín Fac Med S. Paulo, 54 (3) 91 - 96,1999

Objetivo: avaliar a eficácia da cultura de urina obtida através de saco coletor na detecção de infecção do trato urinário no período neonatal.

Estudo retrospectivo (1997), englobando recém-nascidos de termo com urocultura positiva (>100000UFC/ml) colhida em saco coletor. Nesses recém-nascidos foi realizada punção suprapúbica, coletando-se urina para cultura, para confirmação diagnóstica. Os recém-nascidos foram divididos em três grupos, de acordo com a idade do recém-nascido na ocasião da coleta: GI-n=17 (< 48h de vida), GII-n=35 (entre 48h e 7dias) e GIII-n=9 (> 7dias).

Foram estudadas 61 crianças (5,1% dos recém-nascidos de termo). A confirmação diagnóstica pela punção suprapúbica mostrou: GI=2/17 (11,8%), GII=10/35 (28,6%) e GIII=7/9 (77,7%). Quanto ao quadro clínico, nos GI e II a febre (100 e 91,4%) e a perda de peso (35,3 e 45,7%) foram os sinais clínicos mais freqüentes. No GIII as alterações do estado geral (66,6%) e a febre (44,4%) destacaram-se. Dentre os agentes etiológicos, obteve-se: E coli GI (100%), GII (40%) e GIII (28,6%), E faecalis GI (30%), S coagulase-negativa GII (20%) e GIII (42,8%) e S aureus GII (10%) e GIII(14,3%). A análise do risco relativo da positividade da cultura de urina obtida por saco coletor corresponder à infecção urinária foi de: GI=0,3 (IC95% 0,08-1,15), GII=0,51 (IC95% 0,25-1,06) e GIII=3,31 (IC95% 1,8-6,06).

Os resultados sugerem que os sinais clínicos mais importantes da infecção do trato urinário na primeira semana de vida foram a febre e a perda de peso, enquanto as alterações do estado geral ocorreram mais tardiamente; a E coli foi o agente mais freqüente e, a partir do sétimo dia, houve o aparecimento de S aureus e S coagulase negativa. A cultura de urina através de saco coletor teve maior capacidade de detecção de infecção urinária a partir do setimo dia.

DESCRITORES: Cultura de urina. Infecção urinária. Recém-nascido.

REFERENCES

1. BARKEMEYER BM. - Suprapubic aspiration in very low birth weight infants. Pediatrics 1993; 92:457-8.

2. BENADOR D, BENADOR N, SLOSMAN D et al. - Are younger children at highest risk of renal sequelae after pyelonephritis. Lancet 1997; 349:17-9.

3. BRION CP, SATLIN LM, EDELMANN CM. - Renal disease. In AVERYFLETCHER MA, MACDONALD MG, eds. - Neonatology: pathophysiology and management of the newborn. 4th ed. Philadelphia, Lippincott, 1994 p. 792-886.

4. CHIU C, LIN T & BULLARD MJ. - Identification of febrile neonates unlikely to have bacterial infections. Pediatr Infect Dis J 1997; 16:59-63.

5. HANSSON S, BRANDSTROM P, JODAL U et al. - Low bacterial counts in infants with urinary tract infection. J Pediatr 1998; 132:180-2.

6. HELLERSTEIN S. - Urinary tract infections: old and new aspects. Pediatr Clin North Am 1995; 42:1433-57.

7. HENRY JB, LANZON RB & SCHUMANN GB. - Basic examination of urine. In: Henry JB, ed. Clinical diagnosis and management by laboratory methods. 19th ed. Philadelphia, Saunders, 1996. p. 411-56.

8. HOBERMAN A, WALD ER, PENCHANSKY L et at. - Enhanced urinalysis as a screening test for urinary tract infection. Pediatrics 1993; 91:1196-8.

9. HOBERMAN A & WALD ER. - Urinary infections in young children. Pediatr Infect Dis J 1997; 16:11-7.

10. HOBERMAN A. - Is urine culture necessary to rule out urinary tract infection in young febrile children? Pediatr Infect Dis J 1996; 15:304-9.

11. JAMES-ELLISON MY, ROBERTS R, VERRIER-JONES K et al. - Mucosal immunity in the urinary tract: changes in sIgA, FSC and total IgA with age and in urinary tract infection. Clin Nephrol 1997; 48:69-78.

12. PHILLIPS JR & KARLOWICZ MG. - Prevalence of Candida species in hospital-acquired urinary tract infections in a neonatal intensive care unit. Pediatr Infect Dis J 1997; 16:190-4.

13. KIERMAN SC, PINCKERT TL & KESLER M. - Ultrasound guidance of suprapubic bladder aspiration in neonates. J Pediatr 1993; 123:789-91.

14. KLEIN JO & LONG SS. - Bacterial infections of the urinary tract. In: REMINGTON JS, KLEIN JO, eds. - Infectious diseases of the fetus and newborn. 4th ed. Philadelphia, Saunders, 1995. p. 925-34.

15. KOPELMAN BI & SILVA E. - Punção suprapúbica em recém nascidos normais. Pediatr Prát 1975; 46:87-95.

16. LOHR JA, DOWNS SM, DUDLEY S et al. - Hospital-acquired urinary tract infections in the pediatric patient: a prospective study. Pediatr Infect Dis J 1994; 13:8-12.

17. MORELLL RE, DURITZ G & OLTORF C. - Suprapubic aspiration associated with hematoma. Pediatrics 1982; 69:455.

18. POLLACK CV, POLLACK ES & ANDREW ME. - Suprapubic bladder aspiration versus urethral catheterization in ill infants: success, efficiency, and complication rates. Am Emerg Med 1994; 23:225-30.

19. VOORA S, SNIRIVASAN G, LILIEN LD et al. - Fever in full-term newborns in the first four days of life. Pediatrics 1982; 69:40-4.

20. WOODA GL. - Specimen collection and handling for diagnosis of infectious diseases. In: HENRY JB, ed. Clinical diagnosis and management by laboratory methods. 19th ed. Philadelphia, Saunders, 1996. p. 1311-34.

21. WOODS GL, AYERS LW & WASHINGTON JA. - Medical bacteriology. In: HENRY JB, ed. Clinical Diagnosis and management by laboratory methods. 19th ed. Philadelphia, Saunders, 1996. p. 1132-69.

Received for publication on the 06/06/99

Publication Dates

• Publication in this collection
  18 Apr 2000
• Date of issue
  June 1999

History

• Received
  06 June 1999