An 18-month-old Japanese boy with rapid onset high fever for the previous 12 hours presented to our emergency room. His perinatal and family history was unremarkable. There was no record of previous immunological problems.
At 10 months of age, he was admitted to our hospital for examination owing to a fever of above 39°C, lasting for two days, for an unknown reason. Laboratory examinations revealed leukocytosis (white blood cell (WBC) counts: 20,410/μL), high absolute neutrophil counts (ANCs: 10,880/μL), and high levels of C-reactive protein (CRP: 6.39mg/dL). Although his urine analysis did not reveal pyuria, contrast-enhanced computed tomography revealed that a part of his left renal parenchyma showed decreased contrast enhancement, indicating pyelonephritis, which was also observed in the right small kidney and compensatory hypertrophic left kidney (Figure 1). He was thus diagnosed with pyelonephritis, and empirically treated with intravenous ceftriaxone (100mg/kg-1/day-1 at 24-hour intervals). Subsequently, a culture of urine obtained through catheterization revealed the presence of Enterococcus faecalis, which was susceptible to penicillins (Table 1). The urine was cultured, incubated on blood agar plates and bromothymol blue lactate agar plates at 37°C for species identification, and evaluated by slide culture for quantification of the organism. Moreover, we assessed the antimicrobial susceptibility of the isolate according to the Clinical and Laboratory Standards Institute criteria. The treatment was then changed to oral amoxicillin (60mg/kg-1/day-1 in three doses). He completed a three-week course of treatment and his symptoms were promptly resolved.At 12 months of age, we performed a voiding cystourethrography, which showed severe bilateral VUR (right side grade V, left side grade III; Figure 2). Therefore, he was started on CAP with prophylactic-dose trimethoprim/sulfamethoxazole (TMP/SMX: 2mg/kg TMP and 10mg/kg SMX per day in one single dose); he did not develop recurrent UTIs for the next six months.
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When he presented to our hospital again at 18 months of age, his body temperature was 39°C. Other clinical examination findings were unremarkable. He had severe phimosis. The only abnormal laboratory findings were leukocytosis (WBC counts: 14,460/μL) and high ANCs (10,450/μL), but CRP levels were only slightly elevated (1.81mg/dL). The urine analysis revealed five to nine WBCs per high-power field and a remarkably elevated level of β2 microglobulin (1,490μg/L). Gram staining of urine obtained through catheterization revealed gram-positive cocci. While considering sample contamination, we also suspected pyelonephritis because there was no apparent source of the fever, and the urine sample was obtained by catheterization with a proper procedure. Moreover, during a routine examination two weeks prior, his urine analysis showed less than five WBCs per high-power field, despite the fact that it was bag-collected, and the β2 microglobulin level was within the normal range (195μg/L).
Since his clinical condition was generally good despite the high fever and he was not dehydrated, we determined that oral antibiotic treatment was possible. We planned to administer oral ampicillin after collecting blood and urine cultures, but we abandoned the treatment plan as he came to dislike the taste of oral amoxicillin subsequent to the prescription at first pyelonephritis at 10 months of age. Therefore, we selected tosufloxacin (oral fluoroquinolone, 12mg/kg-1/day-1 in two doses). The fever promptly declined one day after antibiotic therapy was started. After two days, we performed repeated blood examinations, which showed elevated CRP and WBC levels (12.2mg/dL and 16,140/μL, respectively), but significantly decreased ANCs levels (6,843/μL). In addition, we obtained a positive urine culture result indicating the presence of methicillin-resistant S. epidermidis (107 colony-forming units per milliliter) as single bacterial species; the blood culture was negative for any bacterial organisms. Thus, our final diagnosis was pyelonephritis caused by community-acquired methicillin-resistant S. epidermidis, and, based on the result of the antibiotic susceptibility test, the antibiotics were adjusted to ‘therapeutic-dose’ TMP/SMX (10mg/kg TMP and 50mg/kg SMX per day in two doses; Table 1). The total antibiotic treatment duration was two weeks, and his fever did not reoccur. Because he had severe bilateral VUR and developed recurrent pyelonephritis despite receiving CAP, antireflux surgery was performed at 20 months of age. He has not had a reoccurrence of pyelonephritis to date.
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