Genitourinary tract infection in children due to Aerococcus other than Aerococcus viridans. Literature review and 3 case reports

The genus Aerococcus spp. was described for the first time in 1953. It comprises eight different species, among which Aerococcus urinae and Aerococcus sanguinicola are the primary human pathogens, being associated with underlying disease in adults.¹ However, they have been reported as rare causes of infection in the paediatric population. We report clinical and microbiological characteristics corresponding to three cases.

Case 1

A 10-year-old boy visited the emergency department owing to a fever of 40 °C lasting 24 h associated with abdominal pain. Notably, he was found to have pain on palpation of his right flank, with painful fist percussion.

He had a history of admission when he was 25 days old due to a suspected febrile urinary tract infection (UTI), not confirmed microbiologically. A renal ultrasound revealed bilateral pyelocaliceal dilation. At 7 years of age, he was diagnosed with acute appendicitis. In the postoperative period, he was readmitted owing to fever and elevated acute-phase reactants, with normal urinalysis results. He was treated with piperacillin/tazobactam and responded favourably.

A urinalysis showed leukocyturia. A urine culture and blood testing revealed 14,259 leukocytes/mm³ and C-reactive protein (CRP) 22.6 mg/l. The boy was diagnosed with pyelonephritis and a decision was made to treat him with cefixime for 7 days. A renal ultrasound showed pyelocaliceal dilatation, distally tortuous right ureter and urinary retention.

Case 2

A 5-year-old boy had erythema of the urinary meatus and whitish urethral discharge, with the rest of the examination being normal. A sample of the discharge was taken for culture and treatment was started with a topical corticosteroid. He was seen by his paediatrician 21 days later due to persistent urethral discharge, with no fever. He was prescribed topical mupirocin for a week, and his symptoms remitted.

Case 3

An 8-year-old boy had colicky abdominal pain for 2 days and diarrhoeic stools. A urinalysis revealed microhaematuria, and a mid-stream urine culture was performed. He was prescribed fosfomycin tromethamine for 2 days, and his signs and symptoms disappeared. A subsequent renal ultrasound was normal.

Microbiology study

Using previously described procedures,^1,2 the urine cultures performed showed >100,000 colony-forming units (CFUs)/mL and >10,000 CFUs/mL of A. urinae for case 1 and A. sanguinicola for case 3. Abundant colonies of A. urinae alone grew in the urethral discharge culture. For the urine cultures, sensitivity to cefotaxime, ciprofloxacin, nitrofurantoin, penicillin and vancomycin was studied. For the urethral discharge culture, sensitivity to ampicillin, levofloxacin, linezolid, meropenem, rifampicin, tetracycline and vancomycin was studied. The micro-organisms were sensitive to all the antibiotics assessed.

Conclusions

Genitourinary tract sample culture enables identification of unusual micro-organisms that may present in patients with risk factors. Two of these micro-organisms, which were recently described, are A. urinae and A. sanguinicola. Infection with these micro-organisms has been widely reported as a cause of potentially serious diseases (pyelonephritis, bacteraemia, endocarditis, peritonitis, etc.) in elderly patients with urinary tract infections, immune disease or systemic disease.¹ In a review conducted in PubMed (7/2/2020), we found just 8 cases in patients 0–18 years of age (Table 1).^3–10 Among them, 6 cases featured the notable finding of extremely foul-smelling urine and two presented endocarditis. Another corresponded to a case of pyelonephritis in a patient with vesicoureteral reflux who presented abdominal pain and fever.⁸ A case of bacteraemia in a 14-year-old patient with leukaemia was also reported.⁹ Patients were mostly adolescent or pre-adolescent males and generally received a late diagnosis. Case 2 in our series is notable for being the first reported case of balanitis caused by A. urinae.

Table 1.

Infections caused by non-viridans Aerococcus in paediatric patients published in PubMed up to 7/2/2020 and 3 cases reported in our article.

Case	Age	Sex	Clinical presentation	Personal history	Urine testing	Blood testing	Diagnosis	Sample	Concomitant microbiota	Treatment	References
1	11 years	Male	Prolonged fever	Interventricular communication	Normal	Leukocytes 14,800/mm^3, CRP 156 mg/l	Endocarditis	Blood		Ceftriaxone plus vancomycin	Sous et al.^3
			Foul-smelling urine	Imperforate anus			Mycotic pulmonary aneurysm			Pulmonary lobectomy
										Penicillin G for 6 weeks
2	17 years	Male	Fever, headache, tiredness, foul-smelling urine	Obesity	LE traces	Leukocytes 9900/mm^3, CRP 125 mg/l	Bacterial endocarditis	Urine		Nitrofurantoin for 7 days	Qureshi and Patel^4
				Bicuspid aortic valve	N negative					Ampicillin plus gentamicin for 3 days
					E 2+					Penicillin plus gentamicin for 3 weeks
					Leukocytes 11−22					Penicillin for 3 weeks
3	5 years	Male	Foul-smelling urine	Bladder diverticulum	50-70 leukocytes/field		Cystitis	Urine		Amoxicillin/clavulanic acid for 10 days	Skalidis et al.^5
4	12 years	Male	Foul-smelling urine		187−275 leukocytes		Cystitis	Urine	Corynebacterium, Actinomices neuii, Veillonella, Bacteroides fragilis	Amoxicillin/clavulanic acid for 10 days	Lenherr et al.^6
5	11 years	Male	Foul-smelling urine			Normal	Cystitis	Urine		Penicillin	Gibb and Sivaraman^7
6	7 years	Male	Foul-smelling urine		LE and N negative		Cystitis	Urine		Trimethoprim/sulfamethoxazole	De Vries and Brandenburg^8
7	12 years	Male	Fever (39.5 °C), pain in RF, vomiting and diarrhoea	Bilateral JGO	LE 4+	Leukocytes 15,300/mm^3	Pyelonephritis	Urine		Ampicillin/sulbactam for 2 days	Murray et al.^9
				Grade 4 left VUR	N negative	Erythrocyte sedimentation rate (ESR) 34 mm/h				Cefazolin for 5 days
				Pyeloplasty	E 4+					Cefalexin for 7 days
8	14 years	Male	Fever 38.1 °C	Acute myeloid leukaemia		Leukocytes 800/mm^3	Bacteraemia	Blood		Ceftriaxone	Colakoglu et al.^10
				Leukopenia		CRP 96 mg/l
9	10 years	Male	Fever 40 °C, pain in RF	Recurrent UTI	LE 2+	Leukocytes 14,590/mm^3	Pyelonephritis	Urine		Cefixime for 7 days	Our case
					N negative	CRP 22.6 mg/l
10	5 years	Male	Erythema and urinary meatus discharge				Balanitis	Urethral discharge		Topical mupirocin for 7 days	Our case
11	8 years	Male	Abdominal pain, dysuria, diarrhoea		E 2+		Cystitis	Urine		Fosfomycin tromethamine	Our case

CRP: C-reactive protein; E: erythrocytes; JGO: juxtaglomerular obstruction; LE: leukocyte esterase; N: nitrites; RF: right flank; VUR: vesicoureteral reflux.

These micro-organisms are difficult to identify by conventional methods since they are easily mistaken for Enterococcus or Streptococcus viridans, Abiotrophia defectiva, Lactococcus, Leuconostoc, or Pediococcus. Furthermore, urine cultures often yield false negatives since these are slow-growing, nutritionally demanding, facultative anaerobic bacteria that usually grow with CO₂. Proper identification requires an experienced microbiologist.^1,2 At present, MALDI-TOF mass spectrometry is being used to help identify these pathogens.

In conclusion, A. urinae and A. sanguinicola are uncommon, difficult-to-identify micro-organisms that cause genitourinary infections in paediatric patients and are probably underdiagnosed. Studying their epidemiology, signs and association with underlying disease in the paediatric population will enable the relationship to the prognosis to be established and suitable treatments to be selected.