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Encapsulated pleural effusion due to Haemophilus influenzae biotype II in a child with trisomy 21: A case report and literature review

Highlights • This is the second case report of pediatric encapsulated pleural effusion (EPE) due to Haemophilus influenzae.• We represent typical images of chest X-P, CT, echography to find the EPE.• Nontypeable H. influenzae was isolated from the throat after the discharge.


Introduction
Haemophilus influenzae (Hi) including the capsule type b (Hib) occasionally colonize the upper respiratory tract and can cause severe pulmonary infections and meningitis among infants and preschool children. Therefore, Hib vaccination has been introduced to the children, and its preventive intervention is very popular in Japan. Okada et al. [1] reported the radiological findings using thin-section computed tomography (CT) scans in acute pulmonary infections due solely to Hi, which was extracted from 211 patients in Japan. The main CT features were ground-glass opacity (n = 185, 87.7%), bronchial wall thickening (n = 181, 85.8%), centrilobular nodules (n = 137, 64.9%), and consolidation (n = 112, 53.1%); however, pleural effusion (PE) was found in 22 (10.4%) patients. Thus, PE involvement is uncommon.
Encapsulated PE (EPE) is confirmed as an extrapleural sign formed on the chest roentgenogram, and this sign is not changed between standing and lateral decubitus positions, in which the roentgenograms are taken. This situation might be induced by the fibrous adhesion between the parietal and visceral pleura.
Herein, an EPE formed in the left pleural space due to Hi in a 24month-old girl with trisomy 21 was described. In addition, a literature review regarding Hi-related EPE in pediatric patients was also presented.

Case report
A 24-month-old Japanese girl, who was previously diagnosed with trisomy 21, was admitted to our hospital because of high fever and shortness of breath. Her past medical history revealed that she had repetitive lower respiratory tract infections (bronchiolitis or pneumonia) and post-cardiac repair operation for ventricular septal defect. She was already vaccinated against Hib. The patient had been ill with high fever and cold-like symptoms for 4 days before the emergent admission. Physical examinations revealed cyanosis and chest retraction when breathing, tachycardia (150 beats/min), tachypnea (53 breaths/ min), and high fever (body temperature 39.4°C).
Blood laboratory tests showed leukocytosis (28,700/μL), elevated Creactive protein levels (17.75 mg/dL), and hypoxemia. Chest roentgenogram indicated lobar consolidation with a small amount of PE on the left lung. On hospital day 2, both the aspirated sputum and blood cultures yielded the growth of Hi. After starting an intravenous administration of 180 mg/kg/day ampicillin/sulbactam (ABPC/SBT) and oxygen supplementation combined with β-stimulant inhalation, her general conditions ameliorated within the next 2 days. On hospital day 4, although the percutaneous oxygen saturation was improved, the left vesicular sound was poorly auscultated and inflammatory blood markers still remained high. On hospital day 6, chest roentgenogram ( Fig. 1A) and CT (Fig. 1B) showed remarkable EPE formed in the left pleural space.
She was immediately transferred to a tertiary hospital for further management of the EPE. Percutaneous needle aspiration was performed using an echography of the left chest wall (Fig. 1C), and a small amount of fluid was aspirated. Laboratory tests on the fluid revealed white cell count of 800/μL (not suggesting high-levels of inflammation in EPE), lactate dehydrogenase (LDH) level of 488 IU/L, and glucose (Glu) concentration of 4 mg/dL. The Gram-staining and culture results were both negative. Based on these data, we decided no performance of the chest tube placement to improve the EPE. Investigation regarding the immune system was done, and the serum levels of immunoglobulin G (IgG), IgA, and IgM were found to be 1197 mg/dL, 117 mg/dL, and 152 mg/dL, respectively. We considered the potential contribution of polymicrobial anaerobic pathogens to the EPE, and continued to intravenously administer ABPC/SBT (180 mg/kg/day) as the use of antianaerobic antibiotic. Thickening of the chest wall appeared to be due to local fibrinolysis, which might be induced by Hi-related inflammation. After continuously administering intravenous ABPC/SBT with the same dose for 1 month, the EPE disappeared. She had no EPE relapse during the 5-month follow-up period after discharge.

Microbiological analyses
Upon the emergent admission, blood and aspirated sputum specimens were immediately obtained to identify the causative microorganisms. Then, Gram-negative bacilli were isolated from the blood culture bottles, and both of the blood and sputum cultures yielded small gray/white-colored colony formations on the chocolate agar plate, but not on the sheep blood agar plate, which were incubated in a 5% CO 2 atmosphere at 37°C for 24 h. These isolates required both the X (hemin) and V factors (nicotinamide adenine dinucleotide) for their growth. These characteristics were compatible with the biochemical properties of Hi. The blood-origin isolate was accurately identified using a commercially available manual identification kit (ID-test HN-20 rapid, Nissui Pharmaceutical Co., Ltd., Tokyo, Japan), and its profile No. was 7501040 (% probability, 100%). The Hi species has routinely been subdivided into eight biotypes (I-VIII) based on the combined properties of urease production, ornithine decarboxylase activities, and indole production [2,3], and these isolates were biotype II. Antimicrobial susceptibility testing was performed using the broth microdilution method (Dry plate Eiken DP34, Eiken Chemical Co., Ltd., Tokyo, Japan), and both isolates were β-lactamase-negative ampicillinsusceptible (BLNAS) strain.
To determine the capsular type, the throat swab was cultured 1 month after discharge, because the patient developed mild infection (acute otitis media [AOM]) of the upper respiratory tract again. This Hi isolate from the throat swab indicated the profile No. 7501040, biotype II, and antimicrobial susceptibility result of BLNAS, which were identical to those in the blood-origin isolate. The polymerase chain reactionbased amplification of several genes (bexA, bexB, and acs-fcs) was performed in regions I and II of the capsule locus with the amplification of pepN (a DNA-positive control) as previously described [4,5], and this isolate was a nontypeable Hi (NTHi). However, it still remained unclear whether or not this NTHi isolate from the throat was the same genetic lineage to the blood-origin isolate. Her infection was controlled by an oral administration of antimicrobials. Table 1 summarizes the literature review regarding the EPE caused by Hi in children [6]. A 6-month-old boy with Hib pneumonia followed by EPE received thoracic drainage for 8 days, and then, he clinically recovered [6]. On the other hand, our case was treated using an antimicrobial treatment alone without performing the thoracic drainage. Richard WL [7] described that parapneumonic PE and pleural empyema could be divided into classes 1-7 based on the pH, Glu concentration, LDH level, Gram-staining, and effusion culture data. When either the pH of < 7.0, Glu concentration of < 40 mg/dL, positive staining/ culture, or the presence of empyema was observed, invasive procedures (i.e., thoracic drainage or de-capsulation using the video-assisted thoracoscopic surgery) should be recommended. Whether or not these invasive procedures should be performed in a large number of pediatric patients with EPE remains to be evaluated. Table 2 shows the yearly prevalence of various Hi biotypes (2011-2017), which were isolated at our hospital. These strains were isolated mainly (97.9%) from the upper and lower respiratory tract samples of all clinical specimens. Biotypes II (48.8%) and III (32.2%) followed by I (9.6%) were prevalent, whereas biotype VIII were not observed in this study. Another Japanese study results [1] were consistent with our findings that the prevalent types III (48.9%) and II (45.6%) followed by I (3.3%) were isolated from the lower respiratory tract and caused acute pulmonary infections. In a previous study conducted in Iran [3], types II (42.1%), I (18.4%), and III (15.8%) were well known, while types VI and VII were not found. A Japanese study concerning the capsular types of Hi isolates from pediatric patients with respiratory tract infections showed that all encapsulated strains (types b and f) displayed biotype I [8]. Of the 30 Hib isolates from the cerebrospinal fluid of Japanese children with meningitis, 22 (73.3%) were characterized as biotype I [9]. Thus, this biochemical phenotypic assay is useful to assess the prevalent type of Hi based on the data combined with the capsular genotypes.

Discussion
In our case, the NTHi strain with biochemical properties (No. 7501040 and biotype II) and BLNAS result, which were both identical to those in the invasive isolate during the hospitalization, was isolated from the throat, since she developed AOM 1 month after discharge. However, it still remained unclear whether or not this NTHi isolate from the throat was the same genetic lineage to the blood-origin isolate. As most of the systemic Hi infections among children are caused by the Hib, NTHi is also considered as one of the respiratory tract pathogens common in local infections (AOM, pneumonia, acute exacerbation of chronic respiratory disease, and other otorhinolaryngologic infections) [10]. Furthermore, this NTHi strain can cause severe invasive diseases, including meningitis and bacteremia in a healthy child [11] as well as in an immunocompromised host. A review of literature on the Hi epidemiology from the 1990s onward indicates that NTHi induces significant morbidity in pediatric AOM, sinusitis, conjunctivitis, and lower respiratory tract infections in Japan [10]. In fact, 118 (96.7%) NTHi strains were found among 122 tested isolates from pediatric patients with respiratory tract infections [8]. Moriyama et al. [12] demonstrated a biofilm formation of clinical NTHi isolates from AOM children, suggesting that the biofilm production plays an important role in persistent or intractable clinical course of AOM. However, invasive NTHi isolates are genetically and phenotypically diverse, and certain genetic loci are frequently associated with NTHi strains [13,14]. Thus, further investigations should be conducted to clarify the virulent factors shared among the invasive NTHi isolates, because preventing severe invasive diseases due to NTHi strains is difficult.

Conclusions
Pediatric clinicians should be aware of the possibility of Hi-related EPE because of its rapid progression, although it is rare in clinical settings. In addition, they need to consider the possibility of repetitive respiratory infections with Hi in a child with trisomy 21.

Informed consent
The patient's parents gave their informed consent before this article was written.

Conflicts of interest
The authors have disclosed no relevant financial relationships. Capsular type was not determined, because those from the blood and sputum during hospitalization were not stored.

Ethical approval
Ethical approval was not required for this study.