Hearing impairment and its predictors in childhood bacterial meningitis in Angola

Gene polymorphisms of IL-17A and bacterial meningitis in Angolan children

Interleukin (IL)-17 A plays a crucial role in protecting hosts from invading bacterial pathogens. In this study, we investigated if single nucleotide polymorphisms (SNPs) in IL-17A are associated with susceptibility and outcome of bacterial meningitis (BM) in Angolan children. The study sample comprised 241 confirmed BM patients and 265 controls, which were matched for age and ethnicity. Three IL-17A SNPs - rs2275913 (-197G > A), rs8193036 (-737C > T) and rs4711998 (-877 A > G) - were determined by high-resolution melting analysis (HRMA). The frequency of variant genotype rs4711998 was significantly higher in patients with BM caused by Haemophilus influenzae (odds ratio [OR] 3.5; 95% confidence interval [CI] 1.49-8.23; P = 0.0025) than in controls. Also, patients with BM caused by Gram-negative bacteria and who carried the variant genotype rs2275913 had a lower glucose level (P = 0.0051) in cerebrospinal fluid (CSF). Patients with BM caused by Streptococcus pneumoniae who carried the variant type rs8193036 had a reduced risk for severe neurological sequelae (OR: 0.14; 95% CI: 0.029-0.68; P = 0.0079), blindness (OR: 0.012; 95% CI: 0.012-0.87; P = 0.017) and ataxia (OR: 0.28; 95% CI: 0.091-0.83; P = 0.023). This study suggests an association of IL-17A genetic variations with susceptibility and outcome of bacterial meningitis in Angolan children.

Auditory Steady-State Response and Hearing Impairment in Survivors of Childhood Bacterial Meningitis in Luanda, Angola

Survivors of childhood bacterial meningitis (BM) often develop hearing impairment (HI). In low- and middle-income countries (LMICs), BM continues to be a significant cause of hearing disability. We assessed hearing among BM survivors using auditory steady-state responses (ASSR), providing frequency-specific estimated audiograms, and examined whether ASSR would provide a greater understanding of BM-induced HI. Survivors from two prospective BM trials (ISRCTN62824827; NCT01540838) from Luanda Children's Hospital were examined in a follow-up visit with a median duration of 26 months after BM. The hearing of 50 BM survivors and 19 control children was evaluated using ASSR and auditory brainstem response (ABR) after interview and neurological and otorhinolaryngological examinations. The median age of survivors was 80 (IQR 86) months. We diagnosed HI (better ear hearing ≥ 26 dB) in 9/50 (18%) children. Five of the fifty survivors (10%) and 14/100 ears (14%) had profound HI (>80 dB). Severe-to-profound HI affected all frequencies steadily, affecting only the ears of BM survivors (18/100 vs. 0/38, p = 0.003). When looking only at the severely or profoundly affected ears, young age, low Glascow coma score, pneumococcal aetiology, and ataxia were associated with a worse hearing outcome.

Hearing impairment in Angolan children with acute bacterial meningitis with and without otitis media

AIM

Bacterial meningitis (BM) is a common cause of hearing loss in childhood. Our aim was to investigate bacterial aetiology, hearing impairment and outcome in childhood BM with vs. without otitis media (OM) in Angola.

METHODS

Hearing was tested by auditory brainstem response in 391 (76%) children with confirmed BM. The bacteria identified from the ear discharge were compared to those from cerebrospinal fluid (CSF). The hearing findings were compared among children with vs. without OM on days 1 and 7 of hospitalization, and at follow-ups of 1, 3 and 6 month(s).

RESULTS

No correlation was found in bacteriology between the ear discharge and CSF. On day 7 in hospital, hearing impairment (>40 dB) was common, regardless of whether concomitant OM or not (in 27% vs. 30%, respectively). Any hearing deficit on day 7 was associated with a higher risk of complicated or fatal clinical course (OR 2.76, CI_95% 1.43-5.29, p = 0.002).

CONCLUSION

No significant difference prevailed in hearing thresholds between children with or without OM in hospital on day 7 or at later follow-ups. Any hearing impairment during hospital stay associated with a higher risk for complicated clinical course or death.

Risk Factors in Predicting Prognosis of Neonatal Bacterial Meningitis-A Systematic Review

Background: Neonatal bacterial meningitis is a severe infection with high mortality and morbidity. It is necessary to identify factors associated with a high risk of a poor prognosis so that we can prevent them with more appropriate treatments. This study was performed to summarize the prognostic factors known to predict adverse outcomes in neonatal bacterial meningitis.

Methods: The Medline/PubMed, Cochrane Library and Embase databases were searched for studies of prognostic risk factors in neonates with bacterial meningitis. Studies published from the initiation of the database to April 30th, 2017 were included. The quality of cohort studies was assessed by the Newcastle-Ottawa Scale (NOS). The quality of cross-section studies was assessed by the Agency for Healthcare Research and Quality (AHRQ) scale. Each prognostic factor known to cause adverse outcomes is summarized.

Results: Sixteen studies were identified, including 7 cohort studies and 9 cross section studies. Seizure and high protein levels in the cerebrospinal fluid (CSF) predict a poor prognosis in this disease. Coma, the need for ventilation support, and leukopenia also had some value for predicting poor prognoses. A bulging anterior fontanelle was valuable for predicting mortality. Low CSF glucose levels, thrombocytopenia, gestational age (GA) < 37 weeks and an altered sensorium were correlated with a poor prognosis. A birth weight < 2500 g, early onset meningitis and positive CSF cultures were correlated with mortality.

Conclusions: This study provides a preliminary exploration of prognostic factors in neonatal bacterial meningitis and thereby fills some of the gaps in the study of prognoses in this disease. These prognostic factors can be used to predict and estimate outcomes in neonatal bacterial meningitis. Without a meta-analysis, the reliability of these factors cannot be assured. In addition, these results emphasize that there is an urgent need for a standardized protocol for follow-up and well-designed prognostic studies in neonatal bacterial meningitis.

The Severity of Infection Determines the Localization of Damage and Extent of Sensorineural Hearing Loss in Experimental Pneumococcal Meningitis

Hearing loss is an important sequela of pneumococcal meningitis (PM), occurring in up to 30% of survivors. The role of the severity of infection on hearing function and pathomorphological consequences in the cochlea secondary to PM have not been investigated to date. Using a well-established model of PM, we systematically investigated the functional hearing outcome and the long-term fate of neurosensory cells in the cochlea, i.e., hair cells and spiral ganglion neurons (SGNs), with a focus on their tonotopic distribution. Intracisternal infection of infant rats with increasing inocula of Streptococcus pneumoniae resulted in a dose-dependent increase in CSF levels of interleukin-1β, interleukin-6, tumor necrosis factor α, interleukin-10, and interferon-γ in acute disease. The severity of long-term hearing loss at 3 weeks after infection, measured by auditory brainstem response recordings, correlated to the initial inoculum dose and to the levels of proinflammatory cytokines determined in the acute phase of PM. Quantitative cochlear histomorphology revealed a significant loss of SGNs and outer hair cells that strongly correlated to the level of infection, with the most severe damage occurring in the basal part of the cochlea. Inner hair cells (IHCs) were not significantly affected throughout the entire cochlea. However, surviving IHCs lost synaptic connectivity to remaining SGNs in all cochlear regions. These findings provide evidence that the inoculum concentration, i.e., severity of infection, is the major determinant of long-term morphological cell pathologies in the cochlea and functional hearing loss.

SIGNIFICANCE STATEMENT

Hearing loss is a neurofunctional deficit occurring in up to 30% of patients surviving pneumococcal meningitis (PM). Here, we analyze the correlation between the severity of infection and the inflammatory response in the CSF, the tonotopic distribution of neurosensory pathologies in the cochlea, and the long-term hearing function in a rat model of pneumococcal meningitis. Our study identifies the severity of infection as the key determinant of long-term hearing loss, underlining the importance of the prompt institution of antibiotic therapy in patients suffering from PM. Furthermore, our findings reveal in detail the spatial loss of cochlear neurosensory cells, providing new insights into the pathogenesis of meningitis-associated hearing loss that reveal new starting points for the development of otoprotective therapies.

Ataxia and Its Association with Hearing Impairment in Childhood Bacterial Meningitis

INTRODUCTION

Ataxia, deemed usually a minor sequela, follows childhood bacterial meningitis (BM) in up to 18% of cases. Although mostly transient and benign, it can predict permanent hearing loss and vestibular dysfunction. We explored the clinical meaning of ataxia by following its course in a large number of BM patients and examining its relation with hearing loss.

METHODS

The presence, degree (no, mild, moderate and severe) and course (transient, prolonged and late) of ataxia in BM were registered prospectively by predefined criteria. These data were compared with several patient, disease, and outcome variables including hearing loss (none, moderate, severe and profound) on day 7 of treatment and at a follow-up visit 1 month after discharge.

RESULTS

Ataxia was present in 243 of 361 (67%) patients on day 7, being slight in 21%, moderate in 38% and severe in 41%. Its course was transient in 41%, prolonged in 24% and late in 5%, whereas 30% of the patients did not present ataxia at any time. Ataxia associated most significantly not only with several measures of BM severity and suboptimal outcome (P < 0.0001), but also specifically, albeit not consistently, with hearing loss (P = 0.001). The degree of ataxia correlated with the extent of hearing loss (rho, 0.37; P < 0.0001).

CONCLUSIONS

Ataxia is more frequent and lasts longer after BM than learned from previous studies. The presence and intensity of ataxia associate with hearing loss and its magnitude.

Fluctuation in hearing thresholds during recovery from childhood bacterial meningitis

BACKGROUND

Hearing loss from childhood bacterial meningitis is believed to develop early and have little tendency for recovery. We performed serial hearing evaluations in a large number of children with bacterial meningitis in Luanda, Angola to clarify if, and how often, the result changed.

METHODS

Children with confirmed bacterial meningitis and hearing evaluations on admission, day 7 of treatment and the follow-up visit formed the study group. Hearing was tested by auditory brainstem response audiometry using stimuli of 40 dB, 60 dB and 80 dB. Threshold changes are described between the composite levels of 40/60 dB and 80/>80 dB.

RESULTS

In all, 235 ears were tested. While the ≤ 60 dB and ≥ 80 dB levels were maintained through all 3 examinations in 54% and 5% of ears, respectively, changes occurred in 41%. Deterioration from the ≤ 60 dB level to ≥ 80 dB was found in 10% of the ears transiently and in 7% permanently. Improvement from the ≥ 80 dB level to ≤ 60 dB occurred in 22% of the ears. Half of the ears with ≥ 80 dB impairment at the follow-up visit arrived with this finding; the others lost hearing later. Maintaining the ≤ 60 dB level throughout was associated with milder disease (P = 0.003), fewer convulsions (P < 0.0001) and older age (P = 0.009).

CONCLUSIONS

Almost half of the ears showed threshold changes after admission during recovery from bacterial meningitis, most frequently improvement of initially severely impaired hearing, but some normal ears or with moderate impairment became severely impaired.