Group B Streptococcus Meningitis Associated with Acute Otitis Media in an Adult Patient

Background

Group B Streptococcus is one of the most common causes of sepsis and meningitis in neonates and is a major cause of concern during the postpartum period. However, the incidence of invasive GBS infection in non-pregnant adults is also increasing in the United States. The incidence of GBS meningitis in adults is still rare. Invasive GBS infection in adults is commonly associated with other comorbidities or concurrent infections elsewhere in the body [1]. Here, we present the case of a non-pregnant woman who developed a GBS meningitis preceded by several days of ear infection, leading to bacteremia.

Case Report

Our patient was a 55-year-old obese woman with a history of juvenile rheumatoid arthritis who presented to the hospital with acute metabolic encephalopathy. Before admission, she had been undergoing treatment for right-sided acute otitis media and right middle-ear effusion through her primary care provider and ENT specialist for the past 3 weeks. Her treatment included a trial of doxycycline and steroids. There was a tentative plan for a tympanoplasty if her tympanic ef-fusion remained. Despite treatment, her effusion remained. About 2 days before presentation, the patient started developing severe right-sided headaches with associated nausea and emesis. While these symptoms persisted, her mentation worsened and she became increasingly confused, prompting her husband to bring her to the hospital.

At presentation to the hospital Emergency Department (ED), the patient appeared acutely ill, with altered mental status. She was unable to coherently provide a history. On examination, she had a significant amount of right-ear tympanic bulging and effusion but she did not have any meningismus. She was otherwise afebrile, without leukocytosis on laboratory testing and with an unremarkable CT head scan. She rapidly deteriorated, with acute respiratory failure and required emergent intubation.

The patient was started on empiric antibiotics (vancomycin 1.5 g Q8h and ceftriaxone 1g q12h.) She became febrile with marked leukocytosis. A maxillofacial MRI revealed significant fluid in the right mastoid and right middle ear, which was suggestive of acute otitis media and mastoiditis. An ear, nose, and throat (ENT) specialist performed emergent tympanoplasty with tube placement and the patient was then started on systemic steroids. A lumbar puncture was done and revealed profound leukocytosis with a WBC count of 12 815/cmm. CSF glucose was low at 39 mg/dl and CSF protein was elevated at 564 mg/dl. Blood cultures grew GBS but no other pathogens. Cultures from the CSF and the middle-ear fluid drawn during the tympanoplasty did not have any growth, as the patient had been on 1 day of antibiotics by then. However, CSF PCR performed with a BioFire® FilmArray® Meningitis/Encephalitis Panel kit confirmed the presence of GBS.

In response, her antibiotics were adjusted to a high dose (ceftriaxone 2 g i.v. q12). On day 4 of her ICU stay, she was noted to have myoclonic activity in her right arm. A follow-up MRI brain revealed a 1.5-cm foci of diffusion restriction with increased FLAIR signal in the parasagittal left frontal lobe on axial DWI (Figure 1) along with multiple additional small foci of diffusion restriction (<5 mm) scattered throughout the cortex, raising concerns for cerebritis. She completed 2 weeks of high-dose intravenous ceftriaxone, with full neurological recovery. The infectious disease physician signed off at that point. However, without the knowledge of the infectious disease consultant, ENT started the patient again on doxycycline before discharge. This highlights the importance of educating other specialities in appropriate antibiotic selection.

Discussion

Group B Streptococcus (Streptococcus agalactiae) is an encapsulated gram-positive, beta hemolytic, catalase negative, facultative anaerobe that is commensal with humans. This bacterium has a tendency to colonize tissues such as the gastrointestinal, respiratory, and vaginal tracts and it is believed that about 15–40% of all women have vaginal colonization [2]. Despite its widespread presence, it most commonly presents as a less serious non-invasive disease such as asymptomatic bacteriuria. However, GBS is a major pathogen causing neonatal sepsis meningitis and peripartum infection [3].

Studies suggest the incidence of invasive GBS infection in non-pregnant adults is rising in the USA. From 2008 to 2016, Watkins et al performed an epidemiologic study evaluating invasive GBS infection in the USA, finding an increasing incidence, from 8.1% in 2008 to 10.9% in 2016 (P=0.002 for trend). What was particularly striking is that many positive cases in 2016 also were associated with either obesity or diabetes [4]. An epidemiological study by Schwartz et al also found a nearly 10-fold higher risk of invasive GBS in diabetics [1]. It appears that more investigation in defining individuals at risk of invasive GBS may be important in the future as the obesity and diabetes epidemics continue to progress in the United States. There is already a suggestion that African American communities may be at higher risk [1,5].

In regards to CNS infection, the incidence of Group B Streptococcus meningitis in adults appears to be exceptionally low and incidence data are very limited in the USA. Van Kessel et al calculated an incidence rate of about 0.16 per 1 million adults based on 33 cohort studies done in the Netherlands [6]. Previous epidemiological studies in the USA have suggested that CNS involvement occurs in around 1.6% of all cases of invasive GBS infection for both children (non-neonatal) and adults [7]. In their population study, Farley et al reported that out of 137 non-pregnant adult patients with invasive GBS infection detected in Atlanta GA, only 5 presented with meningitis (3.7%) [5]. Jackson et al reported 8 cases of GBS meningitis out of a total of 219 observed invasive GBS infections (8%) [8]. These studies suggest that patients who are immunocompromised, elderly, diabetic, or with endocarditis are at particular risk of GBS meningitis [6,9,10]. A large outbreak of GBS meningitis in Asia was reported after consumption of raw fish [11].

Presentation of GBS meningitis is clinically very similar to other forms of bacterial meningitides. Empiric antibiotics for the coverage of more common bacterial pathogens such as Neisseria meningitidis and Streptococcus pneumoniae include third-generation cephalosporins, which typically are used to treat GBS infection. Mortality rates based on previous literature reviews suggest the fatality rate may be as high as 30% [9,10]. Risk of mortality has been correlated with advanced age and immunocompromised state [7].

Conclusions

Incidence of Invasive Group B Streptococcus (Streptococcus agalactiae) infection in non-pregnant adults may be increasing in the United States with the growing elderly and diabetic populations. Fortunately, GBS meningitis in non-pregnant adults is still rare.