Granulicatella adiacens as an Unusual Cause of Empyema: A Case Report and Review of Literature.

Granulicatella adiacens , a nutritionally variant Streptococcus (NVS), is part of the normal commensal flora of human mouth, genital, and intestinal tracts and rarely causes disease. It has been mostly reported from bacteremia and endocarditis cases, but rarely can cause vertebral osteomyelitis, pancreatic abscess, otitis media, and endovascular, central nervous system, ocular, oral, bone and joint, and genitourinary infections. Due to requirement of fastidious culture conditions and non-specific colony morphology, serious diagnostic difficulties may arise in cases of NVS infections. Here, we are reporting a rare fatal infection of G. adiacens presented with empyema complicated to sepsis and necrotizing fasciitis. Clinicians should be aware of the pathogenic potential of Granulicatella adiacens (a normal commensal flora of human mouth, genital and intestinal tracts). Appropriate supplemented media and a reliable detection system should be used to identify these fastidious organisms. We present this rare case to bring awareness among clinicians regarding such a rare but potentially fatal infection. The Indian Association of Laboratory Physicians. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. ( https://creativecommons.org/licenses/by-nc-nd/4.0/ ).

Introduction

Granulicatella adiacens is a nutritionally variant Streptococcus (NVS). Pyridoxine or other additional agents supplementation into standard media is required for its laboratory isolation. 1 Taxonomically, these bacteria were transferred from Streptococcus to a separate genus Abiotrophia 2 and later, on the basis of 16S rRNA gene sequencing this genus was divided into the genera Abiotrophia and Granulicatella (species Granulicatella adiacens , G. elegans , and G. balaenopterae ). 3

Granulicatella is part of the normal commensal flora of human mouth, genital and intestinal tracts and rarely causes disease. Granulicatella adiacens has been mostly reported to cause bacteremia and endocarditis, but rarely can cause vertebral osteomyelitis, pancreatic abscess, otitis media and endovascular, central nervous system, ocular, oral, bone and joint and genitourinary infections. 4

Infections due to nutritionally variant Streptococcus may have a high mortality rate because of difficulties in robust and reliable diagnosis and therapeutic failures. In a recent survey, mortality rate in nutritionally variant Streptococcus infections was found to be 9.0%. 5 For treatment of Abiotrophia and Granulicatella endocarditis and other serious infections, penicillin or ceftriaxone is the drug of choice as per the American Heart Association (AHA) guidelines. 6 Through this article, we present a review and our experience of a rare case of empyema caused due to G. adiacens complicated to sepsis and necrotizing fasciitis and ultimately death.

Materials and Methods

Case History

A 68-year-old male patient presented with left side chest pain and pain in lower limbs to the emergency department. On examination, the body temperature was 38.5°C, blood pressure 78/50 mm Hg, and pulse rate was 93/min. On chest examination, heart sounds were normal but respiratory rate was 28/min, vesicular breath sound and crepitations were present in the left chest. He was a known case of type 2 diabetes mellitus, hypertension and osteoarthritis of knee joints. He was alcoholic. Chest X-ray showed left-sided encysted pleural effusion. The patient was diagnosed with left-sided empyema with ruptured baker's cyst and septic shock. On ultrasound-guided aspiration, thick pus was aspirated and sent for biochemical analysis, bacteriological culture and sensitivity, Ziehl–Neelsen stain and CBNAAT (Cartridge-based nucleic acid amplification test). Simultaneously, one set of blood (BACT/ALERT FA Plus and BACT/ALERT FN Plus) and urine samples were sent for bacteriological culture. The patient was diagnosed as a case of left-sided empyema with septic shock and transferred to the ICU for management. Intercostal chest tube was placed and fluid was drained. The patient was managed with intravenous saline infusion and empirical antibiotic (inj. cefuroxime) was started. Laboratory findings showed an increased total leukocyte count (18,580/mm 3 ), absolute neutrophil count (17,290 mm 3 ), increased C-reactive protein (CRP 11.2 mg/dL), and hemoglobin level was 11.2 g/dL. Fasting blood sugar was 201 g/dL and serum uric acid was 8.9 mg/dL. Kidney function test was also deranged with serum urea level 102 mg/dL and creatinine 1.2 mg/dL. Pleural pus grew minute colonies on sheep blood agar after 48 hours, which were gram-positive cocci in small chains, catalase-negative, and subsequently identified as Granulicatella adiacens using the VITEK2 system (bioMérieux, France) using Gram positive (GP) identification card with 98% probability index. Antimicrobial susceptibility was performed using the E-test method (HiMedia, Mumbai, India) and MICs in µg were reported according to the EUCAST Clinical Breakpoints. 7 The isolate was sensitive to benzylpenicillin (MIC: 0.002 μ gm/ml), ampicillin (0.016 μ gm/ml), ampicillin sulbactam (0.016 μ gm/ml), ceftriaxone (0.002 μ gm/ml), teicoplanin (0.016 μ gm/ml), vancomycin (0.016 μ gm/ml) and linezolid (0.5 μ gm/ml) and resistant to gentamicin (MIC >16 μ gm/ml) and cotrimoxazole (MIC > 40 μ gm/ml). After 5 days of incubation, blood culture also grew same organism with same sensitivity pattern. Urine culture was sterile. There was no significant improvement from the first presentation, except reduced drain fluid from intercostal site. As per the culture report, the empirical antibiotic was changed to inj. ceftriaxone and inj. linezolid. On the fifth day of targeted therapy, pleural pus was still there although minimal, and was sent for bacterial culture was sterile. But on the seventh day of hospitalization, the patient developed right lower limb necrotizing fasciitis with myonecrosis. Fasciotomy was done and it revealed necrotic muscles of lower leg posterior compartment with hematoma in the intra-muscular compartment. Unfortunately, the patient passed away on twelfth day of hospitalization due to acute myocardial infarction.

Discussion

We did the literature search over past 10 years (2011–2020) using search engines PubMed using the MeSH term, “ Granulicatella adiacens .” Case reports with only monomicrobial infection due to G. adiacens were included in the review. All articles published in English were included in this analysis.

We reviewed 77 literatures on the subject ( G. adiacens ) over the past 10 years (2011–2020). Using the inclusion and exclusion criteria, 24 literature were found relevant and included in the review. 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Clinical details of all published literature are compiled in the Table 1 . As per the review of literature of last 10 years, G. adiacens is found to be the cause of various infections such as bacteremia, endocarditis, osteomyelitis, septic arthritis, discitis, prosthetic joint infections, carbuncle, bacterascites (spontaneous bacterial peritonitis), dacryocystitis, and abscess. Out of these, 13 isolated from blood (4 bacteremia, 8 endocarditis, 1 septic arthritis), 10 from synovial fluid/pus (6 prosthetic joint infection, 2 osteomyelitis, 2 discitis), one each from dacryocystitis, bacterascites, and carbuncle. Further extending search in PubMed using MeSH terms such as “empyema” and “ Granulicatell a” found only one case report of empyema (pleural pus) caused by Granulicatella elegans . 32 None of them were from empyema pus and blood simultaneously except our present report of G. adiacens . All cases were reported from abroad, except three from India: one from New Delhi (suprapatellar abscess), one from Odisha (carbuncle), and the present study from Bhubaneswar, Odisha (empyema pus and blood). To the best of our knowledge, the present study is the first case report of thoracic empyema caused by G. adiacens complicated to necrotizing fasciitis and sepsis.

Table 1

Clinicoepidemiological details of infections caused by Granulicatella adiacens

Infections caused by Granulicatella adiacens	Year	Geographical location	Age/sex	Clinical diagnosis	Clinical samples	References
Bacteremia	2011	Charlottesville, Virginia	89 y/F	Multiple trauma victim with bacteremia	Blood	8
	2011	New Haven, Connecticut, USA	1 d/Mch	Early onset neonatal sepsis	Blood	9
	2013	Rome, Italy	7 y/F	Shone syndrome (coarctation of aorta, mitral stenosis and subvalvular aortic stenosis) with Bacteremia	Blood	10
			5 y/M	Infundibular pulmonary stenosis with Bacteremia.	Blood
Endocarditis	2013	San Diego, CA, U.S.A.	50 y/M	Bivalvular (mitral and aortic valves) endocarditis	Blood	11
	2013	Kerala, India	63 y/M	Infective endocarditis	Blood	12
	2015	Australia	57 y/M	Subacute Bacterial endocarditis with type II mixed cryoglobulinemia	Blood	13
	2016	Tokyo, Japan	67 y/F	Infective endocarditis with Sjogren's syndrome with oral complications	Blood	14
	2019	Columbia, USA	44 y/F	Endocarditis, osteomyelitis, brain abscess	Blood	15
	2019	Switzerland	32 y/F	Cardiac implantable electronic device related infection and bioprosthesis endocarditis	Blood	16
	2019	U.S.A.	82 y/M	Bilateral lower extremity purpuric rash and complete heart block secondary to infective endocarditis	Blood	17
	2020	Farmington CT, United States	46 y/M	Infective endocarditis and glomerulonephritis	Blood	18
Prosthetic joint infection	2013	Paris, France	55 y/M	Prosthetic joint infection (knee) after dental treatment	Knee fluid aspirate	19
	2016	Peterborough, Cambridgeshire, PE3 9GZ, UK	81 y/M	Prosthetic joint infection (hip)	Pus aspirate from hip	20
	2017	Marseille, France	75 y/M	Prosthetic joint infection (hip)	Synovial fluid	21
			65 y/M	Prosthetic joint infection (knee)	Synovial fluid
			44 y/F	Prosthetic joint infection (hip)	Surgical biopsy sample
	2017	Eau Claire, WI, USA	64 y/M	Prosthetic joint infection (knee)	Synovial fluid	22
Osteomyelitis	2016	Swedish Neuroscience Institute	46 y/M	Vertebral osteomyelitis	Vertebral body biopsy tissue	23
	2018	Kitakyushu, Japan.	10 y/F	Mandibular osteomyelitis	Bone marrow fluid	24
Septic arthritis	2019	Iowa City, Iowa	5 y/M	Ruptured appendicitis and retrocecal abscess presenting as atraumatic knee pain	Blood	25
Discitis	2013	Tokyo, Japan	48 y/F	Pyogenic discitis	Blood and disk biopsy sample	26
	2020	Rome, Italy	51 y/M	Spondylodiscitis (L1-L2 and L5-S1 discs)	disk biopsy sample	27
Dacryocystitis	2015	Morgantown, WV 26505, USA	46 y/F	Dacryocystitis	Purulent material from lacrimal sac	28
Bacterascites	2015	Charlottesville, VA 22908, USA	50 y/M	Large distended abdomen (ascites)	Ascitic fluid	29
Abscess	2018	New Delhi, India	30 y/M	Suprapatellar abscess	Aspirated pus from Knee joint swelling	30
			18 y/M	Elbow abscess	Pus swab
Carbuncle	2012	Odisha, India	56 y/M	Carbuncle, multiple discharging sinus over right scapular region	Pus	31
Empyema	2016	South Africa	30 y/F	Empyema underlying TB and HIV Caused by Granulicatella elegans	Pleural pus	32
Empyema	2020	Odisha, India	68 y/M	Empyema underlying diabetes mellitus and alcoholism	Pleural pus and Blood	Present study

Necrotizing fasciitis is a destructive and rapidly progressive soft tissue infection with significant morbidity and mortality. It may necessitate surgical intervention and may progress to systemic involvement, septic shock, and multiorgan failure without intervention. Although the exact cause of necrotizing fasciitis in the present case is not clear, as clinical sample could not be sent for microbiological investigations. But association with G. adiacens infection cannot be ruled out as there is one published report of cervical necrotizing fasciitis due to polymicrobial cause including G. adiacens following dental extraction and its surgical management. 33

Due to requirement of fastidious culture conditions and non-specific colony morphology, serious diagnostic difficulties may arise in cases of NVS infections. Commercial blood culture media contain pyridoxal and support the growth of NVS. However, in the present case, the bacteria isolated from pleural pus and blood samples grew on commercial 5% sheep blood agar (without any additional supplement) as cited in other reports. 31

With evolvement of the newer advanced laboratory systems, that is, the MALDI-TOF (VITEK MS, Bruker MS) system and the VITEK 2 system, NVS can be identified up to the species level. In our case also, the isolate was identified using the VITEK 2 system.

As NVS are parts of normal commensal flora of human mouth, genital and intestinal tracts, their exact pathogenic role is unclear. Proteins secreted by these species may act as virulence determinants for interaction with the host. The secretome of G. adiacens is well documented in infective endocarditis and oral infections. More importantly, G. adiacens secretome comprised several putative virulence proteins, which enhance bacterial colonization and virulence through their multifunctional roles. 34 35 Granulicatella and Abiotrophia spp. have the ability to bind to fibronectin and other extracellular matrix proteins and this binding ability appears to correlate with their degree of infectivity. 36

Thus, clinicians should be aware of the pathogenic potential of these organisms. They can be easily overlooked because of their poor growth or no-growth on conventional solid media. NVS should be suspected when Gram stain shows microbial cells but cultures are negative. Due to the difficulties in identification of these bacteria, it is crucial for microbiology staff to be vigilant to prevent misidentification. For culture-negative cases, molecular test or Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS) would be a faster and reliable method for identification. The difficulty in identifying these organisms leads to delays in diagnosis. In addition, the results of susceptibility testing may not be accurate or reliable. Therefore, appropriate supplemented media and a reliable detection system should be used to identify these fastidious organisms.