Molecular identification of Gemella species from three patients with endocarditis

An Emerging Threat: A Systematic Review of Endocarditis Caused by Gemella Species

Infective endocarditis caused by Gemella species is increasingly recognized as an emerging clinical entity. Gemella species are fastidious gram-positive cocci that are typically commensal organisms but can become opportunistic pathogens. This systematic review aimed to provide a comprehensive overview of endocarditis due to Gemella species by synthesizing existing evidence. A total of 52 case reports were identified through a rigorous search and selection process. The most prevalent causative species were G. morbillorum (46.3%) and G. haemolysans (25.9%), with a striking male predominance (79.6%). The clinical presentation was largely nonspecific, mirroring typical infective endocarditis. However, the indolent nature of the illness and fastidious growth requirements of Gemella species often led to diagnostic delays. Echocardiography, particularly transesophageal echocardiography, played a crucial role in the diagnosis, enabling the detection of valvular vegetation and the assessment of complications. Management posed significant challenges, including the need for broad-spectrum empirical antibiotic therapy and increasing antimicrobial resistance among Gemella isolates. Surgical intervention was frequently required for severe valvular dysfunction, persistent infection, or embolic complications. Despite advances in diagnosis and treatment, endocarditis due to Gemella species remains associated with significant morbidity and mortality, underscoring the importance of early recognition and multidisciplinary management. This review highlights the emerging clinical significance of Gemella species as causative agents of infective endocarditis and identifies areas for further research.

A Case of Gemella morbillorum Causing Multi-valvular Endocarditis

This is the case of a 31-year-old man with no significant past medical history who presented to the emergency department experiencing persistent fevers, chills, and malaise for the past 2-3 weeks. During this period, he had multiple urgent care visits for possible left-sided otitis media which was treated with short a course of Augmentin. While on antibiotics his symptoms would improve, but they would reappear once he had finished treatment. The patient also had significant dental carries with a chronic right molar infection. At the emergency department, blood cultures grew two out of two Gemella morbillorum. Transthoracic echocardiography showed a 1 cm x 0.5 cm mobile density on the left coronary cusp of the aortic valve with moderate-severe aortic insufficiency. The patient was started on empiric IV vancomycin. Further workup revealed that the source of infection was dental carries. While proceeding with a transesophageal echocardiogram, the patient went into flash pulmonary edema requiring ICU admission. Imaging revealed an elongated 1.7 cm x 0.6 cm vegetation attached to the base of the left coronary cusp on the left ventricular outflow tract side with severe aortic regurgitation and a small 0.8 cm x 0.8 cm vegetation on the atrial side of the anterior mitral leaflet at A2 associated with mitral leaflet perforation with severe mitral regurgitation. Oral surgery removed the infected teeth. Cardiothoracic surgery performed open heart valve replacement which revealed a completely destroyed aortic valve, droplet vegetation, and destruction of the mitral valve leading to mechanical valve replacement. The patient received a two-week course of gentamycin while in the ICU with meropenem. Once sensitivities were back, he was switched to IV penicillin therapy for a total of six weeks.

Infective endocarditis caused by Gemella haemolysans in a patient with bicuspid aortic valve: A case report

Gemella haemolysans is a gram-positive coccus, and commensal of the upper respiratory tract and oral mucosa. In rare cases, it has been identified as an opportunistic pathogen in the development of endocarditis. Here, we describe a case of Gemella haemolysans endocarditis in a patient with bicuspid aortic valve. A 14-year-old male presented to our hospital with a 1-month history of intermittent fever. Gemella haemolysans was isolated from the patient's blood cultures. Transesophageal echocardiography revealed severe aortic stenosis and a pseudoaneurysm of the mitral-aortic intervalvular fibrosa. The patient underwent aortic valve replacement with pseudoaneurysm of the mitral-aortic intervalvular fibrosa repair and remained symptom-free during follow-up. This case highlights the importance of considering atypical pathogens as causative agents of infective endocarditis.

Antimicrobial Susceptibility to 27 Drugs and the Molecular Mechanisms of Macrolide, Tetracycline, and Quinolone Resistance in Gemella sp

Gemella is a catalase-negative, facultative anaerobic, Gram-positive coccus that is commensal in humans but can become opportunistic and cause severe infectious diseases, such as infective endocarditis. Few studies have tested the antimicrobial susceptibility of Gemella. We tested its antimicrobial susceptibility to 27 drugs and defined the resistant genes using PCR in 58 Gemella strains, including 52 clinical isolates and six type strains. The type strains and clinical isolates included 22 G. morbillorum, 18 G. haemolysans (GH) group (genetically indistinguishable from G. haemolysans and G. parahaemolysans), 13 G. taiwanensis, three G. sanguinis, and two G. bergeri. No strain was resistant to beta-lactams and vancomycin. In total, 6/22 (27.3%) G. morbillorum strains were erythromycin- and clindamycin-resistant ermB-positive, whereas 4/18 (22.2%) in the GH group, 7/13 (53.8%) G. taiwanensis, and 1/3 (33.3%) of the G. sanguinis strains were erythromycin-non-susceptible mefE- or mefA-positive and clindamycin-susceptible. The MIC90 of minocycline and the ratios of tetM-positive strains varied across the different species-G. morbillorum: 2 µg/mL and 27.3% (6/22); GH group: 8 µg/mL and 27.8% (5/18); G. taiwanensis: 8 µg/mL and 46.2% (6/13), respectively. Levofloxacin resistance was significantly higher in G. taiwanensis (9/13 69.2%) than in G. morbillorum (2/22 9.1%). Levofloxacin resistance was associated with a substitution at serine 83 for leucine, phenylalanine, or tyrosine in GyrA. The mechanisms of resistance to erythromycin and clindamycin differed across Gemella species. In addition, the rate of susceptibility to levofloxacin differed across Gemella sp., and the quinolone resistance mechanism was caused by mutations in GyrA alone.

Integrative analysis of microbial 16S gene and shotgun metagenomic sequencing data improves statistical efficiency

Background

The most widely used technologies for profiling microbial communities are 16S marker-gene sequencing and shotgun metagenomic sequencing. Interestingly, many microbiome studies have performed both sequencing experiments on the same cohort of samples. The two sequencing datasets often reveal consistent patterns of microbial signatures, highlighting the potential for an integrative analysis to improve power of testing these signatures. However, differential experimental biases, partially overlapping samples, and differential library sizes pose tremendous challenges when combining the two datasets. Currently, researchers either discard one dataset entirely or use different datasets for different objectives.

Methods

In this article, we introduce the first method of this kind, named Com-2seq, that combines the two sequencing datasets for testing differential abundance at the genus and community levels while overcoming these difficulties. The new method is based on our LOCOM model (Hu et al., 2022), which employs logistic regression for testing taxon differential abundance while remaining robust to experimental bias. To benchmark the performance of Com-2seq, we introduce two ad hoc approaches: applying LOCOM to pooled taxa count data and combining LOCOM p-values from analyzing each dataset separately.

Results

Our simulation studies indicate that Com-2seq substantially improves statistical efficiency over analysis of either dataset alone and works better than the two ad hoc approaches. An application of Com-2seq to two real microbiome studies uncovered scientifically plausible findings that would have been missed by analyzing individual datasets.

Conclusions

Com-2seq performs integrative analysis of 16S and metagenomic sequencing data, which improves statistical efficiency and has the potential to accelerate the search of microbial communities and taxa that are involved in human health and diseases.

Integrative analysis of microbial 16S gene and shotgun metagenomic sequencing data improves statistical efficiency

The most widely used technologies for profiling microbial communities are 16S marker-gene sequencing and shotgun metagenomic sequencing. Interestingly, many microbiome studies have performed both sequencing experiments on the same cohort of samples. The two sequencing datasets often reveal consistent patterns of microbial signatures, highlighting the potential for an integrative analysis to improve power of testing these signatures. However, differential experimental biases, partially overlapping samples, and differential library sizes pose tremendous challenges when combining the two datasets. Currently, researchers either discard one dataset entirely or use different datasets for different objectives. In this article, we introduce the first method of this kind, named Com-2seq, that combines the two sequencing datasets for the objective of testing differential abundance at the genus and community levels while overcoming these difficulties. We demonstrate that Com-2seq substantially improves statistical efficiency over analysis of either dataset alone and works better than two ad hoc approaches.

A Rare Pathogen of Bones and Joints: A Systematic Review of Osteoarticular Infections Caused by Gemella morbillorum

Osteoarticular infections (OAIs) caused by Gemella morbillorum (G. morbillorum) are a rare clinical entity. This study aimed to review all published cases of OAI due to G. morbillorum. A systematic review of PubMed, Scopus, and Cochrane Library was conducted to report the demographic and clinical characteristics, microbiological data, management, and outcome of OAIs caused by G. morbillorum in the adult population. A total of 16 studies reporting on 16 patients were included in this review. Eight patients had arthritis and eight patients had osteomyelitis/discitis. The most reported risk factors were immunosuppression, poor dental hygiene/dental infections, and recent gastrointestinal (GI) endoscopy. Five cases of arthritis occurred in a native joint while three patients had prostheses. The potential source of G. morbillorum infection was documented in more than half of the cases (56%) (most commonly odontogenic and GI sources (25% and 18%, respectively). The knee and hip joints were the most frequently affected joints in patients with arthritis, while the thoracic vertebrae were the most common sites for osteomyelitis/discitis. The blood cultures were positive in three patients with arthritis (37.5%) and five patients with osteomyelitis/discitis (62.5%). Associated endovascular infection was found in five patients with bacteremia. Contiguous spread (adjacent mediastinitis) was documented in two patients with sternal osteomyelitis and thoracic vertebral osteomyelitis. Surgical interventions were performed for 12 patients (75%). Most strains of G. morbillorum were susceptible to penicillin and cephalosporins. All patients with reported outcomes had achieved complete recovery. G. morbillorum is an emerging pathogen for OAIs in certain susceptible populations with specific risk factors. This review reported the demographic, clinical, and microbiological features of OAIs caused by G. morbillorum. A careful evaluation of an underlying infectious focus is warranted to control the source. When G. morbillorum bacteremia is present, it is also necessary to have a high index of suspicion to rule out an associated endovascular infection.

<i>Gemella hemolysans</i> endocarditis and septicemia: case report and literature review

A suggestive report of Gemella hemolysans endocarditis and sepsis is described and commented on the ground of an updated literature review.

A substrate-induced gating mechanism is conserved among Gram-positive IgA1 metalloproteases

The mucosal adaptive immune response is dependent on the production of IgA antibodies and particularly IgA1, yet opportunistic bacteria have evolved mechanisms to specifically block this response by producing IgA1 proteases (IgA1Ps). Our lab was the first to describe the structures of a metal-dependent IgA1P (metallo-IgA1P) produced from Gram-positive Streptococcus pneumoniae both in the absence and presence of its IgA1 substrate through cryo-EM single particle reconstructions. This prior study revealed an active-site gating mechanism reliant on substrate-induced conformational changes to the enzyme that begged the question of whether such a mechanism is conserved among the wider Gram-positive metallo-IgA1P subfamily of virulence factors. Here, we used cryo-EM to characterize the metallo-IgA1P of a more distantly related family member from Gemella haemolysans, an emerging opportunistic pathogen implicated in meningitis, endocarditis, and more recently bacteremia in the elderly. While the substrate-free structures of these two metallo-IgA1Ps exhibit differences in the relative starting positions of the domain responsible for gating substrate, the enzymes have similar domain orientations when bound to IgA1. Together with biochemical studies that indicate these metallo-IgA1Ps have similar binding affinities and activities, these data indicate that metallo-IgA1P binding requires the specific IgA1 substrate to open the enzymes for access to their active site and thus, largely conform to an "induced fit" model.

Acute Hematogenous Periprosthetic Hip Infection by Gemella morbillorum, Successfully Treated with Debridement, Antibiotics and Implant Retention: A Case Report and Literature Review of Osteoarticular Gemella morbillorum Infections

Gemella morbillorum is a facultative anaerobic, catalase-negative and non-spore forming Gram-positive cocci. It can be found as part of the normal oropharyngeal flora, in the gastrointestinal tract and the female genital tract. However, it can be a causal agent of infections such as endocarditis, meningitis or brain abscesses, and very rarely can cause osteoarticular infections. Herein, a case report of an acute hematogenous prosthetic hip infection caused by Gemella morbillorum, successfully treated with a DAIR and beta-lactam antibiotic therapy, is presented. We provide a literature review of the other orthopedic-related infections caused by this microorganism.

Gemella haemolysans: Rare case of automatic implantable cardioverter-defibrillator (AICD) lead infection

We present a rare case of Gemella haemolysans automated implantable cardioverter defibrillator (AICD) lead infection. Gemella species are catalase-negative, facultative anaerobic, Gram-positive cocci which are found in normal human oral flora. Gemella are often incorrectly identified on routine Gram stain and culture, requiring advanced techniques such as PCR. Gemella has been shown to be a rare cause infective endocarditis in case reports; however, there has not been a report of an isolated AICD lead infection. AICD infections with gram positive organisms other than Staphylococcus species has been associated with more aggressive infections and higher mortality. Standard treatment for Gemella consists of β-lactam inhibitors and aminoglycosides. In this case, we present an alternative antibiotic treatment with vancomycin and ceftriaxone. A case series for Gemella haemolysans endocarditis, without lead infection, reported the use of vancomycin and ceftriaxone with good results. This approach is similar to methicillin-resistant staphylococcus aureus (MRSA) bacteremia salvage therapy. In addition, this case highlights the importance of culture and sensitivity in the selection of antibiotics, particularly avoiding nephrotoxic drugs when possible.

Gemella morbillorum mitral valve endocarditis in a patient with a history of mitral valve annuloplasty

A woman with a history of congenital heart disease status post multiple valve operations including mitral valve repair presented with 2 months of low back pain and general malaise. Blood cultures returned positive for Gram-positive cocci. While transthoracic echocardiography did not identify vegetations, transoesophageal echocardiography visualised vegetations on the patient's mitral valve, which had previously undergone repair with annuloplasty. The patient was found to have infectious endocarditis (IE), caused by Gemella morbillorum The patient was treated with over 6 weeks of intravenous antibiotics. Cases of Gemella-associated IE are rare and largely relegated to case reports. This report aims to contribute to the literature regarding this subject, and to further characterise the presentation and treatment of Gemella-associated IE. Additionally, this report emphasises the importance of maintaining a high suspicion of IE in a patient with non-specific malaise in the setting of prior cardiac valve operation.

Characterization of Changes and Driver Microbes in Gut Microbiota During Healthy Aging Using A Captive Monkey Model

Recent population studies have significantly advanced our understanding of how age shapes the gut microbiota. However, the actual role of age could be inevitably confounded due to the complex and variable environmental factors in human populations. A well-controlled environment is thus necessary to reduce undesirable confounding effects, and recapitulate age-dependent changes in the gut microbiota of healthy primates. Herein we performed 16S rRNA gene sequencing, characterized the age-associated gut microbial profiles from infant to elderly crab-eating macaques reared in captivity, and systemically revealed the lifelong dynamic changes of the primate gut microbiota. While the most significant age-associated taxa were mainly found as commensals such as Faecalibacterium, the abundance of a group of suspicious pathogens such as Helicobacter was exclusively increased in infants, underlining their potential role in host development. Importantly, topology analysis indicated that the network connectivity of gut microbiota was even more age-dependent than taxonomic diversity, and its tremendous decline with age could probably be linked to healthy aging. Moreover, we identified key driver microbes responsible for such age-dependent network changes, which were further linked to altered metabolic functions of lipids, carbohydrates, and amino acids, as well as phenotypes in the microbial community. The current study thus demonstrates the lifelong age-dependent changes and their driver microbes in the primate gut microbiota, and provides new insights into their roles in the development and healthy aging of their hosts.

A Rare Case of Gemella haemolysans Infection of Knee Arthroplasty

Gemella haemolysans is a facultative, catalase-negative, anaerobic, gram-positive cocci. It is known to mostly cause endocarditis, meningitis, peritonitis, and cerebral abscesses. However, it is extremely rare for this organism to cause infections of an orthopedic nature, with only a single report of infection in total knee arthroplasty (TKA). We present a rare case of knee arthroplasty infection caused by G. haemolysans four years after an uncomplicated TKA procedure.

Multi-valvular infective endocarditis from Gemella morbillorum

Gemella morbillorum is increasingly implicated in infectious endocarditis. Our patient presented with anaemia and renal failure with evidence of infarcts and embolic disease. He was found to have endocarditis with an organism that could not speciate with standard culture methods requiring matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) for identification and susceptibilities. While involvement of mitral and aortic valves can be expected with Gemella, he had rare involvement of the pulmonic valve in a structurally normal heart. Although bacteriological cure was achieved, due to the locally destructive nature of Gemella, he ultimately required valve replacements for heart failure resolution. Workup for commonly implicated pathologies associated with G. morbillorum led to suspicion of gastrointestinal malignancy with findings of occult bleeding prompting an ongoing evaluation. With improved access to advanced diagnostics, G. morbillorum has been increasingly identified in infectious endocarditis. Given its destructive nature, it is important for clinicians to consider this organism is difficult to identify isolates.

A Metatranscriptomics Survey of Microbial Diversity on Surfaces Post-Intervention of cleanSURFACES® Technology in an Intensive Care Unit

Hospital-acquired infections (HAIs) pose a serious threat to patients, and hospitals spend billions of dollars each year to reduce and treat these infections. Many HAIs are due to contamination from workers’ hands and contact with high-touch surfaces. Therefore, we set out to test the efficacy of a new preventative technology, AIONX^® Antimicrobial Technologies, Inc’s cleanSURFACES^®, which is designed to complement daily chemical cleaning events by continuously preventing re-colonization of surfaces. To that end, we swabbed surfaces before (Baseline) and after (Post) application of the cleanSURFACES^® at various time points (Day 1, Day 7, Day 14, and Day 28). To circumvent limitations associated with culture-based and 16S rRNA gene amplicon sequencing methodologies, these surface swabs were processed using metatranscriptomic (RNA) analysis to allow for comprehensive taxonomic resolution and the detection of active microorganisms. Overall, there was a significant (P < 0.05) global reduction of microbial diversity in Post-intervention samples. Additionally, Post sample microbial communities clustered together much more closely than Baseline samples based on pairwise distances calculated with the weighted Jaccard distance metric, suggesting a defined shift after product application. This shift was characterized by a general depletion of several microbes among Post samples, with multiple phyla also being reduced over the duration of the study. Notably, specific clinically relevant microbes, including Staphylococcus aureus, Clostridioides difficile and Streptococcus spp., were depleted Post-intervention. Taken together, these findings suggest that chemical cleaning events used jointly with cleanSURFACES^® have the potential to reduce colonization of surfaces by a wide variety of microbes, including many clinically relevant pathogens.

Gemella haemolysans inhibits the growth of the periodontal pathogen Porphyromonas gingivalis

The oral microbiome plays an important role in the human microbial community and in maintaining the health of an individual. Imbalances in the oral microbiome may contribute to oral and systemic diseases. The progression of periodontal disease is closely related to the growth of bacteria, such as Porphyromonas gingivalis, in the oral cavity. However, the pathogen growth mechanism specific to periodontal disease remains unknown. This study aimed to identify bacteria associated with periodontal health by focusing on hemolytic bacteria. Unstimulated saliva samples were collected from ten periodontitis patients and five healthy subjects to detect and identify the presence of hemolytic bacteria. The saliva of healthy subjects contained a higher proportion of G. haemolysans than saliva samples from patients with periodontitis. Growth inhibition assays indicated that the protein components contained in the culture supernatant of G. haemolysans directly suppressed the growth of P. gingivalis. This study shows that the presence of G. haemolysans in saliva is associated with periodontal health and that it inhibits the growth of P. gingivalis in vitro.

Risk Factors and Patient Profile of Infective Endocarditis due to Gemella spp

BACKGROUND

The diagnosis of infective endocarditis is difficult, especially when it involves atypical organisms. Therefore, our study identified risk factors of infective endocarditis caused by rare pathogen, Gemella spp.

METHODS

A systematic review was conducted to investigate characteristics of endocarditis patients infected with Gemella spp. using the search term "Gemella" and "endocarditis." Case reports were gathered by searching Medline/Pubmed, Google Scholar, CINAHL, Cochrane CENTRAL, and Web of Science databases. 83 articles were selected for review.

RESULTS

Five species of Gemella were identified. Typical patients were males between 31 and 45 years of age. On admission, patients had fever, tachycardia, and normal blood pressure. Common clinical manifestation other than fever included fatigue and weakness, chills and sweating, and nausea, vomiting, diarrhea, and weight changes. One in four reported a history of congenital heart disease, and a recent oral cavity infection. Laboratory tests reveal anemia, leukocytosis, and elevated erythrocyte sedimentation in all age groups, elevated C-reactive protein is observed among adult and geriatric populations only. Mitral and aortic valves were most commonly infected by Gemella spp.. The most common Gemella spp.-susceptible antibiotics were penicillin, vancomycin, cephalosporin, macrolide, and aminoglycosides. However, antibiotic resistance was observed against penicillin, aminoglycoside, and fluoroquinolone. Antibiotic course of at least six weeks resulted in superior clinical improvements than durations under six weeks. Finally, one in two patients underwent valve replacement or repair, with common complications affecting the cardiovascular, neurological, and renal systems. Finally, death occurred in 1 in 8 patients, half of which occurred post-surgical procedure, and the majority occurring equal to or greater than 1 week from admission.

CONCLUSION

Our systematic review highlights the importance of considering rare pathogens, particularly in the presence of predisposing risk factors.

Benefits of a Pre-Treatment Comprehensive Geriatric Assessment in a Rare Case of Gemella Haemolysans Endocarditis in an 86-Year-Old Patient and a Review of the Literature

Infective endocarditis is a serious condition, which is associated with high mortality in elderly patients. Gemella haemolysans (GH) is a microorganism from the Streptococcus family, rarely involved in infective endocarditis. Here, we present a case of Gemella haemolysans endocarditis in an 86-year-old patient, successfully treated by antibiotics and surgery following a pre-treatment comprehensive geriatric assessment (CGA). This case is discussed in the context of a review of all published cases of Gemella haemolysans endocarditis. We illustrate the benefit of a systematic pre-treatment comprehensive geriatric assessment in elderly patients with infective endocarditis.

The Microbiomes of Pancreatic and Duodenum Tissue Overlap and Are Highly Subject Specific but Differ between Pancreatic Cancer and Noncancer Subjects

BACKGROUND

In mice, bacteria from the mouth can translocate to the pancreas and impact pancreatic cancer progression. In humans, oral bacteria associated with periodontal disease have been linked to pancreatic cancer risk. It is not known if DNA bacterial profiles in the pancreas and duodenum are similar within individuals.

METHODS

Tissue samples were obtained from 50 subjects with pancreatic cancer or other conditions requiring foregut surgery at the Rhode Island Hospital (RIH), and from 34 organs obtained from the National Disease Research Interchange. 16S rRNA gene sequencing was performed on 189 tissue samples (pancreatic duct, duodenum, pancreas), 57 swabs (bile duct, jejunum, stomach), and 12 stool samples.

RESULTS

Pancreatic tissue samples from both sources (RIH and National Disease Research Interchange) had diverse bacterial DNA, including taxa typically identified in the oral cavity. Bacterial DNA across different sites in the pancreas and duodenum were highly subject specific in both cancer and noncancer subjects. Presence of genus Lactobacillus was significantly higher in noncancer subjects compared with cancer subjects and the relative abundance of Fusobacterium spp., previously associated with colorectal cancer, was higher in cancer subjects compared with noncancer subjects.

CONCLUSIONS

Bacterial DNA profiles in the pancreas were similar to those in the duodenum tissue of the same subjects, regardless of disease state, suggesting that bacteria may be migrating from the gut into the pancreas. Whether bacteria play a causal role in human pancreatic cancer needs to be further examined.

IMPACT

Identifying bacterial taxa that differ in cancer patients can provide new leads on etiologically relevant bacteria.

Gemella haemolysans bacteremia in a patient with secondary peritonitis due to a duodenal ulcer perforation: A case report

We describe a case of Gemella haemolysans septic shock in a 75-year old Japanese male with a duodenal perforation and secondary peritonitis. Blood cultures on admission were positive for Gram-positive and Gram-variable cocci, and G. haemolysans was identified using whole cell matrix-assisted laser desorpition/ionization mass spectrometry (MALDI-TOF MS), with a score value of 2.12. The 16S rRNA sequencing was difficult to use as a diagnostic test because there was more than 99% sequence homology with related bacterial strains. Based on both the biochemical profiles and whole groEL sequence, we concluded that the strain in our patient was G. haemolysans. The patient was successfully treated with a 16-day course of antimicrobials. His clinical condition improved, and no evidence of a relapse of the infection was noted. Although MALDI-TOF MS and 16S rRNA sequencing are useful for identification of the species, the basic biochemical profile is also important to identify a rare species.

The first case report of infective endocarditis caused by Gemella taiwanensis

Gemella is a facultative anaerobic Gram-positive coccus and a rare cause of infective endocarditis (IE). Gram staining may eventually misidentify the organism, which tends to easily decolorize and manifest as either Gram-negative or Gram-variable. Commercial biochemical tests are often used to identify Gemella, but the methods they employ sometimes lack accuracy. A 52-year-old woman was diagnosed with Gemella taiwanensis IE after initial identification of the pathogen as Gemella haemolysans using biochemical tests combined with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). She was treated successfully with penicillin, gentamicin, and mitral valve replacement. To our knowledge, this is the first case of IE confirmed by 16S rRNA gene and groEL sequencing to have been caused by G. taiwanensis. The accurate diagnosis of rare or difficult-to-identify pathogens is a major challenge for clinical microbiological laboratories. The concurrent use of molecular methods could lead to the recognition of new or different pathogens.

Gemella Species Bacteremia and Stroke in an Elderly Patient with Respiratory Tract Infection

Gemella species are part of normal human flora. They are rarely associated with infections. As opportunistic pathogens, they can cause life-threatening infection in individuals with risk factors. We present an unusual case of an elderly patient, with no predisposing risk factors, who presented with respiratory tract infection and Gemella species bacteremia and suffered a stroke in the absence of features of endocarditis.

Endocarditis due to Gemella haemolysans in a newly diagnosed multiple myeloma patient

An 87-year-old Caucasian woman with hypertension, diabetes mellitus type 2, and COPD was admitted with 1-week duration of back pain and weight gain. The physical examination revealed jugular venous distention, rales in the left lower lung field, and severe pitting edema over lower extremities. As workup for leukocytosis, blood cultures grew Gemella haemolysans. Subsequently, a transthoracic echocardiogram revealed vegetation on the non-coronary aortic leaflet and mild aortic stenosis. She was treated with ampicillin and gentamicin. After further investigation, the patient was diagnosed with plasma cell myeloma, the monoclonal lambda type. This is the first reported case of G. haemolysans endocarditis in a multiple myeloma patient.

Unreported neurological complications of Gemella bergeriae infective endocarditis

We report the first case of native aortic and mitral valve endocarditis due to Gemella bergeriae from the Middle East in a young patient with rheumatic heart disease. Our case illustrates a fulminant course of infection with G. bergeriae endocarditis that was complicated by embolic stroke, as well as intracerebral and subarachnoid haemorrhage secondary to rupture of a mycotic aneurysm in the right middle cerebral artery. This case highlights the dire, unreported neurological complications of infective endocarditis due to a rare causative organism-G. bergeriae.

Gemella parahaemolysans sp. nov. and Gemella taiwanensis sp. nov., isolated from human clinical specimens

Four Gram-staining-positive, catalase-negative, coccoid isolates, designated NTUH_1465(T), NTUH_2196, NTUH_4957 and NTUH_5572(T), were isolated from human specimens. The four isolates displayed more than 99.6% 16S rRNA gene sequence similarity with Gemella haemolysans ATCC 10379(T), and 96.7 to 98.6% similarity with Gemella sanguinis ATCC 700632(T), Gemella morbillorum ATCC 27824(T) or Gemella cuniculi CCUG 42726(T). However, phylogenetic analysis of concatenated sequences of three housekeeping genes, groEL, rpoB and recA, suggested that the four isolates were distinct from G. haemolysans ATCC 10379(T) and other species. Isolates NTUH_2196, NTUH_4957 and NTUH_5572(T) clustered together and formed a stable monophyletic clade. DNA-DNA hybridization values among strains NTUH_1465(T) and NTUH_5572(T) and their phylogenetically related neighbours were all lower than 49%. The four isolates could be distinguished from G. haemolysans and other species by phenotypic characteristics. Based on the phylogenetic and phenotypic results, two novel species Gemella parahaemolysans sp. nov. (type strain NTUH_1465(T) = BCRC 80365(T) = JCM 18067(T)) and Gemella taiwanensis sp. nov. (type strain NTUH_5572(T) = BCRC 80366(T) = JCM 18066(T)) are proposed.

Cerebrospinal fluid shunt infection due to Gemella haemolysans

Gemella haemolysans has long been considered a commensal in the human upper respiratory tract. Commensals are natural inhabitants on or within another organism, deriving benefit without harming or benefiting the host. Opportunistic infection of the CNS by the species is exceedingly rare. In the present case, a 16-year-old boy was admitted with a ventriculoperitoneal shunt infection, which was confirmed to be due to G. haemolysans. Following antibiotic treatment, removal of the old shunt, and delayed insertion of a new shunt, the patient made a full neurological recovery. To the authors' knowledge, this is the eighth case of CNS infection with G. haemolysans. Although prosthesis-related infections have been reported in other systems, this is the first case of CNS infection by the bacterium associated with an implant. Previous reported cases of CNS infection by G. haemolysans are reviewed. Due to the variable Gram staining property of the organism, the difficulty in diagnosing G. haemolysans infection is emphasized.

The influence of iron availability on human salivary microbial community composition

It is a well-recognized fact that the composition of human salivary microbial community is greatly affected by its nutritional environment. However, most studies are currently focused on major carbon or nitrogen sources with limited attention to trace elements like essential mineral ions. In this study, we examined the effect of iron availability on the bacterial profiles of an in vitro human salivary microbial community as iron is an essential trace element for the survival and proliferation of virtually all microorganisms. Analysis via a combination of PCR with denaturing gradient gel electrophoresis demonstrated a drastic change in species composition of an in vitro human salivary microbiota when iron was scavenged from the culture medium by addition of the iron chelator 2,2'-bipyridyl. This shift in community profile was prevented by the presence of excessive ferrous iron (Fe(2+)). Most interestingly, under iron deficiency, the in vitro grown salivary microbial community became dominated by several hemolytic bacterial species, including Streptococcus spp., Gemella spp., and Granulicatella spp. all of which have been implicated in infective endocarditis. These data provide evidence that iron availability can modulate host-associated oral microbial communities, resulting in a microbiota with potential clinical impact.

Use of groESL as a target for identification of Abiotrophia, Granulicatella, and Gemella species

We determined the groESL sequences of three species of nutritionally variant streptococci (Abiotrophia defectiva, Granulicatella adiacens, and Granulicatella elegans) and three Gemella species (Gemella morbillorum, Gemella haemolysans, and Gemella sanguinis). The nucleotide sequence similarities between the groES and groEL genes of the above genera were 41.7 to 85.9% and 63.7 to 84.3%, respectively. The intraspecies similarities of groESL sequences for the isolates of Abiotrophia and Granulicatella species were 94.4 to 97.8% for groES and 94.0 to 98.2% for groEL. For Ge. morbillorum and Ge. sanguinis, all strains showed the same groESL spacer length (8 bp), and sequence identities within species were >97.8% for groES and >96.1% for groEL. However, higher intraspecies heterogeneity was observed in Ge. haemolysans. Phylogenetic analysis of groEL sequences separated the 6 isolates of Ge. haemolysans into two subgroups. Among these isolates, three isolates with the same groESL spacer region length (45 bp) clustered together but were distant from the ATCC reference strain (with a spacer length of 8 bp). The remaining three isolates, with a spacer length of 50 or 8 bp, clustered together. Although 16S rRNA gene sequence analysis did not provide enough discrimination for the 6 Ge. haemolysans isolates, rpoB gene sequence analysis supported the subgrouping. Based on the obtained groESL sequences, we developed a multiplex PCR that enables simple, rapid, and accurate identification of Abiotrophia, Granulicatella, and Gemella at the genus level. This assay would be helpful for identifying these fastidious and slow-growing organisms in clinical laboratories.

[Lethal aortic endocarditis due to Gemella morbillorum in a Djiboutian khat user]

We report a 22-year-old man who presented in January 2009 in Djibouti for an aortic-abscessed endocarditis due to Gemella morbillorum (G. morbillorum). A voluminous aortic abscess that extended to the perimembranous ventricular septum was fistulized into the right atrium. Atrioventricular conduction abnormalities were observed. The portal of entry was dental with multiples caries and a periodontitis attributed to khat chewing. The patient died within few days. Diagnosis, severity and management of endocarditis due to this rare bacterium are discussed.

Gemella morbillorum: an underestimated aetiology of central nervous system infection?

A case is reported of cerebellar abscess and diffuse cerebritis due to Gemella morbillorum. The clinical course was 'biphasic', developing with an acute meningeal infection followed shortly afterwards by suppuration in the cerebellar and cerebral parenchyma; this pattern seemed to suggest a latent survival of the aetiological agent, probably within the central nervous system (CNS), despite systemic antibiotic therapy. Based upon a review of cases so far described, infections of the CNS caused by G. morbillorum appear to be an emerging reality.

Endocarditis caused by Gemella morbillorum resistant to β-lactams and aminoglycosides

Two rare cases of Gemella morbillorum endocarditis, caused by a strain resistant to penicillin and gentamicin are reported. G. morbillorum is usually sensitive to beta-lactams and aminoglycosides. The present 2 cases raise concern that appropriate prophylaxis and empirical treatment may be more complicated than believed in the past.

Identification of Bartonella henselae in an aborted equine fetus

This report describes the characterization of a Bartonella henselae abortion in an equine fetus by gross, histologic, immunohistochemical, ultrastructural, and molecular methods. Bartonella henselae can cause cat scratch disease, bacillary angiomatosis, bacillary peliosis, and endocarditis in humans and other animals. The bacterium has been isolated from several mammalian species but only recently from equids; however, it has not been linked to abortion in equids. An aborted equine fetus exhibited necrosis and vasculitis in multiple tissues, with intralesional Gram-negative short-to-spirillar bacteria. Nucleotide sequence analysis of the bacterial 16S rRNA gene amplified from the DNA extracted from fetal tissues revealed 99.9% homology to that of B. henselae. The presence of B. henselae in the fetal tissues was further confirmed by polymerase chain reaction amplification and nucleotide sequence analysis of other Bartonella species-specific genes. Microorganisms were immunohistochemically labeled with a monoclonal antibody to B. henselae and were ultrastructurally characterized. Attempts to detect known causative agents of equine abortion were unsuccessful. Given the severity of vasculitis and the presence of intralesional bacteria, we concluded that B. henselae infection caused the abortion of this foal.

Gemella morbillorum in primary and secondary/persistent endodontic infections

OBJECTIVE

To investigate the presence of Gemella morbillorum by culture or nested PCR in primary and secondary/persistent endodontic infections.

STUDY DESIGN

Microbial samples were taken from 50 cases with primary and 50 cases with secondary/persistent endodontic infections. Microbiologic techniques were used for culture and identification. The DNA extracted from the samples was analyzed for the presence of the target species using species-specific primers.

RESULTS

Culture and polymerase chain reaction (PCR) identified the species in 23 and 77, respectively, of 100 root canals. Culture yielded the test organism in 19 of 50 (38%) of root canal samples from primary and in 4 of 50 (8%) from secondary/persistent infections. PCR yielded the test organisms in 41 of 50 (82%) and 36 of 50 (72%) of the, respectively, primary and secondary/persistent root canal infections studied.

CONCLUSION

Gemella morbillorum was identified more frequently in primary endodontic infections than in secondary/persistent ones. A higher frequency of the target species was detected by PCR than by culture.

[Necrotizing pneumonia due to Gemella morbillorum in an immunocompetent patient]

BACKGROUND

Gemella morbillorum is an anaerobic to aerotolerant Gram positive coccus. It is considered a member of the normal upper respiratory tract flora including the oropharynx and also the gastro-intestinal and female genital tract. However severe infections are reported like endocarditis, septic shock and septic arthritis, more often in immunocompromised hosts. It is an infrequently isolated organism and a rare cause of pulmonary or pleural infections.

CASE REPORT

We report a case of necrotizing pneumonia due to Gemella morbillorum in a 45-years-old Melanesian, smoker patient. The presentation was subacute with a four month history of loss of appetite, progressive weight loss and cough without fever. Initial presentation seems to be a malignant disease. The positive diagnosis has been established on the results of BAL fluid and the protected specimen brush samples. It was an immunocompetent patient presenting dental inflammation but not oral infection. Further management included intravenous administration of amoxicillin during two weeks. We recommended oral antibiotic treatment for another six weeks. After two months the patient was reevaluated. The CT scan showed no evidence of persistent infection. The HR CT scan will reveal multiple kystic bronchiectasies not seen on the first CT scan.

CONCLUSION

Gm can be found endoscopic samples. Gemella morbillorum can be responsible of community-acquired pneumonia in immunocompetent host.