Aerobic and Facultatively Anaerobic Gram-Positive Cocci

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Enterococcus faecalis and Enterococcus faecium

Clinical Features

Urinary tract infections, peritonitis, bacteremia, endocarditis

Virulence Factors

Relatively avirulent

Aerobic and Facultatively Anaerobic Gram-Positive Cocci

Staphylococcus aureus

Clinical Features

Suppurative infections: impetigo, folliculitis, furuncles, carbuncles, wounds

Disseminated infections: bacteremia, endocarditis, pneumonia, empyema, osteomyelitis, septic arthritis

Toxin-mediated infections: toxic shock syndrome, scalded skin syndrome, food poisoning

Virulence Factors

Possess thick peptidoglycan layer, capsule, protein A, various toxins (cytotoxins, exfoliative toxins, enterotoxins, toxic shock syndrome toxin, Panton- Valentine leukocidin) and hydrolytic enzymes

Staphylococcus, coagulase-negative

Clinical Features

Wound infections, urinary tract infections, catheter and shunt infections, prosthetic device infections

Virulence Factors

Possess thick peptidoglycan layer and loose polysaccharide slime layer; Staphylococcus saprophyticus
produces high concentrations of urease

Streptococcus pyogenes (group A)

Clinical Features

Suppurative infections: pharyngitis, scarlet fever, sinusitis, skin and softtissue infection (impetigo,
erysipelas, cellulitis, necrotizing fasciitis), toxic shock–like syndrome; bacteremia

Nonsuppurative infections: rheumatic fever, glomerulonephritis

Virulence Factors

Capsule, M protein, M-like protein, F protein, pyrogenic exotoxins, streptolysin S and O, streptokinase,
deoxyribonuclease, C5a peptidase

Streptococcus agalactiae (group B)

Clinical Features

Neonatal disease (early onset, late onset): bacteremia, pneumonia, meningitis; postpartum endometritis, wound infection, skin and soft-tissue infection, urinary tract infections, pneumonia

Virulence Factors

Similar to group A but no capsule

Viridans streptococci

Clinical Features

Abscess formation; septicemia in neutropenic patients; subacute endocarditis; odontogenic infections; dental caries

Virulence Factors

Relatively avirulent

Streptococcus pneumoniae

Clinical Features

Pneumonia, sinusitis, otitis media, meningitis, bacteremia, endocarditis, spontaneous bacterial peritonitis, septic arthritis

Virulence Factors

Polysaccharide capsule; teichoic acid; immunoglobulin A protease; pneumolysin O

About Author

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Sagar Aryal, PhD

Dr. Sagar Aryal is a microbiologist, researcher, and science communicator from Nepal. He is also co-founder and Research Head of the Department of Natural Products at the Kathmandu Research Institute for Biological Sciences (KRIBS), where he leads research on natural product discovery and microbial biodiversity. Dr. Aryal earned his Ph.D. in Microbiology from Tribhuvan University, Kathmandu, Nepal, in 2025, supported by a DAAD Research Grant and a University Grants Commission (UGC) Nepal Ph.D. Fellowship. His research interests include Actinomycetes, Myxobacteria, microbial taxonomy, and natural products, particularly the discovery of bioactive compounds with potential pharmaceutical applications. He isolated and identified Nocardia nepalensis, a novel bacterial species from Nepal, contributing to understanding microbial diversity in the region. Dr. Aryal has published more than 16 research articles in international journals and contributed three book chapters to established academic publications. He has presented scientific research findings and developed international research collaborations through visits to more than 18 countries across Asia, Europe, North America, and Oceania. From 2023 to 2025, he served as the American Society for Microbiology (ASM) Young Ambassador to Nepal. Since December 2025, he has served as an Editorial Board Member of Scientific Reports, a Nature Portfolio journal. In recognition of his scientific contributions, Dr. Aryal received the NAST Science and Technology Youth Award 2025 from the Nepal Academy of Science and Technology. He previously received the Frs. Locke and Stiller Research Award (LSRA) for the 2017-2018 cycle from St. Xavier's College, Kathmandu, and a Nepal Academy of Science and Technology (NAST) Research Grant for 2017-2018. Alongside his scientific career, Dr. Aryal has more than 15 years of experience in blogging, content writing, and search engine optimization (SEO).