In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner membrane (cytoplasmic), and an outer membrane.
Haemophilus ducreyi are fastidious gram-negative coccobacilli bacteria.
The HACEK organisms are a group of fastidious Gram-negative bacteria that are an unusual cause of infective endocarditis, which is an inflammation of the heart due to bacterial infection. HACEK is an abbreviation of the initials of the genera of this group of bacteria: Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella. The HACEK organisms are a normal part of the human microbiota, living in the oral-pharyngeal region.
A broad-spectrum antibiotic is an antibiotic that acts on the two major bacterial groups, Gram-positive and Gram-negative, or any antibiotic that acts against a wide range of disease-causing bacteria. These medications are used when a bacterial infection is suspected but the group of bacteria is unknown or when infection with multiple groups of bacteria is suspected. This is in contrast to a narrow-spectrum antibiotic, which is effective against only a specific group of bacteria. Although powerful, broad-spectrum antibiotics pose specific risks, particularly the disruption of native, normal bacteria and the development of antimicrobial resistance. An example of a commonly used broad-spectrum antibiotic is ampicillin.
A coccus is any bacterium or archaeon that has a spherical, ovoid, or generally round shape. Bacteria are categorized based on their shapes into three classes: cocci (spherical-shaped), bacillus (rod-shaped) and spiral. Coccus refers to the shape of the bacteria, and can contain multiple genera, such as staphylococci or streptococci. Cocci can grow in pairs, chains, or clusters, depending on their orientation and attachment during cell division. In contrast to many bacilli-shaped bacteria, most cocci bacteria do not have flagella and are non-motile.
Haemophilus influenzae is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria are mesophilic and grow best at temperatures between 35 and 37 °C.
Bacterial pneumonia is a type of pneumonia caused by bacterial infection.
Haemophilus is a genus of Gram-negative, pleomorphic, coccobacilli bacteria belonging to the family Pasteurellaceae. While Haemophilus bacteria are typically small coccobacilli, they are categorized as pleomorphic bacteria because of the wide range of shapes they occasionally assume. These organisms inhabit the mucous membranes of the upper respiratory tract, mouth, vagina, and intestinal tract. The genus includes commensal organisms along with some significant pathogenic species such as H. influenzae—a cause of sepsis and bacterial meningitis in young children—and H. ducreyi, the causative agent of chancroid. All members are either aerobic or facultatively anaerobic. This genus has been found to be part of the salivary microbiome.
In microbiology, pleomorphism, also pleiomorphism, is the ability of some microorganisms to alter their morphology, biological functions or reproductive modes in response to environmental conditions. Pleomorphism has been observed in some members of the Deinococcaceae family of bacteria. The modern definition of pleomorphism in the context of bacteriology is based on variation of morphology or functional methods of the individual cell, rather than a heritable change of these characters as previously believed.
Betaproteobacteria are a class of Gram-negative bacteria, and one of the eight classes of the phylum Pseudomonadota.
Chromobacterium violaceum is a Gram-negative, facultative anaerobic, non-sporing coccobacillus. It is motile with the help of a single flagellum which is located at the pole of the coccobacillus. Usually, there are one or two more lateral flagella as well. It is part of the normal flora of water and soil of tropical and sub-tropical regions of the world. It produces a natural antibiotic called violacein, which may be useful for the treatment of colon and other cancers. It grows readily on nutrient agar, producing distinctive smooth low convex colonies with a dark violet metallic sheen. Some strains of the bacteria which do not produce this pigment have also been reported. It has the ability to break down tarballs.
Moraxella is a genus of gram-negative bacteria in the family Moraxellaceae. It is named after the Swiss ophthalmologist Victor Morax. The organisms are short rods, coccobacilli, or as in the case of Moraxella catarrhalis, diplococci in morphology, with asaccharolytic, oxidase-positive, and catalase-positive properties. M. catarrhalis is the clinically most important species under this genus.
Pasteurella multocida is a Gram-negative, nonmotile, penicillin-sensitive coccobacillus of the family Pasteurellaceae. Strains of the species are currently classified into five serogroups based on capsular composition and 16 somatic serovars (1–16). P. multocida is the cause of a range of diseases in mammals and birds, including fowl cholera in poultry, atrophic rhinitis in pigs, and bovine hemorrhagic septicemia in cattle and buffalo. It can also cause a zoonotic infection in humans, which typically is a result of bites or scratches from domestic pets. Many mammals and birds harbor it as part of their normal respiratory microbiota.
A bacillus, also called a bacilliform bacterium or often just a rod, is a rod-shaped bacterium or archaeon. Bacilli are found in many different taxonomic groups of bacteria. However, the name Bacillus, capitalized and italicized, refers to a specific genus of bacteria. The name Bacilli, capitalized but not italicized, can also refer to a less specific taxonomic group of bacteria that includes two orders, one of which contains the genus Bacillus. When the word is formatted with lowercase and not italicized, 'bacillus', it will most likely be referring to shape and not to the genus at all. Bacilliform bacteria are also often simply called rods when the bacteriologic context is clear.
Bacterial cellular morphologies are morphologies that are characteristic of various types bacteria and often a key factor in identifying bacteria species. Their direct examination under the light microscope enables the classification of these bacteria and archaea.
Spiral bacteria, bacteria of spiral (helical) shape, form the third major morphological category of prokaryotes along with the rod-shaped bacilli and round cocci. Spiral bacteria can be subclassified by the number of twists per cell, cell thickness, cell flexibility, and motility. The two types of spiral cells are spirillum and spirochete, with spirillum being rigid with external flagella, and spirochetes being with internal flagella.
ESKAPE is an acronym comprising the scientific names of six highly virulent and antibiotic resistant bacterial pathogens including: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. The acronym is sometimes extended to ESKAPEE to include Escherichia coli. This group of Gram-positive and Gram-negative bacteria can evade or 'escape' commonly used antibiotics due to their increasing multi-drug resistance (MDR). As a result, throughout the world, they are the major cause of life-threatening nosocomial or hospital-acquired infections in immunocompromised and critically ill patients who are most at risk. P. aeruginosa and S. aureus are some of the most ubiquitous pathogens in biofilms found in healthcare. P. aeruginosa is a Gram-negative, rod-shaped bacterium, commonly found in the gut flora, soil, and water that can be spread directly or indirectly to patients in healthcare settings. The pathogen can also be spread in other locations through contamination, including surfaces, equipment, and hands. The opportunistic pathogen can cause hospitalized patients to have infections in the lungs, blood, urinary tract, and in other body regions after surgery. S. aureus is a Gram-positive, cocci-shaped bacterium, residing in the environment and on the skin and nose of many healthy individuals. The bacterium can cause skin and bone infections, pneumonia, and other types of potentially serious infections if it enters the body. S. aureus has also gained resistance to many antibiotic treatments, making healing difficult. Because of natural and unnatural selective pressures and factors, antibiotic resistance in bacteria usually emerges through genetic mutation or acquires antibiotic-resistant genes (ARGs) through horizontal gene transfer - a genetic exchange process by which antibiotic resistance can spread.
Infectious coryza is a serious bacterial disease of chickens, which affects respiratory system, and it is manifested by inflammation of the area below the eye, nasal discharge, and sneezing. The disease is found all over the world, causing high economic losses, which are due to stumping off and reduction of egg production in case of laying chickens. The disease was discovered early 1930s by considering clinical signs.
Histophilus somni is a non-motile, gram-negative, rod or coccobacillus shaped, facultative anaerobe bacterial species belonging to the family Pasteurellaceae. Prior to 2003, it was thought Haemophilus somnus, Histophilus ovis, and Histophilus agni were three different species, but now are all classified as Histophilus somni. Histophilus somni is a commensal bacteria of mucous membranes of the upper respiratory tract and reproductive tract with a global prevalence and is found in cattle and other small ruminants. Histophilus somni is also a known causative agent that is a part of the Bovine Respiratory Disease (BRD) complex, which typically involves multiple pathogens residing together in biofilm environments. Histophilus somni may also cause Histophilosus symptoms and clinical presentation will depend on the tissue affected. When disease does occur, it can be difficult to catch in time and is often diagnosed on post mortem. This means that treatment often involves metaphylactic mass treatment or no treatment at all. This organism is more fastidious than others and requires knowledge for sample collection, storage and culture. Genomic studies related to this bacteria have enabled scientist to pin point antibiotic resistance genes.
