STAPHYLOCOCCUS: CHARACTERISTICS, MORPHOLOGY, METABOLISM - BIOLOGY - 2025

Staphylococcus is a genus belonging to the Staphylococcaceae family formed by gram-positive bacteria, characterized by having a cell wall that contains peptidoglycans composed of L-lysine and teicoic acid. They are cells without mobility, generally encapsulated or have limited capsule formation and do not produce spores.

Some species are selective for a specific host and niche, while others can reproduce in a greater diversity of habitats. They can be established in the host as residents or they can be transitory.

Staphylococcus aureus. www.flickr.com

They are commonly associated with the skin, skin glands, and mucous membranes of humans and other homeothermic animals. These organisms have also been isolated from a variety of animal products (such as meat, poultry, and dairy) and environmental sources (such as objects, soil, sand, dust, air, seawater, freshwater).

Some species have been described as opportunistic pathogens of humans and / or animals. Other species are an important component of the normal human microflora.

However, due to the increase in antibiotic-resistant strains, these species have become a problem in immunosuppressed patients, generating hospital infections.

Staphylococcus aureus is resistant to methicillin, with intermediate sensitivity and resistance to vancomycin, making them a public health problem. The World Health Organization includes this species in a list of pathogens with critical priority for the research and development of new antibiotics, due to its worrying resistance to antibiotics.

General characteristics

Metabolism

Staphylococcus bacteria are facultative anaerobes, but they grow faster and more abundantly under aerobic conditions, with the exception of anaerobic Staphylococcus aureus subspecies and Staphylococcus saccharolyticus.

They are generally catalase positive and oxidase negative. They can grow in a temperature range between 18 and 40 ° C and in media with 10% NaCl. They are chemoorganotrophs. Some species are mainly respiratory or mainly fermentative.

They can metabolize lactose or D-galactose through the D-tagatose-6-phosphate pathway or the Leloir pathway, depending on the particular species. They use carbohydrates and / or amino acids as sources of carbon and energy.

For most species, the main product of glucose fermentation is lactic acid, although under aerobic conditions the main products are acetic acid and CO ₂.

Taxonomy and phylogeny

According to comparative studies of 16S rRNA sequence, the genus Staphylococcus belongs to the Bacilli class of the phylum Firmicutes. It is a monophyletic genus and is well differentiated from other related genera.

It is one of four genera in the Staphylococcaceae family, along with Jeotgalicoccus, Macrococcus, and Salinicoccus. It is closely related to other genera such as Macrococcus, Enterococcus, Streptococcus, Lactobacillus, and Listeria.

The genus Staphylococcus includes 37 species and more than 17 subspecies. These can be separated into groups according to the presence of coagulase (a protein that coats the surface of bacteria with fibrin when it comes into contact with blood) and the susceptibility to novobiocin.

Morphology

Staphylococcus are spherical-shaped bacteria, measuring 0.5 to 1.5 mm in diameter. They can be seen separately, in pairs, tetrads or in short chains, which are divided into one or more planes, forming groups in the form of grape clusters, from which their name comes (staphyle = bunch of grapes, kokkos = coconut, grain or berry).

This cluster-shaped architecture differentiates Staphylococcus from Streptococcus, which generally grow in a chain.

Pathogeny

-Coagulase positive species

Species of the genus Staphylococcus that test positive for coagulase (S. aureus, S. intermedius, S. delphini, S. schleiferi subsp. Coagulans, and S. hyicus) are considered potentially serious pathogens.

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S. aureus can cause a variety of infections in humans including boils, impetigo, toxic epidermal necrolysis, pneumonia, osteomyelitis, acute endocarditis, myocarditis, pericarditis, enterocolitis, mastitis, cystitis, prostatitis, cervicitis, cerebritis, meningitis, bacteremia, syndrome of toxic shock and abscesses in muscle, skin, urogenital tract, central nervous system, and various intra-abdominal organs.

Additionally, staphylococcal enterotoxin is involved in food poisoning. Methicillin-resistant strains of S. aureus constitute a major clinical and epidemiological problem in hospitals.

S. aureus is also capable of causing infections in a variety of other mammals and birds. The most common natural infections include mastitis, synovitis, arthritis, endometritis, boils, suppurative dermatitis, and septicemia.

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S. intermedius is an opportunistic dog pathogen that can cause otitis externa, pyoderma, abscesses, reproductive tract infections, mastitis, and purulent wounding.

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S. hyicus has been implicated as the etiologic agent of infectious exudative epidermitis and septic polyarthritis in pigs, skin lesions in cattle and horses, osteomyelitis in poultry and cattle, and has occasionally been associated with mastitis in cattle.

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S. delphini has been linked to purulent lesions on the skin of dolphins. S. schleiferi subsp. coagulans is associated with the external auditory meatus in dogs suffering from otitis externa of the ear.

-Coagulase negative species

Coagulase negative Staphylococcus species constitute an important component of the normal human microflora. Its role in causing hospital infections has been recognized and well documented over the past two decades.

The increase in infections by these organisms has been correlated with the increase in the use of permanent medical prostheses and the increase in immunocompromised patients in hospitals.

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Among the coagulase negative staphylococci, S. epidermidis is the species most associated with nosocomial diseases due to its greater pathogenic and adaptive potential.

This species has been implicated in bacteremia, prosthetic and native valve endocarditis, osteomyelitis, pyroarthritis, mediastinitis, permanent pacemaker infections, vascular grafts, cerebrospinal fluid shunts, orthopedic and urinary prostheses and joints, and tract infections including urethritis and pyelonephritis.

Other coagulase negative species have been associated with infections in humans and animals. S. haemolyticus is the second most common species in hospital infections in humans.

It has been implicated in native valve endocarditis, septicemia, peritonitis, and urinary tract infections, and is occasionally associated with wound, bone, and joint infections.

S. haemolyticus has been associated with mastitis in cattle.

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S. caprae has produced cases of infective endocarditis, bacteremia, and urinary tract infections.

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S. lugdunensis has been implicated in native and prosthetic valve endocarditis, sepsis, brain abscess, and chronic osteoarthritis, and infections of soft tissue, bone, peritoneal fluid, and catheters.

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S. schleiferi has been associated with human brain empyema, osteoarthritis, bacteremia, wound infections, and infections with cat skin infections.

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S. capitis has been associated with endocarditis, septicemia, and catheter infections.

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S. hominis has been associated with human endocarditis, peritonitis, septicemia, and arthritis.

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S. cohnii has been isolated from urinary tract infections and arthritis.

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S. chromogenes is commonly present in the milk of cows suffering from mastitis, although its role as an etiological agent is questionable.

References

1. Foster T. (1996). Chapter 12: Staphylococcus. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston, Galveston, Texas.
2. Kloos, WE (1980). Natural populations of the genus Staphylococcus. Annual Review of microbiology, 34: 559-592.
3. Seija, V. (2006). Genus Staphylococcus. In Subjects of Bacteriology and Medical Virology. Second edition. Department of Bacteriology and Virology Institute of Hygiene. Montevideo.
4. Staphylococcus. (2018, September 29). Wikipedia, The Free Encyclopedia. Consultation date: 03:52, October 5, 2018 from es.wikipedia.org
5. Vos, P., Garrity, G., Jones, D., Krieg, NR, Ludwig, W., Rainey, FA, Schleifer, K.-H., Whitman, W. (2009). Bergey's Manual of Systematic Bacteriology: Volume 3: The Firmicutes. USES.