Staphylococcus genus

The genus *Staphylococcus* belongs to the family Staphylococcaceae. Clinically relevant species include *Staphylococcus aureus*, which comprises the subspecies *S. aureus subsp. aureus* and the anaerobic subspecies *subsp. Anaerobius*; *S. auricularis*, *S. capitis* (which includes the subspecies *S. capitis subsp. capitis* and the urea-splitting subspecies *subsp. ureolyticus*); *S. caprae*, *S. cohnii* (comprising *S. cohnii subsp. cohnii* and the urea-splitting subspecies *subsp. ureolyticum*); *S. delphini*, *S. epidermidis*, *S. haemolyticus*, *S. hominis* (which includes the human-specific subspecies *subsp. hominis* and the novobiocin-resistant septic subspecies *subsp. novobiosepticus*); *S. hyicus*, *S. intermedius*, *S. lugdunensis*, *S. saprophyticus* (comprising the saprophytic subspecies *sub-sp. Saprophyticus* and the bovine subspecies *subsp. bovis*); *S. schleiferi* (including the coagulase-positive subspecies *sub-sp. Coagulans* and the Schleiferi subspecies *subsp. Schleiferi*); *S. simulans*, *S. warneri*, *S. xylosus*, *S. lentus*, *S. lutrae*, *S. sciuri*, and *S. nepalensis*.

Staphylococcus bacteria are Gram-positive cocci (0.5–1.5 μm in size), arranged in clusters resembling grapes—either in pairs, groups of three to four cells, or irregularly—but they lack motility, do not form spores, and have no flagella; instead, they may produce a limited capsule.

With the exception of *Staphylococcus saprophyticus* and the anaerobic subspecies of *Staphylococcus aureus* (both of which grow anaerobically and are catalase-negative), most species are facultative anaerobes. They thrive best at temperatures between 35°C and 40°C and prefer a pH range of 7.0 to 7.5. These bacteria have relatively low nutritional requirements and can grow on media such as blood agar, nutrient agar, or brain-heart infusion agar. Typically, most staphylococci form colonies measuring 1–3 mm in diameter after 24 hours of incubation on non-selective media. However, the anaerobic subspecies of *S. aureus*, *S. saprophyticus*, *S. auricularis*, and *S. equi* grow more slowly; some may require 24 to 36 hours of incubation before visible colonies appear. Certain strains even depend on specific growth factors like carbon dioxide, heme, or vitamin K. Staphylococci are generally salt-tolerant, thriving well on 6.5% NaCl agar. On blood agar plates, their colonies usually exhibit medium size, smooth surfaces, central elevations, and neat edges. Notably, *S. aureus* and certain other staphylococcal species produce hemolysins, which result in distinct β-hemolysis zones visible after 24 hours of incubation on sheep or rabbit blood agar. Additionally, many staphylococcal strains produce pigments that are soluble in lipids under standard culture conditions, causing colonies to display yellow, orange-yellow, or orange hues—consistent with the observations shown in Figure 1.

Figure 1. Colony morphology of Staphylococcus on BA medium

Most staphylococci are part of the normal flora on skin and mucous membranes, but they can also act as opportunistic pathogens, leading to a variety of diseases. Staphylococcus is the most common type of pyogenic cocci, capable of causing infections such as wound infections, arthritis, mastitis, otitis externa, cystitis, and more. It can also trigger purulent skin lesions. Notably, most staphylococcal species have specific host associations, with certain diseases they may cause—details of which are listed in Table 1.

Table 1. Pathogenicity of Staphylococcus in Animals

Collect swabs from animal lesion sites for testing → Perform selective culture → Isolate and identify.

Currently, the most commonly used detection methods are bacterial isolation and culture, along with biochemical identification. To address this, our company has introduced the Vitek 2 compact fully automated biochemical identification system, which enables rapid and accurate strain identification. For any questionable results, we employ PCR-based nucleic acid testing to ensure absolute accuracy. Additionally, MALDI-TOF MS mass spectrometry directly analyzes microbial protein mixtures, allowing for swift strain identification—with results available in as little as 1 to 2 minutes. The introduction and implementation of these advanced detection methods have significantly enhanced both efficiency and precision, while also delivering more reliable test outcomes to our customers.

Antibiotic resistance among Staphylococcus species varies significantly, making it essential to base infection treatment on antimicrobial susceptibility testing. Methicillin-resistant Staphylococcus aureus (MRS) exhibits a broad spectrum of resistance and employs complex resistance mechanisms, posing considerable challenges for prevention and control. To effectively curb the spread of MRS, comprehensive preventive measures must be implemented, including rigorous disinfection, strict isolation protocols, proactive surveillance, timely and appropriate treatment, and careful management of antimicrobial use.

References

1. *National Clinical Laboratory Procedures, 4th Edition*

2. "Veterinary Microbiology, 6th Edition"

3. Application of MALDI-TOF MS Mass Spectrometry in Microbiological Research

4. Li Zongliang, Lai Chunyan, Liang Minfeng, et al. Clinical Distribution and Antibiotic Resistance Analysis of Staphylococcus Species[J]. Chinese Journal of Hospital Infection, 2015, 25(12):3. DOI: 10.11816/cn.ni.2015-135806.