Journal of Veterinary Science & Medical Diagnosis ISSN: 2325-9590

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Review Article, J Vet Sci Med Diagn Vol: 11 Issue: 8

Review on Streptococcus Species

Negesa Gedefa Areda*

Department of Veterinary Epidemiology, Ambo University, Guder, Ethiopia

*Corresponding Author: Negesa Gedefa Areda
Department of Veterinary Epidemiology,
Ambo University,
Tel: + 251922967177;
[email protected]

Received date: 19 May, 2022, Manuscript No. JVSMD-22-64210; Editor assigned date: 23 May, 2022, PreQC No. JVSMD-22-64210 (PQ); Reviewed date: 06 June, 2022, QC No. JVSMD-22-64210; Revised date: 18 July, 2022, Manuscript No. JVSMD-22-64210 (R); Published date: 25 July, 2022, DOI: 10.4172/2325-9590.100034.

Citation: Areda NG (2022) Review on Streptococcus Species. J Vet Sci Med Diagn 11:8.


Zoonotic infections caused by Eubacterium species are neglected in spite of the actual fact that frequency and severity of outbreaks accumulated dramatically in recent years. This might flow from to non-identification since various species area unit usually not thought about in human medical diagnostic procedures. On the opposite hand, associate degree increasing human population concomitant with associate degree increasing demand for food and also the accumulated range of companion animals favor conditions for host species adaptation of animal streptococci. This review aims to administer an outline on eubacteria zoonoses with target medicine and pathogenicity of 4 major animal disease species, Eubacterium genus Canis, and Eubacterium equi sub. Zooepidemicus, Eubacterium iniae and Eubacterium suis. Eubacterium infections area unit still one amongst the vital issues facing up to date medication. Despite associate degree increasing range of diplococcus vaccinations, incidences of malady connected to the present pathogen’s infection reside a similar level that is said to a perpetually increasing range of infections caused by non-vicinal serotypes.

Keywords: Epidemiology; Infections; Outbreaks; Streptococcus, Zoonotic


Streptococci are spherical or ovoid cells, organized bound or pairs. They’re no motile, non-spore forming and enzyme negative with complicated nutritionary necessities. All are facultative anaerobic, most can grow in air however some need to feature greenhouse gas for growth. All species fails to scale back nitrate [1]. Several species of streptococci are members of the commensals of small flora, bacterium that are gift on tissue layer surface of humans and animals and customarily cause hurt.

However, this species will cause serious infection. The diseases caused by the streptococci vary from dental carries, inflammatory disease, and inflammatory disease to life threatening conditions like necrotizing fasciitis and infectious disease. On the opposite hand, an increasing human population concomitant with an increasing demand for food and also the inflated range of companion animals favor conditions for host species adaptation of animal streptococci. This review aims to offer an outline on true bacteria zoonosis with concentrate on medicine and pathogenicity of major animal disease species.

Literature Review

Classification of Streptococcus

The earliest try at differentiating the streptococci was in all probability created in 1903 by Shottmuller world health organization used nutrient agar to differentiate strains that were beta-hemolytic from people who weren't. Before 1933, fermentation and tolerance were the sole take a look at used for differentiating several of the streptococci species. In 1933, Lancefield reported the technique of demonstration specific saccharide cluster matter related to the beta haemolytic strains. In 1937, Sherman projected a theme for putting the streptococci in to four classes. These classes were organized by haemolytic reaction, cluster saccharide antigens, and phonotypical test (mainly fermentation and tolerance test) [2].

Sherman’s four division were the pathology division, the drinkable division, the variance division and therefore the enterococci. The pathology division includes the beta –hemolytic strains with outlined cluster antigens (A, B, C, E, F and G). This division of the streptococci isn't appreciably completely different from that of today’s identification systems supported sero-grouping. Sherman’s viridians division enclosed strep species that weren't beta-hemolytic, weren't tolerant to high pH growth, weren't salt tolerant and failed to grow at 10℃. This cluster continues to be notable these days because the viridians streptococci, and plenty of a lot of species are additional to the current classification.

Lancefield group: The Lancefield serological grouping system for identification of streptococci is based on the immunological differences in their cell wall polysaccharides (groups A, B, C, F, and G) or lipoteichoic acids (group D) [3]. The group a carbohydrate antigen is composed of N-acetyl-b-Dglucosamine linked to a polymeric rhamnose backbone. Confirmation of S. pyogenes is done by highly accurate serological methods, such as the Lancefield capillary precipitin technique and the slide agglutination procedure, which utilize standardized grouping antisera [4].

Hemolysis: A) Hemolysis preliminary identifications based on the type of hemolysis produced on blood agar plates. Agar plate containing sheep erythrocytes are used rather than human erythrocytes as human blood usually contains anti streptococcal antibodies. There are three types of hemolytic patterns; B) β hemolytsis in which a clear zone of hemolysis surrounds the streptococcal colonies indicating complete lysis of the red blood cells. In β hemolytic zones, there are no red cell outlines remaining; C) Alpha hemolysis is in which there is partial hemolysis of the red blood cells. Typically, the zones surrounding these streptococcal colonies has a brown or green colorization. Since the blood cells are not totally destroyed, they can observed microscopically. In α hemolytic zones, the red cells are clearly outlined; D) Gammahemolysis: In this, there are no zones of hemolysis surrounding the streptococcal (Figure 1).

Figure 1: Classification of Streptococcus species based on their hemolytic capability.

New species: Pathogenic species of the Streptococcus genus had been remoted and defined as early as via way of means of the quilt of the nineteenth century subsequently [5,6], new species had been located and defined: Hardie and Whiley in 1997 suggested approximately forty species [7]. An instance is S. tigurinus, a species located earlier than few years via way of means of Swiss researchers, and gift withinside the oral hollow space as physiological flora; however, it can be chargeable for endocarditis and meningitis [8].

Another species is S. urinalis a case of bacteremia because of this turned into defined in a 60-year-antique guy with urethral stricture history. S. australis, defined to start with as one of the oral streptococci additionally seemed to be an etiological issue withinside the case of meningitis [9]. An instance of the species chargeable for more than a few human and animal infections (chargeable for the spontaneous fermentation of dairy merchandise in Africa) turned into S. infantarius subsp. infantarius (Sii) belonging to S. bovis/S. equinus, displaying 80% similarity to the S. thermophilus genome [10].


Pathogenicity of the Streptococcus

Bacteria of the Streptococcus genus encompass a massive number (>a hundred species) of microorganisms colonizing human and animal mucous membranes. They arise as physiological plant life withinside the oral hollow space and intestines of people and animals. In addition, they regularly inhabit the skin, throat, and higher respiration tract. However, severa streptococci arise as opportunistic pathogens, inflicting infections withinside the case of susceptible immunological reaction of the host frame they occupy. Pathogenic streptococci can be divided into 3 groups: The ones typically inflicting infections and commensal and epizootic species which purpose disorder signs and symptoms beneathneath targeted conditions [11].

Typical pathogenic species encompass S. pneumoniae, with S. pyogenes and S. agalactiae, S. Suis, S. Canis. According to the estimations of the WHO, each year, pneumonia ensuing particularly from S. pneumoniae pastime causes 1.2 million deaths of youngsters more youthful than five years of age all around the world, which constitutes 18 % of all deaths on this age group [12].


Typing of GAS lines primarily based totally on T and M proteins are of epidemiological interest. Nine With a GAS vaccines turning into a fact now than ever before, facts on the superiority of M sorts in a network has received excellent significance [13]. This is pretty special from what one sees in non-endemic temperate international locations wherein some M sorts are answerable for maximum of the invasive GAS infections [14].


Many species of streptococci are contributors of the commonsals of microflora, microorganism which can be gift on mucosal floor of human beings and animals and normally reason harm. However, this species can reason extreme infection. The sickness because of the streptococci variety from dental carries, pharygtis, and sore throat to existence threatening situations consisting of necrotizing fasciitis and meningitis.

Zoonotic importance of Streptococcus

Streptococcus pneumonia: According to the estimations of the World Health Organization (WHO), approximately 1.2 million kids’ elderly under 5years die every 12 months due to pneumonia, for which the primary informal element is S. pneumoniae, and this constitutes 18 % of all deaths on this age institution [15]. S. pneumoniae infections have brought on scientists to be looking for to expand vaccines aimed toward lowering the occurrence of such infections. It is understood that the primary element underlying microorganism pathogenicity is the so-referred to as polysaccharide envelope which turned into the premise of the department of the S. pneumoniae microorganism into over ninety serotypes [16,17]. Seventeen immunogenic proteins had been recognized in this microorganism’s floor and the incidence of thirteen of them is depending on the host age.

Streptococcus pyogenes: The other most common cause of diseases and mortality worldwide are invasive GAS infections. S. pyogenes are responsible for about 700 million infections per year, which result in the death of about 500,000 people [18]. This bacteria is equipped with flagella referred to as antigen T. However, unlike the flagella observed in S. pneumoniae , the presence of the flagella in S. pyogenes causes decreased invasiveness and pathogenicity of the strain. Despite the similarity of both kinds of flagella in general, i.e., the main genetic structure, fine differences in particular genes enable functional diversity between the encoded proteins. The flagella of the M1T1 strain increase the adhesive abilities of the proteins towards the endothelium; however, they concurrently constitute a molecular pattern for phagocyte ary cells of the host, and, thus, are subject to higher activity and faster elimination from an organism.

Streptococcus equi subsp. Zooepidemicus:Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) is a beta-haemolytic group C streptococcus able to colonize the upper airways of horses and produce diverse clinical manifestations in domesticated animals, including respiratory tract infections, mastitis and meningitis [19]. S. zooepidemicus rarely causes human infection, and the mechanism is supposed to be zoonotic transmission by direct contact with infected or colonized animals or the consumption of unpasteurized milk products. This streptococcus has been associated with a wide range of severe human infections, including cellulitis, pericarditis, toxic shock syndrome, endovascular infections, pneumonia, septicaemia, meningitis, arthritis and spondylodiscitis [20].

Necrotizing myositis is a very rare and potentially lethal infection, constituting the most severe form of Necrotizing Soft Tissue Infections (NSTI). Monomicrobial NSTI is most often caused by Streptococcus pyogenes (S. pyogenes), and frequently associated with septic shock and high mortality rates [21]. NSTI caused by S. zooepidemicus was recently documented in a dog shortly after subcutaneous vaccination [22]. But to our knowledge, human NSTI caused by S. zooepidemicus has not been reported previously. Zoonotic transmission to man from asymptomatic horses colonized with S. zooepidemicus in the upper airways has previously been described.

Streptococcus suis: Streptococcus suis is one of the maximum crucial pathogens with inside the porcine enterprise inflicting septicemia, meningitis and lots of different infections [23]. In addition, it's miles and rising zoonotic agent chargeable for septicemia without or with septic shock, meningitis and different much less not unusual place infections in people. During the remaining decade, the range of pronounced human instances because of S. suis has dramatically increased, and whilst maximum sporadic human instances of contamination appear like because of near occupational touch with pigs/beef products, in particular in Western countries (farmers, veterinarians, butchers, meals processing workers, etc.), and instances pronounced has increased [24].

In fact, in a few countries, the overall populace is at risk. However, an replace at the distribution of the specific serotypes and Series Types (STs), as decided with the aid of using Multilocus Series Typing (MLST), of lines chargeable for infections in each pigs and people from round the sector have now no longer been currently compiled. Complete evaluations have already included the specific virulence elements implicated withinside the pathogenesis of the contamination because of this crucial pathogen [25]. S. Sui (non-beta-hemolytic; Lancefield companies R, S and T) is a pathogenic or commensal organism normally related to pigs. There are at the least 35 serotypes of S. suis with various virulence.

Streptococcus Iniae: Streptococcus iniae is a rising zoonotic pathogen; such infections normally arise thru accidents related to getting ready entire sparkling fish for cooking. Infections with S. iniae were sporadic however remain pronounced with new instances [26]. Carrier fish were implicated in fish-to-fish trans-project of S. iniae and those providers can be chargeable for human contamination due to the fact fish with overt symptoms and symptoms of ailment are unmarketable. Soft tissue accidents that arise for the duration of the practise of sparkling fish from moist markets normally bring about bacteremic cellulitis of the hand, accompanied with the aid of using >1 of those conditions: endocarditis, meningitis, arthritis, sepsis, pneumonia, osteomyelitis, and poisonous shock [27]. Infections are dealt with with a direction of antimicrobial capsules together with penicillin, ampicillin, amoxicillin, cloxacillin, cefazolin, and/or gentamicin, doxycycline, and trimethoprim/ sulfamethoxazole over a length of 1 to numerous weeks, relying on the character of the contamination [28].

Streptococcus canis: Streptococcus canis is a Lancefield organization G beta-hemolytic streptococcal species that's in particular determined as an animal colonizer and pathogen. S. canis (betahemolytic; Lancefield organization G) is an opportunistic pathogen determined in puppies and different species. This member of the largecolony- forming Lancefield organization C and G Streptococcus (GCGS) organization turned into formally hooked up as a wonderful taxon in 1986 (following preceding research which confirmed that the Lancefield organization G streptococci remoted from animals and human beings have been biochemically divergent and will constitute wonderful species [29]. Although S. canis may be a part of the lady reproductive tract and the tonsillar and ear microbiota of cats and puppies [30].

It is likewise a vital pathogen for those species and infects an extensive variety of different home and wild animals [31]. S. canis is the maximum not unusual place streptococcal species determined in canine infections, being diagnosed in instances of dermatitis, otitis externa, pneumonia, infective endocarditis, and person septicemia. This species has additionally been implicated in fetal or neonatal septicemia, main to abortion or neonatal death, respectively and in each dog and tom cat necrotizing fasciitis and streptococcal poisonous surprise syndrome. S. canis can be transmitted among one of a kind animal species residing in proximity and has been liable for outbreaks of medical and subclinical mastitis with bacterial losing in milk in livestock herds and in pets residing in shelters [32].

Streptococcus bovis: Streptococcus bovis reasons eleven to 14% of infective endocarditis instances and money owed for 24% of endocarditis episodes because of streptococci. S. bovis endocarditis is extra not unusual place in human beings over 60 years old (41), inflicting a excessive mortality rate (45%), in comparison to that for non-S. bovis endocarditis (25%) (26). There is a well-documented excessive prevalence of Gastrointestinal (GI) cancers in sufferers with S. bovis bacteremia and/or endocarditis [33].

The excessive prevalence of S. bovis endocarditis in human beings older than 60 years and the boom withinside the growing old populace itself manner that S. bovis has turn out to be an an increasing number of vital pathogen. S. bovis incorporates the Lancefield organization D antigen shared through contributors of the enterococci. There are biotypes of S. bovis. The majority of S. bovis biotype I strains (the classical S. bovis strains) produce extracellular glucan from sucrose, ferment mannitol, and hydrolyze starch, while S. bovis biotype II strains (the variant S. bovis strains) are typically bad for those traits [34].

Although S. bovis may be divided into biotypes, there had been few researches correlating sickness with biotype. A look at searching on the affiliation among underlying gastrointestinal most cancers and bacteremia resulting from S. bovis biotypes I. The S. bovis organization (non-beta-hemolytic; Lancefield organization D) carries S. bovis, S. equinus, S. gallolyticus, S. infantarius, S. pasteurianus and S. lutetiensis [35].

Streptococcus Agalactiae: GBS, S. agalactiae, has become an equally important microorganism which is responsible for miscarriages, and may also constitute a risk of premature birth and neonate infection in the form of sepsis, pneumonia, or meningitis. In the United States, GBS infection is diagnosed in about 5,000 neonates per year, and mortality caused by this microorganism is estimated at 5%. The studies focused on GBS constitute a very important element allowing the development of methods for the prevention of diseases caused by this microorganism, since no commercial vaccine protecting against S. agalactiae infections has been created so far.

The modified strains were characterized by poorer adhesion to surfaces covered with saliva and by weakened biofilm formation. Confocal and scanning microscope images confirmed that the biofilm in these strains was thinner and looser compared to the biofilm formed by nonimpaired strains. Forty-four proteins, the expression of which is higher in a situation of proper biofilm formation, and 13 proteins of weakened expression were identified using electrophoretic techniques [36].


Bacitracin susceptibility: In many laboratories bacitracin susceptibility test is the method of choice to identify GAS. This test has a sensitivity of >95%, is only a presumptive test and is not recommended since group G and C streptococci can give false positive results. Batch to batch variation may occur in the commercial discs and therefore it is essential to test each batch for quality control with known GAS strains. If this is done regularly, one can resort to GAS identification by this method [37].

Group identification: Grouping can be done on the organism isolated from throat cultures or extracts prepared directly from throat cultures. Numerous methods are available in the laboratory for this, of which the time tested Lancefield’s hot-acid extraction technique and Fuller’s formamide extraction method are the most widely used.

Interpretation of cultures: In countries where streptococcal infections are endemic, pharyngeal carriage of GAS is a common event. Therefore isolation of GAS from throat cultures should be interpreted with caution, especially in a child with viral pharyngitis. In such instances, determination of four-fold rise in titers of antistreptococcal antibodies can differentiate bona-fide GAS pharyngitis from GAS carrier state [38].

Serological diagnosis: Historically, determination of Anti- Streptolysin O antibodies (ASO) had been the mainstay of confirming a diagnosis of GAS pharyngitis as well as RF. Demonstration of a significant or four-fold rise in titer on paired serum samples taken at an interval of 7 to 14 days apart will indicate an ongoing or an acute infection. On the other hand, presence of GAS in throat in the absence of a significant rise in antibodies indicates a carrier state and no GAS infection

Clinical signs: The most common streptococcal species infections, being identified includes dermatitis, otitis external, pneumonia, infective endocarditis, and adult septicemia. The disease may be transmitted between different animal species living in proximity and has been responsible for outbreaks of clinical and subclinical mastitis with bacterial shedding in milk in cattle herds and in pets living in shelters.

Prevention and treatment

Treatment: When the bacterial cause was identified and the antibiotic susceptibility pattern was confirmed, the patient was further treated with a combination of penicillin and clindamycin. Clindamycin has been shown to be superior to beta-lactam-antibiotics in two observational studies on streptococcal NSTI, and furthermore, to reduce mortality of severe GAS infections including toxic shock [39]. Hence, although ST 364 did not belong to S. pyogenes, the combination of penicillin and clindamycin appeared to be the most sensible antibiotic regimen, in line with the recommendations for treatment of beta-haemolytic NSTI in the IDSA-guidelines [40].

But the failure of penicillin to treat severe invasive streptococcal infections successfully is attributed to the phenomenon that a large inoculum reaches stationary phase quickly and penicillin is not very effective against slow-growing bacteria [41]. The reason for this may be that IVIG provides neutralizing or protective antibody to the patient. Plasma from patients with severe invasive group A streptococcal infections who were given IVIG inhibited streptococcal superantigen-induced T cell proliferation and cytokine production [42]. All three streptococcal pyrogenic exotoxins, A, B, and C, were inhibited by the IVIG. The data suggested that a deficiency of neutralizing antibodies against the super antigens may increase the risk of developing disease [43].

Vaccination: Polysaccharide antigens are used in antipneumococcal vaccines. They are conjugated in the vaccines with proteins in order to enhance the immunological response, i.e., with respect to that which would occur during natural infection by bacteria within the polysaccharide envelope [44].

Recombinations occurring in this manner within the polysaccharide envelope enable the microorganism to circumvent the barrier formed by the host’s immune system. Conjugation of these substances allows an effective immunization of children below 2 years of age, who are a reservoir of numerous opportunistic pathogenic bacteria as this stage of their lives [45].

Many types of S.pneumoniae vaccines are distinguished; however, 7-, 10-, and 23-valent vaccines are used the most often. 7 valent vaccines (Protein Conjugate Vaccine, PCV7) contains polysaccharide antigens which were found in seven serotypes of the microorganisms responsible for 80–95% of invasive pneumococcal infections [46-50]. The vaccine is the subject of further tests; however, a disadvantage attributed to it is its defense against only 6 of the 120 suggested serotypes of protein M [51-53].


Streptococcus has a lot of species which all of them were identified and understood well up to date. Therefore, numerous researches will be done to obtain new species and to identify their properties concerning their zoonotic importance. In addition, even though, different types of vaccines against Streptococci species have been created so far, and further research on bacterial strains has formed the basis for widening the list of antigens which may constitute a potential target for the activity of future generations of vaccines.


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