Why streptococcus is in chain form

This photo shows the focal redness and swelling of the lower leg, usually accompanied by warmth and tenderness, characteristic of focal cellulitis. The clinician has marked the border of the cellulitis with a pen, to facilitate recognition of spread or resolution. Note the line of redness extending up the thigh due to lymphangitis. Necrotizing fasciitis Necrotizing Soft Tissue Infection Necrotizing soft tissue infection is typically caused by a mixture of aerobic and anaerobic organisms that cause necrosis of subcutaneous tissue, usually including the fascia.

This infection Inoculation originates through the skin or bowel. Formerly known as streptococcal gangrene and popularized as the flesh-eating bacteria, the same syndrome may also be polymicrobial, involving a host of aerobic and anaerobic flora, including Clostridium perfringens. Polymicrobial infection is likely when the source is the bowel eg, after intestinal surgery, bowel perforation, diverticulitis, or appendicitis. Symptoms of necrotizing fasciitis begin with fever and exquisite localized pain out of proportion to physical findings; pain increases rapidly over time and is often the first and sometimes only manifestation.

Diffuse or local erythema may be present. Thrombosis of the microvasculature causes ischemic necrosis, leading to rapid spread and disproportionally severe toxicity.

Shock and renal dysfunction are common. Mortality is high, even with treatment. Streptococcal toxic shock syndrome Streptococcal toxic shock Toxic shock syndrome is caused by staphylococcal or streptococcal exotoxins. Patients are usually otherwise healthy children or adults with skin and soft-tissue infections.

The mechanism by which certain strains of GABHS cause delayed complications is unclear but may involve cross-reactivity of streptococcal antibodies against host tissue. Rheumatic fever Rheumatic Fever Rheumatic fever is a nonsuppurative, acute inflammatory complication of group A streptococcal pharyngeal infection, causing combinations of arthritis, carditis, subcutaneous nodules, erythema It has become much less common in developed countries but is still common in developing countries.

One of the most important reasons for treating GABHS pharyngitis strep throat is to prevent rheumatic fever. Poststreptococcal acute glomerulonephritis Rapidly Progressive Glomerulonephritis RPGN Rapidly progressive glomerulonephritis is acute nephritic syndrome accompanied by microscopic glomerular crescent formation with progression to renal failure within weeks to months. It is most common among children, occurring 1 to 3 weeks after infection.

Nearly all children, but somewhat fewer adults, recover without permanent renal damage. PANDAS syndrome pediatric autoimmune neuropsychiatric disorder associated with group A streptococci refers to a subset of obsessive disorders or tic disorders in children that is thought to be exacerbated by GABHS infection.

Certain forms of psoriasis Psoriasis Psoriasis is an inflammatory disease that manifests most commonly as well-circumscribed, erythematous papules and plaques covered with silvery scales.

Multiple factors contribute, including Rapid antigen-detection tests that can detect GABHS directly from throat swabs are available ie, for point-of-care use. Many tests use enzyme immunoassay, but more recently, tests using optical immunoassay have become available.

Thus, positive results can establish the diagnosis, but negative results, at least in children, should be confirmed by culture. Because streptococcal pharyngitis is less common among adults and adults are unlikely to have poststreptococcal complications, many clinicians do not confirm a negative rapid screening result in adults by culture unless use of a macrolide is being considered; in such cases, culture with susceptibility testing to detect macrolide resistance should be done.

Demonstrating antistreptococcal antibodies in serum during convalescence provides only indirect evidence of infection. Antistreptococcal antibody tests are not useful in diagnosing acute GABHS infection because antibody first develops several weeks after GABHS infection begins and a single high antibody titer is more likely to reflect a long antecedent infection.

Antibodies are most useful in diagnosis of poststreptococcal diseases, such as rheumatic fever and glomerulonephritis. Both titers may remain elevated for several months, even after uncomplicated infections.

A single titer greater than the upper limit of normal suggests an antecedent streptococcal infection or high streptococcal endemicity in the community.

For completeness in difficult cases, any one of the other tests antihyaluronidase, antinicotinamide adenine dinucleotidase, antistreptokinase can also be used. Penicillin given within the first 5 days for symptomatic streptococcal pharyngitis may delay the appearance and decrease the magnitude of the ASO response.

Patients with streptococcal pyoderma usually do not have a significant ASO response but may have a response to other antigens ie, anti-DNAase, antihyaluronidase. Antibiotics shorten the course in young children, especially those with scarlet fever, but have only modest effect on symptoms in adolescents and adults. However, antibiotics help prevent local suppurative complications eg, peritonsillar abscess , otitis media, and rheumatic fever. However, some streptococcal strains appear to have in vitro tolerance to penicillin ie, significantly decreased bactericidal effect of penicillin ; the clinical significance of such strains is unclear.

A single injection of benzathine penicillin G , units IM for small children 27 kg or 1. These enterococci produce a yellow pigment that can be detected on several different media. The pyruvate utilization test aids in the differentiation of E. This test is also used to help differentiate between E. The tellurite tolerance test aids in the differentiation of E. Table 8. Phenotypic characteristics used for the identification of Enterococcus species and some physiologically related species of other gram-positive cocci.

Lactococcus strains identified to the genus level by the tests listed in Table 1. Identification of the Lactococcus species is accomplished by performing the tests listed in Table 9.

The majority of lactococcal isolates identified from human sources resemble L. An examination of the information provided in Table 9 will show that it is not always possible to differentiate between these two species by phenotypic characteristics.

Table 9. Differentiation of Lactococcus species. Gemella species are identified to the genus level by the tests listed in Table 1. The Gemella species can be differentiated by the tests listed in Table The acid from mannitol and sorbitol tests should be performed as previously described except the incubation period may have to be longer up to days.

Because of the slow growth on blood agar plates by the Gemella species, these strains may be confused with the nutritionally variant streptococci. In such cases, it is necessary to perform the satillitism test to confirm the identity of NVS.

In some cases the species cannot be determined by the phenotypic characteristics listed in Table If this occurs the culture should be reported as a Gemella species, not further identified. Table Differentiation of Gemella species. Mal, Man, Sbl, and Suc positive means acid production from maltose, mannitiol, sorbitol, and sucrose.

VP, Voges-Proskauer reaction. Among the pediococci, only P. Only one strain of Tetragenococcus , T. Identification of the pediococci is accomplished by demonstrating the unknown strain to be vancomycin resistant, PYR negative, LAP positive, and does not form gas from glucose in MRS broth Table 1.

The majority of strains of pediococci isolated from humans have been bile-esculin positive, deaminated arginine and have streptococcal group D antigen in Lancefield extracts.

All strains have failed to form acid in lactose broth, and most have grown very slowly if at all in NaCl broth. These reactions are similar to Streptococcus anginosus and Streptococcus equi nus. Vancomycin resistance has not been identified in any strain of streptococci. Thus the vancomycin screening test should prevent this mis-identification. Tetragenococcus resemble the Pediococcus except in their sensitivity to vancomycin. Identification of Pediococcus and Tetragenococcus species. Pediococcus sp.

Leuconostoc Like the lactococci, the Leuconostoc were once not thought to cause human infections. Like the lactococci, Leuconostoc s grow at 10C but very poorly if at all at 45C.

Four Leuconostoc species, L. The reactions listed in Table 12 can be used to identify the species. These strains may be confused with S.

Both L. The latter two species are differentiated by growth in 6. The Aerococcus , Helcoccus, Dolosigranulum and Tetragenococcus all have the cellular arrangement of clusters and tetrads. All will grow in 6. Identification of Aerococcus species, Helcococcus kunzi , Dolosigranulum pigrum , Tetragenococcus solitarius. There is only one species in the genus Globicatella.

Globicatella sanguinis closely resembles the aerococci, streptococci, and enterococci phenotypically. The major differentiating characteristic between Globicatella and the aerococci is the cellular arrangement of the cells in the Gram stain.

Globicatella forms chains while the aerococci form tetrads and clusters. The colonial morphology of Globicatella strains most closely resembles the viridans streptococci.

However, these strains are readily distinguished with a negative leucine aminopeptidase reaction LAP and growth in the presence of 6. The biochemical characteristics of the most recently identified strains of A. The cellular arrangement from growth in broth can be used to differentiate the two as A.

Fermentation of inulin can be useful as the majority of G. The other key reactions for bile esculin, esculin and hippurate are of limited value in separating these two species since the PYR is a variable reaction for G. The LAP test is also useful in distinguishing enterococci from Globicatella strains.

The two species are phenotypically similar in the PYR, bile esculin, growth in 6. The incorporation of the PYR and LAP tests in the identification scheme, as well as molecular studies have confirmed that many of the strains that are now Globicatella were previously reported as Streptococcus uberis-like. The key test for differentiation of the streptococci from Globicatella is the positive LAP reaction. The majority of strains for both species are PYR positive, grow in 6.

Acid is not produced from glycerol and sorbose for both species. Phenotypic differences between G. Phenotypic Characteristics of Dolosigranulum pigrum , Ignavigranum ruoffiae , Facklamia sp. See Table 1 for general characteristics of these bacteria. Tests are performed as described elsewhere, see index. Potentially useful tests included in the Rapid ID system for differentiating unusual gram positive cocci. Skip directly to site content Skip directly to page options Skip directly to A-Z link.

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Abstract IT was observed that in young broth cultures, Streptococcus faecalis enterococcus grows in marked chains which later break up rather abruptly; the chains can be maintained by spinning young cultures and resuspending the cells in fresh medium.

References 1 Weissenbach, R. Google Scholar 2 Webb, M. Google Scholar Download references. View author publications. Rights and permissions Reprints and Permissions.

Copy to clipboard. ORAM Nature The inoculated tube is incubated at 30C in ambient air and incubated until good growth is observed, in most cases 24 to 48 h is sufficient. Reading and Interpretaion Strains that are motile will show growth outward to the edge of the tube and downward toward the bottom of the tube. Negative strains will only show growth in the line of the stab. Limitations Do not place the motility test at 37C.

Some strains become nonmotile at 37C but are motile at temperatures 25C to 30C. Top of Page 6. Some bacteria can grow in 6. Growth in broth containing 6. Heart infusion base contains 0. To make the test easier to read we add 0. Inoculum A fresh inoculum grow in Todd Hewitt broth is preferred.

Alternatively, a small loopful of growth from a blood agar plate may be used. Reagents and Materials 6. This formulation is identical to the modified 6.

Comparison of several laboratory media for presumptive identification of enterococci and group D streptococci. Procedure One or two colonies or one or two drops of an overnight broth culture is inoculated into the broth containing 6. If 2 or 3 days were required for sufficient inoculum then the NaCl tolerance test should be incubated 10 to 14 days.

In some cases most enterococci the test is positive after overnight incubation. Reading and Interpretaion When most strains grow the dextrose is fermented and the broth changes from purple to yellow color. However, the color change is not required for a positive test.

If there is an obvious increase in turbidity, which indicates growth, without a change in color this is also read as a positive test. Limitations Other base media brain heart infusion and trypticase soy have been used for determining NaCl tolerance of the enterococci and viridans streptococci but these bases have not been tested with the other genera.

Quality control. Enterococcus faecalis strain SS and Streptococcus sanguinis strain SS are used for positive and negative reactions respectively. Inoculum Isolated alpha-hemolytic colonies suspected of being pneumococci. Tap the disk to insure that it stays on the media after the plate is inverted. Reading and Interpretaion If a 6 mm disk is used, a zone of inhibition of at least 14 mm in diameter is considered positive for identification of pneumococci.

A zone of inhibition between 6 and 14 mm in diameter is considered questionable for identification of pneumococci and a bile solubility test should be performed. Bile soluble strains with optochin zones of inhibition between 6 and 14 mm are considered pneumococci, those strains that are not bile soluble with the same zone sizes are not considered pneumococci. Limitations Cultures do not grow as well in normal atmospheres and larger zones of inhibition can cause misidentification.

Quality Control Each new lot and shipment of optochin AP disks is tested for positive and negative reactions. The purpose of the pigmentation test is to aid in the identification of E. These enterococci produce a yellow pigment that can be detected on several different media. Reagents and Materials cotton swab Procedure Use a cotton swab to pick up a 50 mm smear of bacteria.

Examine the swab and smear for a bright yellow color. Reading and Interpretaion A pale to bright yellow color is interpreted as positive. A cream, white, or grey color is negative. Limitations The test should be repeated on the culture again after 48 h of incubation if there is any question about the results at 24 h.

Quality Control E. Top of Page Pyridoxal Requirement Test Vitamin B6 Principle Nutritionally variant streptococci Abiotrophia and Granulicatella are usually very fastidious and will grow only on supplemented media or enriched chocolate agar.

These strains require pyridoxal for growth while non-NVS do not. A final concentration in broth of 0. An alternative to performing the pyridoxal requirement test is the satellite test. Inoculum The cultures are typically received on chocolate agar slants.

Reagents and Materials 0. Procedure Add a drop of the 0. Inoculate both plates with the suspected NVS strain. Reading and Interpretaion If growth is observed on the plate containing pyridoxal and not on the plate without pyridoxal the strain is a NVS. Limitations Quality Control There are no guidelines for quality control of the reagents or the media. Each lot of pyridoxal can be tested for supporting the growth of a known NVS strain. More than 1 day of incubation may be necessary for more fastidious genera such as the Gemella e, alloiococci, and helcococci.

The LAP test is usually done simultaneously. Enterococcus faecalis strain SS is used for positive reaction and Streptococcus sanguinis strain SS is used for a negative reaction. Bromthymol blue is added to the media as an indicator which results in a color change from blue-green to yellow. Inoculum A fresh inoculum grown in Todd Hewitt broth is preferred.

Fastidious strains may be incubated for 14 days. Reading and Interpretaion A positive reaction is indicated by the development of a yellow color. If the broth remains green or greenish yellow, the test result is negative. A yellow color with only a hint of green is usually a positive reaction. Limitations Quality Control Quality control tests are determined for each new batch of prepared medium.

Top of Page Satellite Test SAT Principle Nutritionally variant streptococci Abiotrophia and Granulicatella are usually very fastidious and will grow only on supplemented media or enriched chocolate agar. The purpose of the SAT test is to determine if the unknown streptococcal strain is a nutritionally variant streptococci NVS. These strains require pyridoxal for growth.

An alternative to performing the SAT test is to test for the requirement of vitamin B6 pyridoxal. A single streak of Staphylococcus aureus ATCC is then made across the middle of the agar plate. Incubate the plate in a candle extinction jar or C02 incubator for 24 h or more. Reading and Interpretaion If the strain is a NVS growth will appear only adjacent to the staphylococcus streak, about 2 to 5 mm wide. Streptococci that are not NVS will grow over the entire surface of the agar plate.

Limitations Quality Control There are no quality control guidelines for testing the medium or the Staphylococcus strain for the satillitism test. When iodine is added to starch, it turns dark bluish-black. If starch has been hydrolyzed, then it is not available to react with the iodine and the area around the bacterial growth is clear.

This test can be used to differentiate some bacteria. A drop of Todd Hewitt broth bacterial suspension may also be used to streak the plate. Some strains may require longer incubation for sufficient growth. Reading and Interpretaion A clear zone surrounding the growth is positive test that the strain hydrolyzed starch. A deep purple to black or bluish color of the agar indicates that starch has not been hydrolyzed and thus a negative test. For negative tests the deep color develops in the agar right up to the growth.

Limitations Some fastidious strains show poor growth. Quality Control Each new batch of starch agar is quality control tested. Some fastidious strains may require longer incubation for growth. Examine the plate for levans and dextrans. A loop is used to scrape the colonies for viscosity or adherence. Reading and Interpretaion Some bacteria produce a levan as the extracellular polysaccharide.

The colonies appear very slimy, mucoidal and runny or as large gum drops on the agar. Some bacteria may produce dextrans in which the colonies are dry and adherent to the plate. The following strains are use for QC: Leuconostoc mesenteroides strain SS positive for slime production-levans , Streptococcus sanguinis SS positive for dextrans-adherent and Enterococcus faecalis strain SS negative for levans and dextrans.

Examine the broth for viscosity or a gel button. The broth appears very thick and slimey. Some bacteria may produce dextrans in which a gel button adhers to the bottom or sides of the tube.

There is only an increase in turbidity. The following strains are use for QC: Leuconostoc mesenteroides strain SS positive for slime production-levans , Streptococcus sanguinis SS positive for dextrans-adherent gel button and Enterococcus faecalis strain SS negative for levans and dextrans.

Very few catalase-negative gram-positive cocci will grow on this medium. The primary purpose of the tellurite tolerance test is aid in the differentiation of E. A drop of Todd Hewitt broth bacterial suspension may also be used to streak the slant. Reagents and Materials Tellurite agar slants 0. Reading and Interpretaion Tolerance a positive result is indicated whenever black colonies form on the surface. Typical and variant strains of E. Some strains of E.