GENERAL INFORMATION corynebacteria:

Diphtheria has become exceptional in rich countries, but it persists in poor countries. Although rare in France and because of gravity, it is essential that the bacteriology laboratories are able to identify Corynebacterium diphtheriae.With advances in bacteriology, it is recognized that other corynebacteria can be pathogenic opportunists during hospitalization in the long term, especially in immunocompromised patients.

I – CLASSIFICATION AND NOMENCLATURE:

Most taxonomists agree to restrict the kind

Corynebacterium to bodies:

– Whose wall contains

– Meso-diaminopimelic acid

– Arabinose, galactose

-the range of relatively short mycolic acids (22 to 38 carbon atoms)

-unGC DE51 59%;

– Who are mostly facultative anaerobes.

There are relationships between corynebacteria (human and animal), mycobacteria and Nocardia (ac. Meso-diaminopimelic, arabinose, galactose, ac. Mycolic).

The limits of the genus Corynebacterium are quite blurred, with some representatives of the group of “coryneform” including Brevibacterium (ac. Mesodiaminopimelic (+), GC 60-64%), Arthrobacter, Microbacterium …).

It has recently been proposed to leave the genus Corynebacterium species C. haemolyticum, C. equi, C. pyogenes;C. haemolyticum becoming Arcanobacterium haemolyticum, C. equi: Rhodococcus equi, and C. pyogenes: Actinomyces pyogenes.

Similarly, it was proposed to classify a number of coryneform Oerskovia in the genre.

II – HABITAT AND DISTRIBUTION:

C. diphtheriae is a strictly human bacterium that colonizes the nasopharynx essentially more rarely the skin. There are healthy carriers. C. xerosis and C. pseudodiphtheriticum are normal inhabitants of the man.

Other species may be pathogenic for both man and animals.

C. ulcerans and C. bovis were found in cows (mastitis), C. pseudotuberculosis in sheep and horses, C. pyogenes in cats, sheep and pigs, C. equi in horses, pigs and cats. Other corynebacteria and coryneform can be found in the waters (C. aquaticum), soil and plants.

Corynebacterium diphtheriae:

HISTORY:

– In 1821, Bretonneau individualized diphtheria and contagious reported the appearance.

– In 1883, the bacillus Klebs described in the false membranes of tonsillitis and diphtheria in 1884, Loeffler isolates the bacteria and shows its experimental pathogenicity for guinea pigs.

-In 1888, Roux and Yersin show that heat labile toxin is secreted into the culture medium by C. diphtheriae and that this toxin, inoculated animals, reproduces general manifestations of diphtheria.

– In 1890, Behring and Kitasato immunize animals with modified toxin and showed serum neutralizing power vis-à-vis animals of diphtheria toxin.

– In 1923, Gaston Ramon prepares a vaccine with a toxin modified by heat and formaldehyde, diphtheria toxoid.

I – Pathophysiology:

C. diphtheriae preferentially replicates in the upper layers of some epithelia: nasopharynx, larynx rarely or skin; one can also find it in the conjunctiva.

The proliferation is accompanied by lymphadenopathy satellites, but does not cause bacteremia.

Enzymes and the produced toxin, locally causing an inflammatory reaction with formation of a thick exudate: false membrane. The toxin diffusing away from the seat of bacterial multiplicaiton, through blood, will reach different tissues, blocking protein synthesis in target cells, and can result in complications (cardiac, nerve, …).

II – PATHOGENICITY:

A – Experimental:

A number of animals are susceptible to C. diphtheriae, or rather its toxin. This is the case of the monkey, horse and rabbit, but the guinea pig is the animal of choice.

The subcutaneous inoculation of 1 ml of pure culture of C. diphtheriae a guinea pig, causes the rapid appearance of local edema, gelatinous, hemorrhagic fibrin-rich bacilli followed by lymphadenopathy and death animal in 2 to 4 days. At autopsy, there is an absence of germs in the blood and organs, and hemorrhagic adrenalitis due to the toxin. The intradermal injection of toxin produced necrotic effect. Toxin also has a cytotoxic effect observed in vitro on human or animal cells.

B – Natural:

Transmission of C. diphtheriae man to man is:

– Usually through direct salivary droplets (sick or healthy carriers) or by contact with contaminated wounds.

– More rarely indirectly through objects, dust or contaminated food. This is a seed resistant several months on objects or false dried membranes.

In diphtheria, we recognize the entanglement of two types of events:

– Local: related to the multiplication of the germ at the front door,

– General: toxinogenesis charge related to malignant forms.

1. Diphtheria “common”:

The role of the toxin remains in the background here, however, that rapid diagnosis provided allows the establishment of an early serum therapy without delay.

Pharyngeal Location: it is the common diphtheria angina or angina false membranes (fibrin clumps infiltrated with polymorphonuclear and diphtheria bacilli).

After a silent incubation of 2 to 5 days, the occurrence of an insidious invasion period marked by a general malaise, a temperature (38 ° C) and dysphagia precedent that the status period characterized by:

– Pharyngitis with false membranes: coated white, greyish, adherent false membranes, consistent, reproducing in situ within hours after removal (extensive). These false membranes can invade the tonsils, but also the pillars of the veil, and sheathed uvula “thimble”; angina but is not always so typical (erythematous pultaceous, pseudo-gangrenous).

– A discreet coryza and moderate cervical lymph nodes, sore throat accompany this false membranes.

– Functional signs (dysphagia) and general remain in the background (pallor, tachycardia, mild fever).

In this form, if serum therapy is instituted rapidly changing will be benign. However in the absence of treatment and sometimes outright, we are faced with severe or malignant diphtheria.

Other locations meet:

– Laryngeal form or “croup” is either primary or associated with pharyngeal form; it typically comprises three phases: Phase dysphonic (modification of cough and voice), the dyspnea phase and the asphyxial phase.

– Over few other locations (nasal, conjunctival, esophageal, skin, vaginal.

2. “malignant” Diphtheria:

They are characterized by the importance of:

– Local signs (confluent false membranes, mucosal bleeding, foul whale)

– Regional signs (sero-bloody nasal discharge, cervical lymphadenopathy giving an aspect of proconsular neck)

– General signs.

Death can occur within hours or after a temporary improvement, later as part of Marfan syndrome secondary (with signs cardiovascular, renal, gastrointestinal)

Complications due to the toxin can occur more or less late in the course of diphtheria. These are:

– Myocarditis which follows a severe or malignant diphtheria, sometimes a common form later processed;

– Paralysis favored by age (adult), the severity of the initial diphtheria, and lack or delay of serum therapy. In chronological order is observed: the paralysis of the soft palate (2nd week), paralysis of accommodation, paralysis of limbs, others paralysis can be observed (cranial nerves …).

The severity of the infection is related to the delay in initiating treatment, but also with the existence of more toxigenic strains than others (gravis strains) and associated infections (strep) …

3. Cutaneous diphtheria:

Until the last few years, the pure cutaneous diphtheria with necrotic pseudomembrane formation at the injury had been reported especially in the tropics, or these forms are not exclusive to developing countries; countries such as Germany, Holland, Sweden, for Europe and also Canada and the US have reported (in 1975, the USA 56% of all strains of C. diphtheriae were isolated from samples skin); we must think of these forms in France knowing that sometimes C. diphtheriae is associated with S. aureus or S. pyogenes.

III – CHARACTER BACTERIOLOGICAL:

A – morphological characters:

C. diphtheriae is in the form of bacillus 1-8 um / 0, 3-0, 8 pm, straight or slightly curved, with rounded ends or bulging (dumbbells aspects or clubs).

Most toxigenic strains called “gravis” contain bacilli shorter than the others (intermedius and mitis).

These are Gram-positive bacilli but are readily bleached by the alcohol.

We can specifically stain metachromatic granules (Albert coloring of Emst-Neisser, Del Vecchio) or body Babes-Ernst, contained in the swollen ends of bacilli; these granules are reserves polyphosphates or grain volutin.

These bacilli are characterized by their group, they are observed in the false membranes (aspects letters or small clusters) or cultural (large clusters of pins in packages, palisades, Chinese, Roman numeral or capital letters: L, M, N, V, …).

This grouping method is explained by incomplete separation at the time of the bacterial division because there is an attachment point between the bacilli. Forms of granular or branched involution can be observed in the aged cultures.

Structure of C. diphtheriae

We distinguish:

a) a wall formed of four layers visible by electron microscopy: Irregular outer layer, inhomogeneous core layer made of two dense layers separated by a layer of low electron density.

Type 1 peptidoglycan contains meso-diaminopimelic acid with interpeptidique bridge

D-alanyl-diaminopimelic acid.

Also contained within the walls:

– A polysaccharide or arabinogalactan (0 Lautrop antigen) that cross-react with Mycobacterium and Nocardia.

– Fatty acids, and corynémycoliques corynémycoliniques acids

– Toxic glycolipid or “Cord Factor”

b) at the surface, there are K proteinaceous antigens, which play a role in immunity and hypersensiblilité, and which are used for the serological classification.

c) cytoplasm containing:

– Lipids associated with many mesosomes

– Metachromatic granules or grains volutin

– Unusual organelles in toxigenic strains.

B – Cropping characters:

C. diphtheriae is an aerobic-anaerobic facultative species having a catalase, cytochromes a, b, c, but no oxidase.

Culture is obtained at an optimum temperature of 36-37 ° C and a pH optimum at 7.4.

Culture can be obtained on ordinary media, but growth:

– On enriched medium is better (blood agar medium Mueller-Hinton serum coagulated beef or horse, Loeffler medium or coagulated bovine serum), where colonies of 1-3 mm are observed, smooth , greyish, creamy in 16 to 24 hours

– On blood agar reveals a beta hemolysis that allows a first orientation

– On selective media, may be necessary. Conventionally used potassium tellurite containing media on which C.diphtheriae give black colonies reducing tellurium tellurite; but culture on blood agar nalidixic acid gives good results.

The colonies are visible in 16 hours on enriched media and in 48 hours on some selective media.

They look different on blood agar containing tellurite, depending on the strains:

– Gravis, large colonies “R” jagged (central nipple)

– Intermedius, smooth or rough small colonies

– Mitis, large colonies “S” curved and shiny.

If for growing the strains are fairly undemanding (push factors: oleic acid, carbon and energy source, variable growth factors with strains), they are for toxinogenesis where cystine and glutamic acid are essential. Other amino acids and involved a small acidification (maltose), agitation and especially the iron concentration (optimal rate 0.14 ug / ml).

There is a correlation between the iron porphyrin and toxin production (available, for good toxinogenesis, empirical backgrounds, semisynthetic or synthetic).

If the bacterium is resistant to the absence of air, it is destroyed by heat, light, antiseptics and antibiotics. Moreover, it is concerned with the phenomenon of antibiosis, its development is inhibited by various bacterial species (for example Staphylococci).

C – biochemical characters:

For a diagnosis of C. diphtheriae, it is important to distinguish this species from other bacteria “coryneform” frequent in the nasopharynx of normal individuals.

The mere possession of a catalase and nitrate reductase is not sufficient to rule out these other species (Table I).

The study of carbohydrate metabolism is important; can use special media, liquid media enriched with serum (as the medium of HISS); there fermentation without gas production from glucose, dextrin, galactose, maltose. There is no attack sucrose, lactose mannitol.

The study of protein metabolism provides additional information: urease (-) (searched on the middle of Lange) indole (-), gelatinase (-) and HS (+).

There are reports of non-diffusible hemolysin, a neuraminidase.

D – Bacteriophages:

n is a large number of carriers or lysogenic strains defective phages.

A phage typing system was developed with 22 phage types. Studies have focused on bacteriocins or corynécines, and bactériocinotypie was proposed.

E – antigenic characters:

The antigenic structure of C. diphtheriae is heterogeneous. A distinction is heat stable polysaccharide antigens 0 (group) and K labile protein antigens (type).

Antigenic studies are discordant according to the authors and have not led to an international nomenclature.

IV – DIPHTHERIA TOXIN:

Diphtheria toxin is a bacterial toxin that has been the most studied. Its structure and the cellular and molecular mechanisms of its action are among the best known.

Toxin production by C. diphtheriae is related to the state of the lysogeny

strains harboring the carrier beta phage Tox gene. This double-stranded bacteriophage DNA is integrated in the form of prophage in the bacterial chromosome. Non-lysogenic strains (Tox-) do not produce toxin but can be virulent.Infected with bacteriophage Tox + they synthesize and excrete the toxin.

Toxinogenesis is a function of the iron content of the culture medium, it is optimal when the concentration is low.There is a repressor encoded by the bacterial genome that would associate active iron acting as a corepressor.

This was partially purified repressor is a protein containing iron in the presence of this metal, binds to DNA.

Diphtheria toxin is an exotoxin protein of approximately 58 kDa whose gene has been cloned in E. . al The nucleotide sequence was determined and translated; and the sequence of 535 amino acids is known. Under the action of the trypsin, the toxin is hydrolyzed into two fragments A and B, these two polypeptides are joined by a disulfide bridge. A fragment (about 21 kDa) NH2 terminal has enzymatic activity. Fragment B (about 37 kDa) COOH terminal binds to the cellular receptor. The first fragment contains the signal sequence involved in secretion of the toxin by the bacterium. The B-chain has a region rich in hydrophobic amino acids responsible for the insertion of the toxin into the endosomal membrane and therefore the passage of the chain from the endosome to the cytoplasm.The 148th amino acid is probably the seat of the active site.

The black region in the COOH-terminal, is positively charged and recognizes receptors on the surface of susceptible cells. In the white region, fragment A, to NH2-terminal, is the active part of the molecule and is masked if the toxin is intact. The dotted area is the hydrophobic portion of the molecule.

Diphtheria toxin acts as an enzyme. It inactivates elongation factor EF2 essential component in protein synthesis which allows the translocation of polypeptidyl t-RNA acceptor site A at ribosome P donor of the eukaryotic cell. Toxin catalyzes the transfer of ADP-ribose EF2 of NAD by the following formula:

NAD + + EF2 -> ADP-ribosyl-Nicotinamide EF2 + + H + H-1.

(Active) (inactive)

Antibodies directed against the fragment inhibit the action of the toxin (ADP ribosylation) in an in vitro translationsystem. In contrast, antibodies directed against the fragment B, inhibit the action on the cells, but not on the ribosomes.

So diphtheria toxin is a very active specialized molecule whose enzymatic action is brought by the fragment A. A single molecule is lethal to the cell. Alters protein synthesis in a few hours.

In 1989, Chang showed that diphtheria toxin was causing DNA damage related to nuclease activity and resulted in cytolysis is not simply the result of an inhibition of protein synthesis.

Titration of the Diphtheria Toxin

H can be achieved in vivo and in vitro.

In vivo:

– Determination of lethality (minimum lethal dose DMM; 50% lethal dose, LD50)

– Neutralization of lethality (L +, LO)

– Neutralization of dermo-necrotic power in the guinea pig

– Titration cell cultures

In vitro:

– Initial flocculation (Ramon techniques, Dean and Webb; determining the flocculant dose LF)

– Medium agar precipitation.

V – BACTERIOLOGICAL DIAGNOSIS:

Bacteriological diagnosis of diphtheria is based on the isolation of C. diphtheriae is the direct diagnosis (Figure 2).

A – samples:

The throat swab for research of C. diphtheriae should be performed before any angina false membranes, but like diphtheria sore throats are sometimes atypical angina in false membranes may have other causes that it is important to seek parallel and systematically (fuso-spirillaire association, angina pyogenic, candidiasis, infectious mononucleosis, malignant blood diseases …).

The sampling must be conducted under visual control and before treatment:

– The false membranes collected at the swab or the clamp in the pharynx (or larynx when tracheostomy)

– Swab on the outskirts of the false membrane (amygdala, sailing, uvula)

– More rarely nasal swab, skin or conjunctival edema fluid, depending on the clinical picture.

Sampling must be sent to the laboratory immediately before drying; it must have at least two swabs (direct examination and culture).

B – Direct examination:

We proceed on the smears

– In a conventional Gram staining, optionally Gram with prolonged fading looking bacilli evocative morphology.

– A Ernst-Neisser staining for research corpuscles metachromatic.

– Immunofluorescence test is reported by some authors.

Pressed by the clinician, which requires rapid diagnosis, the microbiologist can at best indicate at this stage “presence” or “absence” of bacilli diphtérimorphes on direct examination, knowing that the vision of such bacilli correspond mostly in latitudes C. pseudodiphtheriticum or C. xerosis well as C. diphtheriae. The clinician should not wait for bacteriological results, if there is clinical suspicion it will start without delay specific treatment without waiting for culture results.

C – Culture:

This is an important step. We have described the rapid technological giving a presumptive diagnosis in 4 to 5 hours, swab dipped in clotted serum in blood … tellurium (Folger techniques, Manzullon of Sohier). They can not replace traditional techniques with crops on two types of environments.

Cultures on rich media (Loeffler medium or Mueller-Hinton blood agar or default) give a culture in 12 to 18 hours.

Cultures on selective media, especially the backgrounds tellurium blood (Clauberg, Hoyie) or agar-cystine-tellurite on which C. diphtheriae give black colonies (but also some diphtérimorphes or streptococci) and failing to blood agar nalidixic acid or nalidixic acid / colistin. The resistance of C. diphtheriae. And other Corynebacteria fosfomycin may be useful, the blood agar plates can be made ​​selective by addition of a fosfomycin disc (200 ug).

After incubation for 18 to 48 hours the colonies is observed, performs a Gram optionally metachromatic staining and a catalase search (if the media does not contain blood). Suspicious colonies, an identification is made ​​gallery (nitrate reductase attack sugars, urea hydrolysis) to differentiate C. diphtheriae other corynebacteria (Table I). A recently marketed gallery (API-Coryne) uses 20 characters.

It is essential to plant along broth (rich mid brain heart type) which then will realize the experimental pathogenicity.

A serotyping, phage typing, or bactériocinotypie can be performed on strains of C. diphtheriae in specialized laboratories.

Recently, Rappuoli could, by a hybridization technique, to obtain a genomic classification of the strains, allowing a very fine epidemiologic analysis and perhaps a dissociation toxinogenesis and virulence factors.

D – power toxigenic Search:

H is essential to prove that the isolated strain of Corynebacterium is a C. diphtheriae toxin producer.

This search can be performed in two ways:

in vivo:

– Or by the detection of the lethality by inoculation into guinea-pigs (subcutaneously by inoculating a culture broth to an unprotected about 300 g guinea pig and another guinea pig serum 250 receiving units diphtheria 2:00 before injection; the unprotected animal dies within 2 to 4 days). It is necessary to do the autopsy of the animal (visceral edema, hemorrhage of the adrenal).

– By seeking dermo-necrotic power after intradermal injection shaved on the sides of a guinea pig.

in vitro:

– Gel immunoprecipitation reaction (Elek Test). Parallel were seeded on the surface of the agar medium the strain to be studied between two reference strains (Tox + and Tox-), then depositing a perpendicular strip of filter paper soaked with diphtheria antitoxin serum (Figure 3). We observe the occurrence of precipitation arcs which, if they are specific, have to join the arcs observed with Tox + strain. The playback time is 1 to 6 days.

E – Indirect diagnosis:

II is no serodiagnosis for bringing a subsequent diagnosis of diphtheria.

By cons, we can measure antitoxic immunity and non-antimicrobial. It may be:

Passive: transplacental (infants less than 6 months) obtained by serum therapy

(Transient) active: due to a natural infection, typical or occult, or obtained through vaccination.

Immunity can be tested by the determination of serum antitoxin, Schick: intradermal injection of 0.1 ml of diphtheria toxin produces a local inflammatory reaction (more than 1 cm in less than 36 hours) in subjects n ‘having no antitoxin; injection of 0.1 ml intradermally toxin in an immunized subject does not cause reaction.

VI – ANTIBIOTIC SENSITIVITY:

Antibiotics have little effect on the course of the disease, but the treatment of the entourage and carriers can limit the spread of germs. The realization of a susceptibility is important because antibiotic resistance have been reported recently.

Is used for susceptibility testing, or determination of MICs, the middle of Mueller-Hinton supplemented with 5% sheep blood. For some intermedius or mitis strains are used in trypticase soy medium, supplemented with 10% fetal calf serum.

C. diphtheriae is sensitive to penicillin, erythromycin and the majority of antibiotics active against Gram-positive organisms; However, strains resistant to erythromycin, clindamycin, tetracyclines have been encountered.

Thus, 86% of Indonesian strains and 5% of African strains resistant to tetracycline. A plasmid bearing the resistance of C. diphtheriae erythromycin has been described.

VII – TREATMENT – PROPHYLAXIS:

Everything about with suspected diphtheria should be rushed to hospital.

A – Curative treatment:

It is based on three essential elements:

– Serum therapy: it remains the indispensable treatment, it must start as early as possible, as soon as the diagnosis is suspected without waiting for bacteriological results. This is an emergency therapy. It must contain a single injection, maximum immediately (IM or SC) of 2 000 to 5 000 units per kg with a maximum of 120 000 units.

– Antibiotics: systematically associated with penicillin G or erythromycin (50 mg / kg / day for 15 days) depending on the situation of local resistance.

– Strict bed rest for several weeks.

Depending on the clinical presentation, we will use specific treatments: croup (tracheotomy, corticosteroids), symptomatic treatments (rehydration, …), treatment of myocarditis, paralysis …

B – Preventive treatment:

It is mainly based on vaccination with tetanus toxin is

detoxified with formalin 4% C and heat (39 to 45 ° C for 1 month).

The vacination is mandatory in France. It includes three successive injections 1 month apart, followed by a booster at 1 year and then every 5 years.

The vaccine is also available in combination DT, DT cock, cock DT polio.

Vaccine reactions are minimal.

There are temporary cons-indications (eczema, pyoderma, acute, recent tuberculin reactions) or permanent (serious chronic diseases, tuberculosis, neoplasia). In fact the only real cons-indication is severe nephropathy.

Found after 5 years 70% of protected subjects and 50% after 10 years.

Recently a synthetic diphtheria vaccine was obtained. It consists of:

– A peptide fragment at the junction of the two fragments A and B of diphtheria toxin, it is a loop of 16 amino acids (MW 1600) synthesized in vitro antigen component,

– A carrier molecule “carrier” made of a synthetic peptide chain poly-D-alanine-poly-L-lysine,

– A synthetic adjuvant and muramyl dipeptide.

Tests on animals show immunogenicity.

Other collective measures are to be observed in cases of diphtheria:

– The declaration of diphtheria is compulsory (6)

– This disease requires: isolation of the patient, current disinfection and late disease, screening and treatment of carriers in the entourage, school crowding to the patient for 30 days after clinical recovery and the 7-day entourage if not properly vaccinated.

Despite these measures the diphtheria bacillus, and diphtheria have not completely disappeared. A recent survey on porting to Greece showed that 0.8% of children were carriers. Between 1979 and 1983, 363 cases of diphtheria were recorded in Europe, 0.2 cases per year per million inhabitants.

Each year, the number of identified diphtheria than 100 cases for Turkey and 1,000 cases for the USSR. In France, diphtheria has almost disappeared (Figure 1), however there were 12 cases between 1984 and 1987. In Sweden, where vaccination coverage was higher than 95% an outbreak has occurred.In the US, we consider that only 50% of adults are properly vaccinated. These facts should encourage vigilance both in terms of vaccination (recall in adults) that diagnosis.

OTHER corynebacteria:

The incidence of opportunistic infections in coryneform bacteria is growing while the diphtheria decrease.

Some species are well experienced in immunocompromised subjects. These are: C. xerosis, C. pseudodiphtheriticum (C. hofmannii), C. equi (Rhodococcus equi), C. matruchotii (Bacterionema matruchotii) as well as the groups defined by the

CDC as D2, A4, G2 …

Other species are isolated during infections in non-immunocompromised. These are: C. ulcerans, C. haemolyticum (Arcanobacterium haemolyticum), C. pseudotuberculosis (C. ovis) and C. minutissimum.

There is no question of reviewing the pathology induced by these species, only a few points will be developed.

C. ulcerans. : it may be responsible for exudative pharyngitis and pseudo-diphtheria tables. The strains can produce two toxins of which is neutralized by diphtheria antitoxin, the second would be a phospholipase D.

C. pseudotuberculosis (C. ovis): this species was reported in granulomatous lymphadenitis and pneumonia.

C. xerosis: it was reported that germ in valve endocarditis in bacteremia and pneumonia in immunocompromised subjects.

Pseudodiphtheriticum C. (C. hofmannii): this species has been the source of infections on prosthetic and a fatal infection in a renal transplant.

C.jeikeium (eg JK Group) was found in various septicemic infections, peritoneal, genitourinary, meningitis and endocarditis.

It is present in the normal state on the skin and can colonize up to 25-35% of hospitalized patients. After staining, this species appears as Gram positive bacilli sometimes very short evoking streptococci. Antimicrobial susceptibility reveals multiple resistance, some strains are only sensitive to vancomycin.

C. minutissimum: can be isolated from the skin in cases of erythrasma.

C. pyogenes (Actinomyces pyogenes) – C. haemolyticum (Arcanobacterium haemolyticum) C. haemolyticumdescribed in pseudo-membranous diphtheria exudates but also in sepsis and various abscesses.

It appears likely that this group of bacteria is called to have an increasing role in pathology. They are selected by the antibiotic, favored by instrumentation (catheters) and immunocompromised courses. It is important to be able to recognize as well as C. diphtheriae keeps a special place historically and in terms of gravity.