Anaerobic necrotizing fasciitis

Although the term "necrotizing fasciitis" was coined by Meleney in 1924 to designate "gangrene related to haemolytic Streptococci"29, since Wilson (1952)30 it is now used for a sub-cutaneous infection spreading along the deep fascia, causing secondary skin lesions and sparing muscles until late stages of infection.

Many terms have been coined: necrotizing fasciitis31-34; clostridial cellulitis35,36; non-clostridial crepitant cellulitis37; synergistic necrotizing

cellulitis , ; and for penis and scrotum infections, Fournier's gangrene ' " .

1.3.2.1 Bacteriology

Although in his initial description, Meleney stated that beta-haemolytic Streptococci were isolated in all his patients29,42, since then - as sampling and bacteriological culture methods have improved - many authors30,43-46 have reported isolation of mixed flora where Streptococci are no longer the sole infective agents.

Rea & Wyrick46 made the finding of mixed flora an essential sign of this type of infection. Their opinion was that improper handing and transport of samples and difficulties with culture of anaerobes were the explanation for the absence of detection of mixed flora in these infections.

After their work, most of the published series reported mixed flora as the cause of necrotizing fasciitis. Mixed flora refers to the presence of both anaerobic and aerobic germs, as well as Gram-positive Cocci and Gramnegative bacilli. In 1977, Giuliano47 reported on a series of 16 patients in whom 75 strains of bacteria had been isolated. Streptococci were isolated alone or jointly with other bacteria in 15 of those 16 patients, Bacteroides in 10 and Peptostreptococcus in 8. This distribution is quite different from that reported by Stone & Martin38 or from our own series48, where no beta-haemolytic Streptococci were found. In both these series, Gram-negative anaerobic bacilli - mainly Bacteroides - were dominant, associated with Gram-negative aerobic bacilli and Enterococci (Table 2.2.4-3).

1.3.2.2 Etiology

Necrotizing fasciitis begins with a break in the skin or mucosa. It can be obvious, i.e., trauma, surgical wounds, infection of pre-existing lesions (arterial or venous ulcers, pressure ulcers, diabetic foot lesions, etc). Sometimes it is less obvious, idiopathic or goes unnoticed by the patient: e.g., skin abrasions, insect bites, etc.33,35,44,45.

Rare indisputable cases have been observed after uncomplicated tooth removals49; conventional surgery50; and after sub-cutaneous or intramuscular injections - mostly of corticosteroids or non steroidal antiinflammatory drugs. Septic injections carried out by IV drug abusers are a frequent point of entry51; here the bacteria are quite specific and include several germs of the oral flora such as Prevotella)52.

1.3.2.3 Clinical description

After the initial trauma, the phase of incubation is usually short (6 to 72 hrs), with discreet local signs in some cases: pale wound; local paresthesias; a feeling of fullness in the area, etc. Then an erythema appears. Soon after the area becomes swollen and painful. The infection develops rapidly and both local and generalised signs appear in a few hours.

272

D. Mathieu et al.

Table 2.2.4-3. Anaerobic germ distribution isolated from 3

series of necrotizing fascitiis

Brook43

Giuliano38

Own series48

* Number of patients

259

16

52

* Total of isolated strains

582

75

239

* Strictly and aerotolerant anaerobic bacteria

335

66

79

Gram-negative bacilli

B. fragilis

59

2

16

Bacteroides sp.

17

15

19

Prevotella sp.

49

5

3

& Porphyromonas sp.

Fusobacterium

11

1

3

Gram-positive bacilli

Clostridium perfringens

21

3

26

Clostridia

(except perfringens)

19

1

1

Eubacterium

5

1

3

Propionibacterium

23

4

2

Gram-positive Cocci

Peptostreptococcus

116

12

1

Streptococci

36

22

5

(all groups)

* Strictly aerobic bacteria

247

9

160

Locally, the affected area becomes erythematous, infiltrated, warm and painful; the swelling extends beyond the visible boundaries and beyond the borders of abnormal skin turgor. Usually there is neither lymphangitis nor satellite adenopathy. The lesion spreads quickly as observed by frequent clinical examinations. Crepitation can be found, indicating the presence of gas in the tissue, although it is less frequent than in the case of clostridial myonecrosis. Radiographic pictures of the soft tissue can show gas bubbles separating the sub-cutaneous tissue and showing the shapes of the muscles53. The local signs are remarkable for the speed at which they develop. It is quite possible for localized erythema in the immediate vicinity of a wound to develop into fasciitis involving a whole limb and spreading into the loin and abdomen within a 36 hour-period.

Systemic signs of necrotizing fasciitis often include a marked inflammatory response syndrome with fever, organ dysfunctions and extreme leukocytosis. Altered consciousness, oliguria and coagulopathy indicate that the infection is severe. However, it is essential to be aware that in some cases there is little or no infectious syndrome, even though the infection is rapidly spreading. This suggests a global fulminant infection and immunocompromise.

1.3.2.4 Site-related aspects

* Perineal fasciitis

In 1883, Fournier39 described gangrene of the external genitalia in 5 men. Since then, fast-developing gangrene of the penis and scrotum has been designated as Fournier's syndrome. The category is divided into 2 subgroups : Fournier's disease - in which the initial lesion is undetermined -and secondary Fournier gangrene in which there is a rectal or prostatic cause in the majority of cases 40>41>54>55. Although Fournier's descriptions were sound there are cases of localised gangrene of the penis and scrotum spreading to the whole perineal area. Similarly there are cases of gangrene originating in the anal area spreading to the external genitalia. A similar pathophysiogical process also occurs in women so that today Fournier's syndrome is considered to represent any form of perineal necrotizing fasciitis56-58.

From a clinical point of view, the perineal area is covered in a widespread and painful erythema. Cutaneous necrosis quickly develops. The infection spreads - more frequently in the case of secondary fasciitis -towards the abdomen, groin, buttocks and thighs. Systemic manifestations are also more common in the case of secondary fasciitis.

The search for a cause is an essential point of the management. In around 30 % of cases in men the search for a primary cause is fruitless or reveals only a folliculitis lesion in the scrotum. Nevertheless the fasciitis cannot be treated while the point of entry is left open. Abdomino-pelvic CT scan with a water-soluble contrast enema is a emergency mandatory examination. Many cases of seemingly spontaneous fasciitis ultimately lead to the discovery of an occult rectal or colic cancer58.

Post-operative perineal fasciitis another potential cause - particularly after haemorrhoid or anal fistula surgery.

* Necrotizing fasciitis of the neck and face

Location of necrotizing fasciitis in the neck and face is less frequent59,60. As anaerobic bacteria form the majority of the mouth and throat flora630, it is not surprising that this type of infection can develop after apparently ordinary disorders such as an abscess on a lower third molar61 or in the tonsil62, The absence of barriers to stop the infection from spreading64,65 to the mediastinum66'67 makes this type of infection particularly serious.

From a clinical point of view, the initial disorder (e.g., tooth or throat pain, sub mandibular swelling, etc.) quickly makes way to a rapidly-spreading erythematous swelling involving the whole sub mandibular area ultimately encroaching the other side and providing the well-known clinical picture of Ludwig's Angina68. The infection then spreads to the face, the lower part of the neck, the supraclavicular area and the thorax.

This is a serous condition mainly because the infection can spread to the mediastinum - an event which, in our experience, can only be detected by a cervical and thoracic tomodensitometry. The latter must be carried out as a matter of emergency to assess the development of the infection. The infection then spreads onward to the pleura, the lungs and the pericardium61.

0 0

Post a comment