What Is GRAM-NEGATIVE BACTEREMIA?
Bacteremia caused by gram-negative bacilli has become a problem of greater relative impor-tance since the advent of penicillin and better control of gram-positive coccal infections. Urinary tract infection accounts for about two-thirds of all cases of blood invasion by enteric bacteria. Other causes include surgical disease of the gastrointestinal tract, infections developing at the site of “cut-downs” and “interacts” for intravenous therapy, postpartum or postabortal sepsis (including the so-called “placental Sometimes there is a clearly apparent precipitating factor such as cystoscopy, surgical or obstetrical procedure, or manipulation of an infected wound.
These bacterias have clinical characteristics closely resembling the recognized biological effects of gram-negative bacterial endotoxins. The onset of symptoms may occur with a shaking chill and rise in temperature of 101 to 105° F. There is an initial leukopenia, but after 6 to 12 hours usually there is leukocytosis. An important and highly significant accompaniment is a circulatory embarrassment with the lowering of the blood pressure. This may be manifested only by some alteration in the patient's state of consciousness, and the skin may continue to feel warm, although sometimes the skin is cold and clammy.
Occasionally patients slip into a shocklike state without much elevation of temperature; hence infection of this kind must always be taken into consideration in the evaluation of peripheral circulatory failure. Petechial hemorrhages and purpura are not common. There are a diminution in urine output, an increase in proteinuria, and often a rise in nonprotein nitrogen of the blood. Some patients show shifts in acid-base balance in the direction of metabolic acidosis, whereas others have hyperventilation and respiratory alkalosis. Much depends on the nature of the underlying disease and the renal reserve. The outlook is grave, being influenced by age, associated disease, and evidence of shock. When obvious signs of circulatory collapse are present, the fatality rate may be as high as 75 percent.
Clinical significance and mere removal of necrotic tissue may cause it to disappear. Nevertheless, under certain circumstances, especially in chronically debilitated persons or in patients with agranulocytosis or acute leukemia, severe sepsis may be produced by this class of bacteria. Pseudomonas is notoriously resistant to anti-microbial therapy; hence it tends to emerge as the dominant micro-organism following eradication of other bacteria by drugs, and it may then be responsible for the phenomenon of superinfection, as in the bronchopulmonary infections that may complicate prophylactic chemotherapy of chronic lung disease.
Because Pseudomonas commonly occurs in tap water, and because it may be resistant to antiseptics used in sterilizing instruments, it is likely to be carried into the body by such procedures as cystoscopy. Furthermore, most of the reported instances of meningitis following lumbar puncture have been associated with this organism. Tissue invasion is characterized by necrotizing vasculitis with bacterial invasion of the walls of arteries and veins. This leads to a distinctive necrotic skin lesion (called ecthyma gangrenous) that is found most commonly along the axillary folds or in the anogenital area but may also de-yelp on any part of the body. It may begin as a vesicle that later becomes necrotic. The typical lesion of ecthyma gangrenous is around an indurated ulcer with a black center that varies from a few millimeters to several centimeters in diameter.
UNIQUE FEATURES OF PSEUDOMONAS INFECTIONS
Pseudomonas infections, although often similar to those caused by other gram-negative bacteria, sometimes have unique characteristics. As already mentioned, this organism frequently appears in necrotic tissue, as in ulcers, burns, or draining sinuses. Usually, such colonization is of little.
TREATMENT OF ENTERIC BACTERIAL INFECTIONS
General Principles. early recognition and drainage of abscesses,
(1) the anticipation of the role' of anaerobic bacteria that cannot be readily cultured, and
(2) early recognition of bacteremic shock. Every physician must consider the elimination of such sources of contamination as one of his prime responsibilities. Gram-Negative Bacteremia. Removal of devices and drainage of abscesses should be done as soon as possible. Among the aminoglycoside antimicrobials, gentamicin and kanamycin are the most reliable,