In vitro activity of 5-episisomicin in bacteria resistant to other aminoglycoside antibiotics

Eighty-seven isolates of Pseudomonas, Enterobacteriaceae, and Staphylococcus, chosen because of their resistance to other aminoglycosides, were tested for susceptibility to 5-episisomicin. Tests were performed in Mueller-Hinton agar and also, with 38 of these isolates, in Mueller-Hinton broth. Of Enterobacteriaceae, 85 and 95.5% were inhibited by 5 and 10 mug of 5-episisomicin per ml, respectively. Amikacin inhibited 74 and 91% of the strains at 10 and 20 mug/ml, respectively. Fifty-four percent of P. aeruginosa were inhibited by 5-episisomicin and amikacin. Eighty-three percent of S. aureus were inhibited by netilmicin and amikacin, whereas only 50% were inhibited by 5-episisomicin. Isolates resistant to 5-episisomicin were most often resistant to the other aminoglycosides and occurred in gram-negative bacilli that did not carry aminoglycoside-modifying enzymes. Five of 23 isolates that carried a 6'-N-acetyltransferase (AAC-6') and one of two that carried an aminoglycoside 3-acetyltransferase were resistant to and acetylate 5-episisomicin. Strains carrying other aminoglycoside-modifying enzymes were inhibited by 5-episisomicin. Thus, 5-episisomicin is a promising aminoglycoside not attacked by most aminoglycoside-modifying enzymes. Resistance will probably most often be based upon nonenzymatic mechanisms which will also affect other aminoglycosides.

Infections due to gentamicin-resistant Staphylococcus aureus strain in a nursery for neonatal infants

An apparently homogeneous strain of Staphylococcus aureus resistant to gentamicin (Gmr), kanamycin, tobramycin, and sisomicin, but susceptible to amikacin and netilmicin, caused multiple infections in neonatal infants in a special care nursery. Nasal cultures revealed a high rate of carriage of the Gmr staphylococcus in infants without clinical infection. Segregating patients according to a modified cohort system and use of careful aseptic techniques led to apparent elimination of the Gmr strain. The resistance to aminoglycosides in this strain was mediated by an aminoglycoside 6'-N-acetyltransferase and a gentamicin phosphotransferase. Genetic determinants for these enzymes were borne on a circular covalently closed plasmid of approximately 11 megadaltons. These resistance determinants closely resemble those found in isolates of S. aureus that have caused nosocomial infections in patients in Europe.

In vitro comparison of netilmicin, a semisynthetic derivative of sisomicin, and four other aminoglycoside antibiotics

One hundred isolates of Pseudomonas and Enterobacteriaceae, of which 85 were chosen because of their resistance to gentamicin or amikacin, were tested for susceptibility to netilmicin (SCH 20569), a new semisynthetic derivative of sisomicin, and to four other aminoglycosides. Tests were performed in Mueller-Hinton agar and, with 43 of these isolates, also in Mueller-Hinton broth. Most isolates of Escherichia coli, Klebsiella, Enterobacter, Citrobacter, and Serratia that were gentamicin resistant proved to be susceptible to netilmicin and amikacin. Tests of representative isolates of this group showed that they owed their resistance to the production of aminoglycoside-adenylylating enzymes. Four isolates of Serratia, detected by their resistance to amikacin, were also highly resistant to netilmicin but were susceptible to gentamicin. These isolates produced aminoglycoside-acetylating enzymes. Gentamicin-resistant Proteus and Providencia were, in general, highly resistant to netilmicin but were susceptible to amikacin. These isolates also produced aminoglycoside-acetylating enzymes. Most gentamicin-resistant strains of Pseudomonas were resistant to netilmicin, either by enzymatic aminoglycoside modification or by other undefined mechanisms. Thus, like amikacin, netilmicin extends the aminoglycoside susceptibility pattern of Enterobacteriaceae to include gentamicin-resistant isolates that produce aminoglycoside-adenylylating enzymes. It is ineffective against strains, some of them susceptible to amikacin, gentamicin, or tobramycin, that produce aminoglycoside-acetylating enzymes.

[ Study of prolactin and blood gonadotropins in amenorrheas-galactorrhea. Dynamic exploation in 13 cases]

A study of the secretion of prolactin and plasma gonadotrophins was carried out comparatively in 3 groups of patients: histologically confirmed prolactin adenoma (group 1), idiopathic or iatrogenic amenorrhoea/galactorrhoea syndrome (group 2), empty sella turcica syndrome (group 3). The last group differs fundamentally from the two previous by the presence of a normal basal LH and FSH levels and normal LH-RH stimulation. Prolactin is not increased. It may be suppressed by L-dopa and stimulated by TRH. There exist no differences, apart from neuroradiological criteria, between the other two groups. The level of LH is slightly decreased but the response to LRH is positive, this effect often being more clear on FSH. Prolactin levels are raised, this no doubt explaining the negative response to TRH and chlorpromazine stimulation. Suppression by L-dopa is positiive, reflecting the absence of autonomy of prolactin adenomata. The water load test is unsatisfactory. There exists at the present time no method sufficiently discriminating to exclude the presence of a tumour at the origin of an amenorrhoea-galactorrhoea syndrome.