Ciprofloxacin treatment of Staphylococcus aureus infections

39 Infectious Diseases Newsletter 7(5) May 1988 tropicalis were highly predictive of systemic infection. Positive surveillance cultures for C. albicans were not predictive of disease. Negative surveillance cultures for C. albicans were not predictive of disease. Negative surveillance cultures for C. albicans and C. tropicalis had a high negative predictive value (95-99%). The authors concluded that surveillance culture data for specific Candida spp may aid in diagnostic and therapeutic decision making. Comment The logic behind doing surveillance cultures for Candida spp is similar to that used by neonatologists who often obtain surveillance cultures to determine the likelihood of neonatal sepsis. This logic holds that the first step in the pathogenesis of invasive infection is colonization of the gastrointestinal tract or oropharynx by the potential pathogen. The usefulness of neonatal surveillance cultures was recently evaluated in a large study (JAMA 259:248-252, 1988) and found to be minimal. Similarly, the results of this study can be interpreted to show that surveillance cultures for Candida spp have minimal usefulness, although the authors failed to calculate the sensitivity and specificity testing. Moreover, the authors inclusion of urine cultures in their analysis for predictive value may be challenged because candiduria more often results from renal "filtration" of yeasts in a fungemic patient than from colonization of the urinary tract followed by invasion. Finally, the cost of multiple surveillance cultures far outweighs any potential for clinical usefulness [3084 cultures at approximately $30 per culture (Vanderbilt charge) comes to $92,520)]. CWS []

Righter J: Ciprofloxacin treatment of Staphylococcus aureus infections.

J. Antimicrob Chemother 20:595-597, 1987. Ciprofloxacin (200 mg, IV, 12-hourly until defervescence, followed by 750 mg, PO, 12-hourly, to complete a 2week course of therapy) was used to treat 17 patients with infections caused by Stapylococcus aureus that were severe enough to require hospitalization and parenteral therapy. The results were poor with clinical failure in five and bacteriologic failure in 12. Neither emergence of resistance during therapy nor tolerant strains was cause for the poor results. The author advises great caution before ciprofloxacin is used to treat systemic staphylococcal infections, particularly in neutropenic patients. Comment Although numerous in vitro studies have demonstrated that ciprofloxacin has high inhibitory activity against S. aureus (mean MIC approximately 1 ug/ml), the clinical utility of ciprofloxacin is prejudiced by two factors: 1) ciprofloxacin has relatively poor bactericidal activity against S. aureus, e.g., in our kill-kinetic studies less than 50% of the final inoculum was killed at 12 or 24 h at 1/2 x MIC and 1 x MIC, whereas at 4 x MIC there was 95% killing at 12 h, but not at 24 h (Antimicrob Agents Chemother 31: 1210-1215, 1987); and 2) the peak concentrations in the serum even after IV administration are only about 3 ug/ml after a dose of 200 mg (Antimicrob Agents Chemother 28:235239, 1985; Antimicrob Agents Chemother 27:375-379, 1985). In view of the relatively poor bactericidal activity and the low serum/tissue concentrations, it is not surprising that clinical efficacy was not satisfactory. CWS []

Klotz SA, Penn RL: Acid-fast staining of urine and gastric con© 1988 Elsevier Science Publishing Co., Inc. 0278-2316/88/$0.00 + 2.20

tents is an excellent indicator of mycobacterial disease. Am Rev Resp Dis During the years 1974-1984, 5,829 specimens of urine (first morning voidings only) and 309 gastric aspirates were processed by digestion with either N-acetyl-L-cysteine or NaOH. Smears were examined using fluorochrome staining, followed by Kinyoun staining of fluorochromepositive specimens. The results of examinations of the smears were compared to the results of cultures set up when the smears were made (three kinds of culture medium). Of 47 culture-positive specimens of urine, 23 were also smear-positive; 22 of these came from patients with clinically established mycobacterial disease. Of 39 culture-positive gastric aspirates, 9 were also smear-positive; all came from patients with clinically established mycobacterial disease. The one falsely smear-positive specimen of urine yielded Mycobacterium gordonae by culture. On the other hand, 12 of the stain-negative specimens of urine yielded saprophytic mycobacteria in cultures, as did two of the gastric aspirates. The authors conclude that detection of acid-fast bacteria in smears of concentrates of urine and gastric aspirates reliably indicate mycobacterial disease.

Comment It is dogma that examination of smears of urine and gastric contents for acid-fast bacteria is a potentially misleading exercise because of the high prevalence of saprophytic acidfast bacteria in the mouth and urethra. The authors emphasize that examination of smears by experienced microscopists is a highly important determinant of the validity of the test. Undoubtedly, this is correct. Unfortunately, the trend in medical training continues away from acquisition of the skill needed to perform the simple, yet demanding, and still clin-