Rapid development of ciprofloxacin resistance in methicillin-susceptible and -resistant Staphylococcus aureus

Article Abstract:

Staphylococcus aureus (S. aureus) is a common bacteria that is found on the skin and inside the nose. There are many different types, or strains, of S. aureus. Some of these strains are resistant to or not killed by methicillin (MRSA, methicillin-resistant S. aureus), while other strains are sensitive to or are killed by methicillin (MSSA, methicillin-susceptible S. aureus). Infections with MRSA are difficult to treat and are a major cause of sickness and death in hospitalized patients. Elderly patients, patients with burns, patients who are seriously ill and those in intensive care units have the greatest risk for developing infections with MRSA. Currently, the best drug for treating MRSA infections is vancomycin. However, this drug is expensive, it must be given intravenously (directly into a vein), and it is not effective in eliminating MRSA located in the nose. Another drug known as ciprofloxacin has been proposed as an alternative means of treating MRSA and MSSA infections. Several clinical studies have shown that ciprofloxacin is effective in treating MRSA and MSSA infections. However, some MRSA infections have shown resistance to treatment with ciprofloxacin. At the Veterans Administration Medical Center in Atlanta, it was reported that 79 percent of the MRSA infections became resistant to treatment with ciprofloxacin within one year, and 14 percent of the MSSA infections became resistant. These results suggest that ciprofloxacin has limited use in treating infections caused by MRSA. (Consumer Summary produced by Reliance Medical Information, Inc.)

Staphylococcus aureus, Methicillin, Ciprofloxacin

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Increase of trimethoprim resistance among Shigella species, 1975-1988: analysis of resistance mechanisms

Article Abstract:

Trimethoprim (TMP) has been used alone and in combination with other drugs for the treatment of bacterial infections of the urinary tract. Recent data has shown that resistance to trimethoprim has been increasing over the past twenty years among urinary tract pathogens such as Escherichia coli and the Proteus and Klebsiella species. Resistance has also been reported to be increasing among the different Shigella species. Co-resistance to other antimicrobial drugs has also been on the increase. The mechanisms of resistance to TMP have been characterized as the development of a plasmid-mediated dihydrofolate reductase (DHFR) enzyme. Types I and II have most frequently been detected among the Shigella, with type I imparting highest degree of resistance to TMP. Among Finnish travelers, the number of TMP-resistant Shigella isolates has been increasing consistently, from 3 percent between 1975 and 1982 to more than 42 percent in 1988. A total of 1,951 isolates were obtained from returning Finnish travellers during the years of the study. Strains of Shigella sonnei (Ss) were the most resistant, followed by strains of Shigella flexneri (Sf). Resistance varied among all species, depending on the countries visited and the possible source of the infection. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Finland, Shigella, Trimethoprim

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Interspecies gene transfer in vivo producing an outbreak of multiply resistant shigellosis

Article Abstract:

Resistance-factor plasmids (bacterial components outside the nucleus) have readily been transferred in studies conducted in the laboratory. The development of resistance during antibiotic therapy suggests frequent occurrence of the transfer of R-factors in living beings, but this event has rarely been clinically documented. This case of multiply resistant Shigella infections suggests the transfer of R-factor from a multiply resistant strain of Escherichia coli in the index case. A 57-year-old Hopi Indian woman was admitted for diarrhea and dysuria. Her stool was positive for Shigella flexneri 3a and her urine was positive for E. coli. She had repeated episodes and had been treated with a wide array of antibiotics, including trimethoprim-sulfamethoxazole, for a period of five years. The strain of S. flexneri isolated from the woman was later identified in six other people on the reservation. It appears that the R-factor plasmid was transferred from the E. coli to S. flexneri, since the earlier E. coli isolate showed the same resistance pattern as the Shigella isolate. It appears that resistant coliform strains seem to appear following preventive therapy with the antibiotic trimethoprim-sulfamethoxazole, suggesting this practice be reevaluated. (Consumer Summary produced by Reliance Medical Information, Inc.)

Case studies, Genetic aspects, Pathogenic microorganisms, Shigella flexneri, Shigellosis, Bacillary dysentery

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