Occurrence of quinolone resistance in Staphylococcus aureus from nosocomial infection.
TL;DR: The phenotypic association of quinolone resistance and MRSA is rather likely due to a higher frequency of spontaneous resistant mutants which are present in natural populations of MRSA.
Abstract: Among 63 Staphylococcus aureus isolates (one isolate per one patient) counted from infections (from August to November 1991) in hospital T., eight exhibited resistance to fluoroquinolones. Seven of these quinolone-resistant isolates were multiply- and methicillin-resistant S. aureus (QR-MRSA). The results of phage-, plasmid- and genotyping (pulsed field electrophoresis) revealed that six different strain-clones of these MRSA were spread in the hospital. In vitro spontaneous mutants resistant to fluoroquinolones are 10-100-fold more frequent in MRSA than in other S. aureus when selected on isosensitest-agar containing 1 microgram/ml of ciprofloxacin. However, the same mutant frequencies were found in strain 8325-4 with and without the mecA-determinant. The resistance phenotype was stable over 30 generations of subculture in nutrient broth as well in natural quinolone resistant MRSA as in mutants of other types of S. aureus selected in vitro. The phenotypic association of quinolone resistance and MRSA is rather likely due to a higher frequency of spontaneous resistant mutants which are present in natural populations of MRSA. Data of chemotherapy prior to the isolation of S. aureus show that three of seven patients from whom QR-MRSA were isolated were treated with a quinolone. In eight cases of infections with non-MRSA and quinolone treatment the isolated S. aureus strains were in vitro sensitive to quinolones.
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TL;DR: The use of repeatedly subcultured strains of H. pylori in virulence experiments can lead to different results from those of the original strain, especially when the adhesion, motility, cytotoxicity, and gastric inflammation produced in Mongolian gerbils are compared.
Abstract: In vitro subcultures of bacteria can lead to genetic and phenotypic changes. This study aimed at investigating the effect of repeated subcultures on the adhesion, motility, cytotoxicity, and gastric inflammation caused by Helicobacter pylori. H.pylori SS1 strain was subcultured 64 times on agar plates containing Brucella broth and 5% bovine calf serum. The adhesion, motility, cytotoxicity, and gastric inflammation produced in Mongolian gerbils were compared between the first and 64th subcultured strain. The adhesion rates, following 3 hr exposure of AGS cells to either the first strain or the 64th-transferred strain, were 21% and 12%, respectively. The motility of the 64th-transferred strain decreased significantly when compared to the 1st strain (9.1 mm vs. 15.1 mm). The cytotoxicity index tended to be higher in the first strain than in the 64th-transferred strain (73.7% vs. 69.2%). The initial infection rate on the gerbils showed no difference between the two strains. However, chronic gastric inflammation of the first strain-infected gerbils was somewhat more severe than that of the 64th-transferred strain-infected gerbils. Therefore, the use of repeatedly subcultured strains of H. pylori in virulence experiments can lead to different results from those of the original strain.
13 citations
Cites background from "Occurrence of quinolone resistance ..."
...In vitro, spontaneous mutants resistant to fluoroquinolones are frequent in methicillin-resistant Staphylococcus aureus when selected on isosensitest-agar containing 1 g/mL of ciprofloxacin (10)....
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...Also, specific mutants of the original organisms can be made by adjusting the culture condition (9, 10)....
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TL;DR: Evidence for the spread of previously recognized epidemic MRSA clones in Poland and the presence of a new epidemic heterogeneously resistant clone of MRSA in hospitals outside Warsaw is documented.
13 citations
TL;DR: Oxacillin-susceptible staphylococci confirmed their susceptibility to many other antimicrobial agents while oxacilli-resistant strains confirmed their multiple and frequent resistance to antibiotics.
Abstract: A multicentre study to evaluate the susceptibility of Gram-positive cocci isolated from clinical samples, was performed by six centres working in different areas of Italy. We examined 4,544 strainsof Staphylococcus aureus, 4,381 strains of coagulase-negative staphylococci and 2,478 strains of enterococci. The following antibiotics were tested: penicillin G, ampicillin, amoxicillin, piperacillin, imipenem, oxacillin, ofloxacin, pefloxacin, ciprofloxacin, gentamicin, tobramycin, amikacin, netilmicin, rifampicin, clindamycin, tetracycline, cotrimoxazole, erythromycin, chloramphenicol, vancomycin and teicoplanin. Oxacillin-susceptible staphylococci confirmed their susceptibility to many other antimicrobial agents while oxacillin-resistant strains confirmed their multiple and frequent resistance to antibiotics. Resistance to oxacillin, cotrimoxazole and chloramphenicol was more frequent in coagulase-negative staphylococci than inStaphylococcus aureus. Aminoglycosides, rifampicin and quinolones were more active against coagulase-negative staphylococci than againstStaphylococcus aureus. Enterococci were susceptible to penicillins and imipenem, and moderately susceptible to cipro-floxacin. Susceptibility of 70–79% was observed with high levels of aminoglycosides. Excellent results against staphylococci and enterococci were observed with vancomycin and teicoplanin.
12 citations
TL;DR: These investigations confirmed that MRSA in the hospital, 1991 and 1994, was not due to the spread of one or two clones, but by the simultaneous occurrence of a few well characterized strains and sporadic, occurring strains of different phage-types.
8 citations
01 May 1993-Zentralblatt Fur Bakteriologie-international Journal of Medical Microbiology Virology Parasitology and Infectious Diseases
TL;DR: Results indicate that there is obviously no overregional spread of one particular QR-MRSA clone and that quinolone resistance has developed independently in different MRSA.
Abstract: Summary Methicillin-resistant S. aureus with quinolone-resistance (QR-MRSA) isolated in Germany from three outbreaks of nosocomial infections and from sporadic nosocomial infections in five hospitals exhibited different SmaI-restriction patterns of their genomic DNA. Phage-typing and determination of plasmid profiles performed in parallel confirmed this differentiation, with one exception. These results indicate that there is obviously no overregional spread of one particular QR-MRSA clone and that quinolone resistance has developed independently in different MRSA.
7 citations
References
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TL;DR: A high-molecular-weight PBP (PBP-2a; approximate size, 78,000 daltons) was detected that was only present in the resistant bacteria but not in the isogenic sensitive strain, and in cultures grown at pH 5.2, the extra PBP was not detectable.
Abstract: Methicillin resistance in Staphylococcus aureus has been associated with alterations in the penicillin-binding proteins (PBPs). An intriguing property of all methicillin-resistant staphylococci is the dependence of resistance on the pH value of the growth medium. Growth of such bacteria at pH 5.2 completely suppressed the expression of methicillin resistance. We have examined the PBP patterns of methicillin-resistant staphylococci grown at pH 7.0. We detected a high-molecular-weight PBP (PBP-2a; approximate size, 78,000 daltons) that was only present in the resistant bacteria but not in the isogenic sensitive strain. In cultures grown at pH 5.2, the extra PBP was not detectable. Images
856 citations
Journal Article•
TL;DR: A detailed account of methods that have been found satisfactory for propagating the phages are given and a standard testing routine by which the stability of the phage preparations can be verified is defined.
Abstract: Standardized methods are essential if phage typing of staphylococci is to be reliable and if the results obtained in different laboratories are to be compared. This paper, prepared on behalf of the Subcommittee on Phage Typing of Staphylococcus of the Nomenclature Committee of the International Association of Microbiological Societies, gives a detailed account of methods that have been found satisfactory for propagating the phages and defines a standard testing routine by which the stability of the phage preparations can be verified. Technical details are given of methods recommended for determining the phage type of staphylococci and the interpretation of differences between the types is discussed. The need for close collaboration between the epidemiologist and the laboratory worker in the use of phage typing is emphasized.
821 citations
"Occurrence of quinolone resistance ..." refers methods in this paper
...Phage typing was performed using the international basic set [11] and two sets of experimental phages (for details see [12]....
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TL;DR: The status of these agents as revealed in the published English literature is reviewed in a two-part minireview, considering the structures, mechanisms of action and resistance, and spectra of activity of the six aforementioned fluoroquinolones with reference to nalidixic and oxolonic acids.
Abstract: INTRODUCTION During the past 5 to 7 years, much attention has been given to the synthesis of new 4-quinolone-3-carboxylates and to the evaluation of these newly prepared agents for antibacterial activity, a revival of interest generated by the discovery of nalidixic and oxolinic acids mtny years ago. This renewed effort uncovered a. number of 6-fluoro-7piperazino-4-quinolones noteworthy for both the breadth and intensity of their activities against gram-negative bacilli and cocci in vitro and for the capacity to control experimentally induced systemic infections with selected bacteria when administered orally in well-tolerated doses (21). The most active representatives of this compound class, designated fluoroquinolones, include norfloxacin (AM-715, MK-0366), ofloxacin (DL-8280), ciprofloxacin (Bay o 9867), amifloxacin (WIN 49375), enoxacin (AT-2266, CI-919), and pefloxacin (1589-RB). The prim4ary target of nalidixic acid and probably also all the fluoroquinolones is DNA gyrase, an essential bacterial enzyme that maintains superhelical twists in DNA (13, 18, 24). The promise of the fluoroquinoloies led to their prompt evaluation for pharmacokinetics in human volunteers and cautious assessments of therapeutic potential, including tolerability in selected patients. The encouraging results of these early trials, with the burgeoning interest in further studies, have made it desirable to review the status of these agents as revealed in the published English literature. We have attempted this task in a two-part minireview. The first part here considers the structures, mechanisms of action and resistance, and spectra of activity of the six aforementioned fluoroquinolones with reference to nalidixic and oxolonic acids for comparison. The second part will consider pharmacology, clinical activity, and toxicities in humans (D. C. Hooper and J. S. Wolfson, Antimicrob. Agents Chemother., in press). Other quinolones, such as cinoxacin, pipemidic acid, rosoxacin, and flumequine, will not be discussed directly. Several reviews of cinoxacin have recently appeared (28, 63).
711 citations
"Occurrence of quinolone resistance ..." refers background in this paper
...staphylococci [1] with no difference between methicillinresistant Staphylococcus aureus (MRSA) and methicillin-sensitive strains....
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304 citations
"Occurrence of quinolone resistance ..." refers background in this paper
...aureus and Pseudomonas aeruginosa together with therapeutic use correspond to these observations [7, 8]....
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Book•
30 Nov 1990
TL;DR: Introduction genome organization and evolution gene transfer and transposons plasmids exoproteins and pathogenicity factors resistance and its spread resistance and epidemiology.
Abstract: Introduction genome organization and evolution gene transfer and transposons plasmids exoproteins and pathogenicity factors resistance and its spread resistance and epidemiology.
272 citations