Low-level colonization of hospitalized patients with methicillin-resistant coagulase-negative staphylococci and emergence of the organisms during surgical antimicrobial prophylaxis

Abstract

By use of techniques that have been developed to detect small numbers of methicillin-resistant staphylococci, we cultured samples from the nares and subclavian and inguinal areas of 29 patients before and after cardiac surgery and 10 patients before and after coronary angioplasty. Methicillin-resistant coagulase-negative staphylococci were recovered before the surgical or angioplasty procedure from 74% of patients. The quantitative recovery of methicillin-resistant isolates before cardiac surgery or coronary angioplasty was compared with the number of methiciflin-resistant staphylococci detected at the same site 3 days after the procedure. In cardiac surgery patients (who received antibiotic prophylaxis), 17 of the 28 sites (61%) in which low-level colonization with methicillin-resistant strains was detected preoperatively contained high levels of methicillin-resistant staphylococci postoperatively. In contrast, coronary angioplasty patients (who did not receive antibiotic prophylaxis) did not have any of the 14 sites containing low levels of methicillin-resistant strains before angioplasty emerge to harbor high levels of methicillin-resistant staphylococci after angioplasty. Methicillin-resistant coagulase-negative staphylococci from each site in which high levels of methicillin-resistant staphylococci emerged postoperatively were paired with preoperative isolates from the same site. Identical antibiograms and plasmid profile patterns were demobstrated for seven of the pre-and postoperative isolate pairs, suggesting that the high levels of methicillin-resistant coagulase-negative staphylococci detected on the skin or in the nares after cardiac surgery were derived from methicillin-resistant organisms present at the site preoperatively in much smaller numbers.Two factors have hindered the epidemiologic study of methicillin-resistant (MR) coagulase-negative staphylococci as colonizing flora of hospitalized patients. First, routine skin culture techniques sample only a fraction of the skin's quantitatively complex flora (9,11,16), potentially missing small subpopulations of antibiotic-resistant organisms. Second, organisms that possess the MR genotype may fail to express resistance phenotypically unless they are encouraged to do so by certain laboratory manipulations (growth in salt-supplemented media, incubation at a lower temperature, use of a large inoculum, etc.), further impairing recognition of their presence (1,5,7,14). We adopted culture techniques which ensured that a reasonable fraction of the colonizing flora of a patient would be sampled and which encouraged the phenotypic expression of the MR genotype. We used these techniques to reexplore the epidemiology of MR coagulase-negative staphylococci in cardiac surgery and coronary angioplasty patients. were interviewed with regard to the possible risk factors of prior colonization with MR coagulase-negative staphylococci (hospitalization or antibiotic usage within the last 3 months or time spent in the intensive care unit). After the patients were enrolled...

Prolonged Antibiotic Prophylaxis After Cardiovascular Surgery and Its Effect on Surgical Site Infections and Antimicrobial Resistance

“…22 In contrast, prolonged antibiotic use after surgery induces antimicrobial resistance and may facilitate the colonization of foreign devices with antimicrobial-resistant organisms. [23][24][25] Therefore, in place of extended ABP, meticulous handling of catheters, strict compliance with hand disinfection, maintenance of closed drainage systems, and early catheter removal are the preferred means to avoid infections related to foreign devices. 26 Observational cohort studies should complement controlled clinical trials dealing with ABP, because the latter have a limited ability to detect adverse effects such as acquisition of resistant microorganisms, provide information only about patients who satisfy the criteria for study entry, and often concentrate on the efficacy of specific agents rather than evaluate variations in the duration of prophylaxis.…”

Comparative prophylactic efficacies of ciprofloxacin, ofloxacin, cefazolin, and vancomycin in experimental model of staphylococcal wound infection

“…This does not mean, however, that a short course of perioperative treatment in humans will not select for quinolone-resistant staphylococci in niches harboring a more complex and numerous staphylococcal flora such as the nares or skin. Considering the proven ability of prophylaxis with other antimicrobial agents to select for antibiotic-resistant organisms (1,24,37), it is likely that quinolone prophylaxis will demonstrate a similar propensity. Since perioperative antibiotic prophylaxis accounts for one-third of all antibiotic use among hospitalized patients (21,40), it exerts considerable selective pressure upon the important pathogens causing nosocomial infections within an institution.…”

Impact of an Infection Control Program on the Prevalence of Nosocomial Infections at a Tertiary Care Center in Switzerland

“…20 It is frequently prescribed for prolonged periods and may contribute to the emergence of resistant pathogens. 21 The main goal of this step of our intervention was to standardize the prophylaxis procedure and, therefore, increase the compliance with the administration time recommended in the guideline and avoid unnecessary postoperative administration. The distribution of the guideline on pocket cards made it easily available and may have contributed to improved compliance and reduced antibiotic consumption.…”