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PubMed2001

Antibiotic-resistant pneumococci carried by young children do not appear to disseminate to adult members of a closed community.

Although antibiotic-resistant pneumococci have been frequently detected among day care center (DCC) attendees, the transmission of these organisms to other members of the community has not been adequately studied. Nasopharyngeal cultures were obtained from 152 children and 244 adult members of a closed community (a kibbutz) in Israel. Serotyping, antibiogram, and pulsed-field gel electrophoresis were performed to determine the relatedness of isolated pneumococci. Twenty (30%) of the 66 isolates from children showed decreased susceptibility to penicillin and 9 isolates (14%) were resistant to > or =3 drugs. Of the 16 isolates from adults, 5 (31%) were intermediately resistant to trimethoprim-sulfamethoxazole. Resistant strains carried by DCC attendees were not isolated either from their parents or from other adult members of the community. Despite the high degree of interpersonal contact occurring in a closed community, resistant pneumococcal strains carried by DCC attendees do not appear to be easily transmitted to the adult population, which suggests the existence of an immunological barrier.

Adolescent↗
PubMed2001

Optochin resistance in Streptococcus pneumoniae: mechanism, significance, and clinical implications.

Traditionally, Streptococcus pneumoniae is identified in the laboratory by demonstrating susceptibility to optochin. Between 1992 and 1998, 4 pneumococcal isolates exhibiting optochin resistance were recovered from patients at Children's National Medical Center. Three of the 4 isolates consisted of mixed populations of optochin-resistant and -susceptible organisms. Both subpopulations had identical antibiograms, serotypes, and restriction fragment profiles. The other isolate was uniformly resistant to optochin. Resistant strains had MICs of optochin 4-30-fold higher than susceptible strains, belonged to different serotypes, and had dissimilar restriction fragment profiles, indicating clonal unrelatedness. Resistance arose from single point mutations in either the a-subunit (W206S) or the c-subunit (G20S, M23I, and A49T) of H(+)-ATPase. There is speculation of a possible association between exposure to antimalarial drugs and evolution of optochin resistance. alpha-Hemolytic streptococci resistant to optochin, particularly invasive isolates, should be tested for bile solubility or with an S. pneumoniae DNA probe before identification as viridans streptococci.

Amino Acid Sequence↗
PubMed2002

Spread of Streptococcus pneumoniae and antibiotic-resistant S. pneumoniae from day-care center attendees to their younger siblings.

A prospective study was conducted to determine the association between pneumococcal carriage among 36 infants and young toddlers cared for at home and carriage among their older siblings who attended 8 day-care centers (DCCs); 71 pneumococcal strains acquired by the younger siblings were compared with those present in the DCCs for 6 months. In 76% of cases, > or =1 strain identical by serotype and antibiogram was isolated in the older siblings' DCC versus 32%-63% in all other DCCs (P<.001). When phenotypically identical strains were compared by pulsed-field gel electrophoresis, the similarity between strains from older siblings' DCCs and the younger siblings' isolates was striking. This was not found when isolates from other DCCs were compared. Vaccinating DCC attendees with a 7-valent pneumococcal conjugate vaccine may play a key role in controlling the spread of antibiotic-resistant pneumococci, because the most resistant serotypes are included in the vaccine.

Anti-Bacterial Agents↗
PubMed2003

Emergence of multidrug-resistant Salmonella enterica serotype Newport infections resistant to expanded-spectrum cephalosporins in the United States.

We describe a field investigation in New England that identified the emergence and epidemiology of new strains of multidrug-resistant Salmonella, Newport-MDRAmpC, and summarize the Center for Disease Control and Prevention's surveillance data for these infections. In Massachusetts, the prevalence of Newport-MDRAmpC among Salmonella serotype Newport isolates obtained from humans increased from 0% (0/14) in 1998 to 53% (32/60) in 2001 (P<.001). In a retrospective case-control study, infection with Newport-MDRAmpC was domestically acquired and was associated with exposure to a dairy farm. Isolates from both humans and cattle had indistinguishable or closely related antibiograms and pulsed-field gel electrophoresis patterns. Nationally, the prevalence of ceftriaxone-resistant Salmonella increased from 0.5% in 1998 to 2.4% in 2001; 85% of the isolates in 2001 were Newport-MDRAmpC, and at least 27 states have isolated these strains from humans, cattle, or ground beef. These data document the widespread emergence of Newport-MDRAmpC strains in the United States and show that the 5-fold increase in the prevalence of Salmonella resistant to expanded-spectrum cephalosporins, between 1998 and 2001, is primarily due to the emergence of Newport-MDRAmpC strains.

Adolescent↗
PubMed2004

Emergence of penicillin-nonsusceptible Streptococcus pneumoniae clones expressing serotypes not present in the antipneumococcal conjugate vaccine.

BACKGROUND: Penicillin-nonsusceptible Streptococcus pneumoniae isolates are confined mainly to a few serogroups. Capsular transformation may serve as a mechanism for spreading antibiotic resistance to new serotypes. METHODS: Antibiogram and molecular typing, by pulsed-field gel electrophoresis (PFGE), were performed on 46 nasopharyngeal and middle ear fluid (MEF) isolates expressing serotype 11A, 45 MEF isolates expressing serotype 15B/C (recovered during 1998-2003 from Israeli children <5 years old), and 57 MEF isolates expressing serotype 19F (recovered during 1998-2001 from Costa Rican children <7.5 years old). RESULTS: PFGE patterns showed that 49 (86%) of 57 serotype 19F isolates and 19 (41%) of 46 serotype 15B/C isolates were closely related. The vast majority of these isolates (80% of serotype 19F and 100% of serotype 15B/C isolates) were nonsusceptible to penicillin. Multilocus sequence typing (MLST) data show that the serotype 15B/C isolates belonged to the ST346 cluster, whereas the serotype 19F isolates were a single-locus variant of ST346. For serotype 11A isolates, PFGE patterns and MLST analysis showed that 8 (80%) of the 10 penicillin-nonsusceptible isolates belonged to a single clone--namely, ST156--which was identical to the international Spain9V-3 clone. CONCLUSIONS: Penicillin-nonsusceptible pneumococcal clones of serotypes not related to those included in the 11-valent conjugate vaccines may derive from capsular transformation of vaccine-related serotypes. Of particular concern was the detection of serotype 11A variants of the successful international Spain9V-3 clone. This phenomenon, although seemingly rare at present, can have implications for the long-term effectiveness of the conjugate vaccines.

Child↗
PubMed2005

Hospital and community fluoroquinolone use and resistance in Staphylococcus aureus and Escherichia coli in 17 US hospitals.

BACKGROUND: Fluoroquinolones are widely prescribed in hospitals and the community. Previous studies have shown associations between fluoroquinolone use and isolation of fluoroquinolone-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). We performed an ecologic-level study to determine whether variability in hospital percentages of fluoroquinolone-resistant E. coli and MRSA were associated with fluoroquinolone use in hospitals and their surrounding communities. METHODS: We measured fluoroquinolone use in 17 US hospitals and their surrounding communities in the year 2000. Data on fluoroquinolone use in hospitals was electronically extracted from billing data. Data on fluoroquinolone use in communities was obtained from IMS health data for all prescriptions filled in pharmacies within a 16-km radius of each hospital. We used hospital antibiograms to determine the percentage of isolates that were fluoroquinolone-resistant E. coli and MRSA, and we performed linear regression to determine the relationship between percentage of resistant isolates and fluoroquinolone use in hospitals and their surrounding communities. RESULTS: There was a significant association between total fluoroquinolone use within hospitals and percentage of S. aureus isolates that were MRSA (r=0.77; P=.0003) and between total fluoroquinolone use in the community and percentage of E. coli isolates that were fluoroquinolone-resistant E. coli (r=0.68; P=.003). Population density within the 16-km radius also correlated with MRSA percentage (r=0.57; P=.015) and fluoroquinolone-resistant E. coli percentage (r=0.85; P=.002), but associations between total fluoroquinolone use and resistance remained significant after adjustment for population density. CONCLUSIONS: In this ecologic analysis, we found associations between fluoroquinolone use in hospitals and methicillin resistance in S. aureus and between fluoroquinolone use in communities and fluoroquinolone resistance in E. coli in hospitals. Antimicrobial use in hospitals and communities may have different relative importance with regard to resistance in different pathogens encountered in hospitals.

Anti-Bacterial Agents↗
PubMed2006

Effectiveness of education and an antibiotic-control program in a tertiary care hospital in Thailand.

BACKGROUND: We conducted a study to evaluate the impact of education and an antibiotic-control program on antibiotic-prescribing practices, antibiotic consumption, antimicrobial resistance, and cost of antibiotics in a tertiary care hospital in Thailand. METHODS: A study of the year before and the year after the intervention was performed. Inpatient antibiotic prescriptions were prospectively observed. Demographic characteristics, hospital unit, indication for antibiotic prescription, appropriateness of antibiotic use, reasons for inappropriate antibiotic use, antibiotic consumption (i.e., the rate of antibiotic use), bacterial resistance, and antibiotic cost data were collected. Interventions included education, introduction of an antibiogram, use of antibiotic prescription forms, and prescribing controls. RESULTS: After the intervention, there was a 24% reduction in the rate of antibiotic prescription (640 vs. 400 prescriptions/1000 admissions; P<.001). The incidence of inappropriate antibiotic use was significantly reduced (42% vs. 20%; P<.001). A sustained reduction in antibiotic use was observed (R2=0.692; P<.001). Rates of use of third-generation cephalosporins (31 vs. 18 defined daily doses [DDDs]/1000 patient-days; P<.001) and glycopeptides (3.2 vs. 2.4 DDDs/1000 patient-days; P=.002) were significantly reduced. Rates of use of cefazolin (3.5 vs. 8.2 DDDs/1000 patient-days; P<.001) and fluoroquinolones (0.68 vs. 1.15 DDDs/1000 patient-days; P<.001) increased. There were no significant changes for other antibiotic classes. Significant reductions in the incidence of infections due to methicillin-resistant Staphylococcus aureus (48% vs. 33.5%; P<.001), extended-spectrum beta -lactamase-producing Escherichia coli (33% vs. 21%; P<.001), extended-spectrum beta -lactamase-producing Klebsiella pneumoniae (30% vs. 20%; P<.001), and third-generation cephalosporin-resistant Acinetobacter baumanii (27% vs. 19%; P<.001) were also observed. Total costs saving were USD 32,231 during the study period. CONCLUSIONS: Education and an antibiotic-control program constituted an effective and cost-saving strategy to optimize antibiotic use in a tertiary care center in Thailand.

Anti-Bacterial Agents↗
PubMed2006

Use of local community hospital data for surveillance of antimicrobial resistance.

We sought to determine whether antimicrobial susceptibility data from a nonteaching community hospital could be used to detect statistically significant local increases in resistance among Streptococcus pneumoniae over a 5-year period. Minimum inhibitory concentrations (MICs) of penicillin and ceftriaxone from 1997-1998 were compared with those from 2000-2001. MICs of penicillin and ceftriaxone for organisms collected in a nonteaching community hospital in central Illinois were used for analysis. The hospital has 224 beds and a catchment area of approximately 40 miles. There were significant increases in MICs of penicillin and ceftriaxone between 1997-1998 and 2000-2001. The MIC of penicillin increased from 0.042 to 0.121 microg/mL (P = .001; 95% confidence interval, -1.713 to -0.388), and the MIC of ceftriaxone increased from 0.028 to 0.071 microg/mL (P = .005; 95% confidence interval, -1.353 to -0.188). There were no significant changes in the percentage of S. pneumoniae isolates that were resistant, intermediate, or susceptible to penicillin and ceftriaxone. MIC data from a community hospital can be used to detect local increases in the rate of resistance before antibiogram data show significant changes. This information is important for demonstrating to physicians the need to review local antibiotic use in the attempt to slow the development of resistant organisms in the community.

Adolescent↗
PubMed1999

Outbreak of Stenotrophomonas maltophilia bacteremia among patients undergoing bone marrow transplantation: association with faulty replacement of handwashing soap.

Using molecular typing methods, we confirmed an outbreak of Stenotrophomonas maltophilia among bone marrow transplant patients. The likely source was a healthcare worker who may have washed with moisturizer instead of soap between patients. Hospital epidemiologists need to go beyond antibiograms when evaluating outbreaks and be vigilant about all aspects of hand washing.

Anti-Bacterial Agents↗
PubMed1999

Bloodstream infections in a neonatal intensive-care unit: 12 years' experience with an antibiotic control program.

OBJECTIVE: To assess the prevalence of gram-positive coccal (GPC), gram-negative bacillary (GNB), and fungal blood-stream infections (BSIs) during a 12-year period in which a consistent antibiotic treatment protocol was in place; to evaluate the efficacy of these antibiotic policies in relation to treatment, to the emergence of bacterial or fungal resistance, and to the occurrence of infection outbreaks or epidemics. STUDY DESIGN: Case series. METHODS: Demographic, clinical, and bacteriological information from 363 infants born during 1986 through 1991 and 1992 through 1997 who developed 433 blood-culture-proven BSIs was analyzed. Early-onset BSIs were defined as those infections discovered within 48 hours of birth, and late-onset BSIs as those that occurred thereafter. Suspected early-onset BSIs were treated with ampicillin and gentamicin, and suspected late-onset BSIs with vancomycin and gentamicin. Antibiotics were changed on the basis of organism antimicrobial susceptibility. RESULTS: Early-onset BSIs were noted in 52 of 21,336 live births and 40 of 20,402 live births during 1986 through 1991 and 1992 through 1997, respectively. GPC (83% due to group B streptococcus [GBS]) accounted for approximately one half of early-onset BSI cases and GNB (68% Enterobacteriaceae) for the remainder. Early-onset GBS declined from 24 to 11 cases (P=.04) and late-onset BSI increased from 111 to 230 cases (P<.01) from the first to the last study period. Sixty-eight percent of late-onset BSIs were due to GPC (primarily coagulase-negative Staphylococcus), 18% to GNB, and 14% to fungus. Over the study period, Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa isolated from the newborn intensivecare unit (unlike those strains from other hospital units) remained fully susceptible to ceftazidime and gentamicin. Although the hospitalwide prevalence of methicillin-resistant Staphylococcus aureus increased, all 17 newborn BSI cases were due to methicillin-sensitive strains. Prevalence of methicillin-resistant coagulase-negative Staphylococcus increased, although all strains remained vancomycin-susceptible, as did the 16 Enterococcus faecalis isolates. All fungi recovered (from 48 patients) were susceptible to amphotericin. CONCLUSION: We observed a decrease in the prevalence of early-onset BSIs due to GBS and an increase in late-onset BSIs due to GPC, GNB, and fungi. The combination of ampicillin and gentamicin for suspected early-onset BSIs and vancomycin and gentamicin for late-onset BSIs has been successful for treatment of individual patients without the occurrence of infection outbreaks or the emergence of resistance. Controlled antibiotic programs and periodic evaluations based on individual unit and not on hospitalwide antibiograms are advisable.

Anti-Bacterial Agents↗
PubMed1999

Implementation of an interactive computer-assisted infection monitoring program at the bedside.

A new computer-assisted infection monitoring (CAI) software program has been developed for use in an intensive-care unit (ICU). By means of an interactive dialogue with physicians at the bedside, infection diagnoses and therapeutic decisions were recorded prospectively during a 3-month test period. By linking epidemiological data with information about therapeutic decisions, CAI could assess the quality of the therapeutic decisions. Antibiotics chosen empirically before the availability of any culture results, matched the antibiotic susceptibility patterns of the subsequently identified pathogens in 74% of the cases. Therapy chosen in collaboration with the computer after the pathogen was known, but before sensitivity results were available, corresponded with the eventual antibiograms of the microorganisms in 90% of the cases. Data analysis by CAI allowed us to assess critically the diagnostic and therapeutic habits in our ICU. Using the query-by-example method, CAI automatically calculated device-associated infection rates.

Adolescent↗
PubMed2002

Serratia bacteremia in a large university hospital: trends in antibiotic resistance during 10 years and implications for antibiotic use.

OBJECTIVE: To identify antibiotic resistance trends and risk factors for resistance of Serratia species to third-generation cephalosporins. DESIGN: Retrospective survey of medical records. SETTING: A 2,200-bed, tertiary-care hospital. PATIENTS: One hundred twenty-two patients with Serratia bacteremia between January 1991 and June 2001. METHODS: Infectious disease physicians collected data from medical records regarding patient demographics, underlying disease or condition, portal of entry, microorganism, antibiogram, complications, antibiotics received, and outcome. RESULTS: Among 122 Serratia isolates, 117 (95.9%) were Serratia marcescens and 110 (90.2%) were of nosocomial origin. During the study period, the 122 isolates showed a high rate of resistance to third-generation cephalosporins (45.9%) and extended-spectrum penicillins (56.6%). The resistance rate to ciprofloxacin was 32.0%. The resistance rate to third-generation cephalosporins increased from 31.7% for 1991 to 1995 to 54.9% for 1996 to 1998 and 50.0% for 1999 to 2001. In the multivariate analysis, prior use of a second-generation cephalosporin (adjusted odds ratio [OR], 5.90; 95% confidence interval [CI90], 1.41 to 24.6; P = .015) or a third-generation cephalosporin (OR, 3.26; CI95, 1.20 to 8.87; P = .020) was a strong independent risk factor for resistance to third-generation cephalosporins. The overall case-fatality rate was 25.4% (Serratia bacteremia-related case-fatality rate, 13.1%). CONCLUSION: Prior use of a second- or third-generation cephalosporin was the most important risk factor for bacteremia with Serratia resistant to third-generation cephalosporins, suggesting the need for antibiotic control. The potential role of patient-to-patient spread could not be fully evaluated in this retrospective study.

Adolescent↗
PubMed2003

Rates of carriage of methicillin-resistant and methicillin-susceptible Staphylococcus aureus in an outpatient population.

OBJECTIVES: To assess the prevalence of and the clinical features associated with asymptomatic Staphylococcus aureus colonization in a healthy outpatient population, and to compare the characteristics of colonizing methicillin-resistant S. aureus (MRSA) strains with those of strains causing infection in our community and hospital. SETTING: Outpatient military clinics. METHODS: Specimens were obtained from the nares, pharynx, and axillae of 404 outpatients, and a questionnaire was administered to obtain demographic and risk factor information. MRSA strains were typed by pulsed-field gel electrophoresis (PFGE) and evaluated for antibiotic susceptibility. Antibiograms of study MRSA strains were compared with those of MRSA strains causing clinical illness during the same time period. RESULTS: Methicillin-susceptible S. aureus (MSSA) colonization was present in 153 (38%) of the 404 asymptomatic outpatients, and MRSA colonization was present in 8 (2%). Detection of colonization was highest from the nares. No clinical risk factor was significantly associated with MRSA colonization; however, a tendency was noted for MRSA to be more common in men and in those who were older or who had been recently hospitalized. All colonizing MRSA strains had unique patterns on PFGE. In contrast to strains responsible for hospital infections, most colonizing isolates of MRSA were susceptible to oral antibiotics. CONCLUSIONS: MRSA and MSSA colonization is common in our outpatient population. Colonization is best detected by nares cultures and most carriers of MRSA are without apparent predisposing risk factors for acquisition. Colonizing isolates of MRSA are heterogeneous and, unlike nosocomial isolates, often retain susceptibility to other non-beta-lactam antibiotics.

Adolescent↗
PubMed2003

Analysis of three outbreaks due to Klebsiella species in a neonatal intensive care unit.

OBJECTIVE: To investigate the clinical, microbiological, and epidemiologic features of three outbreaks caused by Klesiella during 3 years. SETTING: Neonatal intensive care unit of a university hospital. PATIENTS: Thirty affected neonates. METHODS: Data were collected through chart reviews and conversations with physicians. Screening samples were obtained from the staff, the neonates, and the environment. Antibiogram typing and arbitrarily primed polymerase chain reaction-based fingerprinting were used to type the strains. RESULTS: The first outbreak had 13 K. pneumoniae strains isolated. The second outbreak had 10 K. oxytoca strains isolated. The third outbreak had 20 K. pneumoniae strains isolated. More than half of the patients had low birth weights, were premature, and underwent mechanical ventilation and intravenous catheterization. Approximately three-fourths of the patients died. The isolates tested were completely susceptible to meropenem, cefoxitin, and ciprofloxacin and were resistant to cephalothin. More than half of these strains were resistant to many beta-lactam antibiotics, amikacin, and trimethoprim/sulfamethoxazole. Typing procedures yielded 3 antibiotypes and 3 genotypes among the isolates of the first outbreak, 3 antibiotypes with 1 subtype and 2 genotypes with 1 subtype in the second outbreak, and 2 antibiotypes and 2 genotypes in the third outbreak. CONCLUSIONS: Klebsiella outbreaks mainly affected premature neonates with intravenous catheters, mechanical ventilation, or both. The high mortality rate (76.7%) was notable. Resistance to multiple antibiotics, but mainly to broad-spectrum beta-lactam antibiotics, was observed, particularly in K. pneumoniae isolates. Molecular typing indicated that the three outbreaks were not related to one other.

Anti-Bacterial Agents↗
PubMed2005

Variation in the use of procedures to monitor antimicrobial resistance in U.S. hospitals.

BACKGROUND: Antimicrobial resistance is a growing clinical and public health crisis. Experts have recommended measures to monitor antimicrobial resistance; however, little is known regarding their use. OBJECTIVE: We describe the use of procedures to detect and report antimicrobial resistance in U.S. hospitals and the organizational and epidemiologic factors associated with their use. METHODS: In 2001, we surveyed laboratory directors (n = 108) from a random national sample of hospitals. We studied five procedures to monitor antimicrobial resistance: (1) disseminating antibiograms to physicians at least annually, (2) notifying physicians of antimicrobial-resistant infections, (3) reporting susceptibility results within 24 hours, (4) using automated testing procedures, and (5) offering molecular typing. Explanatory variables included organizational characteristics and patterns of antimicrobial resistance for oxacillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, quinolone-resistant Escherichia coli, and extended-spectrum beta-lactamase-producing Klebsiella species. Generalized estimating equations accounting for the correlation among outcomes at the facility level were used to identify predictors of the five outcomes. RESULTS: Use of the procedures ranged from 85% (automated testing) to 33% (offering molecular typing) and was related to teaching hospital status (OR, 3.1; CI95, 1.5-6.5), participation of laboratory directors on the infection control committee (OR, 1.7; CI95, 1.1-2.8), and having at least one antimicrobial-resistant pathogen with a prevalence greater than 10% (OR, 2.2; CI95, 1.4-3.3). CONCLUSION: U.S. hospitals underutilize procedures to monitor the spread of antimicrobial resistance. Use of these procedures varies and is related to organizational and epidemiologic factors. Further efforts are needed to increase their use by hospitals.

Cross Infection↗
PubMed2005

A pilot study of antibiotic cycling in the community hospital setting.

OBJECTIVE: To assess the feasibility of a quarterly antibiotic cycling program at two community hospitals and to evaluate its safety and impact on antibiotic use, expenditures, and resistance. DESIGN: Nonrandomized, longitudinal cohort study. SETTING: Two community hospitals, one teaching and one non-teaching. PATIENTS: Adult medical and surgical inpatients requiring empiric antibiotic therapy. INTERVENTION: We developed and implemented a treatment protocol for the empiric therapy of common infections. Between July 2000 and June 2002, antibiotics were cycled quarterly; quinolones, beta-lactam-inhibitor combinations, and cephalosporins were used. Protocol adherence, adverse drug events, nosocomial infections, antibiotic use and expenditures, resistance among clinical isolates, and length of stay were assessed during eight quarters. RESULTS: Physicians adhered to the protocol for more than 96% of 2,494 eligible patients. No increases in nosocomial infections or adverse drug events were attributed to the cycling protocol. Antibiotic acquisition costs increased 31%; there was a 14.7% increase in antibiotic use. Length of stay declined by 1 day. Quarterly variability in the prevalence of vancomycin-resistant enterococci and ceftazidime resistance among combined gram-negative organisms were noted. CONCLUSIONS: Implementation of an antibiotic cycling program is feasible in a community hospital setting. No adverse safety concerns were identified. Antibiotic cycling was more expensive, partly due to an increase in antibiotic use to optimize initial empiric therapy. Quarterly antibiogram patterns suggested that antibiotic cycling may have impacted resistance, although the small number of isolates precluded statistical analysis. Further assessment of this approach is necessary to determine its relationship to antimicrobial resistance.

Adult↗
PubMed2000

Potential role of pharmacokinetics, pharmacodynamics, and computerized databases in controlling bacterial resistance.

Bacterial resistance to antibiotics continues to be a problem, in spite of increased knowledge of resistance mechanisms. Due to the multifactorial nature of bacterial resistance, studies that evaluate the association between antimicrobial exposure and emergence of resistance may fail to find a relationship unless other factors, in particular the association between patient-pathogen pharmacokinetics (PK) and pharmacodynamics (PD) and the emergence of bacterial resistance, are evaluated as well. It has been hypothesized that, in conjunction with good infection control practices, cycling of antimicrobial agents may prove to be effective in reducing resistance emergence. There is some indication that there may be a relationship between the level of antibiotic exposure and the probability of emergence of bacterial resistance. As shown in our companion article in this supplement, factors associated with ciprofloxacin resistance in Pseudomonas aeruginosa included increased length of stay prior to isolation, exposure to ciprofloxacin, and respiratory tract site of bacterial isolation. However, in patients who received ciprofloxacin therapy, when exposure was at an area under the 24-hour inhibitory concentration curve (AUIC24)>110 (microg x h/mL)/microg/mL, resistance was decreased to 11%, a rate similar to that seen in respiratory isolates not exposed to ciprofloxacin (7%). While the length of time the patient spends in the hospital and the site of infection cannot be controlled, by using PK and PD principles for dosing of ciprofloxacin, the emergence of ciprofloxacin resistance in P aeruginosa may be reduced. Prospective antibiotic-cycling studies may help to determine not only the impact of antibiotic cycling on the institution's antibiogram but also, through the use of PK and PD principles, may help to determine appropriate dosing schedules for antibiotics in order to reduce the probability of emergence of bacterial resistance.

Anti-Bacterial Agents↗
PubMed2006

Molecular characterization of methicillin-resistant Staphylococcus aureus spread by neonates transferred from primary obstetrics clinics to a tertiary care hospital in Korea.

OBJECTIVE: To investigate the characteristics and origins of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from neonatal patients admitted to a tertiary care hospital from local and primary care obstetrics clinics. DESIGN: Molecular typing study. SETTING: A 1,278-bed tertiary care hospital (Samsung Medical Center) and 2 primary obstetrics clinics in Seoul, Korea. PATIENTS: The genotypic characteristics of 12 MRSA samples isolated from 11 neonatal patients transferred from 2 primary care obstetrics clinics to a tertiary care hospital were investigated by means of multilocus sequence typing, spa (staphylococcal protein A) typing, and SCCmec typing. Ten MRSA strains isolated from workers and environments in the associated obstetrics clinics were also investigated. RESULTS: Although the antibiograms of isolates from 2 obstetrics clinics differed, no strain showed multidrug resistance to antimicrobials. Multilocus sequence typing analysis showed that all 22 MRSA isolates analyzed in this study had sequence type 1 (with the allelic profile 1-1-1-1-1-1-1), sequence type 493 (62-1-1-1-1-1-1), or a novel sequence type (25-1-1-1-1-1-1) and that all belonged to a single clonal complex (clonal complex 1). Moreover, they all contained SCCmec type IVA and the identical spa type (UJEBKBP). These genotypic characteristics are similar to those of typical community-associated MRSA strains rather than the hospital-acquired MRSA strains common in Korea. CONCLUSION: The findings of this study suggest that community-acquired MRSA strains can spread in primary care clinics and be imported into tertiary care settings.

Bacterial Typing Techniques↗