Evaluation of current activities of fluoroquinolones against gram-negative bacilli using centralized in vitro testing and electronic surveillance

Global prevalence and distribution of antibiotic resistance among clinical isolates of Stenotrophomonas maltophilia: A systematic review and meta-analysis

OBJECTIVES

Stenotrophomonas maltophilia (S. maltophilia), an opportunistic pathogen, causes infection in patients undergoing immunosuppressive therapy, mechanical ventilation, or catheters and in long-term hospitalized patients. Due to its extensive resistance to various antibiotics and chemotherapeutic agents, S. maltophilia is challenging to treat. Using case reports, case series, and prevalence studies, the current study provides a systematic review and meta-analysis of antibiotic resistance profiles across clinical isolates of S. maltophilia.

METHODS

A systematic literature search was performed for original research articles published in Medline, Web of Science, and Embase databases from 2000 to 2022. Statistical analysis was performed using STATA 14 software to report antibiotic resistance of S. maltophilia clinical isolates worldwide.

RESULTS

223 studies (39 case reports/case series and 184 prevalence studies) were collected for analysis. A meta-analysis of prevalence studies demonstrated that the most antibiotic resistance worldwide was to levofloxacin, trimethoprim-sulfamethoxazole (TMP/SMX), and minocycline (14.4%, 9.2%, and 1.4%, respectively). Resistance to TMP/SMX (36.84%), levofloxacin (19.29%), and minocycline (1.75%) were the most prevalent antibiotic resistance types found in evaluated case reports/case series studies. The highest resistance rate to TMP/SMX was reported in Asia (19.29%), Europe (10.52%), and America (7.01%), respectively.

CONCLUSION

Considering the high resistance to TMP/SMX, more attention should be paid to patients' drug regimens to prevent the emergence of multidrug-resistant S. maltophilia isolates.

Global prevalence and antibiotic resistance in clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

Introduction

Stenotrophomonas maltophilia is a little-known environmental opportunistic bacterium that can cause broad-spectrum infections. Despite the importance of this bacterium as an emerging drug-resistant opportunistic pathogen, a comprehensive analysis of its prevalence and resistance to antibiotics has not yet been conducted.

Methods

A systematic search was performed using four electronic databases (MEDLINE via PubMed, Embase, Scopus, and Web of Science) up to October 2019. Out of 6,770 records, 179 were documented in the current meta-analysis according to our inclusion and exclusion criteria, and 95 studies were enrolled in the meta-analysis.

Results

Present analysis revealed that the global pooled prevalence of S. maltophilia was 5.3 % [95% CI, 4.1-6.7%], with a higher prevalence in the Western Pacific Region [10.5%; 95% CI, 5.7-18.6%] and a lower prevalence in the American regions [4.3%; 95% CI, 3.2-5.7%]. Based on our meta-analysis, the highest antibiotic resistance rate was against cefuroxime [99.1%; 95% CI, 97.3-99.7%], while the lowest resistance was correlated with minocycline [4·8%; 95% CI, 2.6-8.8%].

Discussion

The results of this study indicated that the prevalence of S. maltophilia infections has been increasing over time. A comparison of the antibiotic resistance of S. maltophilia before and after 2010 suggested there was an increasing trend in the resistance to some antibiotics, such as tigecycline and ticarcillin-clavulanic acid. However, trimethoprim-sulfamethoxazole is still considered an effective antibiotic for treating S. maltophilia infections.

Bacteriological Study of Urinary Tract Infections among Pregnant Women in Al Samawa City of Iraq

Pregnancy causes some changes in pregnant women due to mechanical and hormonal changes that lead to ureteral dilatation and urinary stasis which in turn contribute to an increased risk of developing urinary tract infection (UTI). This study aimed to determine the frequency of urinary tract infections among pregnant women in Samawa city, Iraq, and examine the isolated organisms. In total, 210 and 55 urine samples were collected from pregnant and non-pregnant women with clinical signs and symptoms of UTI who were hospitalized in the Obstetric and Pediatric Hospital in Samawa, Iraq, respectively. The data collected from each woman included their age, gestational period, parity, level of education, and residence. The frequency of urinary tract infections among the studied woman was 86%. Escherichia coli (38.6%), staphylococcus aureus (20.4%), and Proteus mirabilis (12.7%) were the most frequently isolated bacteria in the current study. According to the recorded data in this study, 86% of the infections in pregnant women occurred in the age group of 25-34 years (52.4%) and the 3rd trimester of pregnancy (49.1%). On the other hand, the results revealed that the infection rate in women with one to three pregnancies was 50.2% more than non-pregnant women. The findings of the current study showed that the highest rate of infection was observed in women who were in the age range of 25-34 years (52.4%). This can be explained by the fact that women often experience the highest reproductive activity during this period. In fact, in this period of life, women are most prone to sexual activity which predisposes them to the introduction of microorganisms to the urinary tract which causes infection. The recorded data showed that UTI became more prevalent with the progress of pregnancy, accounting for 49.1% of infections occurring in the third trimester of pregnancy. Parity and frequent pregnancies are other factors that account for 50.2% of UTI. The prevalence of UTI in women with 1 to 3 children was 58.5%. Moreover, the rate of UTI was 61.3% among pregnant women who attended the antenatal care unit, which was the highest risk of UTI among the pregnant participants. In the non-pregnant women, the prevalence of UTI was 50.2 at the age range of 6-12 years. Based on the obtained results, pregnant women were more vulnerable to renal infection. On the other hand, the concurrence of UTI was positively influenced by sexual activity and pregnancy.

The synergistic effect of hydroalcoholic extracts of Origanum vulgare, Hypericum perforatum and their active components carvacrol and hypericin against Staphylococcus aureus

AIM

This study was designed to evaluate the synergistic activities of hydroalcoholic extracts of medicinal plants Origanum vulgare and Hypericum perforatum and their active components, carvacrol and hypericin against Staphylococcus aureus.

METHODS

The synergistic effects of the plants, as well as carvacrol and hypericin, were examined using a checkered method against S. aureus (ATCC 12600).

RESULTS

A fractional inhibitory concentration of 0.5 was obtained for combination of O. vulgare and H. perforatum and 0.49 for combination of the active ingredients carvacrol and hypericin, both of which indicated a synergistic effect.

CONCLUSION

This preliminary evaluation demonstrated a synergistic property of O. vulgare and H. perforatum extracts in treating S. aureus infection. This study indicates that combination of the plants, as well as combination of carvacrol and hypericin, might be used as a new antibacterial strategy against S. aureus.

Optimization adsorption of norfloxacin onto polydopamine microspheres from aqueous solution: Kinetic, equilibrium and adsorption mechanism studies

Polydopamine microspheres (PDMPs) synthesized by a facile solution oxidation method were adopted as a potential adsorbent for the removal of Norfloxacin (NOR) from aqueous solution. The morphologies and properties of PDMPs were characterized using TEM, SEM, FTIR and pH_PZC. Parameters effects such as contact time, initial pH, initial concentration and ionic strength on the adsorption capacity of NOR onto PDMPs were studied. To maximize NOR removal from liquid phase, Box-Behnken experimental design (BBD) combined with response surface modeling (RSM) was employed based on the 17 preliminary experiments at 308 K. Optimum contact time, initial NOR concentration and initial pH value were found to be 97 min, 303 mg·L^-1 and 6.6, respectively, the corresponding NOR removal capacity was found to be 307 mg·g^-1. Batch adsorption experiments under the optimal conditions were conducted to investigate kinetics, thermodynamics and adsorption isotherm. Kinetic analysis confirmed that the kinetic data were well described by Pseudo-second order model. The experimental equilibrium data were well fitted by Langmuir, Redlich-Peterson, Koble-Corrigan and Dubinin-Radushkevich models. Thermodynamic parameters such as Gibbs free energy, enthalpy and entropy were calculated and the results indicated that the NOR adsorption onto PDMPs was spontaneous and endothermic. The adsorption process may be attributed to the electrostatic interaction, the formation of hydrogen bonds or π-π stacking interactions among the polydopamine (PDA) and NOR molecule.

Action of cholecalciferol and alpha-tocopherol on Staphylococcus aureus efflux pumps

Alpha-tocopherol is one the most abundant and biologically active isoforms of vitamin E. This compound is a potent antioxidant and one of most studied isoforms of vitamin E. Vitamin D3 (cholecalciferol) is an important nutrient for calcium homeostasis and bone health, that has also been recognized as a potent modulator of the immune response. Methicillin-resistant Staphylococcus aureus (MRSA) is the most important causative agent of both nosocomial and community-acquired infections. The aim of this study was to evaluate the inhibitory effect of alpha-tocopherol and cholecalciferol on both S. aureus and multidrug resistant S. aureus efflux pumps. The RN4220 strain has the plasmid pUL5054 that is the carrier of gene that encodes the macrolide resistance protein (an efflux pump) MsrA; the IS-58 strain possesses the TetK tetracycline efflux protein in its genome and the 1199B strain resists to hydrophilic fluoroquinolones via a NorA-mediated mechanism. The antibacterial activity was evaluated by determining the Minimal Inhibitory Concentration (MIC) and a possible inhibition of efflux pumps was associated to a reduction of the MIC. In this work we observed that in the presence of the treatments there was a decrease in the MIC for the RN4220 and IS-58 strains, suggesting that the substances presented an inhibitory effect on the efflux pumps of these strains. Significant efforts have been done to identify efflux pump inhibitors (EPIs) from natural sources and, therefore, the antibacterial properties of cholecalciferol and alpha-tocopherol might be attributed to a direct effect on the bacterial cell depending on their amphipathic structure.

Coding of Electronic Laboratory Reports for Biosurveillance, Selected United States Hospitals, 2011

Objective

Electronic laboratory reporting has been promoted as a public health priority. The Office of the U.S. National Coordinator for Health Information Technology has endorsed two coding systems: Logical Observation Identifiers Names and Codes (LOINC) for laboratory test orders and Systemized Nomenclature of Medicine-Clinical Terms (SNOMED CT) for test results.

Materials and Methods

We examined LOINC and SNOMED CT code use in electronic laboratory data reported in 2011 by 63 non-federal hospitals to BioSense electronic syndromic surveillance system. We analyzed the frequencies, characteristics, and code concepts of test orders and results.

Results

A total of 14,028,774 laboratory test orders or results were reported. No test orders used SNOMED CT codes. To describe test orders, 77% used a LOINC code, 17% had no value, and 6% had a non-informative value, “OTH”. Thirty-three percent (33%) of test results had missing or non-informative codes. For test results with at least one informative value, 91.8% had only LOINC codes, 0.7% had only SNOMED codes, and 7.4% had both. Of 108 SNOMED CT codes reported without LOINC codes, 45% could be matched to at least one LOINC code.

Conclusion

Missing or non-informative codes comprised almost a quarter of laboratory test orders and a third of test results reported to BioSense by non-federal hospitals. Use of LOINC codes for laboratory test results was more common than use of SNOMED CT. Complete and standardized coding could improve the usefulness of laboratory data for public health surveillance and response.

Levofloxacin: update and perspectives on one of the original ‘respiratory quinolones’

The fluoroquinolone class of antimicrobials has enjoyed enormous clinical and marketing success over the past 20 years. These drugs have proven to be extremely useful in a broad range of clinical indications including both common community-acquired as well as nosocomial bacterial infections. Levofloxacin (Levaquin, Tavanic), like ciprofloxacin (Cipro), has established an enviable record of safe and efficacious use, and in many ways has become the agent against which all of the newer fluoroquinolones are judged. New clinical indications in complicated skin and skin structure infections, nosocomial pneumonia and chronic bacterial prostatitis continue to expand the important role of this already versatile drug. In addition, the use of 'short-course, high-dose' therapies are being studied in indications, such as community-acquired pneumonia, in an effort to optimize the efficacy and convenience of the drug while minimizing the future development of resistance. As the use of levofloxacin continues to expand, future challenges will include the threat of increasing antimicrobial resistance and the availability of newer alternative agents, both newer fluoroquinolones as well as agents of other antibiotic classes.

Impact of antibiotic use during hospitalization on the development of gastrointestinal colonization with Escherichia coli with reduced fluoroquinolone susceptibility

OBJECTIVE

Infections due to fluoroquinolone-resistant Escherichia coli (FQREC) are associated with significant morbidity and mortality. Fluoroquinolone resistance likely arises at the level of gastrointestinal colonization. The objective of this study was to identify risk factors for the development of FQREC gastrointestinal tract colonization in hospitalized patients, including the impact of antibiotics prescribed during hospitalization.

DESIGN

A prospective cohort study was conducted from 2002 to 2004 within a university health system.

METHODS

Hospitalized patients initially colonized with fluoroquinolone-susceptible E. coli were followed up with serial fecal sampling for new FQREC colonization or until hospital discharge or death. A Cox proportional hazards regression model was developed to identify risk factors for new FQREC colonization, with antibiotic exposure modeled as time-varying covariates.

RESULTS

Of 395 subjects, 73 (18.5%) became newly colonized with FQREC. Length of stay before sampling (hazard ratio [HR], 1.02 [95% confidence interval (CI), 1.1-1.03]; P = .003) and malignancy (HR, 0.37 [95% CI, 0.21-0.67]; P = .001) were significantly associated with the development of FQREC colonization. In addition, receipt of a first-generation cephalosporin (HR, 1.19 [95% CI, 1.10-1.29]; P < .001) or cefepime (HR, 1.05 [95% CI, 1.00-1.10]; P = .048) during hospitalization increased the risk of new FQREC colonization.

CONCLUSIONS

The acquisition of FQREC in the hospital setting is complex, and antimicrobial stewardship programs should take into account patterns of antibiotic use in implementing strategies to reduce the development of new FQREC colonization. Future studies are needed to identify risk factors for infection in hospitalized patients newly colonized with FQREC.

Analysis of risk factors associated with antibiotic-resistant Escherichia coli

Antimicrobial-resistant bacteria represent a major threat to human and animal health. We compared equine fecal samples (n=264) from 138 horses from hospital and nonhospital (livery stable and riding school) premises in North West England to determine the prevalence of Escherichia coli, Salmonella, and Campylobacter and rates of antimicrobial-resistant E. coli strains. Campylobacter jejuni was detected only in hospitalized horses (1.1%), and no Salmonella was identified. Data analysis of the horses' management and veterinary treatments (Tx) identified risk factors associated with shedding of antimicrobial-resistant E. coli. The hospital was the major source of resistant and multi-drug-resistant (MDR) E. coli. Moreover, shedding of antimicrobial-resistant E. coli was associated significantly with hospitalization for a gastrointestinal problem (odds ratio [OR]:±95% confidence intervals=8.50:1.79-40.32), receipt of oral antimicrobial Tx (OR=3.52:1.11-11.10), multiple antimicrobial Tx in hospital (OR/Tx=1.05:1.01-1.09), or geldings (OR=4.62:1.23-17.46). Interestingly, intravenous antimicrobial Tx was negatively associated with shedding of antimicrobial-resistant E. coli (OR=0.18:0.04-0.76). MDR E. coli was associated with hospitalization, antimicrobial Tx in hospital (OR/Tx=3.65:1.54-8.68), and increased age (OR/year=1.11:1.03-1.19). Thus, equine hospitals in this geographic location appear to be an important source of antimicrobial-resistant and MDR E. coli strains, but unlikely reservoirs of Salmonella or Campylobacter. Thus, it is important to moderate antimicrobial Tx given to hospitalized horses to lessen exposure and fecal shedding of resistant pathogens.

QRDR mutations, efflux system & antimicrobial resistance genes in enterotoxigenic Escherichia coli isolated from an outbreak of diarrhoea in Ahmedabad, India

BACKGROUND & OBJECTIVES

Diverse mechanisms have been identified in enteric bacteria for their adaptation and survival against multiple classes of antimicrobial agents. Resistance of bacteria to the most effective fluoroquinolones have increasingly been reported in many countries. We have identified that most of the enterotoxigenic Escherichia coli (ETEC) were resistant to several antimicrobials in a diarrhoea outbreak at Ahmedabad during 2000. The present study was done to identify several genes responsible for antimicrobial resistance and mobile genetic elements in the ETEC strains.

METHODS

Seventeen ETEC strains isolated from diarrhoeal patients were included in this study. The antimicrobial resistance was confirmed by conventional disc diffusion method. PCR and DNA sequencing were performed for the identification of mutation in the quinolone resistance-determining regions (QRDRs). Efflux pump was tested by inhibiting the proton-motive force. DNA hybridization assay was made for the detection of integrase genes and the resistance gene cassettes were identified by direct sequencing of the PCR amplicons.

RESULTS

Majority of the ETEC had GyrA mutations at codons 83 and 87 and in ParC at codon 80. Six strains had an additional mutation in ParC at codon 108 and two had at position 84. Plasmid-borne qnr gene alleles that encode quinolone resistance were not detected but the newly described aac(6')-Ib-cr gene encoding a fluoroquinolne-modifying enzyme was detected in 64.7 per cent of the ETEC. Class 1 (intI1) and class 2 (intI2) integrons were detected in six (35.3%) and three (17.6%) strains, respectively. Four strains (23.5%) had both the classes of integrons. Sequence analysis revealed presence of dfrA17, aadA1, aadA5 in class 1, and dfrA1, sat1, aadA1 in class 2 integrons. In addition, the other resistance genes such as tet gene alleles (94.1%), catAI (70.6%), strA (58.8%), bla TEM-1 (35.2%), and aphA1-Ia (29.4%) were detected in most of the strains.

INTERPRETATION & CONCLUSIONS

Innate gene mutations and acquisition of multidrug resistance genes through mobile genetic elements might have contributed to the emergence of multidrug resistance (MDR) in ETEC. This study reinforces the necessity of utilizing molecular techniques in the epidemiological studies to understand the nature of resistance responsible for antimicrobial resistance in different species of pathogenic bacteria.

Integrated Multilevel Surveillance of the World's Infecting Microbes and Their Resistance to Antimicrobial Agents

Microbial surveillance systems have varied in their source of support; type of laboratory reporting (patient care or reference); inclusiveness of reports filed; extent of microbial typing; whether single hospital, multihospital, or multicountry; proportion of total medical centers participating; and types, levels, integration across levels, and automation of analyses performed. These surveillance systems variably support the diagnosis and treatment of patients, local or regional infection control, local or national policies and guidelines, laboratory capacity building, sentinel surveillance, and patient safety. Overall, however, only a small fraction of available data are under any surveillance, and very few data are fully integrated and analyzed. Advancing informatics and genomics can make microbial surveillance far more efficient and effective at preventing infections and improving their outcomes. The world's microbiology laboratories should upload their reports each day to programs that detect events, trends, and epidemics in communities, hospitals, countries, and the world.

Fluoroquinolone-resistant uncomplicated urinary tract infections, Chinese herbal medicine may provide help

We assessed the effects of Chinese herbs on the uncomplicated urinary tract infections (UTIs) in women caused by fluoroquinolone-resistant strains. A total of 56 pre-menopausal women with uncomplicated UTIs caused by fluoroquinolone-resistant strains were included. Urine cultures were carried out. All organisms were proved to be fluoroquinolone-resistant at baseline. The patients were orally administrated Chinese herbal concoction for ten days. Chinese herbal concoction eradicated the primary pathogen in 71.4% of the patients at the 1-week follow-up. Among the 20 patients who had bacteriologic failures in the Day 5 of treatment, 2 developed superinfection. Of the failures in the group, Proteus mirabilis, Staphylococcus epidermidis and Providencia rettgeri were implicated in 50.0%, 50.0% and 100.0% of the failures, respectively. The clinical outcomes were also good, with cure or improvement for more than 80% of all subjects. About 14% of the study subjects reported at least one potential adverse event. The adverse events most frequently reported were nausea and diarrhea. All patients tolerated the symptoms. The adverse reactions did not prevail after discontinuation of the medication. Chinese herbal therapy may be an acceptable alternative for the treatment of uncomplicated UTIs caused by fluoroquinolone-resistant uropathogens.

Article Commentary: Strategies in the Prevention and Management of Ventilator-Associated Pneumonia

Ventilator-associated pneumonia (VAP) is a leading cause of morbidity and mortality in the intensive care unit. Prevention of VAP is possible through the use of several evidence-based strategies intended to minimize intubation, the duration of mechanical ventilation, and the risk of aspiration of oropharyngeal pathogens. Current data favor the quantitative analysis of lower respiratory tract cultures for the diagnosis of VAP, accompanied by the initiation of broad-spectrum empiric antimicrobial therapy based on patient risk factors for infection with multi-drug-resistant pathogens and data from unit-specific antibiograms. Eventual choice of antibiotic and duration of therapy are selected based on culture results and patient stability, with an emphasis on minimization of unnecessary antibiotic use.

Early complications of primary total hip replacement performed with a two-incision minimally invasive technique. Surgical technique

BACKGROUND

Total hip replacement performed through a small incision theoretically results in less trauma to the underlying structures, reduced blood loss, less pain, and a shorter hospital stay, but it may result in increased complications, particularly early in a surgeon's experience with a new technique. In the present study, we reviewed the early results of two techniques involving the use of smaller incisions; specifically, we evaluated one series of primary total hip replacements that had been performed through two small incisions and another series of total hip replacements that had been performed through a single small incision.

METHODS

Eighty-nine consecutive primary total hip replacements were performed with use of the two-incision technique as described by Mears and Berger; all procedures were performed without cement and with use of fluoroscopic guidance. Outcomes data were reviewed at a minimum of six months following the procedure. The results of these procedures were retrospectively compared with those of a historical control series of ninety-six total hip replacements that had been performed by the same surgeon with use of a single miniincision technique. No special attempt was made to discharge any patient early from the hospital. In preparation for the use of the two-incision technique, the surgeon attended a two-day seminar that included cadaveric training and mentoring by surgeons who had experience with this technique.

RESULTS

In the two-incision group, nine patients (nine hips; 10%) required repeat surgery because of a femoral fracture that had been identified postoperatively (two hips), dislocation (one hip), a wound complication (two hips), or subsidence and loosening of the femoral implant (four hips). Twenty-two patients (twenty-two hips; 25%) sustained an injury of the lateral femoral cutaneous nerve, and one patient (one hip) had a neuropraxia of the femoral nerve. In the comparative series of ninety-six total hip arthroplasties that had been performed with use of a single mini-incision and a direct lateral exposure of the hip joint, the overall complication rate was 6% (six of ninety-six) and the reoperation rate was 3% (three of ninety-six). The rate of complications associated with the two-incision technique decreased significantly as the surgeon gained experience with the procedure (p = 0.0202).

CONCLUSIONS

Although total hip arthroplasty with use of the two-incision technique was performed by a surgeon who was experienced in the performance of total hip replacement surgery with use of a single small incision, the rates of complications and repeat surgery associated with the two-incision technique initially were very high. While the rate diminished with increasing experience, total hip replacement with use of two incisions and fluoroscopic guidance is a technically demanding procedure that may be associated, especially initially, with higher rates of complications and repeat surgery.

Fluoroquinolone-resistant urinary isolates of Escherichia coli from outpatients are frequently multidrug resistant: results from the North American Urinary Tract Infection Collaborative Alliance-Quinolone Resistance study

Ciprofloxacin-resistant Escherichia coli isolates (n = 1,858) from outpatient midstream urine specimens at 40 North American clinical laboratories in 2004 to 2005 were frequently resistant to ampicillin (79.8% of isolates) and trimethoprim-sulfamethoxazole (66.5%); concurrent resistance to cefdinir (9.0%) or nitrofurantoin (4.0%) was less common. Only 10.8% of isolates were resistant to ciprofloxacin alone. Fluoroquinolone-resistant isolates of E. coli from urine were frequently multidrug resistant.

Bloodstream infections caused by extended-spectrum-beta-lactamase-producing Klebsiella pneumoniae: risk factors, molecular epidemiology, and clinical outcome

Bloodstream infections caused by extended-spectrum-beta-lactamase (ESBL)-producing Klebsiella pneumoniae isolates are a major concern for clinicians, since they markedly increase the rates of treatment failure and death. One hundred forty-seven patients with K. pneumoniae bloodstream infections were identified over a 5-year period (January 1999 to December 2003). The production of ESBLs in bloodstream isolates was evaluated by molecular methods. A retrospective case-case-control study was conducted to identify risk factors for the isolation of ESBL-producing K. pneumoniae or non-ESBL-producing K. pneumoniae isolates in blood cultures. Forty-eight cases infected with ESBL-producing K. pneumoniae isolates and 99 cases infected with non-ESBL-producing K. pneumoniae isolates were compared to controls. Risk factors for isolation of ESBL-producing K. pneumoniae isolates were exposure to antibiotic therapy (odds ratio [OR], 11.81; 95% confidence interval [CI], 2.72 to 51.08), age (OR, 1.14; 95% CI, 1.08 to 1.21), and length of hospitalization (OR, 1.10; 95% CI, 1.04 to 1.16). Independent determinants for isolation of non-ESBL-producing K. pneumoniae were previous urinary tract infection (OR, 8.50; 95% CI, 3.69 to 19.54) and length of hospitalization (OR, 1.07; 95% CI, 1.04 to 1.10). When the initial response was assessed at 72 h after antimicrobial therapy, the treatment failure rate for the ESBL-producing K. pneumoniae-infected group was almost twice as high as that of the non-ESBL-producing K. pneumoniae-infected group (31% versus 17%; OR, 2.19; 95% CI, 0.98 to 4.89). The 21-day mortality rate for all patients was 37% (54 of 147); it was 52% (25 of 48) for patients with ESBL-producing K. pneumoniae bloodstream infections and 29% (29 of 99) for patients with non-ESBL-producing K. pneumoniae bloodstream infections (OR, 2.62; 95% CI, 1.28 to 5.35). In summary, this investigation identifies epidemiological characteristics that distinguish ESBL-producing K. pneumoniae infections from non-ESBL-producing K. pneumoniae ESBL bloodstream infections.

Extended antimicrobial resistance screening of the dominant faecal Escherichia coli and of rare resistant clones

Fifty faecal samples from healthy adults were grown on MacConkey agar and three pink colonies were subcultured, identified to species level and their antimicrobial susceptibility determined. Forty-seven samples yielded 141 isolates of Escherichia coli that were susceptible to most antimicrobials. Resistance was noted for ampicillin (30.5%), chloramphenicol (12.1%), tetracycline (23.4%), trimethoprim (24.8%) and co-trimoxazole (22.7%). A direct faecal plating method was used for extended resistance screening with E. coli as the indicator organism. Zone breakpoints were determined using normalised resistance interpretation and gave similar susceptibility results. Eighty-eight isolates of E. coli from within the zones of inhibition revealed four times more antimicrobial resistance. Extended antimicrobial resistance screening both provides the susceptibility profile of the dominant E. coli isolate and detects greater resistance in rare isolates.

Weichteilinfektionen in der Mund-, Kiefer- und Plastischen Gesichtschirurgie

BACKGROUND

Soft tissue infections in the maxillofacial region are mainly caused by Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli but also by members of the genera Enterococcus, Klebsiella, and Enterobacter, respectively.

METHODS

In a prospective study 96 patients with severe maxillofacial non-odontogenic postoperative soft tissue infections were analyzed with regard to the bacterial spectrum and resistance patterns against antibiotics. The dominating bacteria were Streptococci (25% of the isolates) and Staphylococci (24% of the isolates). In addition, members of Enterobacteriaceae were isolated in approximately 10% of the cases. The most frequent anaerobes found were as follows: Peptostreptococcus, Eubacterium, Prevotella and Fusobacterium.

RESULTS

The resistance rates against antibiotics found were: penicillin G 36%, ampicillin 42%, and doxycycline 36%. In addition, the resistance rate against erythromycin and clindamycin was 26% and 7%, respectively. No resistant strains were detected against vancomycin and teicoplanin. All anaerobes showed a low antimicrobial resistance as previously described for odontogenic infections.

CONCLUSION

In summary, soft tissue infections in the maxillofacial region present a different spectrum of bacteria in contrast to the well-investigated odontogenic infections. Antibiotic administration should be, whenever possible, performed after differentiation of involved strains and resistogram. The most promising antibiotics are imipenem, meropenem, and ciprofloxacin as well as cefotiam. Modern fluoroquinolones will be the antibiotics of the future.

Hospital-Level Rates of Fluoroquinolone Use and the Risk of Hospital-Acquired Infection with Ciprofloxacin-Nonsusceptible Pseudomonas aeruginosa

BACKGROUND

In recent years, Pseudomonas aeruginosa has become increasingly resistant to fluoroquinolones, and fluoroquinolone use in the United States has also increased. Our objective was to determine whether higher hospital-level rates of use of ciprofloxacin, levofloxacin, and moxifloxacin antimicrobials were predictors that a higher proportion of P. aeruginosa isolates from hospital-acquired infections (hereafter, "hospital-acquired isolates") would be nonsusceptible to ciprofloxacin.

METHODS

We identified all hospital-acquired isolates from 14 hospitals in the Northern California Kaiser Permanente health care delivery system between 1998 and 2003 and determined their susceptibility to ciprofloxacin. For each facility, we determined the number of days of fluoroquinolone use per 1000 patient-days, by calendar quarter. We used a logistic regression model to analyze the data, with susceptibility status as the outcome variable. Hospital-level rates of use of the 3 fluoroquinolones were the predictors of interest; we adjusted for year, for use of nonquinolone antimicrobials, and for patient variables, including the number of days spent in the hospital in the prior year and fluoroquinolone use in the prior year. The model tested whether isolates from those facilities with higher rates of use of antimicrobials were more likely to be nonsusceptible to ciprofloxacin.

RESULTS

Of 6099 isolates tested, 15% were not susceptible to ciprofloxacin. The nonsusceptibility rate increased from 9% to 20% between 1998 and 2003. Both the overall rate of use at the hospital and prior patient-specific use of ciprofloxacin, levofloxacin, and moxifloxacin were found to be independent predictors that a subsequent P. aeruginosa isolate would be nonsusceptible to ciprofloxacin.

CONCLUSIONS

Higher hospital-level rates of use of ciprofloxacin, levofloxacin, and moxifloxacin are each associated with an increased proportion of hospital-acquired P. aeruginosa isolates being nonsusceptible to ciprofloxacin.

Posttreatment changes in Escherichia coli antimicrobial susceptibility rates among diarrheic patients treated with ciprofloxacin

Changes in antimicrobial resistance of Escherichia coli among deployed U.S. military personnel being treated for diarrhea were evaluated. Stool samples were collected pretreatment and on days 7, 14, and 28 posttreatment. Resistance to ciprofloxacin was noted in 13.3% of baseline specimens, and rates of resistance against multiple antibiotics increased dramatically from baseline to day 7 and then tapered off to return to pretreatment levels by day 28, except for ciprofloxacin, suggesting that population accumulative usage of fluoroquinolones may result in an incremental increase in resistance rates.

Resistance to antimicrobial agents: an update

Decades of overuse and misuse of antibiotics have turned the resistance problem into a crisis. Preventive and corrective measures are urgently needed. This article presents a broad overview of the status of antimicrobial resistance. Resistance in key bacterial pathogens such as enterococci, staphylococci, pneumococci, and gram-negative bacilli; resistance to fluoroquinolones, third-generation cephalosporins, and the carbapenems; and mechanisms of resistance are discussed. The article also reviews the adverse impact of resistance on outcomes for patients with nosocomial infections. Finally, a brief overview of how the medical community can face its moment of truth is presented.

Stable Antimicrobial Susceptibility Rates for Clinical Isolates of Pseudomonas aeruginosa from the 2001–2003 Tracking Resistance in the United States Today Surveillance Studies

From 2001 to 2003, rates of susceptibility to piperacillin-tazobactam (86%), ceftazidime (80%), ciprofloxacin (68%), and levofloxacin (67%) did not decrease or decreased by <1.5%, whereas the rate of susceptibility to gentamicin decreased by 3.2% (from 75.5% to 72.3%) and the rate of susceptibility to imipenem decreased by 5.6% (from 84.4% to 78.8%), for 2394 clinical isolates of Pseudomonas aeruginosa collected in the Tracking Resistance in the United States Today surveillance studies. Rates of multidrug resistance (i.e., resistance to > or =3 antimicrobial agents) increased from 7.2% in 2001 to 9.9% in 2003 and were significantly higher for isolates from the East North Central and Mid-Atlantic regions of the United States than for isolates from other regions. Analysis of minimum inhibitory concentrations (MICs) suggested that combining an antipseudomonal beta -lactam with ciprofloxacin or levofloxacin would yield a 3.4%-7.1% increase in the percentage of isolates susceptible to the combination, compared with the beta -lactam alone. Ratios of the area under the serum concentration-time curve values for free drug to modal MICs for ciprofloxacin and levofloxacin were similar and were >125 (target ratio), whereas those ratios for gatifloxacin and moxifloxacin were significantly lower. Ongoing surveillance of P. aeruginosa is essential.

Optimizing pharmacodynamic target attainment using the MYSTIC antibiogram: data collected in North America in 2002

The OPTAMA Program is intended to examine typical antimicrobial regimens used in the treatment of common nosocomial pathogens and the likelihood of these regimens attaining appropriate pharmacodynamic exposure in different parts of the world. A 5,000-subject Monte Carlo simulation was used to estimate pharmacodynamic target attainment for meropenem, imipenem, ceftazidime, cefepime, piperacillin-tazobactam, and ciprofloxacin against Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. Standard dosing regimens from North America were used. Pharmacokinetic parameter variability was derived from existing healthy volunteer data, and MIC data came from the 2002 MYSTIC Program. Ciprofloxacin displayed the lowest target attainment against all bacterial species (41 to 46% for A. baumannii, 53 to 59% for P. aeruginosa, and 80 to 85% for the Enterobacteriaceae). Increasing the dose to 400 mg every 8 h did not significantly increase target attainment against nonfermenters. Piperacillin-tazobactam target attainments were similar to that of ceftazidime against all pathogens. Higher doses of both compounds were needed to achieve better target attainments against P. aeruginosa. Overall, meropenem, imipenem, and cefepime attained the highest probabilities of attainment against the Enterobacteriaceae (99 to 100%). The carbapenems appear to be the most useful agents against A. baumannii (88 to 92%), and these agents, along with higher doses of any of the beta-lactams, would be the most appropriate choices for empirical therapy for P. aeruginosa infection. Given the lack of agreement between percent susceptibility and probability of target attainment for certain antimicrobial regimens, a methodology employing stochastic pharmacodynamic analyses may be a more useful tool for differentiating the most-optimal compounds and dosing regimens in the clinical setting of initial empirical therapy.

Factors associated with relative rates of antibiotic resistance in Pseudomonas aeruginosa isolates tested in clinical laboratories in the United States from 1999 to 2002

For the period from 1999 to 2002 in the United States, the in vitro susceptibilities of 52,637 Pseudomonas aeruginosa isolates to 10 antimicrobial agents were evaluated. The isolates were from 29 laboratories, 11 of which participated in The Surveillance Network for four consecutive years. Isolates were collected from adult patients (> or =18 years of age) in intensive care units (ICU), non-ICU inpatients, nursing home patients, and outpatients; data were analyzed to evaluate factors, such as year of isolation, patient age group, isolate specimen source, and patient type (hospitalized patients [ICU, non-ICU, or nursing home] or outpatients). Rates of resistance for the 4-year period were highest for isolates from patients in ICU and 18- to 39-year-old patients and for isolates from the lower respiratory tract. Resistance decreased with age. Resistance was lowest in isolates from outpatients, in isolates from > or =70-year-old patients, and from specimens from the upper respiratory tract. Multidrug resistance (MDR) (resistance to three or more antimicrobial agents) accounted for 24.9% of all isolates. The MDR rate was highest in isolates from patients in nursing homes (29.9%) and ICU (29.5%).

Predicting hospital rates of fluoroquinolone-resistant Pseudomonas aeruginosa from fluoroquinolone use in US hospitals and their surrounding communities

Rates of fluoroquinolone resistance among Pseudomonas aeruginosa in hospitals are increasing, but interhospital variability is great. We sought to determine whether this variability correlated to fluoroquinolone use in hospitals and in the surrounding community. Hospital quinolone use in 1999 (24 hospitals) through 2001 (35 hospitals) was determined from billing records. The number of fluoroquinolone prescriptions within a 10-mile (approximately 16-km) radius of each hospital was determined for 1999 and 2000. Hospital fluoroquinolone use increased from 1999 through 2001, from 137 to 163 defined daily doses (DDD)/1000 patient-days (P=.01). The rate of community fluoroquinolone use also increased, from 2.3 to 2.8 DDD/1000 inhabitant-days (P<.001). Rates of fluoroquinolone-resistant P. aeruginosa increased from 29% in 1999 to 36% in 2001 (P=.003). Both community and hospital fluoroquinolone use were predictive of rates of fluoroquinolone-resistant P. aeruginosa. Levofloxacin was associated with resistance, but ciprofloxacin was not. Most of the variability in resistance rates is explained by volume of fluoroquinolone use, both in the hospital and the surrounding community.

The magnitude of the association between fluoroquinolone use and quinolone-resistant Escherichia coli and Klebsiella pneumoniae may be lower than previously reported

Case-control analyses of resistant versus susceptible isolates have implicated fluoroquinolone exposure as a strong risk factor for fluoroquinolone-resistant isolates of Enterobacteriaceae. We suspect that such methodology may overestimate this association. A total of 84 cases with fluoroquinolone-resistant isolates and 578 cases with fluoroquinolone-susceptible isolates of Escherichia coli or Klebsiella pneumoniae were compared with 608 hospitalized controls in parallel multivariable analyses. For comparison of previous estimates, the results of 10 published case-control studies of risk for fluoroquinolone resistance in isolates of Enterobacteriaceae were pooled by using a random-effects model. Exposure to fluoroquinolones was significantly positively associated with fluoroquinolone resistance (odds ratio [OR], 3.17) and negatively associated with fluoroquinolone susceptibility (OR, 0.18). Multivariable analyses yielded similar estimates (ORs, 2.04 and 0.10, respectively). As data on antibiotic exposure were limited to inpatient prescriptions, misclassification of fluoroquinolone exposure in persons who received fluoroquinolones as outpatients may have led to an underestimation of the true effect size. Pooling the results of previously published studies in which a direct comparison of fluoroquinolone-resistant and fluoroquinolone-susceptible cases was used resulted in a markedly higher effect estimate (OR, 18.7). Had we directly compared resistant and susceptible cases, our univariate OR for the association between fluoroquinolone use and the isolation of resistant Enterobacteriaceae would have been 19.3, and the multivariate OR would have been 16.5. Fluoroquinolone use is significantly associated with the isolation of fluoroquinolone-resistant Enterobacteriaceae; however, previous studies likely exaggerated the magnitude of this association.

Beta-lactamase stability of faropenem

Faropenem (FAR) is an orally available member of the penem class unique among carbapenems and other available beta-lactams. This study compared FAR to cephalosporins and imipenem with respect to beta-lactamase (BLA) stability and emergence of resistance to Staphylococcus aureus and Escherichia coli. BLA stability was studied using enzyme preparations from sonicated/centrifuged 24-hour cultures of E. coli, Enterobacter cloacae, Proteus vulgaris, Providencia rettgeri, Klebsiella pneumoniae, S. aureus, and Bacteroides fragilis grown in the presence of 20 mg/l ampicillin or cephaloridine to induce penicillinase or cephalosporinase, respectively. Substrate hydrolysis was quantitated spectrophotometrically. Multistep acquisition of resistance was promoted by growing bacteria in broth containing 2-fold dilutions of antibiotic over 10 cycles. Aliquots from test tubes with visible growth provided the inoculum for the next series of dilutions. FAR as well as other cephalosporins tested were highly stable to penicillinase derived from S. aureus and E. coli. However, E. coli- and P. vulgaris-derived cephalosporinase hydrolyzed cephaloridine, cefaclor and cefotiam considerably, whereas FAR was highly stable. FAR was highly stable against hydrolysis by various BLAs prepared from four B. fragilis strains and the rate of FAR hydrolysis by metallo-BLA was 5 times lower than that for imipenem. Additionally, the acquisition of resistant S. aureus strains was less pronounced for FAR compared to other agents tested. MICs rose 8-fold after the 10th sub-MIC exposure, while MICs rose 16-, 31- and 512-fold for cefixime, cefazolin and cefaclor, respectively. E. coli shifts in MICs were moderate for all the agents tested. In conclusion, FAR is characterized by pronounced BLA stability compared to other cephalosporins and imipenem. Furthermore, a lower propensity for resistance development with FAR as compared to cephalosporins was observed.

In vitro susceptibilities of gram-negative bacteria isolated from hospitalized patients in four European countries, Canada, and the United States in 2000-2001 to expanded-spectrum cephalosporins and comparator antimicrobials: implications for therapy

Access to current antimicrobial agent surveillance data is an important prerequisite for the optimal management of patients with hospital-acquired infections. The present study used data collected in 2000 to 2001 from 670 laboratories in Europe (France, Germany, Italy, and Spain), Canada, and the United States to report on the in vitro activities of ceftriaxone, cefotaxime, and comparative agents against >125,000 isolates of gram-negative bacteria from hospitalized patients. All but two isolates of Enterobacteriaceae (one isolate of Proteus mirabilis from France and one isolate of Morganella morganii from Canada) were susceptible to imipenem. The susceptibility of Escherichia coli to ceftriaxone or cefotaxime was > or = 97% in each country, and for P. mirabilis, susceptibility was 99% in each country except Italy. In contrast, susceptibility of E. coli to ciprofloxacin varied from 80.5% (Spain) to 94.0% (France); levofloxacin susceptibility ranged from 75.2% (Spain) to 91.6% (United States). Among Klebsiella pneumoniae and Klebsiella oxytoca isolates, ceftriaxone and cefotaxime susceptibilities ranged from 86.6 to 98.7% and 83.5 to 99.7%, respectively, depending upon the country. Considerable geographic variation in the susceptibilities (generally 85 to 95% susceptible) of Serratia marcescens and M. morganii to ceftriaxone and cefotaxime were observed. For S. marcescens, susceptibility to piperacillin-tazobactam varied from 81.5% (France) to 94.1% (Italy) and susceptibility to ciprofloxacin ranged from 66.2% (Germany) to 90.7% (Spain). Enterobacter cloacae and Enterobacter aerogenes were less susceptible to ceftriaxone and cefotaxime than were the other species of Enterobacteriaceae studied. The present study demonstrated that established parenteral expanded-spectrum cephalosporin antimicrobial agents retain significant in vitro activity against many clinically important gram-negative pathogens.

In vitro activity of gemifloxacin and contemporary oral antimicrobial agents against 27,247 Gram-positive and Gram-negative aerobic isolates: a global surveillance study

This study was a multi-centre, multi-country surveillance of 27247 Gram-positive and Gram-negative isolates collected from 131 study centres in 44 countries from 1997 to 2000. MICs of gemifloxacin were compared with penicillin, amoxicillin-clavulanic acid, cefuroxime, azithromycin, clarithromycin, trimethoprim-sulphamethoxazole, ciprofloxacin, grepafloxacin and levofloxacin by broth microdilution. Penicillin resistance in Streptococcus pneumoniae was extremely high in the Middle East (65.6%), Africa (64.0%) and Asia (60.4%) and lower in North America (40.3%), Europe (36.9%) and the South Pacific (31.8%). Macrolide resistance in S. pneumoniae was highest in Asia (51.7%) but varied widely between laboratories in Europe (26.0%), North America (21.6%), the Middle East (13.7%), the South Pacific (10.6%) and Africa (10.0%). All the study quinolones were highly active against penicillin-resistant and macrolide-resistant S. pneumoniae. Overall, gemifloxacin had the lowest MIC(90) at 0.06 mg/l with MICs 4-64-fold lower than ciprofloxacin, levofloxacin and grepafloxacin against S. pneumoniae. Gemifloxacin MICs were more potent than grepafloxacin > levoflaxacin > ciproflaxin against the Gram-positive aerobes and shared comparable Gram-negative activity with ciprofloxacin and levofloxacin.

Antimicrobial resistance among gram-negative organisms in the intensive care unit

PURPOSE OF REVIEW

We review the hospital-acquired gram-negative organisms commonly encountered among patients in the intensive care unit and discuss pertinent surveillance data, resistance mechanisms and patterns, and optimal treatment regimens for these pathogens.

RECENT FINDINGS

There has been a notable increase in antibiotic resistance among gram-negative intensive care unit pathogens. Data from surveillance programs such as National Nosocomial Infections Surveillance System, Intensive Care Antimicrobial Resistance Epidemiology, and others have documented undesirable trends in antibiotic resistance, indicating decreasing efficacy of antibiotic classes such as third-generation cephalosporins, carbapenems, and fluoroquinolones, The increased prevalence of extended-spectrum beta-lactamases has contributed to the finding of multidrug resistance among bacteria such as Klebsiella and Escherichia coli. Furthermore, organisms such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia display intrinsic resistance to many antibiotics, making selection of optimal therapy difficult. Studies have correlated infection by these organisms with prior antibiotic exposure, and containment of the spread of infection can be achieved by careful antibiotic use and infection control practices.

SUMMARY

Antibiotic resistance continues to rise among hospital-acquired gram-negative pathogens. Optimal management of these infections requires knowledge of local epidemiology and practices to control their spread.

Antimicrobial susceptibility and synergy studies of Stenotrophomonas maltophilia isolates from patients with cystic fibrosis

Stenotrophomonas maltophilia is a newly emerging pathogen being detected with increasing frequency in patients with cystic fibrosis (CF). The impact of this multidrug-resistant organism on lung function is uncertain. The optimal treatment for S. maltophilia in CF patients is unknown. We studied the in vitro activity of ten antimicrobial agents, and conducted synergy studies by using checkerboard dilutions of eight pairs of antimicrobial agents against strains isolated from 673 CF patients from 1996 to 2001. This represents approximately 7 to 23% of the CF patients in the United States who harbor S. maltophilia annually. Doxycycline was the most active agent and inhibited 80% of 673 initial patient isolates, while trimethoprim-sulfamethoxazole inhibited only 16%. High concentrations of colistin proved more active than high concentrations of tobramycin and gentamicin. Serial isolates (n = 151) from individual patients over time (median, 290 days) showed minimal changes in resistance. Synergistic or additive activity was demonstrated by trimethoprim-sulfamethoxazole paired with ticarcillin-clavulanate (65% of strains), ciprofloxacin paired with ticarcillin-clavulanate (64% of strains), ciprofloxacin paired with piperacillin-tazobactam (59% of strains), trimethoprim-sulfamethoxazole paired with piperacillin-tazobactam (55% of strains), and doxycycline paired with ticarcillin-clavulanate (49% of strains). In all, 522 (78%) isolates were multidrug resistant (i.e., resistant to all agents in two or more antimicrobial classes) but 473 (91%) of these were inhibited by at least one antimicrobial combination (median, four; range, one to eight). To determine appropriate treatment for patients with CF, it is important to monitor the prevalence, antimicrobial susceptibility, and clinical impact of S. maltophilia in this patient population.

Current and future perspectives for levofloxacin in severe Pseudomonas aeruginosa infections

The question of whether levofloxacin includes Pseudomonas aeruginosa in its spectrum of clinical activity is discussed by reviewing the major findings on this issue, mainly those published in Italy. The in vitro activity of levofloxacin against P. aeruginosa is now documented on thousands of strains worldwide. The pharmacodynamic properties of levofloxacin allow for the treatment of pseudomonal infections. The levofloxacin clinical results extrapolated from published studies document the efficacy of levofloxacin in the treatment of infections sustained by P. aeruginosa.

Trends in antimicrobial susceptibilities among Enterobacteriaceae isolated from hospitalized patients in the United States from 1998 to 2001

Longitudinal surveillance of Enterobacteriaceae for antimicrobial susceptibility is important because species of this family are among the most significant and prevalent human pathogens. To estimate rates of in vitro antimicrobial susceptibility among hospitalized patients in the United States, data from The Surveillance Network were studied for 14 agents tested against 10 species of Enterobacteriaceae (n = 384,279) isolated from intensive-care-unit (ICU) patients and non-ICU inpatients from 1998 to 2001. Cumulative susceptibility (percent) data for all species of Enterobacteriaceae isolated from ICU patients and non-ICU inpatients, respectively, were ranked as follows: ampicillin-sulbactam (45.5 and 57.2) << ticarcillin-clavulanate (74.8 and 83.5) < trimethoprim-sulfamethoxazole (87.0 and 84.5) congruent with cefotaxime (82.9 and 92.6) = ceftazidime (82.3 and 91.0) = ceftriaxone (86.5 and 93.9) = piperacillin-tazobactam (83.5 and 90.5) < levofloxacin (89.3 and 90.6) = ciprofloxacin (91.0 and 91.7) < gentamicin (91.8 and 94.3) < cefepime (95.0 and 97.9) < amikacin (98.5 and 99.2) < imipenem (100 and 100) = meropenem (100 and 100). Of those agents studied only susceptibilities to ciprofloxacin (94 to 89%) and levofloxacin (93 to 89%) decreased in a stepwise manner from 1998 to 2001. Decreased fluoroquinolone susceptibility was most pronounced for Escherichia coli, Proteus mirabilis, and Enterobacter cloacae. For all species of Enterobacteriaceae, trimethoprim-sulfamethoxazole resistance was more commonly observed in isolates with a single-drug resistance phenotype while gentamicin and fluoroquinolone resistances were more common in isolates resistant to at least one additional class of antimicrobial agent. Ongoing surveillance of Enterobacteriaceae will be particularly important to monitor changes in fluoroquinolone susceptibility, as well as changes in the prevalence of isolates resistant to multiple classes of antimicrobial agents.

Surveillance for antimicrobial susceptibility among clinical isolates of Pseudomonas aeruginosa and Acinetobacter baumannii from hospitalized patients in the United States, 1998 to 2001

Pseudomonas aeruginosa and Acinetobacter baumannii are the most prevalent nonfermentative bacterial species isolated from clinical specimens of hospitalized patients. A surveillance study of 65 laboratories in the United States from 1998 to 2001 found >90% of isolates of P. aeruginosa from hospitalized patients to be susceptible to amikacin and piperacillin-tazobactam; 80 to 90% of isolates to be susceptible to cefepime, ceftazidime, imipenem, and meropenem; and 70 to 80% of isolates to be susceptible to ciprofloxacin, gentamicin, levofloxacin, and ticarcillin-clavulanate. From 1998 to 2001, decreases in antimicrobial susceptibility (percents) among non-intensive-care-unit (non-ICU) inpatients and ICU patients, respectively, were greatest for ciprofloxacin (6.1 and 6.5), levofloxacin (6.6 and 3.5), and ceftazidime (4.8 and 3.3). Combined 1998 to 2001 results for A. baumannii isolated from non-ICU inpatients and ICU patients, respectively, demonstrated that >90% of isolates tested were susceptible to imipenem (96.5 and 96.6%) and meropenem (91.6 and 91.7%); fewer isolates from both non-ICU inpatients and ICU patients were susceptible to amikacin and ticarcillin-clavulanate (70 to 80% susceptible); and <60% of isolates were susceptible to ceftazidime, ciprofloxacin, gentamicin, or levofloxacin. From 1998 to 2001, rates of multidrug resistance (resistance to at least three of the drugs ceftazidime, ciprofloxacin, gentamicin, and imipenem) showed small increases among P. aeruginosa strains isolated from non-ICU inpatients (5.5 to 7.0%) and ICU patients (7.4 to 9.1%). From 1998 to 2001, rates of multidrug resistance among A. baumannii strains isolated from non-ICU inpatients (27.6 to 32.5%) and ICU patients (11.6 to 24.2%) were higher and more variable than those observed for P. aeruginosa. Isolates concurrently susceptible, intermediate, or resistant to both imipenem and meropenem accounted for 89.8 and 91.2% of P. aeruginosa and A. baumannii isolates, respectively, studied from 1998 to 2001. In conclusion, for aminoglycosides and most beta-lactams susceptibility rates for P. aeruginosa and A. baumannii were constant or decreased only marginally (</=3%) from 1998 to 2001. Greater decreases in susceptibility rates were, however, observed for fluoroquinolones and ceftazidime among P. aeruginosa isolates.

Susceptibility patterns of orally administered antimicrobials among urinary tract infection pathogens from hospitalized patients in North America: comparison report to Europe and Latin America. Results from the SENTRY Antimicrobial Surveillance Program (2000)

Urinary tract infections (UTIs) remain a worldwide nosocomial infection problem. Geographic variations in pathogen occurrence and susceptibility profiles require monitoring to provide information to guide new (garenoxacin [BMS284756]) therapeutic options. Two thousand seven hundred-eighty UTI isolates from Europe (n = 783), Latin America (531), and North America (1,466) were tested and compared against 44 agents by reference methods in the SENTRY Antimicrobial Surveillance Program. The top seven pathogens accounted for 90% of all isolates and the rank order for all regions was: Escherichia coli (1,316; 47%), Enterococcus spp. (351; 13%), Klebsiella spp. (306; 11%), Pseudomonas aeruginosa (210; 8%), Proteus mirabilis (145; 5%), Enterobacter spp. (97; 4%), and Citrobacter spp. (78; 3%). The pathogen rank order was similar among regions except for the rarer occurrence of Enterococcus spp. (Rank #6, 4%) in Latin America. E. coli ampicillin resistance was highest in Europe and Latin America (51-55%). Ampicillin (37%), ciprofloxacin or garenoxacin (4%), and trimethoprim/sulfamethoxazole (23%) resistance remained lowest in North America. Nitrofurantoin susceptibility in E. coli was still at acceptable levels and ranged from 91 to 96% across regions. The regional ciprofloxacin-resistant rank order for P. aeruginosa by region was: Latin America (55%) > Europe (41%) > North America (29%). Vancomycin-resistant enterococci (VRE) were only detected in North America (7%). Garenoxacin possessed a 34 to 44% wider spectrum compared to ciprofloxacin against enterococci UTI isolates. Extended spectrum beta-lactamase rates for E. coli and Klebsiella spp. were 4 and 19%, respectively. These results emphasized the need to assess the often striking differences in pathogen occurrence and resistance rates among the commonly encountered UTI pathogens.

Levofloxacin and ciprofloxacin in vitro activities against 4,003 clinical bacterial isolates collected in 24 Italian laboratories

Levofloxacin showed comparable in vitro susceptibility to ciprofloxacin among Enterobacteriaceae, Pseudomonas aeruginosa, enterococci, and Staphylococcus aureus, while greater susceptibility was observed in Stenotrophomonas maltophilia and Staphylococcus epidermidis, mainly when oxacillin resistant. The susceptibility of Streptococcus pneumoniae to levofloxacin reached 99%.

A new method for normalized interpretation of antimicrobial resistance from disk test results for comparative purposes

OBJECTIVE

To evaluate a calibration method for disk diffusion antibiotic susceptibility tests, using zone diameter values generated in the individual laboratory as the internal calibrator for combinations of antibiotic and bacterial species.

METHODS

The high-zone side of zone histogram distributions was first analyzed by moving averages to determine the peak position of the susceptible population. The accumulated percentages of isolates for the high zone diameter values were calculated and converted into probit values. The normal distribution of the ideal population of susceptible strains was then determined by using the least-squares method for probit values against zone diameters, and the ideal population was thereby defined, including mean and standard deviation. Zone diameter values were obtained from laboratories at the Karolinska Hospital (KS) and Växjö Hospital (VX), and from two laboratories (LabA, LabB) in Argentina. The method relies on well standardized disk tests, but is independent of differences in MIC limits and zone breakpoints, and does not require the use of reference strains. Resistance was tentatively set at below 3 SD from the calculated, ideal mean zone diameter of the susceptible population.

RESULTS

The method, called normalized interpretation of antimicrobial resistance, was tested on results from the KS and VX clinical microbiology laboratories, using the disk diffusion method for antimicrobial susceptibility tests, and for two bacterial species, Staphylococcus aureus and Escherichia coli. In total, 114 217 test results were included for the clinical isolates, and 3582 test results for control strains. The methodology at KS and VX followed the standard of the Swedish Reference Group for Antibiotics (SRGA). Zone diameter histograms for control strains were first analyzed to validate the procedure, and a comparison of actual means with the calculated means showed a correlation coefficient of r = 0.998. Results for clinical isolates at the two laboratories showed an excellent agreement for 54 of 57 combinations of antibiotic and bacterial species between normalized interpretations and the interpretations given by the laboratories. There were difficulties with E. coli and mecillinam, and S. aureus and tetracycline and rifampicin. The method was also tested on results from two laboratories using the NCCLS standard, and preliminary results showed very good agreement with quality-controlled laboratory interpretations.

CONCLUSIONS

The normalized resistance interpretation offers a new approach to comparative surveillance studies whereby the inhibition zone diameter results from disk tests in clinical laboratories can be used for calibration of the test.

Trends in antimicrobial resistance among urinary tract infection isolates of Escherichia coli from female outpatients in the United States

The Infectious Diseases Society of America advocates trimethoprim-sulfamethoxazole (SXT) as initial therapy for females with acute uncomplicated bacterial cystitis in settings where the prevalence of SXT resistance does not exceed 10 to 20%. To determine trends in the activities of SXT, ampicillin, ciprofloxacin, and nitrofurantoin among urine isolates of Escherichia coli from female outpatients, susceptibility testing data from The Surveillance Network (TSN) Database-USA (n = 286,187) from 1995 to 2001 were analyzed. Resistance rates among E. coli isolates to ampicillin (range, 36.0 to 37.4% per year), SXT (range, 14.8 to 17.0%), ciprofloxacin (range, 0.7 to 2.5%), and nitrofurantoin (range, 0.4 to 0.8%) varied only slightly over this 7-year period. Ciprofloxacin was the only agent studied that demonstrated a consistent stepwise increase in resistance from 1995 (0.7%) to 2001 (2.5%). In 2001, SXT resistance among E. coli isolates was >10% in all nine U.S. Bureau of the Census regions. At institutions testing > or =100 urinary isolates of E. coli (n = 126) in 2001, ampicillin (range, 27.3 to 98.8%) and SXT (range, 7.5 to 47.1%) resistance rates varied widely while ciprofloxacin (range, 0 to 12.9%) and nitrofurantoin (range, 0 to 2.8%) resistance rates were more consistent. In 2001, the most frequent coresistant phenotypes were resistance to ampicillin and SXT (12.0% of all isolates; 82.3% of coresistant isolates) and resistance to ampicillin, ciprofloxacin, and SXT (1.4% of all isolates; 9.9% of coresistant isolates). Coresistance less frequently included resistance to nitrofurantoin (3.5% of coresistant isolates) than resistance to ciprofloxacin (15.8%), SXT (95.7%), and ampicillin (98.1%). In conclusion, among urinary isolates of E. coli from female outpatients in the United States, national resistance rates to SXT were relatively consistent (14.8 to 17.0%) from 1995 to 2001 but demonstrated considerable regional and institutional variation in 2001. Therapies other than SXT may need to be considered in some locations.

Comparative antimicrobial spectrum and activity of the desfluoroquinolone BMS284756 (T-3811) tested against non-fermentative Gram-negative bacilli

OBJECTIVE

To compare the in vitro activity of BMS284756, a desfluoroquinolone, with four fluoroquinolones against 129 Pseudomonas aeruginosa strains, 97 Stenotrophomonas/Burkholderia group strains and 43 Acinetobacter spp. strains by three in vitro test methods.

METHODS

The activity of BMS284756 was determined using the NCCLS reference broth microdilution method and E test (AB Biodisk, Solna, Sweden). These methods were compared for test accuracy, and 5-microg disk zone diameters were compared for interpretative accuracy using the susceptible breakpoint of < or =4 mg/L recommended by the manufacturer. All strains tested were derived from the 1999-2000 SENTRY Antimicrobial Surveillance Program organism collection.

RESULTS

Comparative quinolone potency against P. aeruginosa was as follows: ciprofloxacin (MIC50, 0.25 mg/L) > gemifloxacin (MIC50, 0.5 mg/L) > levofloxacin = gatifloxacin (MIC50, 1 mg/L) > BMS284756 (MIC50, 4 mg/L). The MIC50 value for BMS284756 versus Stenotrophomonas/Burkholderia group was 2 mg/L. This potency was similar to that of other quinolones reported previously. The MIC50 results for the Acinetobacter spp. were ciprofloxacin at >2 mg/L, levofloxacin, gatifloxacin and gemifloxacin at 4 mg/L, and BMS284756 at >4 mg/L, all intermediate or resistant concentrations. The E test results compared favorably with the reference dilution test results for P. aeruginosa, Stenotrophomonas/Burkholderia group, and Acinetobacter spp., with an overall essential agreement of 97.0% +/- 2 log2 dilution steps. E test MIC results tended to be slightly lower when testing Stenotrophomonas/Burkholderia group strains. The disk diffusion method correlated well for P. aeruginosa (r = 0.94), Stenotrophomonas/Burkholderia group (r = 0.84) and Acinetobacter spp. (r = 0.99) strains.

CONCLUSIONS

BMS284756 was generally less active than other comparison quinolones when tested against non-fermentative Gram-negative bacilli. Its spectrum remains equivalent only if dosing schedules substantiate a proposed susceptible breakpoint of < or =4 mg/L.

Ceftriaxone activity against Gram-positive and Gram-negative pathogens isolated in US clinical microbiology laboratories from 1996 to 2000: results from The Surveillance Network (TSN) Database-USA

Ceftriaxone was introduced into clinical practice in the USA in 1985 and was the first extended-spectrum (third-generation) cephalosporin approved for once-daily treatment of patients with Gram-positive or Gram-negative infections. Review of ceftriaxone activity is important given its continued use since the mid-1980s and reports of emerging resistance among all antimicrobial agent classes. We reviewed the activity of ceftriaxone and relevant comparative agents against five Gram-positive and 11 Gram-negative species for a 5-year period, 1996-2000, using data from The Surveillance Network (TSN) Database-USA. All MIC results were interpreted using NCCLS breakpoint criteria. Ceftriaxone resistance among isolates of Streptococcus pneumoniae (n=17219) remained essentially unchanged over the 5 years studied and in fact was lower from 1998 to 2000 (5.0-5.1%) than in 1996 (6.3%) and 1997 (6.6%). Ceftriaxone resistance (range, 5.1-6.9%) among viridans group streptococci (n=6621) varied by <2% from 1997 to 2000. Beta-lactam-resistant Streptococcus pyogenes (n=935) and group B beta-haemolytic streptococci (n=2267) were not identified in any year. Among methicillin-susceptible Staphylococcus aureus (n=39 284) ceftriaxone resistance was 0.1-0.3% per year from 1996 to 2000. Ceftriaxone resistance among Escherichia coli (n=472407; range, 0.2-0.4%), Klebsiella oxytoca (n=16231; range, 3.5-4.8%), Klebsiella pneumoniae (n=117754; range, 1.9-2.6%), Proteus mirabilis (n=67692; range, 0.2-0.3%), Morganella morganii (n=11251; range, 0.3-2.1%) and Serratia marcescens (n=26519; range, 1.6-3.8%) was low and consistent from 1996 to 2000. Resistance to ceftriaxone among Enterobacter cloacae (n=48114; range, 21.7-23.9%) was relatively high, compared with other Enterobacteriaceae, but unchanged from 1996 to 2000. Rates of resistance to ceftriaxone among Acinetobacter spp. (n=20813) increased from 24.8% in 1996 to 45.1% in 2000. All Haemophilus influenzae (n=7911) and Neisseria gonorrhoeae (n=218) were susceptible to ceftriaxone, as were 99.7% of Moraxella catarrhalis (n=312) tested in 1996 and 1997. In summary, ceftriaxone has retained its potent activity against the most commonly encountered Gram-positive and Gram-negative human pathogens despite widespread and ongoing clinical use for more than 15 years.

Susceptibility to fluoroquinolones among commonly isolated Gram-negative bacilli in 2000: TRUST and TSN data for the United States. Tracking Resistance in the United States Today. The Surveillance Network

From January to May 2000, as part of the Tracking Resistance in the United States Today (TRUST) surveillance initiative, clinical isolates of Enterobacteriaceae (n=2519) and non-fermentative Gram-negatives (n=580) were prospectively collected from 26 hospital laboratories across the United States. Isolates were tested for susceptibility to three fluoroquinolones (ciprofloxacin, levofloxacin, gatifloxacin) and seven other agents. In addition, data for the same period were collected from The Surveillance Network (TSN) Database-USA, an electronic surveillance network that receives data from more than 200 laboratories in the US. Both surveillance methods produced similar results. Against isolates of Enterobacteriaceae, imipenem was the most active agent, followed by the fluoroquinolones; > or = 86.7% of isolates of all species of Enterobacteriaceae except Providencia spp. were susceptible to fluoroquinolones by TRUST and TSN surveillance. TRUST identified differences in susceptibility to the three fluoroquinolones of > or = 2% for Citrobacter spp., Enterobacter cloacae, Proteus mirabilis and Serratia marcescens. Isolates of P. mirabilis were considerably more susceptible to levofloxacin (94.0%) than to ciprofloxacin (87.7%) and gatifloxacin (87.7%). Other results from TRUST included Pseudomonas aeruginosa being slightly more susceptible to ciprofloxacin (73.5%) and levofloxacin (73.0%) than gatifloxacin (71.0%). Imipenem was the only compound with significant activity (95.1% susceptible, TRUST; 87.4% susceptible, TSN) against Acinetobacter baumannii, but it was inactive against Stenotrophomonas maltophilia. S. maltophilia isolates were more susceptible to levofloxacin and gatifloxacin (77.7-79.8%) than ciprofloxacin (29.7-33.0%). Against 513 urinary isolates of Escherichia coli in TRUST, levofloxacin, gatifloxacin and ciprofloxacin were equipotent. Age and gender had no clear effect on the activity of levofloxacin, ciprofloxacin or gatifloxacin. Similar results for all three fluoroquinolones were seen in outpatients and inpatients. TRUST and TSN data indicated that resistance rates had not changed appreciably for any compound studied since a similar study conducted in 1999. TRUST centralized in vitro and electronic (TSN) surveillance methods provided an effective strategy for monitoring trends in resistance.

Spectrum and activity of three contemporary fluoroquinolones tested against Pseudomonas aeruginosa isolates from urinary tract infections in the SENTRY Antimicrobial Surveillance Program (Europe and the Americas; 2000): more alike than different!

The spectrum and potency of ciprofloxacin, gatifloxacin and levofloxacin was compared to that of 10 other agents against urinary tract isolates of Pseudomonas aeruginosa among patients in the year 2000 SENTRY Antimicrobial Surveillance Program (Europe, Latin America, North America). Dramatic differences were observed between isolates in geographic areas with the most fluoroquinolone-resistant strains detected in Latin America (54.5% resistance) compared to resistance rates of 40.8-43.7% and 28.3-29.2% for Europe and North America, respectively. Overall, no significant differences were observed between the spectrums of these fluoroquinolones (37.1-38.8% resistance) for therapy of P. aeruginosa urinary tract infections in hospitalized patients. Generally, in this world wide sample, aminoglycosides, carbapenems (imipenem, meropenem), cefepime, and piperacillin with or without tazobactam possessed a wider range of activity and spectrum versus current P. aeruginosa clinical isolates.