James S. Lewis

Pharmacology of Systemic Antifungal Agents

Traditionally, many invasive fungal infections were associated with a poor prognosis, because effective therapeutic options were limited. The recent development of new antifungal agents has significantly contributed to the successful treatment of fungal diseases. These drugs offer novel mechanisms of action and expanded spectrums of activity over traditional treatment options. However, with these new agents comes the need for increased awareness of the potential interactions and toxicities associated with these drugs. Therefore, an understanding of the pharmacokinetic and pharmacodynamic properties of the classes of antifungal compounds is vital for the effective management of invasive fungal infections. This review provides a summary of the pharmacologic principles involved in treatment of fungal diseases. The number of agents available to treat invasive fungal infections has increased by 30% since the turn of the millennium. Although that statistic is impressive, it brings the total number of approved systemic antifungal drugs to only 14 [1], with the potential for 1 more product to possibly emerge this year. These recent additions have provided clinicians with a tool previously lacking in the management of these life-threatening infections: therapeutic alternatives. Along with new options, however, comes the need to understand the uniqueness of each agent, including its role in therapy, toxicity profile, and interactions with concomitant medications. To attain the maximum effect from these agents, clinicians should also become familiar with strategies to optimize efficacy through an understanding of pharmacokinetic and pharmacodynamic properties. These characteristics are unique for each class of antifungal drug and even for each member within a class. In many cases, this variability is not subtle and merits careful attention.

First Report of the Emergence of CTX-M-Type Extended-Spectrum β-Lactamases (ESBLs) as the Predominant ESBL Isolated in a U.S. Health Care System

ABSTRACT CTX-M-type extended-spectrum β-lactamases (ESBLs) have become increasingly common worldwide, with the notable exception of the United States, where TEM- and SHV-type ESBLs have appeared to predominate. We have noted the emergence of ESBLs in our health care system (the University Health System in San Antonio, TX), especially in Escherichia coli isolates, that preferentially hydrolyze cefotaxime rather than ceftazidime, suggesting the possibility of CTX-M-type enzymes. Microbiology laboratory records were reviewed to identify ESBL-producing isolates and to compare the diameters of ceftazidime disk diffusion zones of inhibition to cefotaxime zone diameters. All isolates had been initially detected and confirmed using the procedures recommended by the Clinical and Laboratory Standards Institute. A total of 94 stored ESBL-producing isolates recovered between January 2000 and June 2006 (predominately from blood and normally sterile fluids) were retrieved for further study and screened using PCR primers specific for the presence of CTX-M, TEM, and SHV ESBLs. Only small numbers of retained ESBL-producing isolates were available for study in 2000 and 2002. The percentages of available ESBL-producing organisms in the following years were found to produce CTX-M enzymes: 2000, 25%; 2001, 10%; 2002, 0%; 2003, 60%; 2004, 69%; 2005, 89%; and 2006, 70%. The most common CTX-M-type ESBL was CTX-M-15, followed by CTX-M-16, CTX-M-8, and CTX-M-14. Comparing the disk diffusion zone diameters of cefotaxime and ceftazidime was helpful with the initial recognition of CTX-M-producing E. coli, which had an average cefotaxime zone diameter 7 mm smaller than the ceftazidime zone. However, comparing ceftazidime and cefotaxime zones for CTX-M-producing Klebsiella spp. was not helpful with initial recognition. CTX-M enzymes were also identified in Proteus mirabilis, Enterobacter spp., and Morganella morganii. Based on pulsed-field gel electrophoresis typing of the E. coli isolates, the CTX-M-producing isolates did not represent the spread of a single clone in the institution or in the community. In conclusion, CTX-M-type ESBLs are now the most common ESBL type isolated from patients in our health care system and may also be present but unrecognized in other U.S. locales.

Community-Associated Extended-Spectrum β-Lactamase–Producing Escherichia coli Infection in the United States

Background. The occurrence of community-associated infections due to extended-spectrum β-lactamase (ESBL)-producing Escherichia coli has been recognized as a major clinical problem in Europe and other regions. Methods. We conducted a prospective observational study to examine the occurrence of community-associated infections due to ESBL-producing E. coli at centers in the United States. Five academic and community hospitals and their affiliated clinics participated in this study in 2009 and 2010. Sites of acquisition of the organisms (community-associated or healthcare-associated), risk factors, and clinical outcome were investigated. Screening for the global epidemic sequence type (ST) 131 and determination of the ESBL types was conducted by polymerase chain reaction and sequencing. Results. Of the 291 patients infected or colonized with ESBL-producing E. coli as outpatients or within 48 hours of hospitalization, 107 (36.8%) had community-associated infection (81.5% of which represented urinary tract infection), while the remainder had healthcare-associated infection. Independent risk factors for healthcare-associated infection over community-associated infection were the presence of cardiovascular disease, chronic renal failure, dementia, solid organ malignancy, and hospitalization within the previous 12 months. Of the community-associated infections, 54.2% were caused by the globally epidemic ST131 strain, and 91.3% of the isolates produced CTX-M-type ESBL. Conclusions. A substantial portion of community-onset, ESBL-producing E. coli infections now occur among patients without discernible healthcare-associated risk factors in the United States. This epidemiologic shift has implications for the empiric management of community-associated infection when involvement of E. coli is suspected.

Emergence of Daptomycin Resistance in Enterococcus faecium during Daptomycin Therapy

Daptomycin is a cyclic lipopeptide antibiotic that has been available in the United States since September 2003. We report a clinical and bacteriological failure of daptomycin therapy for enterococcal bacteremia. Briefly, a 22-year-old man with Hodgkins lymphoma, subsequent acute myelogenous

Development of Caspofungin Resistance following Prolonged Therapy for Invasive Candidiasis Secondary to Candida glabrata Infection

ABSTRACT We report a case of Candida glabrata invasive candidiasis that developed reduced susceptibility to caspofungin during prolonged therapy. Pre- and posttreatment isolates were confirmed to be isogenic, and sequencing of hot spots known to confer echinocandin resistance revealed an F659V substitution within the FKS2 region of the glucan synthase complex.

Refractory coccidioidomycosis treated with posaconazole

BACKGROUND Disseminated coccidioidomycosis (which is caused by the endemic fungi of the genus Coccidioides) can be a life-threatening systemic fungal infection. Although conventional antifungal therapies have activity against Coccidioides, the disease can be refractory to standard therapies. Drug-associated toxicities also may limit the clinical utility of the standard antifungal drugs. In addition, relapses in patients with disseminated coccidioidomycosis are common, making long-term management of this disease challenging. METHODS We report the outcomes of 6 patients with coccidioidomycosis who were treated with posaconazole salvage therapy after treatment with conventional antifungal therapies failed to produce sustained clinical improvement. Patients were administered posaconazole oral suspension 800 mg/day in divided doses as part of an open-label clinical trial. A modified version of the Mycoses Study Group Coccidioides scoring system was used to evaluate the burden of disease. Posaconazole therapy resulted in rapid clinical improvements in the signs and symptoms of coccidioidomycosis. RESULTS At the end of therapy, 5 of 6 patients had successful outcomes. Posaconazole was well tolerated despite long-term administration (1-2 years), and 2 patients continued to receive posaconazole maintenance therapy at the time of writing. CONCLUSIONS The successful outcomes observed in this case series suggest that posaconazole is an effective therapy for coccidioidomycosis.

Vancomycin MICs for Methicillin-Resistant Staphylococcus aureus Isolates Differ Based upon the Susceptibility Test Method Used

Recent studies have questioned treatment of serious methicillin-resistant Staphylococcus aureus (MRSA) infections with vancomycin because of treatment failures, despite vancomycin MICs in the susceptible category (MIC ≤ 2 μg/ml) ([2][1], [3][2], [5][3], [6][4], [7][5]). Some of these studies have

Extended-spectrum β-lactamases: Epidemiology, detection, and treatment

Extended‐spectrum β‐lactamases (ESBLs) are extremely broad spectrum β‐lactamase enzymes found in a variety of Enterobacteriaceae. Most strains producing these β‐lactamases are Klebsiella pneumoniae, other Klebsiella species (i.e., K. oxytoca), and Escherichia coli. When producing these enzymes, organisms become highly effective at inactivating various β‐lactam antibiotics. In addition, ESBL‐producing bacteria are frequently resistant to many classes of antibiotics, resulting in difficult‐to‐treat infections. Other problems due to ESBL‐producing bacteria are difficulty in detecting the presence of ESBLs, limited treatment options, and deleterious impact on clinical outcomes. Clinicians should be familiar with the clinical significance of these enzymes and potential strategies for dealing with this growing problem.

Molecular epidemiological analysis of Escherichia coli sequence type ST131 (O25:H4) and bla CTX-M-15among extended-spectrum-β- lactamase-producing E. coli from the United States, 2000 to 2009

ABSTRACT Escherichia coli sequence type ST131 (from phylogenetic group B2), often carrying the extended-spectrum-β-lactamase (ESBL) gene blaCTX-M-15, is an emerging globally disseminated pathogen that has received comparatively little attention in the United States. Accordingly, a convenience sample of 351 ESBL-producing E. coli isolates from 15 U.S. centers (collected in 2000 to 2009) underwent PCR-based phylotyping and detection of ST131 and blaCTX-M-15. A total of 200 isolates, comprising 4 groups of 50 isolates each that were (i) blaCTX-M-15 negative non-ST131, (ii) blaCTX-M-15 positive non-ST131, (iii) blaCTX-M-15 negative ST131, or (iv) blaCTX-M-15 positive ST131, also underwent virulence genotyping, antimicrobial susceptibility testing, and pulsed-field gel electrophoresis (PFGE). Overall, 201 (57%) isolates exhibited blaCTX-M-15, whereas 165 (47%) were ST131. ST131 accounted for 56% of blaCTX-M-15-positive- versus 35% of blaCTX-M-15-negative isolates (P < 0.001). Whereas ST131 accounted for 94% of the 175 total group B2 isolates, non-ST131 isolates were phylogenetically distributed by blaCTX-M-15 status, with groups A (blaCTX-M-15-positive isolates) and D (blaCTX-M-15-negative isolates) predominating. Both blaCTX-M-15 and ST131 occurred at all participating centers, were recovered from children and adults, increased significantly in prevalence post-2003, and were associated with molecularly inferred virulence. Compared with non-ST131 isolates, ST131 isolates had higher virulence scores, distinctive virulence profiles, and more-homogeneous PFGE profiles. blaCTX-M-15 was associated with extensive antimicrobial resistance and ST131 with fluoroquinolone resistance. Thus, E. coli ST131 and blaCTX-M-15 are emergent, widely distributed, and predominant among ESBL-positive E. coli strains in the United States, among children and adults alike. Enhanced virulence and antimicrobial resistance have likely promoted the epidemiological success of these emerging public health threats.

Methicillin-resistant Staphylococcus aureus bacteraemia and endocarditis treated with ceftaroline salvage therapy

BACKGROUND One of the newest methicillin-resistant Staphylococcus aureus (MRSA) antibiotics to receive FDA approval is ceftaroline fosamil, a member of a new subclass of cephalosporins with unique activity against MRSA. However, ceftaroline is currently only FDA approved for complicated skin/soft tissue infections and community-acquired pneumonia; there are currently no clinical data regarding its use in MRSA bacteraemia and endocarditis. We report a series of six patients in which ceftaroline was utilized as salvage monotherapy in persistent MRSA bacteraemia or endocarditis. METHODS Using pharmacy records, 11 ceftaroline-treated patients were identified between January 2011 and November 2011 at University Health System and the South Texas Veterans Health Care System in San Antonio, TX, USA. All cases were reviewed and six patients received ceftaroline therapy for MRSA bacteraemia or endocarditis due to persistent or recurrent bacteraemia while on standard antibiotics (vancomycin or daptomycin). RESULTS All six patients experienced rapid clearance of their bacteraemia after starting ceftaroline. In the case of endocarditis for which the patient subsequently developed heart failure and required valve replacement, there was no evidence of growth from cultures taken from the excised valve, suggesting sterilization within 13 days of starting ceftaroline. CONCLUSIONS Ceftaroline exhibits potent anti-MRSA activity in both in vitro and animal studies, including rabbit endocarditis models; however, the lack of clinical data has limited its use in bacteraemia and endovascular infections in humans. We hope that this series serves as an initial stepping stone for further evaluation of this compound for more invasive infections due to MRSA.