Colistin is increasingly used as an antibiotic of last resort for the treatment of carbapenem-resistant Gram-negative infections. The plasmid-borne colistin resistance gene mcr-1 was initially identified in animal and clinical samples from China and subsequently reported worldwide, including in the United States. Of particular concern is the spread of mcr-1 into carbapenem-resistant bacteria, thereby creating strains that approach pan-resistance. While several reports of mcr-1 have involved carbapenem-resistant strains, no such isolates have been described in the United States. Here, we report the isolation and identification of an Escherichia coli strain harboring both mcr-1 and carbapenemase gene blaNDM-5 from a urine sample in a patient without recent travel outside the United States. The isolate exhibited resistance to both colistin and carbapenems, but was susceptible to amikacin, aztreonam, gentamicin, nitrofurantoin, tigecycline, and trimethoprim-sulfamethoxazole. The mcr-1- and blaNDM-5-harboring plasmids were completely sequenced and shown to be highly similar to plasmids previously reported from China. The strain in this report was first isolated in August 2014, highlighting an earlier presence of mcr-1 within the United States than previously recognized.
The susceptibility of Borrelia burgdorferi, the causative agent of Lyme borreliosis, to various antimicrobial agents varies widely among published studies. These differences are probably due in part to variations in susceptibility testing techniques and growth endpoint determinations. We developed a microdilution method for determining the MICs of antibiotics against B. burgdorfen. The method incorporated BSK II medium, a final inoculum of 106 cells per ml, and a 72-h incubation period and was found to be simple and highly reproducible. A variety of antibiotics and strains of B. burgdorferi and one strain of Borrelia hermsii were examined by this method. MICs of penicillin, ceftriaxone, and erythromycin for the B31 strain ofB. burgdorferi were 0.06, 0.03, and 0.03 ,ug/ml, respectively. We compared the MICs obtained by the microdilution method with those obtained by a macrodilution method using similar criteria for endpoint determinations and found the values obtained by both methods to be in close agreement. To further investigate the bactericidal activities of penicillin, ceftriaxone, and erythromycin against strain B31, we used subsurface plating to determine MBCs and we also performed time-kill studies. The MBCs of penicillin, ceftriaxone, and erythromycin were 0.125, 0.03, and 0.06 igIml, respectively. Time-kill curves demonstrated a .3-log1o-unit killing after 72 h with penicillin, ceftriaxone, and erythromycin; ceftriaxone provided the greatest reduction in CFU. The described methods offer a more standardized and objective approach to susceptibility testing of B. burgdorferi. The spectrum of antibiotic susceptibility of Borrelia burgdorferi, the etiologic agent of Lyme borreliosis, has been only partially defined. In vitro antimicrobial susceptibility studies of B. burgdorferi have been limited in part by the lack of standardized methods. The existing susceptibility data from different studies are difficult to compare because of differences in test conditions, inoculum concentrations, and endpoint determinations (33). B. burgdorfien has been reported to be most susceptible in vitro to erythromycin, azithromycin, clarithromycin, ceftriaxone, and cefotaxime (17-21, 27, 28, 35, 36). Tetracycline, doxycycline, ampicillin, and penicillin G have been reported to have less activity against the organism (18, 21, 35). The spirochetes are resistant to aminoglycosides, rifampin, trimethoprim-sulfamethoxazole, and ciprofloxacin (18, 21, 35). Wide variations in the MICs and MBCs of most antibiotics tested have been reported (26, 33). Furthermore, in vitro results have not always correlated with clinical experience (34, 41, 45). Although erythromycin has excellent in vitro activity against B. burgdorferi, clinically it has been less effective than tetracycline, doxycycline, or penicillin in the treatment of Lyme borreliosis (37, 41). The investigation described here was designed to develop a standardized method for in vitro susceptibility testing of borrelias. We report here the in vitro susceptibility data we obtained w...
We describe three patients with AIDS who developed clinically significant infection with Mycobacterium haemophilum. One patient had skin and bone involvement and suspected laryngeal involvement; the second had extensive abdominal adenopathy with partial bowel obstruction; and the third presented with limited skin involvement. Each patient responded transiently to antimycobacterial therapy, but disease recurred and progressed in all three cases. Recovery of M. haemophilum requires a high level of clinical suspicion and special handling of mycobacterial cultures by the microbiology laboratory, including cultivation on enriched chocolate agar or heme-supplemented media and incubation at 30 degrees C for up to 8 weeks. Characteristic patterns of drug susceptibility for this organism have been only partially defined. Reported responses to antimycobacterial therapy in AIDS patients with M. haemophilum infection have been poor, and the optimal therapeutic regimen is not yet known. The prognosis for recovery appears to depend heavily on host-related factors, particularly the degree of immunosuppression.
Urban minority HIV-infected patients receiving combination antiretroviral therapy including a protease inhibitor may be at increased risk for the development of hyperglycemia and diabetes mellitus. Risk factors for diabetes mellitus should be identified and blood glucose monitored in all patients receiving protease inhibitors.
Borrelia burgdorferi, a spirochete and the causative agent of Lyme disease, has been reported to be susceptible to a variety of antimicrobial agents. In this investigation, the action of vancomycin, a glycopeptide antibiotic not previously known to have activity against spirochetes, against borrelias was examined. The in vitro activity of vancomycin against a variety of strains ofB. burgdorferi and one strain ofBorrelia hermsii was determined by use of a microdilution MIC method (L. L. Dever, J. H. Jorgensen, and A. G. Barbour, J. Clin. Microbiol. 30:2692Microbiol. 30: -2697Microbiol. 30: , 1992. MICs ranged from 0.5 to 2 ,ug/ml. MICs of the glycopeptides ristocetin and teicoplanin and the lipopeptide daptomycin against strain B31 ofB. burgdorferi were all .8 ,ug/ml. Subsurface plating, time-kill studies, synergy studies, and electron microscopy were used to investigate further the activity of vancomycin against B31. The MBC of vancomycin was 2 ,ug/ml. Time-kill curves demonstrated .3-loglounit (99.9%o) killing of the final inoculum after 72 h by vancomycin concentrations twice the MIC. Synergy between vancomycin and penicillin was demonstrated at concentrations one-fourth the MIC of each drug. In electron microscopy, B31 cells exposed to vancomycin showed a disruption of cellular integrity and were indistinguishable from those exposed to penicillin. These studies demonstrate another class of microorganisms susceptible in vitro to vancomycin.Lyme disease is the most common arthropod-borne disease in the United States and Europe (36, 39). The disease, caused by the spirochete Borrelia burgdorfien and transmitted primarily by ticks of the genus LIxodes, may be acute and self-limited or may progress to a chronic state with skin, joint, cardiac, and neurological involvement. Although many antibiotics have been used successfully in the treatment of Lyme disease, the full spectrum of antibiotic susceptibility of B. burgdorfien has not been fully defined. B. burgdorferi has been reported to be susceptible in vitro to a variety of antibiotics, including penicillin, amoxicillin, ceftriaxone, cefotaxime, cefuroxime, doxycycline, tetracycline, erythromycin, clarithromycin, and azithromycin (2,15,18,19,31). Oral doxycycline, amoxicillin and, to a lesser extent, erythromycin have been the antibiotics recommended most often for the treatment of the early stages of Lyme disease (11,27,32,36). Recent evidence suggests that oral cefuroxime and azithromycin are also effective in the early stages (23,25). For central nervous system infection and for late complications of Lyme disease, intravenous penicillin G and intravenous ceftriaxone have been the antibiotic therapies most often used (13,14,(36)(37)(38).In the present study, we explored the action of vancomycin, a glycopeptide antibiotic, against borrelias. Although vancomycin is primarily thought of as an antibiotic for use against gram-positive bacteria, we pursued this investigational tack for the following reasons: (i) some gram-negative bacteria, such as certain strains of...
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