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PubMed1999

Activity of gatifloxacin against Haemophilus influenzae and Moraxella catarrhalis, including susceptibility test development, E-test comparisons, and quality control guidelines for H. influenzae.

In vitro antimicrobial activity and susceptibility testing interpretation criteria and quality control were studied for gatifloxacin, a new 8-methoxy fluoroquinolone, tested against Haemophilus influenzae. Moraxella catarrhalis (600 strains) and H. influenzae (1,400 strains) from the SENTRY Antimicrobial Surveillance Program in North America (Canada and the United States) were also tested against gatifloxacin and 12 other antimicrobial agents. Gatifloxacin (MIC at which 90% of the isolates are inhibited [MIC90], </=0.03 microg/ml; 100.0% of strains inhibited at </=2 microg/ml) was the most active agent tested against H. influenzae and was similar to four comparison fluoroquinolones (MICs, </=0.03 to 2 microg/ml) against M. catarrhalis. A subset of 300 recent clinical isolates of H. influenzae were tested by using media (Haemophilus Test Medium agar and broth) and procedures recommended by the National Committee for Clinical Laboratory Standards (NCCLS) and with the E-test (AB BIODISK, Solna, Sweden). Gatifloxacin (MIC50, 0.008 microg/ml) was slightly more active than levofloxacin, and E-test results were generally elevated by 0.5 log2 dilution step compared to reference MICs. The gatifloxacin 5-microg disk test produced zone diameters that were routinely above 30 mm for H. influenzae strains, corresponding to gatifloxacin MICs of 0.008 or 0. 016 microg/ml. The gatifloxacin susceptibility breakpoint proposed for nonfastidious species (</=2 microg/ml; >/=18 mm) was also suggested for H. influenzae testing. No interpretive errors were observed. Quality control guidelines for H. influenzae ATCC 49247 were determined by using the NCCLS M23-T3 (1998) study design. The results from the nine-laboratory protocol suggested the following control ranges: for broth microdilution tests, 0.004 to 0.03 microg/ml; for disk diffusion testing, 33 to 41 mm. Gatifloxacin appears to be a potent anti-Haemophilus fluoroquinolone compound with in vitro testing interpretive criteria that will produce accurate results (disk diffusion, broth microdilution, and E-test).

Anti-Bacterial Agents↗
PubMed2001

[Spread of Enterobacteriaceae producing broad-spectrum beta-lactamase and the development of their incidence over a 16-month period in a university hospital center].

Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBLE) constitute with methicillin-resistant Staphylococcus aureus the main multiresistant bacteria recovered in French hospitals. Our objectives were to evaluate these ESBLE diffusion in our teaching hospital and to follow their incidence during a 16-month period, whereas a control programme (barrier precautions) had been implemented in the beginning of 1999. This study was conducted in a teaching hospital containing 1800 beds, from February 1999 to May 2000. All ESBLE isolated in clinical or screening samples were included. Duplicates (same bacteria in the same patient) were excluded. The detection of the ESBL was performed with the double-disk diffusion test. Incidence densities were determined with their 95% confidence interval (CI95%). Their evolution by four-month period was evaluated with the chi-square test for trend. During the 16-month period, 229 ESBLE were isolated. The incidence was 0.35 per 1000 patient-days (PD) (CI95% = [0.30-0.40]) for the whole hospital. It was 0.47/1000 PD (CI95% = [0.38-0.56]) in medical wards, 0.29/1000 PD (CI95% = [0.20-0.38]) in surgical wards and 1.32/1000 PD (CI95% = [0.90-1.74]) in intensive care units. Enterobacter aerogenes strains represented more than 75% of all ESBLE, whereas Klebsiella pneumoniae stains represented only 8.6%. During the study, the incidence of ESBLE and the proportion of strains acquired in our hospital decreased significantly (p < 0.0001 and p < 0.001 respectively). Indeed, between the first eight-month period and the last one, the incidence of ESBLE acquired in our hospital decreased by 55%, whereas the incidence of imported strains increased slightly. This study shows that the diffusion of ESBLE concerns the entire hospital. The implementation of a control programme of the spread of multiresistant bacteria allowed us to reduce significantly the incidence of ESBLE. This incidence seemed to be stable for several months. The implementation of a policy which restricts antimicrobial use would allow us to complete the the efficacy of barrier precautions.

Academic Medical Centers↗
PubMed2005

Synthesis, surface active and antimicrobial properties of new alkyl 2,6-dideoxy-L-arabino-hexopyranosides.

Synthesis of alkyl 2,6-dideoxy-L-arabino-hexopyranosides was accomplished by the reaction of 1,5-anhydro-2,6-dideoxy-L-arabino-hex-1-enitol with fatty alcohols in dichloromethane, catalyzed by triphenylphosphine hydrobromide. Reaction with octanol and dodecanol gave the corresponding alpha-glycosides in 50% and 42% yield, the beta-glycosides in 20% and 21% yield and the alpha-anomer of the Ferrier product in 10% and 9% yield, respectively. Deacetylation of the alpha-/beta-glycosides with sodium methoxide in methanol afforded the amphiphilic L-arabino-hexopyranosides in 94-99% yield. The surface tension at the air-water interface of the octyl L-glycosides and of the dodecyl alpha-L-glycoside aqueous solutions at 35 degrees C was measured with a du Noüy ring tensiometer and surface properties such as critical micelle concentration (CMC), relative surface excess, molecular area at the interface and Gibbs micellization free energy were evaluated. The stereochemistry of the hexopyranoside ring in unimers and aggregates is correlated to the hydrophobicity and packing efficiency on the air-water interface. The antibacterial and antifungal activities of the surface-active glycosides were evaluated using the paper disk diffusion method. The dodecyl alpha-L-arabino-hexopyranoside was quite active over Bacillus cereus and Bacillus subtilis, while low activity was found for this glycoside over Enterococcus faecalis and Listeria monocytogenes. The octyl glycosides tested showed low activity over almost all the above-mentioned bacteria, and also over the fungus Candida albicans. No inhibition of Salmonella enteritidis and of the filamentous fungus Aspergillus niger was detected for any of the compounds tested.

Adsorption↗
PubMed1986

In vitro susceptibilities of four species of coagulase-negative staphylococci.

The in vitro susceptibilities of 260 strains of coagulase-negative staphylococci to penicillin G, oxacillin, nafcillin, methicillin, cephalothin, and seven non-beta-lactam antimicrobial agents were determined and compared with the susceptibilities of 54 strains of Staphylococcus aureus with known patterns of susceptibility. Penicillin G susceptibility for S. aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus hominis was readily determined by using beta-lactamase tests with induced cells and with a standardized microdilution test. MIC criteria for susceptibility used for S. aureus were applicable to the coagulase-negative species. Percentages of organisms susceptible were as follows: S. epidermidis, 7%; S. haemolyticus, 5%; and S. hominis, 47%. Oxacillin susceptibility for these four species was readily determined by using a modification of the microdilution test. MIC criteria for susceptibility used for S. aureus were applicable to S. haemolyticus and S. hominis, but alternate criteria were necessary for S. epidermidis. Percentages of organisms susceptible were as follows: S. epidermidis, 29%; S. haemolyticus, 36%; and S. hominis, 97%. Staphylococcus saprophyticus differed from the other staphylococcal species; all strains were beta-lactamase negative and were penicillin susceptible but had higher penicillin G MICs than did susceptible strains of the other species. There was total cross resistance among the penicillinase-resistant penicillins and cephalothin for the coagulase-negative staphylococci as well as for S. aureus; oxacillin MICs were more reliable than MICs of the other drugs or a standardized disk diffusion test for distinguishing resistant from susceptible strains. Vancomycin, rifampin, and ciprofloxacin were consistently active against all staphylococci. Erythromycin, clindamycin, gentamicin, and trimethoprim-sulfamethoxazole were more active against oxacillin-susceptible staphylococci than against oxacillin-resistant staphylococci.

Anti-Bacterial Agents↗
PubMed2003

Antimicrobial properties of commercial annatto extracts against selected pathogenic, lactic acid, and spoilage microorganisms.

Annatto preparations are used to impart distinctive flavor and color to foods and are a primary colorant in dairy foods such as cheese and butter. There are several reports indicating that certain fractions of the annatto plant have biological activities against microorganisms of significance in food fermentation, food preservation, and human health. However, little is reported describing the nature of the antimicrobial compound(s) or their potential presence in commercial annatto colorant preparations. This study was conducted to determine whether commonly available annatto extracts are capable of influencing the outgrowth of selected lactic acid, spoilage, and pathogenic microorganisms. Disk diffusion and tube macrodilution techniques were used to determine the MICs and MBCs of double-strength water-soluble annatto extracts. Standard antibiotic disks were used as controls for the disk diffusion assay. The results demonstrate that annatto has an inhibitory effect on Bacillus cereus, Clostridium perfringens, and Staphylococcus aureus, with MICs of 0.08, 0.31, and 0.16% (vol/vol) and diameters of inhibition of 9 to 10, 12 to 13, and 15 to 16 mm, respectively. A concentration of 0.63% (vol/vol) inhibited the growth of Streptococcus thermophilus, Lactobacillus casei subsp. casei, Lactococcus lactis, and Paenibacillus polymyxa. The MICs for Listeria monocytogenes and Enterococcus durans were 1.25 and 2.5% (vol/vol), respectively. No activity was detected against Lactobacillus plantarum, Bifidobacterium bifidum, yeasts, or selected gram-negative bacteria.

Bacteria↗
PubMed2001

In vitro evaluation of BI 397, a novel glycopeptide antimicrobial agent.

BI 397, a semi-synthetic amide derivative of the experimental glycopeptide, MDL 62,476 (A40926), has excellent in vitro activity against a wide range of Gram-positive organisms. In this extensive study, 630 contemporary (1998-2000) Gram-positive isolates were selected from various resistance surveillance studies for their resistance patterns to fluoroquinolones, macrolides-lincosamides-streptogramins, beta-lactams and glycopeptide agents. The BI 397 spectrum of activity was similar to that of other glycopeptides with a MIC90 of < or =0.5 microg/ml for all tested isolates with the exception of vancomycin-resistant enterococci Van A; (MIC90, 32 microg/ml). BI 397 was more potent than vancomycin and teicoplanin against Staphylococcus aureus (2- to 8-fold), beta-haemolytic streptococci (equal to >16-fold), viridans group streptococci (equal to >32-fold), and Corynebacterium spp. including C. jeikeium (8- to >16-fold). BI 397 was also more active than quinupristin/dalfopristin against all Gram-positive organisms tested with the exception of oxacillin-susceptible S. aureus, against which it had equal activity. BI 397 has little activity against Haemophilus influenzae (MIC90, 64 microg/ml) or other Gram-negative bacilli (MIC90, >64 microg/ml). BI 397 exhibited bacteriostatic activity (like the vancomycin control) versus most species, but was bactericidal against tested Streptococcus pneumoniae. In vitro testing conditions with blood supplemented or free protein containing media elevated BI 397 MIC results, and the 30-microg disk seems acceptable for further disk diffusion test development. Animal pharmacokinetic data published elsewhere suggest that BI 397 may be dosed less frequently than teicoplanin and the results of early studies in humans are awaited with interest, especially when treating teicoplanin-refractory coagulase-negative staphylococci.

Anti-Bacterial Agents↗
PubMed2004

Intravenous catheter infections associated with bacteraemia: a 2-year study in a university hospital.

The aim of this retrospective study was to assess the incidence and aetiology of central and peripheral venous catheter (C/PVC) infections during a 2-year period (1999-2000) and to determine the susceptibility of isolated microorganisms to various antimicrobial agents. Catheter tips were processed using the semiquantitative method and blood cultures were performed with the BacT/Alert automated system. Antibiotic susceptibilities were performed by disk agar diffusion and MICs were determined by Etest, according to NCCLS standards. During the study period, samples from 1039 C/PVC infections were evaluated, yielding 384 (37.0%) positive cultures. Blood cultures were also available from 274 patients, of which 155 (56.6%) yielded the same microorganism as from the catheter. No bloodstream infections were detected in 104 C/PVC-positive cases. Methicillin-resistant coagulase-negative staphylococci were the most frequent isolates, followed by Gram-negative bacteria, especially Pseudomonas aeruginosa. Resistance to glycopeptides among staphylococci and enterococci was not detected, whereas 60% of Gram-negative bacilli were resistant to beta-lactams.

Bacteremia↗
PubMed2000

Antimicrobial susceptibility profile of soil isolates of Nocardia asteroides from Kuwait.

OBJECTIVES: To find the antimicrobial susceptibility profile of 42 soil isolates of Nocardia asteroides against 14 antimicrobial agents representing beta-lactams, aminoglycosides, ciprofloxacin, minocycline, erythromycin and third generation cephalosporins. METHODS: The antimicrobial susceptibility was determined by the disk diffusion method using Mueller-Hinton agar medium. A homogeneous suspension giving an inoculum of 106-108 CFU/mL was used to streak the plates. The zone of inhibition was read after 36-48 h of incubation at 37 degrees C. RESULTS: All the soil isolates of N. asteroides were susceptible to amikacin, imipenem and tobramycin. Susceptibility to cephalosporins was quite variable; 86% of the isolates were susceptible to cefotaxime, 57% to ceftriaxone and 40% to cefamandole. Fifty-seven per cent of the isolates showed intermediate susceptibility to cefamandole, 33% to ceftriaxone and 5% to cefotaxime. Ninety-three per cent of the isolates were resistant to sulfamethoxazole alone or in combination with trimethoprim. CONCLUSIONS: The study reports a wide variation in the antimicrobial susceptibility profile of soil isolates of N. asteroides originating from a single geographical area. Of interest is the finding that over 90% of N. asteroides isolates were resistant to sulfamethoxazole without any previous exposure to this drug. This may have serious therapeutic implications as sulphonamides or the combination of trimethoprim-sulfamethoxazole is the therapy of choice for nocardiosis. Demonstration of resistance to beta-lactam antibiotics may be attributed to the presence of beta-lactamases which was detectable in > 90% of the soil strains of N. asteroides. The study underscores the importance of antimicrobial susceptibility testing for clinical isolates of Nocardia since individual strains show considerable differences in their susceptibility patterns necessitating therapeutic adjustments.

Anti-Bacterial Agents↗
PubMed1990

In vitro activity of sulbactam/ampicillin against ampicillin-resistant, beta-lactamase-producing bacteria isolated in Italian hospitals.

A multicenter study aimed at assessing the in vitro activity of sulbactam/ampicillin against a wide range of bacterial pathogens was performed using 2,209 clinical strains, all recently collected from inpatients in seven Italian centers and preliminarily screened as being ampicillin-resistant and beta-lactamase producers. In comparative disk diffusion trials using 8 large-spectrum antimicrobials, the percentage of resistance to sulbactam/ampicillin in staphylococci was similar to the percentage of resistance to netilmicin and lower than to the other antibiotics; with gram-negative bacteria, only netilmicin, ofloxacin, and, less consistently, cefotetan showed lower incidences of resistance. The minimal inhibitory concentrations (MICs) of ampicillin alone and sulbactam/ampicillin together were determined using the agar dilution method. The Enterobacteriaceae strains which shifted to ampicillin susceptibility in the presence of sulbactam averaged 68%, but values significantly above or below average were observed in some genera of this family. The percentage of strains which the presence of sulbactam rendered ampicillin-susceptible in vitro reached 97% in Haemophilus strains and 100% in branhamellae and gonococci. High percentages were also recorded in staphylococci, with a peak of 100% in oxacillin-susceptible Staphylococcus aureus strains. In general, center-to-center differences were relatively limited.

Ampicillin↗
PubMed2001

Antimicrobial sensitivity of Haemophilus influenzae isolates from bacterial conjunctivitis.

Haemophilus influenzae is one of the common bacterial pathogens which affect children. Resistance to frequently used antibiotics is becoming a significant problem in community isolates of common pathogens. A retrospective review was conducted of the serotypes and antimicrobial sensitivity of H influenzae isolates from bacterial conjunctivitis, over an 18-month period. Data on antimicrobial sensitivity (obtained by the National Committee for Clinical Laboratory Standards disk diffusion method) and beta-lactamase production, and typing results, were analysed. Ninety-nine isolates were recovered, of which 87 were typed. Most isolates were recovered from children under one year of age. Ninety-three percent were unencapsulated and biotypes I and IV were most common. H influenzae type b was recovered only twice. beta-lactamase was produced by 41% isolates while four isolates were ampicillin-resistant but did not produce beta-lactamase. All isolates were sensitive to chloramphenicol and 45% were co-trimoxazole sensitive. H influenzae is commonly isolated from bacterial conjunctivitis in Barbados and, as elsewhere, the majority of isolates are from small children and are non-encapsulated. However, there is a high prevalence of beta-lactamase production, which may serve as a reservoir for transfer to more invasive encapsulated strains of H influenzae within the oropharyngeal flora.

Adult↗
PubMed2003

Isolation of Staphylococcus schleiferi from dogs with pyoderma.

OBJECTIVE: To determine frequency with which Staphylococcus schleiferi could be isolated from dogs with pyoderma and antimicrobial susceptibility patterns of isolates that were obtained. DESIGN: Prospective study. ANIMALS: 54 dogs with a first (n = 14) or recurrent (40) episode of pyoderma. PROCEDURE: Specimens were obtained and submitted for bacterial culture. Isolates were identified as S schleiferi on the basis of growth and biochemical characteristics. Two isolates were submitted for DNA sequencing to confirm identification. Methicillin susceptibility was determined by means of disk diffusion with oxacillin-impregnated disks. RESULTS: 3 of 14 dogs examined because of a first episode of pyoderma and 12 of 40 dogs examined because of a recurrent episode of pyoderma were receiving antimicrobials at the time of specimen collection. Staphylococcus schleiferi was not isolated from any dog with first-time pyoderma but was isolated from 5 dogs with recurrent pyoderma that were not receiving antimicrobials at the time of specimen collection and 10 dogs with recurrent pyoderma that were receiving antimicrobials. Nine isolates were identified as S schleiferi subsp schleiferi, and 6 were identified as S schleiferi subsp coagulans. All S schleiferi subsp schleiferi isolates were resistant to methicillin, but only 2 S schleiferi subsp coagulans isolates were. Two methicillin-resistant isolates were also resistant to fluoroquinolones, and 1 isolate had intermediate susceptibility to fluoroquinolones. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that S schleiferi subsp schleiferi and S schleiferi subsp coagulans may be isolated from dogs with recurrent pyoderma. Although isolates from dogs with pyoderma were frequently resistant to methicillin, multiple drug resistance was uncommon.

Animals↗
PubMed2002

[Detection of Enterococcus with high-level aminoglycoside and glycopeptide resistance in Lactuca sativa (lettuce)].

BACKGROUND: The aim of this study was to assess the presence of enterococci highly resistant to aminoglycosides and glycopeptides in foods eaten uncooked, in order to evaluate their role as reservoirs of antimicrobial resistance. METHODS: We isolated 92 strains of enterococci from 79 samples of lettuce grown on farms near the city of Corrientes (Argentina). Enterococci were identified by standard methods. Antimicrobial susceptibility was determined by growth in azide dextrose broth supplemented with 500 microg/ml of gentamicin and 2,000 microg/ml of streptomycin, and by disk diffusion technique using disks with high levels of aminoglycosides, vancomycin and teicoplanin, in Müller Hinton agar. RESULTS: The most frequently detected species was E. faecium (32.61%), followed by E. faecalis (21.74%), E. gallinarum (13.04%), E. casseliflavus and E. mundtii (7.60%), E. hirae, (6.52%), E. durans (4.35%), E. raffinossus and E. saccharolyticus (2.17%), E. avium and E. malodoratus (1.10%). High-level resistance to streptomycin and gentamicin was found in 2 strains of E. Faecium. Resistance to streptomycin alone was observed in 2 strains of E. faecium, in 3 of E. hirae and in 1 of E. mundtii. Resistance only to gentamicin was not observed in any strain. None of the isolates showed glycopeptide resistance, except the intrinsically resistant species (E. gallinarum and E. casseliflavus). CONCLUSION: These results confirm the presence of enterococci within the community having susceptibility profiles similar to those of strains found in hospitals.

Anti-Bacterial Agents↗
PubMed2005

Antimicrobial-resistant and extraintestinal pathogenic Escherichia coli in retail foods.

BACKGROUND: Extraintestinal Escherichia coli infections are associated with specialized extraintestinal pathogenic E. coli (ExPEC) strains and, increasingly, with antimicrobial resistance. The food supply may disseminate ExPEC and antimicrobial-resistant E. coli. METHODS: In a prospective survey of 1648 diverse food items from 10 retail markets in the Minneapolis-St. Paul area during 2001-2003, selective cultures and disk-diffusion assays for the isolation and characterization of antimicrobial-resistant E. coli and polymerase chain reaction-based assays and O serotyping to define ExPEC-associated traits were performed. RESULTS: E. coli contamination exhibited a prevalence gradient from miscellaneous foods (9%), through beef or pork (69%), to poultry (92%; P<.001). Among E. coli-positive samples, similar prevalence gradients were detected for antimicrobial resistance (27%, 85%, and 94% of samples, respectively; P<.001) and ExPEC contamination (4%, 19%, and 46%, respectively; P<.001). By multivariate analysis, beef or pork and poultry from natural-food stores exhibited reduced risks of E. coli contamination and antimicrobial resistance. Indirect evidence suggested on-farm selection of resistance. Four food-source ExPEC isolates (from pea pods, turkey parts, ground pork, and vegetable dip) closely resembled selected human clinical isolates by O antigen and genomic profile. CONCLUSIONS: Retail foods may be an important vehicle for community-wide dissemination of antimicrobial-resistant E. coli and ExPEC, which may represent a newly recognized group of medically significant foodborne pathogens.

Animals↗
PubMed1999

Characterization of antimicrobial resistance in Streptococcus pyogenes isolates from the San Francisco Bay area of northern California.

During 1994 and 1995, 157 isolates of Streptococcus pyogenes from patients with invasive disease were consecutively collected in the San Francisco Bay area to determine the frequency of antimicrobial resistance. Susceptibility testing was performed according to the guidelines of the National Committee for Clinical Laboratory Standards by the disk method and by broth microdilution. For comparison of susceptibility patterns, an additional 149 strains were randomly collected from patients with pharyngitis. For San Francisco County, 32% of the isolates from invasive-disease-related specimens but only 9% of the isolates from throat cultures from the same period were resistant to erythromycin (P = 0.0007). Alameda County and Contra Costa County had rates of resistance of </=10% from isolates from all cultures. When the data were analyzed by hospital, the San Francisco County Hospital had a statistically higher rate of erythromycin resistance (39%) among the strains from serious infections compared to those from other counties (P = <0. 0003). For tetracycline, high rates of resistance were observed in San Francisco County for both isolates from patients with invasive disease (34%) and pharyngitis (21%) in the same period. Using pulsed-field gel electrophoresis, two clones, one at the San Francisco County Hospital and a second in the entire area, were identified. The latter clone exhibited resistance to bacitracin. Of 146 strains that were tested by microdilution, all were susceptible to penicillin. Clindamycin resistance was not seen among the erythromycin-susceptible strains, but two of the 39 erythromycin-resistant strains were also resistant to clindamycin. An additional 34 strains showed resistance to clindamycin when exposed to an erythromycin disk in the double-disk diffusion test, suggesting that the mechanism of erythromycin resistance is due to an erm gene. This study demonstrates a high rate of resistance to macrolides and tetracycline among S. pyogenes isolates in San Francisco County and shows that macrolide resistance is more common in strains from patients with invasive disease than in strains from those with pharyngitis.

Anti-Bacterial Agents↗
PubMed1999

The emergence of decreased susceptibility to vancomycin in Staphylococcus epidermidis.

BACKGROUND: Coagulase-negative staphylococci (CNS) are the major cause of nosocomial bloodstream infection. Emergence of vancomycin resistance among CNS is a serious public health concern, because CNS usually are multidrug-resistant, and glycopeptide antibiotics, among which only vancomycin is available in the United States, are the only remaining effective therapy. In this report, we describe the first bloodstream infection in the United States associated with a Staphylococcus epidermidis strain with decreased susceptibility to vancomycin. METHODS: We reviewed the hospital's microbiology records for all CNS strains, reviewed the patient's medical and laboratory records, and obtained all available CNS isolates with decreased susceptibility to vancomycin. Blood cultures were processed and CNS isolates identified by using standard methods; antimicrobial susceptibility was determined by using minimum inhibitory concentration (MIC) and disk-diffusion methods. Nares cultures were obtained from exposed healthcare workers (HCWs) to identify possible colonization by CNS with decreased susceptibility to vancomycin. RESULTS: The bloodstream infection by an S. epidermidis strain with decreased susceptibility to vancomycin occurred in a 49-year-old woman with carcinoma. She had two blood cultures positive for CNS; both isolates were S. epidermidis. Although susceptible to vancomycin by the disk-diffusion method (16-17 mm), the isolates were intermediate by MIC (8-6 microg/mL). The patient had received an extended course of vancomycin therapy; she died of her underlying disease. No HCW was colonized by CNS with decreased susceptibility to vancomycin. CONCLUSIONS: This is the first report in the United States of bloodstream infection due to S. epidermidis with decreased susceptibility to vancomycin. Contact precautions likely played a role in preventing nosocomial transmission of this strain, and disk-diffusion methods may be inadequate to detect CNS with decreased susceptibility to vancomycin.

Anti-Bacterial Agents↗
PubMed2003

Antimicrobial resistance of bacteria isolated from dairy cow milk samples submitted for bacterial culture: 8,905 samples (1994-2001).

OBJECTIVE: To determine whether antimicrobial resistance patterns of major mastitis pathogens isolated from milk samples from dairy cows have changed over time. DESIGN: Retrospective study. SAMPLE POPULATION: 8905 bacterial isolates obtained from milk samples submitted to the Wisconsin Veterinary Diagnostic Laboratory between January 1994 and June 2001. PROCEDURE: Antimicrobial susceptibility was determined by means of the Kirby-Bauer disk diffusion method. Logistic regression was used to determine whether percentages of isolates resistant to various antimicrobials changed over time. RESULTS: For the gram-positive mastitis pathogens, percentages of isolates resistant to various flactam antimicrobials did not increase over the course of the study. Percentage of Staphylococcus aureus isolates resistant to penicillin decreased from 49 to 30%; percentage of Streptococcus isolates resistant to penicillin decreased from 6 to 1%. Percentage of isolates resistant to erythromycin increased for S aureus, Escherichia coli, Enterobacter spp, Enterococcus spp, and Pasteurella spp. Percentage of isolates resistant to lincomycin increased for S aureus and Staphylococcus spp. Percentage of coagulase-negative Staphylococcus isolates resistant to pirlimycin increased from 6 to 19%. For several pathogens, percentages of isolates resistant to sulfisoxazole and to trimethoprim-sulfamethoxazole decreased. No pathogens had a significant increase in the percentage of isolates resistant to novobiocin-penicillin. CONCLUSIONS AND CLINICAL RELEVANCE: Results did not indicate a trend toward increased antimicrobial resistance among mastitis pathogens isolated from milk samples from dairy cows between 1994 and 2001. Reduced resistance to flactam antimicrobials was identified for several gram-positive mastitis pathogens.

Animals↗
PubMed2002

Comparative study of antimicrobial resistance of Pseudomonas aeruginosa strains isolated from patients of Caracas and Asunción in a 4-year-period.

The antimicrobial resistance of Pseudomonas aeruginosa to beta-lactams, aminoglycosides and ciprofloxacin was investigated in two Latin American hospitals, one in Venezuela and the other in Paraguay. The resistance of P. aeruginosa was investigated in 1,481 clinically isolated strains, 988 from Asunción and 493 from Caracas, collected between 1996 and 1999. Susceptibility was assessed by the disk diffusion method according to the National Committee for Clinical Laboratory Standards. 11.4% were resistant to cefoperazone, 11.4% to ceftazidime, 12.8% to piperacillin, 13.6% to amikacin, 18.2% to gentamicin, 11.1% to ciprofloxacin, and 6.7% to imipenem. There were significant differences in resistance patterns between isolates from Asunción and Caracas. Resistance was higher in Caracas. Despite similar antibiotic usage policies and other measures, differences in the resistance patterns of P. aeruginosa are evident in this study. The clinical and therapeutic implications of this resistance suggest the need to maintain surveillance in local settings, especially in developing countries such as Venezuela and Paraguay.

Drug Resistance, Microbial↗
PubMed1994

Antimicrobial susceptibility patterns of bacterial isolates at the American University Medical Center in Lebanon.

In Lebanon, knowledge of the prevailing pattern of bacterial resistance to antimicrobial agents has been limited, particularly because of 15 years of civil strife. Thus, the current study was conducted to determine the antimicrobial susceptibility patterns of nonselected bacterial isolates recovered from recent clinical specimens, using the standardized disk agar diffusion technique. A total of 5216 isolates (1443 Gram positive and 3773 Gram negative) were examined. Over 92% of Staphylococcus aureus and coagulase-negative staphylococci (CNS) were resistant to penicillins. Methicillin resistance was more frequently noted among CNS (28%) compared with S. aureus (18%). For the pneumococci, 27% of the isolates were resistant to penicillin G. High but variable rates of multidrug resistance were encountered among Acinetobacter spp., Pseudomonas spp., Serratia spp., Citrobacter spp., and Enterobacter spp. Ampicillin resistance was detected in 65% of Escherichia coli and in 20% of Haemophilus influenzae isolates. Although one resistant Salmonella typhi strain was observed, 17% of other Salmonella spp. and 60% of Shigella spp. proved to be resistant to ampicillin, chloramphenicol, and cotrimoxazole. Among Vibrio cholerae isolates, high resistance to tetracycline (71%) and trimethoprim-sulfamethoxazole (94%) was observed. The overall antimicrobial resistance rates in Lebanon seem to fall between figures reported from the Arabian Gulf countries (higher) and those from medical centers in the United States (lower).

Drug Resistance, Microbial↗