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PubMed1984

Rapid antimicrobial susceptibility testing of Gram-negative clinical isolates with the AutoMicrobic system.

Comparisons of the antimicrobial susceptibility patterns of clinical isolates of the family Enterobacteriaceae and Pseudomonas aeruginosa were made by using Kirby-Bauer disk diffusion, the MicroMedia system broth microdilution, and the AutoMicrobic system. The Kirby-Bauer system compared favorably with the MicroMedia system (95% essential correlation with 90% complete agreement). The AutoMicrobic system also compared favorably with both the Kirby-Bauer system (93% essential correlation with 87% complete agreement) and the MicroMedia system (97% essential correlation with 85% complete agreement). These data indicate that the AutoMicrobic system results are comparable to those of the MicroMedia and the Kirby-Bauer systems. Furthermore, the AutoMicrobic system offers a more rapid system (6 to 10 h), than the traditional systems, without sacrificing accuracy (16 to 24 h).

Anti-Bacterial Agents↗
PubMed1977

Techniques for anaerobic susceptibility testing.

Minimal inhibitory concentrations (MICs) of antimicrobial agents for anaerobic bacteria can be determined by agar dilution and broth dilution (including microdilution) techniques. If MICs are not determined routinely, the disk broth or category methods are recommended for routine use. The Bauer-Kirby disk diffusion method and its interpretative standards should not be used for anaerobes.

Anaerobiosis↗
PubMed1987

Improved medium for antimicrobial susceptibility testing of Haemophilus influenzae.

The need for complex growth media has complicated routine susceptibility testing of Haemophilus influenzae because of antagonism of certain antimicrobial agents by the medium or because of difficulties in interpretation of growth endpoints. Haemophilus test medium (HTM) is a simple, transparent medium for broth- or agar-based tests with H. influenzae. HTM incorporates Mueller-Hinton medium with additions of 15 micrograms of hematin per ml, 15 micrograms of NAD per ml, and 5 mg of yeast extract per ml as growth-promoting additives. Agar or broth microdilution MICs of 10 antimicrobial agents for a collection of 179 H. influenzae isolates determined by using HTM compared favorably with MICs determined by the conventional agar or broth dilution methods recommended by the National Committee for Clinical Laboratory Standards. Disk diffusion tests performed with HTM allowed accurate categorization of susceptible and resistant strains and were easier to interpret than tests performed with Mueller-Hinton chocolate agar. A particular advantage of HTM was the reliability of broth- or agar-based test results with trimethoprim-sulfamethoxazole. The results of the study suggest modification of current National Committee for Clinical Laboratory Standards MIC-interpretive criteria for H. influenzae with amoxicillin-clavulanate, chloramphenicol, and trimethoprim-sulfamethoxazole. Error rate-bounded analysis of MICs and disk diffusion zone sizes also suggest modified zone-interpretive criteria for ampicillin, amoxicillin-clavulanate, chloramphenicol, and tetracycline with HTM or conventional media. Interpretive zone sizes are newly proposed for cefaclor and rifampin disk diffusion tests.

Anti-Bacterial Agents↗
PubMed1999

Antimicrobial susceptibility of bacterial pathogens in the oropharynx of healthy children.

In a study to determine the prevalence and antimicrobial susceptibility of bacterial pathogens in the oropharynx of healthy children, throat swabs obtained from 1765 children were cultured and the organisms recovered tested by the disk diffusion method and the E test. Six hundred ninety-one children (39.1%) harbored Haemophilus influenzae, 112 (6.3%) Streptococcus pyogenes, 73 (4.1%) Moraxella catarrhalis, 52 (2.9%) Streptococcus pneumoniae, and 50 (2.8%) Neisseria meningitidis in their oropharynx. The rate of penicillin resistance was 2%, 0%, and 12%, respectively, for Streptococcus pneumoniae, Streptococcus pyogenes, and Neisseria meningitidis. Ampicillin resistance was observed in 8.6% of Haemophilus influenzae strains and 78% of Moraxella catarrhalis strains and was associated with the presence of beta-lactamase, except in one strain of Haemophilus influenzae. Five (4.4%) isolates of Streptococcus pyogenes were resistant to macrolides. The low level of resistance observed in this area contrasts with the high rates reported in the literature.

Anti-Bacterial Agents↗
PubMed2006

Are multidose over-the-counter artificial tears adequately preserved?

PURPOSE: To investigate artificial tears containing different preservatives for antimicrobial efficacy. Based on the challenge test outlined in the European Pharmacopoeia, products were tested in their original containers to see whether their component preservative had sufficient activity. METHODS: Five brands of over-the-counter artificial tears each containing different preservatives (benzalkonium chloride/EDTA, parabens, chlorobutanol, silver chloride complex, and Purite-stabilized oxychloro complex) were inoculated with test microorganisms (Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans). Changes in the microbial start concentration with time were followed by plating onto growth media to provide a measure of the preservative efficacy. In another test, artificial tears were applied to paper disks that were then placed onto agar growth media seeded with microorganisms. Zones of inhibition were measured after incubation. RESULTS: Only the brand of artificial tears containing benzalkonium chloride/EDTA satisfied the major criteria for antimicrobial preservation for all the test microorganisms. Only a benzalkonium chloride/EDTA-containing disk placed on agar seeded with S. aureus produced a zone of inhibition in the agar diffusion test. CONCLUSION: The brand of artificial tears containing benzalkonium chloride/EDTA is suitable for sale in countries adopting the monographs of the European Pharmacopoeia. Other brands would only be suitable for sale if justified reasons for not meeting the major criteria for preservative efficacy can be provided.

Benzalkonium Compounds↗
PubMed2004

Community-acquired, methicillin-resistant and methicillin-susceptible Staphylococcus aureus musculoskeletal infections in children.

BACKGROUND: The clinical characteristics and virulence factors related to musculoskeletal infections caused by community-acquired, methicillin-resistant Staphylococcus aureus (MRSA) in children are not well-defined. METHODS: In this retrospective study, the demographics, hospital course and outcome of children with musculoskeletal infections were reviewed from medical records and by contacting patients or their physicians. Antimicrobial susceptibilities were determined by disk diffusion. Polymerase chain reaction was performed to detect genes encoding for virulence factors. Mann-Whitney, chi2 and Kaplan-Meier tests were used for statistical analysis. RESULTS: Community-acquired MRSA and community-acquired methicillin-susceptible S. aureus (MSSA) caused musculoskeletal infections in 31 and 28 children, respectively. The median numbers of febrile days after start of therapy were 4 and 1 for MRSA and MSSA patients, respectively (P = 0.001). The median numbers of hospital days were 13 and 8 for the MRSA and MSSA groups, respectively (P = 0.014). At follow-up, 2 patients in the MRSA and 1 in the MSSA group had developed chronic osteomyelitis. pvl and fnbB genes were found in 87 and 90% versus 24 and 64% in the MRSA versus MSSA groups, respectively. (P = 0.00001 and 0.017). Ten patients with pvl-positive strains had complications versus no patients with pvl-negative isolates (P = 0.002). CONCLUSIONS: Febrile days and hospital days were greater in children with musculoskeletal infection caused by MRSA than in those affected by MSSA, but no significant differences were found in the final outcome. pvl and fnbB genes were more frequent in the MRSA than in the MSSA strains. The presence of the pvl gene may be related to an increased likelihood of complications in children with S. aureus musculoskeletal infections.

Adolescent↗
PubMed1989

Evaluation of four newer antimicrobial agents in the Avantage susceptibility test system.

Antimicrobial elution disks containing amoxicillin-clavulanic acid (Augmentin), cefotetan, ciprofloxacin, or norfloxacin were tested in the Avantage automated susceptibility test system. Performance was compared against an agar diffusion procedure in a three-site collaborative study. Results of 1,500 comparison with amoxicillin-clavulanic acid showed a full accord (agreement of both systems) of 93.6% and an essential accord (agreement excluding minor discrepancies) of 97.6%. Results for cefotetan showed a full accord of 95.1% and an essential accord of 98.3% by the two methods. Results for both ciprofloxacin and norfloxacin were in full accord for more than 98% of tests with gram-negative bacilli and staphylococci, but tests with enterococci gave 38 and 26.1% minor discrepancies (the result of one method was resistant or susceptible and the result of the other method was intermediate), respectively. The results indicated that the Avantage test system is accurate and reliable and provides appropriate determination of bacterial susceptibility with the four antibiotics tested.

Amoxicillin↗
PubMed2004

Occurrence of extended-spectrum beta-lactamase in clinical isolates of Klebsiella pneumoniae in a University Hospital, Thailand.

The occurrence and antimicrobial susceptibility of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae in patients attending Siriraj Hospital in Bangkok from August 2000 to January 2001 were determined. ESBL-producing isolates were screened with four different methods: disk diffusion according to the National Committee for Clinical Laboratory Standards (NCCLS) guidelines, Etest ESBL (CT/CTL and TZ/TZL), Oxoid combination discs and MIC Etest strip. Antimicrobial susceptibility testing were determined by a microdilution automatic method (VITEX system, bioMerieux). Of 22,178 clinical specimens, 400 (1.8%) K. pneumoniae were isolated Of 26% (104/400) of these isolates were suspected to be ESBL-producing. Rates of detection of ESBL-producing K. pneumoniae were 18.67%, 30% and 23.78% for blood, sputum and urine samples, respectively. Susceptibility testing has revealed that all 70 tested isolates including 53 isolates from blood and sputum and 17 isolates from urine samples were susceptible to imipenem (MIC< or =4 mg/L). None of the tested isolates were susceptible to cephalosporins, cephamycin and aztreonam. Rate of susceptibility to ciprofloxacin, levofloxacin, gentamicin and tobramycin were 60%, 64%, 28% and 9%, respectively, for isolates from blood and sputum; 71%, 71%, 18% and 6% for urinary isolates. The present findings revealed a high occurrence rate of multi-drug resistance ESBL-producing K. pneumoniae in patients attending the university hospital. Imipenem was highly active against ESBL-producing K. pneumoniae.

Anti-Bacterial Agents↗
PubMed1991

Susceptibility of Xanthomonas maltophilia and amikacin-resistant gram-negative bacteria to newer antimicrobials.

The susceptibility of Xanthomonas maltophilia and amikacin-resistant gram-negative bacteria to a variety of newer antimicrobials was determined. Sixty-three amikacin-resistant isolates were collected from 61 inpatients at a tertiary-care hospital between 1985 and 1988. The organisms included Xanthomonas maltophilia (24 isolates), Pseudomonas aeruginosa (16), Pseudomonas species (3), Serratia marcescens (10), Flavobacterium meningosepticum (4), Enterobacter species (3), Acinetobacter calcoaceticus var. anitratus (2), and Alcaligenes xylosoxidans (1). Amikacin resistance was initially determined by using the Kirby-Bauer disk diffusion method. The isolates were batched, and the minimum inhibitory concentrations (MICs) of 11 antimicrobials including amikacin were measured by using the standard agar dilution method. Of the 63 isolates initially found to be amikacin resistant by the disk diffusion method, 37% were found to be amikacin susceptible by MIC testing. Of 38 truly amikacin-resistant isolates, 76% were susceptible to ciprofloxacin, 63% to ofloxacin, 50% to imipenem-cilastatin, 47% to cefoperazone, 45% to ceftazidime, 13% to ceftizoxime, 11% to aztreonam, 11% to ceftriaxone, 5% to cefotetan, and 3% to amdinocillin. Ciprofloxacin and ofloxacin inhibited X. maltophilia to the greatest degree, with median MICs of 1 microgram/ml each. Fifteen amikacin-resistant Ps. aeruginosa isolates were inhibited by ciprofloxacin, imipenem, and ceftazidime, with median MICs of 0.375, 3, and 2 microgram/ml, respectively. Of the antimicrobials tested, ciprofloxacin had the greatest activity against amikacin-resistant organisms in vitro.

4-Quinolones↗
PubMed2004

Evaluation of extended spectrum beta lactamase in urinary isolates.

BACKGROUND & OBJECTIVES: Urinary tract infection (UTI) remain the common infections diagnosed in outpatients as well as in hospitalized patients. Current knowledge on antimicrobial susceptibility pattern of uropathogens is mandatory for appropriate therapy. Extended spectrum beta lactamases (ESBL) hydrolyse expanded spectrum cephalosporins like ceftazidime, cephotaxime which are used in the treatment of UTI. ESBL producing bacteria may not be detectable by routine disk diffusion susceptibility test, leading to inappropriate use of antibiotics and treatment failure. Not much information on ESBL producing organisms causing UTI is available from India. An effort was therefore made to study the ESBL producing uropathogens and also the susceptibility patterns of ESBL and nonESBL producers. METHODS: Urinary isolates from symptomatic UTI cases attending or admitted to the Indira Gandhi Medical College and Hospital, Nagpur were identified by conventional methods. Antimicrobial susceptibility testing was done by Kirbey Bauer's disc diffusion method. Isolates resistant to cephotaxime were tested for ESBL production by double disc synergy test method. RESULTS: Of the 217 isolates, 87 were cephotaxime resistant Gram-negative bacilli. Of these, 42 (48.3%) were found to be ESBL producers. Escherichia coli, Klebsiella pnuemoniae and Acinetobacter were ESBL producing species. Multidrug resistance was found to be significantly (P<0.05) more in ESBL producing isolates (90.5%) than non ESBL producers (68.9%). INTERPRETATION & CONCLUSION: In the present study a large number of uropathogens were found to be ESBL producers. Most of the ESBL producing isolates were multidrug resistant. Monitoring of ESBL production and antimicrobial susceptibility testing are necessary to avoid treatment failure in patients with UTI.

Drug Resistance, Multiple, Bacterial↗
PubMed2002

[Susceptibility to antimicrobial agents of bacteria isolated from pregnant, postpartum women, and newborns from zones with high irradiation risk].

Susceptibility of 350 strains of staphylococci, isolated from pregnant women, puerperal and newborns and of 170 strains, isolated from obstetrical hospital environment at the region with high risk of radiation after accident was determined. The tested bacterial strains were the following: 56--Staphylococcus aureus, 152--S. epidermidis, 142--S. saprophyticus, isolated from women and newborns; strains isolated from hospital environment included 120 strains of S. saprophyticus and 50 strains E. coli. The tested antimicrobial factors were the following: 22 antibiotics, 2 bioantibiotics of the breast milk and blood (lysozyme, betalysin) not separated from the substrate and tested on test-cultures of M. luteus and B. subtilis, and 5 desinfectants. Analysis was performed by common disk-diffusion method and by contact method elaborated before. High resistance of staphylococci to many antibiotics, bioantibiotics and disinfectants was demonstrated. The resistance is considered to be due to high radiation background because it is much higher than resistance frequency of the similar strains isolated at the safe areas. The resistance to antimicrobial factors was higher among the opportunistic and saprophyte staphylococci along with appearance of pathogenic factors and activation of persistence properties.

Anti-Bacterial Agents↗
PubMedDate not supplied

Antimicrobial susceptibility of Neisseria gonorrhoeae isolates from a military population in San Diego.

Neisseria gonorrhoeae isolates were studied to determine their patterns of antimicrobial susceptibility and possible chemotherapeutic implications. Of 370 consecutive isolates, 32 (8.7%) were penicillinase-producing N. gonorrhoeae (PPNG). The remaining 338 were subjected to disk-diffusion tests, and those apparently resistant to penicillin, tetracycline, or spectinomycin were tested by an agar-dilution method. The dilution test showed that 5.4% (20/370) were penicillin-resistant, non-PPNG strains, of which 100%, 90%, and 45% were also resistant to tetracycline, cefoxitin, and erythromycin, respectively. No resistance to spectinomycin or ceftriaxone was demonstrated, although there was an association between minimum inhibitor concentrations (MICs) of penicillin of greater than or equal to 1.0 microgram/ml and increased MICs of ceftriaxone. The overall incidence of penicillin resistant isolates, including PPNG, was 14.1% (52/370). Of the 20 penicillin-resistant, non-PPNG strains, all were also resistant to tetracycline, and another 21 exhibited tetracycline resistance but were sensitive to penicillin. The in-vitro data suggested that: (1) neither penicillin, tetracycline, nor cefoxitin were acceptable drugs for routine treatment of gonorrhea in our population during the study period; (2) spectinomycin and ceftriaxone continue to demonstrate adequate in-vitro activity against N. gonorrhoeae despite increasing in-vitro resistance to penicillin; and (3) non-plasmid-mediated resistance to penicillin may predict future resistance to ceftriaxone.

Anti-Bacterial Agents↗
PubMed1979

In vitro susceptibility testing of anaerobic bacteria.

In vitro susceptibility testing of anaerobic bacteria should be limited to isolates from persistent or recurrent infections that have been treated adequately and appropriately with antimicrobial agents and, in reference centers, to collections of isolates in order to monitor alterations in susceptibility of species to various antimicrobial agents. An agar dilution reference method is being evaluated currently; however, practicality limits sporadic testing of single isolates to disk elution or broth dilution techniques. No single disk diffusion method has yet been found to be acceptable for testing anaerobic bacteria, and the results obtained with standardized procedures for aerobic and facultatively anaerobic bacteria are not applicable to anaerobic bacteria.

Anti-Bacterial Agents↗
PubMed1986

Susceptibility testing of methicillin-resistant Staphylococcus aureus with three commercial microdilution systems.

The antimicrobial susceptibilities of 100 methicillin-resistant Staphylococcus aureus isolates were determined concurrently by API Uniscept KB, Micro-Media, MicroScan, standardized disk diffusion, and reference broth microdilution to evaluate whether these commercial microdilution systems would reliably defect methicillin-resistant S. aureus. The methicillin minimal inhibitory concentration for all isolates was greater than or equal to 16 micrograms/ml as determined by the reference minimal inhibitory concentration panels containing 2% NaCl supplemented Mueller-Hinton broth. Using the breakpoints established by the National Committee for Clinical Laboratory Standards for reporting susceptible and resistant methicillin results, there was 100% agreement between the reference methods and API Uniscept KB at 24 hr. The Micro-Media and MicroScan systems had 47% and 8% very major discrepancies at 24 hr, respectively. At 48 hr, these two systems exhibited 15% and 0% very major discrepancies. Micro-Media and MicroScan were in agreement with the reference microdilution method (+/- 1 log2 dilution) for 62% and 68% of the strains at 24 hr, respectively and 88% and 85% of the isolates at 48 hr, respectively. The results of this study indicate that API Uniscept KB would provide a practical and reliable method for the detection of methicillin-resistant S. aureus.

Anti-Bacterial Agents↗
PubMed1987

In vitro activities of aztreonam, imipenem, and amoxycillin-clavulanate against ampicillin-resistant Haemophilus influenzae.

Two hundred and fifty-seven ampicillin-resistant clinical isolates of Haemophilus influenzae were tested by disk diffusion and MIC determination for susceptibility to aztreonam, imipenem, and amoxycillin combined with clavulanate. The modal MICs and MICs for 50 and 90% of isolates of all three antimicrobial agents for the 157 beta-lactamase-positive strains did not differ significantly from figures obtained with 2,201 ampicillin-susceptible H. influenzae by the same methods. Aztreonam and amoxycillin-clavulanate were less active, as reflected by an increase in these parameters, against 38 beta-lactamase-negative isolates requiring greater than or equal to 4 micrograms of ampicillin per ml for inhibition and 62 strains considered to have an intermediate degree of nonenzymic (intrinsic) resistance to ampicillin (zone diameters of less than 20 mm with 2-micrograms ampicillin disks and MICs of 1 or 2 micrograms/ml). There was no detectable difference in imipenem activity against these 100 strains compared with that observed against the ampicillin-susceptible group. Of the 24 strains requiring at least 4 micrograms of imipenem per ml for inhibition, 13 also showed reduced susceptibility to ampicillin (5 beta-lactamase-positive and 8 beta-lactamase-negative isolates). A lack of correlation between reduced susceptibility to imipenem and the other beta-lactams was observed.

Amoxicillin↗
PubMed1998

Antimicrobial activity of gatifloxacin tested against Neisseria gonorrhoeae using three methods and a collection of fluoroquinolone-resistant strains.

Gatifloxacin, a new 8-methoxy fluoroquinolone, was tested against 131 strains of Neisseria gonorrhoeae by reference agar dilution, disk diffusion, and Etest (AB BIODISK, Solna, Sweden) methods on supplemented GC agar. Gatifloxacin activity was equal to ciprofloxacin (MIC50, 0.008 microgram/mL) against strains fully susceptible to fluoroquinolones, but was generally four-fold more active (MIC90, 0.064-0.094 microgram/mL) against strains with par C or gyr A mutations and resistance to ciprofloxacin. Etest results were comparable to those generated by the agar dilution test [correlation coefficient (r) = 0.97]. Gatifloxacin zone diameters using 5-microgram disks also correlated well (r = 0.86-0.87) with the agar dilution and Etest MIC results. Breakpoints for laboratory testing of Neisseria gonorrhoeae strains await clinical trial outcome correlations, but susceptibility at < or = 0.125 or < or = 0.25 microgram/mL (> or = 34 mm) seems appropriate. All three tests used in this study seem applicable for laboratory testing of isolates from patients with uncomplicated gonorrhoeae receiving therapy with gatifloxacin.

Anti-Infective Agents↗
PubMed2005

Effectiveness of steam pasteurization in controlling microbiological hazards of cull cow carcasses in a commercial plant.

The purpose of the study, carried out in a beef processing plant, was to evaluate the effectiveness of a new prototype for steam pasteurization treatment in controlling microbiological hazards. Samples were taken by swabbing randomly selected sites before and after pasteurization and again after chilling to obtain total aerobic counts (TAC), total coliform counts (TCC), and generic Escherichia coli counts (ECC) on Petrifilm plates and to determine the prevalence of Salmonella spp., Listeria monocytogenes, and E. coli O157:H7 using standard enrichment techniques. Escherichia coli and L. monocytogenes strains were tested for various factors associated with their virulence by using colony hybridization and polymerase chain reaction (PCR), respectively. Antimicrobial susceptibility was determined for each isolate that was potentially pathogenic to humans by using the disk-diffusion method. Mean values for TAC, TCC, and ECC were 2.18, 0.16, and 0.06 log10 CFU/cm2, respectively, before pasteurization; 1.17, 0.03, and 0.01 log10 CFU/cm2 after pasteurization; and 0.89, 0.02, and 0.01 log10 CFU/cm2 after chilling. Prevalence of L. monocytogenes, Salmonella spp., and E. coli O157:H7 on carcasses was 0.8%, 0.0%, and 0.0%, respectively, before pasteurization; 2.6%, 0.0%, and 0.0% after pasteurization; and 3.1%, 0.1%, and 0.0% after chilling. The prevalence of E. coli containing > or = 1 virulence gene was 14.7%. More specifically, 11.88% of the isolates obtained before pasteurization, 22.2% obtained after pasteurization, and 31.2% obtained after chilling had virulence genes. All L. monocytogenes isolates tested positive for the presence of 3 major virulence factors (hlyA, inlB, and plcB). Antibiograms showed that certain isolates were susceptible to all antibiotics, some showed an intermediate sensitivity, and others were multiresistant. Overall, these results suggest that steam pasteurization is an effective means of improving safety quality of beef carcasses. However, pasteurization may indirectly contribute to the growth of some pathogenic microorganisms, such as L. monocytogenes.

Abattoirs↗