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PubMed1992

Evaluation of methods for typing coagulase-negative staphylococci.

One hundred and forty-two coagulase-negative staphylococci (CNS) isolated from dialysate effluent or skin of patients receiving continuous ambulatory peritoneal dialysis (CAPD) were typed by extended antibiogram (16 antibiotics) and biotype (26 reactions). These isolates were then typed by supplementary methods to determine the most suitable typing method for an epidemiological study of antibiotic resistance. These included phage typing, reverse phage typing, plasmid typing, whole-cell protein typing by SDS-PAGE with analysis by densitometry, and immunoblotting. The percentage of isolates typed successfully by the supplementary methods were: phage typing 20%, reverse phage typing 0%, plasmid typing 66%, SDS-PAGE 100%, immunoblotting 100%. The discrimination of each method was: phage typing 20%, plasmid typing 37%, SDS-PAGE 69%, immunoblotting 57%. Reproducibility was 88% for phage typing and 97% for plasmid typing. The reproducibility of the whole-cell protein typing was 83% if the same extracts were used but only 43% when separate protein extracts were analysed on separate occasions. However, strain relatedness was highly reproducible. The determination of an antibiogram-biotype profile was not a sufficiently accurate typing method for an epidemiological study of antibiotic resistance. Whole-cell protein typing by SDS-PAGE or immunoblotting was technically demanding but was the most effective of the supplementary methods for detecting erroneous discrimination and false matching produced by antibiogram-biotype combinations.

Bacterial Proteins↗
PubMed1999

Phenotypic and genotypic typing of food and clinical isolates of Enterobacter sakazakii.

Enterobacter sakazakii, designated a unique species in 1980, has been implicated as the causative organism in a rare but severe form of neonatal meningitis. Dried infant formula milk has been identified as a potential source of the organism. E. sakazakii isolates from dried infant formula available in Canada and clinical isolates obtained from Canadian hospital culture collections were characterised by phenotypic (biotype and antibiograms) and genotypic (ribotyping, random amplification of polymorphic DNA and pulsed-field gel electrophoresis) methods. Three biotypes and four antibiogram patterns were observed in the 18 isolates examined. Ribotyping with the Dupont Riboprinter microbial identification system divided the 18 isolates into 10 ribotypes. Three isolates from the same hospital had indistinguishable ribotyping patterns although each was isolated in a different year, as did three food isolates from one company. Pulsed-field gel electrophoresis (PFGE) and random amplification of polymorphic DNA (RAPD) profiles indicated minor differences between the isolates that were indistinguishable by ribotyping. PFGE (with the restriction endonucleases Xba1 and Spe1) and RAPD gave discrete patterns that enabled easy comparison of E. sakazakii isolates, with a high degree of discrimination. The discriminatory index showed RAPD and PFGE were shown to be the most discriminatory typing schemes for E. sakazakii, followed by ribotyping, biotyping and antibiograms.

Bacterial Typing Techniques↗
PubMed1972

In vitro antibiotic susceptibility of pseudomonads other than Pseudomonas aeruginosa recovered from cancer patients.

The increase in occurrence of infections due to opportunistic gram-negative bacilli in patients with impaired host defenses emphasizes the need for information on the antibiotic susceptibility of the organisms that colonize such patients. During a 20-month period, more than 100 pseudomonads which were not Pseudomonas aeruginosa were recovered from cancer patients at the Baltimore Cancer Research Center. These included P. fluorescens, P. putida, P. multivorans (cepacia), P. maltophilia, P. stutzeri, P. alcaligenes, and P. pseudoalcaligenes. Susceptibility tests with 12 antibiotics indicated that the intraspecies antibiograms for many of these species were more uniform than those of P. aeruginosa. The stability of susceptibility patterns allowed the antibiograms to be used as aids in the preliminary differentiation of these organisms. Variable antibiogram patterns were noted among certain species, i.e., P. fluorescens, P. stutzeri, and P. multivorans, whereas each of the other species had essentially one pattern. These in vitro studies showed that some of the Pseudomonas species other than P. aeruginosa were resistant to a number of antibiotics. Among these were antibiotics that are in general use for P. aeruginosa infections. Such differences in antibiotic susceptibilities emphasize the necessity for careful speciation of this group of microorganisms to assure proper epidemiological documentation of colonization and infection, as well as to ensure therapy with an antimicrobial agent to which the organism is susceptible in vitro.

Anti-Bacterial Agents↗
PubMed2003

Effectiveness of combination antimicrobial therapy for Pseudomonas aeruginosa bacteremia.

It remains controversial whether combination therapy, given empirically or as definitive treatment, for Pseudomonas aeruginosa bacteremia is associated with a better outcome than monotherapy. The aim of the present study was to compare the rates of survival among patients who received either combination therapy or monotherapy for P. aeruginosa bacteremia. We assembled a historical cohort of 115 episodes of P. aeruginosa bacteremia treated with empirical antipseudomonal therapy between 1988 and 1998. On the basis of susceptibility testing of the bacteremic P. aeruginosa isolate, we defined categories of empirical treatment, including adequate combination therapy, adequate monotherapy, and inadequate therapy, as well as corresponding categories of definitive therapy. Neither the adequacy of the empirical treatment nor the use of combination therapy predicted survival until receipt of the antibiogram. However, the risk of death from the date of receipt of the antibiogram to day 30 was higher for both adequate empirical monotherapy (adjusted hazard ratio [aHR], 3.7; 95% confidence interval [CI], 1.0 to 14.1) and inadequate empirical therapy (aHR, 5.0; 95% CI, 1.2 to 20.4) than for adequate empirical combination therapy. Compared to adequate definitive combination therapy, the risk of death at 30 days was also higher with inadequate definitive therapy (aHR, 2.6; 95% CI, 1.1 to 6.7) but not with adequate definitive monotherapy (aHR, 0.70; 95% CI, 0.30 to 1.7). In this retrospective analysis the use of adequate combination antimicrobial therapy as empirical treatment until receipt of the antibiogram was associated with a better rate of survival at 30 days than the use of monotherapy. However, adequate combination antimicrobial therapy given as definitive treatment for P. aeruginosa bacteremia did not improve the rate of survival compared to that from the provision of adequate definitive monotherapy.

Aged↗
PubMed1987

Plasmids of Ewingella americana: supplementary epidemiologic markers in an outbreak of pseudobacteremia.

During an outbreak of pseudobacteremia in a children's hospital, Ewingella americana was found in blood cultures from 20 patients. E. americana was inoculated into blood culture bottles at the time of specimen collection due to cross contamination from nonsterile, citrated blood collection tubes used for coagulation studies. Antimicrobial susceptibility testing and plasmid profiling were used to assess the association between patient isolates and isolates from unused blood collection tubes. All E. americana isolates had similar antibiograms (i.e., resistance only to cephalothin) when tested at 37 degrees C. However, when the same isolates were tested for antimicrobial susceptibility at 25 degrees C, a different antibiogram (i.e., resistance to chloramphenicol, ampicillin, and cephalothin) was found. The majority of these isolates also demonstrated a unique four-plasmid profile (130, 56, 4.6, and 3.1 megadaltons), and two of these plasmids (130 and 56 megadaltons) were characterized as temperature-sensitive plasmids. An epidemiologic link between outbreak-associated isolates obtained from different time periods in the outbreak was supported by evidence of a significant trend in the ability of the outbreak-associated isolates to reduce nitrate, together with the presence of the resistance antibiogram at 25 degrees C and the demonstration of the unique four-plasmid profile.

Adolescent↗
PubMed1992

Latex agglutination-negative methicillin-resistant Staphylococcus aureus recovered from neonates: epidemiologic features and comparison of typing methods.

An unusual strain of methicillin-resistant Staphylococcus aureus (MRSA) was repeatedly isolated from infants in a newborn special care unit (NBSC) and a newborn intensive care unit. Between January 1989 and March 1990, approximately 100 isolates from infected or colonized infants were recovered. Surveillance cultures taken during this time revealed a 20% colonization rate, which was defined as recovery of MRSA from the nares, umbilicus, or groin. Isolates were identified as S. aureus by tube coagulase reactivity and heat-stable nuclease production but were unreactive in a latex agglutination assay. Representative isolates that were collected during the outbreak and that were found to share the latex agglutination assay-negative phenotype were compared by antibiogram (12 isolates), bacteriophage typing (20 isolates), capsular polysaccharide typing (30 isolates), and plasmid as well as chromosomal DNA analyses (20 isolates). All isolates known to be associated with the outbreak had nearly identical antibiograms and were notably susceptible to clindamycin. Staphylococcal bacteriophage typing was not useful in determining the relatedness of the isolates, since the majority were nontypeable. Plasmid pattern analysis revealed one large plasmid (approximately 100 kb) of equivalent size among the isolates. Capsular polysaccharide typing revealed that 14 of 30 isolates tested were type 5. Isolates identified in children at two other hospitals in the city which were also unreactive by the latex agglutination assay and clindamycin susceptible had plasmid and antibiogram patterns identical to those of isolates from the NBSC. Pulsed-field gel electrophoresis of restriction enzyme-digested genomic DNAs from the outbreak isolates demonstrated identical patterns which could be clearly differentiated from those of other unrelated MRSA. The strain from the NBSC is, therefore, unique and underscores the need for caution in interpreting the latex agglutination reactivities of MRSA isolates.

Bacterial Typing Techniques↗
PubMed2002

Direct sensitivity test of the MB/BacT system.

In order to evaluate the direct-method test of sensitivity to drugs used in the principal tuberculosis treatment regimes, in the Organon Teknika MB/BacT system, we tested 50 sputum samples positive to microscopy taken from patients with pulmonary tuberculosis and with clinical indications for an antibiogram, admitted sequentially for examination during the routine of the reference laboratory. The material was treated v/v with 23% trisodium phosphate solution, incubated for 24 h at 35 degrees C, and neutralized v/v with 20% monosodium phosphate solution. The material was then centrifuged and the sediment inoculated into flasks containing Rifampin - 2 micro g/ml, Isoniazid - 0.2 micro g/ml, Pyrazinamide - 100 micro g/ml, Ethambutol - 2.5 micro g/ml, Ethionamide - 1.25 micro g/ml, and Streptomycin - 2 micro g/ml. The tests were evaluated using the indirect method in the BACTEC 460 TB (Becton Dickinson) system as the gold standard. The results showed that the Rifampin test performed best, i.e., 100% sensitivity at 95% Confidence Interval (82.2-100) and 100% specificity at 95% Confidence Interval (84.5-100), followed by Isoniazid and Pyrazinamide. In this experiment, 92% of the materials showed a final reading in 30 days; this period represents the time for primary isolation as well as the results of the sensitivity profile, and is within Centers for Disease Control and Prevention recommendations regarding time for performance of the antibiogram. The inoculated flasks showed no contamination during the experiment. The MB/BacT is shown to be a reliable, rapid, fully automated nonradiometric system for the tuberculosis antibiogram.

Antitubercular Agents↗
PubMedDate not supplied

Antibiotic sensitivity profiles do not reliably distinguish relapsing or persisting infections from reinfections in cats with chronic renal failure and multiple diagnoses of Escherichia coli urinary tract infection.

Older cats with chronic renal failure (CRF) commonly develop urinary tract infections (UTI). Uropathogenic Escherichia coli (UPEC) is identified as the causal agent of UTI in most affected cats. Infections are often complicated, and UPEC infections may persist or recur in these cats. Antibiotic sensitivity profiles have been used to distinguish relapsing or persisting UTI from reinfection by different clones of the same species. However, the accuracy with which antibiograms discriminate different urinary E coli clones in cats is uncertain. We studied 17 cystocentesis-derived UPEC isolates collected from 5 cats with stable CRF and multiple diagnoses of UTI. UTIs were classified as relapses versus persistent infections or reinfections using antibiograms determined by Kirby-Bauer discs and Etests. Subsequently, clonality of UPEC isolates was determined by pulsed-field gel electrophoresis (PFGE). A comparison of PFGE results with antibiograms indicated that antibiotic resistance patterns varied considerably within several individual E coli clones. Both antibiotic susceptibility tests differentiated between relapsing or persistent infections and reinfections with only 58% overall efficiency. Thus, antibiotic sensitivity profiles cannot be relied upon to distinguish between persisting or relapsing infections as compared to reinfections in cats with CRF and multiple diagnoses of E coli UTI.

Animals↗
PubMedDate not supplied

[Bacteriological examination of the sputum in support of a rational antibiotic therapy of bronchopulmonary infections].

An algorhythm of bacteriological investigation of the sputum is suggested for the etiological diagnosis of acute bronchopulmonary infections with pathogenically-conditioned bacteria. This investigation avoids misleading results, and provides, in a minimal time interval, both the first empiric criteria for the application of antibiotherapy--a definition of the microscopy category of the infecting pathogenically-conditioned bacteria--, and the second one, namely the antibiogram of the primary culture. This algorhythm is based on: decontamination of the sample by repeated washings; microscopical screening of the sample's quality, according to the ratio between inflammatory cells, squamous epithelial cells and the fibrin exudate; the qualitative bacterioscopic examination; the semi-quantitative culture of the sputum with the antibiogram on the primary culture; identification of infecting pathogenically-conditioned bacteria by confrontation of the microscopic significant amounts; inflammatory cells on the smear prepared directly from the sputum; the antibiogram on sub-cultures of the infecting, pathogenically-conditioned bacteria. Of high significance for the etiologic implication is the association of the inflammatory cells in quantities equal or greater than 13 organisms per microscopic field of pneumoncocoid bacteria, equal or greater than 20 organisms per microscopic field of the haemophilloid germs (with a significance threshold of 5%), and equal or greater than 18 organisms per microscopic field of neisseroid germs (at a significance threshold of 0.27%).

Anti-Bacterial Agents↗
PubMed1980

[Epidemiological studies of increasing appearances of Proteus inconstans (Providencia stuartii) infections (author's transl)].

Since proteus inconstans turns out to be the causative agent of an increasing amount of hospital infections, studies on this species are necessary. By means of bacteriocines, biochemical reactions and antibiograms 53 strains were subclassified. 47 strains displayed same biochemical properties, 44 strains showed the same antibiogram. By the method on the basis of bacteriocine typing 15 groups were established. The strains with the same biochemical properties and the same antibiograms could be further subclassified. The distribution of the different bacteriocine groups showed that the infections were not due to a single strain. In contrast there were some indices for cross-infections on some stations.

Anti-Bacterial Agents↗
PubMed1994

Identification of coagulase-negative staphylococci and typing of Staphylococcus epidermidis by a 4 h micromethod.

A new 4 h micromethod (Minibact-S) for identification of coagulase-negative staphylococci (CNS) important in human medicine, Staphylococcus epidermidis, Staphylococcus hominis, Staphylococcus haemolyticus and Staphylococcus saprophyticus, has been investigated. The reproducibility for species identification was 100% and the reproducibility for the single reactions was 95%. When compared to a modified Kloos & Schleifer conventional identification method, discrepant identification was obtained with the Minibact-S in only 8 of 382 clinical and reference strains. The system has been used for typing and biotyping of 201 S. epidermidis strains, and gave a subdivision in 69 different types; 4 related types accounted for 91 (45%) of the isolates, whereas 44 types were represented by only 1 isolate. The discriminatory index was 0.82. In a comparison with other typing methods performed on 81 isolates from 15 patients Minibact-S gave about the same number of types as antibiograms, but in 20% of the patients extra types were obtained with Minibact-S alone compared to antibiogram alone and vice versa. The Minibact-S is of some value in the routine clinical microbiology laboratory as a first screening method for identification of coagulase-negative staphylococci and typing of S. epidermidis in combination with the antibiogram.

Coagulase↗
PubMed1998

The changing patterns of antimicrobial susceptibility of urinary pathogens in Trinidad.

OBJECTIVE: The prevalence of antimicrobial resistance in urinary pathogens is increasing worldwide. Accurate bacteriologic records of culture results may provide guidance on empirical therapy before sensitivity patterns are available. We report the changing antibiograms of pathogens associated with urinary tract infections (UTI) over a 4-year period at a newly commissioned hospital complex diagnostic laboratory in Trinidad. METHODS: From January 1992 to December 1995, kept records of antibiograms of all urinary pathogens isolated were examined. Samples were derived from hospital sources (wards and out-patient clinics) and general practice sources (health centers and general practitioners). Quantitative bacteriologic cultures were performed according to standard laboratory procedures, and identification of isolates were based on Gram reaction, morphology and biochemical characteristics. Significant bacteriuria was defined as the presence of greater than 100,000 organisms per mL of a midstream urine specimen or more than 3000 bacteria per mL in a catheter specimen of a single specie. Antimicrobial sensitivities were done using the following antibiotics: norfloxacin, ampicillin, tetracycline, nitrofurantoin, gentamicin, co-trimoxazole (sulfamethoxazole-trimethoprim), trimethoprim, nalidixic acid, cephalexin and augmentin (amoxicillin-clavulanic acid). Control organism was E coli NCTC 10,418 strain. RESULTS: The total number of specimens for the 4-year period in hospital was 14,181 with an isolation rate of 17%, and a general practice isolation rate of 67% from a total of 5,088 specimens. E coli was the most frequent isolate in both hospital (40%) and general practice (30%). There was an increase isolation of P aeruginosa from community practice reflecting an increase in home care catheterised male patients. Resistance to tetracycline was most significant in hospital (99%) and general practice (81%). Similar trend was observed for trimethoprim in hospital, and co-trimoxazole in both practices. Resistance to ampicillin, augmentin and cephalexin was relatively stable over the 4-year period. CONCLUSION: We conclude that laboratories should encourage accurate bacteriologic record keeping of urinary isolates and their antibiograms to serve as guidance in empirical treatment in UTI. Also, urine microscopy may reduce the number of specimens sent for culture which are not cost-effective.

Anti-Bacterial Agents↗
PubMed1997

Molecular typing of Acinetobacter baumannii from ten different intensive care units of a university hospital.

Thirty-one isolates of Acinetobacter baumannii were collected from ten intensive care units of an Austrian university hospital. All isolates were typed by enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR). Two strains colonizing 13 infants in the neonatal intensive care unit were identified by ERIC-PCR. All other Acinetobacter baumannii isolates had highly divergent ERIC-PCR patterns, despite having the same antibiogram. Thus, a hospital-wide clonal distribution, as suggested by identical antibiogram patterns, was excluded by ERIC-PCR.

Acinetobacter↗
PubMed1984

Hospital personnel with penicillin-resistant Streptococcus viridans. A case for special consideration in the prevention of bacterial endocarditis.

Penicillin is the drug of choice for the prevention of bacterial endocarditis (BE) resulting from dental treatment. The susceptibility of Streptococcus viridans to this antimicrobial agent was studied. A representative sample of hospital personnel (N = 76) was compared to a control group of seventy-six subjects who were not associated with the hospital. Twenty-four of the hospital personnel worked in wards that consume 0.13 to 1.64 (mean +/- SD = 0.88 +/- 0.64) gm penicillin per day per position (low consumption group = LCG) and fifty-two worked in wards that consume 2.27 to 3.67 (mean +/- SD = 3.04 +/- 0.55) gm penicillin per day per position (high consumption group = HCG). Antibiograms of oral isolates showed that, while 48.08% of the subjects from the HCG revealed penicillin-resistant S. viridans only 8.33% of the subjects from the LCG and 7.89% of the control group presented such results. The data presented suggest that there are subjects who may unknowingly carry penicillin-resistant S. viridans as part of their oral flora. It is therefore recommended that the preferable antibiotic used for the prevention of BE should be determined by an antibiogram.

Carrier State↗
PubMed1988

A study of the value of electrophoretic and other techniques for typing Acinetobacter calcoaceticus.

Forty-four isolates of Acinetobacter calcoaceticus var anitratus collected during hospital outbreaks were studied using polyacrylamide gel electrophoresis (PAGE), plasmid analysis, antibiograms and biochemical tests to determine their degree of similarity. Reproducibility tests were also carried out on the PAGE and biochemical techniques to determine their validity when used to compare bacteria of the same type isolated intermittently. PAGE data was analysed densitometrically and isolates compared using a similarity matrix. All methods were able to subdivide the isolates, but results did not always correlate well between methods. Reproducibility data indicated that careful attention to technique is required when organisms are examined by PAGE sequentially. Results suggest that no single biotyping technique is likely to be adequate and that electrophoretic, biochemical and antibiogram data may complement one another and other epidemiological data in the typing of these organisms.

Acinetobacter↗
PubMed1991

Evolution of Staphylococcus aureus resistance to erythromycin in Denmark, 1959 to 1988: correlations between characteristics of erythromycin-resistant bacteraemia strains.

In an attempt to characterize erythromycin-resistant Staphylococcus aureus we present the intricate relationships between the following factors: phage type, period of isolation, antibiogram, minimum inhibitory concentration (MIC) to erythromycin, inducible or constitutive resistance, spectinomycin susceptibility, hospital- or community-acquired infection, and mortality rate. We studied 718 cases of bacteraemia with erythromycin-resistant S. aureus, occurring between 1959 and 1988. Central factors were phage type pattern, period of isolation, and antibiogram. Between 1959 and 1973 the majority of the erythromycin-resistant strains were multiresistant and belonged to the 83A complex and the related group III. They were mainly inducibly resistant, spectinomycin resistant, and had intermediate MICs (1-4 mg l-1) to erythromycin. The majority of these strains came from hospital-acquired infections and still exist today, although in decreased numbers. By contrast, erythromycin-resistant S. aureus isolated in recent years are usually co-resistant only to penicillin and more rarely also to tetracycline. These strains have inducible resistance, are spectinomycin susceptible, and have a high erythromycin MIC. They are isolated both from hospital- and community-acquired infections. Strains with constitutive resistance to macrolides occurred at a stable low level (13%) during the whole observation period and always had high MICs to erythromycin. The mortality rate among patients with S. aureus bacteraemia due to an erythromycin-resistant strain was only associated with the year of infection and decreased from 61% in the first 15-year period to 40% in the subsequent 15 years.

Bacteriophage Typing↗
PubMed1991

Recurrent CAPD peritonitis caused by coagulase-negative staphylococci: re-infection or relapse determined by clinical criteria and typing methods.

Four hundred consecutive episodes of continuous ambulatory peritoneal dialysis (CAPD)-associated peritonitis in 105 patients were analysed. Of these episodes 161 (40.25%) were caused by coagulase-negative staphylococci (CNS). Thirty-seven patients developed recurrent attacks (3-10) of peritonitis and CNS accounted for 72 (60%) of these episodes. Classification of reinfection or relapse in 67 of these recurrent episodes of peritonitis was based on clinical criteria alone. This was compared with the results of three typing methods of CNS strains: biotyping plus antibiograms, immunoblotting and 35S-methionine-labelled protein patterns (radio-PAGE). Radio-PAGE was the most discriminatory method followed by biotyping with antibiograms and then immunoblotting. There was total agreement between clinical diagnosis and the three typing methods in 67.2% of episodes but there was total disagreement between the clinical diagnosis and the three typing methods in 11.9%, suggesting inaccurate clinical diagnosis, and in 20.8% typing by at least one method differed from the clinical criteria. Thus, clinical criteria alone are inadequate for the accurate distinction of reinfection from relapse in recurrent CNS peritonitis. This distinction is desirable for optimal management and accurate assessment of different therapies. We suggest that CNS strains from peritoneal dialysate are stored for future typing should the patient develop repeated episodes of peritonitis, to aid in the diagnosis and management of such patients.

Autoradiography↗
PubMed1991

Multiply antibiotic-resistant Staphylococcus epidermidis in patients, staff and environment--a one-week survey in a bone marrow transplant unit.

The distribution of Staphylococcus epidermidis resistant to ciprofloxacin and/or gentamicin was studied in an isolation unit for patients undergoing bone marrow transplantation. During 1 week all such strains colonizing patients or staff members or found on the clothes of staff or in the air were investigated. Antibiograms and plasmid profiles were used for epidemiological typing. Thirty-one different antibiograms were found. A few strains were widely spread and dominated quantitatively. Staff colonization was 23%, but contamination of their clothes was 82%. Two strains which colonized three of the patients were widely spread in the air. They were found in the corridor and in every patient room, even where the patient was not colonized. The main source of the environmental contamination seems to have been patients. Possible routes of infection were direct airborne transmission as well as passive transfer via staff.

Bone Marrow Transplantation↗