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PubMed1996

Detection of extended-spectrum beta-lactamase (ESBL)-producing strains by the Etest ESBL screen.

Resistance to contemporary broad-spectrum beta-lactams, mediated by extended-spectrum beta-lactamase (ESBL) enzymes, is an increasing problem worldwide. The Etest (AB Biodisk, Solna, Sweden) ESBL screen uses stable gradient technology to evaluate the MIC of ceftazidime alone compared with the MIC of ceftazidime with clavulanic acid (2 micrograms/ml) to facilitate the recognition of strains expressing inhibitable enzymes. In the present study, ESBL-producing strains (17 Escherichia coli transconjugants) were studied to define "sensitive" interpretive criteria for the Etest ESBL screen. These criteria (reduction of the ceftazidime MIC by > 2 log2 dilution steps in the presence of clavulanic acid) defined a group of 92 probable ESBL-positive organisms among the 225 tested strains of Klebsiella species and E. coli having suspicious antibiogram phenotypes. With a subset of 82 clinical strains, the Etest ESBL screen was more sensitive (100%) than the disk approximation test (87%) and was more convenient. The MICs of ciprofloxacin, gentamicin, and tobramycin at which 50% of isolates are inhibited were 16- to 128-fold higher (coresistance) for the ESBL screen-positive group of strains than for the ESBL screen-negative group of strains. Some strains for which cephalosporin MICs were elevated and which were Etest ESBL screen negative were also cefoxitin resistant, i.e., consistent with a chromosomally mediated AmpC resistance phenotype. The Etest ESBL screen test with the ceftazidime substrate appears to be a useful method for detecting or validating the presence of enteric bacilli potentially producing this type of beta-lactamase.

Anti-Bacterial Agents↗
PubMed1996

Patient-to-patient spread of a single strain of Corynebacterium striatum causing infections in a surgical intensive care unit.

Over a 12-month period, Corynebacterium striatum strains were isolated from clinical specimens from 14 patients admitted to a surgical intensive care unit. These isolates were identical by morphology and biotype and displayed the same antibiogram. Ten isolates were found to be the sole possible pathogen. These 10 isolates were from six patients, three of whom had signs of infection at the time of positive culture. Further typing was performed by random amplification of polymorphic DNA analysis, by which all strains were identical and were found to differ to various degrees from reference strains and from isolates found in clinical samples from other wards. In a case-control study the only independent risk factor for acquiring the strain was intubation for longer than 24 h (odds ratio, 20.09; 95% confidence interval, 2.29 to 176.09). The same strain was isolated from surfaces and from air sampled in the direct vicinity of infected patients but never from surfaces or air in other places of the ward. The strain was not isolated from the ventilators. The strain was cultured from the hands of personnel attending to infected patients, but no long-term carriers were found among members of the hospital personnel, suggesting transient carriage only. We conclude that C. striatum can cause serious nosocomial infections in surgical intensive care unit patients and may spread from patient to patient via the hands of attending personnel.

Corynebacterium↗
PubMed1997

Emergence of a unique O3:K6 clone of Vibrio parahaemolyticus in Calcutta, India, and isolation of strains from the same clonal group from Southeast Asian travelers arriving in Japan.

Active surveillance of Vibrio parahaemolyticus infection among hospitalized patients in Calcutta, India, was initiated in January 1994. The incidence of cases of V. parahaemolyticus infection suddenly increased in February 1996 and has remained high since then. One hundred thirty-four strains of V. parahaemolyticus isolated from January 1994 to August 1996 were examined for serovar, the presence of the thermostable direct hemolysin gene (tdh) and tdh-related hemolysin genes (trh1 and trh2), production of urease, and antibiogram. Strains of the O3:K6 serovar appeared for the first time in February 1996. The O3:K6 serovar strains accounted for 50 to 80% of the strains isolated during the high-incidence period (February to August 1996). All of the serovar O3:K6 strains carried the tdh gene but not the trh genes and did not produce urease. All of the isolates except two were sensitive to all of the antibiotics tested. These and the results of analysis by an arbitrarily primed PCR method indicated that the O3:K6 serovar strains belong to a unique clone. When the O3:K6 serovar strains, isolated from travelers arriving in Japan from Southeast Asian countries, were compared by the arbitrarily primed PCR method, the strains isolated between 1982 and 1993 were distinct from Calcutta O3:K6 while the strains isolated in 1995 and 1996 were indistinguishable from the Calcutta O3:K6 strains. The results suggest that this unique O3:K6 clone may have become prevalent not only in Calcutta but also in Southeast Asian countries very recently. Not only the O3:K6 strains but also the non-O3:K6, tdh-bearing strains isolated in 1996 produced thermostable direct hemolysin at high levels, and thus the level of hemolysin produced does not appear to have influenced the high incidence of serovar O3:K6 strains.

Asia, Southeastern↗
PubMed1997

Outbreak of Shigella sonnei in a clinical microbiology laboratory.

Laboratory technologists (22%) developed infections with Shigella sonnei. The isolates had the same antibiogram and pulse-field gel electrophoresis pattern as an unknown isolate handled by a laboratory student. Covering faucet handles with paper towels during hand washing in the laboratory was protective. No further cases occurred after the laboratory was cleaned with a phenolic agent and a handle-free faucet was installed.

DNA, Bacterial↗
PubMed1997

Indwelling device-related bacteremia caused by serum-susceptible Campylobacter coli.

Two isolates of serum-susceptible Campylobacter coli were recovered in a 7-day interval from blood from a patient with hepatocellular carcinoma and liver cirrhosis whose peritoneal-caval (Denver's) shunt malfunctioned. Identical random amplified polymorphic DNA fingerprints, cellular fatty acid chromatograms, and antibiograms of the two isolates indicate that C. coli has the ability to cause catheter-related bacteremia following its colonization of the catheter.

Bacteremia↗
PubMed1997

Comparison of screening methods for detection of extended-spectrum beta-lactamases and their prevalence among blood isolates of Escherichia coli and Klebsiella spp. in a Belgian teaching hospital.

Using a set of 33 well-defined extended-spectrum beta-lactamase (ESBL)-producing strains of Escherichia coli and Klebsiella pneumoniae, we compared three screening methods for ESBL detection: (i) a double-disk synergy test, (ii) a three-dimensional test (both the double-disk synergy test and the three-dimensional test were performed with ceftriaxone, ceftazidime, aztreonam, and cefepime), and (iii) the Etest ESBL screen (AB Biodisk, Solna, Sweden), based on the recognition of a reduction in the ceftazidime MIC in the presence of clavulanic acid. In the double-disk test, all four indicator antibiotics scored equally and 31 of the 33 reference strains were recognized. In the three-dimensional test, ceftriaxone was the only satisfactory indicator and 30 ESBL-positive strains were detected by this antibiotic. Both systems produced two false-positive results with cefepime. With the Etest ESBL screen, 15 of 16 TEM-related and 11 of 16 SHV-related ESBL-producing strains scored positive. In 10 cases the clavulanic acid on one end of the strip interfered with the MIC determination for ceftazidime, which was read on the opposite end. This MIC had to be determined with an extra ceftazidime-only strip. No false-positive results were noted. Eighty-six blood isolates of E. coli and Klebsiella species were screened for ESBL expression by the double-disk and three-dimensional tests, both with ceftriaxone. Six strains with suspicious antibiogram phenotypes also gave positive results by the double-disk test. One E. coli strain remained undetected by the three-dimensional test. Identification of the enzymes suspected of being ESBLs by isoelectric focusing (all strains) and DNA sequencing (1 strain) confirmed the screening test results except for one Klebsiella oxytoca strain, which proved to be a hyperproducer of its chromosomal enzyme and which also had a negative Etest score. The five true ESBL producers were all confirmed by the Etest ESBL screen. Pulsed-field gel electrophoresis proved that the E. coli strains were unrelated, but that two of the three K. pneumoniae strains were closely related.

Aztreonam↗
PubMed1997

Recognition of a Nocardia transvalensis complex by resistance to aminoglycosides, including amikacin, and PCR-restriction fragment length polymorphism analysis.

Amikacin resistance, rare among nocardiae, was observed in 58 clinical isolates of nocardiae. All of these isolates hydrolyzed hypoxanthine, and 75 to 100% utilized citrate, D-galactose, and D-trehalose as sole carbon sources. Based on utilization of I-erythritol, D-glucitol, i-myo-inositol, D-mannitol, and ribitol and susceptibility to amoxicillin-clavulanic acid, the 58 isolates were separable into four groups. One group was negative for I-erythritol and ribitol and included all the isolates belonging to Nocardia asteroides complex antibiogram type IV. The remaining three groups were positive for I-erythritol and ribitol and were grouped within Nocardia transvalensis. The group that included the type strain was designated N. transvalensis sensu stricto, and the other two groups were designated new taxons 1 and 2. PCR-restriction fragment length polymorphism (RFLP) analysis of a 439-bp segment of the 65-kDa heat shock protein gene with XhoI and HinfI produced identical patterns for 53 (91%) and 58 (100%) isolates, respectively, and differentiated them from all other Nocardia taxa. NarI- and HaeIII-derived RFLP patterns clearly differentiated each of the four biochemically defined taxa. These four groups were also distinguishable by using the chromogenic substrates in Dade MicroScan test panels. By high-performance liquid chromatography, these isolates exhibited the same unique mycolic acid-ester elution patterns that differed from those of all other clinically significant nocardiae. Gas-liquid chromatographic analysis of fatty acids also produced similar patterns for all isolates that distinguished them from all other Nocardia taxa, but did not differentiate the four taxa within the complex. We propose the designation N. transvalensis complex for these four groups of nocardiae, pending further genetic evaluation.

Amikacin↗
PubMed1998

Genetic relationship between blood and nonblood isolates from bacteremic patients determined by pulsed-field gel electrophoresis.

A total of 148 isolates from 55 bacteremic patients were examined by pulsed-field gel electrophoresis. Genetically different nonblood strains were isolated from 13.9% of patients with bacteremia caused by gram-positive cocci and 42.1% with Pseudomonas aeruginosa bacteremia, indicating that antibiograms of a single nonblood P. aeruginosa isolate are not always informative for treatment of bacteremia.

Bacteremia↗
PubMed1999

Antimicrobial susceptibility patterns of Aeromonas jandaei, A. schubertii, A. trota, and A. veronii biotype veronii.

Fifty-six isolates of four Aeromonas species, which have been documented as causative agents of human infections or isolated from human clinical specimens, were subjected to antimicrobial susceptibility testing using a MicroScan WalkAway conventional (overnight incubation) gram-negative panel. The four species tested and the number of isolates of each were as follows: Aeromonas jandaei, 17; A. schubertii, 12; A. trota, 15; and A. veronii biotype veronii, 12. All isolates of A. trota were susceptible to all antimicrobial agents tested, except cefazolin (20% of isolates were resistant) and cefoxitin (13% of isolates were resistant). All isolates of A. schubertii and A. veronii biotype veronii, as well as 88% of A. jandaei isolates, were resistant to ampicillin. Resistance to ampicillin-sulbactam ranged from 25% of A. schubertii strains to 100% of A. veronii biotype veronii strains. Cefazolin resistance ranged from 17% of A. veronii biotype veronii isolates to 59% of A. jandaei isolates. Imipenem resistance was detected in 65% of A. jandaei strains and 67% of A. veronii biotype veronii strains. A. jandaei displayed resistance to piperacillin and ticarcillin in 53 and 71% of the isolates, respectively. A. veronii biotype veronii strains were 100% susceptible to piperacillin and 100% resistant to ticarcillin. These antibiogram data may be useful in establishing the identification of these four species when members of the genus Aeromonas are isolated from human clinical sources.

Aeromonas↗
PubMed1999

DNA banding pattern polymorphism in vancomycin-resistant Enterococcus faecium and criteria for defining strains.

The degree of DNA banding pattern polymorphism exhibited by vancomycin-resistant Enterococcus faecium (VREM) strains isolated on a renal unit over an 11-month period was investigated. Thirty VREM strains from different patients were analyzed by pulsed-field gel electrophoresis (PFGE; with extended run and optimal pulse times), ribotyping, plasmid profile analysis, biotyping, pyrolysis mass spectrometry, and antibiogram analysis. PFGE resolved 17 banding patterns which formed four distinct clusters at the 82% similarity level. Intercluster band differences ranged from 14 to 31 bands. The strains in one cluster, which contained seven patterns that differed from each other by one to seven bands and from the common pattern by five bands, were confirmed to be a single strain by four of the five other typing methods. The strains in a second cluster with eight patterns, which differed from each other by 1 to 12 bands, contained two subclusters. This subdivision was supported by ribotyping and biotyping. However, it was unclear whether these subclusters represented distinct strains. In one strain, marked polymorphism (patterns that differed from each other by up to four bands) was observed in the ribotype pattern. This study demonstrates the high degree of DNA banding pattern polymorphism found for some strains of VREM and illustrates the complexity involved in defining such strains.

Anti-Bacterial Agents↗
PubMed1999

Methicillin-resistant Staphylococcus aureus outbreak in a veterinary teaching hospital: potential human-to-animal transmission.

During a 13-month period, 11 equine patients visiting a veterinary teaching hospital for various diagnostic and surgical procedures developed postprocedural infections from which methicillin (oxacillin)-resistant Staphylococcus aureus (MRSA) strains were isolated. The S. aureus isolates were identified by conventional methods that included Gram staining, tests for colonial morphology, tests for clumping factor, and tests for coagulase and urease activities and were also tested with the API STAPH IDENT system. Antimicrobial susceptibility tests were performed by the disk diffusion method. The biochemical profile and antibiogram of each isolate suggested that the isolates may have come from a common source. Because MRSA strains are very uncommon animal isolates but are rather common human isolates, a nasal swab specimen for culture was collected voluntarily from five persons associated with equine surgery and recovery in an attempt to identify a possible source of the organisms. MRSA strains were isolated from three of the five people, with one person found to be colonized with two biotypes of MRSA. The MRSA isolates from the people appeared to be identical to the isolates from horses. Further study of the isolates included SmaI and EagI macrorestriction analysis by pulsed-field gel electrophoresis conducted in two different laboratories. The results indicated that both the equine and human isolates were members of a very closely related group which appear to have originated from a common source. On the basis of the pattern associated with the infection, it is speculated that the members of the Veterinary Teaching Hospital staff were the primary source of the infection, although the specific mode of transmission is unclear.

Animals↗
PubMed1999

Susceptibility testing of anaerobic bacteria: evaluation of the redesigned (Version 96) bioMérieux ATB ANA device.

We compared the susceptibility results for 200 clinical anaerobes with nine antibiotics obtained by using a new ATB ANA (bioMérieux) device against those obtained by the National Committee for Clinical Laboratory Standards (NCCLS) standard agar dilution method. For better evaluation of the device, we added some resistant Bacteroides fragilis group strains from our own collection: 3, 6, and 12 strains that were resistant to imipenem, ticarcillin plus clavulanic acid, and co-amoxiclav, respectively, and 2 other strains with decreased susceptibility to metronidazole. For some strains that did not grow on ATB S medium, tests were performed by using West-Wilkins medium supplemented with 1.5% agar. The new ATB ANA device made clinical categorization of the investigated strains possible, according to French (Committee of the Antibiogram of the French Society of Microbiology) or U.S. (NCCLS) breakpoints, with the following respective results: category agreement, 94.3 and 94.9%; minor errors, 4.8 and 3.8%; major errors, 0.4 and 0.8%; and very major errors 4.6 and 4.2%. The ATB ANA device was able to detect low-level metronidazole-resistant B. fragilis strains according to the French breakpoints but not the NCCLS ones. For B. fragilis and beta-lactamase-positive Prevotella strains, the clustering effect of amoxicillin MICs around the French breakpoints led to more frequent minor errors. ATB ANA is a very convenient method to determine the antibiotic susceptibilities of anaerobes. Results obtained by ATB ANA correlated well with those obtained by the reference method.

Anti-Bacterial Agents↗
PubMed1999

Epidemiological study of an Acinetobacter baumannii outbreak by using a combination of antibiotyping and ribotyping.

From June to November 1994 (period 1) and from February to June 1995 (period 2), multiresistant Acinetobacter baumannii strains were isolated in intensive care units and surgical wards of the Amiens Teaching Hospital Center (Amiens, France). Eighteen isolates were obtained from 17 (1%) of 1,706 patients admitted during both of these periods, giving an incidence rate of nosocomial infection per 1,000 patient days of 0.6%. Of 17 infected patients, 9 had pneumonia, 3 had urinary tract infection, 2 had peritonitis, 1 had septicemia, 1 had a catheter infection, and 1 had pneumonia and urinary tract infection. According to typing results, four antibiotic resistance profiles were detected: a, b, c, and d; seven ribotypes were distinguished by both restriction enzymes EcoRI and SalI (A, B, C, D, E, F, and G). By combining antibiotyping and ribotyping, we obtained eight groups of strains (groups I to VIII). Group I contained five strains (strains 4, 5, 7, 8, and 9) which had antibiogram pattern a and ribopattern A and constituted the outbreak strains. The strains of group II (strains 3, 10, 11, 13, and 14) were closely related to outbreak strain A and appeared to be variants of ribotype A (A2 [strain 3]; A4 [strain 10]; A5 [strains 11, 13, and 14]). Groups III, IV, V, VI, VII, and VIII included strains which were epidemiologically unrelated to the strains of group I and were considered nonoutbreak strains.

Acinetobacter↗
PubMed1999

Evidence of clonal dissemination of multidrug-resistant Streptococcus pneumoniae in Hong Kong.

The relationship between the phenotypic and genotypic characteristics of 105 penicillin-intermediate or -resistant Streptococcus pneumoniae isolates saved during 1994 to 1997 at the Prince of Wales Hospital and Pamela Youde Nethersole Eastern Hospital, Hong Kong, was studied. The pbp genes for penicillin-binding proteins 1a, 2b, and 2x for each isolate were amplified by PCR, and the products were digested with restriction enzymes HinfI and AluI. A combination of the pulsed-field gel electrophoresis (PFGE) profiles, pbp fingerprints, and phenotypic characteristics of capsular types and antibiograms enabled these isolates to be divided into four major groups. Seventy-four percent (78 of 105) of the strains, belonging to serotypes 23F, 19F, and 14, showed indistinguishable pbp fingerprint patterns (group A1, 1-1-1, 1-1-1), with PFGE patterns belonging to group A and its subtypes, suggesting that these strains were closely related. Eighty-three percent (65 of 78) of these isolates were also resistant to tetracycline, erythromycin, chloramphenicol, and trimethoprim. The type 23F isolates were indistinguishable from representative strains of the Spanish 23F clone by these molecular methods, indicating that these strains may be variants of the Spanish 23F clone. Serotype 6B accounted for 19% (20 of 105) of the isolates with reduced penicillin susceptibility and was made up of variants belonging to four different pbp fingerprint groups with the PFGE pattern group B, the predominant group being indistinguishable from that of the Spanish 6B clone. Other PFGE and fingerprint groups were mainly obtained from penicillin-susceptible strains of various serotypes. The results suggest that the rapid emergence of drug-resistant S. pneumoniae in Hong Kong has been due to the rapid dissemination of several successful clones.

Bacterial Capsules↗
PubMed2000

Phenotypic and molecular typing of nosocomial methicillin-resistant Staphylococcus aureus strains susceptible to gentamicin isolated in france from 1995 to 1997.

Methicillin-resistant strains susceptible to gentamicin (Gm(s) MRSA) have emerged since 1993 in several French hospitals. To study whether particular clones have spread in various French cities and whether some clones are related to gentamicin-resistant (Gm(r)) MRSA strains, various methods (antibiotyping, phage typing, determination of SmaI macrorestriction patterns before and after hybridization with IS256 transposase and aacA-aphD probes) were used to compare 62 Gm(s) MRSA strains isolated from 1995 to 1997 in nine cities and 15 Gm(r) MRSA strains. Eighteen major SmaI genotypes were identified, of which 11 included only Gm(s) MRSA strains and 5 included only Gm(r) MRSA strains. Each of the Gm(r) MRSA strains contained 6 to 13 SmaI fragments hybridizing with the insertion sequence IS256, of which a single band also hybridized with the aacA-aphD gene. No such hybridizing sequences were detected in 60 of the 62 Gm(s) MRSA strains. Thus, the divergence between Gm(r) and Gm(s) MRSA strains is revealed, not only by their distributions in distinct SmaI genotypes but also by the differences in hybridization patterns. Two of the 62 Gm(s) MRSA strains had the uncommon feature of carrying several SmaI bands hybridizing with IS256, suggesting that they are possibly related to the Gm(r) MRSA strains grouped in the same SmaI genotype. Five of the 11 SmaI genotypes including only Gm(s) MRSA strains contained strains from diverse cities, isolated during different years and with different antibiograms, suggesting that some clones have spread beyond their cities of origin and persisted.

Bacterial Typing Techniques↗
PubMed2000

Bacteremic pneumonia caused by a single clone of Streptococcus pneumoniae with different optochin susceptibilities.

Two isolates of Streptococcus pneumoniae having different optochin susceptibilities were recovered from a blood sample of a 2-year-old boy with community-acquired pneumonia. The two isolates were documented to belong to a single clone on the basis of the isolates' identical serotype (23F), antibiograms by the E-test, random amplified polymorphic DNA patterns generated by arbitrarily primed PCR, pulsed-field gel electrophoresis, and restriction fragment length polymorphism of the penicillin-binding protein genes pbp2b and pbp2x.

Bacteremia↗
PubMed2000

Outbreak of nosocomial infections due to extended-spectrum beta-lactamase-producing strains of enteric group 137, a new member of the family Enterobacteriaceae closely related to Citrobacter farmeri and Citrobacter amalonaticus.

A member of the Enterobacteriaceae initially identified as Kluyvera cryocrescens by the MicroScan Gram-Negative Combo 13 panel caused an outbreak of nosocomial infections in four patients (pneumonia, n = 2; urinary tract infection, n = 1; wound infection, n = 1) and urinary tract colonization in one patient. When the strains were tested by the Enteric Reference Laboratory of the Centers for Disease Control and Prevention, biochemical results were most compatible with Yersinia intermedia, Kluyvera cryocrescens, and Citrobacter farmeri but identification scores were low and test results were discrepant. However, when the biochemical test profile was placed in the computer database as a new organism, all strains were identified as the organism with high identification scores (0. 999968 to 0.999997) and no discrepant test results. By 16S rRNA sequence analysis the organism clustered most closely with, but was distinct from, Citrobacter farmeri and Citrobacter amalonaticus. Based on its unique biochemical profile and rRNA sequence, this organism is designated Enteric Group 137. Restriction endonuclease analysis and taxonomic antibiograms of strains causing the outbreak demonstrated a single clone of Enteric Group 137, and antibiotic susceptibility testing revealed the presence of extended-spectrum beta-lactamase (ESBL) resistance. Enteric Group 137 appears to be a new opportunistic pathogen that can serve as a source of ESBL resistance in the hospital.

Aged↗
PubMed2000

Emergence of Vibrio cholerae O1 biotype El Tor serotype Inaba from the prevailing O1 Ogawa serotype strains in India.

The toxigenic Inaba serotype of Vibrio cholerae O1 biotype El Tor reappeared in India in 1998 and 1999, almost 10 years after its last dominance in Calcutta in 1989. Extensive molecular characterization by ribotyping, restriction fragment length polymorphism, and pulsed-field gel electrophoresis indicated that recent Inaba strains are remarkably different from the earlier Inaba strains but are very similar to the prevailing V. cholerae O1 Ogawa El Tor biotype strains. The antibiograms of the Inaba strains were also similar to those of the recent V. cholerae Ogawa strains. These V. cholerae O1 Inaba strains appear to have evolved from the currently prevailing Ogawa strains and are likely to dominate in the coming years.

Anti-Bacterial Agents↗