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Clinical and epidemiological features of an outbreak of acinetobacter infection in an intensive therapy unit.

Sporadic examples of infection with multi-resistant Acinetobacter spp. have occurred in Nottingham hospitals since at least 1977, punctuated by more prolonged outbreaks involving larger numbers of patients, particularly those confined to the intensive therapy unit (ITU) with severe underlying disease. In the most recent outbreak, 11 patients were infected with multi-resistant Acinetobacter strains and 26 patients were colonised. Four of the infected patients died directly or indirectly from infection with multi-resistant Acinetobacter spp., either while in the ITU or after discharge to a general ward. The mean interval from admission to the first isolation of a multi-resistant Acinetobacter strain was 6.7 and 12.1 days in the infected and colonised groups, respectively. Multi-resistant Acinetobacter strains were isolated most frequently from the respiratory tract, and eight patients had probable or suspected pneumonia caused by a multi-resistant Acinetobacter sp. All infected patients were treated with imipenem, with or without an aminoglycoside, except one patient who died before a diagnosis of acinetobacter infection was confirmed. Multi-resistant Acinetobacter spp. were isolated from various environmental sites in the ITU, and patient and environmental isolates were found to be related closely by biotyping, antibiograms, pulsed-field gel electrophoresis of chromosomal fingerprints and ribotyping. The outbreak was controlled ultimately by transfer of infected or colonised patients to an isolation cubicle, cohort nursing, emphasis on the importance of hand washing before and after patient contact and when handling case notes, and the use of disposable aprons and gowns during patient contact.(ABSTRACT TRUNCATED AT 250 WORDS)

Acinetobacter↗

Resistance to extended-spectrum cephalosporins, caused by PER-1 beta-lactamase, in Salmonella typhimurium from Istanbul, Turkey.

Two Salmonella typhimurium isolates were studied, one as a representative from a series of neonatal meningitis cases treated at an Istanbul teaching hospital, the other from a gastro-enteritis case seen at a different Istanbul hospital. Both isolates were resistant to extended-spectrum cephalosporins, as well as penicillins, aminoglycosides and chloramphenicol. Cephalosporin resistance depended on production of PER-1 beta-lactamase, which is an extended-spectrum class A enzyme that is only distantly related to TEM and SHV enzymes, and which was previously known only from Pseudomonas aeruginosa isolates. The PER-1 gene was carried by an 81-MDa plasmid, which also determined resistance to aminoglycosides and chloramphenicol. Although it was not self-transmissible to Escherichia coli, this element did transfer if mobilised with plasmid pUZ8. The two S. typhimurium isolates gave indistinguishable DNA restriction patterns and, in addition to their 81-MDa plasmid, also contained 52- and 2.8-MDa plasmids, the last of these encoded TEM-1 enzyme. The two isolates were identical in serotype, antibiogram and plasmid-profile but nevertheless differed in phage type, and, therefore, represented distinct strains. The emergence of cefotaxime and ceftriaxone resistance in salmonellae is disturbing, since these agents are preferred therapy for neonatal meningitis caused by members of the genus.

Base Sequence↗

Comparison of rapid automated laser fluorescence analysis of DNA fingerprints with four other computer-assisted approaches for studying relationships between Acinetobacter baumannii isolates.

The relationships between isolates suggested by a novel DNA typing method (RAPD-ALFA) that combines randomly amplified polymorphic DNA with automated on-line laser fluorescence analysis of DNA fragments were compared with those suggested by four other computer-assisted typing strategies (biotyping, antibiogram typing, pulsed-field gel analysis of chromosomal fingerprints and arbitrarily-primed DNA amplification with three different primers) for 25 isolates of Acinetobacter baumannii obtained from 12 different hospitals in four countries over a period of 12 years. The results obtained by cluster analysis with two different software packages confirmed that the relationships suggested by RAPD-ALFA were robust and essentially similar to those suggested by the other more laborious computer-assisted typing methods. The technique of RAPD-ALFA appears to offer the possibility of routine on-line molecular identification and typing of isolates from particular hospital wards or units (e.g., intensive care units), and could, therefore, play a key role in the early recognition and prevention of outbreaks of infection.

Acinetobacter↗

Identification and antibiotic susceptibility of Nocardia farcinica and N. nova in the UK.

Nocardia asteroides has long been recognised as a heterogeneous group of organisms. The description and identification of two new subgroups, N. farcinica and N. nova, in other countries encouraged us to re-examine a collection of N. asteroides isolates from the UK. Of 73 clinical isolates identified as N. asteroides from different parts of England and Wales during 1991-1993, and now subjected to further differentiation tests by the Mycobacterial/Nocardial Reference Laboratory, 15 (20.5%) were identified as N. farcinica based on three out of four characteristics: growth property, acetamide production, rhamnose assimilation and a distinct antibiogram. No isolates were identified as N. nova. A revised identification and susceptibility system has significant clinical and taxonomic implications. Its introduction will improve speciation, identify antibiotic resistance and influence the choice of safer alternative therapy for patients infected with Nocardia spp. in the UK.

Bacterial Typing Techniques↗

Long-term investigation of the clonal dissemination of Klebsiella pneumoniae isolates producing extended-spectrum beta-lactamases in a university hospital.

Seventy isolates of Klebsiella pneumoniae with extended-spectrum beta-lactamases (ESBLs) were compared. These were isolated from 51 patients on 10 separate wards in one hospital over an 18-month period between 1992 and 1994. Antibiograms were determined and the isolates were typed by pulsed-field gel electrophoresis of their DNA digestion with XbaI. The isolates were compared to three genotypically different epidemic strains responsible for previous outbreaks at the hospital between 1988 and 1991. Isolates from 84% of the present patients had closely related XbaI patterns, and most (74%) produced an ESBL with an iso-electric point (pI) of 7.0. A similar pattern was found for one of the previous epidemic strains, but it produced an ESBL with a pI of 7.8; isolates with this latter enzyme variant were found only in six of the present patients. The two other previous epidemic strains had ESBLs with a pI of 6.3 and organisms related to them were found in one and two of the present patients, respectively.

Cephalosporins↗

Expression of beta-lactamases in Yersinia enterocolitica strains of biovars 2, 4 and 5.

Characteristic patterns of susceptibility to beta-lactam antibiotics are associated with different biovars of Yersinia enterocolitica. To elucidate the basis for these differences, the beta-lactamases of strains of Y. enterocolitica biovars 4 (n = 63), 2 (n = 12) and 5 (n = 10) were characterised. PCR fragments were generated from the beta-lactamase A (blaA) and B (blaB) genes; in addition, beta-lactamase induction tests were performed with imipenem as the inducer and beta-lactamase inhibition assays were undertaken with aztreonam and clavulanic acid. All the strains yielded PCR amplification fragments with primers to blaA and blaB. Biovar 4 strains had uniform patterns of beta-lactamase induction and inhibition: uninduced biovar 4 strains predominantly expressed BlaA, but low-level expression of BlaB was also detected; after induction, biovar 4 strains predominantly produced BlaB. Beta-lactamase expression varied between and within biovars 2 and 5: uninduced strains predominantly expressed either BlaA or BlaB, or exclusively BlaB; after induction BlaB was predominantly or exclusively expressed. Both the basal and induced levels of beta-lactamase varied within biovars 2 and 5. Some biovar 5 strains were not inducible; these predominantly produced BlaA. The results of this study show that biovar 2, 4 and 5 strains contain both blaA and blaB, but that the expression of the enzymes is regulated differently between the biovars, and varies within biovars 2 and 5. There was some correlation between antibiogram and the clusters defined from the beta-lactamase induction and inhibition tests, but it was not possible to predict beta-lactamase expression profiles from MIC data.

Animals↗

Cytotoxic and cell vacuolating activity of Vibrio fluvialis isolated from paediatric patients with diarrhoea.

Vibrio fluvialis is a halophilic Vibrio species associated with acute diarrhoeal illness in humans. It has the potential to cause outbreaks and has an association with paediatric diarrhoea. In this study, 11 V. fluvialis strains isolated from hospitalized patients with acute diarrhoea at the Infectious Diseases Hospital, Kolkata were extensively characterized. All the strains showed growth in peptone broth containing 7% NaCl. The strains showed variable results in Voges-Proskauer test and to a vibriostatic agent. There was also variation in their antibiograms, and some of the strains were multidrug resistant. Among the 11 strains, two showed only a single band difference in their PFGE profile and the remaining strains showed nine different PFGE patterns. However, unlike PFGE, the strains exhibited close matches and clustering in their ribotype patterns. The haemolytic effect on sheep red blood cells varied with strains. Partial sequence analysis revealed that the V. fluvialis haemolysin gene has 81% homology with that of the El Tor haemolysin of Vibrio cholerae. A striking finding was the capability of all the strains to evoke distinct cytotoxic and vacuolation effects on HeLa cells.

Bacterial Toxins↗

Real-time TaqMan PCR for rapid detection and typing of genes encoding CTX-M extended-spectrum beta-lactamases.

The prevalence of CTX-M-producing members of the Enterobacteriaceae is increasing worldwide. A novel, multiplex, real-time TaqMan PCR assay to detect and type bla(CTX-M) genes is described which is an improvement on previously described techniques with respect to reduced assay time, elimination of the need for protracted post-PCR processing and the convenience of a single reaction vessel. Based on beta-lactam antibiogram and MIC data, 478 of 1279 Enterobacteriaceae isolates from clinical blood and urine culture specimens were selected and tested for extended-spectrum beta-lactamase (ESBL) production using phenotypic methods. The new TaqMan assay detected and typed bla(CTX-M) genes in 21 of 28 ESBL-producing isolates.

Ampicillin↗

Genotyping of Staphylococcus epidermidis by small-fragment restriction endonuclease analysis and pulsed-field gel electrophoresis of genomic restriction fragments.

Small-fragment restriction endonuclease analysis (SF-REA) was established as a typing tool for Staphylococcus epidermidis. A total of 60 isolates comprising 48 epidemiologically nonrelated strains and 12 putatively linked isolates from 7 patients in 2 wards were analyzed. Nonrelated isolates were characterized by unique fingerprints when DNA was cleaved with EcoRI or ClaI, electrophoretically separated in a polyacrylamide gel, and silver stained. Three blood culture isolates from one patient in an intensive care unit, 4 isolates obtained from a child over a span of 2 weeks, and 5 isolates from 5 newborns in the same ward were grouped into 3 DNA pattern types, indicating identity of sequential isolates from 2 patients and nosocomial transmission of one Staphylococcus epidermidis strain between 5 babies. Results from pulsed-field gel electrophoresis of SmaI and SacII DNA digests and conventional marker systems such as antibiogram and plasmid profile were in accordance with these interpretations, whereas slight variation was observed in the biotypes of several strains. From the results of this study, we conclude that SF-REA is a precise and efficient method for the genotypic characterization of Staphylococcus epidermidis strains that can be used as a rapid and reliable typing tool.

Adult↗

Combined use of ribotyping, PFGE typing and IS431 typing in the discrimination of nosocomial strains of methicillin-resistant Staphylococcus aureus.

We have previously reported the phenotypic characterization of methicillin-resistant Staphylococcus aureus (MRSA) clinical strains isolated in Malaya University Hospital in the period 1987 to 1989 using antibiogram, coagulase typing, plasmid profiles, and phage typing. Here, we report the analysis of the same strains with three genotyping methods; ribotyping, pulsed-field gel electrophoresis (PFGE) typing, and IS431 typing (a restriction enzyme fragment length polymorphism analysis using an IS431 probe). Ribotyping could discriminate 46 clinical MRSA strains into 5 ribotypes, PFGE typing into 22 types, and IS431 typing into 15 types. Since the differences of the three genotyping patterns from strain to strain were quite independent from one another, the combined use of the three genotyping methods could discriminate 46 strains into 39 genotypes. Thus, the powerful discriminatory ability of the combination was demonstrated.

Bacterial Proteins↗

Evidence for the pathogenic role of Rhodococcus species in pulmonary diseases.

Three hundred expectorated sputa from patients suffering from chest disorders were examined microscopically and cultured on various media. Among other micro-organisms isolated there were four strains of Rhodococcus aurantiacus (Gordona aurantiaca), one each of Rh. erythropolis, Rh. pellegrino, Rh. rubropertinctus and Rh. rhodnii. Suspensions in 5% hog gastric mucin were virulent for immuno-suppressed white mice and the pathology of their lungs was compatible with those produced in experimental nocardial and rhodococcus infections. The in-vitro antibiogram was similar to that of Nocardia asteroides. Two of the patients from whom Rh. aurantiacus and Rh. pellegrino were isolated responded bacteriologically and clinically to treatment with co-trimoxazole. The frequency with which these rhodococci were isolated and the clinical conditions of the patients strongly indicated a pathogenic role for some Rhodococcus species. It is suggested that rhodococci should be sought in chronic pulmonary infections, particularly in those who are immuno-compromised or debilitated, and their aetiologic role determined.

Actinomycetales Infections↗

Characterization of Aeromonas salmonicida subsp. salmonicida: a comparative study of strains of different geographic origin.

A total of 130 strains of the fish pathogen Aeromonas salmonicida isolated in Denmark, Norway, Scotland, Canada and the USA were examined. The strains originated from farmed salmonid fish. The biochemical, physiological and serological characteristics, antibiotic resistance patterns and cell surface-related properties were compared. Aeromonas salmonicida was found to be remarkably consistent in general cultural and biochemical characteristics. It is noteworthy that the strains were positive in the fermentation of L-arabinose and were negative in the fermentation of D-arabinose. All the strains were highly proteolytic. It was observed, however, that 5% of the strains did not digest calf and trout serum and the production of haemolysin and degradation of casein by the same strains were delayed compared with the other strains. Common to all of the rough strains were auto-aggregation and ability to bind the dyes Coomassie brilliant blue and Congo red and the majority of these strains were highly hydrophobic. The strains were tested for their susceptibility to 22 antibacterial agents. Antibiotic resistance profiles of Aer. salmonicida indicated that resistance to the quinolones and oxytetracycline was increasing and that multi-resistant strains were found in several countries. The variation found in antibiograms could have potential as epidemiological markers in certain geographic areas.

Aeromonas↗

Molecular tracking of the lineage of strains of Vibrio cholerae O1 biotype El Tor associated with a cholera outbreak in Andaman and Nicobar Islands, India.

A large outbreak of acute watery diarrhoea involving all age groups of mongoloid tribal aborigines occurred during October-November, 2002 in the Nancowry group of Andaman and Nicobar Islands in the Indian Ocean. Twenty-one of the 67 stool samples from 67 patients were positive for toxigenic Vibrio cholerae O1, serotype Ogawa biotype El Tor, which showed striking similarity in its antibiogram with some of the strains of V. cholerae O1 Serotype Ogawa biotype El Tor isolated in Kolkata. The Nancowry and Kolkata isolates were compared with molecular tools involving random amplified polymorphic DNA (RAPD) fingerprinting, ribotyping and pulsed-field gel electrophoresis (PFGE). RAPD fingerprinting and ribotyping techniques revealed that all the V. cholerae strains associated with the outbreak in these islands were clonal in nature and identical to a population of isolates obtained from Kolkata since 1993. PFGE could discriminate within these Kolkata isolates further and established that a particular subtype of this population reached the remote Nancowry islands and was responsible for the outbreak.

Adolescent↗

Screening of Staphylococcus aureus, Staphylococcus intermedius, and Staphylococcus schleiferi isolates obtained from small companion animals for antimicrobial resistance: a retrospective review of 749 isolates (2003-04).

Companion animal staphylococcal isolate antibiograms were screened retrospectively to determine the frequency of methicillin-resistant (MR) infection by Staphylococcus aureus, Staphylococcus intermedius, and Staphylococcus schleiferi. Rates of MR were: S. aureus 35%, S. intermedius 17%, and S. schleiferi 40%. Frequency of isolation of methicillin-resistant S. aureus (MRSA) from dogs and cats was similar, whereas methicillin-resistant S. intermedius (MRSI) and methicillin-resistant S. schleiferi (MRSS) were significantly more common in dogs. MRSS was more commonly associated with superficial (skin and ear canal) infections, whereas MRSA was more commonly associated with deep infections. The MR strain resistance pattern to other classes of antibiotics was also investigated. MRSA was resistant to the most classes of antibiotics, followed by MRSI, while MRSS maintained the most favourable susceptibility profile. MR staphylococci may pose a significant risk to animal and public health. Therefore, to avoid selecting for resistant strains in cases of suspected staphylococcal infection, clinicians should consider culture and susceptibility testing early in the course of treatment.

Animals↗

Methicillin-resistant Staphylococcus aureus in community-acquired pyoderma.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial pathogen. It can also cause community-acquired infections. Indian reports about MRSA in community-acquired infections are rare. AIM: To evaluate the rate of MRSA in community-acquired pyoderma and the nasal colonisation with S. aureus in such patients. METHODS: Two hundred and fifty patients with community-acquired pyoderma, who attended outreach camps around Mangalore, south India between January 2000 and July 2001, were studied. Swabs collected from the skin lesions and anterior nares were inoculated onto blood agar and MacConkey's agar. Antimicrobial sensitivity testing was performed using Kirby-Bauer disk diffusion, agar dilution, and agar screen. RESULTS: Of 250 pyoderma cases, S. aureus was isolated from 202 (80.8%) patients. Twenty-two (10.9%) S. aureus isolates were methicillin resistant, 179 (88.6%) were resistant to penicillin, and 114 (56.4%) were resistant to erythromycin. S. aureus colonization in the anterior nares was observed in 136 (54.4%) cases, 11.8% of which were MRSA. Antibiograms of clinical isolates of S. aureus matched with nasal isolates in 99 (49%) cases. CONCLUSION: The emergence of MRSA in the community is a warning. A high nasal carriage rate may contribute to recurrent pyoderma. A correct antimicrobial policy and the avoidance of inappropriate antimicrobial usage are mandatory to reduce the spread of MRSA in the community.

Adolescent↗

Functional analysis of pVT745, a plasmid from Actinobacillus actinomycetemcomitans.

Plasmid pVT745 is a 25.1-kb replicon isolated from Actinobacillus actinomycetemcomitans strain VT745. A previous report described the hybridization of pVT745 in 5 strain-specific patterns to chromosomal DNA from 15 other A. actinomycetemcomitans strains. However, pVT745 does not share homology with the chromosome of the strain from which it was isolated, VT745. It was hypothesized that the shared areas of homology might represent insertion sequence elements and/or transposons possibly encoding resistance to one or more antibiotics. An antibiogram of strain VT745 demonstrated that this strain was uniformly susceptible to all antibiotics examined. Because insertion sequence elements and transposons are mobile genetic elements, a series of cell passaging experiments, followed by Southern hybridization was conducted in a attempt to detect transposition of pVT745 homologous DNA within the chromosomes of several A. actinomycetemcomitans strains. The results of these experiments suggested stability of the homologous DNA both within the chromosome and on the plasmid. It was also possible that pVT745 represented a lysogenic bacteriophage. Phage induction experiments were conducted under conditions that induced a previously described A. actinomycetemcomitans lysogenic phage, but no phage could be induced from strain VT745. Attempts to obtain isolates of VT745 cured of pVT745 were also unsuccessful.

Aggregatibacter actinomycetemcomitans↗

Carpegen real-time polymerase chain reaction vs. anaerobic culture for periodontal pathogen identification.

BACKGROUND/AIMS: The aim of this study was to compare two methods of microbiological diagnosis, anaerobic bacterial culture and real-time polymerase chain reaction (PCR), for the detection of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, Fusobacterium nucleatum, and Treponema denticola. METHODS: Seventy-two samples were collected from 18 patients who were suffering from aggressive periodontitis. The data obtained were compared for the two methods. RESULTS: The results obtained with real-time PCR were different from those obtained with bacterial culture. The detection differences were 3% for A. actinomycetemcomitans, 8.33% for P. intermedia, and 12.5% for F. nucleatum. However, the differences for P. gingivalis and T. forsythia were 51.39% and 36.11%, respectively. No comparison was possible for T. denticola because it cannot be identified in culture. The variations found were the result of the better detection level (10(2) pathogens) of the PCR probe. Unlike bacterial culture, PCR allows the detection of T. denticola, which does not forming colonies and is oxygen sensitive. For F. nucleatum, T. forsythia and P. gingivalis, the real-time PCR technique was more sensitive than culture. CONCLUSION: Good results were obtained with the real-time PCR technique for the six periopathogens targeted. This method seems to be indicated for its simplicity, rapidity and reproducibility but it cannot analyze data for an antibiotic susceptibility test. The periodontist must therefore choose one of these two methods according to his specific clinical objective: to obtain rapid, specific detection even with weak initial concentrations (but for targeted periopathogens only) or to be non-specific and analyze the pathological activity with an antibiogram.

Aggregatibacter actinomycetemcomitans↗

Investigation of a cluster of Staphylococcus aureus invasive infection in the top end of the Northern Territory.

INTRODUCTION: Staphylococcus aureus invasive infection remains a serious condition associated with considerable morbidity and mortality. Following notification of five cases at Royal Darwin Hospital (RDH), we searched for related cases, determined their epidemiological characteristics and attempted to identify the source of this apparent cluster. METHODS: We reviewed RDH microbiology records between June 1996 and April 1997 for S. aureus isolates with similar antibiograms to notified cases. We used antibiotic resistance patterns, bacteriophage typing and two molecular typing techniques to subtype implicated isolates. Hospital records were reviewed for admission details and associated costs were estimated. RESULTS: Fifty-four cluster-related isolates occurred in 47 separate presentations. The peak incidence was in the wet season. The most important risk factor for staphylococcal invasive infection was the presence of skin sores/scabies in 17/54 cases (31%), followed by intravascular line use in 14/54 (26%), open trauma in 11/54 (20%), underlying end stage renal failure and alcoholism each in ten of 54 (18%). The mean admission length was 30 days and antibiotics were given for an average of 23 days. Death due to S. aureus infection occurred in eight of 47 (17%) presentations. S. aureus pneumonia was community acquired in 12/13 patients (92%) and six of 13 (46%) died. Ten of 13 (80%) pneumonia patients had at least one other focus of S. aureus infection. The cost of antibiotics and hospital bed per presentation was approximately $16,000. Presentations with skin sores/scabies cost considerably more ($31,000). No common epidemiologic features were found for community or hospital acquired cases. CONCLUSION: Considerable mortality and cost was attributable to cases of S. aureus invasive infection during this cluster; particularly those with community acquired pneumonia or skin sores/scabies. Staphylococcal antibiotic cover should be considered early for unwell patients presenting to hospital with pneumonia and other signs of potential S. aureus infection. It is appropriate to target public health efforts to prevent skin sores and to provide adequate treatment when they occur.

Adolescent↗