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PubMed1991

Epidemiological study of an outbreak of Serratia marcescens in a haemodialysis unit.

Twenty-three isolates of Serratia marcescens were isolated over a 10-month period from the blood and arteriovenous shunt sites of patients undergoing haemodialysis in an artificial kidney unit. Surveillance measures performed on the equipment, sterile materials, environment and personnel of this unit yielded Serratia from the air conditioner and one of the dialysis units. The isolates from the patients and dialyser unit were pigmented and had an identical biochemical profile, antibiograms, phage typing pattern and O serotype. The isolate from the air conditioner, though of the same biotype, had a different phage and serotype. It was concluded that the dialyser was the 'common source' and that the organism was persisting in the machine in spite of recommended sterilization procedures being implemented.

Cross Infection↗
PubMed1993

Nosocomial colonization and infection with multiresistant Acinetobacter baumannii: outbreak delineation using DNA macrorestriction analysis and PCR-fingerprinting.

The prevalence of nosocomial acinetobacter colonization and infection in a university hospital was reviewed and multiresistant Acinetobacter baumannii infections in an intensive care unit (ICU) were investigated using epidemiological typing and a case-control study. Acinetobacter colonization at various body sites was found in 3.2 to 10.8 per 1000 patients. Acinetobacter infection accounted for 0.3% of endemic nosocomial infections in critically ill patients and for 1% of nosocomial bacteraemia hospitalwide. Over a three-week period, four ventilated patients developed colonization, followed by pneumonia in two patients, with A. baumannii resistant to multiple antimicrobials. Cultures of samples from respiratory equipment and ICU surfaces (n = 27) as well as from hands of personnel (n = 14) failed to yield A. baumannii, except for one sample of respiratory tubing. Antibiogram, biotype, chromosomal DNA macrorestriction profiles and polymerase chain reaction (PCR) mediated fingerprints of A. baumannii isolates (n = 31) indicated that this outbreak was caused by two strains, one of which later spread to another hospital where it caused a second outbreak. Both strains were clearly discriminated from control strains from cases of sporadic infection. Risk factors for cross-colonization that were identified by a case-control comparison were neurosurgery, mechanical ventilation and treatment with broad-spectrum antibiotics. Transmission was controlled by implementing contact isolation precautions and routine sterilization of ventilator tubing. Wider use of sensitive genotypic methods like DNA macrorestriction analysis and PCR-mediated fingerprinting for typing nosocomial pathogens should improve the detection of micro-epidemics amenable to early control.

Acinetobacter↗
PubMed1993

Comparison of three typing methods in hospital outbreaks of Acinetobacter calcoaceticus infection.

During a period of 11 months Acinetobacter baumanii was isolated from 27 patients and 21 environmental samples in the Intensive Care Unit (ICU) and in one surgical unit of a University Hospital. The isolates were characterized by biotyping, antibiograms and plasmid profiles and compared with co-isolates. Plasmid fingerprinting distinguished three outbreaks, whereas other typing methods were less sensitive and discriminatory. Although plasmid profiles seem to be a simple and reproducible marker for epidemiological studies with acinetobacter strains, it might be useful to combine at least two typing methods since plasmids are unstable genetic structures, and not all strains possess plasmids.

Acinetobacter Infections↗
PubMed1993

Outbreak of methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit.

An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) occurred in a neonatal intensive care unit (NICU) over a period of 2 months involving 16 babies, mainly of low birth weight. Arbitrary grouping of the isolates showed that there were apparently three different strains involved in the outbreak, as determined only by antibiogram. Twenty-three out of 27 isolates were allocated to 'group 1' based on antibiotic sensitivity pattern. Control of spread of the MRSA in the unit was difficult because of some technical constraints but eradication was finally achieved by cohort nursing and treatment with topical mupirocin in paraffin base. All MRSA isolates were resistant to gentamicin, erythromycin, tetracycline and at least four other antibiotics but sensitive to vancomycin. Overcrowding, limited space, inadequate cleaning of the equipment and initial lack of correct attitude to scrupulous handwashing techniques, all appeared to contribute to the ease of spread of the strains involved.

Colony Count, Microbial↗
PubMed1993

Daily scrub with chlorhexidine reduces skin colonization by antibiotic-resistant Staphylococcus epidermidis.

The aim of this study was to establish whether long-term use of chlorhexidine would prevent skin colonization by antibiotic-resistant Staphylococcus epidermidis. Ten nurses, working on a ward for haematological disorders, volunteered to participate in the test. They washed one arm every morning for three weeks with chlorhexidine gluconate, ('Hibiscrub' ICI Pharmaceuticals). The other arm served as a negative control. Samples from the antecubital fossa of both arms were taken two to three times a week during the wash period and two weeks thereafter, giving a total of 216 samples. The appearance of resistant S. epidermidis with different antibiograms was analysed. During the wash period the total bacterial counts and the counts of the resistant S. epidermidis strains on the test arm were both about one-tenth of those on the control arm, a significant difference (P < 0.05). Moreover, there were significantly fewer resistant S. epidermidis on the test arm, 1.3 per sample, than on the control arm, 2.5 per sample (P < 0.01). Most of the resistant S. epidermidis were only found once or a few times on the same site, after which they disappeared, though a few persisted on the skin even during 'Hibiscrub' washing. In an agar dilution test, chlorhexidine minimum inhibitory concentrations (MICs) of persisting strains were the same as for strains disappearing from the skin following 'Hibiscrub' washing, 1.0 or 2.0 mg l-1, but somewhat higher than MICs of strains isolated from healthy carriers outside the hospital whose MICs were 0.5 mg l-1. The relative contribution to the skin counts by those S. epidermidis strains found only occasionally were compared with those found repeatedly but no difference in reduction was found between these categories during 'Hibiscrub' washing.

Adult↗
PubMed1993

Molecular typing of Enterobacter cloacae by pulsed-field gel electrophoresis of genomic restriction fragments.

Eleven multiply resistant Enterobacter cloacae isolates were obtained from eight preterm neonates in a neonatal intensive care unit (NICU) of one hospital in Osnabrück, together with one sensitive strain from another infant. The presence of similar antibiograms and biotypes in 11 isolates prompted further characterization of the isolates by pulsed-field gel electrophoresis (PFGE) of NotI generated genomic restriction fragments. For assessment of the discriminatory power of this typing method 50 non-related strains were included in the study. Non-related strains demonstrated a marked variation in restriction fragment patterns and were clearly discriminated one from another. In contrast, 11 of 12 isolates from the NICU exhibited identical restriction profiles, indicating a cluster associated with nosocomial infection. Since the discriminatory power of PFGE is high, reproducibility is good, and all reagents and equipment for DNA fingerprinting are commercially available, this technique is proposed as a useful tool in the microbiology laboratory for investigating the epidemiology of E. cloacae strains.

Bacterial Typing Techniques↗
PubMed1993

Enhanced ability to colonize the skin: a possible explanation for the epidemic spread of certain strains of Staphylococcus epidermidis.

Experimental skin colonization was attempted on healthy volunteers using one epidemic and two non-epidemic strains of Staphylococcus epidermidis isolated from a bone marrow transplant unit. Although the three strains had similar biochemical reactions, they had different antibiograms and plasmid patterns, and the epidemic strain grew rather more slowly when in a mixture in broth. Two experiments involving sets of 5 volunteers were performed. The epidemic strain was mixed with one non-epidemic strain for experiment 1, and with the other for experiment 2. Each volunteer had an inoculum of a mixture of 10(7) cfu of each strain inoculated onto the antecubital fossae of both arms; one of the arms had had a prior treatment with chlorhexidine to see if this would prevent colonization. Quantitative skin cultures were continued until the test strains could no longer be isolated. Colonization occurred in all but one volunteer, and lasted from a few weeks to 17 months. Maximal counts of the epidemic strain were significantly higher than the maximal counts of the non-epidemic strains. Chlorhexidine had no effect in experiment 1, and caused a reduction in intensity and duration of colonization in experiment 2, although this did not achieve statistical significance. Plasmid patterns were unchanged throughout, but in two instances a variant of the epidemic strain that had lost resistance to methicillin and tobramycin was isolated together with the parent strain. The enhanced ability of the epidemic strain to colonize skin may be an important factor in allowing cross-infection.

Chlorhexidine↗
PubMed1994

A nosocomial outbreak due to non-encapsulated Haemophilus influenzae: analysis of plasmids coding for antibiotic resistance.

An outbreak of infections with non-encapsulated Haemophilus influenzae, resistant to ampicillin, chloramphenicol, sulphonamide and tetracycline involved 13 elderly patients and three nurses on acute admission and care of the elderly wards. Thirty-two isolates were found to be indistinguishable on analysis of biotype, antibiogram, serotype and major outer membrane proteins (MOMP). Plasmids could not be identified in the original isolates but after mating with a Rec A H. influenzae recipient, the resultant transconjugates were found to harbour either a 72 kilobase pair (kB) plasmid coding for resistance to chloramphenicol, ampicillin, sulphonamide and tetracycline or a 65 kB plasmid coding for resistance to chloramphenicol, ampicillin and sulphonamide. Both plasmids yielded virtually indistinguishable restriction digest patterns. This suggests that the tetracycline resistance gene (Tc gene) is a non-essential component of one basic plasmid responsible for the multiple antibiotic resistances seen in the strains recovered during the outbreak. This illustrates the value of plasmid profiles to compare strains of non-encapsulated H. influenzae, and suggests that plasmid restriction enzyme analysis is critical.

Aged↗
PubMed1994

PCR based fingerprinting of Enterobacter cloacae.

An outbreak of lower respiratory tract infection with Enterobacter cloacae occurred in an intensive care unit in a university teaching hospital. Random amplification of polymorphic DNA (RAPD) was used to assist in the investigation of the outbreak. The technique was readily applied to this organism and permitted differentiation between strains which had identical biochemical profiles and antibiograms. The versatility of this technique makes it attractive for use in hospitals where fingerprinting of any one of the many Gram-negative rods associated with nosocomial infection may be required from time to time.

Cross Infection↗
PubMed1995

Outbreak caused by two multi-resistant Acinetobacter baumannii clones in a burns unit: emergence of resistance to imipenem.

Since early 1992 an increased number of tobramycin- and imipenem-resistant Acinetobacter spp. were observed causing colonization, wound infections, and bacteraemias in a burns and plastic surgery unit. This raised the question of whether this outbreak was caused by a single or by multiple Acinetobacter spp. clones. To study this, 97 Acinetobacter spp. isolates from clinical samples from different hospital units as well as isolates from the environment and the hands of the staff were characterized by antibiogram, plasmid profile and ribotyping. Two dominant multi-resistant A. baumannii clones were identified; one of them was sensitive to polymyxin B only. There was a close correlation between the results obtained by plasmid profiling and ribotyping. No common environmental source or significant hand carriage, or spread of these strains outside the unit were detected. The burns patients were the most likely reservoir, and strain transmission occurred in spite of strict control measures.

Acinetobacter↗
PubMed1995

A major outbreak of methicillin-resistant Staphylococcus aureus caused by a new phage-type (EMRSA-16)

An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) infection caused by a novel phage-type (now designated EMRSA-16) occurred in three hospitals in East Northamptonshire over a 21-month period (April 1991--December 1992). Four hundred patients were colonized or infected. Seven patients died as a direct result of infection. Chest infections were significantly associated with the outbreak strain when compared with methicillin-sensitive S. aureus. Twenty-seven staff and two relatives who cared for patients were also colonized. A 'search and destroy' strategy, as advocated in the current UK guidelines for control of epidemic MRSA was implemented after detection of the first case. Despite extensive screening of staff and patients and isolation of colonized and infected patients, the outbreak strain spread to all wards of the three hospitals except paediatrics and maternity. A high incidence of throat colonization (51%) was observed. Failure to recognize the importance of this until late in the outbreak contributed to the delay in containing its spread. Key parts of the strategy which eventually contained the local outbreak were the establishment of isolation wards in two hospitals, treatment of all colonized patients and staff to eradicate carriage and screening of all patients upon discharge from wards where MRSA had ever been detected. EMRSA-16 spread to neighbouring hospitals by early 1992 and to London and the South of England by 1993. It is distinguished from other epidemic strains by its characteristic phage-type, antibiogram (susceptibility to tetracycline and resistance to ciprofloxacin), and in the pattern given on pulse field electrophoresis.

Adolescent↗
PubMed1995

Molecular epidemiology of a multiple strain outbreak of methicillin-resistant Staphylococcus aureus amongst patients and staff.

Since methicillin-resistant Staphylococcus aureus (MRSA) isolates are not endemic in our hospital, which is a tertiary referral centre, the finding of 13 MRSA isolates from 12 patients associated with an acute vascular surgery ward between October 1993 and December 1993 prompted further epidemiological and laboratory investigations. Two strains were distinguished by antibiogram and phage-typing. One strain, resembling EMRSA-16, colonized six patients and was probably introduced from another hospital in the Oxford Region. Five other patients were colonized by a second strain, gentamicin-resistant and non-typable by phage-typing, probably introduced into the hospital 12 months previously by a patient from Nairobi, Kenya. A 12th patient was colonized by both strains simultaneously. Of 46 staff members screened three were colonized--one by an EMRSA-16 strain, a second by the gentamicin-resistant 'Nairobi'-strain and a third member carried yet a further distinct MRSA strain. The healthcare worker colonized by the 'Nairobi'-strain had been carrying the isolate 12 months previously and was the likely source of this strain. These isolates were also characterized by the repetitive extragenic palindromic-polymerase chain reaction (REP-PCR), a novel PCR-based methodology which has not been previously used in characterizing Staphylococcus aureus in an outbreak. This method corroborated the strain classifications provided by the traditional methods, confirming that there had been spread of two strains simultaneously. Our study demonstrates that multiple strains of MRSA may circulate amongst patients and staff during an outbreak, patients may be colonized by more than one strain simultaneously and long-term staff carriage (> 12 months) may be an important source of colonization in patients. REP-PCR is a rapid and effective molecular typing method for MRSA.

Bacterial Typing Techniques↗
PubMed1995

Pillows, an unexpected source of Acinetobacter.

From 1989 until 1992 an increase in the number of isolations of Acinetobacter was observed in a community hospital in The Netherlands. The organisms were spread throughout the hospital and a common source was suspected. Feather pillows were found to harbour high numbers of acinetobacters. Replacement with synthetic pillows and correction of the laundry procedure resulted in a significant reduction of Acinetobacter isolations. A number of isolates from patients and from pillows were indistinguishable using biotyping, antibiogram typing and cell envelope protein typing. By the use of DNA-DNA hybridization most isolates were identified to A. baumannii and the unnamed closely related genomic species 13. A number of isolates, mostly from pillows, were identified as A. radioresistens. The outcome of cultivation, intervention and typing suggests that the feather pillows played an important role in the outbreak.

Acinetobacter↗
PubMed1989

Epidemiology and mechanisms of antimicrobial resistance.

Bacterial evolution and the emergence of antimicrobial drug resistance continue to interfere with the successful treatment of infections by both community- and hospital-based physicians. Resistance has emerged to even the newer, most potent antimicrobial agents. Although generalizations can be made about the appropriateness of antimicrobial agents on the basis of published susceptibility patterns, significant regional, demographic, and interinstitutional variables exist that require each hospital to establish its own antibiotic data base and antibiogram. In particular, multiresistant pathogens occur infrequently in acute care community hospitals compared with tertiary care centers. Important clinical factors that promote the emergence of drug-resistant flora include prolonged therapy, the persistence of foreign bodies, sequestra, or prostheses, and the inadequate surgical debridement of necrotic tissue or abscesses. Antibiotic resistance may occur through changes in the permeability of the cell wall or outer membrane, by alteration of the antimicrobial binding or target site, and by inactivation or modification of the drug by bacterial enzymes. These mechanisms are reviewed. In particular, gram-negative beta-lactamases, methicillin-resistant staphylococci, multiresistant enterococci, and the emergence of fluoroquinolone resistance are discussed in detail.

Anti-Bacterial Agents↗
PubMed1991

Efficiency in pathology laboratories: a survey of operations management in NHS bacteriology.

In recent years pathology laboratory services in the U.K. have experienced large increases in demand. But the extent to which U.K. laboratories have introduced controls to limit unnecessary procedures within the laboratory was previously unclear. This paper presents the results of a survey of all 343 NHS bacteriology laboratories which records the extent to which such operations management controls are now in place. The survey shows large differences between laboratories. Quality controls over inputs, the use of screening tests as a culture substitute, the use of direct susceptibility testing, controls over routine antibiotic susceptibility testing, and controls over reporting of results all vary widely. The survey also records the prevalence of hospital antibiotic policies, the extent to which laboratories produce antibiograms for user clinicians, the degree of computerisation in data handling, and the degree of automation in processing specimens. Finally, the survey uncovers a large variation between NHS labs in the percentage of bacteriology samples which prove positive and lead to antibiotic susceptibility tests being carried out.

Bacteriological Techniques↗
PubMed1992

Updated evaluation of the activity of antibiotics in a burn centre.

The results of microbiological tests performed in a burns unit between January 1989 and December 1990 have been analysed. Burn wound swabs and biopsies, blood cultures, central venous and urinary catheters, bronchial aspirates, pharyngeal swabs and faecal cultures for a total of 7950 examinations were considered. Staph. aureus was the most frequently isolated bacterium, followed by Staph. epidermidis, Pseud. aeruginosa and E. coli. The antibiograms have shown a low efficacy rate of cephalosporins, even of the latest generation, while with Gram-positive isolates the highest rates of activity were recorded by vancomycin and teicoplanin (100 per cent sensitivity). The situation seems better with Gram-negative organisms since they appear to be sensitive to a larger number of antimicrobial agents.

Adolescent↗
PubMed1996

A comparison of phenotypic properties of Staphylococcus aureus isolated from burned children and other patient groups.

This study aimed to determine whether strains of Staph. aureus isolated from children on our paediatric burns unit were different from strains isolated from other patient groups. Of particular interest was the incidence of toxin production amongst the different patient groups and the potential association with toxic shock syndrome (TSS). Wound isolates of Staph. aureus were collected from three patient groups: (1) hospital inpatients, (2) community patients and (3) patients from a regional burns unit. One hundred isolates were collected from each group (n = 300). Each isolate was tested for enterotoxin and TSST-1 production, phage type, antibiogram and tryptophan dependence. The results were compared, to determine whether there were any differences between the isolates from each of these patient groups. There were some variations in antibiotic sensitivity patterns and phage type of the isolates between the different patient groups but there was no significant difference in the incidence of toxin production, which was an important observation. The 100 isolates collected from this burns unit were derived from 58 patients. The colonization patterns of the Staph. aureus showed that 12 patients were colonized by more than one isolate and that these were a mixture of toxin-positive and toxin-negative strains. The medical records were examined for evidence of TSS; there was a higher incidence of toxic episodes in the patients colonized with strains which produced TSST-1 toxin.

Anti-Bacterial Agents↗
PubMed1995

Antibioresistance of Escherichia coli strains isolated in Morocco from chickens with colibacillosis.

Two hundred and fifty eight isolates of Escherichia coli were made from autopsied chickens showing lesions of avian colibacillosis. Antibiograms showed high levels of resistance (greater than 40%) to sulphonamides (SSS), oxytetracycline (OT), trimethoprim + sulphamethoxazole (STX) and chloramphenicol (C). Medium frequencies of resistances (from 15 to 40%) were noted for streptomycin (S), spectinomycin (SPT), nalidixic acid (NA), oxolinic acid (OA), flumequine (UB) and enrofloxacine (ENR). For ampicillin (AM), gentamicin (GM), nitrofurans (FT), colistin (CS) and rifampin (RA) the frequencies of resistance were low (less than 15%). A linked resistance was observed for the 4 quinolones. A significant percentage of isolates (82.5%) were resistant to at least 2 antimicrobial agents. The most frequent antibiotypes were: C.OT.SSS.STX (4.65%), C.OT.SSS.STX.OA.NA.UB.ENR (4.65%), AM.S.C.OT.SSS.STX (4.26%) and OT.SSS.STX (3.87%).

Animals↗