Spread of resistant gram-negative bacilli in a burns unit

Risk Factors for the Antibiotic Resistant Gram-Negative Bacilli Associated Infections in Burn Patients and the In-Vitro Susceptibility of Colistin

Background: Burns patients are predisposed to infectious complications. Amongst microbial infections, Gram-negative bacilli are the most prevalent bacteria in the burn units. Objectives: The current study aimed to identify the risk factors associated with antibiotic-resistant Gram-negative bacilli in hospitalized burn patients and determine the in-vitro susceptibility of these organisms to colistin. Methods: Two hundred burn patients hospitalized in the burn unit and ICU burn ward were allocated to two groups (each with 100 patients) of patients with antibiotic-resistant Gram-negative bacilli infections and the other with antibiotic susceptible Gram-negative bacilli associated infections. The susceptibility of Gram-negative bacilli was done towards various antibacterial agents by the Kirby-Bauer method. Susceptibility of colistin was performed using both E-test and disc diffusion methods. Results: The history of antibiotic usage, length of ICU stay, mechanical ventilation, and catheter usage were the most important risk factors for infections associated with antibiotic-resistant Gram-negative bacilli. Pseudomonas aeruginosa and Acinetobacter baumannii were the most prevalent bacteria in the burn unit. Only one A. baumannii isolate was found resistant toward colistin by both disk diffusion and E-test methods. Conclusions: Burn patients are prone to infections, and Gram-negative bacilli predominates in patients harboring risk factors. These findings influence the choice of traditional therapeutic regimens in such patients. Colistin served as an appropriate antibiotic choice.

The Inanimate Environment of an Intensive Care Unit as a Potential Source of Nosocomial Bacteria: Evidence for Long Survival of Acinetobacter calcoaceticus

Environmental surface and personnel hand impression cultures were obtained during 13 sampling periods in the University of Virginia Pediatric Intensive Care Unit to document potential reservoirs of nosocomial pathogens. In 78 environmental cultures Staphylococcus aureus was found eight times and gram-negative bacilli ten times. The patient chart cover was the most commonly contaminated surface. Acinetobacter calcoaceticus was found in five of ten cultures positive for gram-negative bacilli. Thirty of 59 hand cultures were positive for S aureus and gram-negative bacilli; nurses and residents had both, respiratory therapists only gram-negative bacilli, and A calcoaceticus was the most commonly isolated bacterium of potentially nosocomial significance (14/30). Laboratory investigation of bacterial survival revealed that gramnegative bacilli survived on a dry formica surface from a few hours up to three days but Acinetobacter survived up to 13 days. Since A calcoaceticus has been implicated in many nosocomial infections, its long survival on a dry surface may be an additional factor in its transmission in hospitals and suggests that more attention be paid to environmental surfaces as a source of significant nosocomial pathogens.

Pseudomonas infections in the thermally injured patient

Pseudomonas aeruginosa, remains a serious cause of infection and septic mortality in burn patients, particularly when nosocomially acquired. A prototypic burn patient who developed serious nosocomially acquired Pseudomonas infection is described as an index case which initiated investigations and measures taken to identify the source of the infection. The effect of changes in wound care to avoid further nosocomial infections was measured to provide data on outcome and cost of care. The bacteriology of Pseudomonas is reviewed to increase the burn care providers understanding of the behaviour of this very common and serious pathogen in the burn care setting, before reviewing the approach to detection of the organism and treatment both medically and surgically. After controlling the nosocomial spread of Pseudomonas in our burn unit, we investigated the morbidity and mortality associated with nosocomial infection with an aminoglycoside resistant Pseudomonas and the associated costs compared to a group of case-matched control patients with similar severity of burn injury, that did not acquire resistant Pseudomonas during hospitalization at our institution. We found a significant increase in the mortality rate in the Pseudomonas group compared to controls. The morbidity in terms of length of stay, ventilator days, number of surgical procedures, and the amount of blood products used were all significantly higher in the Pseudomonas group compared to controls. Costs associated with antibiotic requirements were also significantly higher in the Pseudomonas group. Despite this increased resource consumption necessary to treat Pseudomonas infections, these efforts did not prevent significantly higher mortality rates when compared to control patients who avoided infection with the resistant organism. Thus, in addition to the specific measures required to identify and treat nosocomial Pseudomonas infections in burn patients, prevention of infection through modification of treatment protocols together with continuous infection control measures to afford early identification and eradication of nosocomial Pseudomonas infection are critical for cost-effective, successful burn care.

Outbreak of infection in a burns unit due to Pseudomonas aeruginosa originating from contaminated tubing used for irrigation of patients

Five patients with extensive deep burns developed septicaemia due to Pseudomonas aeruginosa serogroup O-7.8 and phage type 21 or 21/188 shortly after they had been admitted to hospital. Four other burned patients became colonized with the same strain. The source of infection was contaminated tap water used for irrigation of the burns, as part of the first-aid treatment which the patients received when entering the hospital. Contamination was restricted to showers and tubing that were permanently connected to the taps, and the outbreak stopped after they had been disinfected. Tubing and showers used for irrigation of burns should be dismantled and heat-disinfected after each patient and not reconnected to the taps until immediately before the next treatment. Taps used for irrigation of burns should be monitored regularly for the presence of P. aeruginosa and other potentially pathogenic bacteria. Routine typing of P. aeruginosa isolates from burned patients is indicated in order to detect and eliminate hidden sources of infection.

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.

Epidemiological surveillance of Acinetobacter species

Two hundred and sixty Acinetobacter isolates were recovered from 237 patients over a 2-year period; 156 isolates from 135 spinal cord injuries unit (SCIU) patients and 104 isolates from 102 patients in all the other hospital units. In SCIU patients, 133 isolates were recovered from the urine, 21 from wounds and aspirates, one from sputum and one from blood culture. In non-SCIU patients, 12 isolates were recovered from urine, 43 from wounds and aspirates, 48 from sputum and one from blood culture. Sixty-nine percent of isolates from SCIU patients showed resistance to gentamicin compared to 3% from non-SCIU patients. Gentamicin-resistant Acinetobacter anitratus was recovered from many environmental sites in the SCIU wards and from the hands of seven of 94 SCIU staff members tested. Serial rectal swabs were obtained from 79 newly-diagnosed SCIU patients. Ninety-two percent of those patients followed for up to 5 months acquired gentamicin-resistant Acinetobacter anitratus in their intestinal tract. API 2ONE profiles and antibiograms suggested that two distinct gentamicin-resistant strains of A. anitratus had become endemic in the SCIU and that nosocomial transmission was a frequent occurrence.

The inanimate environment of an intensive care unit as a potential source of nosocomial bacteria: evidence for long survival of Acinetobacter calcoaceticus

Environmental surface and personnel hand impression cultures were obtained during 13 sampling periods in the University of Virginia Pediatric Intensive Care Unit to document potential reservoirs of nosocomial pathogens. In 78 environmental cultures Staphylococcus aureus was found eight times and gram-negative bacilli ten times. The patient chart cover was the most commonly contaminated surface. Acinetobacter calcoaceticus was found in five of ten cultures positive for gram-negative bacilli. Thirty of 59 hand cultures were positive for S aureus and gram-negative bacilli; nurses and residents had both, respiratory therapists only gram-negative bacilli, and A calcoaceticus was the most commonly isolated bacterium of potentially nosocomial significance (14/30). Laboratory investigation of bacterial survival revealed that gram-negative bacilli survived on a dry formica surface from a few hours up to three days but Acinetobacter survived up to 13 days. Since A calcoaceticus has been implicated in many nosocomial infections, its long survival on a dry surface may be an additional factor in its transmission in hospitals and suggests that more attention be paid to environmental surfaces as a source of significant nosocomial pathogens.

Acinetobacter calcoaceticus biovar anitratus septicaemia in a neonatal intensive care unit: epidemiology and control

Nineteen neonates with septicaemia caused by Acinetobacter calcoaceticus biovar anitratus were treated in a neonatal intensive care unit between October, 1983 and March, 1986. The ages of the patients at the onset of septicaemia ranged from 4 to 22 days (mean 9.7 days). Their birth weights ranged from 1000 g to 3350 g (mean 1790 g) and were less than 2000 g in 14 patients. Antibiotics had been administered to 17 of the 19 neonates before the onset of septicaemia, and all mature infants had received prior antibiotic therapy, intubation or had suffered from a convulsion. Acinetobacter anitratus strains were isolated from pharyngeal swabs and/or faeces from 35 (79.5%) out of 44 infants of less than 2000 g. These strains were also isolated from the hands of staff members, and from equipment such as sinks and baths in the unit. It was likely that nosocomial infection via the hands of the staff occurred. Encouraging frequent hand-washing, strict antibiotic use, and cohorting of colonized infants resulted in a reduction of colonization and no further cases of septicaemia were reported.

Minimizing the potential for nosocomial pneumonia: architectural, engineering, and environmental considerations for the intensive care unit

The development of pneumonia in seriously ill patients remains an important concern of intensive care medicine. The design of the intensive care unit will have a direct effect upon the potential for infection. Persons involved in this design should consider engineering and architectural elements that will ultimately contribute to lower rates of infection. These include components to regulate the atmosphere, such as ventilation systems and temperature and humidity controls. Sources of contaminated water and the amplification mechanisms need to be addressed and minimized in the final designs. Architectural elements such as treatment space and lighting encourage optimal patient management and workable staffing patterns. Personnel who treat seriously ill patients should be part of the planning and design process in the construction and renovation of intensive care facilities.

Hand disinfection: a comparison of various agents in laboratory and ward studies

The efficacy of 14 handwashing or disinfectant preparations was compared in laboratory tests on staff volunteers. The test organism, Escherichia coli, was applied to the fingertips and log reductions (LR) were measured following treatment with the test agent and control preparations (70% isopropanol and non-medicated bar soap). Alcoholic preparations, particularly n-propanol and isopropanol were the most effective showing LRs of 3.1-3.8. Chlorhexidine (LR 2.9) and povidone-iodine detergent preparations were significantly more effective than non-medicated soap (LR 2.1), but triclosan products were not. In addition the residual effect of several of these formulations was assessed after 10 applications by comparing the survival of E. coli on the fingertips over a 32-min period. This number of handwashes compares favourably with those recorded during an 8 h nursing shift. Chlorhexidine-detergent consistently showed the best residual activity. Alcoholic formulations showed little or no residual effect. The survival studies show that on the whole gram-positive organisms (Staphylococcus aureus and Candida albicans) survive better on the skin than Gram-negative bacilli (GNB). However, it would seem that GNB which are considered to be residents (Acinetobacter calcoaceticus and Enterobacter spp.) survive much better than many other GNB (Pseudomonas aeruginosa, E. coli and Proteus vulgaris). The Klebsiella species varied in survival times. Random sampling of ward staff hands showed that contamination with S. aureus and GNB was greater in dermatological and general wards than in an isolation unit, where handwashing or disinfection was carried out after every patient contact. No cross-infection occurred in the isolation ward during periods of study in which 70% alcohol, chlorhexidine-detergent and non-medicated soap were used.

Plasticized polyvinyl chloride film as a primary burns dressing: a microbiological study

Twenty-four patients were studied after the application of plasticized polyvinyl chloride (PVC) film as a temporary burns dressing. The burns were assessed as being partial thickness (nine patients) and full thickness (15 patients) in depth and involving 2 per cent to 35 per cent of the body surface area. Microbiological cultures were performed on the exudate beneath the plasticized PVC film and then at each dressing change until the burn was healed. Bacterial isolates showed no unexpected organisms and there was no predominant organism to suggest contamination from the plasticized PVC film. Indeed, bacteria were only rarely isolated from the initial exudate (three of 37 burn wounds), and subsequent bacterial cultures did not differ from those normally found in burn wounds. In addition, incorporation of the plasticized PVC film into nutrient broth and agar with Staph, aureus and Ps. aeruginosa did not influence the recovery of these organisms, indicating that plasticized PVC film does not exert any antibacterial effect.

Endemic occurrence of Acinetobacter calcoaceticus biovar anitratus in an intensive care unit

One strain of Acinetobacter calcoaceticus biovar anitratus caused colonization of 111 patients admitted to an intensive care unit (ICU) during a 2-year period. All patients were intubated and had received antibiotic therapy prior to colonization. Morbidity due to the organism was about 1%. The colonization rate showed a decreasing trend during the study period, but no seasonal variation. The strain was found in the air in a low concentration and on the hands of 8-13% of the members of the staff. No chronic carriers were found.

Systemic antibiotic treatment in burned patients

Systemic antibiotics are a valuable therapeutic modality in the burned patient when properly used. Injudicious use, however, may not only fail to be beneficial to the patient but also may produce harmful effects--either through direct toxicity or by contributing to the emergence of resistant strains of micro-organisms. General guidelines and principles for systemic antibiotic use include the following: The burned patient, despite all efforts, will be exposed to microorganisms. No single agent or combination of agents can destroy all the organisms to which the burned patient is exposed. Treatment involves first identifying the organism responsible for clinical sepsis, then choosing appropriate agents. Combinations of antibiotics are not always synergistic or even additive in effect. Multiagent therapy may have the untoward effect of predisposing to superinfection by yeast, fungi, or resistant organisms. Antibiotics should be used for a long enough period to produce an effect, but not long enough to allow for emergence of opportunistic or resistant organisms. Dosages must be adjusted based on serum concentrations when serum assays are available. In general prophylactic systemic antibiotics are indicated in only a few clinical situations including the immediate preoperative and postoperative periods associated with excision and autografting, and possibly in the early phases of burns in children. The penetration of systemic antibiotics into burn eschar remains an area not fully studied; hence, they cannot be the only therapeutic modality used to treat burn wound infection. Systemic dosages of antibiotics in burns will require alteration depending on the clinical status of the patient. The choice of agent requires a thorough knowledge of side effects, toxicity, and potential benefit. Above all, active surveillance and monitoring of the burned patient and the environment in which he or she is being treated is mandatory for effective treatment. The increasing number of new antimicrobial agents has presented a new dilemma to the practicing clinician because many of these agents have not been evaluated thoroughly in the burned population. With further studies, the armamentarium of the burn treatment team will inevitably increase. It is in this manner only that so many of the unanswered questions will be solved, and that infection will start to decline as the major cause of death in the burned population.

Infection with Acinetobacter in a burns unit

In recent months 17 patients on the Burns Unit at St Lawrence Hospital have been infected with Acinetobacter anitratus. We present 4 patients who have been extremely ill and in whom Acinetobacter was considered to have played a prominent role. We stress the importance of opportunistic infection in burns patients and antibiotic resistance in this organism.