Nosocomial infections

Efficiency of polymyxin B treatment against nosocomial infection: a systematic review and meta-analysis

Background

Some cohort studies have explored the effects and safety of polymyxin B (PMB) in comparison to other antibiotics for the treatment of nosocomial infections, yielding inconsistent results. This systematic review aims to explore the effectiveness and safety of PMB and compared it with other antibiotics.

Methods

A systematic literature search was conducted in PubMed, Embase, the Cochrane Library, and Web of Science, searching specific terms to identify quantitative cohort studies or RCTs that compared the effects of PMB with other antibiotics in terms of their efficacy and safety. The Newcastle-Ottawa Scale (NOS) was conducted to evaluate the risk of bias of observational studies. Odds ratios with 95% confidence intervals were used for outcome assessment. We evaluated heterogeneity using the I 2 test.

Results

A total of 22 observational trials were included in the analysis. The PMB group had a higher mortality rate compared to the control group (odds ratio: 1.84, 95% CI: 1.36-2.50, p<0.00001, I 2 = 73%). while, the ceftazidime-avibactam group demonstrated a distinct advantage with lower mortality rates, despite still exhibiting high heterogeneity (odds ratio 2.73, 95% confidence interval 1.59-4.69; p = 0.0003; I 2 = 53%). Additionally, the PMB group had a lower nephrotoxicity rate compared to the colistin group but exhibited high heterogeneity in the results (odds ratio 0.58, 95% CI 0.36-0.93; p = 0.02; I 2 = 73%).

Conclusion

In patients with nosocomial infections, PMB is not superior to other antibiotics in terms of mortality, specifically when compared to ceftazidime-avibactam. However, PMB demonstrated an advantage in terms of nephrotoxicity compared to colistin.

Bacterial and fungal colonisation of peripheral intravenous catheters in dogs and cats

OBJECTIVES

The purposes of this study were to determine the prevalence of intravenous catheter colonisation in a routine clinical setting, to identify pathogens involved and to explore factors associated with an increased risk of colonisation.

METHODS

A prospective study of 100 peripherally placed intravenous catheters from 13 cats and 78 dogs was conducted. The distal two-thirds were removed and submitted for bacterial and fungal cultures. Antimicrobial susceptibility of each isolate was determined.

RESULTS

Nineteen peripheral catheters were positive for microbiologic culture from 14 animals. Twenty organisms were isolated among which Staphylococcus species was the most common. Isolates displayed lower levels of resistance against the antimicrobial agents amoxicillin-clavulanate, cephalosporins and gentamicin than against other agents tested. Major risk factors predisposing to catheter-related colonisation included dextrose infusion, duration of catheter placement, local complications and immunosuppressive diseases or drugs.

CLINICAL SIGNIFICANCE

In a routine clinical setting, the prevalence of microbial colonisation of peripheral intravenous catheters is comparable to that found in an intensive care unit. However, consequences on morbidity and mortality rates differ.

Prospective randomized comparison of cefodizime versus cefuroxime for perioperative prophylaxis in patients undergoing coronary artery bypass grafting

The effects of cefodizime and cefuroxime on neutrophil phagocytosis and reactive oxygen production in 54 patients undergoing elective coronary artery bypass grafting were studied. Both drugs were administered twice at a dosage of 40 mg/kg of body weight (pre- and intraoperative). Phagocytic capacity was assessed by measuring the uptake of fluorescein isothiocyanate-labeled Escherichia coli and Staphylococcus aureus by flow cytometry. Reactive oxygen generation after phagocytosis was estimated by determining the amount of dihydrorhodamine 123 converted to rhodamine 123 intracellularly. In both groups the mean phagocytic ability for E. coli and S. aureus decreased during surgery (-21 and -8%, respectively, for the cefodizime group and -39 and -38%, respectively, for the cefuroxime group; P < 0.05 for all). In the cefodizime group a normalization of mean E. coli and S. aureus neutrophil phagocytosis was seen on day 5 (+9 and -4% compared to preoperative values; P > 0.35 for both), whereas in cefuroxime-treated patients phagocytic ability remained depressed (-37 and -31%; P < 0.04 for both). In both groups mean neutrophil reactive oxygen intermediate (ROI) production after E. coli and S. aureus phagocytosis increased during cardiopulmonary bypass (+44 and +83%, respectively, in the cefodizime group and +58 and +73%, respectively, in the cefuroxime group; P < 0.05 for all). One day after surgery E. coli- and S. aureus-driven neutrophil ROI production was not different from the preoperative values (-2 and +12%, respectively, for the cefodizime group and +7 and +15%, respectively, for the cefuroxime group; P > 0.15 for all). Postoperative serum levels of the C-reactive protein on days 2 and 7 were lower in cefodizime-treated patients (19 +/- 6 and 4 +/- 2 mg/liter versus 23 +/- 6 and 11 +/- 5 mg/liter; P < 0.05 for both). In addition to cefodizime's antimicrobial activity during perioperative prophylaxis, its use in coronary artery bypass grafting can prevent procedure-related prolonged postoperative neutrophil phagocytosis impairment.

Colonization of mechanical ventilation bags during use

BACKGROUND

Colonization of patients' mechanical ventilation bags was examined to evaluate two criteria (days in use and appearance) for replacing the disposable adapter that interfaces with the patient.

METHODS

Adapters used 1 to 2, 3 to 4 and 6 to 7 days formed groups I, II, and III, respectively (n = 29 to 67 per group). Another group (IA) contained 33 adapters used 1 to 2 days from patients intubated at least 7 days. Appearance of adapters was noted and adapters were swab cultured on nonselective medium.

RESULTS

Analysis of variance indicated a difference in log colony-forming units per adapter between groups I and II (p = 0.032), but colony-forming units per adapter varied widely. Group III had a lower mean colony-forming unit count than group II. Groups I and II differed in variables other than days of use, but these confounding variables were eliminated by substituting group IA for group I. When adapter appearance versus colonization was examined by chi 2 test, a significant difference was found between adapters that looked "clean" and those with precipitate or with mucus or blood.

CONCLUSIONS

For the subjects studied, colonization of adapters increased significantly between 1 to 2 and 3 to 4 days of use but varied widely. Appearance may be more useful than days in use as a criterion for changing adapters.

Anti-infective treatment in intensive care: the role of glycopeptides

Antibiotics are used in 80% of patients in the ICU, encouraging nosocomial infections with resistant organisms. If the antibiotic susceptibilities of the pathogen are known, a narrow-spectrum antibiotic is preferable to preserve the patient's resistance to colonization. However, treatment is often empirical and broad-spectrum combinations are commonly used. Gram-positive bacteraemia is associated with invasive monitoring or intravascular catheters. If the device cannot be removed easily, the glycopeptides are the only agents likely to be active against most strains of the commonest pathogen, the coagulase-negative staphylococcus. Long-stay patients are susceptible to infection with enterococci and methicillin-resistant Staphylococcus aureus, which are often resistant to all the usual agents other than glycopeptides. Vancomycin is long established, but is nephrotoxic, requires serum monitoring, must be administered as an infusion and can cause red man syndrome. Teicoplanin can be given as a single daily bolus without similar side-effects or monitoring. In deep-seated staphylococcal infection, the usual dose of teicoplanin is adequate if given in combination with other agents, but it may need to be doubled if used as monotherapy. Monitoring of the levels in the serum is helpful to ensure an adequate dose in patients with renal failure or in drug abusers, but is not needed to prevent toxicity.

Infections in critically ill patients: experience in MICU at a major teaching hospital

During a one-year period 105 patients suffering a total of 134 infectious episodes were studied prospectively in the medical intensive care unit (MICU). These patients included 54 male and 51 female patients, age ranging from 14 to 100 years (median = 54 years). The overall incidence of infection was 46.7%. Infections acquired in medical wards accounted for 47.8% of the total, followed by community-acquired infections in 27.0%, and MICU-acquired infections in 25.2% of the cases. The most frequent infections were pneumonia and septicaemia accounting for 88% of the total, whereas urinary tract (4.4%), gastrointestinal tract (5.0%), skin and wound infections (2.5%) constituted only 11.5%. The pathogens mainly involved were gram-negative rods, Staphylococcus spp. and Streptococcus pneumoniae. However, in community-acquired pneumonia, the major pathogens were gram-negative rods. In addition, Mycobacterium tuberculosis was an important cause of pneumonia in these patients. The majority of patients had a monoinfection; multiple pathogens were isolated in 11.9% of the episodes. The overall mortality was 46.7%. Several factors that influenced the mortality in these patients were analyzed. Early recognition of these factors may reduce morbidity and mortality.

Septic shock in critically ill patients: aetiology, management and outcome

Over a period of 28 months, 45 episodes of septic shock from 83 episodes of bacteraemia were studied prospectively to evaluate their clinical profile, management and outcome. Thirty-six patients were studied, the overall incidence of septic shock being 54.2%. Gram-negative organisms accounted for 23 (51.1%) of such episodes, Gram-positive 17 (37.8%), and three episodes were polymicrobial (6.7%). The organisms isolated most frequently were Staphylococcus epidermidis (17.8%), Pseudomonas aeruginosa (13.3%), Escherichia coli and Klebsiella sp. (each 11.1%). Coagulation abnormalities were detected in 32 episodes (78%) and disseminated intravascular coagulation (DIC) occurred in 11 of these with high mortality. The most common underlying conditions were respiratory, hepatic and renal failures. The majority of these patients received crystalloids, colloids, vasopressor drugs and blood. Swan-Ganz catheters (SGC) were inserted on eight occasions, the majority of times indicating a hyperdynamic circulatory response. The overall mortality was 40%, despite aggressive management and intensive care. The most important factor in reducing mortality is early detection of bacteraemia and prompt management of these patients.

Regulation of acute phase response after cardiopulmonary bypass by immunomodulation

The object of this prospective, randomized trial was to study the dysregulation effects of cardiopulmonary bypass on the synthesis pattern of interleukin-1, tumor necrosis factor, and interleukin-6, which have been identified as the key mediators of acute phase response. In addition, the counterregulation achieved by administration of indomethacin, which blocks the downregulating mediator prostaglandin E2, or indomethacin combined with thymopentin, which enhances T-lymphocytic reactivity, was investigated. Sixty patients who had undergone open heart operations were included in the study. These patients were divided into three groups: group A (n = 20) received both indomethacin and thymopentin, and group C (n = 20) served as control. In control patients interleukin-1 and tumor necrosis factor synthesis were suppressed postoperatively. This effect was significantly counteracted by indomethacin with no further improvement by adding thymopentin. Interleukin-6 synthesis increased in all groups. Although indomethacin treatment alone had little effect on this phenomenon, additional administration of thymopentin significantly reduced elevated interleukin-6 synthesis. Corresponding differences in clinical outcome could not be detected due to small patient numbers. This study was, however, able to demonstrate that an immunomodulatory therapy can influence alterations in immune mechanisms after cardiopulmonary bypass.

Surveillance of nosocomial fungal infections in a burn care unit

A survey was conducted to trace the source of nosocomial fungal infections in the burn care unit of Nehru Hospital, Chandigarh, India, by collection of samples from wounds of 25 severely burnt patients and their surroundings. The environmental sampling revealed predominant fungal contamination by dematiceous hyphomycetes, aspergilli, Penicillium, Fusarium and yeasts (Candida albicans, Candida tropicalis, Candida krusei, Candida parapsilosis), whereas the colonising or invading fungi from the patients were Aspergillus flavus and yeasts of the genus Candida (C. albicans, C. tropicalis, C. krusei, C. parapsilosis, Torulopsis glabrata). This study thus corroborates the more pathogenic potential of some of the environmental fungal isolates located in the vicinity of the immunocompromised patients and stresses the need for decontamination of the environment of the burn care unit.

Fibronectin is not detectable on the intact buccal epithelial surface of normal rats or humans

Fibronectin (FN) has been postulated to prevent gram-negative bacillary (GNB) colonization of the oropharynx by covering epithelial cell GNB receptors. We investigated the distribution of FN along the luminal surface of oropharyngeal epithelium in animals and humans. Examination of buccal epithelial biopsies obtained from normal rats revealed no luminal surface FN by either immunofluorescent or immunoperoxidase staining. Extraction of epithelial surface proteins and quantitation of FN by rocket immunoelectrophoresis and electrophoretic transfer to nitrocellulose followed by immunologic detection also detected no FN from normal animals' oropharyngeal biopsies. Buccal epithelial biopsies from three normal humans were examined for FN using electrophoretic transfer to nitrocellulose followed by immunologic detection, and no FN was demonstrable. Our results suggest that FN is not present on the oral epithelial surface of healthy rodents or humans, and that FN may not be involved in the pathogenesis of bacillary colonization.

Nosocomial pneumonia. A multivariate analysis of risk and prognosis

One hundred and twenty consecutive episodes of nosocomial pneumonia (NP) in 118 nonneutropenic adults admitted to a 1,000-bed teaching hospital were studied in order to investigate the prognosis and risk factors. The overall fatality rate was 36.6 percent. The identification of a "high-risk" microorganism (Pseudomonas aeruginosa, Enterobacteriaceae, and other Gram-negative bacilli, Streptococcus faecalis, Staphylococcus aureus, Candida sp, Aspergillus sp, and episodes of polymicrobial pneumonia), bilateral involvement on chest x-ray examination, the presence of respiratory failure, inappropriate antibiotic therapy, and age older than 60 years or an underlying condition ultimately or rapidly fatal were those factors selected by a stepforward logistic regression analysis as independently worsening the prognosis. A series of variables frequently quoted as predisposing to NP was determined to be either present or absent in the same 120 cases of NP and in an equal number of randomly selected control subjects. After adjusting for confounding, factors significantly predisposing to NP were tracheal intubation, depressed level of consciousness, underlying chronic lung disease, thoracic or upper abdominal surgery, prior episode of a large volume aspiration, and age older than 70 years. Since some of the factors influencing the risk or the prognosis of NP are amenable to medical intervention, a percentage of NP might be prevented and its prognosis can be improved.

Comparison of non-protected lower respiratory tract secretions and protected specimen brush samples in the diagnosis of pneumonia

The aim of this prospective study was to compare the results obtained with the non-protected lower respiratory tract secretions samples (LRS) with the protected specimen brushes (PSB) performed through a fiberoptic bronchoscope in mechanically ventilated patients, when pneumonia was suspected. The diagnosis of pneumonia was ultimately made at the end of the hospitalisation, in a double-blind manner by 2 members of the medical staff not aware of the bacteriologic results of LRS and PSB. LRS and PSB were performed in 24 patients. PSB culture was considered as positive at a level of 10(3) colony-forming units per milliliter (cfu/ml) microorganisms. Twenty-five samples from 24 patients were divided as follows: (1) LRS (-) and PSB (-) 5 samples: the clinical diagnosis of pneumonia was never established. (2) LRS (+) and PSB (+) 10 samples: the clinical diagnosis of pneumonia was always established, 2 microorganisms were involved 4 times and 1 microorganism 6 times. (3) LRS (+) and PSB (-) 10 samples: the clinical diagnosis pneumonia was retained in 3 with the possibility of false negative PSB. We conclude that (1) a negative LRS eliminated the diagnosis of pneumonia without PSB; (2) a positive LRS was not sufficient to diagnose pneumonia since PSB was negative in 50% of all LRS (+) cases; (3) the possibility of a false negative PSB must be kept in mind particularly in patients previously treated with antibiotics; (4) 2 microorganisms may be responsible for the pneumonia if the previously determined, as significant, bacteriological count (greater than or equal to 10(3) cfu/ml) appears to be accurate.

Adverse occurrences in the pediatric intensive care unit

This article is intended to provide a review of the literature describing adverse occurrences affecting children in the intensive care unit. In addition, information related to the care of critically ill children is inferred from studies of adult or neonatal patients. Finally, areas in need of future investigation are suggested.

Fungal colonization in patients with cancer of the upper respiratory tract

Fungal opportunistic infections are a danger for immunocompromised hosts, such as patients with malignancies, especially in a hospital environment. We studied a group of patients with solid tumors of the respiratory tract on admission and after twenty days of hospitalization. Colonization by moulds and/or yeasts was frequently found. Preventive measures should be applied to avoid colonization inside the hospital. The importance of overcrowding, sanitation and diet is pointed out.

Sources of fungal contamination in a burn-care unit

A microbiological study was carried out in the burn-care unit of the Centro Traumatologico Ortopedico of Turin (Italy) in order to detect the most important sources of fungal contamination in patients at high risk of infection. Identification of the fungi was carried out only for those of medical mycological interest, with the exclusion of the yeast isolates.

Bedside resuscitation bags: a source of bacterial contamination

Resuscitation bags at the bedside of 12 intubated ICU patients with known culture positive sputum were evaluated as possible reservoirs of pathogenic bacteria. As oxygen was constantly flowing into the bags, sampling of gas continuously emitted from the exhalation valve assembly was sampled to detect if a bacteria-laden aerosol was being created. Positive cultures were obtained from 75% of the valves and 25% of the aerosol samples. In those patients with gram-negative bacteria in their sputum, 71% of the valves and 29% of the gas samples were positive for the same organisms. Various methods to control this possible contributing factor to nosocomial infection in the ICU are discussed.

Treatment with aztreonam or tobramycin in critical care patients with nosocomial gram-negative pneumonia

During the course of one year, 47 critical care patients with gram-negative bacillary pneumonia at Millard Fillmore Hospital were randomly assigned to aztreonam or tobramycin therapy (two to one). Of these, 40 were fully evaluable for microbiologic and clinical response. All evaluable patients had gram-negative organisms in tracheal aspirate culture specimens and confirmed susceptibility of the organism to both study drugs. There was no difference between the two groups with respect to the percentage of patients who received concurrent antibiotics for gram-positive organisms. More than 60 percent of the patients received mechanical ventilation. Essentially, all had new lung infiltrates as shown by chest radiography, leukocytosis, recent onset of fever, and increased volume of purulent secretions. Half had multilobar pulmonary infiltrates. Their mean age was 73 years, with none under age 50. Most had chronic obstructive pulmonary disease, congestive heart failure, or both. By the prognostic nutritional index criteria, over 70 percent were nutritionally deficient at entry. The majority of infections were caused by Pseudomonas, Enterobacter, Klebsiella, and Escherichia coli. Aztreonam eradicated 92 percent of the causative gram-negative organisms, compared with 57 percent for tobramycin (p less than 0.05). Aztreonam produced a favorable clinical response (cure or improvement) in 93 percent of patients, compared with 50 percent for tobramycin (p less than 0.05). There were no differences in the minor adverse effects observed in the two treatment groups. Overall, aztreonam was superior to tobramycin for treatment of pneumonia due to susceptible gram-negative bacteria in these critical care patients.

[Lack of specificity of protected distal bronchial samples in the bacteriological diagnosis of nosocomial pneumonia caused by gram negative bacilli]

Lower respiratory tract secretions (LRS) were sampled during a two year period in patients undergoing mechanical ventilation using a method previously described by Matthew et al. Only those LRS positive for gram-negative bacilli were reported in this study. The patients were separated in two groups: those with nosocomial pneumonia due to gram-negative bacilli (NP+ group) and those without (NP- group). The species most often isolated from LRS were: Pseudomonas aeruginosa (25%), Proteus (20%), Escherichia coli (18%), Klebsiella pneumoniae (10%), Acinetobacter calcoaceticus (8%) and Haemophilus influenzae (7%). The spectrum of gram-negative species was not statistically different in either group of patients. The numbers of gram-negative bacilli isolated from each LRS were more important in the NP+ group (p less than 0.001), but so was the duration of mechanical ventilation before each LRS (p less than 0.01). In this group also, a specific bacteriological diagnosis with only one species was possible in 3 out of the 13 cases; a tentative diagnosis only was possible in 10 cases: in 6 cases, the responsibility of two (or more) species was suggested. The susceptibility to antibiotics of gram-negative bacilli isolated from LRS was moderate. A third generation cephalosporin together with amikacin seemed to be the best choice of antibiotics when no specific bacteriological diagnosis could be made with the LRS.