Incidence and bacteriology of burn infections at a military burn center

Considerable advancements in shock resuscitation and wound management have extended the survival of burned patients, increasing the risk of serious infection. We performed a 6-year review of bacteria identification and antibiotic susceptibility records at the US Army Institute of Surgical Research Burn Center between January 2003 and December 2008. The primary goal was to identify the bacteria recovered from patients with severe burns and determine how the bacteriology changes during extended hospitalization as influenced by population and burn severity. A total of 460 patients were admitted to the burn ICU with 3507 bacteria recovered from 13,727 bacteriology cultures performed. The most prevalent organisms recovered were Acinetobacter baumannii (780), Pseudomonas aeruginosa (703), Klebsiella pneumoniae (695) and Staphylococcus aureus (469). A. baumannii was most often recovered from combat-injured (58%) and S. aureus the most frequent isolate from local (46%) burn patients. Culture recovery rate of A. baumannii and S. aureus was highest during the first 15 hospital days (73% and 71%); while a majority of P. aeruginosa and K. pneumoniae were recovered after day 15 (63% and 53%). All 4 pathogens were recovered throughout the course of hospitalization. A. baumannii was the most prevalent pathogen recovered from patients with total body surface area (TBSA) burns less than 30% (203) and 30–60% (338) while P. aeruginosa was most prevalent in patients with burns greater than 60% TBSA (292). Shifting epidemiology of bacteria recovered during extended hospitalization, bacteriology differences between combat-injured and local burn patients, and impact of % TBSA may affect patient management decisions during the course of therapy.     

Activity of topical antimicrobial agents against multidrug-resistant bacteria recovered from burn patients

Background

Topical antimicrobials are employed for prophylaxis and treatment of burn wound infections despite no established susceptibility breakpoints, which are becoming vital in an era of multidrug-resistant (MDR) bacteria. We compared two methods of determining topical antimicrobial susceptibilities.

Methods

Isolates of Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus (MRSA), extended spectrum beta-lactamase (ESBL) producing Klebsiella pneumoniae, and Acinetobacter baumanii-calcoaceticus (ABC) from burn patients were tested using broth microdilution and agar well diffusion to determine minimum inhibitory concentrations (MICs) and zones of inhibition (ZI). Isolates had systemic antibiotic resistance and clonality determined. MDR included resistance to antibiotics in three or more classes.

Results

We assessed 22 ESBL-producing K. pneumoniae, 20 ABC (75% MDR), 20 P. aeruginosa (45% MDR), and 20 MRSA isolates. The most active agents were mupirocin for MRSA and mafenide acetate for the gram-negatives with moderate MICs/ZI found with silver sulfadiazene, silver nitrate, and honey. MDR and non-MDR isolates had similar topical resistance. There was no clonality associated with resistance patterns.

Conclusion

Despite several methods to test bacteria for topical susceptibility, no defined breakpoints exist and standards need to be established. We recommend continuing to use silver products for prophylaxis against gram-negatives and mafenide acetate for treatment, and mupirocin for MRSA.     

Reducing the spread of Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus on a burns unit through the intervention of an infection control bundle

Methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii are major nosocomial pathogens in burns units. We investigated the impact of an infection control bundle on the incidence of nosocomial MRSA and A. baumannii in our burns unit, comparing a pre-intervention period (December 2006–August 2008) with an intervention period (September 2008–December 2009). The bundle comprised regular hydrogen peroxide vapour (HPV) disinfection of the rooms following discharge of patients colonized or infected by multidrug-resistant bacteria, pre-emptive cohort isolation of newly admitted patients before being proven culture negative, cohorting of colonized or infected patients, installation of two air disinfection systems in the corridors of the unit and improvement of material storage. We also investigated the microbiological efficacy of HPV disinfection by sampling the environment before and after HPV treatments. HPV disinfection eliminated pathogens from the environment and significantly reduced total bacterial surface counts, and total fungal air and surface counts, on both a unit and room scale. The incidence of nosocomial MRSA infection or colonization fell by 89.3% from 7.22 to 0.77 cases/1000 patient days (p < 0.0001) and A. baumannii fell by 88.8% from 6.92 to 0.77 cases/1000 patient days (p = 0.002) in the intervention period with no further outbreaks of these organisms occurring in this period. The infection control bundle resulted in a significant reduction in the incidence of nosocomial MRSA and A. baumannii in our burns unit and prevented further outbreaks of these organisms.     

Molecular epidemiology of methicillin-resistant Staphylococcus aureus in a burn unit from Brazil

Methicillin-resistant Staphylococcus aureus (MRSA) poses a threat for patients in burn units. Studies that mix epidemiological designs with molecular typing may contribute to the development of strategies for MRSA control. We conducted a study including: molecular characterization of Staphylococcal Chromosome Cassette mecA (SCCmec), strain typing with pulsed field gel electrophoresis (PFGE) and detection of virulence genes, altogether with a case–case–control study that assessed risk factors for MRSA and for methicillin-susceptible S. aureus (MSSA), using S. aureus negative patients as controls. Strains were collected from clinical and surveillance cultures from October 2006 through March 2009. MRSA was isolated from 96 patients. Most isolates (94.8%) harbored SCCmec type III. SCCmec type IV was identified in isolates from four patients. In only one case it could be epidemiologically characterized as “community-associated”. PFGE typing identified 36 coexisting MRSA clones. When compared to MSSA (38 isolates), MRSA isolates were more likely to harbor two virulence genes: tst and lukPV. Previous stay in other hospital and admission to Intensive Care Unit were independent risk factors for both MRSA and MSSA, while the number of burn wound excisions was significantly related with the former (OR = 6.80, 95%CI = 3.54–13.07). In conclusion, our study found polyclonal endemicity of MRSA in a burn unit, possibly related to importing of strains from other hospitals. Also, it pointed out to a role of surgical procedures in the dissemination of MRSA strains.     

Risk factors for acquisition of Methicillin-resistant Staphylococcus aureus among patients from a burn unit in Brazil

Methicillin-resistant Staphylococcus aureus (MRSA) is an important agent of colonization and infection in burn units. In order to identify risk factors for MRSA acquisition in a Brazilian burn unit, we performed two retrospective studies. In the first (“cohort” study), 175 patients who were not colonized with MRSA on admission were followed to assess risk factors for MRSA acquisition. In the second (“case–case–control” study), 143 individuals from the previous study who were negative for both MRSA and Methicillin-susceptible S. aureus (MSSA) on admission were followed. Case–control studies were performed to investigate risk factors for MRSA and MSSA acquisition. MRSA and MSSA were recovered from 75 and 23 patients, respectively. In the “cohort” study, only the number of wound excisions (Odds Ratio [OR] = 1.55, 95% Confidence Interval [CI] = 1.21–1.98, P = 0.001) was associated with MRSA acquisition. In the “case–case–control” study, burns involving head (OR = 3.43, 95%CI = 1.50–7.81, P = 0.003) and the number of wound excisions (OR = 1.83, 95%CI = 1.27–2.63, P = 0.001) were significant risk factors for MRSA. Burns involving perineum were negatively associated with MSSA acquisition (OR = 0.16, 95%CI = 0.03–0.75, P = 0.02). In conclusion, the acquisition of MRSA was related to the site of the burn and to the surgical manipulation of tissues, but not to the use of antimicrobials.     

Comparison of pathogens and antibiotic resistance of burn patients in the burn ICU or in the common burn ward

Background

This study aims to compare pathogens and their antibiotic resistances of burn patients from burn intensive care unit (ICU) or common burn ward. Of 2395 clinical samples from 63 patients in burn ICU, pathogens were detected in 1621 samples, in which 1203 strains (74.2%) were Gram negative bacteria, 248 strains (15.3%) were Gram positive bacteria, 170 strains (10.5%) were fungi. Top-4 microorganisms isolated from patients in burn ICU were Bauman's Acinetobacter (557, 34.4%), Pseudomonas aeruginosa (287.17.7%), Staphylococcus aureus (199, 12.3%) and Klebsiella pneumoniae (171, 10.5%). Of 512 clinical samples from 235 patients in common burn units, pathogens were detected in 373 samples, in which 189 (50.6%) strains were Gram negative bacteria, 150 strains (40.2%) were Gram positive bacteria, 34 strains (9.2%) were fungi. Top-4 microorganisms isolated from patients in common burn units were S. aureus (103, 27.6%), P. aeruginosa (46, 12.3%), K. pneumoniae (38, 10.2%) and Escherichia coli (32, 8.6%). Antibiotic resistance rates of pathogens isolated from clinical samples of burn patients from ICU was significantly higher than those from common units.

Conclusions

Pathogens and their antibiotic resistances are significantly different between burn ICU and common burn units. This finding has great implication for infection control in burn patients.     

Description of Streptococcus pneumoniae infections in burn patients

Background

Longer survival in burn patients has resulted in more infectious complications, typically with Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus. Although Streptococcus pneumoniae infections are common in the community and can cause nosocomial infections, the incidence and risk factors for pneumococcal infections in burn patients is unclear.

Methods

We performed an electronic retrospective chart review to collect rates of and risk factors for S. pneumoniae infections in patients with thermal burns from March 2003 through June 2008.

Results

Of the 1838 patients admitted to the burn center, 10 were infected (0.54% incidence). Patients presented with pneumonia (seven patients, 0.38% incidence) and bacteremia (three patients, 0.16% incidence) within a week of initial burn (median 1 day, range 0–8), often in the setting of bacterial co-infection (five patients). This group was mainly young males with median 28.8% total body surface area burns; 60% had concomitant inhalational injury. Most did not have traditional risk factors for pneumococcal infection but had objective signs of infection at time of positive culture and were treated with appropriate antibiotics. Two patients in this series died, although no mortality was attributed to S. pneumoniae.

Conclusions

Pneumococcal disease is not common in burn patients and generally occurs early on in hospitalization after burn making it more likely to be a community-acquired pathogen rather than nosocomial in the burn population. It should be considered in the setting of sepsis or new pulmonary infiltrates within a week after burn, but typical empiric antibiotics against the usual burn pathogens should be adequate to also treat for pneumococcal infection.     

Twenty-five year epidemiology of invasive methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered at a burn center

Over the past two decades, an epidemiologic emergence of methicillin-resistant Staphylococcus aureus (MRSA) infections has occurred from that of primarily hospital-associated to community-associated. This emergence change has involved MRSA of different pulsed-field types (PFT), with different virulence genes and antimicrobial resistance patterns. In this study we, evaluate the changes in PFT and antimicrobial resistance epidemiology of invasive MRSA isolates over 25 years at a single burn unit. Isolates were tested by pulsed-field gel electrophoresis (PFGE), broth microdilution antimicrobial susceptibility testing, and PCR for the virulence factors Panton–Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME), and the resistance marker staphylococcal chromosomal cassette mec (SCCmec). Forty isolates were screened, revealing stable vancomycin susceptibility MIC without changes over time but decreasing susceptibility to clindamycin and ciprofloxacin. The majority of PFGE types were MRSA USA800 carrying the SCCmec I element and USA100 carrying the SCCmec II element. No strains typically associated with community-associated MRSA, USA300 or USA400, were found. USA800 isolates were predominately found in the 1980s, USA600 isolates were primarily found in the 1990s, and USA100 isolates were found in the 2000s. The PVL gene was present in only one isolate, the sole USA500 isolate, from 1987. The virulence marker ACME was not detected in any of the isolates. Overall, a transition was found in hospital-associated MRSA isolates over the 25 years, but no introduction of community-associated MRSA isolates into this burn unit. Continued active surveillance and aggressive infection control strategies are recommended to prevent the spread of community-acquired MRSA to this burn unit.     

Characterisation of SCCmec elements in methicillin-resistant Staphylococcus aureus isolated from burn patients

Staphylococcus aureus is an important pathogen, especially in burn units all around the world. Because of the emergence of the β-lactam antibiotic-resistant strains since 1961, concern about the prevalence of methicillin-resistant S. aureus (MRSA) has increased in these units. Resistance to methicillin is mediated by penicillin-binding proteins (PBPs) that have enough affinity for binding to the β-lactam ring, but another kind of protein (PBP2α), which is encoded by the mecA gene, has a lower affinity for binding to these antibiotics. The mecA gene is transferred by SCCmec (staphylococcal cassette chromosome mec) as a mobile genetic element, exclusively found in the Staphylococcus genus. Identification of the frequency of the mecA gene, different SCCmec types and also its incidence may have benefit in surveillance prevention and control of MRSA strains in burn units. In this study, 40 S. aureus isolates were collected from patients hospitalised in Motahari burn center of Tehran, during 2012–2013. Conventional microbiological methods were applied and the confirmed isolates were stored at −20 °C for molecular polymerase chain reaction (PCR) tests. The antibiotic resistance pattern was performed by disc diffusion method and finally the different SCCmec types were determined by specific primers. During this research, 40 isolates of S. aureus were collected from burn patients, of which (37.5%) of the specimens belonged to female patients and 62.5% to male patients. The aetiology of the burn was classified as follows: open flame (35%), liquid (32.5%), chemical (5%) and other (27.5%). By a disc diffusion method, no resistance pattern was observed to vancomycin and fosfomycin. Based on a multiplex PCR assay, the five different SCCmec types were detected as: 47.5% type III, 25% type IV, 10% type V, 10% type II and 7.5% type I.     

Detection of VEB-1, OXA-10 and PER-1 genotypes in extended-spectrum β-lactamase-producing Pseudomonas aeruginosa strains isolated from burn patients

Resistance of Pseudomonas aeruginosa strains to the broad-spectrum cephalosporins may be mediated by the extended-spectrum β-lactamases (ESBLs). These enzymes are encoded by different genes located on either chromosomes or plasmids. This study aimed to investigate the prevalence of ESBLs and antimicrobial susceptibilities of P. aeruginosa isolated from burn patients in Tehran, Iran. Antimicrobial susceptibility of 170 isolates to cefpodoxime, aztreonam, ciprofloxacin, ofloxacin, ceftazidime, cefepime, imipenem, meropenem, cefotaxime, levofloxacin, piperacillin–tazobactam and ceftriaxone was determined by disc agar diffusion test. Polymerase chain reaction (PCR) amplification of the genes encoding OXA-10, PER-1 and VEB-1 was also performed. All isolates (100%) were resistant to ceftazidime, cefotaxime, cefepime and aztreonam. Imipenem and meropenem were the most effective anti-pseudomonal agents. The results revealed that 148 (87.05%) of the isolates were multidrug resistant and 67 (39.41%) of the isolates were ESBL positive. Fifty (74.62%), 33 (49.25%) and 21 (31.34%) strains among 67 ESBL-producing strains amplified bla_OXA-10, bla_PER-1 and bla_VEB-1 respectively.     

Pseudomonas aeruginosa bacteraemia in burns patients: Risk factors and outcomes

Introduction

We aimed to identify the risk factors for, and outcomes of Pseudomonas aeruginosa bacteraemia in adult burns patients.

Method

All adult burns patients who developed a Gram-negative bacteraemia over a period of 7 years were included. Retrospective data analysed included patient demographics, organisms cultured, antibiotic susceptibility patterns, isolation of P. aeruginosa in non-blood isolates, treatment, length of stay and mortality.

Results

Forty-three patients developed a Gram-negative bacteraemia over the study period, 12 of whom had Pseudomonas bacteraemia during the course of their admission. In eight patients (18.6%) P. aeruginosa was the first Gram-negative isolated. The only factor predicting P. aeruginosa bacteraemia as a first episode (compared to another Gram-negative) was prior isolation of Pseudomonas at other sites (wound sites, urine or sputum). Overall length of stay was less in patients who developed P. aeruginosa as a first episode, mainly because of increased mortality in this group. Prior non-blood isolates of P. aeruginosa could have correctly predicted the sensitivity pattern of the strain of P. aeruginosa organism in 75% of patients who did not receive appropriate initial antibiotics.

Conclusion

Prior colonisation with P. aeruginosa predicts P. aeruginosa in blood cultures, as opposed to other Gram-negative bacteria. Clinicians should have a high index of suspicion for P. aeruginosa bacteraemia where a septic burns patient has a prior history of non-blood P. aeruginosa cultures. Empirical antibiotic regimes based on the antibiotic-sensitivity patterns of previous non-blood P. aeruginosa isolates in each patient should be given at the time blood cultures are taken.     

Hyperbaric oxygen therapy in a mouse model of implant‐associated osteomyelitis

Implant associated osteomyelitis (OM) is difficult to treat with antibiotics, and outcomes remain poor. Some reports suggest that hyperbaric oxygen treatment is a safe and effective means of treating OM. We tested this hypothesis in a murine model. Clinical isolates of methicillin‐resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Klebsiella pneumoniae were used. The mice were infected with each of the three pathogens, treated with 100% oxygen at high pressure, hyperbaric oxygen (HBO), and monitored for the ability of HBO to prevent and/or clear the OM infection. Assessments included bacterial burden of the tibias and lesion scores, as well as receptor activator of NF‐κB ligand (RANKL) and myeloperoxidase (MPO) concentrations. HBO resulted in more severe lesion scores and higher RANKL and MPO concentrations for MRSA. A significant positive correlation was found between RANKL concentration and lesion score. No significant difference was found with HBO in P. aeruginosa infections and K. pneumoniae seems to either not infect bone well or get cleared before establishing an infection. The model is useful for studying OM infections caused by MRSA and P. aeruginosa, but HBO does not appear to be an efficacious treatment of an implant‐associated OM infection. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:203–208, 2012     

Distribution of Ambler class A, B and D β-lactamases among Pseudomonas aeruginosa isolates

Objectives

We determined the prevalence rate of classes A, B and D β-lactamases among extended-spectrum cephalosporin (ESC)-non-susceptible Pseudomonas aeruginosa clinical isolates from burned patients.

Methods

Disc susceptibility testing was performed on 156 P. aeruginosa isolates collected during 2010 at Prince Salman Hospital in Riyadh, Saudi Arabia. Phenotypic screening of ESBLs and MBLs in the isolates resistant to ceftazidime (MIC > 8 mg/L) was carried out. Genes encoding ESBLs and MBL were sought by PCR in ESBL- and MBL-producing isolates.

Results

The resistance rate to ceftazidime was 22.43%. The resistance rates for ESC-non-susceptible P. aeruginosa isolates to piperacillin, piperacillin/tazobactam, cefepime, aztreonam, imipenem, amikacin, gentamicin and ciprofloxacin were 100%, 71.14%, 88.57%, 48.57%, 70.0%, 82.5%, 87.5%, and 90.0% respectively. No resistance was detected to polymyxine B. The prevalence of ESBL and MBL in ESC-non-susceptible P. aeruginosa was 69.44% and 42.85%, respectively. The prevalence of structural genes for VEB-1, OXA-10 and GES ESBLs in P. aeruginosa was 68%, 56% and 20%, respectively. VIM gene was detected in 15 (100%) of MBL-producing isolates. OXA-10 like gene was concomitant with VEB, GES and/or VIM. Eight isolates harbored OXA-10 with VEB (imipenem MIC 6–8 mg/L), while five isolates harbored OXA-10 with VIM (imipenem MIC ≥ 32 mg/L) and one isolate contained OXA-10, VEB and GES (imipenem MIC 8 mg/L). PER was not detected in this study.

Conclusion

VEB-1 and OXA-10 are the predominant ESBL genes and bla_VIM is the dominate MBL gene in ESC-non-sensitive P. aeruginosa isolates in Saudi Arabia. VEB, OXA-10 and GES ESBLs have not been reported previously in Saudi Arabia and GES has not been reported previously in Middle East and North Africa.     

Antibiotic resistance and OXA-type carbapenemases-encoding genes in airborne Acinetobacter baumannii isolated from burn wards

The study was conducted to investigate drug resistance, OXA-type carbapenemases-encoding genes and genetic diversity in airborne Acinetobacter baumannii (A. baumannii) in burn wards. Airborne A. baumannii were collected in burn wards and their corridors using Andersen 6-stage air sampler from January to June 2011. The isolates susceptibility to 13 commonly used antibiotics was examined according to the CLSI guidelines; OXA-type carbapenemases-encoding genes and molecular diversity of isolates were analyzed, respectively. A total of 16 non-repetitive A. baumannii were isolated, with 10 strains having a resistance rate of greater than 50% against the 13 antibiotics. The resistance rate against ceftriaxone, cyclophosvnamide, ciprofloxacin, and imipenem was 93.75% (15/16), but no isolate observed to be resistant to cefoperazone/sulbactam. Resistance gene analyses showed that all 16 isolates carried OXA-51, and 15 isolates carried OXA-23 except No.15; but OXA-24 and OXA-58 resistance genes not detected. The isolates were classified into 13 genotypes (A-M) according to repetitive extragenic palindromic sequence PCR (REP-PCR) results and only six isolates had a homology ≥90%. In conclusion, airborne A. baumannii in the burn wards had multidrug resistance and complex molecular diversity, and OXA-23 and OXA-51 were dominant mechanisms for resisting carbapenems.     

Staphylococcus aureus bacteremia after thermal injury: The clinical impact of methicillin resistance

Objective

To evaluate the impact of methicillin resistance in Staphylococcus aureus bacteremia (SAB) on mortality and length of stay in burn patients.

Design

Retrospective cohort study.

Setting

A 750-bed tertiary care university hospital in Cologne, Germany.

Patients

Patients registered in the database of the burn intensive care unit (BICU) between 1989 and 2009 with complete data sets (n = 1688).

Results

Over the 21-year study period, 74 patients with SAB were identified; 33 patients had methicillin-resistant S. aureus (MRSA) and 41 methicillin-susceptible S. aureus (MSSA). Comparing the MRSA with the MSSA population the following parameters were significantly different in the univariate analysis: BMI (27.2 kg/m² vs. 23.6 kg/m²; P = 0.05), extent of deep partial thickness burns (17.8% vs. 9.0% of total body surface area; P = 0.007), antibiotic requirement on admission (45.5% vs. 22.0%; P = 0.046), median length of hospitalization prior SAB (24 days vs. 7 days; P < 0.001), packed red blood cells administration (47.6 units vs. 26.1 units; P = 0.003), intubation requirement (100% vs. 80.5%; P = 0.007), intubation period (43.5 days vs. 26.8 days; P = 0.008), catecholamine requirement (90.9% vs. 61.0%; P = 0.004), sepsis (60.6% vs. 34.1%; P = 0.035) and organ failures (81.8% vs. 39.0%; P < 0.001). Regarding outcome parameters, methicillin resistance was not significantly related with mortality (adjusted OR 1.55, 95% CI 0.56–4.28; P = 0.40) and length of BICU stay after SAB (Kaplan–Meier analysis log-rank test P = 0.32; Cox's proportional hazards regression HR 1.22, 95% CI 0.65–2.27, P = 0.535) in the univariate and multivariate analyses.

Conclusion

Our data suggest that methicillin resistance is not associated with significant increases in mortality and length of BICU stay among burn patients with SAB.     

Evaluations of bacterial contaminated full thickness burn wound healing in Sprague Dawley rats Treated with Tualang honey

Aim:

The effect of Tualang honey on wound healing in bacterial contaminated full-thickness burn wounds was evaluated in 36 male Sprague Dawley rats.

Materials and Methods:

The rats were randomly divided into three groups (n = 12/group). Three full-thickness burn wounds were created on each rat. Each group of rats was inoculated with a different organism in the burn wounds: Group A was inoculated with Pseudomonas aeruginosa, Group B was inoculated with Klebsiella pneumoniae and Group C was inoculated with Acinetobacter baumannii. One wound on each rat was dressed with either Tualang honey, Chitosan gel or Hydrofibre silver. Each wound size was measured on day 3, 6, 9, 12, 15, 18 and 21 of the study.

Results:

The mean wound size of the Tualang honey-treated wounds was not statistically different than that of the Chitosan gel or Hydrofibre silver-treated wounds when the wounds were compared throughout the entire experiment (P > 0.05). However, comparing the mean wound size on day 21 alone revealed that the Tualang honey-treated wounds were smaller in comparison to that of the Chitosan gel and Hydrofibre silver-treated groups.

Conclusions:

This study shows that topical application of Tualang honey on burn wounds contaminated with P. aeruginosa and A. baumannii gave the fastest rate of healing compared with other treatments.     

A prospective study of methicillin-resistant Staphylococcus aureus colonization in children scheduled for elective surgery

Background

Staphylococcus aureus is a major cause of surgical wound infections. To obtain contemporary data on S aureus, we performed a prospective study of colonization and infection in children scheduled for elective surgical procedures.

Methods

A nasal swab and clinical information were obtained at the presurgical outpatient visit. At operation, nasal and perianal swabs were obtained. S aureus were isolated and characterized.

Results

We enrolled 499 patients from June 2005 to April 2007. Wound classes were 1 (73%), 2 (22%), 3 (5%), and 4 (0.2%). Prophylactic antibiotics were administered for 153 (31%). Postoperative length of stay ranged from 0 (77%) to 6 days, with 19 (4%) staying 4 days or more. Screening cultures grew S aureus for 186 procedures (36.6%); of these, 141 were methicillin-resistant S aureus (MRSA) (76% of all staphylococcal cultures or 28% of all procedures). Most MRSA had Staphylococcal Chromosomal Cassette mec type II and resistance to clindamycin—typical for hospital-associated strains. There were 10 (2%) surgical site infections, including 4 methicillin-sensitive S aureus, 1 MRSA, 2 with no growth, and 2 with no cultures.

Conclusion

Methicillin-resistant S aureus colonization was common in asymptomatic children. Most strains appeared to be health care-associated and resistant to clindamycin. Wound infection rate remained low despite the high prevalence of staphylococcal colonization.     

Albumin reduces the antibacterial activity of polyhexanide-biguanide-based antiseptics against Staphylococcus aureus and MRSA

Background

Wound infection is one of the major complications in acute and chronic wound healing. Antiseptic solutions and wound irrigating agents are routinely used for therapy and prevention in healthcare today. Even if wound exudate contains total protein concentrations up to 9.3% and albumin concentrations up to 2.7% its influence to the antibacterial efficacy of these agents is barely investigated.

Materials and methods

This study analyzed the antibacterial effect of polyhexanide biguanide (PHMB) agents (PHMB-concentration 0.005–0.1%) against Staphylococcus aureus and methicillin-resistant-S. aureus (MRSA) after 2 min incubation in presents of albumin in different concentrations (0–3%) in a standardized quantitative suspension assay.

Results

A significant decrease of the antibacterial activity against S. aureus was shown for a PHMB-concentration of 0.005% from 0.3% albumin (p < 0.05), respectively highly significant from 0.75% (p < 0.01) on. Thereby the loss of antimicrobial effect was presented as a linear correlation to the rising concentration of albumin. Furthermore a reduction of the antibacterial activity against MRSA in comparison to S. aureus was presented, for albumin concentrations from 3% on highly significant (p < 0.01).

Conclusion

The study showed that albumin causes a significant decrease of the antibacterial potency of PHMB-based antiseptics. Furthermore a diminished potency of the investigated substances for MRSA-contaminated wounds must be taken in consideration. If in vitro experiments show a significant decrease of antibacterial efficacy in the presence of albumin a sufficient activity of PHMB-based agents in clinical practice, especially in cases of exuding wounds or dried-up exudates, cannot be expected.     

Evaluation of biofilm production and characterization of genes encoding type III secretion system among Pseudomonas aeruginosa isolated from burn patients

Pseudomonas aeruginosa is one of the common pathogenic causes of serious infections in burn patients throughout the world. Type III secretion toxins are thought to promote the dissemination of P. aeruginosa from the site of infection, the bacterial evasion of the host immune response and inhibition of DNA synthesis leading to host cell death. A total of 96 isolates of P. aeruginosa were collected from wound infections of burn patients, from April to July 2010. Antimicrobial susceptibility of the isolates were determined by disk agar diffusion method. Polymerase chain reaction (PCR)-based method was used for targeting the genes encoding the type III secretion toxins.     

Diagnosis of parapneumonic pleural effusion by polymerase chain reaction in children

Purpose

Most pleural effusions are associated with bacterial pneumonia, and the identification of the pathogen will assist the therapeutic decision. A specific method that is not affected by previous antibiotic therapy is sought to detect the main causative agents of pneumonia in infants and children (Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus). The aim of the present study was to compare the polymerase chain reaction (PCR) technique with standard culture methods in identifying bacterial infections in infants' and children's pleural effusion.

Methods

Samples obtained from pediatric patients (n = 37) with a diagnosis of pneumonia associated to pleural effusion, submitted to thoracentesis, were analyzed by PCR with specific primers.

Results

The PCR technique identified the presence of bacterial infection in a larger proportion (95.2%) than the standard culture method (33.3%) on complicated pleural effusion samples. The microorganism detection on uncomplicated pleural effusion samples was positive only by the PCR method (31.3%). The frequencies of microorganisms identified on complicated pleural effusion were 57.1% of all patients for methicillin-resistant Staphylococcus; 52.4%, S pneumoniae; 28.6%, S aureus; and 23.8%, H influenzae. The previous use of antibiotics interferes with standard culture method, but it did not interfere with the PCR results.

Conclusions

The molecular diagnosis by PCR method could improve the etiologic diagnosis and might help to guide the treatment of parapneumonic effusion in children.