Nosocomial infections in burn patients: etiology, antimicrobial resistance, means to control

The aim of our study was to determine the etiology of nosocomial infections, their changes over a period of five years (2007-2011), and the measures for control of infections and antimicrobial resistance in the Burns Clinic of the N.I. Pirogov University Multi-Profile Hospital for Active Treatment and Emergency Medicine, Sofia, Bulgaria. The medical records for all the patients and the database of the "Clinical Microbiology and Surveillance of Infections" National Information System were reviewed and analyzed to identify the microbial pathogens isolated in our burns Clinic. The three most frequent nosocomial pathogens were S. aureus, A. baumannii and P. aeruginosa. In order to control effectively nosocomial infections, a system of anti-infective and anti- microbial resistance measures has been developed and routinely implemented in our Clinic since 2008. Since 2009, thanks to this system, there has been a significant decrease in the rates of multi-resistant Staphylococcus aureus strains. Although at present the incidence of the nosocomial infections in our burns clinic is lower than in neighboring countries, several important infection control issues still need to be solved. We mainly rely on updating and strengthening the existing anti-infective system in order to control the spread of multi-drug resistant organisms, such as A. baumannii, extended spectrum beta-lactamase-producing Enterobacteriaceae, and carbapenem-resistant P. aeruginosa.

Overview of molecular typing methods for outbreak detection and epidemiological surveillance

Typing methods for discriminating different bacterial isolates of the same species are essential epidemiological tools in infection prevention and control. Traditional typing systems based on phenotypes, such as serotype, biotype, phage-type, or antibiogram, have been used for many years. However, more recent methods that examine the relatedness of isolates at a molecular level have revolutionised our ability to differentiate among bacterial types and subtypes. Importantly, the development of molecular methods has provided new tools for enhanced surveillance and outbreak detection. This has resulted in better implementation of rational infection control programmes and efficient allocation of resources across Europe. The emergence of benchtop sequencers using next generation sequencing technology makes bacterial whole genome sequencing (WGS) feasible even in small research and clinical laboratories. WGS has already been used for the characterisation of bacterial isolates in several large outbreaks in Europe and, in the near future, is likely to replace currently used typing methodologies due to its ultimate resolution. However, WGS is still too laborious and time-consuming to obtain useful data in routine surveillance. Also, a largely unresolved question is how genome sequences must be examined for epidemiological characterisation. In the coming years, the lessons learnt from currently used molecular methods will allow us to condense the WGS data into epidemiologically useful information. On this basis, we have reviewed current and new molecular typing methods for outbreak detection and epidemiological surveillance of bacterial pathogens in clinical practice, aiming to give an overview of their specific advantages and disadvantages.

Serotype distribution and antimicrobial resistance of invasive Streptococcus pneumoniae isolates in Bulgaria before the introduction of pneumococcal conjugate vaccine

The 10-valent pneumococcal conjugate vaccine (PCV10) was introduced as a mandatory vaccine in Bulgaria in April 2010. We report on the serotype distribution and the antimicrobial resistance of 222 invasive Streptococcus pneumoniae isolates collected from all age groups before the introduction of PCV10. PCV7, PCV10, and PCV13 covered 43.7, 59.9, and 78.8% of all invasive pneumococcal strains, and 64.2, 79.1, and 89.6% of isolates involving children less than 5 years of age. Penicillin resistance was found in 30.1% of the isolates responsible for meningitis and in 5.0% of isolates responsible for other invasive infections. Overall, erythromycin resistance was found in 19.4% of all invasive strains. The erm(B) was the most prevalent pneumococcal macrolide resistance genotype (63.2%) and dual mechanisms of both genes the erm(B) and mef(E) were detected in 15.8% of 19 erythromycin resistant isolates during the period 2006-2010. The prevalence and spread of serotypes 19F, 6B, and 19A during the last period may have contributed to the high predominance of erm(B) genotype in comparison of mef genotype, which was predominant in our country among erythromycin-resistant isolates before 2005. Continuing surveillance is required after the recent introduction of PCV10 in order to observe future developments of any serotype changes in the Bulgarian population, as well as surveillance of antimicrobial susceptibility of invasive S. pneumoniae isolates.

Distribution of enterotoxin genes among carriage- and infection-associated isolates of Staphylococcus aureus

AIMS

To compare the distribution of genes encoding classical and newly described enterotoxins among Staphylococcus aureus, associated with carriage and infection.

METHODS AND RESULTS

Forty-five nasal isolates from carriers and 42 clinical isolates were included. The genes sea to see and seg to sei as well as sem, sen, seo and seu were tested using multiplex and conventional PCR. The most frequently found toxin genes were egc-related genes, in particular the combination seg and sei (n = 55, 63.1%), followed by sen and seu (n = 54, 62.1%), sem (n = 51, 58.6%) and seo (n = 48, 55.2%). Significant differences were found for seg and sei combination (33 of the nasal vs 22 of the infection isolates, P = 0.048) as well as for the genes sem (P = 0.004), sen (P = 0.029) and seo (P = 0.032). Regarding the classical toxin genes no significant differences between the two groups of isolates were found.

CONCLUSIONS

Significant differences between infection and carriage strains were found only for the egc-related genes, which were more common in the nasal isolates.

SIGNIFICANCE AND IMPACT OF THE STUDY

The egc-related enterotoxin genes seem to be more prevalent in carriage- than in infection-associated S. aureus isolates. The possible contribution of egc-related genes in determining the potential for nasal carriage requires further investigation.

First cases of infections caused by Panton-Valentine leukocidin positive community-acquired methicillin-resistant Staphylococcus aureus in Bulgaria

Infections caused by community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) have emerged as a major public health problem worldwide.

[Activity of vancomycin and teicoplanin against clinical isolates of Staphylococcus aureus in the period 1994-1999]

Since the emergence of the methicillin-resistant S. aureus (MRSA) in the 1960's, glycopeptides (Vancomycin and Teicoplanin) has been the drugs of choice and commonly the sole antimicrobial agents available for the treatment of serious MRSA and other Gram-positive infections. The emergence of S. aureus with intermediate vancomycin-resistance after 1997 threatens to return us to the era before the development of the antibiotics. Prevention of the further spread of S. aureus strains with intermediate and eventually with full glycopeptide resistance requires enhanced laboratory methods to detect resistance. A total of 361 S. aureus clinical isolates (177 MRSA and 184 MSSA) obtained from 1994 to 1999 in eleven Bulgarian hospitals located in geographically distinct areas of the country were enrolled in the study. Minimal inhibitory concentrations of Vancomycin and Teicoplanin were determined by agar-dilution method according to NCCLS recommendations. MIC50 and MIC90 for Vancomycin were 0.7 and 1 mg/ml, and for Teicoplanin--0.5 and 0.9 microgram/ml. All staphylococcal isolates showed sensitivity to Vancomycin and Teicoplanin. MICs of both glicopeptides against MRSA and MSSA did not differ significantly.