Antibiotic sensitivity still prevails in Norwegian blood culture isolates

Trends in antimicrobial resistance and empiric antibiotic therapy of bloodstream infections at a general hospital in Mid-Norway: a prospective observational study

Background

The occurrence of bloodstream infection (BSI) and antimicrobial resistance have been increasing in many countries. We studied trends in antimicrobial resistance and empiric antibiotic therapy at a medium-sized general hospital in Mid-Norway.

Methods

Between 2002 and 2013, 1995 prospectively recorded episodes of BSI in 1719 patients aged 16–99 years were included. We analyzed the antimicrobial non-susceptibility according to place of acquisition, site of infection, microbe group, and time period.

Results

There were 934 community-acquired (CA), 787 health care-associated (HCA) and 274 hospital-acquired (HA) BSIs. The urinary tract was the most common site of infection. Escherichia coli was the most frequently isolated infective agent in all three places of acquisition. Second in frequency was Streptococcus pneumoniae in CA and Staphylococcus aureus in both HCA and HA. Of the BSI microbes, 3.5% were non-susceptible to the antimicrobial regimen recommended by the National Professional Guidelines for Use of Antibiotics in Hospitals, consisting of penicillin, gentamicin, and metronidazole (PGM). In contrast, 17.8% of the BSI microbes were non-susceptible to cefotaxime and 27.8% were non-susceptible to ceftazidime.

Antimicrobial non-susceptibility differed by place of acquisition. For the PGM regimen, the proportions of non-susceptibility were 1.4% in CA, 4.8% in HCA, and 6.9% in HA-BSI (p < 0.001), and increasing proportions of non-susceptibility over time were observed in HA-BSI, 2.2% in 2002–2005, 6.2% in 2006–2009, and 11.7% in 2010–2013 (p = 0.026), mainly caused by inherently resistant microbes. We also observed increasing numbers of bacteria with acquired resistance, particularly E. coli producing ESBL or possessing gentamicin resistance, and these occurred predominantly in CA- and HCA-BSI.

Conclusions

Generally, antimicrobial resistance was a far smaller problem in our BSI cohort than is reported from countries outside Scandinavia. In our cohort, appropriate empiric antibiotic therapy could be achieved to a larger extent by replacing second- and third-generation cephalosporins with penicillin-gentamicin or piperacillin-tazobactam.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2210-6) contains supplementary material, which is available to authorized users.

A multi-centre prospective study of febrile neutropenia in Norway: Microbiological findings and antimicrobial susceptibility

The urgent need to treat presumptive bacterial or fungal infections in neutropenic patients has meant that initial therapy is empiric and based on the pathogens most likely to be responsible, and drug resistance. The traditional empirical treatment in Norway has been penicillin G and an aminoglycoside, and this combination has been criticized over recent y. We wished to analyse the microbiological spectrum and susceptibility patterns of pathogens causing bacteraemia in febrile neutropenic patients. This was a prospective multicentre study. During the study period of 2 y, a total of 282 episodes of fever involving 243 neutropenic patients was observed. In 34% of episodes bacteraemia was documented. Overall, 40% of the episodes were caused by Gram-positive organisms, 41% by Gram-negative organisms and 19% were polymicrobial. The most frequently isolated bacteria were Escherichia coli (25.6%), a- and non-haemolytic streptococci (15.6%), coagulase-negative staphylococci (12.4%) and Klebsiella spp. (7.4%). None of the Gram-negative isolates was resistant to gentamicin, meropenem, ceftazidime or ciprofloxacin. Only 5 coagulase-negative staphylococci isolates were resistant to both penicillin G and aminoglycoside. The overall mortality rate was 7%, and 1.2% due to confirmed bacteraemic infection.

Genetic variation among Staphylococcus aureus strains from Norwegian bulk milk

Strains of Staphylococcus aureus obtained from bovine (n = 117) and caprine (n = 114) bulk milk were characterized and compared with S. aureus strains from raw-milk products (n = 27), bovine mastitis specimens (n = 9), and human blood cultures (n = 39). All isolates were typed by pulsed-field gel electrophoresis (PFGE). In addition, subsets of isolates were characterized using multilocus sequence typing (MLST), multiplex PCR (m-PCR) for genes encoding nine of the staphylococcal enterotoxins (SE), and the cloverleaf method for penicillin resistance. A variety of genotypes were observed, and greater genetic diversity was found among bovine than caprine bulk milk isolates. Certain genotypes, with a wide geographic distribution, were common to bovine and caprine bulk milk and may represent ruminant-specialized S. aureus. Isolates with genotypes indistinguishable from those of strains from ruminant mastitis were frequently found in bulk milk, and strains with genotypes indistinguishable from those from bulk milk were observed in raw-milk products. This indicates that S. aureus from infected udders may contaminate bulk milk and, subsequently, raw-milk products. Human blood culture isolates were diverse and differed from isolates from other sources. Genotyping by PFGE, MLST, and m-PCR for SE genes largely corresponded. In general, isolates with indistinguishable PFGE banding patterns had the same SE gene profile and isolates with identical SE gene profiles were placed together in PFGE clusters. Phylogenetic analyses agreed with the division of MLST sequence types into clonal complexes, and isolates within the same clonal complex had the same SE gene profile. Furthermore, isolates within PFGE clusters generally belonged to the same clonal complex.

Prevalence and characterization of integrons in blood culture Enterobacteriaceae and gastrointestinal Escherichia coli in Norway and reporting of a novel class 1 integron-located lincosamide resistance gene

Background

Class 1 integrons contain genetic elements for site-specific recombination, capture and mobilization of resistance genes. Studies investigating the prevalence, distribution and types of integron located resistance genes are important for surveillance of antimicrobial resistance and to understand resistance development at the molecular level.

Methods

We determined the prevalence and genetic content of class 1 integrons in Enterobacteriaceae (strain collection 1, n = 192) and E. coli (strain collection 2, n = 53) from bloodstream infections in patients from six Norwegian hospitals by molecular techniques. Class 1 integrons were also characterized in 54 randomly selected multiresistant E. coli isolates from gastrointestinal human infections (strain collection 3).

Results

Class 1 integrons were present in 10.9% of the Enterobacteriaceae blood culture isolates of collection 1, all but one (S. Typhi) being E. coli. Data indicated variations in class 1 integron prevalence between hospitals. Class 1 integrons were present in 37% and 34% of the resistant blood culture isolates (collection 1 and 2, respectively) and in 42% of the resistant gastrointestinal E. coli. We detected a total of 10 distinct integron cassette PCR amplicons that varied in size between 0.15 kb and 2.2 kb and contained between zero and three resistance genes. Cassettes encoding resistance to trimethoprim and aminoglycosides were most common. We identified and characterized a novel plasmid-located integron with a cassette-bound novel gene (linF) located downstream of an aadA2 gene cassette. The linF gene encoded a putative 273 aa lincosamide nucleotidyltransferase resistance protein and conferred resistance to lincomycin and clindamycin. The deduced LinF amino acid sequence displayed approximately 35% identity to the Enterococcus faecium and Enterococcus faecalis nucleotidyl transferases encoded by linB and linB'

Conclusions

The present study demonstrated an overall low and stable prevalence of class 1 integron gene cassettes in clinical Enterobacteriaceae and E. coli isolates in Norway. Characterization of the novel lincosamide resistance gene extends the growing list of class 1 integron gene cassettes that confer resistance to an increasing number of antibiotics.

Susceptibility of skin and soft-tissue isolates of Staphylococcus aureus and Streptococcus pyogenes to topical antibiotics: indications of clonal spread of fusidic acid-resistant Staphylococcus aureus

Staphylococcus aureus (SA) isolates (n = 255) from outpatients with skin and soft-tissue infections were collected in 3 different areas in Norway. Group A streptococci (GAS, n = 68) were isolated from skin or pharyngotonsillar specimens from outpatients. Minimum inhibitory concentrations (MIC) of bacitracin, fusidic acid and mupirocin were tested using the E-test. Pulsed field gel electrophoresis (PFGE) patterns of fusidic acid-sensitive (FusS) and -resistant (FusR) SA were compared. All GAS isolates showed MIC of bacitracin of < or = 1.0 mg/l, of mupirocin of < or = 0.125 mg/l and of fusidic acid 1.0-4.0 mg/l. All the SA showed MIC of mupirocin < or = 0.5 mg/l and of bacitracin of > or = 2.0 mg/l, 91% with MIC > or = 16 mg/l. FusR was shown by 32.5% of the SA strains with similar prevalence rates in 3 different geographical areas of Norway. One particular PFGE pattern (type 1) was shown by 76% of the FusR SA. SA of type 1 belonged to phage group II and produced exfoliative toxins. Thus, the results demonstrated a high prevalence of FusR among SA causing skin infections and that this was mainly due to dissemination of clonally related FusR SA.

The use and resistance to antibiotics in the community

The frequency of resistance to antibiotics among common community-acquired pathogens, and the number of drugs to which they are resistant have been increasing worldwide. The relationship between antibiotic usage and resistance is strongly supported by data from several studies. Countries with the highest per capita antibiotic consumption have the highest resistance. The emergence of penicillin-resistant Streptococcus pneumoniae is related to high consumption of antibiotics in general, as well as to increased use of aminopenicillins and/or probably to wider use of oral cephalosporins. Increased consumption of macrolides, especially the long-acting ones, correlates significantly with the level of macrolide resistance of group A streptococci and S. pneumoniae while increased use of oral cephalosporins might be associated with the increase of beta-lactamase-producing strains of Moraxella catarrhalis. Trimethoprim/sulphamethoxazole resistance is strongly associated with resistance to penicillin. A rise in consumption of fluoroquinolones is consonant with a higher rate of resistance to quinolones of S. pneumoniae, Escherichia coli and other Gram-negative bacteria. Paediatric bacterial isolates are more often resistant to various antimicrobial agents than isolates from adult patients; this higher resistance rate may be due to more frequent antimicrobial treatments in children, and extensive child to child transmission. Reliable data on antimicrobial consumption and resistance should form a basis for national policies devised to reduce the resistance of microorganisms to antibiotics.