Agnes Anders

Fosfomycin Susceptibility in Carbapenem-Resistant Enterobacteriaceae from Germany

ABSTRACT Due to the increase in multidrug-resistant Enterobacteriaceae, the interest in older antimicrobial agents, like fosfomycin, has increased. In this study, we used agar dilution for testing susceptibilities to fosfomycin in a collection of 107 carbapenem-nonsusceptible Enterobacteriaceae isolates, of which 80 produced various types of carbapenemases, including KPC, VIM, NDM, and OXA-48. Overall, 78% of the strains had fosfomycin MICs of ≤32 mg/liter and were thus considered to be susceptible according to the current EUCAST breakpoint. The MIC50 and MIC90 were 8 mg/liter and 512 mg/liter, respectively. Escherichia coli strains had significantly lower fosfomycin MICs than the Klebsiella pneumoniae and Enterobacter cloacae strains. Furthermore, comparisons of the susceptibility testing methods, like Etest and disk diffusion, were performed against agar dilution as the reference method. Essential agreement between Etest and agar dilution was 78.9%, and categorical agreement between the two methods was 92.5%, with 20% very major errors and 2.6% major errors. Disk diffusion was studied with 50-μg and 200-μg fosfomycin disks, but no inhibition zone breakpoint that reduced very major and major errors to an acceptable level was found. Etest and disk diffusion showed poor agreement with fosfomycin agar dilution.

Identical MALDI TOF MS-derived peak profiles in a pair of isogenic SCCmec-harboring and SCCmec-lacking strains of Staphylococcus aureus.

MALDI-TOF MS-based peak differences in oxacillin-resistant Staphylococcus aureus and oxacillin-susceptible S. aureus isolates have been described previously. Unfortunately, these isolates were not isogenic with respect to their mecA gene. Ours is the first to use a SCCmec-harboring parent and a SCCmec-lacking daughter strain, with the same genetic background, to unequivocally rule out strain-specific protein peaks. We could not show differences in the peak profiles within the preset Biotyper settings used for MALDI-TOF-based identification in this pair of SCCmec-harboring parent and SCCmec-lacking daughter strains.

Lability of the pAA Virulence Plasmid in Escherichia coli O104:H4: Implications for Virulence in Humans

Background Escherichia coli O104:H4 that caused the large German outbreak in 2011 is a highly virulent hybrid of enterohemorrhagic (EHEC) and enteroaggregative (EAEC) E. coli. The strain displays “stacked-brick” aggregative adherence to human intestinal epithelial cells mediated by aggregative adherence fimbriae I (AAF/I) encoded on the pAA plasmid. The AAF/I-mediated augmented intestinal adherence might facilitate systemic absorption of Shiga toxin, the major virulence factor of EHEC, presumably enhancing virulence of the outbreak strain. However, the stability of pAA in the outbreak strain is unknown. We therefore tested outbreak isolates for pAA, monitored pAA loss during infection, and determined the impact of pAA loss on adherence and clinical outcome of infection. Methodology/Principal Findings E. coli O104:H4 outbreak isolates from 170 patients (128 with hemolytic uremic syndrome [HUS] and 42 with diarrhea without HUS) were tested for pAA using polymerase chain reaction and plasmid profiling. pAA-harboring bacteria in stool samples were quantified using colony blot hybridization, and adherence to HCT-8 cells was determined. Isolates from 12 (7.1%) patients lacked pAA. Analyses of sequential stool samples demonstrated that the percentages of pAA-positive populations in the initial stools were significantly higher than those in the follow-up stools collected two to eight days later in disease (P≤0.01). This indicates a rapid loss of pAA during infections of humans. The pAA loss was associated with loss of the aggregative adherence phenotype and significantly reduced correlation with HUS (P  = 0.001). Conclusions/Significance The pAA plasmid can be lost by E. coli O104:H4 outbreak strain in the human gut in the course of disease. pAA loss might attenuate virulence and diminish the ability to cause HUS. The pAA instability has clinical, diagnostic, epidemiologic, and evolutionary implications.

Description of the metallo-β-lactamase GIM-1 in Acinetobacter pittii

OBJECTIVES To characterize the mechanisms involved in the reduced carbapenem susceptibility of five Acinetobacter pittii strains isolated from different regions of Germany. METHODS The strains were analysed by susceptibility testing, phenotypic tests for metallo-β-lactamase production, sequencing of the integron structure and strain typing by PFGE, as well as multilocus sequence typing (MLST) and plasmid analysis by S1 restriction and hybridization. RESULTS Despite GIM-1 production, the MICs of imipenem were only 4 mg/L for four strains and some methods of phenotypic MBL detection failed. According to PFGE and MLST, the strains belonged to four different clones, but blaGIM-1 was present in identical integron structures in all strains and carried on plasmids of ∼60 kb. CONCLUSIONS For the first time, GIM-1 has been demonstrated in A. pittii. This resistance mechanism has previously been reported only in Enterobacteriaceae and Pseudomonas aeruginosa. As GIM-1 was found in strains with diverse clonal backgrounds, but encoded on plasmids of a similar size, further spread among Acinetobacter spp. seems possible. The detection of GIM-1 production might be challenging in some strains due to the low MICs of carbapenems.

Bacteribilia with resistant microorganisms after preoperative biliary drainage – the influence of bacteria on postoperative outcome

Abstract Background. In pancreatic surgery, preoperative biliary drainage (PBD) leads to bacteribilia. Whether positive bile duct cultures are associated with a higher postoperative morbidity might be related to the resistance of the species isolated from bile. Study. Intraoperative bile duct cultures were collected from all patients who underwent pancreatic surgery. Postoperative morbidity was analyzed according to the species and the resistance found on bile duct cultures. Results. Fifty-five percent (166/301) of patients had PBD, while 45% (135/301) underwent primary operation. PBD was associated with a positive bile duct culture in 87% (144/166) versus 21% (28/135) in patients without PBD (p = 0.001) and polymicrobial infections in 53% (88/166) versus 6% (8/135) (p = 0.001). Postoperative morbidity was 40% (121/301); mortality was 3% (9/301). PBD was not associated with morbidity and mortality, but resistant species on bile duct cultures lead to significantly more postoperative complications, 54% (25/46) versus 38% (96/255) (p = 0.033), with significantly more antibiotic therapies. Conclusion. PBD is associated with polymicrobial infections with resistant microorganisms, resulting in more postoperative complications. Since PBD cannot always be avoided, surgeons and gastroenterologists must be aware of their institutional surveillance data to identify patients at risk for postoperative complications.

Late Periprosthetic Joint Infection due to Staphylococcus lugdunensis Identified by Matrix-Assisted Laser Desorption/Ionisation Time of Flight Mass Spectrometry: A Case Report and Review of the Literature

Staphylococcus lugdunensis, member to the group of coagulase-negative staphylococci, is previously thought to be rarely isolated. Recently other staphylococci have been described, which were supposedly related to S. lugdunensis, such as Staphylococcus pseudolugdunensis and Staphylococcus pettenkoferi. To decrease the rate misidentifications, an accurate identification method, such as matrix-assisted laser desorption ionization time of flight mass spectrometry or molecular methods, should be used. S. lugdunensis is usually associated with severe infections similar to those caused by S. aureus. Moreover, it has been described that skin infections due to S. lugdunensis are severely underreported and could be also underreported in periprosthetic joint infections. Ours is the first case of a late periprosthetic infection of the hip due to S. lugdunensis, identified by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. A periprosthetic infection due to S. lugdunensis should be treated according to protocols of S. aureus periprosthetic infections, and therefore an accurate species identification is desirable.

The autolytic activity of the recombinant amidase of Staphylococcus saprophyticus is inhibited by its own recombinant GW repeats

The Aas (autolysin/adhesin of Staphylococcus saprophyticus) is a multifunctional surface protein containing two enzymatic domains an N-acetyl-muramyl-L-alanine amidase, an endo-beta-N-acetyl-D-glucosaminidase, and two different regions of repetitive sequences, an N-terminal and a C-terminal repetitive domain. The C-terminal repetitive domain is built up by the repeats R1, R2 and R3, which interconnect the putative active centers of the amidase and glucosaminidase. To investigate the influence of the C-terminal repeats and the N-terminal repeats on the amidase activity, the repetitive domains and fragments of them were cloned and expressed in Escherichia coli. The influence of the different fragments on the activity of the recombinant amidase of the Aas, consisting of the active center of the enzyme and repeat R1, was investigated in a turbidimetric microassay. The different fragments derived from the C-terminal repeats inhibited the amidase activity, while the N-terminal repeats did not influence the activity of the enzyme. The inhibiting activity increased with the number of GW repeats the recombinant fragment contained. Thus we conclude, that the C-terminal GW repeats and not the N-terminal repeats are necessary for the cell wall targeting and the autolytic function of the amidase.

Microbial Profile and Antimicrobial Susceptibility of Bacteria Found in Inflammatory Hidradenitis Suppurativa Lesions

Background: The role of bacterial colonization in hidradenitis suppurativa (HS) lesions is poorly understood. To date, data on the related microbial profile and especially on bacterial resistance rates are scarce. Methods: The results of bacterial cultures and susceptibility patterns of the isolated microorganisms obtained from deep portions of HS lesions from patients who underwent surgery at our HS Centre between 2010 and 2015 were retrospectively evaluated. Results: Analyses of 113 bacterial samples from 113 HS patients revealed bacterial growth in 95 samples (84.1%). Polymicrobial growth was found in 51 samples (45.1%). Coagulase-negative staphylococci and Staphylococcus aureus were the most commonly isolated bacteria, followed by Proteus mirabilis and Escherichia coli. Data on susceptibility testing were available for 68 samples, which yielded 129 isolates. The isolated strains were primarily resistant to penicillin G, followed by erythromycin, clindamycin and ampicillin. The highest effectiveness against isolates was observed for fosfomycin, imipenem, fluoroquinolones (moxifloxacin, ciprofloxacin, levofloxacin), and cotrimoxazole. Conclusions: Our findings on bacterial species and their topographical distribution revealed that the microbial flora in HS lesions reflects commensal flora of the skin. Due to the susceptibility rate and immunomodulatory and anti-inflammatory properties, cotrimoxazole may represent an alternative antibiotic agent and should be considered for therapy in HS patients.

Molecular epidemiology of VIM-1 producing Escherichia coli from Germany referred to the National Reference Laboratory

The distribution of carbapenemase genes in Escherichia coli strains isolated between September 2009 and May 2013 in Germany was investigated. Out of 192 isolates with carbapenemase production OXA-48 was found in 44.8%, VIM-1 in 18.8%, NDM-1 in 11.5% and KPC-2 in 6.8%. Patients with VIM-1 producing E. coli (n=36) differed from patients with OXA-48 by an older age, less frequent mention of travel history and an increased proportion of clinical over screening specimens. These data might indicate that introduction from abroad is of minor importance for VIM-1 producing E. coli compared to other carbapenemases. Multilocus sequence typing revealed that E. coli with VIM-1 were mostly multiclonal, emphasizing the role of horizontal gene transfer in its spread. Susceptibility testing of VIM-1 producing E. coli demonstrated aztreonam susceptibility in 55.6%. Among non-β-lactams susceptibility rates of >90% were observed for amikacin, tigecycline, colistin, fosfomycin and nitrofurantoin.

Listeria rhombencephalitis mimicking a demyelinating event in an immunocompetent young patient

Background: Listeriosis caused by listeria monocytogenes (LM) is a potentially lethal foodborne infection of the central nervous system (CNS) and the third most common cause of bacterial meningitis. Foods most commonly implicated are soft cheeses, raw or ready-to-eat meat and pre-processed foods. The incubation time is between 11 and 70 days. Rarely LM rhombencephalitis (RE) can occur, which typically has a biphasic course with non- specific prodromal symptoms like fever, malaise, fatigue, headache, nausea and vomiting followed by cranial nerve palsies, ataxia and hemi- or tetraparesis. Objective: To report a 31-year old immunocompetent female developing a severe abscessing RE caused by LM, which was initially assessed as a relapse after a clinically isolated syndrome (CIS). Methods: Case report. Results: Patients with CIS or multiple sclerosis, who present with brainstem symptoms should be evaluated carefully. The presence of clinical and paraclinical red flags in the diagnostic evaluation of a suspected CNS white matter disease should raise the awareness of clinicians for potential differential diagnoses.