Beta-lactam antibiotic concentrations in critically ill patients with standard and adjusted dosages: A prospective observational study.

INTRODUCTION: Antibiotic concentration target attainment is known to be poor in critically ill patients. Dose adjustment is recommended in patients with altered clearance, obesity and those with bacterial species with intermediate susceptibility. The aim of this study was to investigate the variation of antibiotic concentration in critically ill patients with standard or adjusted dosing regimens. METHODS: The concentration of three beta-lactam antibiotics used in the intensive care unit (ICU) setting, cefotaxime, piperacillin/tazobactam, and meropenem, was measured in patients with confirmed or suspected infection. Mid-dose and trough values were collected during a single dosing interval. The pharmacokinetic endpoints were a free antibiotic concentration that, during the whole dosing interval, was above MIC (100% ƒT > MIC, primary endpoint) or above four times MIC (100% ƒT > 4MIC, secondary endpoint). Non-species related MIC breakpoints were used (1 mg/L for cefotaxime, 8 mg/L for piperacillin/tazobactam, and 2 mg/L for meropenem). RESULTS: We included 102 patients (38 cefotaxime, 30 piperacillin/tazobactam, and 34 meropenem) at a single ICU, with a median age of 66 years. In total, 73% were males, 40% were obese (BMI ≥30) and the median SAPS 3 score was 63 points. Of all patients, 78 patients (76%) reached the primary endpoint (100%ƒT > MIC), with 74% for cefotaxime, 67% for piperacillin/tazobactam and 88% for meropenem. Target attainment for 100% ƒT > 4MIC was achieved in 40 (39%) patients, overall, with 34% for cefotaxime, 30% for piperacillin/tazobactam and 53% for meropenem. In patients with standard dose 71% attained 100%ƒT > MIC and 37% for 100%ƒT > 4MIC. All patients with reduced dose attained 100%ƒT > MIC and 27% attained 100% ƒT > 4MIC. In patients with increased dose 79% attained 100%ƒT > MIC and 48% 100%ƒT > 4MIC respectively. CONCLUSIONS: Beta-lactam antibiotics concentration vary widely in critically ill patients. The current standard dosing regimens employed during the study were not sufficient to reach 100% ƒT > MIC in approximately a quarter of the patients. In patients where dose adjustment was performed, the group with increased dose also had low target attainment, as opposed to patients with dose reduction, who all reached target. This suggests the need for further individualization of dosing where therapeutic drug monitoring can be an alternative to further increase target attainment.

A Cross-Sectional Cohort Study of Extended-Spectrum-Beta-Lactamase-Producing Enterobacterales in Patients with Traveler's Diarrhea.

Patients with traveler's diarrhea (TD) can acquire extended-spectrum-beta-lactamase (ESBL)-producing members of the Enterobacterales (EPE) during travel to areas of endemicity. The aim of the present study was to investigate the prevalence and characteristics of EPE carriage in travelers from southern Sweden who were sampled for bacterial diagnostics of TD compared to those of EPE carriage 10 years ago. Clinical samples sent for culture of common causes of bacterial enterocolitis, if the referral stated foreign travel, were included in the study. Antimicrobial susceptibility testing was done according to the EUCAST disk diffusion test method. EPE strains were subjected to whole-genome sequencing (WGS). Eighty-four of 303 patients carried a total of 92 ESBL-producing members of the Enterobacterales The overall prevalence of EPE in tested samples was thus 28%, compared to 24% 10 years earlier (P = 0.33). Among 86 strains available for WGS, 47 different sequence types (STs) were identified, and there were only 5 ST131 strains. Of the 79 Escherichia coli isolates, 76% carried at least one fim (type 1 fimbria) gene, 29% carried at least one pap (p-fimbriae) gene, and 43% were extraintestinal pathogenic E. coli (ExPEC) or uropathogenic E. coli (UPEC). Over half of the E. coli strains (57%) were intestinal pathogenic E. coli, most commonly enteroaggregative E. coli (EAEC) (33%), and enteroinvasive E. coli EIEC (22%). A relatively high proportion of patients with traveler's diarrhea carry EPE, but there was no significant increase compared to 10 years ago. Most E. coli strains were intestinal pathogenic strains. A comparatively high proportion of the strains were ExPEC/UPEC, many expressing the virulence genes pap and/or fim (This project was assigned ClinicalTrials.gov number NCT03866291.).

Bacteremia with ESBL-producing Enterobacterales is associated with IgG antibodies reacting with CTX-M-15 and/or CTX-M-27.

OBJECTIVES: The adaptive humoral immune response following clinical infection with extended spectrum beta-lactamase (ESBL)-producing Enterobacterales (EPE) has not been thoroughly investigated. The aim of this study was to investigate the presence of anti-CTX-M-15 and/or anti-CTX-M-27 IgG antibodies in bacteremia patients diagnosed with EPE compared to a control group consisting of patients suffering from bacteremia with third generation cephalosporin-susceptible Escherichia coli (3GCSE). METHODS: Patientswith EPE (n = 59) or 3GCSE (n = 42) bacteremia were recruited in this case control study in the Skåne County (South of Sweden). Sera were collected 1-26 months after bacteremia. Enzyme-linked immunosorbent assay (ELISA) was used for detection of specific IgG antibodies directed against recombinant beta-lactamases CTX-M-15 and CTX-M-27. The beta-lactamase resistance genes of the corresponding EPE blood isolates were determined by DNA sequencing. RESULTS: The majority (n = 47; 80 %) of the 59 EPE blood isolates carried blaCTX-M-15 or blaCTX-M-27 genes. IgG antibodies reacting to the corresponding CTX-M enzyme was seen in 28 % (13/47) of patients suffering from EPE-bacteremia, while antibodies were detected in only 9.5 % (4/42) of patients with 3GCSE (p = 0.03). Patients with EPE had a statistically significantly higher median Charlson comorbidity index and prevalence of renal disease (p = 0.01), compared to the 3GCSE control group. CONCLUSION: This study implies that EPE bacteremia can trigger production of IgG antibodies targeting ESBL. Further investigations are required to determine the functional role of anti-ESBL antibodies against EPE bacteremia.

Capsule Typing of Haemophilus influenzae by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry.

Encapsulated Haemophilus influenzae strains belong to type-specific genetic lineages. Reliable capsule typing requires PCR, but a more efficient method would be useful. We evaluated capsule typing by using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Isolates of all capsule types (a-f and nontypeable; n = 258) and isogenic capsule transformants (types a-d) were investigated. Principal component and biomarker analyses of mass spectra showed clustering, and mass peaks correlated with capsule type-specific genetic lineages. We used 31 selected isolates to construct a capsule typing database. Validation with the remaining isolates (n = 227) showed 100% sensitivity and 92.2% specificity for encapsulated strains (a-f; n = 61). Blinded validation of a supplemented database (n = 50) using clinical isolates (n = 126) showed 100% sensitivity and 100% specificity for encapsulated strains (b, e, and f; n = 28). MALDI-TOF mass spectrometry is an accurate method for capsule typing of H. influenzae.

A novel PBP3 substitution in Haemophilus influenzae confers reduced aminopenicillin susceptibility.

BACKGROUND: Identification and characterization of non-typeable Haemophilus influenzae (NTHi) with reduced susceptibility to ß-lactam antibiotics due to mutations in penicillin binding protein 3 (PBP3) is a clinical challenge. We analyzed a blood isolate, NTHi93-57485, that was categorized as aminopenicillin resistant but lacked key amino acid substitutions in PBP3 that have previously been associated with reduced aminopenicillin susceptibility. The significance of an alternative amino acid substitution (Y528H) in this isolate was examined. RESULTS: Site-directed mutagenesis of a ß-lactam susceptible H. influenzae (NTHi3655) was performed to introduce the Y528H substitution into wild-type ftsI (encoding for PBP3). Disc diffusion screening and broth microdilution determination of MICs for ß-lactam agents were done with the NTHi3655-PBP3Y528H mutant and were compared with the NTHi3655 wild-type as well as the original clinical isolate NTHi93-57485. Introduction of the Y528H substitution in NTHi3655 resulted in positive screening for ß-lactam resistance. MICs for aminopenicillins were increased in the mutant compared to the wild-type. However, the mutant remained susceptible to aminopenicillins according to EUCAST clinical breakpoints (assuming intravenous treatment) and the introduction of Y528H alone did not increase the resistance to the same level as NTHi93-57485. None of the isolates had frame shift insertions in the acrR gene regulating the AcrAB efflux pump. CONCLUSIONS: In parallel to the previously well-described PBP3-substitutions R517H and N526K, we demonstrate that Y528H confers reduced aminopenicillin susceptibility.

Benzylpenicillin versus wide-spectrum beta-lactam antibiotics as empirical treatment of Haemophilus influenzae-associated lower respiratory tract infections in adults; a retrospective propensity score-matched study.

There is consensus that definitive therapy for infections with H. influenzae should include antimicrobial agents with clinical breakpoints against the bacterium. In Scandinavia, benzylpenicillin is the recommended empirical treatment for community-acquired pneumonia (CAP) except in very severe cases. However, the effect of benzylpenicillin on H. influenzae infections has been debated. The aim of this study was to compare the outcomes of patients given benzylpenicillin with patients given wide-spectrum beta-lactams (WSBL) as empirical treatment of lower respiratory tract H. influenzae infections requiring hospital care. We identified 481 adults hospitalized with lower respiratory tract infection by H. influenzae, bacteremic and non-bacteremic. Overall, 30-day mortality was 9% (42/481). Thirty-day mortality, 30-day readmission rates, and early clinical response rates were compared in patients receiving benzylpenicillin (n = 199) and a WSBL (n = 213) as empirical monotherapy. After adjusting for potential confounders, empirical benzylpenicillin treatment was not associated with higher 30-day mortality neither in a multivariate logistic regression (aOR 2.03 for WSBL compared to benzylpenicillin, 95% CI 0.91-4.50, p = 0.082), nor in a propensity score-matched analysis (aOR 2.14, 95% CI 0.93-4.92, p = 0.075). Readmission rates did not significantly differ between the study groups, but early clinical response rates were significantly higher in the WSBL group (aOR 2.28, 95% CI 1.21-4.31, p = 0.011), albeit still high in both groups (84 vs 81%). In conclusion, despite early clinical response rates being slightly lower for benzylpenicillin compared to WSBL, we found no support for increased mortality or readmission rates in patients empirically treated with benzylpenicillin for lower respiratory tract infections by H. influenzae.

Considerable variation of trough ß-lactam concentrations in older adults hospitalized with infection-a prospective observational study.

In older adults, few studies confirm that adequate concentrations of antibiotics are achieved using current dosage regimens of intravenous ß-lactam antibiotics. Our objective was to investigate trough concentrations of cefotaxime, meropenem, and piperacillin in older adults hospitalized with infection. We included 102 patients above 70 years of age. Total trough antibiotic concentrations were measured and related to suggested target intervals. Information on antibiotic dose, patient characteristics, and 28-day outcomes were collected from medical records and regression models were fitted. Trough concentrations for all three antibiotics exhibited considerable variation. Mean total trough concentrations for cefotaxime, meropenem, and piperacillin were 6.5 mg/L (range 0-44), 3.4 mg/L (range 0-11), and 30.2 mg/L (range 1.2-131), respectively. When a target range of non-species-related breakpoint - 5× non-species-related breakpoint was applied, only 36% of patients had both values within the target range. Regression models revealed that severe sepsis was associated with varying concentration levels and increasing age and diminishing kidney function with high concentration levels. The study was not powered to demonstrate consequences in clinical outcomes. Conclusively, in older adults treated with cefotaxime, meropenem, or piperacillin-tazobactam, trough antibiotic concentrations varied considerably. Better predictors to guide dosing regimens of ß-lactam antibiotics or increased use of therapeutic drug monitoring are potential ways to address such variations.

Differential distribution of IgA-protease genotypes in mucosal and invasive isolates of Haemophilus influenzae in Sweden.

BACKGROUND: Several different IgA-proteases exist in Haemophilus influenzae. The variants have been suggested to play differential roles in pathogenesis, but there is limited information on their distribution in clinical isolates. The objective of this study was to investigate the distribution of IgA-protease genotypes in H. influenzae and assess the association between IgA-protease genotype and type of clinical infection. METHODS: We performed PCR-screening of the IgA-protease gene variants in two cohorts of clinical H. influenzae. The first cohort consisted of 177 isolates from individuals with respiratory tract infection in January 2010, 2011 and 2012. Information on age, gender and clinical infection was available in this cohort. The second cohort comprised 53 isolates, including NTHi from bloodstream, cerebrospinal fluid (CSF) and urogenital origin as well as encapsulated isolates respresenting all capsule types. We assessed associations between IgA protease genotype and clinical predictors using basic statistical tests of association as well as regression analysis. RESULTS: The igaB gene was found in 46% of isolates in the respiratory tract cohort, and no evident trend could be seen during the study years. However, the igaB gene was significantly less common among invasive isolates (19%), p = 0.003 (Fischer's exact test), even when encapsulated isolates were excluded (21%), p = 0.012. A significantly negative association between bacteraemia and igaB genotype remained after adjusting for covariates. We did not identify a significant association between IgA-protease gene variants and type of respiratory tract infection, but isolates with an igaA2 genotype were overrepresented in pre-school children. CONCLUSIONS: The distribution of IgA-protease gene variants in Swedish H. influenzae highlighted the widespread abundance of the igaB in isolates from cases of respiratory tract infection, but the igaB gene variant was significantly less common in invasive (bloodstream and CSF) isolates of H. influenzae compared with respiratory tract isolates.

The prevalence of ESBL-producing Enterobacteriaceae in a nursing home setting compared with elderly living at home: a cross-sectional comparison.

BACKGROUND: The aim of the study was to investigate the prevalence of faecal carriage of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae among residents living in nursing homes and to compare it with a corresponding group of elderly people living in their own homes. METHODS: A total of 160 persons participated in the study between February and April 2014, 91 were residents in nursing homes (n = 10) and the remaining 69 were elderly living in their own homes. In addition to performing faecal samples, all participants answered a standardized questionnaire regarding known risk factors for ESBL-carriage. RESULTS: There was no significant difference between the groups, as 10 of the 91 (11%) residents from nursing homes were ESBL-carriers compared with 6 of 69 (8,7%) elderly living in their own homes. There was no significant difference between the groups. The total prevalence was 10%. A univariate analysis revealed that the only studied risk factor significantly associated with ESBL-carriage was recent foreign travel (p = 0,017). All ESBL-positive isolates were Escherichia coli and there was a high degree of co-resistance to other antibiotics. All isolates (n = 17) were susceptible to imipenem and amikacin. CONCLUSION: Residents of nursing homes as well as elderly living in their own homes have high rates of faecal carriage of ESBL-producing bacteria. These findings may affect the choice of empirical antibiotic treatment of severe infections in older adults.

Reduction of Streptococcus pneumoniae in upper respiratory tract cultures and a decreased incidence of related acute otitis media following introduction of childhood pneumococcal conjugate vaccines in a Swedish county.

BACKGROUND: The effect of pneumococcal conjugate vaccines (PCV) on invasive pneumococcal disease is frequently reported, but the impact on upper respiratory tract infections in a clinical setting is less documented. Our aim in this 5-year observational study was to investigate serotype changes in a large number of Streptococcus pneumoniae upper respiratory tract isolates following sequential introduction of PCV7 and pneumococcal Haemophilus influenza protein D conjugate vaccine (PHiD-CV10) in a Swedish county. METHODS: All bacterial isolates from the upper respiratory tract (nasopharynx, sinus or middle ear fluid) from patients with respiratory tract infections referred to a clinical microbiology laboratory prior to (2 years 2007-2008; n = 1566) and after introduction of PCV (3 years 2011-2013; n = 1707) were prospectively collected. Microbiological findings were compared between the two periods, and information from clinical referrals was recorded in order to explore changes in incidence of pneumococcal acute otitis media (AOM). RESULTS: Pneumococcal serotypes covered by PHiD-CV10 decreased from 45 to 12 % prior to and after immunization (p < 0.001), respectively. Despite non-PHiD-CV10 serotypes increased from 49 to 80 %, a significant decline of 35 % in the absolute incidence of pneumocococal isolates (p < 0.001) was observed. Finally, the frequency of complicated AOM caused by S. pneumoniae decreased by 32 % (p < 0.001). CONCLUSIONS: After introduction of PCV in 2009, we have observed a significantly decreased number of pneumococcal isolates in the upper respiratory tract, a shift to non-PHiD-CV10 serotypes, and a reduction of complicated AOM. Our findings may have implications for future vaccine design.

A cost analysis of introducing an infectious disease specialist-guided antimicrobial stewardship in an area with relatively low prevalence of antimicrobial resistance.

BACKGROUND: Antimicrobial stewardship programs have been widely introduced in hospitals as a response to increasing antimicrobial resistance. Although such programs are commonly used, the long-term effects on antimicrobial resistance as well as societal economics are uncertain. METHODS: We performed a cost analysis of an antimicrobial stewardship program introduced in Malmö, Sweden in 20 weeks 2013 compared with a corresponding control period in 2012. All direct costs and opportunity costs related to the stewardship intervention were calculated for both periods. Costs during the stewardship period were directly compared to costs in the control period and extrapolated to a yearly cost. Two main analyses were performed, one including only comparable direct costs (analysis one) and one including comparable direct and opportunity costs (analysis two). An extra analysis including all comparable direct costs including costs related to length of hospital stay (analysis three) was performed, but deemed as unrepresentative. RESULTS: According to analysis one, the cost per year was SEK 161 990 and in analysis two the cost per year was SEK 5 113. Since the two cohorts were skewed in terms of size and of infection severity as a consequence of the program, and since short-term patient outcomes have been demonstrated to be unchanged by the intervention, the costs pertaining to patient outcomes were not included in the analysis, and we suggest that analysis two provides the most correct cost calculation. In this analysis, the main cost drivers were the physician time and nursing time. A sensitivity analysis of analysis two suggested relatively modest variation under changing assumptions. CONCLUSION: The total yearly cost of introducing an infectious disease specialist-guided, audit-based antimicrobial stewardship in a department of internal medicine, including direct costs and opportunity costs, was calculated to be as low as SEK 5 113.

Identification of Haemophilus influenzae Type b Isolates by Use of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry.

Haemophilus influenzae type b (Hib) is, in contrast to non-type b H. influenzae, associated with severe invasive disease, such as meningitis and epiglottitis, in small children. To date, accurate H. influenzae capsule typing requires PCR, a time-consuming and cumbersome method. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) provides rapid bacterial diagnostics and is increasingly used in clinical microbiology laboratories. Here, MALDI-TOF MS was evaluated as a novel approach to separate Hib from other H. influenzae. PCR-verified Hib and non-Hib reference isolates were selected based on genetic and spectral characteristics. Mass spectra of reference isolates were acquired and used to generate different classification algorithms for Hib/non-Hib differentiation using both ClinProTools and the MALDI Biotyper software. A test series of mass spectra from 33 Hib and 77 non-Hib isolates, all characterized by PCR, was used to evaluate the algorithms. Several algorithms yielded good results, but the two best were a ClinProTools model based on 22 separating peaks and subtyping main spectra (MSPs) using MALDI Biotyper. The ClinProTools model had a sensitivity of 100% and a specificity of 99%, and the results were 98% reproducible using a different MALDI-TOF MS instrument. The Biotyper subtyping MSPs had a sensitivity of 97%, a specificity of 100%, and 93% reproducibility. Our results suggest that it is possible to use MALDI-TOF MS to differentiate Hib from other H. influenzae. This is a promising method for rapidly identifying Hib in unvaccinated populations and for the screening and surveillance of Hib carriage in vaccinated populations.

Outbreak of a beta-lactam resistant non-typeable Haemophilus influenzae sequence type 14 associated with severe clinical outcomes.

BACKGROUND: During October 2011 several residents and staff members at a long-term care facility (LTCF) for elderly fell ill with respiratory symptoms. Several of the residents required hospitalization and one died. Non-typeable Haemophilus influenzae (NTHi) was identified as the causative pathogen. METHODS: A descriptive analysis of the outbreak and countermeasures was performed. For each identified bacterial isolate implied in the outbreak, standard laboratory resistance testing was performed, as well as molecular typing and phylogenetic analysis. RESULTS: The identified H. influenzae was beta-lactamase negative but had strikingly high MIC-values of ampicillin, cefuroxime and cefotaxime. All isolates displayed the same mutation in the ftsI gene encoding penicillin-binding protein (PBP) 3, and all but one were identified as sequence type 14 by Multilocus Sequence Typing (MLST). In total 15 individuals in connection to the LTCF; 8 residents, 6 staff members and one partner to a staff member were colonized with the strain. CONCLUSION: This report illustrates the existence of non-typeable H. influenzae with high virulence, and furthermore emphasizes the importance of continuous surveillance of possible outbreaks in health care facilities and prompt measures when outbreaks occur.

Comparative genomic analysis reveals distinct genotypic features of the emerging pathogen Haemophilus influenzae type f.

BACKGROUND: The incidence of invasive disease caused by encapsulated Haemophilus influenzae type f (Hif) has increased in the post-H. influenzae type b (Hib) vaccine era. We previously annotated the first complete Hif genome from a clinical isolate (KR494) that caused septic shock and necrotizing myositis. Here, the full genome of Hif KR494 was compared to sequenced reference strains Hib 10810, capsule type d (Hid) Rd Kw20, and finally nontypeable H. influenzae 3655. The goal was to identify possible genomic characteristics that may shed light upon the pathogenesis of Hif. RESULTS: The Hif KR494 genome exhibited large regions of synteny with other H. influenzae, but also distinct genome rearrangements. A predicted Hif core genome of 1390 genes was shared with the reference strains, and 6 unique genomic regions comprising half of the 191 unique coding sequences were revealed. The majority of these regions were inserted genetic fragments, most likely derived from the closely-related Haemophilus spp. including H. aegyptius, H. haemolyticus and H. parainfluenzae. Importantly, the KR494 genome possessed several putative virulence genes that were distinct from non-type f strains. These included the sap2 operon, aef3 fimbriae, and genes for kanamycin nucleotidyltranserase, iron-utilization proteins, and putative YadA-like trimeric autotransporters that may increase the bacterial virulence. Furthermore, Hif KR494 lacked a hisABCDEFGH operon for de novo histidine biosynthesis, hmg locus for lipooligosaccharide biosynthesis and biofilm formation, the Haemophilus antibiotic resistance island and a Haemophilus secondary molybdate transport system. We confirmed the histidine auxotrophy and kanamycin resistance in Hif by functional experiments. Moreover, the pattern of unique or missing genes of Hif KR494 was similar in 20 Hif clinical isolates obtained from different years and geographical areas. A cross-species comparison revealed that the Hif genome shared more characteristics with H. aegyptius than Hid and NTHi. CONCLUSIONS: The genomic comparative analyses facilitated identification of genotypic characteristics that may be related to the specific virulence of Hif. In relation to non-type f H. influenzae strains, the Hif genome contains differences in components involved in metabolism and survival that may contribute to its invasiveness.

Prevalence, distribution and transfer of small ß-lactamase-containing plasmids in Swedish Haemophilus influenzae.

OBJECTIVES: The ß-lactamase genes of Haemophilus influenzae are commonly positioned on large integrative and conjugative elements, but a group of blaTEM-carrying small plasmids (4000-6000 bp) with a common structural backbone have recently been characterized. In this study we investigated the epidemiological significance and potential for transfer of this group of small plasmids. METHODS: We developed a two-step PCR assay to screen for and type this group of resistance plasmids in H. influenzae. A large collection of respiratory isolates (n = 2845) from south Sweden, obtained from 2009 to 2011, as well as a collection of invasive Swedish H. influenzae from 1997 to 2010 (n = 310) was screened. The distribution of plasmid types among clinical isolates was investigated using multilocus sequence typing (MLST). RESULTS: In the collection, 15.8% of ß-lactamase-producing isolates and 1.4% of total isolates possessed a small plasmid with the signature structure. The plasmids were genetically conserved and widely spread geographically. MLST revealed that the spread of small plasmids occurred by both clonal expansion and horizontal transfer. In vitro experiments suggested that one plasmid type, pN223, can transfer ampicillin resistance to susceptible Escherichia coli. CONCLUSIONS: Small ß-lactamase-encoding plasmids constitute a significant mechanism for ß-lactam resistance in H. influenzae and can spread through clonal expansion of resistant clones as well as through horizontal plasmid transfer.

High incidence of septic shock caused by Streptococcus pneumoniae serotype 3--a retrospective epidemiological study.

BACKGROUND: More than 90 immunologically distinct serotypes of Streptococcus pneumoniae exist, and it is not fully elucidated whether the serotype is a risk factor for severity of invasive pneumococcal disease (IPD). Our hypothesis is that serotypes differ in their capacity to cause septic shock. METHODS: We performed a retrospective study in Southern Sweden based upon 513 patients with IPD in the pre-vaccine era 2006-2008. The serotype, co-morbidity, and sepsis severity were determined. Serotypes were compared to serotype 14 as a reference and grouped according to their invasive potential, that is, high (serogroups 1, 5 and 7), intermediate (serogroups 4, 9, 14 and 18) and, finally, low invasive potential (serogroups 3, 6, 8, 15, 19, 23 and 33). RESULTS: Patients with S. pneumoniae serotype 3 had significantly more often septic shock (25%, odds ratio (OR) 6.33 [95% confidence interval (CI) 1.59-25.29]), higher mortality (30%, OR 2.86 [CI 1.02-8.00]), and more often co-morbidities (83%, OR 3.82 [CI 1.39-10.54]) when compared to serotype 14. A significant difference in age and co-morbidities (p ≤ 0.001) was found when patient data were pooled according to the invasive potential of the infecting pneumococci. The median age and percentage of patients with underlying co-morbidities were 72 years and 79%, respectively, for serogroups associated with low invasiveness, 68 years and 61%, respectively, for serogroups with intermediate invasiveness, and, finally, 62 years and 48%, respectively, for serogroups with high invasiveness. No difference in sepsis severity was found between the three groups. CONCLUSIONS: S. pneumoniae serotype 3 more often caused septic shock compared to serotype 14. Our results support the hypothesis that serotypes with high invasiveness mainly cause IPD in younger patients with less co-morbidities. In contrast, serogroups with low and intermediate invasive potential mostly cause IPD in the elderly with defined co-morbidities, and thus can be considered as opportunistic.

Increase of ß-lactam-resistant invasive Haemophilus influenzae in Sweden, 1997 to 2010.

The proportions of Haemophilus influenzae resistant to ampicillin and other ß-lactam antibiotics have been low in Sweden compared to other countries in the Western world. However, a near-doubled proportion of nasopharyngeal Swedish H. influenzae isolates with resistance to ß-lactams has been observed in the last decade. In the present study, the epidemiology and mechanisms of antimicrobial resistance of H. influenzae isolates from blood and cerebrospinal fluid in southern Sweden from 1997 to 2010 (n = 465) were studied. Antimicrobial susceptibility testing was performed using disk diffusion, and isolates with resistance to any tested ß-lactam were further analyzed in detail. We identified a significantly increased (P = 0.03) proportion of ß-lactam-resistant invasive H. influenzae during the study period, which was mainly attributed to a significant recent increase of ß-lactamase-negative ß-lactam-resistant isolates (P = 0.04). Furthermore, invasive ß-lactamase-negative ß-lactam-resistant H. influenzae isolates from 2007 and onwards were found in higher proportions than the corresponding proportions of nasopharyngeal isolates in a national survey. Multiple-locus sequence typing (MLST) of this group of isolates did not completely separate isolates with different resistance phenotypes. However, one cluster of ß-lactamase-negative ampicillin-resistant (BLNAR) isolates was identified, and it included isolates from all geographical areas. A truncated variant of a ß-lactamase gene with a promoter deletion, bla(TEM-1)-PΔ dominated among the ß-lactamase-positive H. influenzae isolates. Our results show that the proportions of ß-lactam-resistant invasive H. influenzae have increased in Sweden in the last decade.

Haemophilus influenzae protein E binds to the extracellular matrix by concurrently interacting with laminin and vitronectin.

Nontypeable Haemophilus influenzae (NTHi) causes otitis media and is commonly found in patients with chronic obstructive pulmonary disease (COPD). Adhesins are important for bacterial attachment and colonization. Protein E (PE) is a recently characterized ubiquitous 16 kDa adhesin with vitronectin-binding capacity that results in increased survival in serum. In addition to PE, NTHi utilizes Haemophilus adhesion protein (Hap) that binds to the basement-membrane glycoprotein laminin. We show that most clinical isolates bind laminin and that both Hap and PE are crucial for the NTHi-dependent interaction with laminin as revealed with different mutants. The laminin-binding region is located at the N-terminus of PE, and PE binds to the heparin-binding C-terminal globular domain of laminin. PE simultaneously attracts vitronectin and laminin at separate binding sites, proving the multifunctional nature of the adhesin. This previously unknown PE-dependent interaction with laminin may contribute to NTHi colonization, particularly in smokers with COPD.

Necrotizing myositis and septic shock caused by Haemophilus influenzae type f in a previously healthy man diagnosed with an IgG3 and a mannose-binding lectin deficiency.

An increased incidence of infections by Haemophilus influenzae type f (Hif) has recently been suggested, but such infections have mainly been regarded as opportunistic. We present here a dramatic case of Hif necrotizing myositis and septic shock. A subsequently diagnosed IgG3 and mannose-binding lectin deficiency possibly contributed to the severe outcome.