Introduction of a conjugated vaccine against encapsulated Haemophilus influenzae type b (Hib) has led to a dramatic reduction of invasive Hib disease. However, an increasing incidence of invasive disease by H. influenzae non-type b has recently been reported. Non-type b strains have been suggested to be opportunists in an invasive context, but information on clinical consequences and related medical conditions is scarce. In this retrospective study, all H. influenzae isolates (n = 410) from blood and cerebrospinal fluid in three metropolitan Swedish regions between 1997 and 2009 from a population of approximately 3 million individuals were identified. All available isolates were serotyped by PCR (n = 250). We observed a statistically significant increase in the incidence of invasive H. influenzae disease, ascribed to non-typeable H. influenzae (NTHi) and encapsulated strains type f (Hif) in mainly individuals >60 years of age. The medical reports from a subset of 136 cases of invasive Haemophilus disease revealed that 48% of invasive NTHi cases and 59% of invasive Hif cases, respectively, met the criteria of severe sepsis or septic shock according to the ACCP/SCCM classification of sepsis grading. One-fifth of invasive NTHi cases and more than one-third of invasive Hif cases were admitted to intensive care units. Only 37% of patients with invasive non-type b disease had evidence of immunocompromise, of which conditions related to impaired humoral immunity was the most common. The clinical burden of invasive non-type b H. influenzae disease, measured as days of hospitalization/100 000 individuals at risk and year, increased significantly throughout the study period.

ABSTRACTThe proportions ofHaemophilus influenzaeresistant to ampicillin and other β-lactam antibiotics have been low in Sweden compared to other countries in the Western world. However, a near-doubled proportion of nasopharyngeal SwedishH. influenzaeisolates with resistance to β-lactams has been observed in the last decade. In the present study, the epidemiology and mechanisms of antimicrobial resistance ofH. influenzaeisolates 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 β-lactam were further analyzed in detail. We identified a significantly increased (P= 0.03) proportion of β-lactam-resistant invasiveH. influenzaeduring the study period, which was mainly attributed to a significant recent increase of β-lactamase-negative β-lactam-resistant isolates (P= 0.04). Furthermore, invasive β-lactamase-negative β-lactam-resistantH. influenzaeisolates 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 β-lactamase-negative ampicillin-resistant (BLNAR) isolates was identified, and it included isolates from all geographical areas. A truncated variant of a β-lactamase gene with a promoter deletion,blaTEM-1-PΔ dominated among the β-lactamase-positiveH. influenzaeisolates. Our results show that the proportions of β-lactam-resistant invasiveH. influenzaehave increased in Sweden in the last decade.

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.

An audit-based antimicrobial stewardship program profoundly reduced and altered antibtiotic use in a setting with low antimicrobial resistance with no negative effect on patient outcome