Emergence of multidrug resistance among Haemophilus parainfluenzae from respiratory and urogenital samples in Barcelona, Spain.

Haemophilus parainfluenzae (HPAR) is a Gram-negative bacterium that can become an opportunistic urogenital pathogen. Recently, multidrug resistant (MDR) strains have emerged. We aim to analyse the epidemiology of HPAR at Hospital Universitari de Bellvitge between 2013 and 2017 to determine its putative role in sexually transmitted infections (STI). Strains were classified by sample origin, and antimicrobial susceptibility was performed by disk-diffusion tested on Mueller-Hinton Fastidious. MDR was defined as the resistance of the antimicrobial to three or more antibiotic class. Molecular typing was performed by pulsed-field gel electrophoresis (PFGE) after restriction with SmaI and Cfr9I. We classified 944 HPAR isolates as being of urogenital (n = 175; 18.5%), respiratory (n = 719; 76.2%), or other (n = 50; 5.3%) origins. Among the urogenital isolates, 50 (28.6%) were MDR, which was significantly higher than that found in respiratory samples (40/719; 5.6%; p < 0.01). The frequency of MDR increased progressively among urogenital samples from 13.3% (2013) to 33.3% (2017) (r = 0.8; p = 0.035). The resistance rates for all 944 episodes were significantly higher for cotrimoxazole (51.4%), tetracycline (46.3%), chloramphenicol (28.0%), ciprofloxacin (21.1%), and ampicillin (20.6%). After PFGE, no clonal relationship was found. Clinical charts were available for 40 symptomatic patients with MDR HPAR infections presenting mostly urethritis (n = 26; 65.0%). In all cases, symptoms were treated effectively with combination therapy. Furthermore, in 10 of those patients with urethritis, MDR HPAR was the only potential pathogen to be identified. The emergence of MDR HPAR is a matter of concern, and the detection as a single pathogen highlights its putative role as cause of STI.

Haemophilus parainfluenzae-related cellulitis of the penis following tearing of a short frenulum.

INTRODUCTION: Infectious cellulitis is a common disease, mostly affecting the lower extremities and the face but only rarely the genitalia. OBSERVATION: A 24-year-old male patient presented with acute erythematous edema of the penile shaft and foreskin present for 48hours. Gentle retraction of the foreskin revealed a short frenulum with a small area (2-3mm) of erosion. He had had unprotected genital and orogenital sex three days before with his usual female partner and reported tearing of the frenulum during intercourse. Ampicillin-sensitive Haemophilus parainfluenzae was isolated from the swab taken from the erosion of the frenulum. Clinical remission was obtained following oral administration of amoxicillin and clavulanic acid. DISCUSSION: We describe not only the first case of Haemophilus parainfluenzae-associated cellulitis of the penis but also the first report of penile cellulitis following erosion of a short frenulum during sexual intercourse.

Multisystem organ failure secondary to Haemophilus parainfluenzae infective endocarditis on an ICD lead: A case report.

Infection of implanted cardiac devices (ICD) is an unusual but life threatening event, rarely caused by Haemophilus parainfluenzae. While clinical presentation varies widely, infective endocarditis (IE) involving an ICD lead requires aggressive resuscitation and a multidisciplinary approach. We present a case of a 33-year-old intravenous drug user who presented in multisystem organ failure secondary to infective endocarditis on an ICD lead. This patient had a complicated hospital course requiring removal of her ICD, highlighting the dramatic presentation of this clinical state.

Anti-Haemophilus Activity of Selected Essential Oils Detected by TLC-Direct Bioautography and Biofilm Inhibition.

Essential oils (EOs) are becoming increasingly popular in medical applications because of their antimicrobial effect. Direct bioautography (DB) combined with thin layer chromatography (TLC) is a screening method for the detection of antimicrobial compounds in plant extracts, for example, in EOs. Due to their lipophilic character, the common microbiological assays (etc. disk diffusion) could not provide reliable results. The aim of this study was the evaluation of antibacterial and anti-biofilm properties of the EO of cinnamon bark, clove, peppermint, thyme, and their main components against Haemophilus influenzae and H. parainfluenzae. Oil in water (O/W) type Pickering nano-emulsions stabilized with silica nanoparticles from each oil were prepared to increase their water-solubility. Samples with Tween80 surfactant and absolute ethanol were also used. Results showed that H. influenzae was more sensitive to the EOs than H. parainfluenzae (except for cinnamon bark oil). In thin layer chromatography-direct bioautography (TLC-DB) the ethanolic solutions of thyme oil presented the best activity against H. influenzae, while cinnamon oil was the most active against H. parainfluenzae. Pickering nano-emulsion of cinnamon oil inhibited the biofilm formation of H. parainfluenzae (76.35%) more efficiently than samples with Tween80 surfactant or absolute ethanol. In conclusion, Pickering nano-emulsion of EOs could inhibit the biofilm production effectively.

Haemophilus parainfluenzae Strain ATCC 33392 Forms Biofilms In Vitro and during Experimental Otitis Media Infections.

Haemophilus parainfluenzae is a nutritionally fastidious, Gram-negative bacterium with an oropharyngeal/nasopharyngeal carriage niche that is associated with a range of opportunistic infections, including infectious endocarditis and otitis media (OM). These infections are often chronic/recurrent in nature and typically involve bacterial persistence within biofilm communities that are highly resistant to host clearance. This study addresses the primary hypothesis that H. parainfluenzae forms biofilm communities that are important determinants of persistence in vivo The results from in vitro biofilm studies confirmed that H. parainfluenzae formed biofilm communities within which the polymeric matrix was mainly composed of extracellular DNA and proteins. Using a chinchilla OM infection model, we demonstrated that H. parainfluenzae formed surface-associated biofilm communities containing bacterial and host components that included neutrophil extracellular trap (NET) structures and that the bacteria mainly persisted in these biofilm communities. We also used this model to examine the possible interaction between H. parainfluenzae and its close relative Haemophilus influenzae, which is also commonly carried within the same host environments and can cause OM. The results showed that coinfection with H. influenzae promoted clearance of H. parainfluenzae from biofilm communities during OM infection. The underlying mechanisms for bacterial persistence and biofilm formation by H. parainfluenzae and knowledge about the survival defects of H. parainfluenzae during coinfection with H. influenzae are topics for future work.

Haemophilus parainfluenzae as a marker of the upper respiratory tract microbiota changes under the influence of preoperative prophylaxis with or without postoperative treatment in patients with lung cancer.

BACKGROUND: Haemophili are representative microbiota of the upper respiratory tract. The aim of this study was to assess the effects of perioperative antimicrobial prophylaxis and/or postoperative treatment on Haemophilus parainfluenzae prevalence, and antimicrobial sensitivity in short-term hospitalized patients with lung cancer who underwent surgery. RESULTS: Samples were collected from 30 short-term hospitalized patients with lung cancer and from 65 healthy people. The nasal and throat specimens were taken twice from each patient: before (EI, Examination I), on the fourth/fifth day (EII, Examination II) after surgery, and once from healthy people. The isolates identification and antimicrobial susceptibility were detected by routine diagnostic methods. H. parainfluenzae was found in throat specimens of 42/65 (64.6 %) healthy people, while in 19/30 (63.3 %) lung cancer patients in EI (p = 0.6203) and in 13/30 (43.3 %) ones in EII (p = 0.0106). Neither the disease itself nor short-term hospitalization with perioperative prophylaxis alone affected H. parainfluenzae prevalence in EII, while perioperative prophylaxis with postoperative treatment significantly decreased its colonization in EII. The differences in the number of patients colonized by Candida spp. in EI and in EII were observed (p = 0.0082).Totally, 23/58 (39.7 %) of H. parainfluenzae isolates were resistant mainly to beta-lactams; among 11 ampicillin-resistant isolates only 3 were beta-lactamase positive. CONCLUSIONS: The antimicrobial perioperative prophylaxis together with postoperative treatment may disturb the composition of the airways microbiota represented by H. parainfluenzae, in addition to selecting the resistant strains of bacteria and promoting yeasts colonization in lung cancer patients undergoing surgery.

Changes in the prevalence and biofilm formation of Haemophilus influenzae and Haemophilus parainfluenzae from the respiratory microbiota of patients with sarcoidosis.

BACKGROUND: Healthy condition and chronic diseases may be associated with microbiota composition and its properties. The prevalence of respiratory haemophili with respect to their phenotypes including the ability to biofilm formation in patients with sarcoidosis was assayed. METHODS: Nasopharynx and sputum specimens were taken in 31 patients with sarcoidosis (average age 42.6 ± 13), and nasopharynx specimens were taken in 37 healthy people (average age 44.6 ± 11.6). Haemophili were identified by API-NH microtest and by the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) system. Biofilm was visualised by crystal violet staining and confocal scanning laser microscopy (CSLM). The statistical analysis was performed with Statgraphics Plus for Windows. RESULTS: In total, 30/31 patients with sarcoidosis and 31/37 healthy people were colonized by Haemophilus influenzae (6/30 vs. 1/31) and Haemophilus parainfluenzae (28/30 vs. 31/31) in the nasopharynx. The overall number of nasopharyngeal haemophili isolates was 59 in patients with sarcoidosis and 67 in healthy volunteers (H. influenzae 6/59 vs. 1/67, P = 0.05; H. parainfluenzae 47/59 vs. 65/67, P = 0.0032). Moreover, the decreased number of H. parainfluenzae biofilm-producing isolates was shown in nasopharyngeal samples in patients with sarcoidosis as compared to healthy people (19/31 vs. 57/65, P = 0.006), especially with respect to isolates classified as strong and very strong biofilm-producers (8/31 vs. 39/65, P = 0.002). CONCLUSIONS: The obtained data suggest that the qualitative and quantitative changes within the respiratory microbiota concerning the overall prevalence of H. influenzae together with the decreased number of H. parainfluenzae strains and the decreased rate of H. parainfluenzae biofilm-producing isolates as compared to healthy people may be associated with sarcoidosis.

An unusual presentation of subacute Haemophilus parainfluenzae endocarditis in a low-risk woman treated by minimally invasive mitral valve repair: a case report.

BACKGROUND: HACEK endocarditis is usually insidious and can often be difficult to diagnose due to the slow-growing nature of the organisms. This report presents our experience in treating a patient with Haemophilus parainfluenzae endocarditis. CASE PRESENTATION: We describe the case of a previously fit and well 23 year-old woman who presented to her local emergency department with a four-week history of persistent febrile illness. She had associated nausea, vomiting, and lethargy. This was preceded by an episode of mucopurulent rhinorrhoea. She was treated empirically with oral amoxicillin for a putative diagnosis of rhinosinusitis. Initially, her symptoms abated, however, she was readmitted with high fevers and a new pansystolic murmur. Transthoracic echocardiography revealed a large, mobile, echogenic mass, tethered to the posterior mitral valve leaflet (PMVL) and mild mitral regurgitation (MR). On examination, she had multiple non-tender, erythematous macules on the plantar surface of her feet, consistent with Janeway lesions. Two separate blood cultures grew H. parainfluenzae. Infectious diseases recommended a four-week course of intravenous ceftriaxone. Transesophageal echocardiography demonstrated a perforation within the P3 segment of the PMVL. Subsequently, the patient underwent mitral valve repair surgery with an uneventful recovery. CONCLUSIONS: Our case highlights the importance of promptly diagnosing HACEK endocarditis. A prolonged course of antibiotic therapy can be lifesaving, and surgery is often necessary to address complications such as perforation within the mitral valve leaflets. In our patient, we were able to perform a sliding P2 leaflet plasty for good quality repair of the mitral valve, through a minimally invasive right anterior thoracotomy.

Genetic Adaptation and Acquisition of Macrolide Resistance in Haemophilus spp. during Persistent Respiratory Tract Colonization in Chronic Obstructive Pulmonary Disease (COPD) Patients Receiving Long-Term Azithromycin Treatment.

Patients with chronic obstructive pulmonary disease (COPD) benefit from the immunomodulatory effect of azithromycin, but long-term administration may alter colonizing bacteria. Our goal was to identify changes in Haemophilus influenzae and Haemophilus parainfluenzae during azithromycin treatment. Fifteen patients were followed while receiving prolonged azithromycin treatment (Hospital Universitari de Bellvitge, Spain). Four patients (P02, P08, P11, and P13) were persistently colonized by H. influenzae for at least 3 months and two (P04 and P11) by H. parainfluenzae. Isolates from these patients (53 H. influenzae and 18 H. parainfluenzae) were included to identify, by whole-genome sequencing, antimicrobial resistance changes and genetic variation accumulated during persistent colonization. All persistent lineages isolated before treatment were azithromycin-susceptible but developed resistance within the first months, apart from those belonging to P02, who discontinued the treatment. H. influenzae isolates from P08-ST107 acquired mutations in 23S rRNA, and those from P11-ST2480 and P13-ST165 had changes in L4 and L22. In H. parainfluenzae, P04 persistent isolates acquired changes in rlmC, and P11 carried genes encoding MefE/MsrD efflux pumps in an integrative conjugative element, which was also identified in H. influenzae P11-ST147. Other genetic variation occurred in genes associated with cell wall and inorganic ion metabolism. Persistent H. influenzae strains all showed changes in licA and hgpB genes. Other genes (lex1, lic3A, hgpC, and fadL) had variation in multiple lineages. Furthermore, persistent strains showed loss, acquisition, or genetic changes in prophage-associated regions. Long-term azithromycin therapy results in macrolide resistance, as well as genetic changes that likely favor bacterial adaptation during persistent respiratory colonization. IMPORTANCE The immunomodulatory properties of azithromycin reduce the frequency of exacerbations and improve the quality of life of COPD patients. However, long-term administration may alter the respiratory microbiota, such as Haemophilus influenzae, an opportunistic respiratory colonizing bacteria that play an important role in exacerbations. This study contributes to a better understanding of COPD progression by characterizing the clinical evolution of H. influenzae in a cohort of patients with prolonged azithromycin treatment. The emergence of macrolide resistance during the first months, combined with the role of Haemophilus parainfluenzae as a reservoir and source of resistance dissemination, is a cause for concern that may lead to therapeutic failure. Furthermore, genetic variations in cell wall and inorganic ion metabolism coding genes likely favor bacterial adaptation to host selective pressures. Therefore, the bacterial pathoadaptive evolution in these severe COPD patients raise our awareness of the possible spread of macrolide resistance and selection of host-adapted clones.

Infected Left Atrial Myxoma Presenting Without Bacterial Growth on Blood Cultures: A Case Report.

Although cardiac myxoma is one of the most common types of benign cardiac tumors, infected cardiac myxoma is very infrequent. The diagnosis of infected cardiac myxoma may be challenging because the presenting symptoms are non-specific and established management guidelines are lacking. This report describes a 39-year-old woman with a 5-month history of uncontrolled fever, chills, and myalgia who was diagnosed with myxoma and underwent mass excision. Although blood and urine cultures were negative for growing bacteria, a pathologic examination showed that the excised mass was a left atrial myxoma, with pan-bacterial polymerase chain reaction (PCR) of the surgical specimen revealing Haemophilus parainfluenzae at 99.87%, resulting in a diagnosis of infected cardiac myxoma. Laboratory tests, such as PCR, may supplement culture results in the diagnosis of infected cardiac myxoma.

An Unusual Case of Haemophilus parainfluenzae Endocarditis in a Young Patient With Crohn's Disease.

We present a rare case of infective endocarditis (IE) associated with Haemophilus parainfluenzae in a 40-year-old male patient with a history of Crohn's Disease (CD). A complete workup, including an echocardiogram and blood cultures, revealed mitral valve vegetation colonized by H. parainfluenzae. The patient was started on appropriate antibiotics with follow-up for outpatient surgery. This case discusses the potential for ectopic colonization of heart valves by H. parainfluenzae in patients with CD. The presence of this organism as the offending agent in this patient's case of IE shines a light on the pathogenesis of CD. Although uncommon, CD-associated bacterial seeding should be a differential when assessing young patients with IE.

Periodontal disease is associated with increased gut colonization of pathogenic Haemophilus parainfluenzae in patients with Crohn's disease.

Intestinal colonization of the oral bacterium Haemophilus parainfluenzae has been associated with Crohn's disease (CD) severity and progression. This study examines the role of periodontal disease (PD) as a modifier for colonization of H. parainfluenzae in patients with CD and explores the mechanisms behind H. parainfluenzae-mediated intestinal inflammation. Fifty subjects with and without CD were evaluated for the presence of PD, and their oral and fecal microbiomes were characterized. PD is associated with increased levels of H. parainfluenzae strains in subjects with CD. Oral inoculation of H. parainfluenzae elicits strain-dependent intestinal inflammation in murine models of inflammatory bowel disease, which is associated with increased intestinal interferon-γ (IFN-γ)+ CD4+ T cells and disruption of the host hypusination pathway. In summary, this study establishes a strain-specific pathogenic role of H. parainfluenzae in intestinal inflammation and highlights the potential effect of PD on intestinal colonization by pathogenic H. parainfluenzae strains in patients with CD.

Systemic Haemophilus parainfluenzae Infection Manifesting With Endocarditis and Membranoproliferative Glomerulonephritis.

Infective endocarditis (IE) is a potentially fatal disease that is primarily caused by Staphylococci and Streptococci. The HACEK group of bacteria (Hemophilus species, Aggregatibacter species, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae) account for only 1-3% of reported IE cases. IE has long been known to cause glomerulonephritis. The most common histologic patterns seen are crescentic and diffuse proliferative glomerulonephritis. Notably, membranoproliferative glomerulonephritis (MPGN) is one of the less common patterns seen with IE. We present a rare case of MPGN associated with Haemophilus parainfluenzae endocarditis. A 56-year-old male with no significant past medical history presented to a local hospital with complaints of fever, night sweats, dyspnea, diarrhea, and dark urine for about a month. He was found to have a hemoglobin of 4g/dL, requiring multiple transfusions. He also had bilateral pleural effusions and pulmonary edema. In the following days, he had worsening renal function and was transferred to our hospital for further workup. Initial labs showed anemia, thrombocytopenia, and leukocytosis. He had creatinine elevated at 5.28 mg/dL and a low estimated glomerular filtration rate (eGFR) of 12 mL/min/1.73m2. Urinalysis showed proteinuria, urine hemoglobin, urine white blood cells (WBCs), and red blood cells (RBCs). Blood cultures revealed H. parainfluenzae. Transesophageal echocardiogram (TEE) showed large vegetations with perforation of the mitral valve leaflet. Serology showed low complement levels. Renal biopsy displayed a membranoproliferative pattern of glomerulonephritis on light microscopy. The hepatitis panel was negative, as was the autoimmune workup. The patient was diagnosed with MPGN associated with H. parainfluenzae endocarditis. His complex clinical course required mitral valve replacement and aortic valve repair. He completed the course of antibiotics, with improvement in renal and cardiac function.

Haemophilus parainfluenzae Pyogenic Liver Abscess Associated With Cholangiocarcinoma.

Haemophilus parainfluenzae (H. parainfluenzae) is a commensal organism of the gastrointestinal tract. It rarely causes hepatobiliary infections; however, in the presence of underlying inflammation, immunosuppression, or malignancy, it can cause hepatobiliary infection via an ascending route. Herein, we report a case of pyogenic liver abscess secondary to H. parainfluenzae associated with cholangiocarcinoma, which was treated with ceftriaxone and metronidazole.

Virulent endocarditis due to Haemophilus parainfluenzae: A systematic review of the literature.

BACKGROUND: Haemophilus parainfluenzae (HPI) belongs to the HACEK (Haemophilus spp., Aggregatibacter spp., Cardiobacterium spp., Eikenella spp., and Kingella spp.) group of organisms. The HACEK group of organisms are a part of the oropharyngeal flora and can cause invasive opportunistic infection such infective endocarditis (IE) in hosts with compromised immunological barriers. AIM: To perform a 20-year systematic review of the literature characterizing the clinical presentation, epidemiology and prognosis of HPI IE. METHODS: We performed a systematic review of Medline, Pubmed, Scopus and Embase from 2000 to 2022 to identify all cases of HPI IE. RESULTS: Thirty-nine adult cases were identified. HPI IE was found to affect males slightly more than females and is common in patients with predisposing risk factors such as underlying valvular abnormalities. It mostly affected the mitral valve and had an indolent course; significantly sized vegetations (> 1 cm) developed in most cases. Central nervous system septic embolization was common. It had a favorable prognosis compared to staphylococcal and streptococcal IE. CONCLUSION: Clinicians should be attentive to the indolent course of HPI IE and the presence of predisposing risk factors in order to allow for timely management.

A study of various factors affecting satellitism tests of Haemophilus influenzae and Haemophilus parainfluenzae using Staphylococcus aureus as the source of NAD.

Many factors affecting satellitism tests are unclear, and it is difficult to avoid misidentification, even if the medium is properly selected. We investigated the factors causing false-positive results for Haemophilus influenzae and false-negative results for Haemophilus parainfluenzae in the satellitism tests using Staphylococcus aureus as the source of nicotinamide adenine dinucleotide (NAD). H. influenzae (four reference strains and 47 clinical isolates), H. parainfluenzae (two reference strains and 67 clinical isolates), four different media, and two strains of S. aureus revived on two different media were used in this study. The type of medium used to revive S. aureus was the most common factor causing false-positive results for H. influenzae, followed by different strains of S. aureus and the type of medium used for the experiment. The production of false-negative results for H. parainfluenzae was only related to the medium used in the experiment. To improve the accuracy of the tests in routine laboratories, using S. aureus as the source of NAD, tryptic soy agar, and S. aureus (ATCC 25923) revived on nutrient agar should be adopted.

Haemophilus parainfluenzae endocarditis in a low-risk woman: a case report.

Haemophilus parainfluenzae endocarditis is a rare but dangerous disease. With this work, we intend to show the importance of early diagnosis and appropriate treatment in order to avoid complications. We also highlight the importance of local epidemiology to choose antibiotic prophylaxis for high-risk procedures in selected predisposed patients.

A Series of Haemophilus parainfluenzae Surgical Infections and Review of the Literature.

Background: Haemophilus parainfluenzae (HPI) is a rare and underreported pathogen. Haemophilus parainfluenzae causes respiratory, soft tissue, and central nervous system (CNS) infections, and endocarditis. Little data on HPI surgical infections are available, especially for intra-abdominal infections (IAI). Patients and Methods: Haemophilus parainfluenzae isolates were recovered from patients treated at a rural hospital during a two-year period. Isolation and identification of the pathogen was done according to standard guidelines. A literature review with regard to HPI IAI was done. Results: A total of 273 HPI isolates were analyzed, 15 patients had double isolates; HPI was commonly part of a mixed infection. Respiratory tract infections accounted for 64.8%, ear-nose-throat (ENT)/eye infections for 17.9%, genital/urologic infections for 3%, blood stream infections for 1% of cases and 13.2% of HPI isolates involved surgical infections. Thirty-four patients (36 isolates) had HPI surgical infections including 28 skin/soft tissue infections, two bone infections, two perirectal abscesses, one infected hemodialysis catheter, and three IAIs including perforated appendicitis, perforated diverticulitis, and a pelvic abscess 10 days after laparoscopic appendectomy. All three IAIs were mixed infections and successfully managed with percutaneous drainage and antibiotic therapy. More than 90% of HPI isolates in our hospital tested negative for ß-lactamase production. A literature review revealed 32 reported cases of HPI IAI including biliary infections (12), peritonitis (9), liver abscess (7), and IA abscess (4) with the majority being monomicrobial; treatment included antibiotic agents and surgery/intervention in most cases. Outcomes were generally favorable. Conclusions: Our study confirms data from the literature that HPI is capable of causing a variety of severe surgical infections. More research with regard to this pathogen is warranted.

Pyelonephritis and bacteremia caused by Haemophilus parainfluenzae: case-report of an unusual pathogen.

We present a case of a young man with known urinary tract abnormalities who developed pyelonephritis and bacteremia caused by Haemophilus parainfluenzae. Since routine urine culture usually does not include enriched media for Haemophilus spp., the true incidence of urinary tract infections caused by H. parainfluenzae is currently unknown. Our case, however, demonstrates that H. parainfluenzae is a potential urinary pathogen, at least in patients with urinary tract anomalies. Clinical laboratories should consider expanding their culture efforts to detect unusual pathogens in patients with underlying risk factors.

Genomic Diversity and Antimicrobial Resistance of Haemophilus Colonizing the Airways of Young Children with Cystic Fibrosis.

Respiratory infection during childhood is a key risk factor in early cystic fibrosis (CF) lung disease progression. Haemophilus influenzae and Haemophilus parainfluenzae are routinely isolated from the lungs of children with CF; however, little is known about the frequency and characteristics of Haemophilus colonization in this context. Here, we describe the detection, antimicrobial resistance (AMR), and genome sequencing of H. influenzae and H. parainfluenzae isolated from airway samples of 147 participants aged ≤12 years enrolled in the Australian Respiratory Early Surveillance Team for Cystic Fibrosis (AREST CF) program, Melbourne, Australia. The frequency of colonization per visit was 4.6% for H. influenzae and 32.1% for H. parainfluenzae, 80.3% of participants had H. influenzae and/or H. parainfluenzae detected on at least one visit, and using genomic data, we estimate 15.6% of participants had persistent colonization with the same strain for at least two consecutive visits. Isolates were genetically diverse and AMR was common, with 52% of H. influenzae and 82% of H. parainfluenzae displaying resistance to at least one drug. The genetic basis for AMR could be identified in most cases; putative novel determinants include a new plasmid encoding blaTEM-1 (ampicillin resistance), a new inhibitor-resistant blaTEM allele (augmentin resistance), and previously unreported mutations in chromosomally carried genes (pbp3, ampicillin resistance; folA/folP, cotrimoxazole resistance; rpoB, rifampicin resistance). Acquired AMR genes were more common in H. parainfluenzae than H. influenzae (51% versus 21%, P = 0.0107) and were mostly associated with the ICEHin mobile element carrying blaTEM-1, resulting in more ampicillin resistance in H. parainfluenzae (73% versus 30%, P = 0.0004). Genomic data identified six potential instances of Haemophilus transmission between participants, of which three involved participants who shared clinic visit days. IMPORTANCE Cystic fibrosis (CF) lung disease begins during infancy, and acute respiratory infections increase the risk of early disease development and progression. Microbes involved in advanced stages of CF are well characterized, but less is known about early respiratory colonizers. We report the population dynamics and genomic determinants of AMR in two early colonizer species, namely, Haemophilus influenzae and Haemophilus parainfluenzae, collected from a pediatric CF cohort. This investigation also reveals that H. parainfluenzae has a high frequency of AMR carried on mobile elements that may act as a potential reservoir for the emergence and spread of AMR to H. influenzae, which has greater clinical significance as a respiratory pathogen in children. This study provides insight into the evolution of AMR and the colonization of H. influenzae and H. parainfluenzae in a pediatric CF cohort, which will help inform future treatment.