Harnessing of Artificial Intelligence for the Diagnosis and Prevention of Hospital-Acquired Infections: A Systematic Review

Healthcare-associated infections (HAIs) are the most common adverse events in healthcare and constitute a major global public health concern. Surveillance represents the foundation for the effective prevention and control of HAIs, yet conventional surveillance is costly and labor intensive. Artificial intelligence (AI) and machine learning (ML) have the potential to support the development of HAI surveillance algorithms for the understanding of HAI risk factors, the improvement of patient risk stratification as well as the prediction and timely detection and prevention of infections. AI-supported systems have so far been explored for clinical laboratory testing and imaging diagnosis, antimicrobial resistance profiling, antibiotic discovery and prediction-based clinical decision support tools in terms of HAIs. This review aims to provide a comprehensive summary of the current literature on AI applications in the field of HAIs and discuss the future potentials of this emerging technology in infection practice. Following the PRISMA guidelines, this study examined the articles in databases including PubMed and Scopus until November 2023, which were screened based on the inclusion and exclusion criteria, resulting in 162 included articles. By elucidating the advancements in the field, we aim to highlight the potential applications of AI in the field, report related issues and shortcomings and discuss the future directions.

Characterization of Virulence Genes Associated with Type III Secretion System and Biofilm Formation in Pseudomonas aeruginosa Clinical Isolates

Pseudomonas aeruginosa is a common pathogen with an increasing multidrug resistance (MDR) phenotype. Its virulence determinants include many factors such as antimicrobial resistance, biofilm formation, and type III secretion system (T3SS) which correlate with disease severity. There are no reports regarding the virulence features of P. aeruginosa in Cyprus. The aim of this study was to investigate the frequency and distribution of selected virulence-encoding genes and evaluate the biofilm formation potential as well as antibiotic resistance rates of isolates in the region. One hundred clinical P. aeruginosa isolates were obtained from clinical specimens and were identified using standard microbiological techniques. Antimicrobial susceptibility was assessed using the VITEK-2 system and biofilm quantification was performed by the microtiter plate assay with crystal violet staining. The presence of algD, exoU, exoT, and exoS was evaluated using polymerase chain reaction (PCR). Among all isolates, 35% were strong biofilm former, 28% were moderate biofilm former, 19% were weak biofilm former, and 18% were non-biofilm former. The rates of MDR and extensive drug resistance (XDR) were 26% and 1%. PCR analysis indicated that 93% of the isolates were algD positive. T3SS genes exoT, exoS, and exoU were detected in 91%, 63%, and 32% of the isolates, respectively. There was a high frequency of exoT + /exoS + genotype (61%), whereas exoT + /exoU + (32%) and exoS + /exoU + (2%) genotypes were relatively uncommon. This study reports the first dataset on the molecular profile of P. aeruginosa in Cyprus. Our results demonstrated that most strains have the biofilm-forming capacity with an algD-positive genotype and the majority carry exoT and exoS with a high frequency of exoT + /exoS + genotype.

Antibiotics Knowledge, Attitudes and Behaviours among the Population Living in Greece and Turkey

Antimicrobial resistance is one of the largest threats to public health worldwide. As the inappropriate use of antibiotics is one of the leading causes of antibiotic resistance, it is important to have an understanding of the public's knowledge, attitudes and behaviours towards antibiotics and antimicrobial resistance. The present study investigated the knowledge, attitudes and behaviours towards antibiotics among the public living in Greece and Turkey using an online cross-sectional survey, with social media advertising (e.g., Facebook) and snowball sampling. In total, 709 individuals completed the survey (Greece n = 309, Turkey n = 400), with an average age of 34.2 (SD = 13.1) and 40.5 (SD = 14.7), respectively. In Greece, 49.4% of the participants were female, and in Turkey, this figure was 62.4%. The Greek respondents reported that obtaining antibiotics without a prescription was easier (52.6% reported "easy or very easy") than the Turkish (35.6% reported "easy or very easy") respondents did. This study reveals that Greek citizens were more educated and knowledgeable about antibiotics (58.5% of Greeks and 44.2% of Turks identified antibiotics correctly), their effects (20.9% of Greeks and 26.3% of Turks agreed with wrong statements about antibiotics) and the risks of antibiotic resistance, compared to those from Turkey. On the other hand, the Greek respondents were more prone to use leftover antibiotics or to give them to someone else later (p < 0.001). The findings of this study indicate that Greece and Turkey, both countries with high rates of antibiotic usage, exhibit distinct variations in their knowledge, attitudes, and perceptions concerning antibiotic use and antibiotic resistance. Effective countermeasures such as public campaigns should be targeted according to the population and those areas of knowledge, attitudes and behaviours in which the main shortcomings lie.

Prevalence and genotype screening of human papillomavirus among women attending a private hospital in Northern Cyprus: an 11-year retrospective study

BACKGROUND

Human papillomavirus (HPV) is the most common sexually transmitted pathogen both in men and women. Accumulating epidemiological evidence supports a strong association between HPV infection and cancer of the cervix, vulva, vagina, anus, and penis. Currently, data on the HPV prevalence and genotyping is lacking in Northern Cyprus, a region in which HPV vaccination is not freely accessible via the national immunization program. The aim of this study was to evaluate the HPV type-specific prevalence in women with and without cytological abnormalities living in Northern Cyprus.

METHODS

A total of 885 women who presented to the Department of Gynecology and Obstetrics Clinic between January 2011 and December 2022 were included in the study. Samples were collected for cytology. Cervical specimens were investigated for the presence of HPV-DNA and genotyping of HPV was performed using real-time polymerase chain reaction (rtPCR). Cytological examination was interpreted according to the Bethesda system.

RESULTS

Among all patients, overall high-risk HPV DNA prevalence was 44.3%. HPV-16 and HPV-18 positivity was found in 10.4% and 3.7% of women respectively, while other high-risk HPV (OHR-HPV) was the most frequent type of HPV (30.2%). The highest frequency of HPV infection was observed in the 30-55 age group (51.0%), followed by the < 30 age group (45.7%). Co-infection with two or more HPV types was observed in 17.0% of all positive samples, in which the prevalence of HPV-16 + HPV-18 was 2.3%, HPV-16 + OHR-HPV and HPV-18 + OHR-HPV was 12.0% and 5.1%, respectively. Among the screened patients, 37.5% had abnormal and 62.5% had normal cytology results. HR-HPV positivity was 65.7% and 34.0% in patients with abnormal and normal cytology. The highest incidence of HRC-HPV was OHR-HPV types (44.7%) in positive cytology cases. Among women with a cytology result of ASCUS, L-SIL, H-SIL and unspecified dysplasia, 52.1%, 67.6%, 97.5% and 75.6% were respectively infected with HR-HPV.

CONCLUSION

The present study provides the latest epidemiological data related to HPV prevalence and genotype distribution among women living in Northern Cyprus. Considering the unavailability of free vaccination in the community, it is imperative to implement local HPV screening programs and provide guidelines on HPV prevention and measures during early school education.

Antibiotics Knowledge, Attitudes and Behaviours among the Population Living in Cyprus

This study investigated the knowledge, attitudes and behaviours towards antibiotics among the general public living in the Republic of Cyprus (RoC) and the Turkish Republic of Northern Cyprus (TRNC) by using an online questionnaire. Differences were examined using independent samples t-tests, chi-square tests, Mann-Whitney U tests and Spearman's rho. In total, 519 individuals completed the survey (RoC = 267, TRNC = 252), with an average age of 32.7, and 52.2% were female. Most citizens correctly identified paracetamol (TRNC = 93.7%, RoC = 53.9%) and ibuprofen (TRNC = 70.2%, RoC = 47.6%) as non-antibiotic medications. A substantial proportion thought antibiotics could treat viral infections, such as a cold (TRNC = 16.3%, RoC = 40.8%) or the flu (TRNC = 21.4%, RoC = 50.4%). Most participants understood that bacteria can become resistant to antibiotics (TRNC = 71.4%, RoC = 64.4%), that unnecessary use can lead to drug ineffectiveness (TRNC = 86.1%, RoC = 72.3%) and that they should always complete the course of antibiotics (TRNC = 85.7%, RoC = 64.0%). Positive attitudes towards antibiotics correlated negatively with knowledge in both samples, indicating that the more people know, the less positive their attitudes towards their use. The RoC appears to have tighter controls of over-the-counter (OTC) sales of antibiotics than TRNC. This study reveals that different communities can have varying levels of knowledge, attitudes and perceptions about antibiotic use. Tighter enforcement of the OTC regulations, educational efforts and media campaigns are needed for enhancing prudent antibiotic use on the island.

Knowledge, attitudes and behaviours regarding antibiotics use among Cypriot university students: a multi-disciplinary survey

BACKGROUND

The present study aims to investigate the knowledge and attitudes towards antibiotics among students studying medicine, dentistry, and pharmacy at the Near East University in Northern Cyprus. The influence of personality characteristics on antibiotic use were also evaluated, in order to identify predictors of antibiotic misuse.

METHODS

Students were enrolled in the study during the 2020-2021 academic year. Study participants were asked to complete an online questionnaire that measured their knowledge, attitudes and practice (KAP) towards antibiotic use and antibiotic resistance. The KAP of students from the three faculties were compared using Kruskall-Wallis H statistics, Mann-Whitney U statistics, and Spearman's rho. The influence of personality traits on the propensity to use antibiotics without a prescription, as well as their attitudes and knowledge of antibiotic use and misuse, were also investigated.

RESULTS

In total, 314 students completed the survey, 52% of which were female. The mean age of the students was 20.5 years. The results showed that among the different disciplines, medical students were significantly more knowledgeable about pharmacological agents, compared to dentistry and pharmacy students, while pharmacy students were more knowledgeable about the effectiveness of antibiotics against different pathogenic microorganisms. All student groups were aware of how antibiotic resistance develops and their role as healthcare personnel in implementing measures against resistance. Appropriate antibiotic use among the student community correlated with study year, highlighting the importance of knowledge and education in the prevention of antibiotic resistance. Personality traits were found to be a contributing factor in students' tendency to use antibiotics without a prescription.

CONCLUSION

This study demonstrates the importance of conveying knowledge about antimicrobials in the education programmes of future dentists, pharmacists and physicians.

Screening of Toxin Genes in Methicillin-Resistant Staphylococcus aureus Clinical Isolates from a Hospital Setting in a Tertiary Hospital in Northern Cyprus

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant opportunistic pathogen with a wide repertoire of virulence characteristics. Data regarding the molecular profile of MRSA in Northern Cyprus is limited. The current study aimed to examine the virulence profiles of MRSA with a focus on toxin-associated factors. Ninety-one S. aureus isolates collected at a university hospital were included in the study. Identification and antibiotic susceptibility testing were performed with BD Phoenix™ automated system. Methicillin resistance was evaluated by the disc diffusion assay and mecA detection. The presence of nuc was confirmed by conventional PCR. Confirmed MRSA isolates were assessed for the presence of virulence genes hla, eta, etb, etd and tst using molecular methods. Among 91 S. aureus isolates identified as MRSA using the BD Phoenix™ platform, 80.85% (n = 76/91) were confirmed as MRSA using phenotypic and genotypic methods. All confirmed MRSA isolates (n = 76, 100%) were positive for the nuc. MRSA rates were statistically higher in elderly inpatients. The prevalence of toxin-encoding genes was 97.3% (n = 74/76) for hla, 2.63% (n = 2/76) for eta, 1.3% (n = 1/76) for etb, and 2.63% (n = 2/76) for tst. None of the screened isolates harbored the etd gene. These results represent the first report to investigate multiple virulence factors in MRSA isolates in Northern Cyprus.

Detection of SARS-CoV-2 N501Y mutation among SARS-CoV-2 variants of concern circulating in Northern Cyprus

Aim: SARS-CoV-2 variants of concern (VOCs) carry signature mutations particularly in the spike protein. Most VOCs lineages that carry N501Y substitution have been reported to evade viral diagnostic tests and have impact on vaccine effectiveness. Therefore, monitoring the circulating variants represents a major requirement for a public health response worldwide. We aimed to investigate the prevalence of N501Y bearing SARS-CoV-2 samples in Northern Cyprus. Materials & methods: Reverse transcription quantitative PCR technique was used to identify N501Y mutation from 658 samples. Results: Our results indicate that the proportion of N501Y-bearing lineages increased significantly from January through May 2021 (45.2–75.5%) in the region. Conclusion: These results indicate that VOCs are dominant lineages in the country and highlight an alarming situation which require strict governmental measures to minimize COVID-19 morbidity and mortality.

In vitro Anti-Leishmanial Activity of Essential Oils Extracted from Plants Growing in Northern Cyprus Against Leishmania tropica

OBJECTIVE

Natural plant products are considered as a source of novel and effective compounds for the treatment of leishmaniasis. In this study, the in vitro activities of essential oils obtained from Origanum dubium (OD), Origanum majorana (OM), Salvia fruticosa (SF) and Laurus nobilis (LN) plants in Northern Cyprus were investigated against Leishmania tropica.

METHODS

Leishmania tropica strain (MHOM/TR/2012/CBCL-LT) was obtained. RPMI-1640 was added to 96-well plates in 100 μL aliquots, 100 μg/mL essential oil was added to the first well of each row and serial 2-fold dilutions were performed. A promastigote suspension was pipetted into all wells, and the plates were incubated. The promastigotes were enumerated using a haemocytometer.

RESULTS

OD essential oil was effective at killing all promastigotes at a minimum inhibitor height (MIC)=0.2 μg/mL and had high activity at the lowest concentrations. Both SF and LN oils had MIC=1.56 μg/mL and LD₅₀=0.78 μg/mL. SF was observed to impair promastigote morphology at the lowest concentrations, while LN did not exert any effect at concentrations <0.2 μg/mL. OM essential oil was found to have a MIC=3.13 μg/mL and a LD₅₀=1.56 μg/mL.

CONCLUSION

All tested essential oils inhibited promastigotes of Leishmania tropica. OD essential oil demonstrated the highest anti-leishmanial activity.

AMAÇ

Bitkilerden elde edilen doğal ürünlerin leishmaniasis tedavisi için yeni ve etkili bileşiklerin üretilmesine öncülük edeceği düşünülmektedir. Çalışmamızda, Kuzey Kıbrıs’ta yetişen Origanum dubium (OD), Origanum majorana (OM), Salvia fruticosa (SF) ve Laurus nobilis (LN) bitkilerinden elde edilen uçucu yağların Leishmania tropica’ya karşı in vitro etkinlikleri araştırılmıştır.

YÖNTEMLER

Çalışmamızda, Leishmania tropica suşu (MHOM/TR/2012/CBCL-LT) kullanıldı. Düz tabanlı 96’lık plaklarda, tüm kuyucuklara 100 μL RPMI-1640 ve ilk kuyucuklara 100 μg/mL uçucu yağlar eklenerek, seri dilüsyonları yapıldı. Ardından tüm kuyucuklara Leishmania tropica promastigot süspansiyonundan pipetlendi ve inkübe edildi. Hemositometre yöntemiyle promastigotların sayısı incelendi.

BULGULAR

OD yağının minimum inhibitör konsantrasyonu (MİK)=0,2 μg/mL’de tüm promastigotları öldürürken, en düşük konsantrasyonlarda bile etkili olduğu görülmüştür. SF ve LN uçucu yağlarının ikisinde de MİK=1,56 μg/mL, LD₅₀=0,78 μg/mL olarak saptanmıştır. SF’nin en düşük konsantrasyonlarının bile promastigot morfolojisini bozduğu görülürken, Laurus nobilis’in ise 0,2 μg/mL’den sonraki konsantrasyonlarda etkisini kaybettiği belirlenmiştir. OM uçucu yağının MİK=3,13 μg/mL, LD₅₀=1,56 μg/mL olduğu görülmüştür.

SONUÇ

Kullanılan tüm uçucu yağların Leishmania tropica promastigotlarını inhibe ettiği görülürken, en yüksek anti-leishmanial etkinlik Origanum dubium uçucu yağında bulunmuştur.

Refining Host-Pathogen Interactions: Organ-on-Chip Side of the Coin

Bioinspired organ-level in vitro platforms that recapitulate human organ physiology and organ-specific responses have emerged as effective technologies for infectious disease research, drug discovery, and personalized medicine. A major challenge in tissue engineering for infectious diseases has been the reconstruction of the dynamic 3D microenvironment reflecting the architectural and functional complexity of the human body in order to more accurately model the initiation and progression of host-microbe interactions. By bridging the gap between in vitro experimental models and human pathophysiology and providing alternatives for animal models, organ-on-chip microfluidic devices have so far been implemented in multiple research areas, contributing to major advances in the field. Given the emergence of the recent pandemic, plug-and-play organ chips may hold the key for tackling an unmet clinical need in the development of effective therapeutic strategies. In this review, latest studies harnessing organ-on-chip platforms to unravel host-pathogen interactions are presented to highlight the prospects for the microfluidic technology in infectious diseases research.

Prioritizing potential ACE2 inhibitors in the COVID-19 pandemic: Insights from a molecular mechanics-assisted structure-based virtual screening experiment

Angiotensin-converting enzyme 2 (ACE2) is a membrane-bound zinc metallopeptidase that generates the vasodilatory peptide angiotensin 1-7 and thus performs a protective role in heart disease. It is considered an important therapeutic target in controlling the COVID-19 outbreak, since SARS-CoV-2 enters permissive cells via an ACE2-mediated mechanism. The present in silico study attempted to repurpose existing drugs for use as prospective viral-entry inhibitors targeting human ACE2. Initially, a clinically approved drug library of 7,173 ligands was screened against the receptor using molecular docking, followed by energy minimization and rescoring of docked ligands. Finally, potential binders were inspected to ensure molecules with different scaffolds were engaged in favorable contacts with both the metal cofactor and the critical residues lining the receptor's active site. The results of the calculations suggest that lividomycin, burixafor, quisinostat, fluprofylline, pemetrexed, spirofylline, edotecarin, and diniprofylline emerge as promising repositionable drug candidates for stabilizing the closed (substrate/inhibitor-bound) conformation of ACE2, thereby shifting the relative positions of the receptor's critical exterior residues recognized by SARS-CoV-2. This study is among the rare ones in the relevant scientific literature to search for potential ACE2 inhibitors. In practical terms, the drugs, unmodified as they are, may be introduced into the therapeutic armamentarium of the ongoing fight against COVID-19 now, or their scaffolds may serve as rich skeletons for designing novel ACE2 inhibitors in the near future.

Prevalence of Panton-Valentine leukocidin in methicillin-resistant Staphylococcus aureus clinical isolates at a university hospital in Northern Cyprus: a pilot study

Objective

Panton-Valentine leukocidin (PVL)-positive methicillin-resistant Staphylococcus aureus (MRSA) is a healthcare problem worldwide. There are no reports on the virulence characteristics of MRSA in Northern Cyprus (NC). This study aimed to determine the presence of pvl among MRSA isolates from patients admitted to a university hospital in NC using molecular methods. Fifty S. aureus strains were included in this study. BD Phoenix automated identification system was used for bacterial identification and antibiotic susceptibility testing. Methicillin resistance was confirmed by disc diffusion assay. Presence of nuc and mecA genes was tested by multiplex PCR. Detection of pvl gene was performed by single-target PCR.

Results

Out of 50 S. aureus isolates identified as MRSA by BD Phoenix system, 3 were susceptible to cefoxitin with disc diffusion assay and were confirmed as methicillin-sensitive S. aureus (MSSA). All isolates (n = 50, 100%) tested positive for the presence nuc gene and 68% (n = 34/50) were mecA positive. pvl was detected in 27.7% (n = 13/47) of the MRSA isolates. Among PVL-positive MRSA isolates, 69.2% (9/13) were inpatients. PVL-MRSA was more common in isolates from deep tracheal aspirate (30.8%, 4/13) and abscess/wound (23.1%, 3/13). This represents the first study of PVL presence among MRSA in hospital setting in NC.

The Effectiveness of Laser-Activated Irrigation on the Apical Microleakage Qualities of MTA Repair HP and NeoMTA Plus in Simulated Immature Teeth: A Comparative Study

There are limited data regarding the potential effect of erbium, chromium: yttrium–scandium–gallium–garnet (Er,Cr:YSGG) laser-activated irrigation (LAI) on the microleakage qualities of calcium silicate-based cements. The objective of the present study was to assess the effect of LAI on the microleakage qualities of MTA Repair HP (MTA-HP) and NeoMTA Plus (Neo) used in root-end filling and to compare the antimicrobial effectiveness of MTA- HP. Two experimental sets were conducted: antimicrobial activity (agar diffusion test/at 24, 48 h) and microleakage (glucose leakage model/at 1st, 10th, 20th days). Antimicrobial activities of MTA-HP, Neo, Biodentine, ProRoot and MTA Angelus were evaluated, and inhibition zones were observed not only against a range of Gram-positive and Gram-negative bacteria but also against yeast at 48h. For microleakage evaluation, fifty teeth were prepared to simulate the clinical situation where the root-tips (apex) are open, and randomly divided into two experimental groups (n = 20/group) according to the cement type (MTA-HP and Neo), and two control (n = 5/group) groups. Each experimental group was further divided into two subgroups (n = 10/group) with respect to LAI: MTA-HP, L-HP, Neo, L-Neo. A statistical difference was only detected between Neo and L-HP groups on day 1. Subsequently, MTA-HP exhibited superior microleakage quality compared to Neo in the short-term. Er,Cr:YSGG laser-activated irrigation could be used as a reliable technique without creating adverse effects on the sealing abilities of MTA Repair HP and NeoMTA Plus.

Current situation of COVID-19 in northern Cyprus

Background

The public health burden of the novel coronavirus disease 2019 (COVID-19) is expected to increase and urgent strict measures by decision-makers is critical for the containment of the novel coronavirus (SARS-CoV-2) outbreak worldwide.

Aims

This study aimed to give a real-time analysis of COVID-19 presence in northern Cyprus.

Methods

All official SARS-CoV-2 positive cases were tracked and reported in terms of the origin, nationality, and transmission routes. Preventive measures taken after the first reported case were analyzed for their effectiveness as control strategies.

Results

The index case of SARS-CoV-2 in northern Cyprus was identified as a female German tourist. First local case had travel history from the United Kingdom after which local transmission occurred. Rapid and strict containment measures have currently delayed a peak in observed cases.

Conclusions

Rapid implementation of social-distancing measures, good hygiene measures and travel/gathering bans in northern Cyprus has been effective in controlling the outbreak.

Next-generation technologies for studying host-pathogen interactions: a focus on dual transcriptomics, CRISPR/Cas9 screening and organs-on-chips

Pathogens constantly interact with their hosts and the environment, and therefore have evolved unique virulence mechanisms to target and breach host defense barriers and manipulate host immune response to establish an infection. Advances in technologies that allow genome mining, gene editing such as CRISPR/Cas9, genomic, epigenomic and transcriptomic studies such as dual RNA-seq, coupled with bioinformatics, have accelerated the field of host-pathogen interactions within a broad range of infection models. Underpinning of the molecular changes that accompany invasion of eukaryotic cells with pathogenic microorganisms at the intersection of host, pathogen and their local environment has provided a better understanding of infectious disease mechanisms and antimicrobial strategies. The recent evolution of physiologically relevant three-dimensional (3-D) tissue/organ models and microfluidic organ-on-chip devices also provided a window to a more predictive framework of infectious disease processes. These approaches combined hold the potential to highly impact discovery of novel drug targets and vaccine candidates of the future. Here, we review three of the available and emerging technologies-dual RNA-seq, CRISPR/Cas9 screening and organs-on-chips, applicable to the high throughput study and deciphering of interaction networks between pathogens and their hosts that are critical for the development of novel therapeutics.

Characterization of biofilm formation and induction of apoptotic DNA fragmentation by nontypeable Haemophilus influenzae on polarized human airway epithelial cells

Nontypeable Haemophilus influenzae (NTHi) is a common airway commensal and opportunistic pathogen that persists within biofilm communities in vivo. Biofilm studies so far are mainly based on assays on plastic surfaces. The aim of this work was to investigate the capacity of clinical NTHi strains to form biofilm structures on polarized Calu-3 human airway epithelial cells and primary normal human bronchial epithelial cells and to characterize the biofilm architecture. Formation of adherent NTHi biofilms post colonization of host cells at multiple time-points was evaluated using confocal laser scanning microscopy and electron microscopy. NTHi biofilms were analyzed in terms of biofilm height and presence of extracellular matrix components, and their apoptotic effects on epithelial cells were measured by TUNEL assay. Strain Fi176 was observed to form robust biofilms on airway epithelia over time, while disrupting the integrity of Calu-3 monolayer by 72 h of co-culture. NTHi biofilms were observed to induce apoptotic DNA fragmentation in host cells at 24 h post infection. Biofilm formation on cell monolayers by Fi176ΔpilA strain was markedly reduced compared to WT strain. Biofilm inhibition and disruption assays by crystal violet staining indicated that DNA and proteins are part of NTHi biofilms in vitro. Our findings highlight critical stages of NTHi pathogenesis following host colonization and provide useful biofilm models for future antimicrobial drug discovery investigations.

Development of a serological assay to predict antibody bactericidal activity against non-typeable Haemophilus influenzae

Background

Non-typeable Haemophilus influenzae (NTHi) is a Gram negative microorganism residing in the human nasopharyngeal mucosa and occasionally causing infections of both middle ear and lower respiratory airways. A broadly protective vaccine against NTHi has been a long-unmet medical need, as the high genetic variability of this bacterium has posed great challenges.

Results

In this study, we developed a robust serum bactericidal assay (SBA) to optimize the selection of protective antigens against NTHi. SBA takes advantage of the complement-mediated lysis of bacterial cells and is a key in vitro method for measuring the functional activity of antibodies. As a proof of concept, we assessed the bactericidal activity of antibodies directed against antigens known to elicit a protective response, including protein D used as carrier protein in the Synflorix pneumococcal polysaccharide conjugate vaccine. Prior to SBA screening, the accessibility of antigens to antibodies and the capacity of the latter to induce C3 complement deposition was verified by flow cytometry. Using baby rabbit serum as a source of complement, the proposed assay not only confirmed the bactericidal activity of the antibodies against the selected vaccine candidates, but also showed a significant reproducibility.

Conclusions

Considering the rapidity and cost-effectiveness of this novel SBA protocol, we conclude that it is likely to become an important tool to prove the capability of antibodies directed against recombinant antigens to induce NTHi in vitro killing and to both select new protective vaccine candidates, and predict vaccine efficacy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-015-0420-x) contains supplementary material, which is available to authorized users.