Bacteria

In the scientific literature, in vitro direct interaction has been shown between the ApoH protein and some bacteria. For instance, a direct interaction has been described with Staphylococcus aureus via the Sbi protein (Zhang et al., 1999),  with Streptococcus pyogenes via the M1 and H surface protein (Nilsson et al., 2008) and most recently with the Escherichia coli LPS (Agar et al., 2011).

In-house studies have shown that the ApoH protein is able to bind to a wide panel of bacteria, Gram positive or negative, aerobic or anaerobic, culturable or viable but non-culturable. Below is a non-exhaustive list of viruses retained on ApoH:

 

GRAM +

GRAM –

Bacillus sp.

Acinetobacter sp.

Porphyromonas endodontalis

Clostridium difficile

Bacteroides sp.

Prevotella oris

Corynebacterium sp.

Bilophila wadsworthia

Proteus mirabilis

Dermabacter

Capnocytophaga canimorsus

Providencia stuartii

Enterococcus sp.

Chlamydia sp.

Pseudomonas sp.

Listeria sp.

Citrobacter freundii

Salmonella sp.

Micrococcus sp.

Enterobacter sp.

Serratia marcescens

Mycobacterium

Escherichia coli

Stenotrophomonas maltophilia

Propionibacterium acnes

Fusobacterium nucleatum

Tropheryma whipplei

Staphylococcus sp.

Klebsiella sp.

...

Streptococcus sp.

Ochrobactrum sp.

Culture

The use of ApoH magnetic beads to bind and concentrate bacteria from varied samples is directly compatible with bacterial culture systems, in liquid media as well as on Petri dishes. Notably, slow-growing bacteria become detectable much faster after their concentration.

Blood culture

The detection of bacteria in blood culture is often challenging due to the extensively various nature of bacteria supposedly present (aerobic, anaerobic, slow growth…).  Moreover, antibiotics often present in the patient’s blood may interfere with diagnostics. The use of ApoH magnetic beads in these complex samples to clarify and concentrate the bacteria is an easy way to overcome these issues. ApoH can enhance detection and reduce analysis delays.

In this example, the ApoH ability to detect bacteria in hemocultures was evaluated by comparing to standard hospital detection systems.

The ApoH technology showed a real detection superiority, with an excellent diagnostic sensitivity.

PCR

The concentration of bacteria on the ApoH magnetic beads induces an increase in PCR signals, PCR being the most used technique to detect and identify cultivated strains.

In the following example, 4 strains from blood cultures (Klebsiella pneumoniae, Staphyloccocus aureus, Coagulase-negative Staphyloccocus and Propionibacterium acnes) were concentrated on ApoH magnetic beads, which gave a higher PCR signal with ApoH than without ApoH. Remarkably, the PCR signal was very dependent on the bacterial lysis efficiency.

It would then seem useful to check the efficacy of detection systems after the ApoH pretreatment step, to obtain the best sensitivity possible.