A New Approach in the Therapy of Infections with Multi-Drug Resistant Bacteria: Monoclonal Antibodies

BLEBEA Nicoleta Mirela1, OHÎI Clementina2*, MOROȘAN Elena3

1Pharmacology and Clinic Pharmacy Department, Faculty of Pharmacy, Ovidius University from Constanța, Romania

2Emergency County Clinical Hospital “Sf. Apostol Andrei” from Constanța

3Clinical Laboratory and Food Hygiene Department, Faculty of Pharmacy,”Carol Davila” University of Medicine and Pharmacy, 6, Traian Vuia Street, 020956, Bucharest (ROMANIA)

  *corresponding author:clementina.ohîi@yahoo.com


The treatment of infections caused by multidrug-resistant (MDR) bacteria puts pressure on medical systems globally, and research in recent years is aimed both at developing new antibiotics and valorizing of the therapeutic potential of other classes of drugs. The use of monoclonal antibodies (mAb) is proving to be a promising approach, due to their characteristics, such as high specificity for a particular pathogen and minimal effect on saprophytic bacterial species. However, the development of such drugs involves high costs, which is an impediment to the widespread approach to these therapies.

Keywords: monoclonal antibody, infectious disease, multidrug-resistant bacteria.


The appearance and spread of bacterial strains wich resistance to different classes of antibiotics make it difficult to treat the infections caused by them and involve high costs of human and material resources. In May 2015, the World Health Organization adopted a Global Action Plan on Antimicrobial Resistance, which aims, in addition to raising awareness of the problem of antimicrobial resistance, to reduce the incidence of infections through effective hygiene and preventive measures and to optimize the use of antimicrobial drugs in human and animal health, and increasing investment in the development of new drugs, diagnostic tools and vaccines [1]. The efforts of specialists are directed both towards the development of new classes of antibiotics and the prevention and treatment of certain multidrug resistant (MDR) infections through approaches based on drugs from other therapeutic groups. Monoclonal antibodies (mAbs) was initially developed for the treatment of  inflammatory and neoplastic diseases, but they have been shown to have real therapeutic potential in treating infections with MDR bacteria.


The aim of this study is to present a relatively recent approach in the treatment of infectious diseases caused by MDR bacteria.

Materials and methods

We analyzed journal articles from the specialized literature of the last decade, accessed from the ScienceDirect and Web of Science databases and using the keywords “monoclonal antibody”, “infectious disease”, “multidrug-resistant bacteria”, as well as specific terms, such as the name of the pathogens. We extracted data of interest on monoclonal antibody therapy against multi-resistant infections.

Results and discussions

When a foreign substance or toxin (the antigen) enters into the body, the immune system responds by producing and releasing antibodies- proteins that recognize the specific components of the pathogen and neutralize it. Monoclonal antibodies are substances developed in the laboratory, obtained from the same cell line and recognizing the same antigen. If the first types of mAbs made, murine mAbs, then chimeric ones (65% human and 35% murine), can frequently cause allergic reactions and induce anti-drug antibodies, the development of new technologies has made it possible to obtain humanized mAbs (95% human) and even fully human mAbs, which are less antigenic and better tolerated and appear to remain present in the bloodstream for a longer time compared to other classes of mAbs [2].
MAb have several characteristics that could make it suitable for the treatment of infections with antibiotic-resistant germs. The efficacy of mAb does not appear to be affected by bacterial resistance mechanisms, as antibacterial mAbs typically target surface-exposed antigens or secreted toxins that are not targets of currently used antimicrobials. Unlike antibiotics, mAbs have a minimal effect on saprophytic bacterial species, such as those that make up the normal bacterial flora [3].

However, the high specificity of mAb for the target pathogen may be a disadvantage in therapeutic practice.  Infectious bacterial species should be identified before starting therapy, which sometimes cannot be achieved very quickly. An additional limitation of mAb would be that these molecules are fragile and perishable [4] and that they are usually delivered intravenously, intravenous therapy being difficult in most outpatients because they require special conditions and specialized personnel. Finally, the possibility that mAb could select resistant bacterial strains by mutations that alter the sequence of the target epitope or the expression of the targeted antigen is not completely ruled out [3]. We have presented below some examples of mAbs that are being studied for their effect against MDR bacteria.

Monoclonal antibodies against multidrug-resistant Gram-negative bacteria

Pseudomonas aeruginosa is the most common and most serious pathogen involved in the chronic respiratory infections in patients with cystic fibrosis, in the bloodstream infections and in the large burns-site infections [3,5] and has been reported as an important cause of conjunctivitis in the elderly and in the neonatal intensive care units [6].
Classical antibiotics with anti-pseudomonas activity include aminoglycosides, ceftazidime and carbapenems. However, 15% of clinical isolates of Pseudomonas aeruginosa are resistant to imipenem and it has been shown that imipenem is associated with the frequent development of drug resistance of Pseudomonas aeruginosa [5].

Panobacumab is a fully human mAb, targeted against pseudomonal lipopolysaccharides, that was developed for the treatment of lung infections with the O11 serotype of Pseudomonas aeruginosa. In preclinical studies, panobacumab has been shown to reduce pulmonary bacterial load, reduce inflammatory markers and facilitate the entry of neutrophils into the lungs [3]. Panobacumab treatment also demonstrated synergistic effects in combination with conventional therapy and reduced the time to clinical resolution, without associated immunogenicity [7,5].

PcrV is a protein subunit of the Pseudomonas aeruginosa type III secretion system. The type III secretion system directly injects toxins into the cellular cytoplasm during infection. KB001 is a mAb fragment against PcrV, which was developed based on mAb166, a murine mAb against PcrV. In a clinical study in patients with cystic fibrosis with associated pseudomonas infection, KB001 showed moderate improvement in lung function and reduced the inflammatory marker IL-8 compared to placebo [7]. Another clinical study evaluating the safety of KB001 in 39 patients receiving mechanical ventilation showed that treatment was well tolerated in these patients and, very importantly, patients treated with KB001 were less likely to develop pneumonia with Pseudomonas aeruginosa, compared to the control group [3].

Psl is an exopolysaccharide with a role in biofilm formation and cell adhesion of Pseudomonas aeruginosa. MEDI3902 is a bispecific antibody that binds to PcrV and to Psl, and that has been shown to inhibit cell adhesion in vitro and to provide protection against infection in murine models of Pseudomonas aeruginosa infection. The safety and pharmacokinetics of a single MEDI3902 administration were evaluated in 56 healthy adults and no serious treatment-associated adverse events have been reported [3].

F429 is a mAb specific for alginate, a surface polysaccharide produced by Pseudomonas aeruginosa. MAb F429 for alginate effectively reduced corneal pathology and bacterial burdens in a model of bacterial conjunctivitis in mice [6].

Acinetobacter baumannii causes pneumonia associated with mechanical ventilation and bloodstream infections in hospitalized patients, and treatment options for some infections caused by this microorganism are limited.

Mouse monoclonal antibodies directed against two iron-regulated extra-membrane proteins were bactericidal and able to opsonize Acinetobacter baumannii in vitro and block siderophore-mediated iron uptake . In a separate study, the anti-capsular polysaccharide K1, mouse mAb 13D6, was able to opsonize K1-positive strains and reduce post-infection bacterial burden in a soft tissue infection model in rats [3]. C8, a mAb targeting capsular carbohydrates on the bacterial surface, improved survival in lethal bacterial sepsis and a model of mouse aspiration pneumonia and was also synergistic with colistin [8]. However, a recent study indicated that the capsular polysaccharide of Acinetobacter baumannii could inhibit the interaction between mAb and the target bacteria [3].

 Klebsiella pneumoniae is a leading cause of MDR nosocomial infections. The emergence of hypervirulent strains and those encoding broad-spectrum b-lactamases and carbapenemases make it difficult to treat these infections [3]. In cases of Klebsiella pneumonia infections, mAbs targeting capsular polysaccharides have been studied.

In a study, mAbs against capsular polysaccharide provided protection in murine sepsis and pulmonary model infection. Two mouse mAbs against the capsular polysaccharide of the hypervirulent ST258 strain have been shown to inhibit biofilm formation and facilitate complement and neutrophil recruitment and reduced bacterial spread after intratracheal infection with Klebsiella pneumoniae. Human mAb against lipopolysaccharide O-antigen have showed synergistic activity with meropenem and protective role in mouse models infection and low doses of human antibody against lipopolysaccharide O-antigen protected rabbits from ST258 strain infection. MAbs targeting MrkA, a major protein in the type III fimbriae complex, inhibited biofilm formation and provided protection in murine pulmonary models infection [3]

In a recent study, H3 and H4, two mAbs against peptide 5 of Hyr1 (a hyphae-regulated protein of Candida albicans), have shown cross-efficacy against infection with Gram-negative MDR bacteria. These mAbs block bacterial-induced endothelial cell damage and protect mice from lethal pulmonary infections mediated by Acinetobacter baumannii or Klebsiella pneumonia [9].

Escherichia coli pathogenic strains produce the Shiga-like II B toxin, that is responsible for organ damage in hemorrhagic colitis and hemolytic uremic syndrome (HUS). The treatment of HUS is complicated because antibiotics can aggravate the disease [4]. Eculizumab is a humanized mAb that was first approved in 2007 for use in nocturnal paroxysmal hemoglobinuria and later in 2011 for HUS. It blocks the formation of the complement pathway and protects host cells from damage, but increases the risk of meningococcal disease due to blockage of the terminal part of the complement pathway [10].

Monoclonal antibodies against multidrug-resistant Gram-positive bacteria

Staphylococcus aureus is a major human pathogen that colonizes about 30% of the human population. It can cause serious illnesses such as pneumonia, blood infections, osteomyelitis and complicated infections of the skin and soft tissues [11]. Staphylococcus aureus can attach and persist to host tissues (eg, heart valves and bones), as well as implanted materials (e.g., catheters) and can cause diseases such as endocarditis and osteomyelitis [12].
Methicillin-resistant Staphylococcus aureus (MRSA) has become a global problem and MRSA infections remain associated with high mortality, despite the availability of appropriate antibiotics [11].

In staphylococcal infections, mAbs could target both bacteria and disease-mediating toxins. Pagibaximab and tefibazumab are two mAbs that target staphylococcal virulence factors. Pagibaximab is a chimeric mAb specific for lipoteichoic acid (LTA) and has been studied to prevent infection in very low birth weight newborns. Tefibazumab targeting another virulence factor, protein clumping factor A (ClfA) [4].

Alpha-toxin (AT) is a pore-forming cytotoxin, which is an essential virulence factor for the development of staphylococcal pneumonia. Researchers have shown that passive administration of an anti-AT mAb, as well as vaccination, provides protection against pneumonia in mouse models [4]. MEDI4893 (suvratoxumab) is a high-affinity anti- (AT) mAb that is currently in the 2nd phase of clinical development to prevent Staphylococcus aureus pneumonia in mechanically ventilated patients colonized with Staphylococcus aureus in the lower respiratory tract [13,14].

ASN100 is an equimolar combination of two human monoclonal antibodies: ASN-1, which targets AT and four other leukocidins, and ASN-2, which neutralizes the 5th leukocidin, LukGH [11,12]. ASN100 blocked the cytolytic activity of Staphylococcus aureus in a 3D human model of lung tissue infection [11].

F598 is a mAb targeting poly-N-acetylglucosamine (PNAG) which is a conserved surface polysaccharide produced by major pathogens, including Staphylococcus aureus and Steptococcus pneumoniae. MAb was delivered systemically or intraconjunctivally in a mice model of bacterial conjunctivitis and reduced bacterial burdens and limited inflammatory lesions [6].

Streptococcus pneumoniae is an important extracellular pathogen that cause a variety of systemic diseases such as pneumonia, or ocular infections including keratitis and conjunctivitis [6]. The potential of radioimmunotherapy (RIT) against streptococcal infection has been studied. RIT was developed at first for the treatment of cancer, and uses the antigen-antibody interaction to delivered radionuclides that emit lethal doses of cytotoxic radiation. The mice treated with 213Bi-D11 survived at a higher percentage compared to control groups, while mice treated with Ci 213Bi-D11 demonstrated a survival rate of 87–100%. Radiolabeled D11 treatment was very well tolerated, with no observed weight loss in treated animals [4]. 

Clostridium difficile is anaerobic Gram-positive bacteria that causes intestinal infections and is the most common cause of nosocomial diarrhea in developed countries. Symptoms can range from mild diarrhea to fatal pseudomembranous colitis, rupture of the colon and can cause death. Because the disease occurs mainly in patients undergoing (or having recently followed) a broad-spectrum antibiotic treatment, clinical management of Clostridium difficile infection requires discontinuation of the offending antibiotic and initiation of treatment with metronidazole, vancomycin or fidaxomycin. Even when the treatment of the primary infection is successful, 20-30% of patients may have a recurrence of the disease after a few days or weeks [15].

Symptoms of Clostridium difficile infection are caused by two homologous exotoxins, TcdA and TcdB, expressed by pathogenic strains of Clostridium difficile. The toxins target the epithelial cells of the intestinal mucosa, enter cells through endocytosis and increase the permeability of the intestinal wall and the release of proinflammatory factors, such as interleukin 8 (IL-8). Hypervirulent strains of Clostridium difficil, overexpress both exotoxins, TcdA and TcdB. Actoxumab and bezlotoxumab are two human mAbs that bind to and neutralize TcdA and TcdB, respectively. In clinical trials, a combination of actoxumab-bezlotoxumab was co-administered with standard treatment, vancomycin and metronidazole. The results showed a 73% decrease in the rate of recurrence and a significant decrease in morbidity and mortality associated with Clostridium difficile infections [15].

In 2017, bezlotoxumab was authorized for use throughout the European Economic Area as an mAb against an infectious agent. It addresses Clostridium difficile toxin B and aims to prevent the recurrence of infection in adults at high risk of recurrence [3,13].


In the context of the increasing of the number of infections with MDR bacteria, mAbs-based therapies could be a promising approach to reducing the clinical and economic impact of these infections.

Despite the benefits of these therapies are proven, the major obstacle to the development of mAbs as antimicrobial drugs remain the economic factor. The research is focused on niche areas where there is sufficient need, urgency and a wide enough market to justify the development of mAbs therapies.

Several studies are needed to evaluate and develop the therapeutic potential of this class of drugs for MDR infections.


  1. World Health Organization, Global action plan on antimicrobial resistance, avaible at https://www.who.int/antimicrobial-resistance/global-action-plan/en/ 
  2. Bayer, V. (2019). An Overview of Monoclonal Antibodies. Seminars in Oncology Nursing 35
  3. McConnell, M.J.(2019). Where are we with monoclonal antibodies for multidrug-resistant infections?. Drug Discovery Today 24 (5), pp 1132-1138
  4. Saylor, C., Dadachova, E., Casadevall, A. (2009).  Monoclonal antibody-based therapies for microbial diseases. Vaccine 27S, pp 38–46
  5. Secher, T., Fas, S., Fauconnier, L., Mathieu, M., Rutschi, O. et al. (2013) The Anti-Pseudomonas aeruginosa Antibody Panobacumab Is Efficacious on Acute Pneumonia in Neutropenic Mice and Has Additive Effects with Meropenem. PLoS ONE 8(9): e73396. doi:10.1371/journal.pone.0073396
  6. Zaidi, T.S., Zaidi, T.  Pier, GB. (2018). Antibodies to Conserved Surface Polysaccharides Protect Mice Against Bacterial Conjunctivitis. Investigative Ophthalmology & Visual Science  59 (6), pp 2512-2519
  7.  Koulenti, D., Song, A., Ellingboe, A., Abdul-Aziz, MH., Harris, P., Gavey, E., Lipman, J. (2019).   Infections by multidrug-resistant Gram-negative Bacteria: What’s new in our arsenal and what’s in the pipeline?, International Journal of Antimicrobial Agents 53, pp. 211–224
  8. Nielsen, TB., Pantapalangkoor, P., Luna, BM., Bruhn, KW., Yan, J., Dekitani, K., Hsieh, S., Yeshoua, B.,  Pascual, B., Vinogradov, E., Hujer, K M.,  Domitrovic, TN., Bonomo, R A., Russo, TA., Lesczcyniecka, M., Schneider, T. and Spellberg, B. (2017). Monoclonal Antibody Protects Against Acinetobacter baumanni Infection by Enhancing Bacterial Clearance and Evading Sepsis. The Journal of Infectious Diseases 216, pp.489–501 
  9. Youssef, E.G., Zhang, L., Alkhazraji, S., Gebremariam,T., Singh, S., Yount, NY., Yeaman, MR., Uppuluri, P., and Ibrahim, AS. (2020) Monoclonal IgM Antibodies Targeting Candida albicans Hyr1 Provide Cross-Kingdom Protection Against Gram-Negative Bacteria. Front. Immunol. 11:76.doi: 10.3389/fimmu.2020.0007
  10. Walsh, P.R., Johnson, S. (2019) Eculizumab in the treatment of Shiga toxin haemolytic uraemic syndrome Pediatric Nephrology34:1485–1492 
  11. Rouha, H., Weber, S.,  Janesch, P., Maierhofer, B., Gross, K., Dolezilkova, I., Mirkina, I., Visram, ZC., Malaf S., Stulik, L., Badarau, A. & Nagy, N. (2018). Disarming Staphylococcus aureus from destroying human cells by simultaneously neutralizing six cytotoxins with two human monoclonal antibodies, Virulence, 9:1,231-247, DOI: 10.1080/ 21505594. 2017.1391447
  12. Raafat, D., Otto, M., Reppschläger, K., Iqbal, J., Holtfreter, S. (2019). Fighting Staphylococcus aureus biofilms with monoclonal antibodies. Trends Microbiol. 27(4), pp 303–322
  13. Pelfrene, E., Mura,M., Cavaleiro Sanches, A., Cavaleri, M. (2019). Monoclonal antibodies as anti-infective products: a promising future?, Clinical Microbiology and Infection 25 60-64
  14. Tkaczyk,C.,Semenova, E., Shi,Y.Y., Rosenthal, K., Oganesyan,V., Warrener,P., C. K. Stover, Sellmana, B.R. (2018). Alanine Scanning Mutagenesis of the MEDI4893 (Suvratoxumab) Epitope Reduces Alpha Toxin Lytic Activity InVitro and Staphylococcus aureus Fitness in Infection Models. Antimicrobial Agents and Chemotherapy. 62 (11)
  15. Yang, Z., Ramsey, J., Hamza, T., Zhang, Y., Li, S., Yfantis, H.G., Lee, D., Hernandez, L.D., Seghezzi, W., Furneisen, J.M., Davis, N.M., Therien, A.G., Feng, H. (2015). Mechanisms of protection against Clostridium difficile infection by the monoclonal antitoxin antibodies Actoxumab and Bezlotoxumab. Infect Immun 83, pp 822–831.