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Pseudomonas aeruginosa is an ubiquitous, Gram-negative, rod-shaped, monoflagellated bacterium, capable of causing serious infections in immunocompromised host. It is one of the most difficult multidrug resistant microorganisms capable of producing metallo-β-lactamase (MBL). Though a notorious organism, its identification should not be limited to pigment production alone, as some strains do not produce pigments. This study was aimed at evaluating the increasing prevalence of multidrug resistance profile and MBL production in P. aeruginosa isolated from nasal cavity of cattle from Kara market, Ogun state, Nigeria.


In this study, a total of 570 samples were randomly collected from the nasal cavity of healthy male and female cattle using sterile swab sticks. They were tested for the presence of P. aeruginosa on cetrimide agar, observing the agar plates for growth and pigmentation. Further biochemical test and molecular analysis were carried out to further confirm their identity as P. aeruginosa. The antibiogram was determined using ceftazidime, cefroxime, gentamicin, ciprofloxacin, ofloxacin, augumentin, nitrofurantouin, ampicillin, imipenem and meropenem discs. Carbapenems (meropenem and imipenem) discs combined with EDTA were used to test for the production of MBL in P. aeruginosa.


A total of 439 samples were found to be positive for Pseudomonas out of the 570 samples collected. Of these positive samples, 229 isolates were from female cattle (31.0% showing pigment production and 68.9% non-pigment producers) and 210 isolates were from the male cattle (48.57% showing pigment production and 51.43% non-pigment producers). Isolates obtained from the female cattle showed 69.01% (pigment producers) and 82.28% (non-pigment producers) multidrug resistance while 75.49% (pigment producers) and 84.26% (non-pigment producers) were multidrug resistant among the isolates from the male cattle. In determining MBLs production, 47.84% were positive for MBL production using the IMP+EDTA and 75.50% were positive for MBL using the MER+EDTA.


From this study, it was concluded that multidrug resistant P. aeruginosa is present in the nasal cavity of cattle and its presence could be detrimental to the cattle, cattle herders, beef handlers and consumers. The level of resistance was high in both pigment and non-pigment producing isolates, though the resistance of non-pigment producing P. aeruginosa was higher. Drugs of choice to be considered first for the treatment of infections caused by multidrug resistant P. aeruginosa are gentamicin, ofloxacin, ciprofloxacin and meropenem. Nitrofurantoin is expensive and not easily purchased hence they are to be considered as the last drug of choice at extreme cases.

Keywords:Pseudomonas.aeruginosa, Carbapenem, resistance, Metallo-beta-lactamase, Cattle.

Word Count: 394



Content                                                                                                                                   Page

Title page                                                                                                                                i

Certification                                                                                                                            ii

Dedication                                                                                                                              iii

Acknowledgements                                                                                                                iv

Abstract                                                                                                                                  v

Table of Contents                                                                                                                   vi

List of Tables                                                                                                                          vii

List of Figures                                                                                                                         viii

List of Plates                                                                                                                           ix


1.1       Background to the Study                                                                                           1

1.1.1    Pseudomonas aeruginosa                                                                                           1

1.1.2    Multidrug resistant Pseudomonas aeruginosa                                                            2

1.1.3    Carbapenems                                                                                                               2

1.1.4    Metallo-beta-lactamase                                                                                               3

1.2       Statement of the Problem                                                                                           3

1.3       Objective of the Study                                                                                               4

1.4       Research Questions                                                                                                     5

1.5       Significance of the Study                                                                                           5

1.6       Justification for the Study                                                                                          5


2.1       Pseudomonas aeruginosa                                                                                           6

2.2       Mechanism of Multidrug Resistance of P. aeruginosa                                              7

2.2.1    Production of Antibiotic-inactivating Enzymes (Beta-lactamases)                            7

Content                                                                                                                                   Page

2.2.2    Decreased Permeability of the Outer Membrane                                                        8

2.2.3    Efflux Pumps System                                                                                                 8

2.2.4    Biofilms formation                                                                                                      8

2.3       Infections Caused by P. aeruginosa                                                                           9

2.3.1    Central Nervous System infections                                                                            10

2.3.2    Ear Infections including External Otitis                                                                     10

2.3.3    Eye Infections                                                                                                             10

2.3.4    Bone and Joint Infections                                                                                           11

2.3.5    Urinary Tract Infections                                                                                             11

2.3.6    Gastrointestinal Infections                                                                                          11

2.4       Pigmented and Non-pigmented P. aeruginosa                                                          11

2.5       Caberpenem                                                                                                                12

2.5.1    Mechanism of Action                                                                                                 13

2.5.2    Microbiological Activity                                                                                             13

2.5.3    Mechanisms of Resistance against Caberpenems                                                       13

2.5.4    Types of Carbapenem                                                                                                 14

2.6       Metallo-Beta-Lactamase                                                                                             16

2.6.1    Verona Integron-encoded Metallo-β-lactamase (VIM)                                              16

2.6.2    Imipenemase (IMP)                                                                                                    17

2.6.3    New Delhi Metallo-β-lactamase (NDM)                                                                    17

2.7       Imipenem                                                                                                                    17

2.7.1    Mechanisms of Resistance                                                                                          17

2.8       Meropenem                                                                                                                 18


Content                                                                                                                                   Page


3.1       Research Design                                                                                                         20

3.2       Population                                                                                                                   20

3.3       Sample size and sampling Technique                                                                          20

3.4       Sample Processing                                                                                                      21

3.5       Identification of the Isolates                                                                                      22

3.5.1    Gram Staining                                                                                                             22

3.5.2    Catalase Test                                                                                                               22

3.5.3    Molecular Analysis                                                                                                     22

3.6       Antibiotics Sensitivity Test                                                                                         24

3.7       Phenotypic Screening for Metallo-β-Lactamase (MBL)                                             25

3.8       Statistical Analysis                                                                                                      25



4.1       Result                                                                                                                          26

4.1.1    Source Distribution of Isolates                                                                                   26

4.1.2    Molecular Identifications of the Isolates                                                                    30

4.1.3    Antibiotic Sensitivity Testing                                                                                     32

4.1.4    Multidrug Resistance (MDR) Profile                                                                         37

4.1.5    Carbapenem Susceptibility, Resistance and Intermediate Profile                              39

4.1.6    Metallo-beta-lactamase Profile                                                                                   41

4.2       Discussion                                                                                                                   43

4.2.1    Introduction                                                                                                                43


Content                                                                                                                                   Page

4.2.2    Distribution and attribute of P. aeruginosa                                                                43

4.2.3    Metallo-beta-lactamase Production                                                                            44

4.2.4    Antibiotic Sensitivity Testing                                                                                     44


5.1       Summary                                                                                                                     46

5.2       Conclusion                                                                                                                  47

5.3       Recommendations                                                                                                      47

5.4       Contribution to Knowledge                                                                                        47

REFERENCES                                                                                         49

APPENDIX                                                                                                61


Table                                                                                                                                       Page

4.1: Distribution of carbapenem susceptibile, resistant and intermediate susceptible

Profiles of the isolated Pseudomonas aeruginosa from cattle                                        40


Figure                                                                                                                                      Page

4.1: Source distribution of Pseudomonas isolated from nasal cavity of cattle                       27

4.2: Varying Pigment Production by P. aeruginosa isolated from the nasal

cavity of Female and Male Cattle                                                                                    28

4.3: Distribution of susceptibility profile of pigment producing P.aeruginosa

from the female animals                                                                                                   33

4.4: Distribution of susceptibility profile of non-pigment producing P.aeruginosa

from the female animals                                                                                                    34

4.5: Distribution of susceptibility profile of pigment producing P.aeruginosa

from the male animals                                                                                                       35

4.6: Distribution of susceptibility profile of non-pigment producing P.aeruginosa

from the male animals                                                                                                      36

4.7: Multidrug resistance profile of P. aeruginosa isolated from the nasal cavity

of female and male cattle                                                                                                  38

4.8: Distribution of MBL production in P. aeruginosa isolated from cattle                          42


Plate                                                                                                                                        Page

4.1: 18-24 hours growth of Pigment and Non-pigment producing

Pseudomonas sp. Cultured on Cetrimide Agar                                                                      29

4.2:Electrophoregram of PCR product obtained

using PGSS primers for Pseudomonas species                                                                31



1.1       Background to the Study

Cattle are the most common and largest domesticated animal in the world (Bollongino,2012). They are reared for meat, milk and other dairy products. According to an estimate from 2011, there are about 1.4 billion cattle in the world. In 2009, cattle became one of the first livestock animals to have a fully mapped genome(Brown, 2009). They are herbivores because they feed on grasses, legumes and roughage. They are also known as ruminants because they have one stomach with four compartments. In Nigeria (West Africa), commercial beef cattle production is common especially in the Northern part of the country (Bollongino, 2012).

Pseudomonas aeruginosa (P. aeruginosa) is a bacterium capable of causing serious infections in cattle e.g. mastitis. It is found in the milk of cattle because it requires few nutrients to grow and multiply. Water supplies, contaminated drugs and infusion equipment are the major sources of this organism. It has also been isolated from waste feed, soil, manure and animal skin. Cows that are immunologically compromised due to other infectious diseases or are nutritionally deficient are also more susceptible to P. aeruginosa infections. The bacterium is resistant to antibiotics (John & Roger, 2011). In 2005, Haydar was able to isolate some bacteria causing pneumonia from the nasal cavity of healthy cattle especially in animals suffering from defects in their immune status or stressed (Haydar, 2005). About 2.43% of the isolates were Pseudomonas species. This showed that Pseudomonas aeruginosa can be an infectious agent in cattle and can be transmitted as zoonotic infection (Haydar, 2005).

  • Pseudomonas aeruginosa

Pseudomonas aeruginosa is a Gram-negative, rod-shaped, monoflagellated bacterium ranging from about 1-5 µm long and 0.5-1.0 µm wide (Lederberg, 2000).  They are ubiquitous microorganism that can be isolated from soil, water, humans, animals, plants, sewage, and hospitals (Lederberg, 2000). Itis an opportunistic human pathogen which often colonizes immunocompromised patients such as those with cystic fibrosis, cancer or AIDS (Botzenhardt et al., 1993). Itis the second leading cause of Gram-negative nosocomial infections (Carmeli et al., 1999) carrying a 40-60% mortality rate (Fick, 1993). It has a natural resistance mechanism to many antibiotics because of a resistance transfer plasmid, extra genetic material carried in the cells with genes that code for proteins that destroy antibiotic substances (Madigan & Martinko 2006).

1.1.2    Multi-drug resistantPseudomonas aeruginosa

Multi-drug resistant (MDR) P. aeruginosa are organisms resistantto one antimicrobial agent in three or moreantipseudomonal antimicrobial classes(carbapenems, fluoroquinolones, penicillins/cephalosporins and aminoglycosides)(Magiorakos et al., 2011). Multi-drug resistance in P. aeruginosa arises from low outer membrane permeability, multidrug efflux systems which accounts for its intrinsic mechanisms of resistance, enzyme production, target mutations (Kotra et al., 2000) and biofilm formation (Carmeli et al., 2002). In addition to these factors, other bacterial exoproducts contributing to multidrug resistance in P. aeruginosa arelipopolysaccharides and elastase which induce harmful pathogenesis resulting in tissue destruction.  Apart from enabling motility, the flagellum of P. aeruginosa plays an indirect role in membrane permeabilization and surfactant protein-mediated bacterial clearance (Zhang, 2007). MDR P. aeruginosa are very problematic because of its inherent resistance to many drug classes andability to acquire resistance to all effectiveantimicrobial agents (Gad et al., 2007).

1.1.3    Carbapenems

Carbapenems are β-lactam group of drugs that are usually used as antibiotics of last resort for treating infections due to multiple-resistant Gram-negative bacilli. Often times, the stable response of P. aeruginosa to extended-spectrum β-lactamases has changed due to the emergence of metallo-β-lactamase (MBL)-producing strains (Jesudason et al., 2005). They bear a penemic together with the beta-lactam ring inhibiting bacterial cell wall synthesis by binding to and inactivating Penicillin Binding Proteins (PBPs).

Multi-drug resistant (MDR) P. aeruginosa are capable of producing enzymes that can inactivate beta-lactams such as metallo-β-lactamase (MBL) which is responsible for a significant proportion of carbapenem resistance in these bacteria (Moya et al., 2009, Borgianni et al., 2010). These enzymes can hydrolyse all classes of β-lactam drugs and withstand neutralization by β-lactamase inhibitors (Wan Nor Amilah et al., 2012). Imipenem, panipenem, meropenem, biapenem, ertapenem, doripenem and tebipenem belong to the carbapenem family. Each one present different characteristics that influence their way of administration and their usefulness as anti-pseudomonal agents.Carbapenem resistance mechanisms in P. aeruginosa may be classified as enzymatic, mediated by carbapenemases (beta-lactamases hydrolyzing carbapenems among other beta-lactams). Carbapenem resistance, however, develops frequently due to the concomitant presence of more than one mechanism (El Amin et al., 2005; Hammami et al., 2009). Another resistant mechanism of P. aeruginosa to carbapenem is the reduction of outer membrane (OM) permeability through alterations in or decreased production of outer membrane porin D (OprD). This porin allows the cellular entry of carbapenems (Farra et al., 2008).

1.1.4    Metallo-Beta-Lactamase

Metallo-beta-lactamases (MBLs) are enzymes that make bacteria resistant to a broad range of beta-lactam antibiotics one of which includes the cabapenem family (Kumarasamy et al., 2010). They belong to class B of the structural classification of β-lactamases and are able to efficiently hydrolyze all β-lactams with the exception of monobactams (Yan et al., 2006; Gutierrez et al., 2007; Palzkill, 2013). The enzymes require divalent cations, usually zinc, as metal cofactors for enzyme activity and are inhibited by metal chelators such as ethylenediamine tetra acetic acid (EDTA) (Maltezou, 2009). MBLs are encoded either by genes that are part of the bacterial chromosome in some bacteria or by heterologous genes acquired by transfer of mobile genetic elements. Therefore, acquired MBL can be spread among various strains of bacteria such as P. aeruginosa (Cornaglia et al., 2011).

 1.2      Statement of the Problem

            Scientifically, P. aeruginosa is known to be a notorious organism because it is highly resistant to virtually all antibiotics. Infections to which it is implicated are always difficult to treat. This may be as a result of most virulence factors and mechanisms of resistance in P. aeruginosa. Although P. aeruginosa is ubiquitous, pathogenic and possibly a zoonotic agent, there is a death of information on its isolation from domesticated animals especially asymptomatic cattle and the susceptibility of these isolates from cattle to different antibacterial agents. Though cattle are not carriers of P. aeruginosa, they are often infected by them (mastitis being the most common infection). The presence of multidrug resistant P. aeruginosa poses a threat not only to the cattle but also to the cattle herders, beef retailers, beef handlers and beef consumers.

Consequently, this study will determine

  1. The possibility of isolating pathogenic pseudomonas from the nasal cavity of healthy cattle as against the expected Staphylococcus aureus which are usually considered natural microflora of the nasal cavity.
  2. Whether the different antibiotics readily available would be effective in inhibiting the growth of aeruginosa strainsisolated from the nasal cavity of cows or not for effective therapy in infections.
  3. The multi-drug resistant profile of aeruginosa isolated from cattle
  4. If the isolates are capable of producing metallo-beta-lactamase which is a resistance mechanism and to what extent or degree.

1.3       Objective of the Study

The general objective of this study is to educate the public on the presence of P. aeruginosa if isolated and to evaluate the increasing prevalence of multi-drug and carbapenem resistant P. aeruginosa isolated from cattle in Kara market, Ogun State, Nigeria. The specific objectives are to:

  1. isolate aeruginosa from the nasal cavity of male and female cattle;
  2. identify aeruginosa from the nasal cavity of male and female cattle;
  3. determine whether all strains of aeruginosa are pigment producing or non-pigment producing P. aeruginosa ;
  4. determine the antibiogram of the isolates and compare the antibiotic resistant pattern between the pigment producing aeruginosa and non-pigment producing P. aeruginosa;
  5. determine metallobeta-lactamase production in the isolated aeruginosa from nasal cavity of asymptomatic cattle.



1.4       Research Questions

  1. Can aeruginosa be isolated from the nasal cavity of healthy cattle?
  2. How is aeruginosa identified when isolated from the nasal cavity of healthy cattle?
  3. Are non-pigmented Pseudomonas truly aeruginosa
  4. How can the isolated pigment producing aeruginosa bedifferentiated from the non-pigment producing P. aeruginosa?
  5. How are the multiple antibiotic resistance index of the isolate calculated using the antibiogram of the isolate?
  6. How is the test for metallo-beta-lactamase carried out?

1.5       Significance of the Study

This study would possibly indicate cattle as a nasal carrier of Pseudomonas aeruginosa and indicate the susceptibility profile of the isolates. It would also, educate the general public on the danger of negligence of multidrug resistant P. aeruginosa in cattle and its effect in eating undercooked beef as well as providing a more recent data on the increasing prevalence of resistance in multidrug resistant P. aeruginosa.

1.6       Justification for the Study

This study will most importantly provide baseline information and a more recent epidemiological data on the increasing prevalence of multi-drug resistant P. aeruginosa resulting from cattle.




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