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.
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).