Bacterial resistance in samples of ear secretions from patients at a hospital in Angola

Introduction

Bacteria are an integral part of life on Earth. They are intrinsically linked to the life of the organism and the vast environment it inhabits, many of which are harmless, some are beneficial to the host, but under certain environmental conditions many, if not all, can cause infection[1].

Upper respiratory tract infection is one of the most common manifestations in medical practice, especially in children, and its symptoms are diverse, with the main categories of infection being pharyngitis, sinusitis and acute otitis media[2]. Acute otitis media is frequently associated with complications of upper respiratory tract infection, one of the main reasons for antibiotic prescription in children. Therefore, knowledge of it is of great importance to prevent the misuse of this class of drugs and to contribute to the positive selection of multidrug-resistant bacteria[3].

Acute otitis media (AOM) causes conductive hearing loss in children and adults, as well as delays in the development of speech, language, balance, and learning abilities, severely affecting the quality of life of children and their families. Therefore, identifying AOM and controlling risk factors is important for overall health in terms of quality of life and medical costs[4].

The impact of drug-resistant bacteria and the indiscriminate use of antibiotics in hospitals is a global problem that continues to concern the scientific community. This problem has intensified research aimed at raising awareness among healthcare professionals, including doctors and nurses, about the importance and need for the prudent use of antibiotics as a measure to minimize the emergence of antibiotic-resistant bacteria in hospital settings[5].

Antimicrobials are drugs that have the property of preventing the growth of pathogens or destroying them, and their use in clinical practice has altered the natural course and improved the prognosis of infectious diseases controlled by the use of these drugs[6].

It is estimated that 70% of upper respiratory tract infections are caused by resistant bacteria. Bacteria possess innate or acquired mechanisms to develop resistance to one or more classes of antimicrobials. Among the intrinsic mechanisms, genetic mutation and genetic recombination between bacteria stand out. The emergence of antibiotic resistance is a complex problem influenced by several factors, such as: environmental factors, the microorganism itself, and the use of antibiotics in humans and animals. These factors differ in developed and developing countries. Considering the lack of public administrative incentives, this justifies the scarcity of further research on antibiotics[7].

The fight against bacterial resistance as a global public health problem must be addressed from several aspects, such as understanding the processes related to antibiotic activity and the development of resistance, the planning, synthesis and pharmacological evaluation of new, more effective antimicrobial agents, the subsequent rational therapeutic application, and the adoption of standards for infection control in the hospital environment, representing different levels of continuous and interrelated activities[8].

The discretionary use of antibiotics should be a fundamental concern, especially in the health field. In this way, the specific use of antibiotics due to causes such as inconvenient prescriptions, unnecessary or widespread errors, incorrect periods and doses, when they could be prescribed according to the reality of the patient's case, is avoided. Failure in communication between doctor and patient also falls within this context and treatments that could be short-term become problems, sometimes even irreversible[9].

Antibiotic resistance has become one of the most important public health problems worldwide today, particularly in developing countries, such as Angola. This increase, which we have been aware of since at least the end of the 20th century, has triggered a massive global movement to limit the potentially catastrophic effects predicted[10].

Materials And Methods

Type and design of the study

Descriptive, retrospective, cross-sectional and quantitative study, carried out in the microbiology laboratory of the Benguela General Hospital.

Study population and sample

Ninety-nine (99) samples of otic secretion from patients treated at HGB, from January to April 2023, were analyzed. Cultures and antibiograms were performed in the microbiology laboratory in accordance with the guidelines for experimental studies.

Exclusion criteria included cultures from patients without TSA, as well as patients with other infections in any other organ or organ system, and patients taking antimicrobials.

Study variables:

The variables evaluated were: age range, sex and characteristics of the biological sample, such as: microbiological growth, type of microorganism, microbial agent, antimicrobial and susceptibility of the microorganism.

Antimicrobial Identification and Susceptibility:

To perform the correct identification, a systematic manual laboratory process was carried out, encompassing everything from the collection of material (optical secretion) to the identification of bacteria through the analysis of the data obtained. In this research, identification was based on the type of colony (macroscopic reading) and confirmation with Gram staining to differentiate Gram-positive or Gram-negative bacteria, morphology, and bacterial type.

After the antibiotic sensitivity test, to better guide the interpretation of the results, we used a table to standardize the diameter of the zones in relation to the quantity of microorganisms seeded and the concentration of the drugs, with the results presented as bacteria sensitive, intermediate, or resistant to the antimicrobial.

Data Analysis

The data were organized using percentage graphs to illustrate the main agents determining the infection and their resistance to the chosen antimicrobials.

Ethical Considerations

The study was approved by the Ethics Committee for Research (CEP) of ISPJPB, and the hospital unit authorized data collection.

Results

The results analyzed as positive for acute otitis media (AOM) showed a predominance of gram-positive microorganisms, particularly in women (62.07%, n=61). The age group most affected by these gram-positive microorganisms was 6 to 10 years (36.59%, n=36). However, the age groups of 2 to 5 years and 11 to 14 years were affected by gram-negative microorganisms, with 32.7% (n=32) respectively.

In graph no. 2, we observe the distribution of the groups of microorganisms identified in the optic culture and analyzed by the study in relation to the sex of the patients, with a predominance of otitis media in women, being 62.07% for gram-positive microorganisms and 51.22% for gram-negative microorganisms. In the case of men, the highest percentage was attributed to the group of gram-negative microorganisms, with 48.78%, exceeding the group of gram-positive microorganisms, 37.93%. Furthermore, the X2 test revealed statistically significant differences (p=0.001) between both sexes.

The predominant etiological agent was Staphylococcus aureus in 70.07% (n=71) of the gram-positive microorganisms, followed by Streptococcus, so the X2 test revealed statistically significant differences (p=0.001) between the groups. (Graphs 3).

In table no. 4 reflects the distribution of bacterial species of Gram-negative microorganisms present in the ear secretion samples, with Pseudomonas aeruginosa being the most predominant, at 39%, followed by Proteus vulgaris, at 22%, and Klebsiella pneumoniae, in a smaller percentage, at 2.4% ( Table. 4).

The antibiotic susceptibility analysis shown in graph 5 indicates that, in general, for both groups of microorganisms differentiated by Gram staining, susceptibility is higher for imipenem, with 46.55% for Gram-positive microorganisms and 41.46% for Gram-negative microorganisms, followed by cefotaxime, with 29.27% ​​for Gram-negative microorganisms and 18.97% for Gram-positive microorganisms. These data highlight the need to identify the microorganism causing the infection, as well as its drug sensitivity profile, to avoid inappropriate medication of the patient and the emergence of new multidrug-resistant bacteria. In general, the microorganisms were more sensitive to Imipenem (Table .5).

The analysis showed that third-generation cephalosporins were the drugs that exhibited resistance to all species of microorganisms when compared to the other antibiotics tested. Among the most sensitive antibiotics, imipenem was the most representative, demonstrating sensitivity to all strains. As can be seen in graph no. 6, for the bacterium Staphylococcus aureus, the most sensitive antibiotics were, in order of frequency, imipenem, cefotaxime, ceftriaxone, ceftazidime, and amikacin, with 48.8%, 19.5%, and 17.1%, respectively, with the last three being the most sensitive. At the intermediate level, imipenem, ciprofloxacin, amikacin, and doxycycline were the most frequent, with 41.5% and 24.4% of the remaining antibiotics, respectively. Resistance was most frequent to ciprofloxacin, doxycycline, and ceftriaxone (cefotaxime), with 58.5% for the first two and 36.6% for the last.

Discussion

Bacterial resistance, defined as a high probability of treatment failure even with increased exposure, has become a serious problem from a clinical and public health perspective. Isolation and identification of microorganisms in the laboratory are decisive evidence for the diagnosis and control of drug resistance[5].

Similar to data from the literature, the highest prevalence of acute otitis media (AOM) in this study was observed in women and children of pediatric age. Among Gram-positive microorganisms, the bacterium Staphylococcus aureus was the causative agent of AOM in this study (70.7%), with greater sensitivity to the antibiotic imipenem (48.8%) and resistance to the antibiotics ciprofloxacin and doxycycline (58.5%). This microorganism is the one that frequently colonizes the nasopharynx [11]. This higher percentage of resistance to this microorganism in isolates from children can be explained by the fact that antibiotic consumption is higher in this age group and the association between antibiotic consumption and the appearance of resistance is well established [12].

Some authors stated that 100% of the bacteria identified in their research were Gram-positive, with Streptococcus pneumoniae being the most frequent isolate (53.3%). Staphylococcus aureus and Streptococcus pyogenes constituted the majority, with 20% and 13.3% respectively [13].

According to Vaduva and colleagues, in their study, otitis externa is generally a polymicrobial infection. The most frequent etiological agents are Pseudomonas aeruginosa (38%), Staphylococcus epidermidis (9%) and Staphylococcus aureus (8%) [14].

Among Gram-negative microorganisms, the bacterium Pseudomonas aeruginosa showed the greatest sensitivity to the antibiotic Imipenem (31.3%). Resistance was observed to Gentamicin (62.5%), Amoxicillin and Cefotaxime, both with 56.3%.

Infections by Pseudomonas aeruginosa are widely associated with otitis externa, occurring in patients who have altered the integrity of the epithelium or who have removed the protective layer of wax by the use of cotton swabs, by itching or by the use of abrasive soaps. In these circumstances, exposure of the ear to water facilitates infection by Pseudomonas aeruginosa and other Gram-negative bacilli[15].

Regarding antibiotic sensitivity tests (AST) performed for Staphylococcus aureus in our research, a high sensitivity to imipenem was observed, close to 50%, with the highest intermediate level being above 40%. Therefore, considering that Staphylococcus aureus is the microorganism most frequently detected in the otic exudate sample in the investigation, this drug should be considered for the empirical treatment of acute otitis media (AOM) at the Benguela General Hospital, despite the high cost.

The medical journal Las Condes addresses the diagnosis and treatment of otitis externa, mentioning Staphylococcus aureus as one of the common pathogens that can cause this acute otitis media (AOM) [16]. For Staphylococcus aureus, the drugs that showed the greatest resistance were ciprofloxacin and doxycycline, with about 60%. Considering the recommendation not to use an antibiotic empirically when its resistance rate against a microorganism is greater than 20% [17], these medications should be avoided as treatment for acute otitis media (AOM) at Benguela General Hospital.

Conclusion

Staphylococcus aureus and Pseudomonas aeruginosa were the most prevalent bacteria causing acute otitis media (AOM) in patients treated at Benguela General Hospital. Although the antibiotic imipenem is the most effective against AOM-causing bacteria, a significant increase in bacterial resistance is observed among bacteria affecting the respiratory tract. Therefore, the use of antibiograms is necessary to prevent the increase in bacterial resistance in the Benguela hospital environment. This study made it possible to identify local pathogenic agents; This identification is extremely important clinically, since, together with the recognition of the sensitivity profile, it will allow the development of important therapeutic action protocols for a faster and more appropriate treatment of acute otitis media.