1.

Introduction neumonia affects 3-5 adults per thousand per year with a mortality of 7-14% in hospitalized patients (1). It is associated with high mortality. About 5.6 million cases of Community acquired pneumonia are reported in the United States each year, with an associated mortality rate of approximately 14% (2,3). Despite the advent of potent antibiotic over the last decades, significant mortality is still associated with pneumonia (4). Increased antibiotic resistance in frequently isolated bacterial pathogens from pneumonia patients has complicated the selection process of Author: Department of Medical Microbiology, Arba Minch University, Arba Minch, Ethiopia . e-mail: [email protected] antimicrobial agents (5) and the clinical presentation is usually not specific enough to make a firm etiologic diagnosis (6). The resistant strains of bacteria can quickly multiply and spread within a community where antibiotic use is common. Consequently, antibiotic resistance often results in various societal costs, including increased drug costs, additional health-service costs (such as laboratory tests and hospitalizations), greater drug resistance-related morbidity and mortality, and productivity losses (7). So it is wise to determine antimicrobial susceptibility pattern of bacterial pathogens and this might help for the management of the case in case of emergency and helps for the rational utilization of antimicrobial agents.

During the period February to December 2013 a total of 170 adults (above 15 years old) with typical symptoms of the disease, such as productive cough, fever, chest pain and the presence of consolidate on the chest radiograph consistent with pneumonia was included in this study. Sputum samples were inoculated onto Blood, MacConkey, Manitol Salt agar (MSA) and Chocolate agar (Oxoid Ltd, UK) plates (8). The bacterial isolates were then identified and subjected to antimicrobial susceptibility testing according to Clinical Laboratory Standards Institute (CLSI) recommendations (9,10).

The antibiotic discs used and their concentration were:-Ceftriaxone (CRO, 30?g), Ciprofloxacin (CIP, 5?g), Tetracycline (TE, 30?g), Chloramphenicol (C, 30?g), Erythromycin (E, 15?g), Doxycycline (DO, 30µg), Penicillin (P, 10µg), Gentamycin (CN, 10?g), Trimethoprim-sulfamethoxazole (TMP-SMX, 1.25+23.75?g), Ampicillin (AMP, 10µg) and Oxacillin (OXA, 1?g) All antibiotic were obtained from Oxoid Limited, Basingstoke Hampshire, UK. A standard inoculum adjusted to 0.5 McFarland was swabbed on to Muller-Hinton agar (Oxoid Ltd. Bashingstore Hampaire, UK); antibiotic disc were dispensed after drying the plate for 3-5 min and incubated at 37 o C for 24 hours. For S. pneumoniae, MHA supplied with 5% sheep blood and for H. influenzae, MHA chocolate agar was used.

Quality control strains that were used include: 27853 (10). Selected Socio-demographic characteristics like age and sex were obtained. Data were entered and analyzed using SPSS version 16.0 computer software.

The proposal of this study was ethically approved by the Institutional Ethical Review Committee (IRC) of Arba Minch University. Permission was obtained from Medical director of Arba Minch Hospital. Written informed consent was obtained from each patient participated in the study.

A total of 170 adult patients clinically diagnosed to have pneumonia in Arba Minch Hospital were selected and participated in this study (Table 1). Of these, 95 (55.9%) were males and 75 (44.1%) were females. The isolated bacteria were, Streptococcus pneumoniae 20 (11.8%), Staphylococcus aureus 18 (10.6%), Pseudomonas aeruginosa 12 (7.1%), Klebsiella pneumoniae 11 (6.5%), Escherichia coli 5 (2.9%), Proteus mirabilis 2 (1.2%), Proteus vulgaris 1 (0.6%) and Haemophilus influenzae 4 (2.4%).

Streptococcus pneumoniae isolates showed relatively high resistance (60%) to Oxacillin (penicillin group representative) and all isolates were sensitive against Trimethoprim-sulfamethoxazole. High resistance rate S. aureus was observed to Tetracycline (100%), Oxacillin (83.3%), Ampicillin (83.3%), Penicillin (83.3%), Trimethoprim-sulfamethoxazole (83.3%), Erythromycin (50%) and Doxycycline (50%). Pseudomonas aeruginosa isolates showed that 50% resistant to Gentamycin. The antimicrobial testing of K. pneumoniae and H. influenzae isolates indicated that all isolates showed resistance (100%) to Tetracycline, Ampicillin and Trimethoprim-sulfamethoxazole. Proteus and E. coli isolates showed resistance to Tetracycline, Chloramphenicol, Doxycycline, Gentamycin, Ampicillin and Trimethoprim-sulfamethoxazole (Table 2). Multidrug resistance was also observed to a number of antimicrobial agents (Table 3) IV.

The importance of knowing susceptibility patterns of bacterial isolates in patients with pneumonia has been identified as a key step towards limiting unnecessary antibacterial prescribing and treating patients effectively, which was the main purpose of this study.

S. pneumoniae, which was the commonest isolate in this study, showed 60% resistant to oxacillin which is representative to penicillin group. This finding is comparable to studies conducted in USA (53%) (11) and Iran (30-57%) (12). In this study, most tested S. pneumoniae isolates showed that 95% susceptible to trimethoprim-sulfamethoxazole, but studies conducted in Nigeria (100%) (13) and Kenya (54%) (14), showed high resistance rate of S. pneumoniae to trimethoprimsulfamethoxazole. In addition, 95% of tested S. pneumoniae isolates were susceptible to chloramphenicol and erythromycin. These findings are comparable to a study conducted in Kenya (>97%) (14). The second most causative agent S. aureus showed 77.8% susceptible to ceftriaxone and ciprofloxacin, and 72.2% to gentamycin and chloramphenicol. This result is comparable to studies conducted in Ibadan, Nigeria (66.7% ciprofloxacin and 66.7% gentamycin) (13) and Benin City, Nigeria (66.7% ceftriaxone, 66.7% ciprofloxacin, and 66.7% chloramphenicol) (15). In addition 83.3% of tested S. aureus showed resistance to penicillin, ampicillin, oxacillin and trimethoprim-sulfamethoxazole; which is comparable to studies conducted China (88.7% resistance to penicillin) (16) and Nigeria (resistance rate of 66.7% for penicillin) (13), but lower than study conducted in Nigeria (100% for trimethoprimsulfamethoxazole) (13).

Most of tested gram negative bacilli isolates were sensitive (90%) to ceftriaxone and ciprofloxacin. These findings are comparable to studies conducted in Benin City, Nigeria (66-100%) (15) and Ibadan, Nigeria (60-100%) (13). Majority of gram negative bacilli was resistance (100%) to tetracycline, chloramphenicol, doxycycline (except K. Pneumoniae, 90% susceptible), trimethoprim-sulfamethoxazole and ampicillin. Similar study conducted in Nigeria (60-100%) (15), supports these findings. The commonest causative agent among gram negative bacilli, P. aeruginosa, showed 58.3% resistance to gentamycin, which is comparable to study conducted in Nigeria (53.6%) (13). However, it showed low resistance (8.3%) to ceftriaxone and ciprofloxacin; ciprofloxacin) (13), showed high resistance. K. pneumoniae and E. coli showed 100% resistance to tetracycline, ampicillin and trimethoprim-sulfamethoxazole. These findings are comparable to studies conducted in Benin City, Nigeria (100% resistance to tetracycline) (15) and Ibadan, Nigeria (100% resistance to trimethoprim-sulfamethoxazole) (13). All tested Proteus species isolates were resistance (100%) to doxycycline, tetracycline, ampicillin and trimethoprimsulfamethoxazole. These findings are comparable to study conducted in Ibadan, Nigeria (100% resistance to trimethoprim-sulfamethoxazole) (13).

All H. influenzae isolates tested for antimicrobial sensitivity showed low resistance (25%) to ceftriaxone, ciprofloxacin and chloramphenicol. These findings are comparable to study conducted in Nigeria (chloramphenicol 30.3% and ciprofloxacin 26.1%) (13).

In most of tested H. influenzae isolates, high resistance rate to tetracycline (100%), ampicillin (50%) and trimethoprim-sulfamethoxazole (100%) were observed. These findings are similar with studies conducted in USA (47% resistance to ampicillin) (17) and Nigeria (93.7% resistance to trimethoprim-sulfamethoxazole) (13), but is not as high as that observed in other countries such as in China (>90% susceptibility to most antibiotics) (16).

The differences in antibiotic resistance patterns may be due to variations in the antibiotic prescribing habits in different geographical regions.

V.

In the present study, most bacterial isolates were susceptible to ceftriaxone and ciprofloxacin. However, antimicrobial resistance including Multidrug resistance was observed to a number of commonly used antibiotics, such as trimethoprimsulfamethoxazole, penicillin group and doxycycline. Hence, it is important to periodically monitor the antibiotic resistance patterns to aid physicians to choose empirical treatments for better management of pneumonia.

VI.