Antibiotic susceptibility testing of isolates showed high resistance rate to Cephalothin
A strain belonging to Enterobacter cloacae, Enterobacter aerogenes (now newly named as Klebsiella aerogeties) or Citrobacter freundii group will virtually always present full resistance to ampicillin, cephalothin
, and cefoxitin due to low level of chromosomal AmpC enzyme expression.
In addition, the side chain of older cephalosporin members (e.g., cephalothin
, cephaloridine, and cefamandole) is similar to that of penicillin (5) thus increasing the risk of cross-reactivity and type IV allergic reaction with penicillin and its derivatives.
Usage of ampicillin, cephalothin
, tetracycline and chloramphenicol have been shown to suppress alpha haemolytic streptococci and promote the emergence of gram-negative enteric organisms.
Results of previous aerobic bacterial culture and sensitivity results showed a methicillin-resistant Staphylococcus aureus (MRSA), with sensitivity to chloramphenicol, doxycycline, gentamicin, and trimethoprim/sulfa and resistance to amikacin, cephalothin
, cefotaxime, ciprofloxacin, enrofloxacin, orbifloxacin, penicillin, and piperacillin.
Of the 51 strains examined, 46 (90.19%) were sensitive to Amoxycillin/ Clavulonic acid, 40 (78.43%) to Gentamicin, 39 (76.47%) to Ampicillin/ Sulbactam, 31 (60.78%) to Enrofloxacin, 30 (58.82%) to Nitrofurantoin, 29 (56.86%) to Kanamycin, 28 (54.90%) to Oxytetracycline, 26 (50.98%) to Cephalothin
and Danofloxacin and 23 (45.09%) to Sulphamethoxazole/Trimethoprim.
The following drugs and concentrations were used to determine the antibiogram of the strains: penicillin (10 U), augmentin (30 [micro]g), trimethoprim-sulfamethoxazole (1.25/23.75 [micro]g), clindamycin (30 [micro]g), gentamicin (30 [micro]g), ciprofloxacin (5 [micro]g), erythromycin (15 [micro]g), chloramphenicol (30 [micro]g), cefuroxime (30 [micro]g), cephalothin
(10 [micro]g), ceftazidime (30 [micro]g), cefotaxim (30 [micro]g), ceftriaxone (10 [micro]g), oxacillin (1 [micro]g), nitrofurantoin (30 [micro]g), nalidixic acid (30 [micro]g), and norfloxacin (30 [micro]g).
coli isolates' resistance to ampicillin and cephalothin
(84.6%), chloramphenicol (83.3%), tetracycline (88.9%), and gentamicin (65.9%) reported by  in Tigray, Ethiopia.
Brain Heart Infusion (BHI) agar, Brain Heart Infusion (BHI) broth, Skirrow's supplement (SR69) Oxoid England, glycerol, cephalothin
(30 [micro]g), and nalidixic acid (30 [micro]g) antibiotic disc were obtained from Mast Group Ltd., Merseyside, UK.
The antimicrobial susceptibility testing was done by using Kirby-Bauer disc-diffusion technique on Mueller-Hinton agar according to the CLSI guidelines 2014  for the following antimicrobial discs: amoxicillin/clavulanic acid (20/10 [micro]g), cefotaxime (30 [micro]g), ceftriaxone (30 [micro]g), ceftazidime (30 [micro]g), ampicillin (10 [micro]g), cephalothin
(30 [micro]g), ciprofloxacin (5 [micro]g), nalidixic acid (30 [micro]g), norfloxacin (10 [micro]g), gentamycin (10 [micro]g), amikacin (30 [micro]g), tetracycline (30 [micro]g), trimethoprimsulfamethoxazole (1.25/23.75 [micro]g), imipenem (30 [micro]g), and chloramphenicol (30 [micro]g) (Oxoid; UK).
Susceptibility (MIC, Reference Antibiotic [micro]g/mL) * number Aminobenzyl-penicillin Amoxicillin R (>16)  Ampicillin R (>16) , current case [beta]-Lactam/ [beta]-lactamase inhibitors Amoxicillin-clavulanate R (8/4)  Ampicillin-sulbactam R (>16/8) Current case Cephalosporins (1st generation) Cefazolin R (>16) Current case Cephalothin
R ([paragraph])  Cephalosporins (2nd generation) Cefoxitin R (>16) Current case Cefuroxime I (16) Current case Polymyxins Colistin R ([paragraph])  Resistance mechanism encoded in C.