Sensitivity Pattern Of Salmonella typhi And Paratyphi A Isolates To Chloramphenicol And Other Anti-Typhoid Drugs: An In Vitro Study

Figures & data

Table 1 Minimal Inhibitory Concentration Breakpoints For Salmonella Species (CLSI 2018)

Antimicrobial Agent	Interpretive Categories And MIC Breakpoints (µg/mL)
	Sensitive	Intermediate	Resistant
Ceftriaxone	≤1	2	≥4
Cefixime	≤1	2	≥4
Azithromycin	≤16		≥32
Ofloxacin	≤0.12	0.25-1	≥2
Chloramphenicol	≤8	16	≥32

Figure 1 Zone-wise distribution of Salmonella isolates.

Table 2 Comparison Of Antibiotic Susceptibility Of Chloramphenicol Versus Other Anti-Typhoid Drugs In Salmonella Isolates

Antibiotics	Sensitive		Intermediate		Resistant
	n (%), (95% CI)	Percentage Difference, (95% CI), (P-value)	n (%), (95% CI)	Percentage Difference, (95% CI), (P-value)	n (%), (95% CI)	Percentage Difference, (95% CI), (P-value)
Chloramphenicol	237 (94.4)^a, (90.82, 96.92)	NA	0, (NA)	NA	14 (5.6), (3.08, 9.18)	NA
Cefixime	251 (100.0), (98.54, 100.00)	−5.6 (−8.42, −2.74), (0.0001)*	0, (NA)	NA	0, (NA)	NA
Ofloxacin	09 (3.6), (1.65, 6.70)	90.8 (87.18, 94.49), (<0.0001)*	170 (67.7)^b, (61.56, 73.47)	NA	72 (28.7), (23.17, 34.71)	−23.1 (−29.38, −16.83) (<0.0001)*
Azithromycin	251 (100.0), (98.54, 100.00)	−5.6 (−8.42, −2.74), (0.0001)*	0, (NA)	NA	0, (NA)	NA
Ceftriaxone	251 (100.0), (98.54, 100.00)	−5.6 (−8.42, −2.74), (0.0001)*	0, (NA)	NA	0, (NA)	NA

Notes: The P-value was calculated using Z test statistic. *The percentage difference (chloramphenicol – other anti-typhoid drugs) was statistically significant. ^aHigher percentage of isolates were chloramphenicol-sensitive compared to chloramphenicol-resistant (P< 0.0001). ^bHigher percentage of isolates were ofloxacin-intermediate compared to ofloxacin-sensitive/-resistant (P< 0.0001).

Abbreviations: CI, Confidence Interval; NA, Not Applicable.

Table 3 Zone-Wise Susceptibility Analysis

Zone	Chloramphenicol	Cefixime	Ofloxacin	Azithromycin	Ceftriaxone
	S. typhi susceptible/total isolates (percentage susceptibility)
East (n = 42)	40 (95.24)	42 (100.00)	3 (7.14)	42 (100.00)	42 (100.00)
North (n = 58)	53 (91.38)	58 (100.00)	4 (6.90)	58 (100.00)	58 (100.00)
South (n = 38)	34 (89.47)	38 (100.00)	1 (2.63)	38 (100.00)	38 (100.00)
West (n = 54)	51 (94.44)	54 (100.00)	1 (1.85)	54 (100.00)	54 (100.00)
	S. paratyphi A susceptible/total isolates (percentage susceptibility)
East (n = 8)	8 (100.00)	8 (100.00)	0 (NA)	8 (100.00)	8 (100.00)
North (n = 18)	18 (100.00)	18 (100.00)	0 (NA)	18 (100.00)	18 (100.00)
South (n = 12)	12 (100.00)	12 (100.00)	0 (NA)	12 (100.00)	12 (100.00)
West (n = 21)	21 (100.00)	21 (100.00)	0 (NA)	21 (100.00)	21 (100.00)

Table 4 Minimum Inhibitory Concentration (µg/mL) Of Anti-Typhoid Drugs

Statistics	ChloramphenicolN = 251	CefiximeN = 251	OfloxacinN = 251	AzithromycinN = 251	CeftriaxoneN = 251
Mean ± Standard deviation	3.8880±6.94286	0.1315±0.10688	2.9518±6.06327	3.3187±2.19397	0.1053±0.17695
Median	2.0000	0.1250	0.5000	3.0000	0.0640
Minimum: Maximum (Range)	0.750:32.000	0.012:0.940	0.047:32.000	0.750:16.000	0.016:1.064

Figure 2 Percentage of chloramphenicol-sensitive isolates.